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Sample records for boreal mire ecosystems

  1. Fluxes of methane and nitrogen oxides in various boreal mire ecosystems. Effects of land-use activities and environmental changes

    Energy Technology Data Exchange (ETDEWEB)

    Martikainen, P.J.; Nykaenen, H.; Regina, K. [National Public Health Inst., Kuopio (Finland). Lab. of Environmental Microbiology; Alm, J.; Silvola, J. [Joensuu Univ. (Finland). Dept. of Biology

    1996-12-31

    Atmospheric impact of peatlands is a sum of their gas fluxes. In contrast to carbon dioxide, peatlands are net sources for methane (CH{sub 4}). Methane is an end product in the anaerobic decomposition processes and it has greater capacity to absorb infrared radiation than carbon dioxide. Most of the data on the CH{sub 4} release from northern peatlands is from North America. The total amount of methane released from wetlands is calculated to be 110 Tg yr{sup -1} of which 34 percent (38 Tg yr{sup -1}) is estimated to be emitted from the northern peatlands. Peat with high content of nitrogen is a potential source for gaseous nitrogen oxides, i.e. nitrous oxide (N{sub 2}O) and nitric oxide (NO). However, the importance of peatlands in producing these trace gases is poorly known. Nitrous oxide and nitric oxide are important components in the atmospheric chemistry and N{sub 2}O also is an effective greenhouse gas. Land-use activities and environmental changes can affect the atmospheric impacts of peatlands by modifying their biogeochemistry. This article presents a short summary of the studies whose objectives were: (1) to measure fluxes of CH{sub 4} and N{sub 2}O on wide range of natural mires in Finland, (2) to study the short- and long-term changes in fluxes of CH{sub 4}, N{sub 2}O and NO on boreal peatlands after lowering their water table. Peatlands used for agriculture, forestry and peat mining were included in the studies. The results from mires drained for forestry may reflect the possible changes in the trace gas fluxes if water table will drop in the northern peatlands as a result of drier climate, (3) to study the effects of nitrogen load on the fluxes of CH{sub 4}, N{sub 2}O and NO, (4) to identify the microbiological processes important for the fluxes of N{sub 2}O, NO and CH{sub 4}, and to study the environmental factors regulating these microbial processes

  2. Successional changes in vegetation and carbon dynamics during boreal mire development

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    Leppaelae, M.

    2012-07-01

    Succession is a compositional change of species and other ecosystem characteristics over time. Mire development, i.e., long-term mire succession is basically driven by an increase in peat layer height, promoting changes in hydrology, vegetation and nutrient status of a particular mire. Due to this, ecosystem processes, such as production and loss of carbon due to decomposition (i.e. carbon gas functions), change with increasing successional mire stage. An adequate method for studying the changes in ecosystem C functions is to measure CO{sub 2} and CH{sub 4} fluxes between the ecosystem and atmosphere. Succession and carbon dynamics of boreal pristine mires have been much studied. However the link between these phenomena is largely unknown. Further, if and how the C gas functions of mires change during mire succession it is rather poorly understood. The main objective of this thesis was to study how ecosystem functions, measured as CO{sub 2} and CH{sub 4} exchange, change during mire development. The study also aims to explore the drivers of succession in mire development, i.e., mire succession. Successional mire C dynamics were studied along an eight-kilometer-long successional sequence of primary paludified mires located in the land uplift coast of the Bothnian Bay. Due to the short distance between sites, they all have been under the same climatic control for most of their development. The gradual replacement of plant species with different photosynthetic potential, phenology and assimilating green area resulted in lower-level and temporal variation of CO{sub 2} exchange patterns at the later successional stages. Similar to this, CH{sub 4} also had the lowest interannual variation in the later stages. In general, CH{sub 4} emissions increased with mire age even though this trend did not emerge during the rainy season. Further, this study showed that the wintertime C function pattern was related to the C pattern during the previous summer confirming the important

  3. Contemporary mire net ecosystem green-house gas balance: controls and susceptibility to change

    Science.gov (United States)

    Nilsson, Mats; Eriksson, Tobias; Grelle, Achim; Larsson, Anna; Laudon, Hjalmar; Lindroth, Anders; Ottosson-Löfvenius, Mikaell; Peichl, Matthias; Sagerfors, Jörgen; Ågren, Anneli; Öquist, Mats

    2015-04-01

    In this presentation I will address three main issues: 1 - What is the contemporary carbon sequestration function of high latitude mire ecosystems relative to Holocene average? 2 - The relative importance of the component carbon (C) fluxes for the annual mire Net Ecosystem Carbon Balance (NECB); 3 - The importance of gross primary production (GPP) versus ecosystem respiration (Reco) for the annual Net Ecosystem Exchange (NEE); The annual boreal mire NECB is made up principally by the biosphere-atmosphere exchange of CO2 (NEE) and CH4 and the runoff C-export. One important research issue is to further understand what controls the relative contribution from the component fluxes to the annual mire NECB. A second important major research issue is to reveal the relative importance of gross photosynthesis (GPP) and ecosystem respiration (Reco) respectively for the annual mire NEE. The relative importance of GPP and Reco respectively for the NECB also encounters the effect of changes in the lengths of the growing season and non-growing season respectively. In this presentation we use ten years of data on annual fluxes of NEE, methane and water discharge C export at a nutrient poor minerogenic boreal mire, Degerö Stormyr, in northern Sweden to address the above questions. Winter time NEE together with methane emission and water discharge C export reduces the growing season NEE with approximately 60%, thus substantially controlling the annual boreal mire NEE.

  4. Accumulation of carbon in northern mire ecosystems

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    Tolonen, K.; Turunen, J.; Alm, J. [Joensuu Univ. (Finland). Dept. of Biology; Korhola, A. [Helsinki Univ. (Finland). Lab. of Physical Geography; Jungner, H. [Helsinki Univ. (Finland). Dating Lab.; Vasander, H. [Helsinki Univ. (Finland). Dept. of Forest Ecology

    1996-12-31

    The basic feature in the functional ecology of any mire ecosystem is retardation of the effective decay of organic material resulting in a conspicuous accumulation of plant debris as peat overtime. The carbon accumulation process is slow, and climatic change may have an impact on the carbon cycle of peatlands, therefore, it has been of interest to study the rate of carbon accumulation by geological methods from dated peat strata. The approach is hampered by several facts. First, the mires vary enormously as to their vegetation and hydrology and hence their production and decay properties. It follows that a great number of study sites are needed. Second, the peat in mires expands both vertically and laterally, and this requires a spatial reconstruction of carbon accumulation within a mire basin. Third, simple geological methods cannot account for the actual rate of carbon accumulation in peat, and finally, an additional carbon sink in the mire ecosystems can be the mineral subsoil beneath peat. The proposed warming will perhaps shift northwards the existing climatic mire regimes and, thus, the northern aapa fens will change to Sphagnum bogs that are more effective in sequestering carbon, but distinctly less effective in their CH{sub 4} and N{sub 2}O emanation. The role of mire fires in more remote northern areas may then become another important factor. The answer to the important question of future total sequestration of carbon to peatlands depends on the precipitation and its seasonal distribution pattern. Most climatic scenarios predict a decrease in the evaporation surplus during the summer at northern regions. Presumably, the consequent lowering of the water table would improve growth of forest on mires and simultaneously decrease the methane fluxes from peat. The combined net effect could be a clear restraining of the radiative forcing

  5. Hg0 evasion from boreal mires determined with chamber methods and a novel REA design

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    Osterwalder, Stefan; Fritsche, Johannes; Åkerblom, Staffan; Nilsson, Mats B.; Alewell, Christine; Bishop, Kevin

    2015-04-01

    Anthropogenic mercury has accumulated in superficial organic soils of boreal mires, hotspots of methylmercury production. We hypothesize that emission from the peat surface is an important factor in regulating the pool of mercury in mires and ultimately the loading of methylmercury to surface waters. To test this hypothesis, we used both dynamic flux chambers (DFCs) and a dual-intake, single analyzer Relaxed Eddy Accumulation (REA) system to quantify the land-atmosphere exchange of elemental mercury (Hg0) from a mixed acid mire system situated near Vindeln in the county of Västerbotten, Sweden. Teflon and polycarbonate DFCs were used to (i) investigate the effect of sulfur and nitrogen addition as well as warming and changed moisture regimes on Hg0 flux and (ii) to quantify typical all-day summertime fluxes. The novel REA design was developed for long-term, all-year flux monitoring and uses twin inlets at the same level for simultaneous accumulation of up and downdrafts on a pair of gold traps which are then analyzed sequentially on the same detector while another pair of gold traps takes over the accumulation. The exchange of Hg0 from the peatland surface was measured continuously with DFC during cloudless conditions in July 2014 and averaged 0.62 ± 1.3 ng m-2 h-1. The flux revealed a significant diurnal pattern and a strong linear relationship with air temperature inside (R2= 0.65, p levels in the soil are too long because up to now the emission of Hg from the mire surface to the atmosphere has been ignored.

  6. H2O and CO2 exchange between a sphagnum mire ecosystem and the atmosphere

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    Olchev, Alexander; Volkova, Elena; Karataeva, Tatiana; Novenko, Elena

    2013-04-01

    The modern climatic conditions are strongly influenced by both internal variability of climatic system, and various external natural and anthropogenic factors (IPCC 2007). Significant increase of concentration of greenhouse gases in the atmosphere and especially the growth of atmospheric CO2 due to human activity are considered as the main factors that are responsible for modern global warming and climate changes. A significant part of anthropogenic CO2 is absorbed from the atmosphere by land biota and especially by vegetation cover. However, it is still not completely clear what is the role of different land ecosystems and especially forests and mires in global cycles of H2O and CO2 and what is a sensitivity of these ecosystems to climate changes. Within the framework of this study the spatial and temporal variability of H2O and CO2 fluxes between a mire ecosystem and the atmosphere was described using results of the field measurements and modeling approach. For the study a mire ecosystem located in Tula region in European part of Russia was selected. The selected mire has karst origin, depth of peat float is 2.5-3.0 m (depth of depression is more than 10 meter), area is about 1 ha. The mire vegetation is characterized by sedge and sphagnum mosses cover. The mire is surrounded by broad-leaved forest of about 20 meter high. To describe the temporal and spatial patterns of H2O and CO2 fluxes within selected mire the chamber method was applied. The measurement were carried out along transect from mire edge to center from June to September of 2012. For measurements the transparent ventilated chambers combined with portable infrared CO2/H2O analyzer LI-840 (Li-Cor, USA) was used. To estimate the gross primary production and respiration of different type of vegetation within the mire the measurements were conducted both under actual light conditions and artificial shading. Results of the experimental studies showed that the maximal CO2 fluxes was observed in central

  7. Net ecosystem CO2 exchange and evapotranspiration of a sphagnum mire: field measurements and model simulations

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    Olchev, Alexander; Volkova, Elena; Karataeva, Tatiana; Zatsarinnaya, Dina; Novenko, Elena

    2014-05-01

    The spatial and temporal variability of net ecosystem exchange of CO2 (NEE) and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest-steppe zones in the central part of European Russia (54.06N, 37.59E, 260 m a.s.l.) was described using results of field measurements and simulations with Mixfor-3D model. The area of the mire is about 1.2 ha and it is surrounded by a broadleaved forest stand. It is a typical peat mire according to water and mineral supply as well as to vegetation composition. The vegetation of the peripheral parts of the mire is typical eutrophic whereas the vegetation in its central part is represented by meso-oligothrophic plant communities. To describe the spatial variability of NEE and ET within the mire a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO2 and H2O analyzer LI-840A (Li-Cor, USA) was used. The measurements were provided along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and from May 2013 to October 2013. The chamber method was used for measurements of NEE and ET fluxes because of small size of the mire, a very uniform surrounding forest stand and the mosaic mire vegetation. All these factors promote very heterogeneous exchange conditions within the mire and make it difficult to apply, for example, an eddy covariance method that is widely used for flux measurements in the field. The results of the field measurements showed a significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation, air temperature and ground water level. During the entire growing season the central part of the mire was a sink of CO2 for the atmosphere (up to 6.8±4.2 µmol m-2 s-1 in June) whereas its peripheral part, due to strong shading by the surrounding forest, was mainly a source of

  8. Autochamber measurements of Net Ecosystem (CO2) Exchange at a subarctic mire in Northern Sweden

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    Walthall, M.; Parker-Smith, X.; Lawrence, R. D.; Crill, P. M.

    2015-12-01

    Northern latitude wetlands (>~50°N) are characterized by cold and wet conditions that result in low decomposition rates for plant litter. This process promotes the sequestration of carbon (C) in the form of organic matter (i.e. peat) and the formation of widespread peatands. Peatlands, particularly in the Northern Hemisphere, have accumulated C by removing atmospheric CO2 for approximately the past 10,000 years. Historically, peatlands represent a net C sink; however, increases in the global average temperature could alter peatlands ability to store carbon. With a warming climate and permafrost thaw, the pool of once stable soil organic C available for decomposition is increasing. Like all terrestrial ecosystems, a number of environmental factors (e.g. peat temperature and vegetation) play important roles in governing the fate of C in peatlands. Projected climate change is expected to affect these regulating factors. Subarctic peatlands in zones of discontinuous permafrost are experiencing widespread environmental changes due to climate warming. In this study, we present net ecosystem (CO2) exchange and δ13C-CO2 data from Stordalen Mire in northern Sweden (68°22'N, 19°03'E). Measurements were made using a quantum cascade laser spectrometer connected to automatic chambers placed in the three predominant ecosystems (a dry, elevated Palsa; an intermediate thaw regime dominated by Sphagnum spp. and; a completely thawed, inundated site dominated by Eriophorum angustifolium). Team was mentored by Mr. Ryan Lawrence from The University of New Hampshire.

  9. Dissolved organic carbon dynamics in a near-pristine boreal mire-forest-river landscape during spring snowmelt, Komi Republic, Russia

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    Avagyan, A.; Runkle, B.; Kutzbach, L.

    2011-12-01

    It is well known that peatlands represent an important soil carbon reserve. Therefore, they are considered as hot-spots with respect to climate change. However, lack of information concerning the transport of dissolved organic matter within peatlands and its release into fluvial systems represents a major gap in our understanding of both local and global carbon cycles. In particular, the spring snowmelt period, as a major hydrological event in the annual water cycle of boreal regions, strongly influences the fluxes of carbon between terrestrial and fluvial systems. The aim of this study is to provide thorough quantitative analyses of dissolved organic carbon (DOC) concentrations and fluxes in a boreal mire-forest-river landscape during the snowmelt period. Water samples were collected in the Komi Republic, Russia, in spring 2011 along transects across the near-pristine Ust-Pojeg mire complex and the nearby river Pojeg into which it drains (61°56'N, 50°13'E). This peatland is in a transitional state from fen to bog and consists of minerogeous, ombrogenous, and transitional forest-mire (lagg) zones. Microtopographic features include hummocks, hollows, and lawns. High frequency absorption measurements were conducted directly at the study site with a portable UV-Vis spectrometer over a wavelength range of 200-742.5 nm at 2.5 nm intervals. These results were calibrated against values obtained from the catalytically-aided platinum 680°C combustion technique. The results showed that in the beginning of the snowmelt period only surface carbon is flushed away by melted snow water while deeper layers remain frozen. During this time, DOC concentrations fluctuated within the range of 10-14 mg L-1 across the whole mire complex. During the later stages of snowmelt, concentrations of DOC were different between lagg, fen and bog zones, which separated them into distinct hydrological and biogeochemical units within the mire complex. The highest concentration was observed at the

  10. Ecosystem feedbacks and nitrogen fixation in boreal forests.

    Science.gov (United States)

    DeLuca, Thomas H; Zackrisson, Olle; Gundale, Michael J; Nilsson, Marie-Charlotte

    2008-05-30

    Biological feedback mechanisms regulate fundamental ecosystem processes and potentially regulate ecosystem productivity. To date, no studies have documented the down-regulation of terrestrial nitrogen (N) fixation via an ecosystem-level feedback mechanism. Herein, we demonstrate such a feedback in boreal forests. Rapid cycling of N in early secondary succession forests yielded greater throughfall N deposition, which in turn decreased N fixation by cyanobacterial associates in feather moss carpets that reside on the forest floor. The forest canopy exerts a tight control on biotic N input at a period of high productivity.

  11. Growing season variability of net ecosystem CO2 exchange and evapotranspiration of a sphagnum mire in the broad-leaved forest zone of European Russia

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    Olchev, A.; Volkova, E.; Karataeva, T.; Novenko, E.

    2013-09-01

    The spatial and temporal variability of net ecosystem exchange (NEE) of CO2 and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest-steppe zones in the central part of European Russia in the Tula region was described using results from field measurements. NEE and ET were measured using a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO2/H2O analyzer, LI-840A (Li-Cor, USA) along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and in May 2013. The results of the field measurements showed significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation and ground water level. The seasonal patterns of NEE and ET within the mire were quite different. During the entire growing season the central part of the mire was a sink of CO2 for the atmosphere. NEE reached maximal values in June-July (-6.8 ± 4.2 μmol m-2 s-1). The southern peripheral part of the mire, due to strong shading by the surrounding forest, was a sink of CO2 for the atmosphere in June-July only. ET reached maximal values in the well-lighted central parts of the mire in May (0.34 ± 0.20 mm h-1) mainly because of high air and surface temperatures and the very wet upper peat horizon and sphagnum moss. Herbaceous species made the maximum contribution to the total gross primary production (GPP) in both the central and the peripheral parts of the mire. The contribution of sphagnum to the total GPP of these plant communities was relatively small and ranged on sunny days of July-August from -1.1 ± 1.1 mgC g-1 of dry weight (DW) per hour in the peripheral zone of the mire to -0.6 ± 0.2 mgC g-1 DW h-1 at the mire center. The sphagnum layer made the maximum contribution to total ET at the mire center (0.25 ± 0.10 mm h-1) and the herbaceous

  12. Biodiversity on mire ecosystems and drained peatlands - a basis for environmental peat harvesting; Biologisk maangfald paa myrar och dikad torvmark - underlag foer ett miljoemaessigt torvbruk

    Energy Technology Data Exchange (ETDEWEB)

    Stedingk, Henrik von (Swedish Biodiversity Centre, Uppsala (Sweden))

    2009-07-01

    biodiversity than not drained peatlands. The plant succession following drainage leads to denser vegetation and dominance of forest plants. Often drainage is followed by forestry, leading to even lower nature conservation values. Conservation values on drained peatlands are rarely studied. Potential environments for nature conservation in drained peatlands are: 1) Areas with little drainage influence and preserved mire function. 2) Late forest successions after drainage with deciduous trees and dead wood. 3) Open pine forest or swamp forest that act as refugia for old growth lichens and wood fungi. 4) Pools and stream like older ditches with running water. An inventory focused on conservation values on drained peatlands is recommended. Peat harvesting causes ecosystem shift and species living on the mire disappear. An estimation of biodiversity effects from peat harvesting must include the lost mire, time of exploitation, as well as the after-treatment. A longer time perspective is therefore required when evaluating consequences of peat harvesting. The development of a broader spectra of after-treatment involving biodiversity is essential, as well as a system that guarantees a long term perspective in after-treatment for biodiversity. Methods for evaluating effects on the landscape level from increased peat harvesting are required. Increased peat harvesting on drained peatlands could be in convergence with the Swedish environmental goals, if choice of site and after-treatment is based on landscape analysis focusing on biodiversity

  13. Modeling the effects of organic nitrogen uptake by plants on the carbon cycling of boreal ecosystems

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    Q. Zhu

    2013-08-01

    Full Text Available Boreal forest and tundra are the major ecosystems in the northern high latitudes in which a large amount of carbon is stored. These ecosystems are nitrogen-limited due to slow mineralization rate of the soil organic nitrogen. Recently, abundant field studies have found that organic nitrogen is another important nitrogen supply for boreal ecosystems. In this study, we incorporated a mechanism that allowed boreal plants to uptake small molecular amino acids into a process-based biogeochemical model, the Terrestrial Ecosystem Model (TEM, to evaluate the impact of organic nitrogen uptake on ecosystem carbon cycling. The new version of the model was evaluated at both boreal forest and tundra sites. We found that the modeled organic nitrogen uptake accounted for 36–87% of total nitrogen uptake by plants in tundra ecosystems and 26–50% for boreal forests, suggesting that tundra ecosystem might have more relied on the organic form of nitrogen than boreal forests. The simulated monthly gross ecosystem production (GPP and net ecosystem production (NEP tended to be larger with the new version of the model since the plant uptake of organic nitrogen alleviated the soil nitrogen limitation especially during the growing season. The sensitivity study indicated that the most important factors controlling the plant uptake of organic nitrogen were the maximum root uptake rate (Imax and the radius of the root (r0 in our model. The model uncertainty due to uncertain parameters associated with organic nitrogen uptake at tundra ecosystem was larger than at boreal forest ecosystems. This study suggests that considering the organic nitrogen uptake by plants is important to boreal ecosystem carbon modeling.

  14. Towards a comprehensive emission inventory of terpenoids from boreal ecosystems

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    Tarvainen, V.; Hakola, H.; Rinne, J.; Hellén, H.; Haapanala, S.

    2007-07-01

    The biogenic volatile organic compound emissions in the south boreal, middle boreal and north boreal vegetation zones in Finland were calculated utilizing satellite land cover information and actual meteorological data in a BEIS-type canopy emission model. The sesquiterpene emissions from the boreal forest were estimated for the first time, and the inventory was further complemented by the inclusion of wetland isoprene emissions from open fens. Recently published results from emission measurements carried out in various parts of the boreal region were utilized in the compilation of the standard emission potentials and monoterpene emission spectra for the deciduous and coniferous forest categories and wetlands. The average annual isoprene emission fluxes from forests were 73, 56 and 45, and those of monoterpenes 657, 567 and 342 kg per km2 of forest area in the south boreal, middle boreal and north boreal vegetation zones, respectively. The average annual sesquiterpene fluxes were of the same order of magnitude as isoprene, being 54, 46 and 26 kg per km2 of forest area in the south boreal, middle boreal and north boreal vegetation zones, respectively. The isoprene emissions from wetlands were significant, contributing 3%, 18% and 31% of the annual isoprene emissions in the south boreal, middle boreal and north boreal vegetation zones, respectively. Throughout the boreal region, the main emitted monoterpenes were α-pinene and Δ3-carene, with significant contributions from β-pinene and sabinene in summer and autumn. Due to the new seasonal emission potentials of the coniferous species introduced in this work, the overwhelming role of spruce as the main isoprene and monoterpene emitter in the boreal forest is subdued. The new emission inventory also accentuates the role of the boreal deciduous trees as terpenoid emitters in the late summer months.

  15. Distribution and transport of radionuclides in a boreal mire--assessing past, present and future accumulation of uranium, thorium and radium.

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    Lidman, Fredrik; Ramebäck, Henrik; Bengtsson, Åsa; Laudon, Hjalmar

    2013-07-01

    The spatial distribution of (238)U, (226)Ra, (40)K and the daughters of (232)Th, (228)Ra and (228)Th, were measured in a small mire in northern Sweden. High activity concentrations of (238)U and (232)Th (up to 41 Bq (238)U kg(-1)) were observed in parts of the mire with a historical or current inflow of groundwater from the surrounding till soils, but the activities declined rapidly further out in the mire. Near the outlet and in the central parts of the mire the activity concentrations were low, indicating that uranium and thorium are immobilized rapidly upon their entering the peat. The (226)Ra was found to be more mobile with high activity concentrations further out into the mire (up to 24 Bq kg(-1)), although the central parts and the area near the outlet of the mire still had low activity concentrations. Based on the fluxes to and from the mire, it was estimated that approximately 60-70% of the uranium and thorium entering the mire currently is retained within it. The current accumulation rates were found to be consistent with the historical accumulation, but possibly lower. Since much of the accumulation still is concentrated to the edges of the mire and the activities are low compared to other measurements of these radionuclides in peat, there are no indications that the mire will be saturated with respect to radionuclides like uranium, thorium and radium in the foreseen future. On the contrary, normal peat growth rates for the region suggest that the average activity concentrations of the peat currently may be decreasing, since peat growth may be faster than the accumulation of radionuclides. In order to assess the total potential for accumulation of radionuclides more thoroughly it would, however, be necessary to also investigate the behaviour of other organophilic elements like aluminium, which are likely to compete for binding sites on the organic material. Measurements of the redox potential and other redox indicators demonstrate that uranium possibly

  16. Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

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    Thomas A. Douglas

    2014-12-01

    Full Text Available Abstract Boreal ecosystems store large quantities of carbon but are increasingly vulnerable to carbon loss due to disturbance and climate warming. The boreal region in Alaska and Canada, largely underlain by discontinuous permafrost, presents a challenging landscape for itemizing carbon sources and sinks in soil and vegetation. The roles of fire, forest succession, and the presence (or absence of permafrost on carbon cycle, vegetation, and hydrologic processes have been the focus of multidisciplinary research in boreal ecosystems for the past 20 years. However, projections of a warming future climate, an increase in fire severity and extent, and the potential degradation of permafrost could lead to major landscape and carbon cycle changes over the next 20 to 50 years. To assist land managers in interior Alaska in adapting and managing for potential changes in the carbon cycle we developed this review paper by incorporating an overview of the climate, ecosystem processes, vegetation, and soil regimes. Our objective is to provide a synthesis of the most current carbon storage estimates and measurements to guide policy and land management decisions on how to best manage carbon sources and sinks. We surveyed estimates of aboveground and belowground carbon stocks for interior Alaska boreal ecosystems and summarized methane and carbon dioxide fluxes. These data have been converted into similar units to facilitate comparison across ecosystem compartments. We identify potential changes in the carbon cycle with climate change and human disturbance. A novel research question is how compounding disturbances affect carbon sources and sinks associated with boreal ecosystem processes. Finally, we provide recommendations to address the challenges facing land managers in efforts to manage carbon cycle processes. The results of this study can be used for carbon cycle management in other locations within the boreal biome which encompasses a broad distribution

  17. Recent changes in vegetation, hydrotopography and peat accumulation in detailed case studies of northern aapa mires

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    Tahvanainen, Teemu; Kumpula, Timo; Tolonen, Kimmo

    2016-04-01

    , pools), 155 peat depth measurements and 38 vegetation plots. Despite the pristine wilderness character of the site, we found increased tree encroachment, significant increase of height of Sphagnum hummocks, lateral expansion of ombrotrophic bog zone over fen vegetation and increase of dwarf-shrubs typical to raised bog vegetation. Peat thickness in the bog zone had increased by 2.2 mm per year, greatly exceeding the long-term average of bogs in the region. Our case studies demonstrate a remarkable potential of ecosystem-scale responses in northern aapa mires, ecotone mire type between temperate-south boreal bogs and subarctic palsa mires. Hydrological disturbances can rapidly trigger an allogenic mechanism of fen to bog transition. Traces of ongoing changes in aapa mires can be apparent also in seemingly pristine sites when accurate repeated measurements are performed. Although the observed changes may threaten aapa mire habitat types and biota, they are progressive in terms of peat growth and carbon dioxide sequestration.

  18. Modelling atmospheric OH-reactivity in a boreal forest ecosystem

    DEFF Research Database (Denmark)

    Mogensen, D.; Smolander, S.; Sogachev, Andrey;

    2011-01-01

    We have modelled the total atmospheric OH-reactivity in a boreal forest and investigated the individual contributions from gas phase inorganic species, isoprene, monoterpenes, and methane along with other important VOCs. Daily and seasonal variation in OH-reactivity for the year 2008 was examined...

  19. Mires and mire types of Peninsula Mitre, Tierra del Fuego, Argentina

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    A. Grootjans

    2014-01-01

    Full Text Available In 2007, a field visit by members of the International Mire Conservation Group (IMCG to the Atlantic coast of Peninsula Mitre (the easternmost part of Isla Grande de Tierra del Fuego, Argentina gathered information on mire diversity in this remote wild area with largely pristine mires. Our expedition showed that Peninsula Mitre hosts a wide variety of habitats across two exciting ecological gradients: (i a regional west–east gradient from Sphagnum magellanicum dominated mires in the west to Astelia pumila dominated mires in the east; and (ii a gradient from extremely acid to extremely carbonate rich mire types induced by local bedrock. The large variety of hydromorphological mire types comprises raised bogs, blanket bogs, sloping fens, string fens, flat fens and calcareous spring fens. In the Atlantic coastal area, the abundance of Sphagnum magellanicum in the ombrogenic systems decreases conspicuously from west to east with the species being almost absent in the east. However, the fossil record shows thick layers of Sphagnum peat close beneath mire surfaces everywhere, indicating that substantial hydrological and ecological changes have taken place in the recent past. We observed large scale erosion in the mires along the Atlantic coast. Locally, well-developed fen systems are present, including calcareous spring fens with active travertine (tufa deposition. The regional vegetation can be regarded as a parallel to that of boreal oceanic regions in the northern hemisphere. The mires and peatlands of the peninsula are of global significance. They are impressive, peculiar, extensive and largely pristine mires in a globally very rare climatic and biogeographical context embedded in a landscape with significant natural dynamics. The damaging impact of free-roaming cattle on the mires and upland vegetation is, however, conspicuous and needs urgent attention. Peninsula Mitre deserves the highest possible protection, e.g. as a provincial protected

  20. Nitrogen Additions Affect Root Dynamics in a Boreal Forest Ecosystem

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    Turner, K. M.; Treseder, K. K.

    2004-12-01

    As with many ecosystems, North American boreal forests are increasingly subjected to anthropogenic nitrogen deposition. To examine potential effects on plant growth, we created nitrogen fertilization plots in three sites along an Alaskan fire chronosequence composed of forests aged 5, 17, and 80 years. Each site had been exposed to two years of nitrogen fertilization, with four control plots and four nitrogen plots per site. General observations indicate that aboveground net primary productivity appears to be nitrogen limited in each site. We hypothesized that nitrogen fertilization would positively influence root dynamics as well, with nitrogen additions resulting in an increase in standing root biomass and length. To test our hypothesis, we used a minirhizotron camera to collect sequential images of roots in the top 10 cm of soil in both nitrogen fertilized and control plots in each site. Images were collected monthly during the growing season, with a total of five sampling times between May 2003 and May 2004. We then analyzed the images with WinRhizotron root measurement software. Nitrogen fertilization had varying effects on root biomass among the three sites, with a significant site by N interaction (P = 0.039). A decrease in root biomass was observed in the 5 and 80 year old sites, dropping from 207 g/m2 to 79 g/m2 and from 230 g/m2 to 129 g/m2 for the youngest and oldest sites, respectively. In contrast, root biomass increased from 52 g/m2 to 107 g/m2 in the 17 year old site. (Values are for the top 10 cm of soil only, and likely underestimate total root stocks.) Patterns in standing root lengths diverged from those of root biomass, with a 2.5-fold overall increase under nitrogen fertilization across all sites (P = 0.004). There were no significant differences among sites in nitrogen response. Standing root biomass and length differed from one another in their responses to nitrogen fertilization because nitrogen additions decreased specific root weight (as g

  1. Impacts of elevated carbon dioxide and temperature on a boreal forest ecosystem (CLIMEX project).

    NARCIS (Netherlands)

    Breemen, van N.; Jenkins, A.; Wright, R.F.; Beerling, D.J.; Arp, W.J.; Berendse, F.; Beier, C.; Collins, R.; Dam, van D.; Rasmussen, L.; Verburg, P.S.J.; Wills, M.A.

    1998-01-01

    To evaluate the effects of climate change on boreal forest ecosystems, both atmospheric CO2 (to 560 ppmv) and air temperature (by 3°–5°C above ambient) were increased at a forested headwater catchment in southern Norway. The entire catchment (860 m2) is enclosed within a transparent greenhouse, and

  2. Does Drought Influence the Relationship between Species diversity and Ecosystem Functioning in Boreal Forests?

    OpenAIRE

    2014-01-01

    Dans le programme la présentation annoncée est "How do Environmental Conditions Influence the Biodiversity-Ecosystem Functioning Relationship in Boreal Forests?"; Ecosystem functioning is influenced by species composition and environmental conditions. Positive biodiversity effects on forest stand-level water use efficiency (WUES) have been observed under limiting soil water conditions, but whether such a relationship would explain WUEs patterns under non-limiting conditions remains to be addr...

  3. Vulnerability to climate-induced changes in ecosystem services of boreal forests

    Science.gov (United States)

    Holmberg, Maria; Rankinen, Katri; Aalto, Tuula; Akujärvi, Anu; Nadir Arslan, Ali; Liski, Jari; Markkanen, Tiina; Mäkelä, Annikki; Peltoniemi, Mikko

    2016-04-01

    Boreal forests provide an array of ecosystem services. They regulate climate, and carbon, water and nutrient fluxes, and provide renewable raw material, food, and recreational possibilities. Rapid climate warming is projected for the boreal zone, and has already been observed in Finland, which sets these services at risk. MONIMET (LIFE12 ENV/FI/000409, 2.9.2013 - 1.9.2017) is a project funded by EU Life programme about Climate Change Indicators and Vulnerability of Boreal Zone Applying Innovative Observation and Modeling Techniques. The coordinating beneficiary of the project is the Finnish Meteorological Institute. Associated beneficiaries are the Natural Resources Institute Finland, the Finnish Environment Institute and the University of Helsinki. In the MONIMET project, we use state-of-the-art models and new monitoring methods to investigate the impacts of a warming climate on the provision of ecosystem services of boreal forests. This poster presents results on carbon storage in soil and assessment of drought indices, as a preparation for assessing the vulnerability of society to climate-induced changes in ecosystem services. The risk of decreasing provision of ecosystem services depends on the sensitivity of the ecosystem as well as its exposure to climate stress. The vulnerability of society, in turn, depends on the risk of decreasing provision of a certain service in combination with society's demand for that service. In the next phase, we will look for solutions to challenges relating to the quantification of the demand for ecosystem services and differences in spatial extent and resolution of the information on future supply and demand.

  4. Modelling atmospheric OH-reactivity in a boreal forest ecosystem

    DEFF Research Database (Denmark)

    Mogensen, D.; Smolander, S.; Sogachev, Andrey;

    2011-01-01

    We have modelled the total atmospheric OH-reactivity in a boreal forest and investigated the individual contributions from gas phase inorganic species, isoprene, monoterpenes, and methane along with other important VOCs. Daily and seasonal variation in OH-reactivity for the year 2008 was examined...... as well as the vertical OH-reactivity profile. We have used SOSA; a one dimensional vertical chemistry-transport model (Boy et al., 2011a) together with measurements from Hyytiala, SMEAR II station, Southern Finland, conducted in August 2008. Model simulations only account for similar to 30......-50% of the total measured OH sink, and in our opinion, the reason for missing OH-reactivity is due to unmeasured unknown BVOCs, and limitations in our knowledge of atmospheric chemistry including uncertainties in rate constants. Furthermore, we found that the OH-reactivity correlates with both organic...

  5. The climate responses of tropical and boreal ecosystems with an improved land surface model (JULES)

    Science.gov (United States)

    Harper, Anna; Friedlingstein, Pierre; Cox, Peter; Wiltshire, Andy; Jones, Chris

    2016-04-01

    The Joint UK Land Environment Simulator (JULES) is the land surface of the next generation UK Earth System Model (UKESM1). Recently, JULES was updated with new plant functional types and physiology based on a global plant trait database. These developments improved the simulation of terrestrial gross and net primary productivity on local and global scales, and enabled a more realistic representation of the global distribution of vegetation. In this study, we explore the present-day distribution of ecosystems and their vulnerability to climate change in JULES with these improvements, focusing on tropical and boreal ecosystems. Changes to these ecosystems will have implications for biogeophysical and biogeochemical feedbacks to climate change and need to be understood. First, we examine the simulated and observed rainforest-savannah boundary, which is strongly related to annual precipitation and the maximum climatological water deficit. Second, we assess the length of growing season and biomass stored in boreal ecosystems, where 20th century warming has likely extended the growing season. In each case, we first evaluate the ability of JULES to capture observed climate-vegetation relationships and trends. Finally, we run JULES to 2100 using climate data from 3 models and 2 RCP scenarios, and examine potential 21st century changes to these ecosystems. For example, do the tropical forests shrink in response to changes in tropical rainfall seasonality? And, how does the composition of boreal ecosystems change in response to climate warming? Given the potential for climate feedbacks and the inherent value in these ecosystems, it is essential to assess their responses to a range of climate change scenarios.

  6. Moss-cyanobacteria associations as biogenic sources of nitrogen in boreal forest ecosystems

    OpenAIRE

    Kathrin eRousk; Jones, Davey L; Thomas H Deluca

    2013-01-01

    The biological fixation of atmospheric nitrogen (N) is a major pathway for available N entering ecosystems. In N-limited boreal forests, a significant amount of N2 is fixed by cyanobacteria living in association with mosses, contributing up to 50% to the total N input. In this review, we synthesize reports on the drivers of N2 fixation in feather moss-cyanobacteria associations to gain a deeper understanding of their role for ecosystem-N-cycling. Nitrogen fixation in moss-cyanobacteria associ...

  7. Arctic and boreal ecosystems of western North America as components of the climate system

    Science.gov (United States)

    Chapin, F. S.; McGuire, A.D.; Randerson, J.; Pielke, R.; Baldocchi, D.; Hobbie, S.E.; Roulet, Nigel; Eugster, W.; Kasischke, E.; Rastetter, E.B.; Zimov, S.A.; Running, S.W.

    2000-01-01

    Synthesis of results from several Arctic and boreal research programmes provides evidence for the strong role of high-latitude ecosystems in the climate system. Average surface air temperature has increased 0.3??C per decade during the twentieth century in the western North American Arctic and boreal forest zones. Precipitation has also increased, but changes in soil moisture are uncertain. Disturbance rates have increased in the boreal forest; for example, there has been a doubling of the area burned in North America in the past 20 years. The disturbance regime in tundra may not have changed. Tundra has a 3-6-fold higher winter albedo than boreal forest, but summer albedo and energy partitioning differ more strongly among ecosystems within either tundra or boreal forest than between these two biomes. This indicates a need to improve our understanding of vegetation dynamics within, as well as between, biomes. If regional surface warming were to continue, changes in albedo and energy absorption would likely act as a positive feedback to regional warming due to earlier melting of snow and, over the long term, the northward movement of treeline. Surface drying and a change in dominance from mosses to vascular plants would also enhance sensible heat flux and regional warming in tundra. In the boreal forest of western North America, deciduous forests have twice the albedo of conifer forests in both winter and summer, 50-80% higher evapotranspiration, and therefore only 30-50% of the sensible heat flux of conifers in summer. Therefore, a warming-induced increase in fire frequency that increased the proportion of deciduous forests in the landscape, would act as a negative feedback to regional warming. Changes in thermokarst and the aerial extent of wetlands, lakes, and ponds would alter high-latitude methane flux. There is currently a wide discrepancy among estimates of the size and direction of CO2 flux between high-latitude ecosystems and the atmosphere. These

  8. Climatic sensitivity of hydrology and carbon exchanges in boreal peatland ecosystems, with implications on sustainable management of reed canary grass (Phalaris arundinacea, L.) on cutaway peatlands

    Energy Technology Data Exchange (ETDEWEB)

    Gong Jinnan

    2013-11-01

    The aim of the study was to investigate the effects of climate change on soil hydrology and carbon (C) fluxes in boreal peatland ecosystems, with implications for the feasibility of cultivating reed canary grass (Phalaris arundinacea, L; RCG) as a way to restore the C sink in cutaway peatlands under Finnish conditions. First, hydrological models were developed for pristine peatland ecosystems and the cutaway peatlands under RCG cultivation. Concurrently, the hydrological responses to varying climatic forcing and mire types were investigated for these ecosystems. Thereafter, process-based models for estimating the seasonal and annual C exchanges were developed for the pristine mires and cutaway peatlands. The C models incorporated the hydrological models for corresponding ecosystems. Model simulations based on the climate scenarios (ACCLIM, developed by the Finnish Meteorological Institute, FMI) were further carried out to study the impacts of climate change on the C exchanges in the peatland ecosystems during the 21st century. The simulation showed that the water table (WT) in the pristine Finnish mires would draw down slightly during the 21st century. Such a chance in WT would be related to a decrease in the CO{sub 2} sink but an increase in the CH{sub 4} source at the country scale, as driven mainly by the rising temperature (Ta) and increasing precipitation (P). These changes in CO{sub 2}/ CH{sub 4} fluxes would decrease the total C-greenhouse gas (GHG) sink (CO{sub 2} equilibrium) by 68% at the country scale, and the changes would be more pronounced toward the end of the century. The majority of pristine fens in southern and western Finland and the pristine bogs near the coastal areas would become centurial CO{sub 2} sources under the changing climate. On the other hand, the major distribution of fens in northern Finland would act to increase the CH{sub 4} source at the country scale, whereas the CH{sub 4} emission would tend to decrease with WT in the southern

  9. Functional Diversity of Boreal Bog Plant Species Decreases Seasonal Variation of Ecosystem Carbon Sink Function

    Science.gov (United States)

    Korrensalo, A.

    2015-12-01

    Species diversity has been found to decrease the temporal variance of productivity of a plant community, and diversity in species responses to environmental factors seems to make a plant community more stable in changing conditions. Boreal bogs are nutrient poor peatland ecosystems where the number of plant species is low but the species differ greatly in their growth form. In here we aim to assess the role of the variation in photosynthesis between species for the temporal variation in ecosystem carbon sink function. To quantify the photosynthetic properties and their seasonal variation for different bog plant species we measured photosynthetic parameters and stress-inducing chlorophyll fluorescence of vascular plant and Sphagnum moss species in a boreal bog over a growing season. We estimated monthly gross photosynthesis (PG) of the whole study site based on species level light response curves and leaf area development. The estimated PG was further compared with a gross primary production (GPP) estimate measured by eddy covariance (EC) technique. The sum of upscaled PG estimates agreed well with the GPP estimate measured by the EC technique. The contributions of the species and species groups to the ecosystem level PG changed over the growing season. The sharp mid-summer peak in sedge PG was balanced by more stable PG of evergreen shrubs and Sphagna. Species abundance rather than differences in photosynthetic properties between species and growth forms determined the most productive plants on the ecosystem scale. Sphagna had lower photosynthesis and clorophyll fluorescence than vascular plants but were more productive on the ecosystem scale throughout the growing season due to their high areal coverage. These results show that the diversity of growth forms stabilizes the seasonal variation of the ecosystem level PG in an ombrotrophic bog ecosystem. This may increase the resilience of the ecosystem to changing environmental conditions.

  10. Declining plant nitrogen supply and carbon accumulation in ageing primary boreal forest ecosystems

    Science.gov (United States)

    Högberg, Mona N.; Yarwood, Stephanie A.; Trumbore, Susan; Högberg, Peter

    2016-04-01

    Boreal forest soils are commonly characterized by a low plant nitrogen (N) supply. A high tree below-ground allocation of carbon (C) to roots and soil microorganisms in response to the shortage of N may lead to high microbial immobilisation of N, thus aggravating the N limitation. We studied the N supply at a Swedish boreal forest ecosystem chronosequence created by new land rising out of the sea due to iso-static rebound. The youngest soils develop with meadows by the coast, followed by a zone of dinitrogen fixing alder trees, and primary boreal conifer forest on ground up to 560 years old. With increasing ecosystem age, the proportion of microbial C out of the total soil C pool from the youngest to the oldest coniferous ecosystem was constant (c. 1-1.5%), whereas immobilised N (microbial N out of total soil N) increased and approached the levels commonly observed in similar boreal coniferous forests (c. 6-7 %), whereas gross N mineralization declined. Simultaneously, plant foliar N % decreased and the natural abundance of N-15 in the soil increased. More specifically, the difference in N-15 between plant foliage and soil increased, which is related to greater retention of N-15 relative to N-14 by ectomycorrhizal fungi as N is taken up from the soil and some N is transferred to the plant host. In the conifer forest, where these changes were greatest, we found increased fungal biomass in the F- and H-horizons of the mor-layer, in which ectomycorrhizal fungi are known to dominate (the uppermost horizon with litter and moss is dominated by saprotrophic fungi). Hence, we propose that the decreasing N supply to the plants and the subsequent decline in plant production in ageing boreal forests is linked to high tree belowground C allocation to C limited ectomycorrhizal fungi (and other soil microorganisms), a strong sink for available soil N. Data on organic matter C-14 suggested that the largest input of recently fixed plant C occurred in the younger coniferous forest

  11. Modeled Climate and Disturbance Impacts to Carbon Sequestration of Recent Interior Boreal Alaska Ecosystem Productivity Declines

    Science.gov (United States)

    Neigh, C. S.; Carvalhais, N.; Collatz, G. J.; Tucker, C. J.

    2010-12-01

    Terrestrial Higher Northern Latitude Boreal ecosystems over the past half century have and are expected to incur substantial future climate warming altering long-term biophysical processes that mediate carbon sink status. Boreal ecosystems are one of the primary terrestrial pools with high organic and mineral soil carbon concentrations due to reduced decomposition from extended periods below freezing. Direct impacts of changing local to regional climate have altered Interior Alaska disturbance regimes shifting patterns of net primary production (NPP), soil heterotrophic respiration (Rh), net ecosystem production (NEP = NPP - Rh) and net biome production (NBP = NEP - De) which includes disturbance events (De). We investigated ecosystem dynamics with a satellite remote sensing driven model accounting for fine-scale heterogeneous events observed from multi temporal-spectral index vectors derived from Landsat. Our intent was to elucidate local to regional processes which have resulted in negative trends observed from the NOAA series of Advanced Very High Resolution Radiometers (AVHRR) over the past decade. The Carnegie-Ames-Stanford approach (CASA) model was run with changing fractional burned area to simulate bi-monthly patterns of net plant carbon fixation, biomass and nutrient allocation, litterfall, soil nitrogen mineralization, combustion emissions, and microbial CO2 production. Carbon reallocation was based on fire disturbances identified with remote sensing data (Landsat, IKONOS, and aerial photography) and disturbance perimeter maps from land management agencies. Warming coupled with insect and fire disturbance emissions reduced interior Boreal forest recalcitrant carbon pools for which losses greatly exceed the North Slope Tundra sink. Our multi spatial-temporal approach confirms substantial forested NPP declines in Landsat and AVHRR while distinguishing abiotic and biophysical disturbance frequency impacts upon NBP.

  12. Photosynthetic properties of boreal bog plant species and their contribution to ecosystem level carbon sink

    Science.gov (United States)

    Korrensalo, Aino; Hájek, Tomas; Alekseychik, Pavel; Rinne, Janne; Vesala, Timo; Mehtätalo, Lauri; Mammarella, Ivan; Tuittila, Eeva-Stiina

    2016-04-01

    Boreal bogs have a low number of plant species, but a large diversity of growth forms. This heterogeneity might explain the seasonally less varying photosynthetic productivity of these ecosystems compared to peatlands with vegetation consisting of fewer growth forms. The differences in photosynthetic properties within bog species and phases of growing season has not been comprehensively studied. Also the role of different plant species for the ecosystem level carbon (C) sink function is insufficiently known. We quantified the seasonal variation of photosynthetic properties in bog plant species and assessed how this variation accounts for the temporal variation in the ecosystem C sink. Photosynthetic light response of 11 vascular plant and 8 Sphagnum moss species was measured monthly over the growing season of 2013. Based on the species' light response parameters, leaf area development and areal coverage, we estimated the ecosystem level gross photosynthesis rate (PG) over the growing season. The level of upscaled PG was verified by comparing it to the ecosystem gross primary production (GPP) estimate calculated based on eddy covariance (EC) measurements. Although photosynthetic parameters differed within plant species and months, these differences were of less importance than expected for the variation in ecosystem level C sink. The most productive plant species at the ecosystem scale were not those with the highest maximum potential photosynthesis per unit of leaf area (Pmax), but those having the largest areal coverage. Sphagnum mosses had 35% smaller Pmax than vascular plants, but had higher photosynthesis at the ecosystem scale throughout the growing season. The contribution of the bog plant species to the ecosystem level PG differed over the growing season. The seasonal variation in ecosystem C sink was mainly controlled by phenology. Sedge PG had a sharp mid-summer peak, but the PG of evergreen shrubs and Sphagna remained rather stable over the growing season

  13. Comparing soil biogeochemical processes in novel and natural boreal forest ecosystems

    Science.gov (United States)

    Quideau, S. A.; Swallow, M. J. B.; Prescott, C. E.; Grayston, S. J.; Oh, S.-W.

    2013-08-01

    Emulating the variability that exists in the natural landscape prior to disturbance should be a goal of soil reconstruction and land reclamation efforts following resource extraction. Long-term ecosystem sustainability within reclaimed landscapes can only be achieved with the re-establishment of biogeochemical processes between reconstructed soils and plants. In this study, we assessed key soil biogeochemical attributes (nutrient availability, organic matter composition, and microbial communities) in reconstructed, novel, anthropogenic ecosystems, covering different reclamation treatments following open-cast mining for oil extraction. We compared the attributes to those present in a range of natural soils representative of mature boreal forest ecosystems in the same area of Northern Alberta. Soil nutrient availability was determined in situ with resin probes, organic matter composition was described with 13C nuclear magnetic resonance spectroscopy and soil microbial community structure was characterized using phospholipid fatty acid analysis. Significant differences among natural ecosystems were apparent in nutrient availability and seemed more related to the dominant tree cover than to soil type. When analyzed together, all natural forests differed significantly from the novel ecosystems, in particular with respect to soil organic matter composition. However, there was some overlap between the reconstructed soils and some of the natural ecosystems in nutrient availability and microbial communities, but not in organic matter characteristics. Hence, our results illustrate the importance of considering the range of natural landscape variability and including several soil biogeochemical attributes when comparing novel, anthropogenic ecosystems to the mature ecosystems that constitute ecological targets.

  14. Comparing soil biogeochemical processes in novel and natural boreal forest ecosystems

    Directory of Open Access Journals (Sweden)

    S. A. Quideau

    2013-08-01

    Full Text Available Emulating the variability that exists in the natural landscape prior to disturbance should be a goal of soil reconstruction and land reclamation efforts following resource extraction. Long-term ecosystem sustainability within reclaimed landscapes can only be achieved with the re-establishment of biogeochemical processes between reconstructed soils and plants. In this study, we assessed key soil biogeochemical attributes (nutrient availability, organic matter composition, and microbial communities in reconstructed, novel, anthropogenic ecosystems, covering different reclamation treatments following open-cast mining for oil extraction. We compared the attributes to those present in a range of natural soils representative of mature boreal forest ecosystems in the same area of Northern Alberta. Soil nutrient availability was determined in situ with resin probes, organic matter composition was described with 13C nuclear magnetic resonance spectroscopy and soil microbial community structure was characterized using phospholipid fatty acid analysis. Significant differences among natural ecosystems were apparent in nutrient availability and seemed more related to the dominant tree cover than to soil type. When analyzed together, all natural forests differed significantly from the novel ecosystems, in particular with respect to soil organic matter composition. However, there was some overlap between the reconstructed soils and some of the natural ecosystems in nutrient availability and microbial communities, but not in organic matter characteristics. Hence, our results illustrate the importance of considering the range of natural landscape variability and including several soil biogeochemical attributes when comparing novel, anthropogenic ecosystems to the mature ecosystems that constitute ecological targets.

  15. Comparing soil biogeochemical processes in novel and natural boreal forest ecosystems

    Directory of Open Access Journals (Sweden)

    S. A. Quideau

    2013-04-01

    Full Text Available Emulating the variability that exists in the natural landscape prior to disturbance should be a goal of soil reconstruction and land reclamation efforts following resource extraction. Long-term ecosystem sustainability within reclaimed landscapes can only be achieved with the re-establishment of biogeochemical processes between reconstructed soils and plants. In this study, we assessed key soil biogeochemical attributes (nutrient availability, organic matter composition, and microbial communities in reconstructed, novel, anthropogenic ecosystems covering different reclamation treatments following open-cast mining for oil extraction. We compared the attributes to those present in a range of natural soils representative of mature boreal forest ecosystems in the same area of northern Alberta. Soil nutrient availability was determined in situ with resin probes, organic matter composition was described with 13C nuclear magnetic resonance spectroscopy and soil microbial community structure was characterized using phospholipid fatty acid analysis. Significant differences among natural ecosystems were apparent in nutrient availability and seemed more related to the dominant tree cover than to soil type. When analyzed together, all natural forests differed significantly from the novel ecosystems, in particular with respect to soil organic matter composition. However, there was some overlap between the reconstructed soils and some of the natural ecosystems in nutrient availability and microbial communities, but not in organic matter characteristics. Hence, our results illustrate the importance of considering the range of natural landscape variability, and including several soil biogeochemical attributes when comparing novel, anthropogenic ecosystems to the mature ecosystems that constitute ecological targets.

  16. Understanding the long term ecosystem stability of a fen mire by analyzing subsurface geology, eco-hydrology and nutrient stoichiometry - Case study of the Rospuda valley (NE Poland)

    NARCIS (Netherlands)

    Jabłońska, Ewa; Falkowski, Tomasz; Chormański, Jarosław; Jarzombkowski, Filip; Kłosowski, Stanisław; Okruszko, Tomasz; Pawlikowski, Paweł; Theuerkauf, Martin; Wassen, Martin J.; Kotowski, Wiktor

    2014-01-01

    We explored the background of differences in long-term stability between two parts in an undisturbed mire system (Rospuda fen, NE Poland). We re-constructed the Holocene history of the mire and compared it with current vegetation, water level dynamics, water chemistry and nutrient availability in tw

  17. Challenges in Modeling Disturbance Regimes and Their Impacts in Arctic and Boreal Ecosystems (Invited)

    Science.gov (United States)

    McGuire, A. D.; Rupp, T. S.; Kurz, W.

    2013-12-01

    Disturbances in arctic and boreal terrestrial ecosystems influence services provided by these ecosystems to society. In particular, changes in disturbance regimes in northern latitudes have uncertain consequences for the climate system. A major challenge for the scientific community is to develop the capability to predict how the frequency, severity and resultant impacts of disturbance regimes will change in response to future changes in climate projected for northern high latitudes. Here we compare what is known about drivers and impacts of wildfire, phytophagous insect pests, and thermokarst disturbance to illustrate the complexities in predicting future changes in disturbance regimes and their impacts in arctic and boreal regions. Much of the research on predicting fire has relied on the use of drivers related to fire weather. However, changes in vegetation, such as increases in broadleaf species, associated with intensified fire regimes have the potential to influence future fire regimes through negative feedbacks associated with reduced flammability. Phytophagous insect outbreaks have affected substantial portions of the boreal region in the past, but frequently the range of the tree host is larger than the range of the insect. There is evidence that a number of insect species are expanding their range in response to climate change. Major challenges to predicting outbreaks of phytophagous insects include modeling the effects of climate change on insect growth and maturation, winter mortality, plant host health, the synchrony of insect life stages and plant host phenology, and changes in the ranges of insect pests. Moreover, Earth System Models often simplify the representation of vegetation characteristics, e.g. the use of plant functional types, providing insufficient detail to link to insect population models. Thermokarst disturbance occurs when the thawing of ice-rich permafrost results in substantial ground subsidence. In the boreal forest, thermokarst can

  18. Multi-trophic resilience of boreal lake ecosystems to forest fires.

    Science.gov (United States)

    Lewis, Tyler L; Lindberg, Mark S; Schmutz, Joel A; Bertram, Mark R

    2014-05-01

    Fires are the major natural disturbance in the boreal forest, and their frequency and intensity will likely increase as the climate warms. Terrestrial nutrients released by fires may be transported to boreal lakes, stimulating increased primary productivity, which may radiate through multiple trophic levels. Using a before-after-control-impact (BACI) design, with pre- and postfire data from burned and unburned areas, we examined effects of a natural fire across several trophic levels of boreal lakes, from nutrient and chlorophyll levels, to macroinvertebrates, to waterbirds. Concentrations of total nitrogen and phosphorus were not affected by the fire. Chlorophyll a levels were also unaffected, likely reflecting the stable nutrient concentrations. For aquatic invertebrates, we found that densities of three functional feeding groups did not respond to the fire (filterers, gatherers, scrapers), while two groups increased (shredders, predators). Amphipods accounted for 98% of shredder numbers, and we hypothesize that fire-mediated habitat changes may have favored their generalist feeding and habitat ecology. This increase in amphipods may, in turn, have driven increased predator densities, as amphipods were the most numerous invertebrate in our lakes and are commonly taken as prey. Finally, abundance of waterbird young, which feed primarily on aquatic invertebrates, was not affected by the fire. Overall, ecosystems of our study lakes were largely resilient to forest fires, likely due to their high initial nutrient concentrations and small catchment sizes. Moreover, this resilience spanned multiple trophic levels, a significant result for ecologically similar boreal regions, especially given the high potential for increased fires with future climate change.

  19. Molybdenum and phosphorus limitation of moss-associated nitrogen fixation in boreal ecosystems.

    Science.gov (United States)

    Rousk, Kathrin; Degboe, Jefferson; Michelsen, Anders; Bradley, Robert; Bellenger, Jean-Philippe

    2017-04-01

    Biological nitrogen fixation (BNF) performed by moss-associated cyanobacteria is one of the main sources of new nitrogen (N) input in pristine, high-latitude ecosystems. Yet, the nutrients that limit BNF remain elusive. Here, we tested whether this important ecosystem function is limited by the availability of molybdenum (Mo), phosphorus (P), or both. BNF in dominant mosses was measured with the acetylene reduction assay (ARA) at different time intervals following Mo and P additions, in both laboratory microcosms with mosses from a boreal spruce forest and field plots in subarctic tundra. We further used a (15) N2 tracer technique to assess the ARA to N2 fixation conversion ratios at our subarctic site. BNF was up to four-fold higher shortly after the addition of Mo, in both the laboratory and field experiments. A similar positive response to Mo was found in moss colonizing cyanobacterial biomass. As the growing season progressed, nitrogenase activity became progressively more P limited. The ARA : (15) N2 ratios increased with increasing Mo additions. These findings show that N2 fixation activity as well as cyanobacterial biomass in dominant feather mosses from boreal forests and subarctic tundra are limited by Mo availability.

  20. Effects of shading on photosynthesis, plant organic nitrogen uptake and root fungal colonization in a subarctic mire ecosystem

    DEFF Research Database (Denmark)

    Olsrud, Hanna Maria Kerstin; Michelsen, Anders

    2009-01-01

    deciduous and evergreen plant species decreased. Species dominance was correlated with uptake of 13C, i.e., the most productive species also took up the highest amount of glycine. The ecosystem exhibited a tendency towards lower colonization by ericoid mycorrhizal fungi and dark septate endophytes in hair...

  1. Development of palsa mires on the northern European continent in relation to Holocene climatic and environmental changes

    Energy Technology Data Exchange (ETDEWEB)

    Oksanen, P.O.

    2005-07-01

    This thesis deals with the Holocene development of palsa mires in continental Europe, especially permafrost dynamics and its consequences on vegetation succession and peat accumulation. Peat deposits of four permafrost mires in boreal and subarctic northeastern European Russia and in northern oroboreal Finland have been studied using plant macrofossil analysis, (AMS) radiocarbon dating, dry bulk density and carbon content measurements. In addition, preliminary results are available from another palsa mire in northeastern European Russia. Modern vegetation has been investigated to support the interpretation of fossil plant assemblages. Earlier literature on vegetation, stratigraphy and dating of permafrost mires in Europe has been reviewed. The vegetation of palsa mires in general is well known. As a rule, palsas are dry ombrotrophic habitats, surrounded by wet flarks of variable trophic levels. There is a lack of information about vegetation in different small-scale habitats within palsa mires, which would have been useful when studying the permafrost-vegetation relationship. Although no functional indicator species of permafrost have been found, permafrost dynamics in peat stratigraphy can often be detected with high degree of probability based on changes in vegetation. Some plant assemblages and vegetation successions are typical on permafrost, while many species rarely grow on or near to permafrost. Relatively sudden changes between dry and wet mire environments and continuously dynamic conditions are good signs of permafrost impact. Also gradual changes towards drier conditions may be caused by permafrost; in these cases the timing of first permafrost aggradation is more difficult to ascertain and can usually be pronounced only in terms of maximum and minimum ages. Changes in peat accumulation rates and even hiatuses in stratigraphy are additional tools to support the interpretation on permafrost history at the studied sites. Dry organic matter and carbon

  2. Soil organic matter cycling in novel and natural boreal forest ecosystems

    Science.gov (United States)

    Norris, C. E.; Mercier Quideau, S.

    2013-12-01

    The uplands of the western boreal forest of Canada are characterized by a mosaic of pure and mixed stands of aspen (Populus tremuloides Michx.) and spruce (Picea glauca (Moench) Voss). In addition to natural ecosystems, the region is now home to novel ecosystems; i.e., ecosystems composed of reclaimed stands formed from trees planted on constructed anthropogenic soils. To understand potential differences in functioning of these novel ecosystems, we must first better understand the functioning of their natural counterparts. Here we present results on both the characterization and cycling of soil organic matter in novel and natural ecosystems found in the Athabasca oil sands region. Soil organic matter from 42 long term monitoring sites was evaluated for long chain (≥ C21) n-alkane composition. The survey showed that n-alkanes were more concentrated and had distinct signatures in natural compared to novel ecosystems. Mineral soils from reclaimed stands showed a distinct microbial community structure from natural aspen and spruce stands, as was demonstrated using phospholipid fatty acids (PLFAs) as microbial biomarkers following addition of 13C-glucose in a laboratory incubation. Further probing by compound specific analysis of the 13C-enriched PLFAs determined that microbial incorporation of 13C-glucose was different among soils. In a field incubation using 15N labeled aspen litter added to the forest floor of reclaimed, harvested and mature natural aspen stands, the microbial community readily incorporated the tracer and nitrogen was cycled to the above-ground vegetation on all sites. In addition, the amendment of leaf litter to the forest floor also increased soil moisture and soil microbial biomass on both the reclaimed and harvested sites. Utilizing stable isotope tracers in addition to a multi-faceted experimental approach has provided insightful results on the development of soil biogeochemical cycling in novel ecosystems.

  3. Trophic transfer of polychlorinated biphenyls (PCB) in a boreal lake ecosystem: testing of bioaccumulation models.

    Science.gov (United States)

    Figueiredo, Kaisa; Mäenpää, Kimmo; Leppänen, Matti T; Kiljunen, Mikko; Lyytikäinen, Merja; Kukkonen, Jussi V K; Koponen, Hannu; Biasi, Christina; Martikainen, Pertti J

    2014-01-01

    Understanding the fate of persistent organic chemicals in the environment is fundamental information for the successful protection of ecosystems and humans. A common dilemma in risk assessment is that monitoring data reveals contaminant concentrations in wildlife, while the source concentrations, route of uptake and acceptable source concentrations remain unsolved. To overcome this problem, different models have been developed in order to obtain more precise risk estimates for the food webs. However, there is still an urgent need for studies combining modelled and measured data in order to verify the functionality of the models. Studies utilising field-collected data covering entire food webs are particularly scarce. This study aims to contribute to tackling this problem by determining the validity of two bioaccumulation models, BIOv1.22 and AQUAWEBv1.2, for application to a multispecies aquatic food web. A small boreal lake, Lake Kernaalanjärvi, in Finland was investigated for its food web structure and concentrations of PCBs in all trophic levels. Trophic magnification factors (TMFs) were used to measure the bioaccumulation potential of PCBs, and the site-specific environmental parameters were used to compare predicted and observed concentrations. Site-specific concentrations in sediment pore water did not affect the modelling endpoints, but accurate site-specific measurements of freely dissolved concentrations in water turned out to be crucial for obtaining realistic model-predicted concentrations in biota. Numerous parameters and snapshot values affected the model performances, bringing uncertainty into the process and results, but overall, the models worked well for a small boreal lake ecosystem. We suggest that these models can be optimised for different ecosystems and can be useful tools for estimating the bioaccumulation and environmental fate of PCBs.

  4. The resilience and functional role of moss in boreal and arctic ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Turetsky, Merritt; Bond-Lamberty, Benjamin; Euskirchen, Eugenie S.; Talbot, Julie; Frolking, Steve; McGuire, A. David; Tuittila, Eeva-Stiina

    2012-08-24

    Mosses in boreal and arctic ecosystems are ubiquitous components of plant communities, represent an important component of plant diversity, and strongly influence the cycling of water, nutrients, energy and carbon. Here we use a literature review and synthesis as well as model simulations to explore the role of moss in ecological stability and resilience. Our literature review of moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories in boreal and arctic regions. Our modeling simulations suggest that loss of moss within northern plant communities will reduce soil carbon accumulation primarily by influencing decomposition rates and soil nitrogen availability. While two models (HPM and STM-TEM) showed a significant effect of moss removal, results from the Biome-BGC and DVM-TEM models suggest that northern, moss-rich ecosystems would need to experience extreme perturbation before mosses were eliminated. We highlight a number of issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, phenotypical plasticity in traits, and whether the effects of moss on ecosystem processes scale with local abundance. We also suggest that as more models explore issues related to ecological resilience, issues related to both parameter and conceptual uncertainty should be addressed: are the models more limited by uncertainty in the parameterization of the processes included or by what is not represented in the model at all? It seems clear from our review that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species.

  5. Bryophyte-cyanobacteria associations contribute to ecosystem-N-budget of boreal forest

    Science.gov (United States)

    Salemaa, Maija; Lindroos, Antti-Jussi; Merilä, Päivi; Mäkipää, Raisa; Smolander, Aino

    2014-05-01

    Bryophytes frequently dominate the ground vegetation on the forest floor in boreal region. Northern ecosystems are often nitrogen limited, and therefore biological nitrogen (N2) fixation of bryophyte-associated microbes is an important source of new N. In this study we estimated the N stock of bryophyte layer and the N input rate by N2 fixation of bryophyte-cyanobacteria associations at the ecosystem level. We studied 12 intensively monitored forest ecosystem plots (ICP Forests Level II) along a latitudinal gradient in Finland during 2009-2013. The total biomass and N stock of the bryophytes varied 700-2000 kg ha-1 and 9-23 kg ha-1, respectively. N2 fixation rate associated to bryophytes increased towards the north and was at highest 1-2 kg N ha-1 year-1 (based on the bryophyte biomass in the monitoring plots). This N input was at the same level as the N deposition in the northern Finland (1.5 kg N ha-1 year-1). In comparison, via needle litterfall and other tree litter c.a. 5 kg N ha-1 is annually returned to the nutrient cycle. In southern Finland, very low rates of N2 fixation were found probably because of inhibition by the anthropogenic N deposition. The upper parts of the bryophyte shoots showed 2-3 times higher N2-fixing rate than the lower parts, but differences between Hylocomium splendens and Pleurozium schreberi were minor. However, Dicranum species showed much lower N2 fixation rates compared to these two species. The moisture level of bryophytes and light/temperature conditions regulated strongly the rate of N2-fixing activity. The results showed that the bryophyte layer significantly contributes to the N input and plays an important role in controlling the N and C balances of boreal forests.

  6. AVIRIS Land-Surface Mapping in Support of the Boreal Ecosystem-Atmosphere Study (BOREAS)

    Science.gov (United States)

    Roberts, Dar A.; Gamon, John; Keightley, Keir; Prentiss, Dylan; Reith, Ernest; Green, Robert

    2001-01-01

    A key scientific objective of the original Boreal Ecosystem-Atmospheric Study (BOREAS) field campaign (1993-1996) was to obtain the baseline data required for modeling and predicting fluxes of energy, mass, and trace gases in the boreal forest biome. These data sets are necessary to determine the sensitivity of the boreal forest biome to potential climatic changes and potential biophysical feedbacks on climate. A considerable volume of remotely-sensed and supporting field data were acquired by numerous researchers to meet this objective. By design, remote sensing and modeling were considered critical components for scaling efforts, extending point measurements from flux towers and field sites over larger spatial and longer temporal scales. A major focus of the BOREAS follow-on program is concerned with integrating the diverse remotely sensed and ground-based data sets to address specific questions such as carbon dynamics at local to regional scales. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) has the potential of contributing to BOREAS through: (1) accurate retrieved apparent surface reflectance; (2) improved landcover classification; and (3) direct assessment of biochemical/biophysical information such as canopy liquid water and chlorophyll concentration through pigment fits. In this paper, we present initial products for major flux tower sites including: (1) surface reflectance of dominant cover types; (2) a land-cover classification developed using spectral mixture analysis (SMA) and Multiple Endmember Spectral Mixture Analysis (MESMA); and (3) liquid water maps. Our goal is to compare these land-cover maps to existing maps and to incorporate AVIRIS image products into models of photosynthetic flux.

  7. Size-based hydroacoustic measures of within-season fish abundance in a boreal freshwater ecosystem.

    Directory of Open Access Journals (Sweden)

    Riley A Pollom

    Full Text Available Eleven sequential size-based hydroacoustic surveys conducted with a 200 kHz split-beam transducer during the summers of 2011 and 2012 were used to quantify seasonal declines in fish abundance in a boreal reservoir in Manitoba, Canada. Fish densities were sufficiently low to enable single target resolution and tracking. Target strengths converted to log2-based size-classes indicated that smaller fish were consistently more abundant than larger fish by a factor of approximately 3 for each halving of length. For all size classes, in both years, abundance (natural log declined linearly over the summer at rates that varied from -0.067 x day(-1 for the smallest fish to -0.016 x day(-1 for the largest (R2 = 0.24-0.97. Inter-annual comparisons of size-based abundance suggested that for larger fish (>16 cm, mean winter decline rates were an order of magnitude lower (-0.001 x day(-1 and overall survival higher (71% than in the main summer fishing season (mean loss rate -0.038 x day(-1; survival 33%. We conclude that size-based acoustic survey methods have the potential to assess within-season fish abundance dynamics, and may prove useful in long-term monitoring of productivity and hence management of boreal aquatic ecosystems.

  8. Impacts of elevated carbon dioxide and temperature on a boreal forest ecosystem (CLIMEX project)

    DEFF Research Database (Denmark)

    Breemen, N. van; Jenkins, A.; Wright, R.F.

    1998-01-01

    a transparent greenhouse, and the upper 20% of the catchment area is partitioned such that it receives no climate treatment and serves as an untreated control. Both the control and treatment areas inside the greenhouse receive deacidified rain. Within 3 years, soil nitrogen (N) mineralization has increased......To evaluate the effects of climate change on boreal forest ecosystems, both atmospheric CO2 (to 560 ppmv) and air temperature (by 3 degrees-5 degrees C above ambient) were increased at a forested headwater catchment in southern Norway. The entire catchment (860 m(2)) is enclosed within...... and the growing season has been prolonged relative to the control area. This has helped to sustain an increase in plant growth relative to the control and has also promoted increased N export in stream water. Photosynthetic capacity and carbon-nitrogen ratio of new leaves of most plant species did not change...

  9. Response of the boreal forest ecosystem to climatic change and its silvicultural implications

    Energy Technology Data Exchange (ETDEWEB)

    Kellomaeki, S.; Haenninen, H.; Karjalainen, T. [Joensuu Univ. (Finland). Faculty of Forestry] [and others

    1996-12-31

    During the next 100 years, the mean annual temperature is expected to be 1-6 deg C higher than at present. It is also expected to be accompanied by a lengthening of the thermal growing season and increased precipitation. Consequently, climatic change will increase the uncertainty of the management of forest ecosystems in the future. In this context, this research project aimed to outline the ecological and silvicultural implications of climatic change with regard to (1) how the expected climatic change might modify the functioning and structure of the boreal forest ecosystem, and (2) how the silvicultural management of the forest ecosystem should be modified in order to maintain sustainable forest yield under changing climatic conditions. The experimental component of the project concerned first the effect that elevating temperature and elevating concentration of atmospheric carbon have on the ontogenetic development of Scots pine (Pinus sylvestris L) and on the subsequent increase in frost damage during winter. The second part of the study looked the effect of elevating temperature and elevating concentration of atmospheric carbon on the growth of Scots pine through photosynthesis, respiration, transpiration, nutrient supply, and changes in crown structure. This experiment was utilised in several subprojects of the overall project

  10. Aquatic ecosystem responses to Holocene climate change and biome development in boreal, central Asia

    Science.gov (United States)

    Mackay, Anson W.; Bezrukova, Elena V.; Leng, Melanie J.; Meaney, Miriam; Nunes, Ana; Piotrowska, Natalia; Self, Angela; Shchetnikov, Alexander; Shilland, Ewan; Tarasov, Pavel; Wang, Luo; White, Dustin

    2012-05-01

    Boreal ecosystems are highly vulnerable to climate change, and severe ecological impacts in the near future are virtually certain to occur. We undertook a multiproxy study on an alpine lake (ESM-1) at the modern tree-line in boreal, southern Siberia. Steppe and tundra biomes were extensive in eastern Sayan landscapes during the early Holocene. Boreal forest quickly expanded by 9.1 ka BP, and dominated the landscape until c 0.7 ka BP, when the greatest period of compositional turnover occurred. At this time, alpine meadow landscape expanded and Picea obovata colonised new habitats along river valleys and lake shorelines, because of prevailing cool, moist conditions. During the early Holocene, chironomid assemblages were dominated by cold stenotherms. Diatoms for much of the Holocene were dominated by alkaliphilous, fragilarioid taxa, up until 0.2 ka BP, when epiphytic species expanded, indicative of increased habitat availability. C/N mass ratios ranged between 9.5 and 13.5 (11.1-15.8 C/N atomic ratios), indicative of algal communities dominating organic matter contributions to bottom sediments with small, persistent contributions from vascular plants. However, δ13C values increased steadily from -34.9‰ during the early Holocene (9.3 ka BP) to -24.8‰ by 0.6 ka BP. This large shift in magnitude may be due to a number of factors, including increasing within-lake productivity, increasing disequilibrium between the isotopic balance of the lake with the atmosphere as the lake became isotopically ‘mature’, and declining soil respiration linked to small, but distinct retreat in forest biomes. The influence of climatic variables on landscape vegetation was assessed using redundancy analysis (RDA), a linear, direct ordination technique. Changes in July insolation at 60 °N significantly explained over one-fifth of the variation in species composition, while changes in estimates of northern hemisphere temperature and ice-rafted debris events in the North Atlantic

  11. Seasonal and inter-annual variation in ecosystem scale methane emission from a boreal fen

    Science.gov (United States)

    Rinne, Janne; Li, Xuefei; Raivonen, Maarit; Peltola, Olli; Sallantaus, Tapani; Haapanala, Sami; Smolander, Sampo; Alekseychik, Pavel; Aurela, Mika; Korrensalo, Aino; Mammarella, Ivan; Tuittila, Eeva-Stiina; Vesala, Timo

    2016-04-01

    Northern wetlands are one of the major sources of atmospheric methane. We have measured ecosystem scale methane emissions from a boreal fen continuously since 2005. The site is an oligotrophic fen in boreal vegetation zone situated in Siikaneva wetland complex in Southern Finland. The mean annual temperature in the area is 3.3°C and total annual precipitation 710 mm. We have conducted the methane emission measurements by the eddy covariance method. Additionally we have measured fluxes of carbon dioxide, water vapor, and sensible heat together with a suite of other environmental parameters. We have analyzed this data alongside with a model run with University of Helsinki methane model. The measured fluxes show generally highest methane emission in late summers coinciding with the highest temperatures in saturated peat zone. During winters the fluxes show small but detectable emission despite the snow and ice cover on the fen. More than 90% of the annual methane emission occurs in snow-free period. The methane emission and peat temperature are connected in exponential manner in seasonal scales, but methane emission does not show the expected behavior with water table. The lack of water table position dependence also contrasts with the spatial variation across microtopography. There is no systematic variation in sub-diurnal time scale. The general seasonal cycle in methane emission is captured well with the methane model. We will show how well the model reproduces the temperature and water table position dependencies observed. The annual methane emission is typically around 10 gC m-2. This is a significant part of the total carbon exchange between the fen and the atmosphere and about twice the estimated carbon loss by leaching from the fen area. The inter-annual variability in the methane emission is modest. The June-September methane emissions from different years, comprising most of the annual emission, correlates positively with peat temperature, but not with

  12. Natural disturbance impacts on ecosystem services and biodiversity in temperate and boreal forests.

    Science.gov (United States)

    Thom, Dominik; Seidl, Rupert

    2016-08-01

    In many parts of the world forest disturbance regimes have intensified recently, and future climatic changes are expected to amplify this development further in the coming decades. These changes are increasingly challenging the main objectives of forest ecosystem management, which are to provide ecosystem services sustainably to society and maintain the biological diversity of forests. Yet a comprehensive understanding of how disturbances affect these primary goals of ecosystem management is still lacking. We conducted a global literature review on the impact of three of the most important disturbance agents (fire, wind, and bark beetles) on 13 different ecosystem services and three indicators of biodiversity in forests of the boreal, cool- and warm-temperate biomes. Our objectives were to (i) synthesize the effect of natural disturbances on a wide range of possible objectives of forest management, and (ii) investigate standardized effect sizes of disturbance for selected indicators via a quantitative meta-analysis. We screened a total of 1958 disturbance studies published between 1981 and 2013, and reviewed 478 in detail. We first investigated the overall effect of disturbances on individual ecosystem services and indicators of biodiversity by means of independence tests, and subsequently examined the effect size of disturbances on indicators of carbon storage and biodiversity by means of regression analysis. Additionally, we investigated the effect of commonly used approaches of disturbance management, i.e. salvage logging and prescribed burning. We found that disturbance impacts on ecosystem services are generally negative, an effect that was supported for all categories of ecosystem services, i.e. supporting, provisioning, regulating, and cultural services (P < 0.001). Indicators of biodiversity, i.e. species richness, habitat quality and diversity indices, on the other hand were found to be influenced positively by disturbance (P < 0.001). Our analyses thus

  13. Spatial variation in vegetation productivity trends, fire disturbance, and soil carbon across arctic-boreal permafrost ecosystems

    Science.gov (United States)

    Loranty, Michael M.; Liberman-Cribbin, Wil; Berner, Logan T.; Natali, Susan M.; Goetz, Scott J.; Alexander, Heather D.; Kholodov, Alexander L.

    2016-09-01

    In arctic tundra and boreal forest ecosystems vegetation structural and functional influences on the surface energy balance can strongly influence permafrost soil temperatures. As such, vegetation changes will likely play an important role in permafrost soil carbon dynamics and associated climate feedbacks. Processes that lead to changes in vegetation, such as wildfire or ecosystem responses to rising temperatures, are of critical importance to understanding the impacts of arctic and boreal ecosystems on future climate. Yet these processes vary within and between ecosystems and this variability has not been systematically characterized across the arctic-boreal region. Here we quantify the distribution of vegetation productivity trends, wildfire, and near-surface soil carbon, by vegetation type, across the zones of continuous and discontinuous permafrost. Siberian larch forests contain more than one quarter of permafrost soil carbon in areas of continuous permafrost. We observe pervasive positive trends in vegetation productivity in areas of continuous permafrost, whereas areas underlain by discontinuous permafrost have proportionally less positive productivity trends and an increase in areas exhibiting negative productivity trends. Fire affects a much smaller proportion of the total area and thus a smaller amount of permafrost soil carbon, with the vast majority occurring in deciduous needleleaf forests. Our results indicate that vegetation productivity trends may be linked to permafrost distribution, fire affects a relatively small proportion of permafrost soil carbon, and Siberian larch forests will play a crucial role in the strength of the permafrost carbon climate feedback.

  14. A MESO-β SCALE SIMULATION OF THE EFFECTS OF BOREAL FOREST ECOSYSTEM ON THE LOWER ATMOSPHERE

    Institute of Scientific and Technical Information of China (English)

    王汉杰; Yi-Fan LI; Aloysius K.LO

    2001-01-01

    Based on the Intensive Field Campaign (IFC-I) data of Boreal Ecosystem-Atmosphere Study(BOREAS), a three-dimensional meso-β scale model is used to simulate the effect of boreal forests on the lower atmosphere. A fine horizontal resolution of 2 km × 2 km is used in order to distinguish the vegetative heterogeneity in the boreal region. A total of 20 × 25 grid points cover the entire sub modeling area in BOREAS' South Study Area (SSA). The ecosystem types and their coverage in each grid square are extracted from the North American Land Cover Characteristics Data Base(NALCCD) generated by the U.S. Geographical Survey (USGS) and the University of Nebraska Lincoln (UNL). The topography of the study area is taken from the Digital Elevation Map (DEM)of USGS. The model outputs include the components of the energy balance budget within the canopy and at the ground, the turbulence parameters in the atmospheric boundary layer and the wind,temperature and humidity profiles extending up to a height of 1500 m. In addition to the fine time nd spatial step, the unique feature of the present model is the incorporation of both dynamic and biological effects of the Boreal forest into the model parameterization scheme. The model results compare favorably with BOREAS' IFC-1 data in 1994 when the forest was in the luxuriant growing period.

  15. Moss-cyanobacteria associations as biogenic sources of nitrogen in boreal forest ecosystems

    Directory of Open Access Journals (Sweden)

    Kathrin eRousk

    2013-06-01

    Full Text Available The biological fixation of atmospheric nitrogen (N is a major pathway for available N entering ecosystems. In N-limited boreal forests, a significant amount of N2 is fixed by cyanobacteria living in association with mosses, contributing up to 50 % to the total N input. In this review, we synthesize reports on the drivers of N2 fixation in feather moss-cyanobacteria associations to gain a deeper understanding of their role for ecosystem-N-cycling. Nitrogen fixation in moss-cyanobacteria associations is inhibited by N inputs and therefore, significant fixation occurs only in low N-deposition areas. While it has been shown that artificial N additions in the laboratory as well as in the field inhibit N2 fixation in moss-cyanobacteria associations, the type, as well as the amounts of N that enters the system, affect N2 fixation differently. Another major driver of N2 fixation is the moisture status of the cyanobacteria-hosting moss, wherein moist conditions promote N2 fixation. Mosses experience large fluctuations in their hydrological status, undergoing significant natural drying and rewetting cycles over the course of only a few hours, especially in summer, which likely compromises the N input to the system via N2 fixation. Perhaps the most central question, however, that remains unanswered is the fate of the fixed N2 in mosses. The cyanobacteria are likely to leak N, but whether this N is transferred to the soil and if so, at which rates and timescales, is unknown. Despite our increasing understanding of the drivers of N2 fixation, the role moss-cyanobacteria associations play in ecosystem-N-cycling remains unresolved. Further, the relationship mosses and cyanobacteria share is unknown to date and warrants further investigation.

  16. Moss-cyanobacteria associations as biogenic sources of nitrogen in boreal forest ecosystems.

    Science.gov (United States)

    Rousk, Kathrin; Jones, Davey L; Deluca, Thomas H

    2013-01-01

    The biological fixation of atmospheric nitrogen (N) is a major pathway for available N entering ecosystems. In N-limited boreal forests, a significant amount of N2 is fixed by cyanobacteria living in association with mosses, contributing up to 50% to the total N input. In this review, we synthesize reports on the drivers of N2 fixation in feather moss-cyanobacteria associations to gain a deeper understanding of their role for ecosystem-N-cycling. Nitrogen fixation in moss-cyanobacteria associations is inhibited by N inputs and therefore, significant fixation occurs only in low N-deposition areas. While it has been shown that artificial N additions in the laboratory as well as in the field inhibit N2 fixation in moss-cyanobacteria associations, the type, as well as the amounts of N that enters the system, affect N2 fixation differently. Another major driver of N2 fixation is the moisture status of the cyanobacteria-hosting moss, wherein moist conditions promote N2 fixation. Mosses experience large fluctuations in their hydrological status, undergoing significant natural drying and rewetting cycles over the course of only a few hours, especially in summer, which likely compromises the N input to the system via N2 fixation. Perhaps the most central question, however, that remains unanswered is the fate of the fixed N2 in mosses. The cyanobacteria are likely to leak N, but whether this N is transferred to the soil and if so, at which rates and timescales, is unknown. Despite our increasing understanding of the drivers of N2 fixation, the role moss-cyanobacteria associations play in ecosystem-N-cycling remains unresolved. Further, the relationship mosses and cyanobacteria share is unknown to date and warrants further investigation.

  17. The role of forest floor and trees to the ecosystem scale methane budget of boreal forests

    Science.gov (United States)

    Pihlatie, Mari; Halmeenmäki, Elisa; Peltola, Olli; Haikarainen, Iikka; Heinonsalo, Jussi; Santalahti, Minna; Putkinen, Anuliina; Fritze, Hannu; Urban, Otmar; Machacova, Katerina

    2016-04-01

    Boreal forests are considered as a sink of atmospheric methane (CH4) due to the activity of CH4 oxidizing bacteria (methanotrophs) in the soil. This soil CH4 sink is especially strong for upland forest soils, whereas forests growing on organic soils may act as small sources due to the domination of CH4 production by methanogens in the anaerobic parts of the soil. The role of trees to the ecosystem-scale CH4 fluxes has until recently been neglected due to the perception that trees do not contribute to the CH4 exchange, and also due to difficulties in measuring the CH4 exchange from trees. Findings of aerobic CH4 formation in plants and emissions from tree-stems in temperate and tropical forests during the past decade demonstrate that our understanding of CH4 cycling in forest ecosystems is not complete. Especially the role of forest canopies still remain unresolved, and very little is known of CH4 fluxes from trees in boreal region. We measured the CH4 exchange of tree-stems and tree-canopies from pine (Pinus sylvestris), spruce (Picea abies) and birch (Betula pubescens, Betula pendula) trees growing in Southern Finland (SMEAR II station) on varying soil conditions, from upland mineral soils to paludified soil. We compared the CH4 fluxes from trees to forest-floor CH4 exchange, both measured by static chambers, and to CH4 fluxes measured above the forest canopy by a flux gradient technique. We link the CH4 fluxes from trees and forest floor to physiological activity of the trees, such as transpiration, sap-flow, CO2 net ecosystem exchange (NEE), soil properties such as temperature and moisture, and to the presence of CH4 producing methanogens and CH4 oxidizing methanotrophs in trees or soil. The above canopy CH4 flux measurements show that the whole forest ecosystem was a small source of CH4 over extended periods in the spring and summer 2012, 2014 and 2015. Throughout the 2013-2014 measurements, the forest floor was in total a net sink of CH4, with variation

  18. Effects of climatic changes on carbon dioxide and water vapor fluxes in boreal forest ecosystems of European part of Russia

    Science.gov (United States)

    Olchev, A.; Novenko, E.; Desherevskaya, O.; Krasnorutskaya, K.; Kurbatova, J.

    2009-10-01

    Effects of possible climatic and vegetation changes on H2O and CO2 fluxes in boreal forest ecosystems of the central part of European Russia were quantified using modeling and experimental data. The future pattern of climatic conditions for the period up to 2100 was derived using the global climatic model ECHAM5 (Roeckner et al 2003 The Atmospheric General Circulation Model ECHAM 5. PART I: Model Description, Report 349 (Hamburg: Max-Planck Institute for Meteorology) p 127) with the A1B emission scenario. The possible trends of future vegetation changes were obtained by reconstructions of vegetation cover and paleoclimatic conditions in the Late Pleistocene and Holocene, as provided from pollen and plant macrofossil analysis of profiles in the Central Forest State Natural Biosphere Reserve (CFSNBR). Applying the method of paleoanalogues demonstrates that increasing the mean annual temperature, even by 1-2 °C, could result in reducing the proportion of spruce in boreal forest stands by up to 40%. Modeling experiments, carried out using a process-based Mixfor-SVAT model, show that the expected future climatic and vegetation changes lead to a significant increase of net ecosystem exchange (NEE) and gross primary productivity (GPP) of the boreal forests. Despite the expected warming and moistening of the climate, the modeling experiments indicate a relatively weak increase of annual evapotranspiration (ET) and even a reduction of transpiration (TR) rates of forest ecosystems compared to present conditions.

  19. Decadal and long-term boreal soil carbon and nitrogen sequestration rates across a variety of ecosystems

    Science.gov (United States)

    Manies, Kristen L.; Harden, Jennifer W.; Fuller, Christopher C.; Turetsky, Merritt

    2016-01-01

    Boreal soils play a critical role in the global carbon (C) cycle; therefore, it is important to understand the mechanisms that control soil C accumulation and loss for this region. Examining C & nitrogen (N) accumulation rates over decades to centuries may provide additional understanding of the dominant mechanisms for their storage, which can be masked by seasonal and interannual variability when investigated over the short term. We examined longer-term accumulation rates, using 210Pb and 14C to date soil layers, for a wide variety of boreal ecosystems: a black spruce forest, a shrub ecosystem, a tussock grass ecosystem, a sedge-dominated ecosystem, and a rich fen. All ecosystems had similar decadal C accumulation rates, averaging 84 ± 42 gC m−2 yr−1. Long-term (century) C accumulation rates were slower than decadal rates, averaging 14 ± 5 gC m−2 yr−1 for all ecosystems except the rich fen, for which the long-term C accumulation rates was more similar to decadal rates (44 ± 5 and 76 ± 9 gC m−2 yr−1, respectively). The rich fen also had the highest long-term N accumulation rates (2.7 gN m−2 yr−1). The lowest N accumulation rate, on both a decadal and long-term basis, was found in the black spruce forest (0.2 and 1.4 gN m−2 yr−1, respectively). Our results suggest that the controls on long-term C and N cycling at the rich fen is fundamentally different from the other ecosystems, likely due to differences in the predominant drivers of nutrient cycling (oxygen availability, for C) and reduced amounts of disturbance by fire (for C and N). This result implies that most shifts in ecosystem vegetation across the boreal region, driven by either climate or succession, will not significantly impact regional C or N dynamics over years to decades. However, ecosystem transitions to or from a rich fen will promote significant shifts in soil C and N storage.

  20. Decadal and long-term boreal soil carbon and nitrogen sequestration rates across a variety of ecosystems

    Science.gov (United States)

    Manies, Kristen L.; Harden, Jennifer W.; Fuller, Christopher C.; Turetsky, Merritt R.

    2016-08-01

    Boreal soils play a critical role in the global carbon (C) cycle; therefore, it is important to understand the mechanisms that control soil C accumulation and loss for this region. Examining C & nitrogen (N) accumulation rates over decades to centuries may provide additional understanding of the dominant mechanisms for their storage, which can be masked by seasonal and interannual variability when investigated over the short term. We examined longer-term accumulation rates, using 210Pb and 14C to date soil layers, for a wide variety of boreal ecosystems: a black spruce forest, a shrub ecosystem, a tussock grass ecosystem, a sedge-dominated ecosystem, and a rich fen. All ecosystems had similar decadal C accumulation rates, averaging 84 ± 42 gC m-2 yr-1. Long-term (century) C accumulation rates were slower than decadal rates, averaging 14 ± 5 gC m-2 yr-1 for all ecosystems except the rich fen, for which the long-term C accumulation rates was more similar to decadal rates (44 ± 5 and 76 ± 9 gC m-2 yr-1, respectively). The rich fen also had the highest long-term N accumulation rates (2.7 gN m-2 yr-1). The lowest N accumulation rate, on both a decadal and long-term basis, was found in the black spruce forest (0.2 and 1.4 gN m-2 yr-1, respectively). Our results suggest that the controls on long-term C and N cycling at the rich fen is fundamentally different from the other ecosystems, likely due to differences in the predominant drivers of nutrient cycling (oxygen availability, for C) and reduced amounts of disturbance by fire (for C and N). This result implies that most shifts in ecosystem vegetation across the boreal region, driven by either climate or succession, will not significantly impact regional C or N dynamics over years to decades. However, ecosystem transitions to or from a rich fen will promote significant shifts in soil C and N storage.

  1. Influence of different tree-harvesting intensities on forest soil carbon stocks in boreal and northern temperate forest ecosystems

    DEFF Research Database (Denmark)

    Clarke, Nicholas; Gundersen, Per; Jönsson-Belyazid, Ulrika;

    2015-01-01

    Effective forest governance measures are crucial to ensure sustainable management of forests, but so far there has been little specific focus in boreal and northern temperate forests on governance measures in relation to management effects, including harvesting effects, on soil organic carbon (SOC......) stocks. This paper reviews the findings in the scientific literature concerning the effects of harvesting of different intensities on SOC stocks and fluxes in boreal and northern temperate forest ecosystems to evaluate the evidence for significant SOC losses following biomass removal. An overview...... of existing governance measures related to SOC is given, followed by a discussion on how scientific findings could be incorporated in guidelines and other governance measures. The currently available information does not support firm conclusions about the long-term impact of intensified forest harvesting...

  2. Modelling soil temperature and moisture and corresponding seasonality of photosynthesis and transpiration in a boreal spruce ecosystem

    Directory of Open Access Journals (Sweden)

    S. H. Wu

    2013-02-01

    Full Text Available Recovery of photosynthesis and transpiration is strongly restricted by low temperatures in air and/or soil during the transition period from winter to spring in boreal zones. The extent to which air temperature (Ta and soil temperature (Ts influence the seasonality of photosynthesis and transpiration of a boreal spruce ecosystem was investigated using a process-based ecosystem model (CoupModel together with eddy covariance (EC data from one eddy flux tower and nearby soil measurements at Knottåsen, Sweden. A Monte Carlo-based uncertainty method (GLUE provided prior and posterior distributions of simulations representing a wide range of soil conditions and performance indicators. The simulated results showed sufficient flexibility to predict the measured cold and warm Ts in the moist and dry plots around the eddy flux tower. Moreover, the model presented a general ability to describe both biotic and abiotic processes for the Norway spruce stand. The dynamics of sensible heat fluxes were well described by the corresponding latent heat fluxes and net ecosystem exchange of CO2. The parameter ranges obtained are probably valid to represent regional characteristics of boreal conifer forests, but were not easy to constrain to a smaller range than that produced by the assumed prior distributions. Finally, neglecting the soil temperature response function resulted in fewer behavioural models and probably more compensatory errors in other response functions for regulating the seasonality of ecosystem fluxes.

  3. Modelling soil temperature and moisture and corresponding seasonality of photosynthesis and transpiration in a boreal spruce ecosystem

    Directory of Open Access Journals (Sweden)

    S. H. Wu

    2012-05-01

    Full Text Available Recovery of photosynthesis and transpiration is strongly restricted by low temperatures in air and/or soil during the transition period from winter to spring in boreal zones. The extent to which air temperature (Ta and soil temperature (Ts influence the seasonality of photosynthesis and transpiration of a boreal spruce ecosystem was investigated using a process-based ecosystem model (CoupModel together with eddy covariance (EC data from one eddy flux tower and nearby soil measurements at Knottåsen, Sweden. A Monte Carlo based uncertainty method (GLUE provided prior and posterior distributions of simulations representing a wide range of soil conditions and performance indicators. The simulated results showed sufficient flexibility to predict the measured cold and warm Ts in the moist and dry plots around the eddy flux tower. Moreover, the model presented a general ability to describe both biotic and abiotic processes for the Norway spruce stand. The dynamics of sensible heat fluxes were well described the corresponding latent heat fluxes and net ecosystem exchange of CO2. The parameter ranges obtained are probably valid to represent regional characteristics of boreal conifer forests, but were not easy to constrain to a smaller range than that produced by the assumed prior distributions. Finally, neglecting the soil temperature response function resulted in fewer behavioural models and probably more compensatory errors in other response functions for regulating the seasonality of ecosystem fluxes.

  4. The potentiation of zinc toxicity by soil moisture in a boreal forest ecosystem.

    Science.gov (United States)

    Owojori, Olugbenga J; Siciliano, Steven D

    2015-03-01

    Northern boreal forests often experience forest dieback as a result of metal ore mining and smelting. The common solution is to lime the soil, which increases pH, reducing metal toxicity and encouraging recovery. In certain situations, however, such as in Flin Flon, Manitoba, Canada, liming has yielded only moderate benefits, with some locations responding well to liming and other locations not at all. In an effort to increase the effectiveness of the ecorestoration strategy, the authors investigated if these differences in liming responsiveness were linked to differences in toxicity. Toxicity of metal-impacted Flin Flon soils on the oribatid mite Oppia nitens and the collembolan Folsomia candida was assessed, with a view toward identifying the metal of concern in the area. The effects of moisture content on metal sorption, uptake, and toxicity to the invertebrates were also investigated. Toxicity tests with the invertebrates were conducted using either Flin Flon soils or artificial soils with moisture content adjusted to 30%, 45%, 60%, or 75% of the maximum water-holding capacity of the soil samples. The Relative to Cd Toxicity Model identified Zn as the metal of concern in the area, and this was confirmed using validation tests with field contaminated soils. Furthermore, increasing the moisture content in soils increased the amount of mobile Zn available for uptake with the ion exchange resin. Survival and reproduction of both invertebrates were reduced under Zn exposure as moisture level increased. Thus, moisture-collecting landforms, which are often also associated with high Zn concentrations at Flin Flon, have, as a result, higher Zn toxicity to the soil ecosystem because of increases in soil moisture.

  5. Vapor pressure deficit controls on fire ignition and fire spread in boreal forest ecosystems

    Directory of Open Access Journals (Sweden)

    F. Sedano

    2014-01-01

    Full Text Available Climate-driven changes in the fire regime within boreal forest ecosystems are likely to have important effects on carbon cycling and species composition. In the context of improving fire management options and developing more realistic scenarios of future change, it is important to understand how meteorology regulates different fire processes, including ignition, daily fire spread rates, and cumulative annual burned area. Here we combined MODIS active fires (MCD14ML, MODIS imagery (MOD13A1 and ancillary historic fire perimeter information to produce a dataset of daily fire spread maps of Alaska for the period 2002–2011. This approach provided a spatial and temporally continuous representation of fire progression and a precise identification of ignition and extinction locations and dates for each wildfire. The fire-spread maps were analyzed together with daily vapor pressure deficit (VPD observations from the North American Regional Reanalysis (NARR and lightning strikes from the Alaska Lightning Detection Network (ALDN. We found a significant relationship between daily VPD and probability that a lightning strike would develop into a fire ignition. In the first 5 days after ignition, above average VPD increased the probability that fires would grow to large or very large sizes. Strong relationships also were identified between VPD and burned area at several levels of temporal and spatial aggregation. As a consequence of regional coherence in meteorology, ignition, daily fire spread rates, and fire extinction events were often synchronized across different fires in interior Alaska. At a regional scale, the sum of positive VPD anomalies during the fire season was positively correlated with annual burned area during the NARR era (1979–2011; R2 = 0.45. Some of the largest fires we mapped had slow initial growth, indicating opportunities may exist for suppression efforts to adaptively manage these forests for climate change. The results of our

  6. Impacts of climatic changes on carbon and water balance components of boreal forest ecosystems in central part of European Russia

    Science.gov (United States)

    Olchev, A.; Novenko, E.; Desherevskaya, O.; Kurbatova, J.

    2009-04-01

    Within the framework of the study the possible impacts of climatic changes on carbon and water balances of boreal forest ecosystems of the central part of European Russia for period up to 2100 was estimated using results of model simulations and field measurements. The boreal forests of the Central Forest State Natural Biosphere Reserve (CFSNBR) were selected for the study. They are located at the southern boundary of south taiga zone in the European part of Russia (Tver region) and it can be expected that they will be very sensitive to modern climate warming. Expected future pattern of climatic parameters in the study area was derived using the global climatic model ECHAM5 (MPI Hamburg, Germany) and climatic scenarios B1, A1B and A2 (IPCC 2007). The possible scenarios of species composition changes of the boreal forests were developed using reconstructions of Holocene vegetation cover and climatic conditions on the base of pollen and plant macrofossil analysis of peat profiles in CFSNBR. The annual future pattern of CO2 and H2O fluxes of the forests were simulated using a process-based Mixfor-SVAT model (Olchev et al. 2002, 2008). The main advantage of Mixfor-SVAT is that it allows us to describe CO2 and H2O fluxes both in mono-specific and mixed forest stands. It is able to quantify both total ecosystem fluxes and flux partitioning among different tree species and canopy layers. It is obvious that it can be very helpful to describe accurately effects of species composition changes on structure of dynamics of carbon and water balance of forest ecosystems. Results of modeling experiments show that expected climatic and vegetation changes can have significant impact on evapotranspiration, transpiration, Net Ecosystem Exchange (NEE), Gross (GPP) and Net (NPP) Primary Productivities of boreal forest ecosystems. These changes have a clear seasonal trend and they are depended on species composition of a forest stand. This study was supported by the Russian Foundation

  7. Spatially explicit simulation of hydrologically controlled carbon and nitrogen cycles and associated feedback mechanisms in a boreal ecosystem

    Science.gov (United States)

    Govind, Ajit; Chen, Jing Ming; Ju, Weimin

    2009-06-01

    Ecosystem models that simulate biogeochemical processes usually ignore hydrological controls that govern them. It is quite possible that topographically driven water fluxes significantly influence the spatial distribution of C sources and sinks because of their large contribution to the local water balance. To investigate this, we simulated biogeochemical processes along with the associated feedback mechanisms in a boreal ecosystem using a spatially explicit hydroecological model, boreal ecosystem productivity simulator (BEPS)-TerrainLab V2.0, that has a tight coupling of ecophysiological, hydrological, and biogeochemical processes. First, the simulated dynamics of snowpack, soil temperature, net ecosystem productivity (NEP), and total ecosystem respiration (TER) were validated with high-frequency measurements for 2 years. The model was able to explain 80% of the variability in NEP and 84% of the variability in TER. Further, we investigated the influence of topographically driven subsurface base flow on soil C and N cycling and on the spatiotemporal patterns of C sources and sinks using three hydrological modeling scenarios that differed in hydrological conceptualizations. In general, the scenarios that had nonexplicit hydrological representation overestimated NEP, as opposed to the scenario that had an explicit (realistic) representation. The key processes controlling the NEP differences were attributed to the combined effects of variations in photosynthesis (due to changes in stomatal conductance and nitrogen (N) availability), heterotrophic respiration, and autotrophic respiration, all of which occur simultaneously affecting NEP. Feedback relationships were also found to exacerbate the differences. We identified six types of NEP differences (biases), of which the most commonly found was due to an underestimation of the existing C sources, highlighting the vulnerability of regional-scale ecosystem models that ignore hydrological processes.

  8. A spatially explicit hydro-ecological modeling framework (BEPS-TerrainLab V2.0): Model description and test in a boreal ecosystem in Eastern North America

    Science.gov (United States)

    Govind, Ajit; Chen, Jing Ming; Margolis, Hank; Ju, Weimin; Sonnentag, Oliver; Giasson, Marc-André

    2009-04-01

    SummaryA spatially explicit, process-based hydro-ecological model, BEPS-TerrainLab V2.0, was developed to improve the representation of ecophysiological, hydro-ecological and biogeochemical processes of boreal ecosystems in a tightly coupled manner. Several processes unique to boreal ecosystems were implemented including the sub-surface lateral water fluxes, stratification of vegetation into distinct layers for explicit ecophysiological representation, inclusion of novel spatial upscaling strategies and biogeochemical processes. To account for preferential water fluxes common in humid boreal ecosystems, a novel scheme was introduced based on laboratory analyses. Leaf-scale ecophysiological processes were upscaled to canopy-scale by explicitly considering leaf physiological conditions as affected by light and water stress. The modified model was tested with 2 years of continuous measurements taken at the Eastern Old Black Spruce Site of the Fluxnet-Canada Research Network located in a humid boreal watershed in eastern Canada. Comparison of the simulated and measured ET, water-table depth (WTD), volumetric soil water content (VSWC) and gross primary productivity (GPP) revealed that BEPS-TerrainLab V2.0 simulates hydro-ecological processes with reasonable accuracy. The model was able to explain 83% of the ET, 92% of the GPP variability and 72% of the WTD dynamics. The model suggests that in humid ecosystems such as eastern North American boreal watersheds, topographically driven sub-surface baseflow is the main mechanism of soil water partitioning which significantly affects the local-scale hydrological conditions.

  9. Constraining ecosystem model with adaptive Metropolis algorithm using boreal forest site eddy covariance measurements

    Science.gov (United States)

    Mäkelä, Jarmo; Susiluoto, Jouni; Markkanen, Tiina; Aurela, Mika; Järvinen, Heikki; Mammarella, Ivan; Hagemann, Stefan; Aalto, Tuula

    2016-12-01

    We examined parameter optimisation in the JSBACH (Kaminski et al., 2013; Knorr and Kattge, 2005; Reick et al., 2013) ecosystem model, applied to two boreal forest sites (Hyytiälä and Sodankylä) in Finland. We identified and tested key parameters in soil hydrology and forest water and carbon-exchange-related formulations, and optimised them using the adaptive Metropolis (AM) algorithm for Hyytiälä with a 5-year calibration period (2000-2004) followed by a 4-year validation period (2005-2008). Sodankylä acted as an independent validation site, where optimisations were not made. The tuning provided estimates for full distribution of possible parameters, along with information about correlation, sensitivity and identifiability. Some parameters were correlated with each other due to a phenomenological connection between carbon uptake and water stress or other connections due to the set-up of the model formulations. The latter holds especially for vegetation phenology parameters. The least identifiable parameters include phenology parameters, parameters connecting relative humidity and soil dryness, and the field capacity of the skin reservoir. These soil parameters were masked by the large contribution from vegetation transpiration. In addition to leaf area index and the maximum carboxylation rate, the most effective parameters adjusting the gross primary production (GPP) and evapotranspiration (ET) fluxes in seasonal tuning were related to soil wilting point, drainage and moisture stress imposed on vegetation. For daily and half-hourly tunings the most important parameters were the ratio of leaf internal CO2 concentration to external CO2 and the parameter connecting relative humidity and soil dryness. Effectively the seasonal tuning transferred water from soil moisture into ET, and daily and half-hourly tunings reversed this process. The seasonal tuning improved the month-to-month development of GPP and ET, and produced the most stable estimates of water use

  10. Mobility of radiocaesium in boreal forest ecosystems: Influence of precipitation chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Steinnes, E. [Department of Chemistry, Norwegian University of Science and Technology (Norway); Gjelsvik, R.; Skuterud, L.; Thoerring, H. [Norwegian Radiation Protection Authority (Norway)

    2014-07-01

    Mobility and plant uptake of Cs in soils is generally limited by the presence of clay minerals in the soil. However, cations supplied by precipitation may substantially influence the mobility of radiocaesium in natural surface soil and subsequent transfer to food chains. The chemical composition of precipitation shows substantial variation among different areas in Norway for two main reasons. At sites close to the coast the atmospheric supply of marine cations and anions is many-fold greater than in regions shielded from marine influence by mountains. The southernmost part of the country has been, and still is, substantially affected by soil acidification due to long-range atmospheric transport of acidifying substances from areas elsewhere in Europe. This may explain a much higher greater uptake of {sup 137}Cs from the Chernobyl accident in moose in this region than elsewhere (Steinnes et al., 2009), in spite of the fact that some areas farther north received substantially greater fallout. Similarly a much greater transfer of {sup 137}Cs to natural birch forest vegetation is evident from the more acidified soils in the south than in comparable ecosystems elsewhere in the country (Thoerring et al., 2012). Repeated recordings of activity levels in natural surface soils showed faster leaching of Chernobyl {sup 137}Cs relative to inland areas not only in the south but also in coastal areas farther north (Gjelsvik and Steinnes, 2013), indicating that the amounts of marine cations in precipitation also has an appreciable effect on the Cs leaching. The geographical leaching differences still became less prominent with time. Recent lysimeter experiments with undisturbed soil columns obtained from an area receiving high radiocaesium deposition from the Chernobyl accident, applying precipitation with ionic composition characteristic of the different regions mentioned above, did not change the current depth distribution of {sup 137}Cs. However, acidic precipitation increased

  11. Effect of ecosystem retrogression on stable nitrogen and carbon isotopes of plants, soils and consumer organisms in boreal forest islands.

    Science.gov (United States)

    Hyodo, Fujio; Wardle, David A

    2009-07-01

    In the prolonged absence of catastrophic disturbance, ecosystem retrogression occurs, and this involves increased nutrient limitation, and reduced aboveground and belowground ecosystem processes rates. Little is known about how the nitrogen and carbon stable isotope ratios (delta(15)N and delta(13)C) of plants, soils and consumer organisms respond to retrogression in boreal forests. We investigated a 5000 year chronosequence of forested islands in the boreal zone of northern Sweden, for which the time since lightning-induced wildfire increases with decreasing island size, leading to ecosystem retrogression. For this system, tissue delta(15)N of three abundant plant species (Betula pubescens, Vaccinium myrtillus and Pleurozium schreberi) and humus all increased as retrogression proceeded. This is probably due to enhanced ecosystem inputs of N by biological fixation, and greater dependency of the plants on organic N during retrogression. The delta(13)C of B. pubescens and plant-derived humus also increased during retrogression, probably through nutrient limitation increasing plant physiological stress. Unlike the plants, delta(15)N of invertebrates (lycosid spiders and ants) did not increase during retrogression, probably because of their partial dependence on aquatic-derived prey that had a variable delta(15)N signature. The delta(13)C of the invertebrates increased as retrogression proceeded and converged towards that of an aquatic prey source (chironomid flies), suggesting increased dependence on aquatic-derived prey during retrogression. These results show that measurement of delta(15)N and delta(13)C of plants, soils, and consumers across the same environmental gradient can provide insights into environmental factors that drive both the aboveground and belowground subsystems, as well as the linkages between them.

  12. Small Boreal Lake Ecosystem Evolution under the Influence of Natural and Anthropogenic Factors: Results of Multidisciplinary Long-Term Study

    Directory of Open Access Journals (Sweden)

    Liudmila Shirokova

    2016-07-01

    Full Text Available Small aquatic ecosystems of the boreal zone are known to be most sensitive indicators of on-going environmental change as well as local anthropogenic pressure, while being highly vulnerable to external impacts. Compared to rather detailed knowledge of the evolution of large and small lakes in Scandinavia and Canada, and large lakes in Eurasia, highly abundant small boreal lakes of northwest Russia have received very little attention, although they may become important centers of attraction of growing rural population in the near future. Here we present the results of a multidisciplinary, multi-annual study of a small boreal humic lake of NW Russia. A shallow (3 m and a deep (16 m site of this lake were regularly sampled for a range of chemical and biological parameters. Average multi-daily, summer-time values of the epilimnion (upper oxygenated layer of the lake provided indications of possible trends in temperature, nutrients, and bacterio-plankton concentration that revealed the local pollution impact in the shallow zone and overall environmental trend in the deep sampling point of the lake. Organic phosphorus, nitrate, and lead were found to be most efficient tracers of local anthropogenic pollution, especially visible in the surface layer of the shallow site of the lake. Cycling of trace elements between the epilimnion and hypolimnion is tightly linked to dissolved organic matter speciation and size fractionation due to the dominance of organic and organo-ferric colloids. The capacity of lake self-purification depends on the ratio of primary productivity to mineralization of organic matter. This ratio remained >1 both during winter and summer periods, which suggests a high potential of lake recovery from the input of allochthonous dissolved organic matter and local anthropogenic pollution.

  13. Coupling of Water and Carbon Cycles in Boreal Ecosystems at Watershed and National Scales

    Science.gov (United States)

    Chen, J. M.; Ju, W.; Govind, A.; Sonnentag, O.

    2009-05-01

    The boreal landscapes is relatively flat giving the impression of spatial homogeneity. However, glacial activities have left distinct fingerprints on the vegetation distribution on moderately rolling terrains over the boreal landscape. Upland or lowland forests types or wetlands having various degrees of hydrological connectivitiy to the surrounding terrain are typical of the boreal landscape. The nature of the terrain creates unique hydrological conditions affecting the local-scale ecophysiological and biogeochemical processes. As part of the Canadian Carbon Program, we investigated the importance of lateral water redistribution through surface and subsurface flows in the spatial distribution of the vertical fluxes of water and carbon. A spatially explicit hydroecological model (BEPS-TerrainLab) has been developed and tested in forested and wetland watersheds . Remotely sensed vegetation parameters along with other spatial datasets are used to run this model, and tower flux data are used for partial validation. It is demonstrated in both forest and wetland watersheds that ignoring the lateral water redistribution over the landscape, commonly done in 1-dimensional bucket models, can cause considerable biases in the vertical carbon and water flux estimation, in addition to the distortion of the spatial patterns of these fluxes. The biases in the carbon flux are considerably larger than those in the water flux. The significance of these findings in national carbon budget estimation is demonstrated by separate modeling of 2015 watersheds over the Canadian landmass.

  14. Biomass burning in boreal forests and peatlands: Effects on ecosystem carbon losses and soil carbon stabilization as black carbon

    Science.gov (United States)

    Turetsky, M. R.; Kane, E. S.; Benscoter, B.

    2011-12-01

    Climate change has increased both annual area burned and the severity of biomass combustion in some boreal regions. For example, there has been a four-fold increase in late season fires in boreal Alaska over the last decade relative to the previous 50 years. Such changes in the fire regime are expected to stimulate ecosystem carbon losses through fuel combustion, reduced primary production, and increased decomposition. However, biomass burning also will influence the accumulation of black carbon in soils, which could promote long-term soil carbon sequestration. Variations in slope and aspect regulate soil temperatures and drainage conditions, and affect the development of permafrost and thick peat layers. Wet soil conditions in peatlands and permafrost forests often inhibit combustion during wildfires, leading to strong positive correlations between pre- and post- fire organic soil thickness that persist through multiple fire cycles. However, burning can occur in poorly drained ecosystems through smouldering combustion, which has implications for emission ratios of CO2:CH4:CO as well as black carbon formation. Our studies of combustion severity and black carbon concentrations in boreal soils show a negative relationship between concentrations of black carbon and organic carbon in soils post-fire. Relative to well drained stands, poorly drained sites with thick peat layers (such as north-facing stands) had less severe burning and low concentrations of black carbon in mineral soils post-fire. Conversely, drier forests lost a greater proportion of their organic soils during combustion but retained larger black carbon stocks following burning. Overall, we have quantified greater black carbon concentrations in surface mineral soil horizons than in organic soil horizons. This is surprising given that wildfires typically do not consume the entire organic soil layer in boreal forests, and could be indicative of the vulnerability of black carbon formed in organic horizons

  15. Calcium isotopic compositions as tracers of vegetation activity in boreal permafrost ecosystems (Kulingdakan watershed, Central Siberia)

    Science.gov (United States)

    Bagard, M.; Schmitt, A.; Chabaux, F. J.; Viers, J.; Pokrovsky, O. S.; Prokushkin, A. S.; Stille, P.; Dupré, B.

    2010-12-01

    In this work, we propose to investigate the geochemical potential of calcium isotopic fractionations in a forested boreal watershed to trace the impact of vegetation activity. This is the first study carried out in a geographical area characterized by deep and continuous permafrost. For this survey, we measured Ca and Sr isotopic compositions in the different compartments (stream waters, soil solutions, precipitations, rock, soils and soil leachates, vegetation) of a 4,100 ha Siberian watershed, the Kulingdakan watershed (Putorana Plateau, Central Siberia). Our results show that the activity of the vegetation is the only process that fractionates significantly calcium isotopes within the watershed. Indeed, Ca uptake by plants and its subsequent storage in larch tree organs favours 40Ca relatively to 44Ca. Vegetation decomposition releases light δ44/40Ca that affects calcium isotopic compositions of soil solution and soil exchangeable fractions. However, this biological impact is significant only for the South-facing slope of the watershed. Indeed, soil pools from the North-facing slope present no imprint of organic matter degradation in their δ44/40Ca signatures. Furthermore, the major difference between South- and North- facing slopes lies in the importance of the vegetation and its decomposition rate. Thus, we propose that in boreal permafrost areas with limited runoff, the available stock of biomass is critical to induce or not a significant vegetation impact on the calcium isotopic compositions in the soil-water system. As a consequence, the study of preserved calcium isotopic compositions in paleosoil exchangeable phases might bring relevant information on the evolution of biological activity at the watershed scale.

  16. Temporal Trends of Ecosystem Development on Different Site Types in Reclaimed Boreal Forests

    Directory of Open Access Journals (Sweden)

    Bradley D. Pinno

    2015-06-01

    Full Text Available Forest development after land reclamation in the oil sands mining region of northern Alberta, Canada was assessed using long-term monitoring plots from both reclaimed and natural forests. The metrics of ecosystem development analyzed included measures of plant community structure and composition and soil nutrient availability. Early seral reclamation plots were grouped by site type (dry and moist-rich and age categories, and these were compared with mature natural forests. There were few significant differences in ecosystem metrics between reclamation site types, but natural stands showed numerous significant differences between site types. Over time, there were significant changes in most plant community metrics such as species richness and cover of plant community groups (e.g., forbs, shrubs, and non-native species, but these were still substantially different from mature forests 20 years after reclamation. Available soil nitrogen did not change over time or by reclamation site type but available soil phosphorus did, suggesting that phosphorus may be a more suitable indicator of ecosystem development. The significant temporal changes in these reclaimed ecosystems indicate that studies of ecosystem establishment and development on reclaimed areas should be conducted over the long-term, emphasizing the utility of monitoring using long-term plot networks.

  17. Modelling carbon and water flows in terrestrial ecosystems in the boreal zone - examples from Oskarshamn

    Energy Technology Data Exchange (ETDEWEB)

    Karlberg, Louise [Stockholm Environment Institute (SEI), Stockholm (Sweden); Gu stafsson, David; Jansson, Per-Erik [Royal Inst. of Technology, Dept. of Land and Water Resources Engineering, Stockholm (Sweden)

    2007-12-15

    Carbon budgets and mean residence times were estimated in four hypothetical ecosystems. The greatest uncertainties in the estimations lie in the calculation of fluxes to and from the field layer. A parametrisation method based on multiple criteria, synthesising a wide range of empirical knowledge on ecosystem behaviour, proved to be useful both in the estimation of unknown parameters, to demonstrate model sensitivity, and to identify processes where our current knowledge is limited. The parameterizations derived from the study of the hypothetical systems were used to estimate site-specific carbon and water budgets for four ecosystems located within the Oskarshamn study-area. Measured soil respiration was used to calibrate the simulations. An analysis of the simulated carbon fluxes indicated that two of the ecosystems, namely the grassland and the spruce forest, were net sources of carbon dioxide, while the alder and the pine forest were net sinks of CO{sub 2}. In the former case, this was interpreted as a result of recent drainage of the organogenic soils and the concurrent increase in decomposition. The results from the study conformed rather well with results from a previous study on carbon budgets from the Oskarshamn study area.

  18. Extent and status of mires, peatlands, and organic soils in Europe

    Science.gov (United States)

    Tanneberger, Franziska; Barthelmes, Alexandra; Tegetmeyer, Cosima; Busse, Stephan; Joosten, Hans

    2016-04-01

    Key words: peatland distribution, peatland drainage, GIS, Global Peatland Database, European Mires Book The relevance of drained peatlands to climate change due to emission of huge amounts of greenhouse gases has recently been recognised e.g. by IPCC, FAO, and the European Union. Oppositely, natural and restored peatlands provide ecosystem services like enhancing biodiversity, nutrient retention, groundwater storage, flood mitigation, and cooling. To evaluate the drainage status of peatlands and organic soils and to develop specific restoration strategies comprehensive and exact geospatial data are needed. The Global Peatland Database (GPD) is hosted at Greifswald Mire Centre (http://tiny.cc/globalpeat). Currently, it provides estimates on location, extent, and drainage status of peatlands and organic soils for 268 countries and regions of the world. Due to the large diversity of definitions and terms for peatlands and organic soils, this mapping follows the broad definition of organic soils from IPCC that gives a minimum soil organic carbon threshold of 12% and considers any depth of the organic layer larger than 10 cm. GIS datasets are continuously collected, specific terms and definitions analysed and the completeness and accuracy of the datasets evaluated. Currently, the GPD contains geospatial data on peatlands and organic soils for all European countries (except Moldova). Recent information on status, distribution, and conservation of mires and peatlands in Europe is summarised in the European Mires Book. It includes descriptions from 49 countries and other geographic entities in Europe. All country chapters follow a generic structure and include also extensive descriptions of national terminology (also in national languages and script) and typologies as well as up to date area statistics and maps. They are complemented by integrative chapters presenting mire classification, mire regionality, peatland use, and mire conservation in Europe. The European Mires

  19. Stable carbon isotope fractionation during methanogenesis in three boreal peatland ecosystems

    Directory of Open Access Journals (Sweden)

    P. E. Galand

    2010-07-01

    Full Text Available The degradation of organic matter to CH4 and CO2 was investigated in three different boreal peatland systems in Finland, a mesotrophic fen (MES, an oligotrophic fen (OLI, and an ombrotrophic peat (OMB. MES had similar production rates of CO2 and CH4, but the two nutrient-poor peatlands (OLI and OMB produced in general more CO2 than CH4. δ13C analysis of CH4 and CO2 in the presence and absence methyl fluoride (CH3F, an inhibitor of acetoclastic methanogenesis, showed that CH4 was predominantly produced by hydrogenotrophic methanogenesis and that acetoclastic methanogenesis only played an important role in MES. These results, together with our observations concerning the collective inhibition of CH4 and CO2 production rates by CH3F, indicate that organic matter was degraded through different paths in the mesotrophic and the nutrient-poor peatlands. In the mesotrophic fen, the major process is canonical fermentation followed by acetoclastic and hydrogenotrophic methanogenesis, while in the nutrient-poor peat, organic matter was apparently degraded to a large extent by a different path which finally involved hydrogenotrophic methanogenesis. Our data suggest that degradation of organic substances in the oligotrophic environments was incomplete and involved the use of organic compounds as oxidants.

  20. Proceedings of a symposium on the reclamation and restoration of boreal peatland and forest ecosystems : towards a sustainable future

    Energy Technology Data Exchange (ETDEWEB)

    Bhatti, J. [Natural Resources Canada, Ottawa, ON (Canada); Foote, L.; Moran, S. [Alberta Univ., Edmonton, AB (Canada); Nadeau, L. [Northern Alberta Inst. of Technology, Edmonton, AB (Canada); Rochefort, L. [Laval Univ., Quebec City, PQ (Canada); Short, P. [Canadian Sphagnum Peat Moss Association, St. Albert, AB (Canada); Vitt, D.H. [Southern Illinois Univ., Carbondale, IL (United States); Wieder, K. [Villanova Univ., Villanova, PA (United States)] (comps.)

    2010-07-01

    Disturbances in Canada's boreal forest occur in both upland forests and in peatlands. These disturbances originate from both anthropogenic and natural causes, particularly fire. Techniques for the restoration, as well as the reclamation of peatlands and forests impacted by agriculture, urban development, or oil and gas activities, have made significant advancement over the last decade and these techniques need to be incorporated into the regulation and management of peatland and forest ecosystems. This symposium addressed the issue of how this research is affected by climate change. The sessions were entitled: (1) reclaiming forest and forest soils impacted by oil and gas production, (2) influence of oil sands development on forest communities, (3) understanding the importance of peatland and forest carbon in the twenty-first century, (4) reclaiming wetlands on mined oil sands tailing, (5) disturbance in peatlands and its relevance to minimizing disturbance footprints and informing reclamation efforts, and (6) restoration and management of harvested peatlands. The symposium featured 37 presentations, of which 6 have been catalogued separately for inclusion in this database. refs., tabs., figs.

  1. The resilience and functional role of moss in boreal and arctic ecosystems

    Science.gov (United States)

    Turetsky, M.; Bond-Lamberty, B.; Euskirchen, E.S.; Talbot, J. J.; Frolking, S.; McGuire, A.D.; Tuittila, E.S.

    2012-01-01

    Mosses in northern ecosystems are ubiquitous components of plant communities, and strongly influence nutrient, carbon and water cycling. We use literature review, synthesis and model simulations to explore the role of mosses in ecological stability and resilience. Moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories. Simulations from two process-based models suggest that northern ecosystems would need to experience extreme perturbation before mosses were eliminated. But simulations with two other models suggest that loss of moss will reduce soil carbon accumulation primarily by influencing decomposition rates and soil nitrogen availability. It seems clear that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species. We highlight several issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, and parameter vs conceptual uncertainty in models. Mosses play an important role in several ecosystem processes that play out over centuries – permafrost formation and thaw, peat accumulation, development of microtopography – and there is a need for studies that increase our understanding of slow, long-term dynamical processes.

  2. Effects of Conversion from Boreal Forest to Arctic Steppe on Soil Communities and Ecosystem Carbon Pools

    Science.gov (United States)

    Han, P. D.; Natali, S.; Schade, J. D.; Zimov, N.; Zimov, S. A.

    2014-12-01

    The end of the Pleistocene marked the extinction of a great variety of arctic megafauna, which, in part, led to the conversion of arctic grasslands to modern Siberian larch forest. This shift may have increased the vulnerability of permafrost to thawing because of changes driven by the vegetation shift; the higher albedo of grassland and low insulation of snow trampled by animals may have decreased soil temperatures and reduced ground thaw in the grassland ecosystem, resulting in protection of organic carbon in thawed soil and permafrost. To test these hypothesized impacts of arctic megafauna, we examined an experimental reintroduction of large mammals in northeast Siberia, initiated in 1988. Pleistocene Park now contains 23 horses, three musk ox, one bison, and several moose in addition to the native fauna. The park is 16 square km with a smaller enclosure (animals spend most of their time and our study was focused. We measured carbon-pools in forested sites (where scat surveys showed low animal use), and grassy sites (which showed higher use), within the park boundaries. We also measured thaw depth and documented the soil invertebrate communities in each ecosystem. There was a substantial difference in number of invertebrates per kg of organic soil between the forest (600 ± 250) and grassland (300 ± 250), though these differences were not statistically significant they suggest faster nutrient turnover in the forest or a greater proportion of decomposition by invertebrates than other decomposers. While thaw depth was deeper in the grassland (60 ± 4 cm) than in the forest (40 ± 6 cm), we did not detect differences in organic layer depth or percent organic matter between grassland and forest. However, soil in the grassland had higher bulk density, and higher carbon stocks in the organic and mineral soil layers. Although deeper thaw depth in the grassland suggests that more carbon is available to microbial decomposers, ongoing temperature monitoring will help

  3. Carbon dioxide emissions and nutrition on a drained pine mire - a case study

    Energy Technology Data Exchange (ETDEWEB)

    Hartman, M.; Karsisto, M.; Kaunisto, S. [Finnish Forest Research Inst., Vantaa (Finland). Vantaa Research Centre

    1996-12-31

    Drainage of boreal peatlands intensify aerobic decomposition and carbon dioxide emission from the peat substrate and increase tree growth. CO{sub 2} emission rates depend on the ground water level and the soil temperature. Predicted rises in mean air temperatures due to anthropogenically induced climate change are expected to further increase carbon dioxide emission from drained boreal peatlands. The role of added nutrients is somewhat vague. The purpose of this presentation is to give some preliminary results on microbial biomass carbon and on carbon dioxide output/input relationship on a pine mire. (6 refs.)

  4. Functional responses and resilience of boreal forest ecosystem after reduction of deer density.

    Directory of Open Access Journals (Sweden)

    Marianne Bachand

    Full Text Available The functional trait-based approach is increasingly used to predict responses of ecological communities to disturbances, but most studies target a single taxonomic group. Here, we assessed the resilience of a forest ecosystem to an overabundant herbivore population by assessing changes in 19 functional traits for plant, 13 traits for ground beetle and 16 traits for songbird communities after six years of controlled browsing on Anticosti Island (Quebec, Canada. Our results indicated that plants were more responsive to 6 years of reduced browsing pressure than ground beetles and songbirds. However, co-inertia analysis revealed that ground beetle communities responded in a similar way than plant communities with stronger relationships between plant and ground beetle traits at reduced deer density, a pattern not detected between plant and songbird. High deer density favored plants species that reproduce vegetatively and with abiotic pollination and seed dispersal, traits implying little interaction with animal. On the other hand, traits found at reduced deer density mostly involved trophic interaction. For example, plants in this treatment had fleshy fruits and large seeds dispersed by birds or other animals whereas ground beetle species were carnivorous. Overall, our results suggest that plant communities recovered some functional components to overabundant herbivore populations, since most traits associated with undisturbed forests were reestablished after six years of deer reduction. The re-establishment of functional plant communities with traits involving trophic interaction induces changes in the ground-beetle trait community, but forest structure remains likely insufficiently heterogeneous to shift the songbird trait community within six years.

  5. Functional responses and resilience of boreal forest ecosystem after reduction of deer density.

    Science.gov (United States)

    Bachand, Marianne; Pellerin, Stéphanie; Moretti, Marco; Aubin, Isabelle; Tremblay, Jean-Pierre; Côté, Steeve D; Poulin, Monique

    2014-01-01

    The functional trait-based approach is increasingly used to predict responses of ecological communities to disturbances, but most studies target a single taxonomic group. Here, we assessed the resilience of a forest ecosystem to an overabundant herbivore population by assessing changes in 19 functional traits for plant, 13 traits for ground beetle and 16 traits for songbird communities after six years of controlled browsing on Anticosti Island (Quebec, Canada). Our results indicated that plants were more responsive to 6 years of reduced browsing pressure than ground beetles and songbirds. However, co-inertia analysis revealed that ground beetle communities responded in a similar way than plant communities with stronger relationships between plant and ground beetle traits at reduced deer density, a pattern not detected between plant and songbird. High deer density favored plants species that reproduce vegetatively and with abiotic pollination and seed dispersal, traits implying little interaction with animal. On the other hand, traits found at reduced deer density mostly involved trophic interaction. For example, plants in this treatment had fleshy fruits and large seeds dispersed by birds or other animals whereas ground beetle species were carnivorous. Overall, our results suggest that plant communities recovered some functional components to overabundant herbivore populations, since most traits associated with undisturbed forests were reestablished after six years of deer reduction. The re-establishment of functional plant communities with traits involving trophic interaction induces changes in the ground-beetle trait community, but forest structure remains likely insufficiently heterogeneous to shift the songbird trait community within six years.

  6. Behaviour of {sup 137}Cs in the Boreal forest ecosystem of central Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Fawaris, B.H.

    1995-12-31

    Behaviour of Chernobyl fallout 1{sup 37}Cs in a coniferous forest ecosystem in central Sweden was investigated between 1990 and 1994. Results demonstrated that forest soil belongs to nutrient deficient type, and deposited fallout 1{sup 37}Cs from Chernobyl nuclear accident (CNA) was retained in the upper 5 cm of humic forest soil layer, with a venial migration deeper into soil profile. No correlation between forest soil exchangeable and total potassium (K{sup +}) and 1{sup 37}Cs transfer parameters was observed. However, addition of K{sup +}, found to efficiently reduce 1{sup 37}Cs uptake by sheep`s fescue and the addition of stable caesium (1{sup 33}Cs{sup +}) enhanced it. The addition of ammonium (NH{sub 4}{sup +}) was slightly stimulating the uptake of 1{sup 37}Cs by sheep`s fescue in the first cut only. Field plants showed a considerably reduction in their 1{sup 37}Cs activity concentrations. Relative to their 1{sup 37}Cs levels of 1986-89, a little reduction in heather occurred eight years after CNA. In contrast the reductions in lingonberry and bilberry were 87% and 68%, respectively. Three fractions of forest soil bound 1{sup 37}Cs were observed due to sequential extraction procedure (SEP). The first, is easily extractable 1{sup 37}Cs fraction, it comprises 22% of total forest soil 1{sup 37}Cs inventory in the upper 5 cm layer. The second, is soil organically and biologically bound 1{sup 37}Cs comprises about 30% of soil bound 1{sup 37}Cs. This fraction might be accounted for long-term soil available 1{sup 37}Cs for plant uptake after bio-degradation processes by soil microorganisms. The third, is the residual fraction, it comprises more than 35% of total forest soil 1{sup 37}Cs inventory, and may be associated with soil components which are probably of organic nature. Sorption of 1{sup 37}Cs by zeolite (Mordenite) revealed that soil bound 1{sup 37}Cs is to some extent more mobile in forest soils with high OM% and low pH than those with low OM%.

  7. Mires and mire types of Peninsula Mitre, Tierra del Fuego, Argentina

    NARCIS (Netherlands)

    Grootjans, A.; Iturraspe, R.; Fritz, C.; Moen, A.; Joosten, H.

    2014-01-01

    In 2007, a field visit by members of the International Mire Conservation Group (IMCG) to the Atlantic coast of Peninsula Mitre (the easternmost part of Isla Grande de Tierra del Fuego, Argentina) gathered information on mire diversity in this remote wild area with largely pristine mires. Our expedit

  8. Synchronous wildfire activity rise and mire deforestation at the triassic-jurassic boundary.

    Directory of Open Access Journals (Sweden)

    Henrik I Petersen

    Full Text Available The end-Triassic mass extinction event (∼201.4 million years ago caused major faunal and floral turnovers in both the marine and terrestrial realms. The biotic changes have been attributed to extreme greenhouse warming across the Triassic-Jurassic (T-J boundary caused by massive release of carbon dioxide and/or methane related to extensive volcanism in the Central Atlantic Magmatic Province (CAMP, resulting in a more humid climate with increased storminess and lightning activity. Lightning strikes are considered the primary source of wildfires, producing charcoal, microscopically recognized as inertinite macerals. The presence of polycyclic aromatic hydrocarbons (PAHs of pyrolytic origin and allochthonous charcoal in siliciclastic T-J boundary strata has suggested widespread wildfire activity at the time. We have investigated largely autochthonous coal and coaly beds across the T-J boundary in Sweden and Denmark. These beds consist of predominantly organic material from the in situ vegetation in the mires, and as the coaly beds represent a substantial period of time they are excellent environmental archives. We document a remarkable increase in inertinite content in the coal and coaly beds across the T-J boundary. We show estimated burning temperatures derived from inertinite reflectance measurements coupled with palynological data and conclude that pre-boundary late Rhaetian mire wildfires included high-temperature crown fires, whereas latest Rhaetian-Sinemurian mire wildfires were more frequent but dominated by lower temperature surface fires. Our results suggest a major change in the mire ecosystems across the T-J boundary from forested, conifer dominated mires to mires with a predominantly herbaceous and shrubby vegetation. Contrary to the overall regional vegetation for which onset of recovery commenced in the early Hettangian, the sensitive mire ecosystem remained affected during the Hettangian and did not start to recover until around

  9. Effect of industrial pollution on the distribution dynamics of radionuclides in boreal understorey ecosystems (EPORA). Final report

    Energy Technology Data Exchange (ETDEWEB)

    Suomela, M.; Rahola, T. [Radiation and Nuclear Safety Authority, Helsinki (Finland); Bergman, R. [National Defence Research Establishment (Sweden); Bunzl, K. [National Research Center for Environmental and Health (Germany); Jaakkola, T. [Helsinki Univ. (Finland). Radiochemical Lab.; Steinnes, E. [Norwegian University of Science and Technology (Norway)

    1999-08-01

    The project EPORA 'Effects of Industrial Pollution on Distribution Dynamics of Radionuclides in Boreal Understorey Ecosystems' is a part of the Nuclear Fission Safety Research programme of the European Union. A suitable environment for the study was found in the surroundings of the Cu-Ni smelter in Monchegorsk, in NW Russia where the huge atmospheric emissions from the smelter have polluted the environment since the 1930's. Samples of soil, litter, plants and runoff water were taken. Total concentrations of the mainpollutants, Ni and Cu, in the organic soil increased from about 10 mg kg{sup -1} at the reference site in Finland to about 5000 mg kg{sup -1} at the most polluted site in Russia. Similar trends were observed for exchangeable fractions and plant concentrations of the same elements. Concentrations of exchangeable K, Ca, and Mg in the organic soil decreased strongly with increased input of chemical pollutants. The radionuclides studied were {sup 137}Cs, {sup 90}Sr and {sup 239+240}Pu, mainly originating from the atmospheric nuclear weapons tests. The contribution of the Chernobyl derived {sup 137}Cs deposition was about 10% but insignificant for the other nuclides. The activity distribution of all three radionuclides in the soil, their corresponding residence half-times as well as their aggregated trencher factors for various plants depended on the degree of pollution: Activity distribution: in the litter layer, the activity of all three radionuclides increased continually from the reference site to the most polluted site. This effect was most pronounced for {sup 239+240}Pu and least for {sup 90}Sr and could, at least partly, be explained by the increase of the thickness of this layer. In the root zone, the opposite effect was observed: the largest fraction of all radionuclides was found at the reference site. In the organic layer, the exchangeable fractions of {sup 137}Cs, {sup 90}Sr and {sup 239+240}Pu decreased with increasing pollution

  10. Carbon exchange in Western Siberian watershed mires and implication for the greenhouse effect. A spatial temporal modeling approach

    Energy Technology Data Exchange (ETDEWEB)

    Borren, W.

    2007-01-19

    The vast watershed mires of Western Siberia formed a significant sink of carbon during the Holocene. Because of their large area these mires might play an important role in the carbon exchange between terrestrial ecosystems and the atmosphere. However, estimation of the Holocene and future carbon balance of whole Western Siberian mires is hampered by the lack of spatially resolved models. The main objective was to assess the carbon exchange fluxes of the mires using a 3-D dynamic approach. These exchange fluxes comprise the sequestration of carbon dioxide (CO2) by peat growth, the emission of methane (CH4) by anaerobic peat decay and the emission of CO2 by aerobic peat decay. From the detailed analysis of peat cores from different sites in the southern taiga of Western Siberia, it emerged that Holocene peat growth and carbon accumulation had different trends, caused by variations in vegetation succession. These differences were strongly influenced by the position in the landscape. Therefore, the effect of climatic change on mire development varied spatially. The indirect effects of climate change through local hydrology appeared to be more important than direct influences of changes in precipitation and temperature. Mire development is closely connected to hydrological dynamics. In the thesis a 3-D dynamic modeling approach is described that makes use of groundwater modeling. In successive timesteps peat growth and decay as well as mire type distribution were calculated, depending on hydrological conditions. The model was forced with a paleo-precipitation record to include variable climatic input. The model results show the Holocene development of a watershed mire from a few small spots to a contiguous mire landscape. As hydrology is the major limiting factor, the mire development is most sensitive to precipitation and evapotranspiration. Under unchanged conditions the mire will grow further, eventually reaching its maximum peat thickness around 11400 yr A.D. Under

  11. Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in the Yukon-Tanana Upland and Seward Peninsula, Alaska

    Science.gov (United States)

    Gough, L.P.; Crock, J.G.; Wang, B.; Day, W.C.; Eberl, D.D.; Sanzolone, R.F.; Lamothe, P.J.

    2008-01-01

    We report on soil development as a function of bedrock type and the presence of loess in two high latitude ecosystems (boreal forest and tundra) and from two regions in Alaska?the Yukon-Tanana Upland (YTU, east-central Alaska) and the Seward Peninsula (SP, far-west coastal Alaska). This approach to the study of 'cold soils' is fundamental to the quantification of regional geochemical landscape patterns. Of the five state factors in this study, bedrock and biota (ecosystem; vegetation zone) vary whereas climate (within each area) and topography are controlled. The influence of time is assumed to be controlled, as these soils are thousands of years old (late Quaternary to Holocene). The primary minerals in soils from YTU, developed over loess and crystalline bedrock (metamorphic and intrusive), are quartz, plagioclase, and 2:1 clays; whereas in the SP, where loess and metasedimentary bedrock (schist and quartzite) predominate, they are quartz and muscovite. The A horizon of both regions is rich in peat. Examination of the ratio of mobile (K2O, CaO, and Fe2O3) to immobile (TiO2) major oxides, within each region, shows that very little difference exists in the chemical weathering of soils developed between the two ecosystems examined. Differences were observed between tundra soils developed in the two regions. These differences are most probably due to the dissimilarity in the geochemical importance of both loess and bedrock. A minimal loss of cadmium with soil depth is seen for soils developed over YTU crystalline bedrock in the boreal forest environments. This trend is related to the mobility of cadmium in these soils as well as to its biogenic cycling. Major differences were observed in the proportion of cadmium and zinc among the A, B, and C horizon material sequestered in various soil fractions as measured by sequential soil extractions. These trends followed such variables as the decrease with depth in organic matter, the change in clay minerals, and the change

  12. Mercury cycling in boreal ecosystems: The long-term effect of acid rain constituents on peatland pore water methylmercury concentrations

    Science.gov (United States)

    Branfireun, Brian A.; Bishop, Kevin; Roulet, Nigel T.; Granberg, Gunnar; Nilsson, Mats

    Sulphate-reducing bacteria have been identified as primary methylators of mercury (Hg) in the laboratory and in field investigations. However, no studies have investigated the effect of long-term deposition of sulphate on methylmercury (MeHg) dynamics in peatlands, which are known to be significant sources of MeHg to downstream waters in the boreal forest zone. As an ancillary experiment to a larger project investigating the effects of acid rain constituents on peatland carbon dynamics, the influence of experimentally elevated Na2SO4 and/or NH4NO3 deposition on peat pore water MeHg concentrations was determined using a simple mesocosm experimental design. After three years, additions of S in amounts equivalent to the 1980s dry and wet deposition in Southern Sweden resulted in peat pore water MeHg concentrations up to six times above background levels. Elevated N loads had no effect on pore water MeHg concentrations.

  13. The response of mire vegetation to water level drawdown

    Science.gov (United States)

    Kurki, Kirsi; Laine, Jukka; Vasander, Harri; Tuittila, Eeva-Stiina

    2010-05-01

    Mires have a significant role in climate change mitigation due to their enormous carbon storage and due to the fluxes of greenhouse gases between ecosystem and the atmosphere. Mire vegetation is controlled by ecohydrology, climate and by the competition of plants on light and nutrients. The water logged conditions create a challenging environment for both vascular plants and bryophytes; therefore majority of plants growing in these habitats are highly specialized. Global warming is predicted to affect mire vegetation indirectly through increased evapotranspiration leading to decreased water table levels down to 14-22 centimeters. Water level drawdown is likely to affect the vegetation composition and consequently the ecosystem functioning of mires. Previous studies covering the first years following water table level drawdown have shown that vascular plants benefit from a lower water table and hollow-specific Sphagnum species suffer. In addition to changes in plant abundances the diversity of plant communities decreases. The lawn and hollow communities of Sphagna and sedges are found to be the most sensitive plant groups. It has been shown that surveys on vegetation changes can have different results depending on the time scale. The short and long term responses are likely vary in heterogenous mire vegetation; therefore predictions can be done more reliably with longer surveys. We applied BACI (before-after-control-impact) experimental approach to study the responses of different functional mire plant groups to water level drawdown. There are 3 control plots, 3 treatment plots with moderate water level drawdown and 3 plots drained for forestry 40 years ago as a reference. The plots are located in meso-, oligo- and ombrotrophic sites in Lakkasuo (Orivesi, Finland). The vegetation was surveyed from permanent sampling points before ditching in 2000 and during the years 2001-2003 and 2009. The data was analyzed with NMDS (PC-Ord) and DCA (CANOCO). Overall results show

  14. Dynamical vegetation-atmosphere modelling of the boreal zone

    Science.gov (United States)

    Tang, Hui; Stordal, Frode; Berntsen, Terje K.; Bryn, Anders

    2016-04-01

    Vegetation interacts with climate on seasonal to inter-annual time scales through albedo, roughness, evapotranspiration, CO2 sequestration and by influencing snow accumulation and ablation. The Scandinavian mountains and high latitudes is a hot spot for land-atmosphere feedback, as the future's increased winter minimum temperature supports a boreal tree line advance, lowering the surface albedo. The northern ecosystem is dominated by mires, boreal forests and alpine heaths, in addition to agricultural land. Model studies have shown that vegetation-climate feedbacks are strong enough to lead to regime shifts in vegetation and local climate in boreal regions. Biogeophysical factors, such as albedo, the Bowen ratio, and surface roughness, are all involved in these feedbacks, and they are also altered by land use change such as reforestation. For calculations of the dynamical coupling between the atmosphere and the vegetation we have used the Earth System Model NorESM, which includes several advanced features in its land surface model (CLM4.5), such as the inclusion of the radiative forcing due to black carbon and dust deposit onto snow, improved representation of fire, permafrost and its hydrological impact, a new snow cover fraction parameterization reflecting the hysteresis in fractional snow cover for a given snow depth between accumulation and melt phases, as well as dynamic vegetation coupled with carbon-nitrogen cycles. These new features improve the representation of surface albedo feedback in Arctic. We have performed experiments with coupled as well fixed ocean for the current as a quadrupled atmospheric CO2 situation. This model configuration is used to study changes in vegetation in a high end radiative forcing case. It is contrasted with an experiment where vegetation dynamics is neglected. Changes in the features of the vegetation along with surface fluxes, albedo and atmospheric temperatures are analysed, with main emphasis on the boreal zone. In

  15. Differential response of bird functional traits to post-fire salvage logging in a boreal forest ecosystem

    Science.gov (United States)

    Azeria, Ermias T.; Ibarzabal, Jacques; Hébert, Christian; Boucher, Jonathan; Imbeau, Louis; Savard, Jean-Pierre L.

    2011-05-01

    The concept of functional trait-environment relationship posits that species in a local community should possess similar traits that match the selective environment. The present study examines species trait-habitat (using Fourth-corner and RLQ analyses) and habitat occupancy patterns (logistic regression models) of bird assemblages in boreal forest stands following disturbances by forest fire and salvage logging. The stands differed in the amount and composition of residual tree retention, salvage- and aquatic-edges, degree of burn severity (all measured at 100 and 500 m buffers), as well as landscape-level variables such as distance to previously burned forests. Tests of trait-habitat relationships showed that canopy-nesters and bark- and foliage- insectivores required high levels of residual trees of low burn severity, with the feeding guilds showing affinity for different stand composition. In contrast, ground-nesters and omnivores thrived in salvaged areas and associated edges. In addition, cavity-nesting and ground-foragers were associated with severely burned stands. The species' habitat occupancy patterns were commensurate with trait requirements, which also appeared to be scale-dependent. For example, some fire-associated species had high occupancy probability in severely burned stands at small-scale (100 m buffer), which was consistent with their cavity-nesting trait. This pattern, however, was not evident at large-scale, where their feeding requirement (bark-insectivores) for low-severity burns dominated. Our study suggests that trait-habitat relationships can provide critical information to the complex ways species' relate to key habitat factors following natural and anthropogenic disturbances.

  16. Non-methane volatile organic compound flux from a subarctic mire in Northern Sweden

    Science.gov (United States)

    Bäckstrand, Kristina; Crill, Patrick M.; Mastepanov, Mikhail; Christensen, Torben R.; Bastviken, David

    2008-04-01

    Biogenic NMVOCs are mainly formed by plants and microorganisms. They have strong impact on the local atmospheric chemistry when emitted to the atmosphere. The objective of this study was to determine if there are significant emissions of non-methane volatile organic compounds (NMVOCs) from a subarctic mire in northern Sweden. Subarctic peatlands in discontinuous permafrost regions are undergoing substantial environmental changes due to their high sensitivity to climate warming and there is need for including NMVOCs in the overall carbon budget. Automatic and manual chamber measurements were used to estimate NMVOC fluxes from three dominating subhabitats on the mire during three growing seasons. Emission rates varied and were related to plant species distribution and seasonal net ecosystem exchange of carbon dioxide. The highest fluxes were observed from wetter sites dominated by Eriophorum and Sphagnum spp. Total NMVOC emissions from the mire (~17 ha) is estimated to consist of ~150 kgC during a growing season with 150 d. NMVOC fluxes can account for ~5% of total net carbon exchange (-3177 kgC) at the mire during the same period. NMVOC emissions are therefore a significant component in a local carbon budget for peatlands.

  17. Wind farms and mires in the Basque Country and north-west Navarra, Spain

    Directory of Open Access Journals (Sweden)

    P. Heras

    2008-07-01

    Full Text Available Mires occur in the Basque Country and north-west Navarra (northern Spain due to the Atlantic influence on climate. They are most frequent in the north and become rarer to the south. True peatland is found at only six locations, but there are also some para-peaty habitats associated with springs and flushes which have very thin discontinuous peat layers. Although small, this mire territory straddles the boundary between two separate autonomous communities where different regulations and management guidelines apply. Both communities have developed extensive plans to exploit wind energy, and the summit ridges of many of the mountain ranges now carry long strings of turbines. Consequences for the Basque and Navarran mire ecosystems are reviewed. Because little is known about these habitats, they went largely unnoticed during the process of wind farm planning and were thus exposed to enormous risk. Nonetheless, the impacts of development so far have been limited by careful practice combined with the fact that the locations of most of the mires do not coincide exactly with the favoured locations for wind turbines. The only blanket bog is situated in the Zalama area, where plans to build a wind farm have been abandoned for a combination of reasons. Paradoxically, the wind farm planning process was instrumental in raising social and political awareness of this important peatland, leading to a very promising level of interest in its conservation and restoration amongst local institutions.

  18. Modeling nonlinear responses of DOC transport in boreal catchments in Sweden

    Science.gov (United States)

    Kasurinen, Ville; Alfredsen, Knut; Ojala, Anne; Pumpanen, Jukka; Weyhenmeyer, Gesa A.; Futter, Martyn N.; Laudon, Hjalmar; Berninger, Frank

    2016-07-01

    Stream water dissolved organic carbon (DOC) concentrations display high spatial and temporal variation in boreal catchments. Understanding and predicting these patterns is a challenge with great implications for water quality projections and carbon balance estimates. Although several biogeochemical models have been used to estimate stream water DOC dynamics, model biases common during both rain and snow melt-driven events. The parsimonious DOC-model, K-DOC, with 10 calibrated parameters, uses a nonlinear discharge and catchment water storage relationship including soil temperature dependencies of DOC release and consumption. K-DOC was used to estimate the stream water DOC concentrations over 5 years for eighteen nested boreal catchments having total area of 68 km2 (varying from 0.04 to 67.9 km2). The model successfully simulated DOC concentrations during base flow conditions, as well as, hydrological events in catchments dominated by organic and mineral soils reaching NSEs from 0.46 to 0.76. Our semimechanistic model was parsimonious enough to have all parameters estimated using statistical methods. We did not find any clear differences between forest and mire-dominated catchments that could be explained by soil type or tree species composition. However, parameters controlling slow release and consumption of DOC from soil water behaved differently for small headwater catchments (less than 2 km2) than for those that integrate larger areas of different ecosystem types (10-68 km2). Our results emphasize that it is important to account for nonlinear dependencies of both, soil temperature, and catchment water storage, when simulating DOC dynamics of boreal catchments.

  19. Modeling forest development after fire disturbance: Climate, soil organic layer, and nitrogen jointly affect forest canopy species and long-term ecosystem carbon accumulation in the North American boreal forest

    Science.gov (United States)

    Trugman, A. T.; Fenton, N.; Bergeron, Y.; Xu, X.; Welp, L.; Medvigy, D.

    2015-12-01

    Soil organic layer dynamics strongly affect boreal forest development after fire. Field studies show that soil organic layer thickness exerts a species-specific control on propagule establishment in the North American boreal forest. On organic soils thicker than a few centimeters, all propagules are less able to recruit, but broadleaf trees recruit less effectively than needleleaf trees. In turn, forest growth controls organic layer accumulation through modulating litter input and litter quality. These dynamics have not been fully incorporated into models, but may be essential for accurate projections of ecosystem carbon storage. Here, we develop a data-constrained model for understanding boreal forest development after fire. We update the ED2 model to include new aspen and black spruce species-types, species-specific propagule survivorship dependent on soil organic layer depth, species-specific litter decay rates, dynamically accumulating moss and soil organic layers, and nitrogen fixation by cyanobacteria associated with moss. The model is validated against diverse observations ranging from monthly to centennial timescales and spanning a climate gradient in Alaska, central Canada, and Quebec. We then quantify differences in forest development that result from changes in organic layer accumulation, temperature, and nitrogen. We find that (1) the model accurately reproduces a range of observations throughout the North American boreal forest; (2) the presence of a thick organic layer results in decreased decomposition and decreased aboveground productivity, effects that can increase or decrease ecosystem carbon uptake depending on location-specific attributes; (3) with a mean warming of 4°C, some forests switch from undergoing succession to needleleaf forests to recruiting multiple cohorts of broadleaf trees, decreasing ecosystem accumulation by ~30% after 300 years; (4) the availability of nitrogen regulates successional dynamics such than broadleaf species are

  20. Mapping of mires in Switzerland - starting point and results

    Energy Technology Data Exchange (ETDEWEB)

    Kuettel, M. [Federal Office of Environment, Forests and Landscape, Bern (Switzerland)

    1996-12-31

    Modern mapping of Swiss mires aims at nature conservation and is based on a phyto-ecological approach to mire definition, which recognizes certain plant associations as being mire vegetation. In particular, apart from societies of raised bogs (Oxycocco-Sphagnetea) and transitional bogs (Scheuchzerietalia palustris), the Phragmition, Magnocaricion, Coercion Norse, Caricion davallianae as well as Molinion and Filipendulion/ Calthion alliances also form part of mire vegetation, regardless of the presence of a peat layer or its thickness. Mires in Switzerland are, therefore, primarily wetlands. Accordingly approximately 14.70 km{sup 2} of raised and transitional bogs (only 1/3 in a primary stage) and approximately 184.70 km{sup 2} of fens of national importance have been mapped and placed under protection. Total mire area has been estimated to be about 224.10 km{sup 2}. (orig.) (8 refs.)

  1. 北方森林生态系统对全球气候变化的响应研究进展%Response of boreal forest ecosystem to global climate change:a review

    Institute of Scientific and Technical Information of China (English)

    韩士杰; 王庆贵

    2016-01-01

    北方森林是地球上第2大生物群区,约占陆地森林面积的30%,提供了从局地到全球的生态系统服务功能。1850年以来,全球性持续升温不断显现,2000—2050年全球至少升高2℃,甚至更高。预计到2100年,北方森林区冬季平均温度将升高1.3~6.3℃。与此同时,几乎所有的北方森林生态系统功能都将会受到影响,尤其是近几十年来,该区域发生了很多与温度升高相关的潜在生态响应。本文从碳循环、生物多样性、干旱化和林火发生频率以及冻土变化等方面具体综述了北方森林生态系统对于全球气候变化的响应。响应结果如下:1)气候变化对于北方森林碳循环动态的影响是极其复杂的,迄今为止并没有达成共识;分解对于温度的反应敏感程度至今仍存在很多不确定性。2)动物、植物和微生物(真菌)均对气候变化产生了一定的响应,表现为动物和植物的分布区进一步北移,但真菌的多样性和生产力响应机制尚无法确定。3)北方森林区随气候变化表现为进一步的干旱化和林火发生明显增加。4)北方森林区与冻土伴生,冻土随气候变暖表现出了面积缩小和活动层扩大的趋势。可见,北方森林对气候变化响应明显,尽管到目前为止有些响应机制尚不清楚,但变化趋势十分明显。本文旨在为北方森林的经营和管理提供基础数据和技术支持,实现北方森林的可持续经营。%The boreal forest, one of the largest biomes on the Earth, encompasses ~30% of the global forest area and provides ecosystem services that benefit society at levels ranging from local to global. Warming since the 1850s increases the annual mean temperature from 2000 to 2050 at least 2 ℃ or even more. Annual winter mean temperatures across the boreal zone could be 1. 3-6. 3℃ warmer than today' s by 2100. In the meantime, all aspects of boreal forest ecosystem function are likely to be

  2. Landscape control of uranium and thorium in boreal streams – spatiotemporal variability and the role of wetlands

    Directory of Open Access Journals (Sweden)

    H. Laudon

    2012-03-01

    Full Text Available The concentrations of uranium and thorium in ten partly nested streams in the boreal forest region were monitored over a two-year period. Considerable spatiotemporal variations were observed, with little or no correlation between streams. The export of both uranium and thorium varied substantially between the subcatchments, ranging from 1.7 to 30 g km−2 a−1 for uranium and from 3.2 to 24 g km−2 a−1 for thorium. Airborne gamma spectrometry was used to measure the concentrations of uranium and thorium in surface soils throughout the catchment, but could not explain the variability in the export. Instead, the extent of lakes and mires within each subcatchment was found to be a stronger predictor for the transport of uranium and thorium. The results indicate that there is a predictable and systematic accumulation of both uranium and thorium in boreal mires. Approximately 65–80 % of uranium and 55–65 % of thorium entering a mire is estimated to be retained in the peat. Overall, accumulation in mires and other types of wetlands is estimated to decrease the fluxes of uranium and thorium from the boreal forest landscape by 30–40 %. The atmospheric deposition of uranium and thorium was also quantified and its contribution to boreal streams was found to be low compared to weathering.

  3. The boreal forest as a cultural landscape.

    Science.gov (United States)

    Johnson, Edward A; Miyanishi, Kiyoko

    2012-02-01

    Because of its generally low density of humans and few settlements, the circumpolar boreal forest is often viewed as an untouched wilderness. However, archeological evidence indicates that humans have inhabited the region since the continental glaciers disappeared 8,000-12,000 years ago. This paper discusses the ecological impacts that humans have had on the boreal forest ecosystem through their activities in prehistoric, historic, and recent times and argues that the boreal forest has always been a cultural landscape with a gradient of impacts both spatially and temporally. These activities include hunting, trapping, herding, agriculture, forestry, hydroelectric dam projects, oil and natural gas development, and mining. In prehistoric times, human impacts would generally have been more temporary and spatially localized. However, the megafaunal extinctions coincident with arrival of humans were very significant ecological impacts. In historic times, the spread of Europeans and their exploitation of the boreal's natural resources as well as agricultural expansion has altered the composition and continuity of the boreal forest ecosystem in North America, Fennoscandia, and Asia. Particularly over the last century, these impacts have increased significantly (e.g., some hydroelectric dams and tar sands developments that have altered and destroyed vast areas of the boreal forest). Although the atmospheric changes and resulting climatic changes due to human activities are causing the most significant changes to the high-latitude boreal forest ecosystem, any discussion of these impacts are beyond the limits of this paper and therefore are not included.

  4. Modelling wetland-groundwater interactions in the boreal Kälväsvaara esker, Northern Finland

    Science.gov (United States)

    Jaros, Anna; Rossi, Pekka; Ronkanen, Anna-Kaisa; Kløve, Bjørn

    2016-04-01

    Many types of boreal peatland ecosystems such as alkaline fens, aapa mires and Fennoscandia spring fens rely on the presence of groundwater. In these ecosystems groundwater creates unique conditions for flora and fauna by providing water, nutrients and constant water temperature enriching local biodiversity. The groundwater-peatland interactions and their dynamics are not, however, in many cases fully understood and their measurement and quantification is difficult due to highly heterogeneous structure of peatlands and large spatial extend of these ecosystems. Understanding of these interactions and their changes due to anthropogenic impact on groundwater resources would benefit the protection of the groundwater dependent peatlands. The groundwater-peatland interactions were investigated using the fully-integrated physically-based groundwater-surface water code HydroGeoSphere in a case study of the Kälväsvaara esker aquifer, Northern Finland. The Kälväsvaara is a geologically complex esker and it is surrounded by vast aapa mire system including alkaline and springs fens. In addition, numerous small springs occur in the discharge zone of the esker. In order to quantify groundwater-peatland interactions a simple steady-state model was built and results were evaluated using expected trends and field measurements. The employed model reproduced relatively well spatially distributed hydrological variables such as soil water content, water depths and groundwater-surface water exchange fluxes within the wetland and esker areas. The wetlands emerged in simulations as a result of geological and topographical conditions. They could be identified by high saturation levels at ground surface and by presence of shallow ponded water over some areas. The model outputs exhibited also strong surface water-groundwater interactions in some parts of the aapa system. These areas were noted to be regions of substantial diffusive groundwater discharge by the earlier studies. In

  5. Boreal forests can have a remarkable role in reducing greenhouse gas emissions locally: Land use-related and anthropogenic greenhouse gas emissions and sinks at the municipal level

    Energy Technology Data Exchange (ETDEWEB)

    Vanhala, Pekka, E-mail: pekka.vanhala@ymparisto.fi [Finnish Environment Institute, Natural Environment Centre, P.O. Box 140, Mechelininkatu 34 a, FI-00251 Helsinki (Finland); Bergström, Irina [Finnish Environment Institute, Natural Environment Centre, P.O. Box 140, Mechelininkatu 34 a, FI-00251 Helsinki (Finland); Haaspuro, Tiina [University of Helsinki, Department of Environmental Sciences, P.O. Box 65, Viikinkaari 1, 00014 Helsinki (Finland); Kortelainen, Pirkko; Holmberg, Maria; Forsius, Martin [Finnish Environment Institute, Natural Environment Centre, P.O. Box 140, Mechelininkatu 34 a, FI-00251 Helsinki (Finland)

    2016-07-01

    Ecosystem services have become an important concept in policy-making. Carbon (C) sequestration into ecosystems is a significant ecosystem service, whereas C losses can be considered as an ecosystem disservice. Municipalities are in a position to make decisions that affect local emissions and therefore are important when considering greenhouse gas (GHG) mitigation. Integrated estimations of fluxes at a regional level help local authorities to develop land use policies for minimising GHG emissions and maximising C sinks. In this study, the Finnish national GHG accounting system is modified and applied at the municipal level by combining emissions and sinks from agricultural land, forest areas, water bodies and mires (land use-related GHG emissions) with emissions from activities such as energy production and traffic (anthropogenic GHG emissions) into the LUONNIKAS calculation tool. The study area consists of 14 municipalities within the Vanajavesi catchment area located in Southern Finland. In these municipalities, croplands, peat extraction sites, water bodies and undrained mires are emission sources, whereas forests are large carbon sinks that turn the land use-related GHG budget negative, resulting in C sequestration into the ecosystem. The annual land use-related sink in the study area was 78 t CO{sub 2} eq km{sup −2} and 2.8 t CO{sub 2} eq per capita. Annual anthropogenic GHG emissions from the area amounted to 250 t CO{sub 2} eq km{sup −2} and 9.2 t CO{sub 2} eq per capita. Since forests are a significant carbon sink and the efficiency of this sink is heavily affected by forest management practices, forest management policy is a key contributing factor for mitigating municipal GHG emissions. - Highlights: • The significance of natural landscapes in the regional C budgets is shown. • Boreal forests can be remarkable C sinks enabling net C sequestration in ecosystems. • The large area of forest may compensate for all C emissions in the municipality.

  6. Seasonality in a boreal forest ecosystem affects the use of soil temperature and moisture as predictors of soil CO2 efflux

    Directory of Open Access Journals (Sweden)

    S. Kellomäki

    2011-03-01

    Full Text Available Our objectives were to identify factors related to temporal variation of soil CO2 efflux in a boreal pine forest and to evaluate simple predictive models of temporal variation of soil CO2 efflux. Soil CO2 efflux was measured with a portable chamber in a Finnish Scots pine forest for three years, with a fourth year for model evaluation. Plot averages for soil CO2 efflux ranged from 0.04 to 0.90 g CO2 m−2 h−1 during the snow-free period, i.e. May–October, and from 0.04 to 0.13 g CO2 m−2 h−1 in winter. Soil temperature was a good predictor of soil CO2 efflux. A quadratic model of ln-transformed efflux explained 76–82% of the variation over the snow-free period. The results revealed strong seasonality: at a given soil temperature, soil CO2 efflux was higher later in the snow-free period than in spring and early summer. Regression coefficients for temperature (approximations of a Q10 value of month-specific models decreased with increasing average soil temperatures. Efflux in July, the month of peak photosynthesis, showed no clear response to temperature or moisture. Inclusion of a seasonality index, degree days, improved the accuracy of temperature response models to predict efflux for the fourth year of measurements, which was not used in building of regression models. Underestimation during peak efflux (mid-July to late-August remained uncorrected. The strong influence of the flux of photosynthates belowground and the importance of root respiration could explain the relative temperature insensitivity observed in July and together with seasonality of growth of root and root-associated mycorrhizal fungi could explain partial failure of models to predict magnitude of efflux in the peak season from mid-July to August. The effect of moisture early in the season was confounded by simultaneous advancement of the growing season and increase in temperature. In a dry year, however, the effect of drought was evident as soil CO2 efflux was some 30

  7. VEGETATION AND HYDROLOGY IN A SPRING MIRE COMPLEX IN WESTERN POMERANIA, POLAND

    NARCIS (Netherlands)

    WOLEJKO, L; AGGENBACH, C; VANDIGGELEN, R; GROOTJANS, AP

    1994-01-01

    The vegetation of one of the largest spring mires in Poland has been studied with special regard to hydrological conditions and stratigraphic development of the mire. Despite its biotic richness the mire is in a slow state of deterioration, initiated by man several hundred years ago. Evidence has be

  8. Characterization of Vegetation Change in a Sub-Arctic Mire using Remotely Sensed Imagery

    Science.gov (United States)

    DelGreco, J. L.; McArthur, K. J.; Palace, M. W.; Herrick, C.; Garnello, A.; Finnell, D.; McCalley, C. K.; Anderson, S. M.; Varner, R. K.

    2015-12-01

    Climate change is impacting northern ecosystems through the thawing of the permafrost, which has resulted in changes to plant communities and greenhouse gas emissions, such as carbon dioxide (CO2) and methane (CH4). These greenhouse gases are of concern due to their potential feedbacks which create a warmer climate, thus increasing permafrost thawing. Our study focuses on how vegetation type differs in areas that have been impacted by thawing permafrost at Stordalen Mire located in Abisko, Sweden. To estimate change in vegetation communities, field-based measurements combined with remotely sensed image data was used. 75 randomized square-meter plots were measured for vegetation composition and classified into one of five site-types, each representing a different stage of permafrost degradation. New high-resolution imagery (1 cm) was collected using Unmanned Aerial Vehicles (UAV) providing insight into the spatial patterning, characterizations, and changes of these communities. The UAV imagery was georectified using high precision GPS points collected across the mire. The imagery was then examined using a neural network analysis to estimate cover type across the mire. This 2015 cover type classification was then compared to previous UAV imagery taken on July 2014 to analyze changes in vegetation distribution as an indication of permafrost thaw. Hummock sites represent intact permafrost and have lost 21.5% coverage since 2014, while tall gramminoid sites, which indicate fully thawed sites, have increased coverage by 12.1%. A discriminate function analysis showed that site types can be differentiated based on species composition, thus showing that vegetation differs significantly across the thaw gradient. Using average flux rates of CH4 from each cover type reported previously, the percent of CH4 emitted over the mire was estimated for 2014 and 2015. Comparing both estimates, CH4 emissions increased with a flux change of 5604.5 g CH4/day. Our estimates of vegetation

  9. Age of vegetation simulated by Boreal ALFRESCO for the state of Alaska. Dataset generated in 2010. NAD83, Alaska Albers projection, http://spatialreference.org/ref/epsg/3338/

    Data.gov (United States)

    Arctic Landscape Conservation Cooperative — These rasters represent output from the Boreal ALFRESCO (Alaska Frame Based Ecosystem Code) model. Boreal ALFRESCO operates on an annual time step, in a landscape...

  10. Application of a UV-Vis submersible probe for capturing changes in DOC concentrations across a mire complex during the snowmelt and summer periods

    Science.gov (United States)

    Avagyan, Armine; Runkle, Benjamin; Kutzbach, Lars

    2013-04-01

    An accurate quantification of dissolved organic carbon (DOC) is crucial for understanding changes in water resources under the influence of climate, land use and urbanization. However, the conventionally used methods do not allow high frequency in situ analyses in remote or hostile environments (e.g., industrial wastewater or during environmental high-flow events, such as snowmelt or floods). In particular, missing measurements during the snowmelt period in landscapes of the boreal region can lead to significant miscalculations in regional carbon budgets. Therefore, the aim of the study was to test the performance of a portable, submersible UV-Vis spectrophotometer (spectro::lyser, s::can Messtechnik GmbH, Austria) during the snowmelt period in a boreal mire-forest catchment, and to provide a conceptual understanding of the spatial and temporal dynamics of DOC concentrations during and after snowmelt. During 2011, water samples were collected from the near-pristine Ust-Pojeg mire complex in northwestern Russia (61° 56'N, 50° 13'E). Sampling started during the spring snowmelt period and continued until late fall. The mire presented a mosaic of different landscape units. The mire consisted of minerogeous (fen), ombrogenous (bog), and transitional forest-mire (lagg) zones. Water samples were taken from the surface across the mire (22 points at 50-m intervals). DOC concentrations were analyzed directly at the study site using a portable, submersible UV-Vis spectrophotometer, which uses high-resolution absorbance measurements over the wavelength range 200-742.5 nm at 2.5-nm intervals as a proxy for DOC content. Because the DOC composition of fluids varies by site, a local calibration replaced the default settings of the spectro::lyser (Global Calibration) to enhance the accuracy of the measurements. To evaluate the local calibration and correct for drift, the same samples (n = 157) were additionally analyzed using the wet persulfate oxidation method (O

  11. Carbon storage change in a partially forestry-drained boreal mire determined through peat column inventories

    Energy Technology Data Exchange (ETDEWEB)

    Pitkanen, A.; Tahvanainen, T.; Simola, H. [Univ. of Eastern Finland, Joensuu (Finland). Dept. pf Biology; Turunen, J. [Geological Survey of Finland, Kuopio (Finland)

    2013-09-01

    To study the impact of forestry drainage on peat carbon storage, we cored paired quantitative peat samples from undrained and drained sides of an eccentric bog. Five pairs of 0 to {<=} 100-cm-deep surface-peat cores, and a pair of profiles representing the full peat deposit provided stratigraphic evidence of marked loss of surface peat due to drainage. For the drained side cores, we found a relative subsidence of 25-37 cm of the surface, and a loss of about 10 kg{sub DW}{sup m-2}, corresponding to 131 {+-} 28 g C m{sup -2} a{sup -1} (mean {+-} SE) for the post-drainage period. Similar peat loss was also found in the full deposit profiles, thus lending credibility to the whole-column inventory approach, even though the decrease (9 kg{sub DW} m{sup -2}) was relatively small in comparison with the total carbon storage (233 and 224 kg{sub DW} m{sup -2} for the undrained and drained sides, respectively). (orig.)

  12. Armillaria ectypa, a rare fungus of mire in Poland

    Directory of Open Access Journals (Sweden)

    Małgorzata Stasińska

    2015-08-01

    Full Text Available Armillaria ectypa is a saprotroph that occurs on active raised bogs and alkaline fens, as well as Aapa mires and transitional bogs. It is a very rare and threatened Eurasian species and one of the 33 fungal species proposed for inclusion into the Bern Convention. Its distribution in Poland, ecological notes and morphology of basidiocarp based on Polish specimens are presented.

  13. Hydroclimatic shifts recorded in peat archive from Rąbień mire (Central Poland) - better understanding of past climate changes using multidisciplinary approach

    Science.gov (United States)

    Słowiński, Michał; Marcisz, Katarzyna; Płóciennik, Mateusz; Obremska, Milena; Pawłowski, Dominik; Okupny, Daniel; Słowińska, Sandra; Borówka, Ryszard; Kittel, Piotr; Forysiak, Jacek; Michczyńska, Danuta J.; Lamentowicz, Mariusz

    2016-04-01

    Hydrological changes are main drivers of the processes occurring in the peatland ecosystem, e.g. organic matter accumulation and decomposition. Hydroclimatic changes in mires are caused by various non-climatic factors, such as hydroseral succession or land use changes. Central Europe, namely Poland, is characterized by a transitional climate with influence o both continental and Atlantic air masses, which makes a this region a very sensitive to climate change. Here we explore a potential of multidisciplinary approach in reconstruction of past climate change and particularly hydroclimatic conditions which control in Sphagnum peatland ecosystem. We reconstructed 3300 years (between 3,500 BC and 200 BC) history of development of Rąbień mire using several biotic proxies (pollen, plant macrofossils, testate amoebae, Cladocera, Chironomidae) and geochemistry. Study site - Rąbień mire (area 42 ha) is located in central Poland and it is protected nature reserve. The origin of the mire depression is connected with the development of the thermokarst basin isolated by dunes. Rąbień mire is limnogenic, i.e. formed by the process of terrestrialisation of a water body and thickness of biogenic deposits is 6.2 m (440 cm of lacustrine sediment and 180 cm of peat). Our results demonstrate the high potential of Rąbień peat record for reconstructing the palaeohydrological dynamics. The studied time interval is characterized by two pronounced dry periods: ~2,500 to ~1,700 cal. BC and ~800 to ~600 cal. BC, and two periods of significant increases in water table: ~1,100 to ~800 cal. BC and ~600 to ~250 cal. BC. The timing of the wet shift at 600 cal. BC corresponds to wet periods in different sites from Central and Eastern Europe. Our investigation reveals a complex pattern of proxies, what might be linked to the past atmospheric circulation patterns. Extreme hydroclimatic conditions most possibly had a direct impact on the functioning of peatland ecosystems. What has been

  14. A quantication of photoproduction of CO2 throughout the water column by degradation of terrigenous organic compounds present in the dissolved form for aquatic ecosystems of the boreal region in Quebec

    Science.gov (United States)

    Plouhinec, J.; Lucotte, M. M.; Ouellet, A.; Gelinas, Y.

    2010-12-01

    This study focuses on the quantity of CO2 produced by photodegradation in various pristine and disrupted water bodies. Photodegradation of dissolved organic matter (DOM) in the water column was evaluated in relation to two environmental factors e.g., the presence or absence of logging on the watershed and the contrast between natural lakes and hydroelectric reservoirs. Water samples were irradiated after filtration under 0,2µm, and subsequently analyzed for their CO2 production. Mean energy normalized for the spectral energy exposed to samples was determined to evaluate the photoreactivity of DOM under similar exposure conditions. In complement, organic matter samples had been concentrated via reverse osmosis. We then characterized the origin of DOM present in the water column with lignin biomarkers. Our results confirmed that the photomineralization increased significantly with DOM concentration. The daily photodegradation production was strikingly different in natural lakes and hydroelectric reservoirs. Average springtime and summertime production was evaluated at 5.45 ± 5.61 µmol.L-1.d-1 for lakes, compared to 14.21 ± 8.77 µmol.L-1.d-1 for boreal reservoirs. A similar comparison between ecosystems affected and unaffected by logging, also showed contrasting results for the photodegradation of DOM. Moreover, our lignin biomarkers increased significantly with CO2 generation. It thus appears that allochthonous organic matter strongly influences CO2 photoproduction. Finally, we evaluated the Photochemical Contribution to CO2 diffusive Fluxes (PCFCO2) between 14% and 32% depending on the degree of perturbation of the aquatic system.

  15. Spatially explicit simulation of hydrologically controlled carbon and nitrogen cycles and associated feedback mechanisms in a boreal ecosystem in Eastern Canada.

    Science.gov (United States)

    Govind, A.; Chen, J. M.; Margolis, H.

    2007-12-01

    Current estimates of terrestrial carbon overlook the effects of topographically-driven lateral flow of soil water. We hypothesize that this component, which occur at a landscape or watershed scale have significant influences on the spatial distribution of carbon, due to its large contribution to the local water balance. To this end, we further developed a spatially explicit ecohydrological model, BEPS-TerrainLab V2.0. We simulated the coupled hydrological and carbon cycle processes in a black spruce-moss ecosystem in central Quebec, Canada. The carbon stocks were initialized using a long term carbon cycling model, InTEC, under a climate change and disturbance scenario, the accuracy of which was determined with inventory plot measurements. Further, we simulated and validated several ecosystem indicators such as ET, GPP, NEP, water table, snow depth and soil temperature, using the measurements for two years, 2004 and 2005. After gaining confidence in the model's ability to simulate ecohydrological processes, we tested the influence of lateral water flow on the carbon cycle. We made three hydrological modeling scenarios 1) Explicit, were realistic lateral water routing was considered 2) Implicit where calculations were based on a bucket modeling approach 3) NoFlow, where the lateral water flow was turned off in the model. The results showed that pronounced anomalies exist among the scenarios for the simulated GPP, ET and NEP. In general, Implicit calculation overestimated GPP and underestimated NEP, as opposed to Explicit simulation. NoFlow underestimated GPP and overestimated NEP. The key processes controlling GPP were manifested through stomatal conductance which reduces under conditions of rapid soil saturation ( NoFlow ) or increases in the Implicit case, and, nitrogen availability which affects Vcmax, the maximum carboxylation rate. However, for NEP, the anomalies were attributed to differences in soil carbon pool decomposition, which determine the heterotrophic

  16. Synchronous interferometric demodulation of Placido mires applied to corneal topography

    CERN Document Server

    Servin, Manuel

    2012-01-01

    This paper presents a novel digital interferometric method to demodulate Placido fringe patterns. This is a synchronous method which uses a computer-stored conic-wavefront as demodulating reference. Here we focuses on the experimental aspects to phase-demodulate Placido mires applied to corneal topography. This synchronous method is applied to two topographic Placido images and their de-modulated corneal-slope deformation is estimated. This conic-interferometric method is highly robust against typical "noisy" signals in Placido topography such as: reflected eyelashes and iris structures. That is because the eyelashes and the iris structure are high frequency "noisy" signals corrupting the reflected Placido mire, so they are filtered-out by this method. Digital synchronous interferometry is here applied for the first time to demodulate corneal topographic concentric-rings images (Patent pending at the USPTO).

  17. The occurrence of rare earth elements in some Finnish mires

    Directory of Open Access Journals (Sweden)

    Yliruokanen, I.

    1995-12-01

    Full Text Available The content of the more abundant rare earths (RE (Y, La, Ce, Pr, Nd and Sm in the ash of 399 peat samples from 26 Finnish mires was determined by X-ray fluorescence spectrometry. The content of all rare earths (La-Lu, Y in 29 samples was also determined by spark source mass spectrometry. The median RE contents in peat ashes from areas where the bedrock consists of rapakivi granite, granite or archean gneiss are reported. Detailed data concerning the individual mires are also presented. The highest RE contents were found in samples from rapakivi granite areas where a strong negative Eu anomaly was also observed. The RE contents were in general highest at the basal peat layers.

  18. THE STUDY ON LATENT AND SENSIBLE HEAT FLUX OVER MIRE IN THE SANJIANG PLAIN

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Understanding how surface energy fluxes respond to environmental variables and how their components vary on daily and seasonal temporal scales are critical for understanding the ecological process of wetland ecosystem. In view of the fact that studies on surface energy flux over mire in China have been very limited, we have initiated a long-term latent and sensible heat flux (two main components of the surface energy balance) observation over mire in the Sanjiang Plain from June to October in 2004 with the eddy covariance technique. Results showed that the latent and sensible heat flux had large seasonal and diurnal variation during the period of measurement. Generally, latent heat flux between the mire wetland and the atmosphere reached the maximum value in June and then gradually decreased from June to October, whose daily mean fluxes were 9.83,8.00,7.33, 4.82 and 2.04 MJ/(m2·d), respectively. By comparison, sensible heat flux changed unnoticeably with season change from June to October, which were 1.47,0.88,1.75, 1.61,1.33 MJ/(m2·d) respectively. The diurnal variation of both latent and sensible heat flux varied noticeably within a day. After the sunrise, the latent and sensible heat flux increased and reached the maximum at noon (11:00-13:00). Then they decreased gradually and reached the minimum value during the nighttime. The patterns of temporal variation in latent and sensible heat flux were significantly controlled by environmental factors. The latent heat flux was linearly dependent on net radiation and increased with increasing vapour pressure deficit until the vapour pressure deficit surpassed 11 hPa. Wind speed effect on latent heat flux was more complicated and, in general, showed a positive correlation between them in daytime. The sensible heat flux was controlled mainly by air temperature difference between the land surface and the overlying air. However, when the temperature difference was larger than 0.3 ℃, it had no effect on the sensible

  19. Mineralization of cellulose in frozen boreal soils

    Science.gov (United States)

    Oquist, Mats G.; Segura, Javier; Sparrman, Tobias; Nilsson, Mats; Schleucher, Jurgen

    2015-04-01

    Soils of high-latitude ecosystems store a large fraction of the global soil carbon. In boreal forests, the microbial mineralization of soil organic matter (SOM) during winter can affect the ecosystems net carbon balance. Recent research has shown that microorganisms in the organic surface layer of boreal forest soil can mineralize and grow on simple, soluble monomeric substrates under frozen conditions. However, any substantial impacts of microbial activity in frozen soils on long-term soil carbon balances ultimately depends on whether soil microorganisms can utilize and grow the more complex, polymeric constituents of SOM. In order to evaluate the potential for soil microorganisms to metabolize carbon polymers at low temperatures, we incubated boreal forest soil samples amended with [13C]-cellulose and studied the microbial catabolic and anabolic utilization of the substrate under frozen and unfrozen conditions (-4 and +4°C). Freezing of the soil markedly reduced microbial utilization of the cellulose. The [13C]-CO2 production rate in the samples at +4°C were 0.52 mg CO2 SOM -1 day-1 while rates in the frozen samples (-4°C) were 0.01 mg CO2 SOM -1 day-1. However, newly synthetized [13C]-enriched cell membrane lipids, PLFAs, were detected in soil samples incubated both above and below freezing, confirming that cellulose can sustain also anabolic activity of the microbial populations under frozen conditions. The reduced metabolic rates induced by freezing indicate constraints on exoenzymatic activity, as well as substrate diffusion rates that we can attribute to reduced liquid water content of the frozen soil. We conclude that the microbial population in boreal forest soil has the capacity to metabolize, and grow, on polymeric substrates at temperatures below zero, which involves maintaining exoenzymatic activity in frozen soils. This capacity manifests the importance of SOM mineralization during the winter season and its importance for the net carbon balance of

  20. Quantifying the water balance of Mfabeni Mire (iSimangaliso Wetland Park, South Africa to understand its importance, functioning and vulnerability

    Directory of Open Access Journals (Sweden)

    P. Grundling

    2015-12-01

    Full Text Available Peatlands occurring in regions with high rates of total evaporation (ET, matching or exceeding precipitation (P during seasonal dry periods or longer-term dry spells, are dependent on sustained groundwater flows to ensure peat accumulation. The objective of this study was to quantify the water balance of Mfabeni Mire in South Africa over one year, and thereby define its contribution to downstream and adjacent ecosystems and identify risks and consequences likely to arise from future shifts in the water balance. P (1,031 mm and ET (1,053 mm dominated the water balance measured from May 2008 to April 2009. These were followed by groundwater inflows (14 mm, stream outflow (9 mm and storage change (-3 mm, a net loss in water stored in the mire with the smallest flux being groundwater outflow (0.3 mm. There were differences in the seasonal patterns of ET from the two dominant plant communities (swamp forest and sedge/reed fen, which probably resulted from their significantly different canopy structures. Limiting factors for ET were low vapour pressure deficit and cloud cover. Although the water balance of Mfabeni Mire was dominated by and equally split between ET and P, it still contributed a small efflux to downstream ecosystems by streamflow. Its value in a landscape where seasonality and long-term dry periods are major ecological drivers lies in its damping effect on climatic variability. This creates a more stable environment for adjacent aquatic ecosystems by contributing to a steady groundwater condition. Mires occurring in areas that experience dry periods, where water stress frequently threatens biodiversity, should be recognised as assets in natural resource management; and their potential to support adjacent ecosystems should be protected through planning and conservation practices. Management of the area should include careful consideration of any proposed changes in land use or encouragement of one plant community at the expense of

  1. Dissolved inorganic carbon and organic carbon in mires in the Forsmark area. A pilot study

    Energy Technology Data Exchange (ETDEWEB)

    Loefgren, Anders [EcoAnalytica, Haegersten (Sweden)

    2011-12-15

    Dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) are the large dissolved carbon pools in mires. They are both related to a number of factors such as groundwater flow, minerogenic influence and peat properties, which all are more or less related to peatland development stage. In a scenario of a release of radionuclides from an underground repository containing radioactive material, behaviour of these pools during the mire ontogeny will be of importance for the understanding of how C-14 will constitute a potential risk to humans and non-human biota. In this pilot study, DIC and DOC concentrations were investigated for three mires representing a potential sequence of peatland development in a coastal area at Forsmark in central Sweden characterized by land upheaval, a flat topography and calcareous content in the soil. The mires where chosen based on difference in height above the sea level, covering approximate 1000 years, and characteristics based on their vegetation. Water samples were collected during August from all three mires at two different depths in the anoxic layer of the mires, by extracting water from peat obtained with a peat corer. DIC concentrations where related to the age of the mires, with the lowest concentrations in the highest located mire. There was a positive correlation between pH and DIC, where the higher DIC concentrations were found in the 'richer' fens. DIC concentrations were also positively related to the conductivity within and between the mires, where conductivity would be a proxy for the dominating cation Ca{sup 2+} associated to the calcareous-influenced groundwater. DOC concentrations were highest in the oldest mire, but were similar in the younger mires. No patterns were found between DIC and DOC, and the peat bulk density. The report ends with suggestions on how a continued study could be improved.

  2. Browning boreal forests of western North America

    Science.gov (United States)

    Verbyla, David

    2011-12-01

    Forest Ecol. Manag. 227 219-32 Berg E E, Hillman K M, Dial R and DeRuwe A 2009 Recent woody invasion of wetlands on the Kenai Peninsula Lowlands, south-central Alaska: a major regime shift after 18 000 years of wet Sphagnum-sedge peat recruitment Canadian J. Forest Res. 39 2033-46 Brabets T P and Walvoord M A 2009 Trends in streamflow in the Yukon River Basin from 1944 to 2004 and the influence of the Pacific Decadal Oscillation J. Hydrol. 371 108-19 Bunn A G, Goetz S J, Kimball J S and Zhang K 2007 Northern high-latitude ecosystems respond to climate change EOS Trans. Am. Geophys. Union 88 333-40 D'Arrigo R, Kaufmann R K, Davi N, Jacoby G C, Laskowski C, Myneni R B and Cherubini P 2004 Thresholds for warming-induced growth decline at elevational tree line in the Yukon Territory, Canada Glob. Biogeochem. Cycles 18 GB3021 Goetz S J, Bunn A G, Fiske G J and Houghton R A 2005 Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance Proc. Natl Acad. Sci. USA 102 13521-5 Lloyd A H and Bunn A G 2007 Responses of the circumpolar boreal forest to the 20th century climate variability Environ. Res. Lett. 2 045013 Lloyd A H and Fastie C L 2002 Spatial and temporal variability in the growth and climate response of treeline trees in Alaska Clim. Change 52 481-509 Malmström C and Raffa K R 2000 Biotic disturbance agents in the boreal forest: considerations for vegetation change models Glob. Change Biol. 6 (Suppl. 1) 35-48 McGuire A D, Ruess R W, Lloyd A, Yarie J, Clein J S and Juday G P 2010 Vulnerability of white spruce tree growth in interior Alaska in response to climate variability: dendrochronological, demographic, and experimental perspectives Canadian J. Forest Res. 40 1197-209 Michealian M, Hogg E H, Hall R J and Arsenault E 2011 Massive mortality of aspen following severe drought along the southern edge of the Canadian boreal forest Glob. Change Biol. 17 2084-94 Parent M B and Verbyla D 2010 The browning of Alaska

  3. Studies on reference mires: 1. Lastensuo and Pesaensuo in 2010-2011

    Energy Technology Data Exchange (ETDEWEB)

    Haapanen, R. [Haapanen Forest Consulting, Vanhakylae (Finland); Aro, L. [Finnish Forest Research Institute, Vantaa (Finland); Lahdenperae, A.-M. [Saanio and Riekkola Oy, Helsinki (Finland); Helin, J.; Ikonen, A.T.K.

    2013-07-15

    New lakes and mires will develop in the sea area now surrounding Olkiluoto Island due to the postglacial land uplift. Despite the lack of well-developed mires at present Olkiluoto Island, input data for modelling the future development of the region are needed. Therefore, analogue objects in a larger geographical area have been selected. This Working Report presents first results from studies targeted on two such mires, Lastensuo and Pesaensuo. Not all collected samples have been analysed yet, but will appear in further versions of this report. The characteristics of the study locations appeared to correspond generally well with preliminary information based on literature and GIS analyses. Various site types were covered by the study locations on Lastensuo mire, whereas those on Pesaensuo mire were dwarf-shrub pine bog all over. Pine was the dominant tree species on all of the plots. Because sampling occurred in late summer, some berry (and on Pesaensuo also mushroom) samples were obtained of species typical of mires. On the studied plots, the deepest peat depths reached to 6.5 m (Lastensuo) and 5.5 m (Pesaensuo). Decomposition of sampled peat varied from very weakly decomposed to almost completely decomposed. Element analyses and distribution coefficient values (Kd) of the indigenous key elements Cl, Cs, I, Mo, Nb, Ni, Se and Sr were presented for one plot on Lastensuo mire. Procedures have been improved based on experiences gained on the field and laboratory analyses of the samples. Factors causing uncertainties and further ideas to improve the representativeness of the work are presented in this Working Report. Studies have already been continued on August 2012, when four more plots were established on the Lastensuo mire. In the future, sampling will be extended to another mire. (orig.)

  4. CO{sub 2} and CH{sub 4} fluxes and carbon balance in the atmospheric interaction of boreal peatlands

    Energy Technology Data Exchange (ETDEWEB)

    Alm, J.

    1997-12-31

    Release of CO{sub 2} from peat was studied using IR analyzer in a range of boreal peatlands under varying nutrient status and moisture conditions. Root associated CO{sub 2} efflux was separated from the total release by experiments both in the field and in a greenhouse. Emissions of CO{sub 2} and CH{sub 4} (the latter by gas chromatography) were measured during the snow-covered period and their contribution to the annual fluxes of these gases was inspected. Ecosystem exchange of CO{sub 2} under varying irradiation, temperature and moisture conditions was measured at different microsites at two peatland sites with different nutrient ecology. One site represented minerotrophic conditions during a wet growing season and the other site ombrotrophic conditions during an exceptionally dry growing season. Annual carbon balances were compiled for the two sites, and the role of the microsites in the annual carbon balance and CH{sub 4} release was studied. The Holocene history of CO{sub 2} sequestration and CH{sub 4} emission dynamics in a raised mire were simulated using lateral and vertical growth rates derived from radiocarbon ages of peat samples from mire bottom and vertical cores. The model was formulated for a geographic information system (GIS). Artificial or natural lowering of water table increased CO{sub 2} release from peat. A drought lasting from late May to July caused a 90 g C m{sup 2} net loss in the annual C balance of a natural ombrotrophic bog. In drained forested sites the increase in peat CO{sub 2} release could be even 100 %, but the development of the tree layer at least partially compensated for these losses. Wet conditions induced a net accumulation of 67 g C m{sup -2}a{sup -1} in the minerotrophic fen site, while the long term average accumulation rate is estimated to be only 15 g C m{sup -2}a{sup -1} for Finnish fens. Carbon balance in boreal peatlands is thus extremely sensitive to year-to-year climatic variations. Root activity of vascular plants

  5. Using high-dynamic-range digital repeat photography to measure plant phenology in a subarctic mire.

    Science.gov (United States)

    Garnello, A.; Dye, D. G.; Bogle, R.; Vogel, J.; Saleska, S. R.; Crill, P. M.

    2015-12-01

    A novel Visual Imaging System (VIS) was designed and deployed in a subarctic mire (68° 20' N, 19° 03'E) aimed at cataloging plant biological changes (phenology) and analyzing seasonal color shifts in relation to micrometeorological data along the summer growing season: June-November, 2015. The VIS is designed as a tower-based, solar-powered, automated phenology camera (Phenocam) that collects red, green, blue (RGB) and near-infrared (NIR) landscape images in High Dynamic Range (HDR) with fully programmable temporal resolution. HDR composite images are made through combining a series of rapid-capture photos with incremental increases of exposure times and a fixed focus, minimizing the spatial and visual data lost from shadows or from the over-saturation of light. This visual record of ecosystem phenology stages (Phenophases) is being used to (1) investigate vegetation-dependent spectral indices; (2) establish a cross-year comparison record of Phenophase seasonality; (3) investigate meteorological-dependent vegetation Phenophases; (4) provide ground-truthing measurements that enhance broader spatial-scale remote sensing analyses of subarctic wetlands.

  6. Geological settings of the protected Selisoo mire (northeastern Estonia threatened by oil shale mining

    Directory of Open Access Journals (Sweden)

    Helen Hiiemaa

    2014-05-01

    Full Text Available The protected Selisoo mire in northeastern Estonia is located above valuable oil shale resources, partly in the permitted mining area. We describe in detail the geomorphology and geological setting of the mire to understand the natural preconditions for its formation, development and preservation. We used the LiDAR-based digital elevation model for relief analysis, mapped the peat thickness with ground-penetrating radar and described the Quaternary cover through corings. Ridges, oriented perpendicular to the generally southward-sloping terrain, and shallow depressions at the surface of mineral soil have influenced mire formation and its spatio-temporal dynamics. The Quaternary cover under the mire is thin and highly variable. Therefore the mire is hydro­geologically insufficiently isolated from the limestone bedrock that is drained by the nearby oil shale mine and consequently the mining activities approaching the mire may have a negative influence on the wetland and proposed Natura 2000 site. Natura 2000 type wetlands, both protected or currently outside the nature reserves, cover a significant portion of the prospective oil shale mining areas. The distribution and resilience of those sites may significantly influence further utilization of oil shale resources.

  7. Developing a Student-Scientist Partnership: Boreal Forest Watch

    Science.gov (United States)

    Spencer, Shannon; Huczek, George; Muir, Bradley

    1998-03-01

    A student-scientist partnership outreach program was funded by the U.S. National Aeronautics and Space Administration's Boreal Ecosystem-Atmosphere Study (BOREAS) to involve students and teachers in scientific investigations pertinent to global change research occurring within the boreal region of Canada. Boreal Forest Watch was planned, designed and piloted by an interdisciplinary group of education and science professionals from the University of New Hampshire, the Prince Albert National Park, and several schools in central Saskatchewan, Canada. A two goal approach was adopted to 1) ensure the educational significance of the program and 2) introduce scientifically valid methods for collection of research data pertinent to global change scientists. Professional educators and school administrators from Saskatchewan were recruited to assist in project planning to ensure that the proposed activities fit within the existing curriculum framework. This process was essential for successful adoption of the program by participating teachers. The process and approach of initiating Boreal Forest Watch are presented in this paper. This program became fully functional in September, 1996 with the training of several participating teachers. Perspectives of the program and its future are provided by members of the design team. Boreal Forest Watch is a unique opportunity for both Canadian students and their teachers to explore their natural environment, learn scientific methods and principles, and contribute data to the global change research community.

  8. Global estimates of boreal forest carbon stocks and flux

    Science.gov (United States)

    Bradshaw, Corey J. A.; Warkentin, Ian G.

    2015-05-01

    The boreal ecosystem is an important global reservoir of stored carbon and a haven for diverse biological communities. The natural disturbance dynamics there have historically been driven by fire and insects, with human-mediated disturbances increasing faster than in other biomes globally. Previous research on the total boreal carbon stock and predictions of its future flux reveal high uncertainty in regional patterns. We reviewed and standardised this extensive body of quantitative literature to provide the most up-to-date and comprehensive estimates of the global carbon balance in the boreal forest. We also compiled century-scale predictions of the carbon budget flux. Our review and standardisation confirmed high uncertainty in the available data, but there is evidence that the region's total carbon stock has been underestimated. We found a total carbon store of 367.3 to 1715.8 Pg (1015 g), the mid-point of which (1095 Pg) is between 1.3 and 3.8 times larger than any previous mean estimates. Most boreal carbon resides in its soils and peatlands, although estimates are highly uncertain. We found evidence that the region might become a net carbon source following a reduction in carbon uptake rate from at least the 1980s. Given that the boreal potentially constitutes the largest terrestrial carbon source in the world, in one of the most rapidly warming parts of the globe (Walsh, 2014), how we manage these stocks will be influential on future climate dynamics.

  9. Interannual variation of methane emissions in a boreal peatland - cross-evaluation of chamber measurements (7 years) and model results (LPJ-WHyMe)

    Science.gov (United States)

    Forbrich, Inke; Wania, Rita; Saarnio, Sanna; Schäfer, Carolyn; Kutzbach, Lars; Wilmking, Martin

    2010-05-01

    Boreal peatlands are a major natural source of methane (CH4). Due to a lack of longterm measurements, the interannual variability of CH4 emission is still uncertain. To fill this gap, a combination of measurements and models is necessary. Here, we present chamber measurements of 7 years from a boreal mire in Finland and compare them with the output of a methane model that is integrated into a dynamic global vegetation model (LPJ-WHyMe: Wania et al. 2010). The mire is characterized by three microsite types which vary in vegetation cover and hydrology (hummocks, lawns, flarks). Chamber measurements have been conducted on all three microsite types in 1993 (Saarnio et al. 1997) and 2005-2007 (Becker et al. 2008, Schäfer 2007, Forbrich et al., in prep.), while in 1996-1998 they have been conducted exclusively on lawns (Saarnio et al. 2000). When all microsite types were measured, we upscale these measurements using classified high-aerial photographs (Becker et al. 2008). Additionally, we analyze the time series of measurements on lawns, which represent the most dominant CH4 source in the peatland (contributing on average 80% to the ecosystem flux: Forbrich et al., in prep.). LPJ-WHyMe has been applied for the grid cell containing the peatland for the years 1988-2008 using the settings of Wania et al. (2010). The upscaled chamber measurements (ecosystem flux estimate) for 1993 and 2005-2007 are generally lower than the model estimates (7-52%). Reasons for the mismatch can be both caused by the measurements and the model: Chamber measurements do miss ebullition fluxes (contributing 68.2% to the modelled annual emission: Wania et al. 2010) and/or the linear flux calculation underestimates the actual flux (Forbrich et al. 2010) while LPJ-WHyMe tends to overestimate the available carbon pool (Wania et al. 2009). Absolute values of observations of lawns in 1993 are well matched by model results (Wania et al. 2010). However, for the other years the model output is

  10. Quantifying nitrogen-fixation in feather moss carpets of boreal forests.

    Science.gov (United States)

    DeLuca, Thomas H; Zackrisson, Olle; Nilsson, Marie-Charlotte; Sellstedt, Anita

    2002-10-31

    Biological nitrogen (N) fixation is the primary source of N within natural ecosystems, yet the origin of boreal forest N has remained elusive. The boreal forests of Eurasia and North America lack any significant, widespread symbiotic N-fixing plants. With the exception of scattered stands of alder in early primary successional forests, N-fixation in boreal forests is considered to be extremely limited. Nitrogen-fixation in northern European boreal forests has been estimated at only 0.5 kg N ha(-1) yr(-1); however, organic N is accumulated in these ecosystems at a rate of 3 kg N ha(-1) yr(-1) (ref. 8). Our limited understanding of the origin of boreal N is unacceptable given the extent of the boreal forest region, but predictable given our imperfect knowledge of N-fixation. Herein we report on a N-fixing symbiosis between a cyanobacterium (Nostoc sp.) and the ubiquitous feather moss, Pleurozium schreberi (Bird) Mitt. that alone fixes between 1.5 and 2.0 kg N ha(-1) yr(-1) in mid- to late-successional forests of northern Scandinavia and Finland. Previous efforts have probably underestimated N-fixation potential in boreal forests.

  11. Optical Design of the SuMIRe PFS Spectrograph

    CERN Document Server

    Pascal, Sandrine; Barkhouser, Robert; Gunn, James

    2014-01-01

    The SuMIRe Prime Focus Spectrograph (PFS), developed for the 8-m class SUBARU telescope, will consist of four identical spectrographs, each receiving 600 fibers from a 2394 fiber robotic positioner at the telescope prime focus. Each spectrograph includes three spectral channels to cover the wavelength range 0.38-1.26 um with a resolving power ranging between 2000 and 4000. A medium resolution mode is also implemented to reach a resolving power of 5000 at 0.8 um. Each spectrograph is made of 4 optical units: the entrance unit which produces three corrected collimated beams and three camera units (one per spectral channel). The beam is split by using two large dichroics; and in each arm, the light is dispersed by large VPH gratings. The proposed optical design was optimized to achieve the requested image quality while simplifying the manufacturing of the whole optical system. The camera design consists in an innovative Schmidt camera observing a large field-of-view (10 degrees) with a very fast beam. To achieve...

  12. MIRE:A GRAPHICAL R PACKAGE FOR MICRORNA RELATED ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    Xing-qi Yan; Kang Tu; Lu Xie; Yi-xue Li; Bin Yin; Yan-hua Gong; Jian-gang Yuan; Bo-qin Qiang; Xiao-zhong Peng

    2008-01-01

    Objective To provide a set of useful analysis tools for the researchers to explore the microRNA data.Methods The R language was used for generating the Graphical Users Interface and implementing most functions.Some Practical Extraction and Report Language (Perl) scripts were used for parsing source fries.Results We developed a graphical R package named miRE,which was designated for the analysis of microRNA functions,genomic organization,etc.This package provided effective and convenient tools for molecular biologists to deal with routine analyses in microRNA-related research.With its help,the users would be able to build a desktopcentered microRNA research environment quite easily and effectively,miRE is freely available at http://www.biosino.org/~kanghu/WorkPresentation/miRE/miRE.html.A detailed user manual and tutorials with example code and image are also available.Conclusion miRE is a tool providing an open-source,user-friendly,integrated interface for microRNA-related analysis.With its help,researchers can perform microRNA-related analysis more efficiently.

  13. Fire and Climate Change in Boreal Forests

    Science.gov (United States)

    Flannigan, M. D.; Logan, K. A.; Stocks, S. J.; Wotton, B. M.; Amiro, B. D.

    2004-12-01

    Fire is the major stand-renewing agent for much of the circumboreal forest, and greatly influences the structure and function of boreal ecosystems from regeneration through mortality. Current estimates are that an average of 5-15 million hectares burn annually in boreal forests, almost exclusively in Siberia, Canada and Alaska. There is a growing global awareness of the importance and vulnerability of the boreal region to projected future climate change. Fire activity is strongly influenced by four factors - weather/climate, vegetation \\(fuels\\), natural ignition agents and humans. Climate and weather are strongly linked to fire activity which suggests that the fire regime will respond rapidly to changes in climate. Recent results suggest that area burned by fire is related to temperature and fuel moisture. The climate of the northern hemisphere has been warming due to an influx of radiatively active gases \\(carbon dioxide, methane etc.\\) as a result of human activities. This altered climate, modelled by General Circulation Models \\(GCMs\\), indicates a profound impact on fire activity in the circumboreal forest. Recent results using GCMs suggest that in many regions fire weather/fire danger conditions will be more severe, area burned will increase, people-caused and lightning-caused ignitions will increase, fire seasons will be longer and the intensity and severity of fires will increase. This increase in fire activity may lead to a positive feedback cycle with the increased release of greenhouse gases. Although a run away scenario is unlikely as changes in vegetation would limit the positive feedback cycle. Changes in fire activity as a result of climate change could have a greater and more immediate impact on vegetation distribution and abundance as compared to the direct impact of climate change.

  14. Long-term CO2 flux dynamics and soil C stock changes of a drained fen mire under different grassland management practices in Northeast Germany

    Science.gov (United States)

    Augustin, Juergen; Giebels, Michael; Albiac Borraz, Elisa; Hoffmann, Mathias; Sommer, Michael

    2014-05-01

    Fen mires, widely distributed in Germany and Northern Europe, contain extreme high amounts of carbon (up to 5000 t C per hectare). For this reason, they play an important role in the global cycle of the greenhouse gases carbon dioxide (CO2) and methane (CH4). Currently more than 95% of all fen mires in central Europe are drained. Therefore, they are assumed to represent extremely strong sources for CO2,accompanied by a fast reduction of the peat carbon stocks. For a number of reasons it is not possible to overcome this problem by restoration measures like flooding at the most drained fen sites. Moreover, there are till now just few and contradictory information about the contribution of alternative land use forms like grassland extensification on the reduction of the CO2 source function of these organic soils. As a contribution to clearing this deficit, we have ongoingly measured the CO2 and CH4 exchange as well as the changes in C stock on a deeply drained fen mire near the village of Paulinenaue from 2007 till 2012. The measurement sites is located within the so-called Rhin-Havelluch, an 80000 ha shallow paludification mire complex in the northwest of Berlin. The investigation included extensively and intensively used meadows (one cut vs. three cuts) on two soil types with different C stocks (Hemic Rheic Histosol vs. Mollic Gleysol). We used transparent chambers for measuring the CO2 flux net ecosystem exchange (difference between gross primary production and ecosystem respiration) and non-transparent chambers for measuring the CO2 flux ecosystem respiration and the CH4 exchange. Determined soil stock changes based on a C budget approach, including cumulated annual net ecosystem exchange, cumulated CH4 exchange, C export by harvest, and C import by fertilization. All current C fluxes were influenced in a complex way by ground-water level, plant development, land use intensity (cut frequency) and current weather conditions. Averaged over the whole investigation

  15. Spatial variability of selected physicochemical parameters within peat deposits in small valley mire: a geostatistical approach

    Directory of Open Access Journals (Sweden)

    Pawłowski Dominik

    2014-12-01

    Full Text Available Geostatistical methods for 2D and 3D modelling spatial variability of selected physicochemical properties of biogenic sediments were applied to a small valley mire in order to identify the processes that lead to the formation of various types of peat. A sequential Gaussian simulation was performed to reproduce the statistical distribution of the input data (pH and organic matter and their semivariances, as well as to honouring of data values, yielding more ‘realistic’ models that show microscale spatial variability, despite the fact that the input sample cores were sparsely distributed in the X-Y space of the study area. The stratigraphy of peat deposits in the Ldzań mire shows a record of long-term evolution of water conditions, which is associated with the variability in water supply over time. Ldzań is a fen (a rheotrophic mire with a through-flow of groundwater. Additionally, the vicinity of the Grabia River is marked by seasonal inundations of the southwest part of the mire and increased participation of mineral matter in the peat. In turn, the upper peat layers of some of the central part of Ldzań mire are rather spongy, and these peat-forming phytocoenoses probably formed during permanent waterlogging.

  16. Nitrogen balance along a boreal forest fire chronosequence

    Science.gov (United States)

    Palviainen, Marjo; Pumpanen, Jukka; Berninger, Frank; Heinonsalo, Jussi; Sun, Hui; Köster, Egle; Köster, Kajar

    2016-04-01

    Fire is a major natural disturbance factor in boreal forests, and the frequency of forest fires is predicted to increase due to climate change in boreal regions. Because boreal forests comprise 30% of the global forest area, increases in the annual area burned may have significant implications for global carbon and nitrogen (N) cycles. The productivity of boreal forests is limited by low N availability. Fires cause N loss from ecosystems through oxidation and volatilization of N stored in biomass and soil. N balance may be poorly buffered against forest fires especially in sub-arctic ecosystems where atmospheric N deposition is low. Although forest fires alter N dynamics, there are little quantitative data available on N pools and fluxes through post-fire succession in sub-arctic boreal forests. We studied changes in N pools and fluxes, and the overall N balance across a 155-year forest fire chronosequence in sub-arctic Scots pine (Pinus sylvestris) forests in Värriö Strict Nature Reserve situated in Finnish Lapland (67°46' N, 29°35' E). Soil was the largest N pool in all forest age classes and comprised 69-82% of the total ecosystem N pool. The total ecosystem N pool varied from 622 kg ha-1 in the recently burned forest to 960 kg ha-1 in the 155-year-old forest. The forests were N sinks in all age classes the annual N accumulation rate being 2.28 kg ha-1 yr-1 which was distributed almost equally between soil and biomass. The observed changes in ecosystem N pools were consistent with the computed N balance 2.10 kg ha-1 yr-1 over the 155-year post-fire period (Balance= (atmospheric deposition + N fixation) - (leaching + N2O emissions)). The results indicated that N deposition is an important component of the N balance and the N outputs are small (13% of the inputs) in the studied ecosystems. N2O fluxes were negligible (≤ 0.01 kg ha-1 yr-1) compared to the other N fluxes. The biological N fixation increased with succession and constituted 9% of the total N

  17. Landscape scale patterns in the character of natural organic matter in a Swedish boreal stream network

    Directory of Open Access Journals (Sweden)

    J. Temnerud

    2009-09-01

    Full Text Available This paper defines landscape-scale patterns in the character of natural organic matter (NOM and tests for relationships to catchment soil, vegetation and topography. The drainage network of a boreal catchment, subcatchment size 0.12–78 km2, in Northern Sweden was sampled in August 2002 during a period of stable low water flow. The NOM was characterized with UV/Vis spectroscopy, fluorescence, XAD-8 fractionation (%humic substances, gel permeation chromatography (apparent molecular weight, and elemental composition (C:N. The largest spatial variation was found for C:N, absorbance ratio, and specific visible absorptivity. The lowest variation was in fluorescence index, %humic substances and molecular retention time. The variation in total organic carbon (TOC, iron and aluminium concentration was more than twice that of C:N. Between headwater and downstream sites no significant changes were distinguished in the NOM character. At stream reaches, junctions and lakes little change (<10% in NOM character was observed. Common factor analysis and partial least squares regression (PLS revealed that the spatial variation in surface coverage of lakes and mires could explain some of the variation of TOC and NOM character. Our suggestion is that the mosaic of landscape elements (different amounts of water from lakes, forest soil and mires delivers NOM with varying characteristics to a channel network that mixes conservatively downstream, with possible small changes at some stream reaches, junctions and lakes.

  18. Landscape scale patterns in the character of natural organic matter in a Swedish boreal stream network

    Directory of Open Access Journals (Sweden)

    J. Temnerud

    2009-04-01

    Full Text Available This paper defines landscape-scale patterns in the character of natural organic matter (NOM and tests for relationships to catchment soil, vegetation and topography. The drainage network of a boreal catchment, subcatchment size 0.12–78 km2, in Northern Sweden was sampled in August 2002 during a period of stable low water flow. The NOM was characterized with UV/Vis spectroscopy, fluorescence, XAD-8 fractionation (%humic substances, gel permeation chromatography (apparent molecular weight, and elemental composition (C:N. The largest spatial variation was found for C:N, absorbance ratio, and specific visible absorptivity. The lowest variation was in fluorescence index, %humic substances and molecular retention time. But the variation in total organic carbon (TOC, iron and aluminium concentration was more than twice that of C:N. Between headwater and downstream sites no significant changes were distinguished in the NOM character. At stream reaches, junctions and lakes little change (<10% in NOM character was observed. Common factor analysis and partial least squares regression (PLS revealed that the spatial variation in surface coverage of lakes and mires could explain some of the variation of TOC and NOM character. Our suggestion is that the mosaic of landscape elements (different amounts of water from lakes, forest soil and mires delivers NOM with varying characteristics to a channel network that mixes conservatively downstream, with possible small changes at some stream reaches, junctions and lakes.

  19. Simultaneous high C fixation and high C emissions in Sphagnum mires

    Directory of Open Access Journals (Sweden)

    S. F. Harpenslager

    2015-03-01

    Sphagnum's active lowering of the pH, which triggers the chemical release of CO2 from bicarbonate. Our results clearly illustrate that high Sphagnum biomass production may still coincide with high C emission. These counterintuitive C dynamics in mire succession seem to be the result of both species- and biomass-dependent acidification and buffered water infiltration. Together, these processes can explain part of the large variation in C fluxes (ranging from C sequestration to C release reported for pristine mires in literature.

  20. Fire impacts on European Boreal soils: A review

    Science.gov (United States)

    Pereira, Paulo; Oliva, Marc; Cerda, Artemi

    2016-04-01

    Fire is an important natural disturbance in boreal ecosystems, fundamental to understand plant distribution (Ryan, 2002; Wallenius et al., 2004; Granstrom, 2001). Nevertheless, nowadays the intense and successful, fire suppression measures are changing their ecological role (Pereira et al., 2013a,b). This is consequence of the lack of understanding of stakeholders and decision makers about the role of the fire in the ecosystems (Mierasukas and Pereira, 2013; Pereira et al., 2016). This fire suppression measures are increasing the amount of fuel accumulation and the risk of severe wildfires, which can increase of frequency and severity in a context of climate change. Fire is a good tool for landscape management and restoration of degraded ecosystems (Toivanen and Kotiaho, 2007). Fire is considered a soil forming factor (Certini, 2014) and in boreal environments it has been observed that low fire severities, do not change importantly soil properties, mean fire severities induce positive impacts on soil, since add an important amounts of nutrients into soil profile and high severity fires had negative impacts due to the high consumption of organic matter (Vanha-Majamaa et al., 2007; Pereira et al., 2014). References Certini, G., 2014. Fire as a soil-forming factor. Ambio, 43, 191-195 Granstrom A. 2001. Fire management for biodiversity in the European Boreal forest. Scandinavian Journal of Forest Research 3: 62-69. Mierauskas, P., Pereira, P. (2013) Stakeholders perception about prescribed fire use in Lithuania. First results, Flamma, 4(3), 157-161. Pereira, P., Cerdà, A., Jordán, A., Bolutiene, V., Úbeda, X., Pranskevicius, M., Mataix-Solera, J. (2013) Spatio-temporal vegetation recuperation after a grassland fire in Lithuania, Procedia Environmental Sciences, 19:856-864 Pereira, P., Mierauskas, P., Ubeda, X., Mataix-Solera, J.,Cerda, A. (2012) Fire in protected areas - the effect of the protection and importance of fire management, Environmental Research

  1. Development and validation of the Measure of Indigenous Racism Experiences (MIRE

    Directory of Open Access Journals (Sweden)

    Paradies Yin C

    2008-04-01

    Full Text Available Abstract Background In recent decades there has been increasing evidence of a relationship between self-reported racism and health. Although a plethora of instruments to measure racism have been developed, very few have been described conceptually or psychometrically Furthermore, this research field has been limited by a dearth of instruments that examine reactions/responses to racism and by a restricted focus on African American populations. Methods In response to these limitations, the 31-item Measure of Indigenous Racism Experiences (MIRE was developed to assess self-reported racism for Indigenous Australians. This paper describes the development of the MIRE together with an opportunistic examination of its content, construct and convergent validity in a population health study involving 312 Indigenous Australians. Results Focus group research supported the content validity of the MIRE, and inter-item/scale correlations suggested good construct validity. A good fit with a priori conceptual dimensions was demonstrated in factor analysis, and convergence with a separate item on discrimination was satisfactory. Conclusion The MIRE has considerable utility as an instrument that can assess multiple facets of racism together with responses/reactions to racism among indigenous populations and, potentially, among other ethnic/racial groups.

  2. The role of fire in the boreal carbon budget

    Science.gov (United States)

    Harden, J.W.; Trumbore, S.E.; Stocks, B.J.; Hirsch, A.; Gower, S.T.; O'Neill, K. P.; Kasischke, E.S.

    2000-01-01

    To reconcile observations of decomposition rates, carbon inventories, and net primary production (NPP), we estimated long-term averages for C exchange in boreal forests near Thompson, Manitoba. Soil drainage as defined by water table, moss cover, and permafrost dynamics, is the dominant control on direct fire emissions. In upland forests, an average of about 10-30% of annual NPP was likely consumed by fire over the past 6500 years since these landforms and ecosystems were established. This long-term, average fire emission is much larger than has been accounted for in global C cycle models and may forecast an increase in fire activity for this region. While over decadal to century times these boreal forests may be acting as slight net sinks for C from the atmosphere to land, periods of drought and severe fire activity may result in net sources of C from these systems.

  3. The Effects of Moose (Alces alces) Browsing on Boreal Tree Species in Norway and Quebec

    OpenAIRE

    2015-01-01

    The circumpolar boreal forest is important for recreational purposes, timber harvesting, game meat and as a CO2-storage. Biodiversity is important for maintaining these ecosystem services. Many boreal forests are experiencing an increase in the cervid populations. Densities of moose Alces alces not seen before in modern history have been reported several places. Knowledge about the interactions between this selective browser and the regenerating forest is therefore of importance for both the ...

  4. Simultaneous high C fixation and high C emissions in Sphagnum mires

    Science.gov (United States)

    Harpenslager, S. F.; van Dijk, G.; Kosten, S.; Roelofs, J. G. M.; Smolders, A. J. P.; Lamers, L. P. M.

    2015-08-01

    Peatlands play an important role in the global carbon (C) cycle due to their large C storage potential. Their C sequestration rates, however, highly vary depending on climatic and geohydrological conditions. Transitional mires are often characterised by floating peat with infiltration of buffered groundwater or surface water. Sphagnum mosses grow on top, producing recalcitrant organic matter and fuelling large C stocks. As Sphagnum species strongly differ in their tolerance to the higher pH in these mires, their species composition can be expected to influence C dynamics in transitional mires. We therefore experimentally determined growth and net C sequestration rates for four different Sphagnum species (Sphagnum squarrosum, S. palustre, S. fallax and S. magellanicum) in aquaria, with floating peat influenced by the infiltration of buffered water. Surprisingly, even though the first three species increased their biomass, the moss-covered peat still showed a net efflux of CO2 that was up to 3 times higher than that of bare peat. This species-dependent C release could be explained by Sphagnum's active lowering of the pH, which triggers the chemical release of CO2 from bicarbonate. Our results clearly illustrate that high Sphagnum biomass production may still coincide with high C emission. These counterintuitive C dynamics in mire succession seem to be the result of both species- and biomass-dependent acidification and buffered water infiltration. Together, these processes can explain part of the large variation in C fluxes (ranging from C sequestration to C release) reported for pristine mires in the literature.

  5. Impact of mire reclamation on export potential and characteristics of dissolved carbons in the Sanjiang Plain, Northeast China

    Directory of Open Access Journals (Sweden)

    Y. D. Guo

    2012-05-01

    Full Text Available As an important dissolved organic carbon (DOC reservoir, the mires in the Sanjiang Plain, Northeast China, have been suffering from large scale of reclamation, and thus elevated loss and degradation since the 1960s. This study compares the export dynamics of the dissolved carbons, as well as the chemical characteristics of DOC, in the natural mire, degraded mire and drainage ditches during the growing seasons from 2008 to 2010 with the aim to clarify the final effects of the longterm reclamation on the export dynamics of the dissolved carbons. Results show that the average concentrations of total dissolved carbon (TC and DOC are much higher in natural mires than that in degraded mire and drainage ditches. The DOC concentration for natural mires, about 35.53 ± 5.15 mg l−1 on average, is nearly 2.39 times of that in degraded mire (14.84 ± 4.21 mg l−1 and 2.77 times of the average value in ditches (12.84 ± 4.49 mg l−1. Similarly, the hydrophobic fraction and SUVA254 of DOC also represent lower values in the degraded mire and ditches, which suggests that mire reclamation has resulted not only in the reduced DOC concentrations but also in the reduced chemical stability. Whereas the inorganic dissolved carbons (DIC exhibits obvious increased trends in drainage ditches in comparison to natural mires. Analyses of exitation-emission fluorescence spectra reveal that the reclamation has greatly altered the DOC composition with more biological organic substances exporting from the Sanjiang Plain. The presence of protein- and tryptophan-like substances in the ditches indicates there has been extensive agricultural pollution in the surface waters. Changes in the hydrological regime of the mire landscapes by sustained agriculture activities are deemed the prodominant reason, and the trends in the export dynamics of dissolved carbons will keep on if mire reclamation continues in the future.

  6. Simulating Changes in Fires and Ecology of the 21st Century Eurasian Boreal Forests of Siberia

    Directory of Open Access Journals (Sweden)

    Ksenia Brazhnik

    2017-02-01

    Full Text Available Wildfires release the greatest amount of carbon into the atmosphere compared to other forest disturbances. To understand how current and potential future fire regimes may affect the role of the Eurasian boreal forest in the global carbon cycle, we employed a new, spatially-explicit fire module DISTURB-F (DISTURBance-Fire in tandem with a spatially-explicit, individually-based gap dynamics model SIBBORK (SIBerian BOReal forest simulator calibrated to Krasnoyarsk Region. DISTURB-F simulates the effect of forest fire on the boreal ecosystem, namely the mortality of all or only the susceptible trees (loss of biomass, i.e., carbon within the forested landscape. The fire module captures some important feedbacks between climate, fire and vegetation structure. We investigated the potential climate-driven changes in the fire regime and vegetation in middle and south taiga in central Siberia, a region with extensive boreal forest and rapidly changing climate. The output from this coupled simulation can be used to estimate carbon losses from the ecosystem as a result of fires of different sizes and intensities over the course of secondary succession (decades to centuries. Furthermore, it may be used to assess the post-fire carbon storage capacity of potential future forests, the structure and composition of which may differ significantly from current Eurasian boreal forests due to regeneration under a different climate.

  7. Long term patterns in dissolved organic carbon, major elements and trace metals in boreal headwater catchments: trends, mechanisms and heterogeneity

    Directory of Open Access Journals (Sweden)

    S. K. Oni

    2012-12-01

    Full Text Available The boreal landscape is a complex, spatio-temporally varying mosaic of forest and mire landscape elements that control surface water hydrology and chemistry. Here, we assess long-term water quality time-series from three nested headwater streams draining upland forest (C2, peat/mire (C4 and mixed (C7 (forest and mire catchments. Temporal trends in weather and runoff (1981–2008; dissolved organic carbon concentration [DOC] (1993–2010 and other water quality parameters (1987–2011 were assessed. There was no significant annual trend in precipitation or runoff but a significant monotonic increasing trend existed in air temperature and length of growing season. Stream [DOC] was positively correlated with some trace metals (copper, iron and zinc and negatively with several other chemical parameters (e.g. sulfate, conductivity, calcium. Both sulfate and conductivity showed declining trends, while a significant increase was observed in pH during winter and spring. Calcium and magnesium showed monotonic decreasing trends. The declining trajectories of stream base cation and sulfate concentrations during other times of the year were not accompanied by changes in pH and alkalinity. Water temperature increased significantly both annually and in most months while iron and DOC concentrations showed significant increases in autumn months. Though all streams showed significant positive trends in [DOC] in autumn, only C2 had a significant annual increasing trend. There was also a shift in the magnitude of variability in spring [DOC] and increasing trend of summer baseflow [DOC] in C2 and C7.

  8. Ecological Sustainability of Birds in Boreal Forests

    Directory of Open Access Journals (Sweden)

    Gerald Niemi

    1998-12-01

    Full Text Available We review characteristics of birds in boreal forests in the context of their ecological sustainability under both natural and anthropogenic disturbances. We identify the underlying ecological factors associated with boreal bird populations and their variability, review the interactions between boreal bird populations and disturbance, and describe some tools on how boreal bird populations may be conserved in the future. The boreal system has historically been an area with extensive disturbance such as fire, insect outbreaks, and wind. In addition, the boreal system is vulnerable to global climate change as well as increasing pressure on forest and water resources. Current knowledge indicates that birds play an important role in boreal forests, and sustaining these populations affords many benefits to the health of boreal forests. Many issues must be approached with caution, including the lack of knowledge on our ability to mimic natural disturbance regimes with management, our lack of understanding on fragmentation due to logging activity, which is different from permanent conversion to other land uses such as agriculture or residential area, and our lack of knowledge on what controls variability in boreal bird populations or the linkage between bird population fluctuations and productivity. The essential role that birds can provide is to clarify important ecological concerns and variables that not only will help to sustain bird populations, but also will contribute to the long-term health of the boreal forest for all species, including humans.

  9. Main dynamics and drivers of boreal forests fire regimes during the Holocene

    Science.gov (United States)

    Molinari, Chiara; Lehsten, Veiko; Blarquez, Olivier; Clear, Jennifer; Carcaillet, Christopher; Bradshaw, Richard HW

    2015-04-01

    Forest fire is one of the most critical ecosystem processes in the boreal megabiome, and it is likely that its frequency, size and severity have had a primary role in vegetation dynamics since the Last Ice Age (Kasischke & Stocks 2000). Fire not only organizes the physical and biological attributes of boreal forests, but also affects biogeochemical cycling, particularly the carbon balance (Balshi et al. 2007). Due to their location at climatically sensitive northern latitudes, boreal forests are likely to be significantly affected by global warming with a consequent increase in biomass burning (Soja et al. 2007), a variation in vegetation structure and composition (Johnstone et al. 2004) and a rise in atmospheric carbon dioxide concentration (Bond-Lamberty et al. 2007). Even if the ecological role of wildfire in boreal forest is widely recognized, a clearer understanding of the environmental factors controlling fire dynamics and how variations in fire regimes impact forest ecosystems is essential in order to place modern fire processes in a meaningful context for projecting ecosystem behaviour in a changing environment (Kelly et al. 2013). Because fire return intervals and successional cycles in boreal forests occur over decadal to centennial timescales (Hu et al. 2006), palaeoecological research seems to be one of the most promising tool for elucidating ecosystem changes over a broad range of environmental conditions and temporal scales. Within this context, our first aim is to reconstruct spatial and temporal patterns of boreal forests fire dynamics during the Holocene based on sedimentary charcoal records. As a second step, trends in biomass burning will be statistically analysed in order to disentangle between regional and local drivers. The use of European and north-American sites will give us the unique possibility to perform a large scale analysis on one of the broadest biome in the world and to underline the different patterns of fire in these two

  10. Visible camera cryostat design and performance for the SuMIRe Prime Focus Spectrograph (PFS)

    CERN Document Server

    Smee, Stephen A; Golebiowski, Mirek; Hope, Stephen C; Madec, Fabrice; Gabriel, Jean-Francois; Loomis, Craig; Fur, Arnaud Le; Dohlen, Kjetil; Mignant, David Le; Barkhouser, Robert; Carr, Michael; Hart, Murdock; Tamura, Naoyuki; Shimono, Atsushi; Takato, Naruhisa

    2016-01-01

    We describe the design and performance of the SuMIRe Prime Focus Spectrograph (PFS) visible camera cryostats. SuMIRe PFS is a massively multi-plexed ground-based spectrograph consisting of four identical spectrograph modules, each receiving roughly 600 fibers from a 2394 fiber robotic positioner at the prime focus. Each spectrograph module has three channels covering wavelength ranges 380~nm -- 640~nm, 640~nm -- 955~nm, and 955~nm -- 1.26~um, with the dispersed light being imaged in each channel by a f/1.07 vacuum Schmidt camera. The cameras are very large, having a clear aperture of 300~mm at the entrance window, and a mass of $\\sim$280~kg. In this paper we describe the design of the visible camera cryostats and discuss various aspects of cryostat performance.

  11. Differentiating moss from higher plants is critical in studying the carbon cycle of the boreal biome

    DEFF Research Database (Denmark)

    Yuan, Wenping; Liu, Shuguang; Dong, Wenjie

    2014-01-01

    that vascular plants can because of its much lower photosynthetic capacity. Here, based on eddy covariance measurements, we show that the difference in photosynthetic capacity between these two plant functional types has never been explicitly included when estimating regional GPP in the boreal region, resulting...... in a substantial overestimation. The magnitude of this overestimation could have important implications regarding a change from a current carbon sink to a carbon source in the boreal region. Moss abundance, associated with ecosystem disturbances, needs to be mapped and incorporated into GPP estimates in order...

  12. Non-methane volatile organic compound flux from a subarctic mire in Northern Sweden

    OpenAIRE

    Bäckstrand, Kristina; Crill, Patrick M.; Mastepanov, Mikhail; Christensen, Torben R.; Bastviken, David

    2011-01-01

    Biogenic NMVOCs are mainly formed by plants and microorganisms. They have strong impact on the local atmospheric chemistry when emitted to the atmosphere. The objective of this study was to determine if there are significant emissions of non-methane volatile organic compounds (NMVOCs) from a subarctic mire in northern Sweden. Subarctic peatlands in discontinuous permafrost regions are undergoing substantial environmental changes due to their high sensitivity to climate warming and there is ne...

  13. Using three decades of Landsat data to characterize changes and vulnerability of temperate and boreal forest phenology to climate change

    Science.gov (United States)

    Melaas, E. K.; Sulla-menashe, D. J.; Gray, J. M.; Friedl, M. A.

    2015-12-01

    Climate change is creating well-documented impacts on terrestrial ecosystems. Among the best known of these impacts are changes to the growing season of temperate and boreal forests. Changes in phenology provide useful diagnostics of climate change impacts in these biomes, influence coupled biosphere-atmosphere interactions, and also affect regional-to-global carbon budgets. Extreme events and climate variability complicate the response of ecosystems and increase vulnerability by inducing large phenological responses that affect ecosystem function at seasonal (and longer) time scales. Studies using in-situ measurements have suggested that the growing season of temperate and boreal ecosystems is changing, and remote sensing-based research using time series imagery from coarse resolution sensors appear to confirm this trend. Specifically, studies using AVHRR NDVI data have documented changes in growing season NDVI that indicate widespread perturbations to boreal and temperate forests in response to climate change. However, the coarse spatial resolution and other limitations of AVHRR data constrain the types of inferences that can be drawn from these data. We describe research to address these challenges using Landsat data. Specifically, we use a new methodology that exploits dense time series of Landsat images to quantify spatio-temporal patterns in North American temperate and boreal forest growing season dynamics. Our methodology uses a sampling strategy designed to capture geographic variation in temperate and boreal forest properties, and focuses on regions of overlap between adjacent Landsat scenes, thereby significantly increasing the temporal sampling of Landsat images. Results from this research provide retrospective characterization of changes to temperate and boreal forest growing seasons spanning 30+ years at 30 m spatial resolution. In doing so, this research is (1) dramatically improving information about how temperate and boreal forests have changed in

  14. Climate-induced boreal forest change: Predictions versus current observations

    Science.gov (United States)

    Soja, Amber J.; Tchebakova, Nadezda M.; French, Nancy H. F.; Flannigan, Michael D.; Shugart, Herman H.; Stocks, Brian J.; Sukhinin, Anatoly I.; Parfenova, E. I.; Chapin, F. Stuart; Stackhouse, Paul W.

    2007-04-01

    For about three decades, there have been many predictions of the potential ecological response in boreal regions to the currently warmer conditions. In essence, a widespread, naturally occurring experiment has been conducted over time. In this paper, we describe previously modeled predictions of ecological change in boreal Alaska, Canada and Russia, and then we investigate potential evidence of current climate-induced change. For instance, ecological models have suggested that warming will induce the northern and upslope migration of the treeline and an alteration in the current mosaic structure of boreal forests. We present evidence of the migration of keystone ecosystems in the upland and lowland treeline of mountainous regions across southern Siberia. Ecological models have also predicted a moisture-stress-related dieback in white spruce trees in Alaska, and current investigations show that as temperatures increase, white spruce tree growth is declining. Additionally, it was suggested that increases in infestation and wildfire disturbance would be catalysts that precipitate the alteration of the current mosaic forest composition. In Siberia, 7 of the last 9 yr have resulted in extreme fire seasons, and extreme fire years have also been more frequent in both Alaska and Canada. In addition, Alaska has experienced extreme and geographically expansive multi-year outbreaks of the spruce beetle, which had been previously limited by the cold, moist environment. We suggest that there is substantial evidence throughout the circumboreal region to conclude that the biosphere within the boreal terrestrial environment has already responded to the transient effects of climate change. Additionally, temperature increases and warming-induced change are progressing faster than had been predicted in some regions, suggesting a potential non-linear rapid response to changes in climate, as opposed to the predicted slow linear response to climate change.

  15. Climate-Induced Boreal Forest Change: Predictions versus Current Observations

    Science.gov (United States)

    Soja, Amber J.; Tchebakova, Nadezda M.; French, Nancy H. F.; Flannigan, Michael D.; Shugart, Herman H.; Stocks, Brian J.; Sukhinin, Anatoly I.; Parfenova, E. I.; Chapin, F. Stuart, III; Stackhouse, Paul W., Jr.

    2007-01-01

    For about three decades, there have been many predictions of the potential ecological response in boreal regions to the currently warmer conditions. In essence, a widespread, naturally occurring experiment has been conducted over time. In this paper, we describe previously modeled predictions of ecological change in boreal Alaska, Canada and Russia, and then we investigate potential evidence of current climate-induced change. For instance, ecological models have suggested that warming will induce the northern and upslope migration of the treeline and an alteration in the current mosaic structure of boreal forests. We present evidence of the migration of keystone ecosystems in the upland and lowland treeline of mountainous regions across southern Siberia. Ecological models have also predicted a moisture-stress-related dieback in white spruce trees in Alaska, and current investigations show that as temperatures increase, white spruce tree growth is declining. Additionally, it was suggested that increases in infestation and wildfire disturbance would be catalysts that precipitate the alteration of the current mosaic forest composition. In Siberia, five of the last seven years have resulted in extreme fire seasons, and extreme fire years have also been more frequent in both Alaska and Canada. In addition, Alaska has experienced extreme and geographically expansive multi-year outbreaks of the spruce beetle, which had been previously limited by the cold, moist environment. We suggest that there is substantial evidence throughout the circumboreal region to conclude that the biosphere within the boreal terrestrial environment has already responded to the transient effects of climate change. Additionally, temperature increases and warming-induced change are progressing faster than had been predicted in some regions, suggesting a potential non-linear rapid response to changes in climate, as opposed to the predicted slow linear response to climate change.

  16. Exchange of volatile organic compounds in the boreal forest floor

    Science.gov (United States)

    Aaltonen, Hermanni; Bäck, Jaana; Pumpanen, Jukka; Pihlatie, Mari; Hakola, Hannele; Hellén, Heidi; Aalto, Juho; Heinonsalo, Jussi; Kajos, Maija K.; Kolari, Pasi; Taipale, Risto; Vesala, Timo

    2013-04-01

    Terrestrial ecosystems, mainly plants, emit large amounts of volatile organic compounds (VOCs) into the atmosphere. In addition to plants, VOCs also have less-known sources, such as soil. VOCs are a very diverse group of reactive compounds, including terpenoids, alcohols, aldehydes and ketones. Due to their high reactivity, VOCs take part in formation and growth of secondary organic aerosols in the atmosphere and thus affect also Earth's radiation balance (Kulmala et al. 2004). We have studied boreal soil and forest floor VOC fluxes with chamber and snow gradient techniques we were developed. Spatial and temporal variability in VOC fluxes was studied with year-round measurements in the field and the sources of boreal soil VOCs in the laboratory with fungal isolates. Determination of the compounds was performed mass spectrometrically. Our results reveal that VOCs from soil are mainly emitted by living roots, above- and belowground litter and microbes. The strongest source appears to be litter, in which both plant residuals and decomposers play a role in the emissions. Soil fungi showed high emissions of lighter VOCs, like acetone, acetaldehyde and methanol, from isolates. Temperature and moisture are the most critical physical factors driving VOC fluxes. Since the environment in boreal forests undergoes strong seasonal changes, the VOC flux strength of the forest floor varies markedly during the year, being highest in spring and autumn. The high spatial heterogeneity of the forest floor was also clearly visible in VOC fluxes. The fluxes of other trace gases (CO2, CH4 and N2O) from soil, which are also related to the soil biological activity and physical conditions, did not show correlations with the VOC fluxes. These results indicate that emissions of VOCs from the boreal forest floor account for as much as several tens of percent, depending on the season, of the total forest ecosystem VOC emissions. This emphasises that forest floor compartment should be taken into

  17. Mirror image hydrocarbons from Tropical and Boreal forests

    Directory of Open Access Journals (Sweden)

    J. Williams

    2007-01-01

    Full Text Available Monoterpenes, emitted in large quantities by trees to attract pollinators and repel herbivores, can exist in mirror image forms called enantiomers. In this study such enantiomeric pairs have been measured in ambient air over extensive forest ecosystems in South America and northern Europe. For the dominant monoterpene, α-pinene, the (−-form was measured in large excess over the (+-form over the Tropical rainforest, whereas the reverse was observed over the Boreal forest. Interestingly, over the Tropical forest (−-α-pinene did not correlate with its own enantiomer, but correlated well with isoprene. The results indicate a remarkable ecosystem scale enantiomeric fingerprint and a nexus between the biosphere and atmosphere.

  18. Local heterogeneity and scaled dependence of eco-hydrology in mire

    Science.gov (United States)

    Nakayama, T.

    2011-12-01

    Japanese governments recently started nature conservation project to restore meandering former river channel in order to prevent invasive forest and to recover original ecosystem because various anthropogenic stressors have caused mire degradation in subarctic northern Japan such as drying and invasion of alder-dominant shrub forest. In order to predict effectiveness of this restoration, the author has so far developed the process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a, 2008b, 2010, 2011a, 2011b; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Watanabe, 2004, 2006, 2008a, 2008b; Nakayama et al., 2006, 2007, 2010, 2011), which includes complex interactions between canopy, surface water, unsaturated water, aquifer, lake, and rivers. Because the model simulates the hydrologic cycle, elevation change, and vegetation succession processes iteratively including competition between native reed-sedge vegetation and invasive alder, it is possible to estimate nonlinear interaction between hydro-geomorphic and vegetation dynamics. In this study, the author further improved the model to evaluate positive feedback between heterogeneous drying and alder invasion in relation to stability and regime shift beyond previous researches about constant slope and its relation to regular pattern. In particular, he evaluated local heterogeneity of groundwater and surface water in both horizontal and vertical directions, and clarified relationship between microtopography about ridge-depression and hydrologic cycle about divergence-convergence in short-term period. This mechanism is also related to interaction between groundwater and inundated flow, scaled dependence of hydrologic cycle, and its effect on sediment deposition and vegetation change. These results will throw some light on two conflicting conceptualizations of peatland hydrology, so-called, shallow-flow and groundwater-flow models (Reeve et al., 2000), and bring

  19. Methane metabolism in a stratified boreal lake

    Science.gov (United States)

    Nykänen, Hannu; Peura, Sari; Kankaala, Paula; Jones, Roger

    2013-04-01

    Stratified lakes, typical of the boreal zone, are naturally anoxic from their bottoms. In these lakes methanogenesis can account for up to half of organic matter degradation. However, a major part of the methane (CH4) is oxidized in the water column before reaching the atmosphere. Since methanotrophs use CH4 as their sole carbon and energy source, much CH4-derived carbon is incorporated into their biomass. Microbially produced CH4 has strongly negative δ13C compared to other carbon forms in ecosystems, making it possible to follow its route in food webs. However, only a few studies have estimated the amount of this microbial biomass or its carbon stable isotopic composition due to difficulties in separating it from other biomass or from other carbon forms in the water column. We estimated methanotrophic biomass from measured CH4 oxidation, and δ13C of the biomass from measured δ13C values of CH4, DIC, POM and DOC. An estimate of the fraction of methanotrophs in total microbial biomass is derived from bacterial community composition measurements. The study was made in, Alinen Mustajärvi, a small (area 0.75 ha, maximum depth 6.5 m, mean depth 4.2 m,), oligotrophic, mesohumic headwater lake located in boreal coniferous forest in southern Finland. CH4 and DIC concentrations and their δ13C were measured over the deepest point of the lake at 1 m intervals. 13C of DOM and POM were analyzed from composite samples from epi-, meta-, and hypolimnion. Evasion of CH4 and carbon dioxide from the lake surface to the atmosphere was estimated with boundary layer diffusion equations. CH4oxidation was estimated by comparing differences between observed concentrations and CH4potentially transported by turbulent diffusion between different vertical layers in the lake and also by actual methanotrophy measurements and from vertical differences in δ13C-CH4. The estimate of CH4 production was based on the sum of oxidized and released CH4. Molecular microbiology methods were used to

  20. Latent heat exchange in the boreal and arctic biomes.

    Science.gov (United States)

    Kasurinen, Ville; Alfredsen, Knut; Kolari, Pasi; Mammarella, Ivan; Alekseychik, Pavel; Rinne, Janne; Vesala, Timo; Bernier, Pierre; Boike, Julia; Langer, Moritz; Belelli Marchesini, Luca; van Huissteden, Ko; Dolman, Han; Sachs, Torsten; Ohta, Takeshi; Varlagin, Andrej; Rocha, Adrian; Arain, Altaf; Oechel, Walter; Lund, Magnus; Grelle, Achim; Lindroth, Anders; Black, Andy; Aurela, Mika; Laurila, Tuomas; Lohila, Annalea; Berninger, Frank

    2014-11-01

    In this study latent heat flux (λE) measurements made at 65 boreal and arctic eddy-covariance (EC) sites were analyses by using the Penman-Monteith equation. Sites were stratified into nine different ecosystem types: harvested and burnt forest areas, pine forests, spruce or fir forests, Douglas-fir forests, broadleaf deciduous forests, larch forests, wetlands, tundra and natural grasslands. The Penman-Monteith equation was calibrated with variable surface resistances against half-hourly eddy-covariance data and clear differences between ecosystem types were observed. Based on the modeled behavior of surface and aerodynamic resistances, surface resistance tightly control λE in most mature forests, while it had less importance in ecosystems having shorter vegetation like young or recently harvested forests, grasslands, wetlands and tundra. The parameters of the Penman-Monteith equation were clearly different for winter and summer conditions, indicating that phenological effects on surface resistance are important. We also compared the simulated λE of different ecosystem types under meteorological conditions at one site. Values of λE varied between 15% and 38% of the net radiation in the simulations with mean ecosystem parameters. In general, the simulations suggest that λE is higher from forested ecosystems than from grasslands, wetlands or tundra-type ecosystems. Forests showed usually a tighter stomatal control of λE as indicated by a pronounced sensitivity of surface resistance to atmospheric vapor pressure deficit. Nevertheless, the surface resistance of forests was lower than for open vegetation types including wetlands. Tundra and wetlands had higher surface resistances, which were less sensitive to vapor pressure deficits. The results indicate that the variation in surface resistance within and between different vegetation types might play a significant role in energy exchange between terrestrial ecosystems and atmosphere. These results suggest the need

  1. Investigations of boreal forest bidirectional reflectance factor

    Science.gov (United States)

    White, H. Peter

    view/illumination geometries. Forward mode validation of FLAIR demonstrates its ability to reproduce canopy reflectance values using reasonable canopy properties as input. Inversion of FLAIR to produce a canopy BRF function based on a limited number of observed reflectance values indicate the model's ability to characterize boreal canopy BRF. Difficulties are found with hotspot reflectance values when the modelled BRF function is extrapolated to illumination angles significantly beyond those associated with the observed reflectance. Data for this research was obtained as part of the BOReal Atmosphere-Ecosystem Study (BOREAS), with BRF of various pure canopy stands obtained during five periods of the year (winter, thaw, late spring, mid-summer, and early autumn). Airborne spectral imagery was acquired using the Compact Airborne Spectrographic Imager (CASI). The sensor mount allows multiple view directions ranging from +45° to -45°, and was flown along, perpendicular to, and at 45° to the solar illumination plane. This provides full resolution multi- angular imagery ( ~ 2 x 2 meters) with relevant spectral bands for a significant angular sampling of canopy BRF. Nadir viewing understorey reflectance data was also obtained using field spectrometers.

  2. How a Sphagnum fuscum-dominated bog changed into a calcareous fen : the unique Holocene history of a Slovak spring-fed mire

    NARCIS (Netherlands)

    Hajkova, Petra; Grootjans, A. B.; Lamentowicz, Mariusz; Rybnickova, Eliska; Madaras, Mikulas; Opravilova, Vera; Michaelis, Dierk; Hajek, Michal; Joosten, Hans; Wolejko, Leslaw; Rybníčková, Eliška; Madaras, Mikuláš; Opravilová, Věra; Wołejko, Lesław; Hajkova, T.

    2012-01-01

    In general, mires develop by autogenic succession from more groundwater-fed to more rainwater-fed. This study from a calcareous mire in the West Carpathians (Slovakia) describes a similar development in the Early Holocene, followed by a reverse development in the Middle and Late Holocene. Pollen, ma

  3. Characterisation of Holocene plant macrofossils from North Spanish ombrotrophic mires: bryophytes

    Directory of Open Access Journals (Sweden)

    M. Souto

    2017-01-01

    Full Text Available The methods and criteria used for the identification of bryophytes from the peat deposits of four ombrotrophic mires in northern Spain are presented. Two liverworts and fifteen moss taxa were recorded. Twelve were identified to species level, two to genus level (Polytrichum sp., Campylopus sp. and another to section level (Sphagnum sect. Acutifolia. All taxa were identified from their vegetative remains, mainly leaves. Only sporangia of Sphagnum species were recorded. Descriptions of the most relevant characters for taxa identifications are shown, accompanied by illustrations that facilitate their interpretation. A dichotomous identification key is also provided.

  4. The calcareous mires in South-East Poland are home to two rare Anthracoidea species

    Directory of Open Access Journals (Sweden)

    Marcin Piątek

    2013-12-01

    Full Text Available The new collections of Anthracoidea buxbaumii Kukkonen on Carex buxbaumii Wahlenb. and Anthracoidea hostianae B.Lindeb. ex Nannf. on Carex lepidocarpa Tausch recorded in the calcareous mires in South-East Poland are described, illustrated and discussed. The holotype of the latter smut is also re-examined, described and illustrated in detail. Anthracoidea buxbaumii is reported for the second time from Poland on a new host plant. Anthracoidea hostianae is new to Poland. The variability of spore sizes of both species is discussed. The conspecificity of Anthracoidea buxbaumii and A. hostianae suggested in the literature is analyzed.

  5. Surface energy balance of subarctic lowland palsa mires related to permafrost degradation

    Science.gov (United States)

    Stiegler, C.; Lindroth, A.; Johansson, M.

    2013-12-01

    During the last decades, an accelerating trend in increasing active-layer thickness and rising permafrost temperatures has been observed in the Nordic area. One region, where permafrost is particularly vulnerable to any further climate change is the Torneträsk area in northern subarctic Sweden. Within the next decades a projected ongoing climate warming and increase in snow cover will most likely lead to the disappearance of lowland permafrost in this region, affecting surface vegetation cover, greenhouse gas emissions and surface energy balance. In this study we link first results of surface energy balance measurements from lowland palsa mires in the Torneträsk region to the current state of permafrost and the degradation of peat plateaus. The study area covers several mires with similar local topographic conditions along an east-west oriented transect. Due to a strong climatic gradient, with maritime climate in the west and a more continental climate in the east, active layer thickness and permafrost temperatures generally increase from east to west while permafrost thickness decreases. In the recent years permafrost has fully disappeared at our westernmost study site while at the other investigated locations the peat plateaus show varying stages of degradation. For our measurements of energy balance components we use both a mobile energy balance tower and a stationary eddy covariance tower. Data has been collected during the growing season in 2013 by measuring all components of the surface energy budget, i.e. net radiation, turbulent fluxes of sensible and latent heat as well as ground heat fluxes. In addition, we measure active layer thickness and both soil moisture and soil temperature at various depths. First results display that the turbulent fluxes of latent heat exceed the fluxes of sensible heat at all investigated sites. The difference is more pronounced at those mires where permafrost degradation is at an advanced stage and therefore more open water

  6. The summertime Boreal forest field measurement intensive (HUMPPA-COPEC-2010): an overview of meteorological and chemical influences

    NARCIS (Netherlands)

    Williams, J.; Crowley, J.; Fischer, H.; Harder, H.; Martinez, M.; Ouwersloot, H.G.; Vilà-Guerau de Arellano, J.; Ganzeveld, L.N.; Lelieveld, J.

    2011-01-01

    This paper describes the background, instrumentation, goals, and the regional influences on the HUMPPACOPEC intensive field measurement campaign, conducted at the Boreal forest research station SMEAR II (Station for Measuring Ecosystem-Atmosphere Relation) in Hyyti¨al¨a, Finland from 12 July–12 Augu

  7. Phase and amplitude of ecosystem carbon release and uptake potentials as derived from FLUXNET measurements

    DEFF Research Database (Denmark)

    Falge, E.; Tenhunen, J.; Baldocchi, D.;

    2002-01-01

    boreal and temperate. deciduous and coniferous forests, Mediterranean evergreen systems, rainforest, native and managed temperate grasslands, tundra, and C-3 and C-4 crops. Generalization of seasonal patterns are useful for identifying functional vegetation types for global dynamic vegetation models...... mainly on Northern Hemisphere temperate and boreal forest ecosystems. Grasslands, crops, Mediterranean ecosystems, and rainforests are under-represented. as are savanna systems, wooded grassland, shrubland, or year-round measurements in tundra systems. For regional or global estimates of carbon...

  8. Regional-scale surface flux observations across the boreal forest during BOREAS

    DEFF Research Database (Denmark)

    Oncley, S.P.; Lenschow, D.H.; Campos, T.L.;

    1997-01-01

    study area to the subarctic tundra. Typical midsummer, midday, large-scale net ecosystem exchanges of carbon dioxide were about -10 mu mol m(-2) s(-1) for primarily deciduous forests, about -6 mu mol m(-2) s(-1) for the primarily coniferous regions between and including the two BOREAS study areas......A major role of the National Center for Atmospheric Research (NCAR) Electra aircraft during the Boreal Ecosystem-Atmosphere Study (BOREAS) was to measure fluxes of momentum, sensible and latent heat, carbon dioxide, and ozone on a transect that crossed the entire boreal forest biome....... The observations spanned the growing season (late May to mid-September 1994) and extended the fluxes obtained in two intensive study areas to larger spatial scales to help provide a data set that is useful for comparison with and validation of large-scale models and satellite retrievals. We found the deciduous...

  9. Nitrogen cycling in the upland boreal shield forest : response to an experimental addition of nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Lamontagne, S.

    1998-12-31

    The industrial and agricultural releases of nitrogen gases into the atmosphere has significantly increased the load of nitrogen in many forested ecosystems. This study examined the threat of nitrogen saturation which can cause freshwater acidification and forest decline. The nitrogen cycle in small upland boreal shield catchments at the Experimental Lake Area in northwestern Ontario was described and the process involved in nitrogen retention in this system using an experimental addition of NO{sub 3} was studied. It was determined that in the short-term, the upland boreal shield is limited in preventing nitrogen-based acidification of downstream ecosystems because of a weak potential for nitrogen retention during part of the year and because of the intrinsic nitrogen saturation of part of the landscape.

  10. Monitoring Current Status of and Trends in Boreal Forest Land Use in Russian Karelia

    Directory of Open Access Journals (Sweden)

    Erkki Tomppo

    2003-12-01

    Full Text Available Some of the last remaining near-natural boreal forest landscapes in northern Europe can be found in the Russian Karelia near its border with Finland. Currently, these forests are facing strong exploitation pressure in the form of extensive clearcuts. Demand for conservation is also high. We characterize the boreal forest landscape in the region and assess the impacts of past and potential management actions through a mapping and modeling study that synthesizes methods from landscape ecology, remote sensing, and simulation modeling. The forests of the study area were mapped using techniques for interpreting multitemporal satellite images and detecting changes. The species composition and structure of the forests were estimated using the multisource k-nearest neighbors (k-nn method. Forest harvesting rates and current landscape patterns were used to parameterize models built with a cell-based Spatially Explicit Landscape Event Simulator (SELES modeling tool, and alternative land-use policy strategies were simulated with and without natural fire. Based on 10 Monte Carlo runs for each scenario, we can predict dramatic changes in the forest landscape structure after 30–70 yr. The current, complexly structured, near-natural forest assemblage will rapidly be converted into its transpose: an expanse of young regeneration stands, with blocks of near-natural forest extant only as islands within mires and in the reserve areas. The prompt establishment of the proposed Kalevala National Park is regionally important for these reasons: (1 to increase the types of near-natural forest conserved, (2 to provide a second large biodiversity source adjacent to the heavily fragmented Finnish forests, and (3 to reduce the currently inflated rate of harvesting.

  11. Anthropogenic nitrogen deposition enhances carbon sequestration in boreal soils.

    Science.gov (United States)

    Maaroufi, Nadia I; Nordin, Annika; Hasselquist, Niles J; Bach, Lisbet H; Palmqvist, Kristin; Gundale, Michael J

    2015-08-01

    It is proposed that carbon (C) sequestration in response to reactive nitrogen (Nr ) deposition in boreal forests accounts for a large portion of the terrestrial sink for anthropogenic CO2 emissions. While studies have helped clarify the magnitude by which Nr deposition enhances C sequestration by forest vegetation, there remains a paucity of long-term experimental studies evaluating how soil C pools respond. We conducted a long-term experiment, maintained since 1996, consisting of three N addition levels (0, 12.5, and 50 kg N ha(-1) yr(-1) ) in the boreal zone of northern Sweden to understand how atmospheric Nr deposition affects soil C accumulation, soil microbial communities, and soil respiration. We hypothesized that soil C sequestration will increase, and soil microbial biomass and soil respiration will decrease, with disproportionately large changes expected compared to low levels of N addition. Our data showed that the low N addition treatment caused a non-significant increase in the organic horizon C pool of ~15% and a significant increase of ~30% in response to the high N treatment relative to the control. The relationship between C sequestration and N addition in the organic horizon was linear, with a slope of 10 kg C kg(-1) N. We also found a concomitant decrease in total microbial and fungal biomasses and a ~11% reduction in soil respiration in response to the high N treatment. Our data complement previous data from the same study system describing aboveground C sequestration, indicating a total ecosystem sequestration rate of 26 kg C kg(-1) N. These estimates are far lower than suggested by some previous modeling studies, and thus will help improve and validate current modeling efforts aimed at separating the effect of multiple global change factors on the C balance of the boreal region.

  12. Mires and Histosols in French Guiana (South America: new data relating to location and area

    Directory of Open Access Journals (Sweden)

    F. Muller

    2013-05-01

    Full Text Available Large peatland areas have been identified in French Guiana, an equatorial province (département of France, but the exact distribution and ecological condition of mires is not well known. Maps of pedological and agronomic units that were prepared between the early 1950s and 1975 enable us to improve on previously published estimates of Histosol areas in French Guiana. Only the non-forested parts of the province have been studied because there are hardly any pedological maps for the portion that lies within the Amazon rainforest. The extent of Histosols recorded in French Guiana is around 975 km², which is 57–60 % of the estimates of peatland area (1620 km² and 1720 km² reported in the scientific literature. The largest Histosol areas are located near the coast in the north-east of the province, between Cayenne and the border with Brazil. This region receives the highest annual rainfall recorded in French Guiana and provides a particularly favourable hydro-geomorphological setting for peat formation. It will be necessary to explore these large Histosol areas in order to characterise them and to study the associated mire vegetation. Difficult access, combined with the adverse hydro-climatic conditions, will make this a long-term endeavour.

  13. Perawatan Gigitan Silang Gigi Depan pada Gigi Susu dengan Dataran Gigitan Miring Akrilik Cekat

    Directory of Open Access Journals (Sweden)

    Wayan Ardhana

    2016-10-01

    Full Text Available Latar Belakang: Gigitan silang gigi depan jika dibiarkan berkembang akan dapat mengakibatkan terhambatnya pertumbuhan maksila dan tidak terkontrolnya pertumbuhan mandibula ke depan sehingga dapat menjadi maloklusi skeletal kelas III yang sangat merusak penampilan wajah. Perawatan sangat perlu dilakukan pada usia dini sejak periode gigi susu. Tujuan: Membahas perawatan gigitan silang gihi depan pada gigi susu menggunakan dataran gigitan miring dari resin akrilik yang dipasang secara cekat pada rahang bawah. Kasus: Dua kasus maloklusi pseuid kelas III dengan gigitan silang gigi depan pada periode gigi susu. Dirawat menggunakan dataran gigitan miring akrilik yang dipasang secara cekat pada gigi depan bawah. Kesimpulan: maloklusi dapat terkoreksi dalam waktu 2 bulan, oklusi dapat dikembalikan ke relasi normalnya dan tetap dalam keadaan normal saat dilakukan observasi ketika semua gigi depan permanen telah erupsi.   Background: Untreated anterior crossbite will be able to inhibit the maxillary growth and subsquent uncontrolled forward growth of the mandible can lead to class III skeletal malocclusion and therefore an unattractive appearance. Care needs to be done at a very early age and can be started during primary dentition period. Objectives: Discussing the treatment anterior crossbite of primary dentition using fixed acrylic mandibulary inclined bite plane. Cases: Two cases of pesudo class III malocclusion with anterior crossbite of primary dentition have been treated using fixed acrylic bite plane mounted on the lower front teeth. Conclusion: Malocclusion can be corrected in 2 months, and normal occlusion can be restored and remained stable when all the permanent anterior teeth had been erupted.

  14. Phosphorus limitation controls rates of biological N2-fixation in boreal peatlands

    Science.gov (United States)

    Dynarski, K. A.; Wieder, R.; Vile, M. A.

    2013-12-01

    N2-fixation, once thought to occur at negligible rates in pristine boreal peatlands, has recently been demonstrated to be the dominant input of nitrogen (N) to these ecosystems. The controls of biological N2-fixation in pristine boreal peatlands are not well understood, but limitation of the nutrients molybdenum (Mo) and phosphorus (P) may play a key role. Because the enzyme nitrogenase requires molybdenum-containing cofactors to function, biological N2-fixation may be limited by the trace metal molybdenum. Recent studies have shown that Mo limits nitrogen fixation rates in tropical soils. P availability may also be important in regulating N2-fixation rates; N2-fixation is a P-intensive process because the nitrogenase enzyme is rich in P, and P is likely to be the most limiting nutrient to boreal peatland productivity, next to N. In this study, we examined the role of Mo and P limitation in controlling rates of biological N2-fixation in boreal peatlands. We applied Mo and P nutrient amendments equivalent to 5 mg m-2 yr-1and 10 kg ha-1 yr-1 respectively, both alone and in combination, to fifteen 0.36 m2 plots in a pristine Alberta fen throughout the summer 2013 growing season. We periodically assessed N2-fixation rates in Sphagnum angustifolium moss samples using the acetylene reduction assay with subsequent calibration using 15N2. We found a significant overall treatment effect (F3,44=15.62, pTukey's HSD indicates that N2-fixation rates were significantly higher in plots receiving P additions relative to control plots. However, Mo additions had no effect on N2-fixation rates. These results indicate that P, not Mo, availability is dominant in controlling rates of biological N2-fixation in boreal peatland ecosystems.

  15. Nitrogen balance of a boreal Scots pine forest

    Directory of Open Access Journals (Sweden)

    J. F. J. Korhonen

    2012-08-01

    Full Text Available The productivity of boreal forests is considered to be limited by low nitrogen (N availability. Increased atmospheric N deposition has altered the functioning and N cycling of these N-sensitive ecosystems. The most important components of N pools and fluxes were measured in a boreal Scots pine stand in Hyytiälä, Southern Finland. The measurement at the site allowed direct estimations of nutrient pools in the soil and biomass, inputs from the atmosphere and outputs as drainage flow and gaseous losses from two micro-catchments. N was accumulating to the system with a rate of 7 kg N ha−1 yr−1. Nitrogen input as atmospheric deposition was 7.4 kg N ha−1 yr−1. Dry deposition and organic N in wet deposition contributed over half of the input in deposition. Total outputs were 0.4 kg N ha−1 yr−1, the most important outputs being N2O emission to the atmosphere and organic N flux in drainage flow. Nitrogen uptake and retranslocation were as important sources of N for plant growth. Most of the uptaken N originated from decomposition of organic matter, and the fraction of N that could originate directly from deposition was about 30%. In conclusion, atmospheric N deposition fertilizes the site considerably.

  16. 长白山圆池泥炭沼泽演变及环境信息记录%The Evolution and Environment Archives of Yuanchi Peat Mires in Changbai Mountains

    Institute of Scientific and Technical Information of China (English)

    张彦; 史彩奎; 王健; 马小凡; 吕宪国; 王国平

    2012-01-01

    通过分析长白山圆池泥炭剖面总有机碳含量、总正构烷烃含量、奇偶优势指数、(C23+C25)含量和2C31/(C27+C29)比值,讨论了泥炭发育不同时期植物输入情况,同时结合210Pb测年建立的年代序列来探讨该区的气候变化规律.研究结果显示,约1400年前,气候干冷,圆池尚没有出现沼泽化;1400年开始,气候稍暖,少量植物输入,圆池开始沼泽化;约从1860年至今,气候逐步转暖,大量植物输入,圆池沼泽化速度加快.%Peatl mire is formed by decayed wetland plants, which were accumulated for a long time. It is a good geological archive to get information about surrounding environment, thus, it could preserve the high resolution informations that from deposition layers. Plant species and growth are controlled by climate change, so, organic compounds in peat could reflect vegetation succession of plants' residue and then reveal the characteristics of climate and development of peat mires. Peat mires are important ecosystem and distributed widely in the Changbai Mountains, but they have received less attention than other ecosystems because away from industrial area. So it was less affected by human activities. Above those reasons, peat mires in Changbai Mountains are ideal area to gain information about environmental change. The study discussed the vegetation succession of peatlands in different development periods by analyzing total organic carbon content, normal al-kanes content, odd-even predominance index, content of (C23+C25) value of 2C31/(C27+C29) in peat profiles, of Yuanchi peatland in Changbai Mountains. Meanwhile, the history of climate change in this area was discussed by combining with 210Pb dating. It turned out that, in about 1400, the lake in Yuanchi was not in a palustrine process, due to the cold and dried climate; then the temperature was slightly warm, it began a palustrine process with less vegetation inputting; so far, in 1860, climate became wanner gradually

  17. Landscape control of uranium and thorium in boreal streams – spatiotemporal variability and the role of wetlands

    Directory of Open Access Journals (Sweden)

    F. Lidman

    2012-11-01

    Full Text Available The concentrations of uranium and thorium in ten partly nested streams in the boreal forest region were monitored over a two-year period. The investigated catchments ranged from small headwaters (0.1 km2 up to a fourth-order stream (67 km2. Considerable spatiotemporal variations were observed, with little or no correlation between streams. The fluxes of both uranium and thorium varied substantially between the subcatchments, ranging from 1.7 to 30 g km−2 a−1 for uranium and from 3.2 to 24 g km−2 a−1 for thorium. Airborne gamma spectrometry was used to measure the concentrations of uranium and thorium in surface soils throughout the catchment, suggesting that the concentrations of uranium and thorium in mineral soils are similar throughout the catchment. The fluxes of uranium and thorium were compared to a wide range of parameters characterising the investigated catchments and the chemistry of the stream water, e.g. soil concentrations of these elements, pH, TOC (total organic carbon, Al, Si and hydrogen carbonate, but it was concluded that the spatial variabilities in the fluxes of both uranium and thorium mainly were controlled by wetlands. The results indicate that there is a predictable and systematic accumulation of both uranium and thorium in boreal wetlands that is large enough to control the transport of these elements. On the landscape scale approximately 65–80% of uranium and 55–65% of thorium entering a wetland were estimated to be retained in the peat. Overall, accumulation in mires and other types of wetlands was estimated to decrease the fluxes of uranium and thorium from the boreal forest landscape by 30–40%, indicating that wetlands play an important role for the biogeochemical cycling of uranium and thorium in the boreal forest landscape. The atmospheric deposition of uranium and thorium was also quantified, and its contribution to boreal streams was

  18. High-resolution records detect human-caused changes to the boreal forest wildfire regime in interior Alaska

    Science.gov (United States)

    Gaglioti, Benjamin V.; Mann, Daniel H.; Jones, Benjamin M.; Wooller, Matthew J.; Finney, Bruce P.

    2016-01-01

    Stand-replacing wildfires are a keystone disturbance in the boreal forest, and they are becoming more common as the climate warms. Paleo-fire archives from the wildland–urban interface can quantify the prehistoric fire regime and assess how both human land-use and climate change impact ecosystem dynamics. Here, we use a combination of a sedimentary charcoal record preserved in varved lake sediments (annually layered) and fire scars in living trees to document changes in local fire return intervals (FRIs) and regional fire activity over the last 500 years. Ace Lake is within the boreal forest, located near the town of Fairbanks in interior Alaska, which was settled by gold miners in AD 1902. In the 400 years before settlement, fires occurred near the lake on average every 58 years. After settlement, fires became much more frequent (average every 18  years), and background charcoal flux rates rose to four times their preindustrial levels, indicating a region-wide increase in burning. Despite this surge in burning, the preindustrial boreal forest ecosystem and permafrost in the watershed have remained intact. Although fire suppression has reduced charcoal influx since the 1950s, an aging fuel load experiencing increasingly warm summers may pose management problems for this and other boreal sites that have similar land-use and fire histories. The large human-caused fire events that we identify can be used to test how increasingly common megafires may alter ecosystem dynamics in the future.

  19. Sources of spatial variation in methane emission from mires in northern Sweden: A mechanistic approach in statistical modeling

    Science.gov (United States)

    Granberg, Gunnar; Mikkelä, Catharina; Sundh, Ingvar; Svensson, Bo H.; Nilsson, Mats

    1997-06-01

    Methane emissions from six mires in northern Sweden were measured using a closed chamber technique during the frost free season in 1992. The average methane flux over the measurement period, calculated either for each mire or for different plant communities within one mire, ranged from 9 to 83 mg CH4 m-2 d-1. The emission rate on each occasion was related to physical and chemical environmental variables, both in a general data set for all mires (n = 836) and in subdata sets for individual mires, using multiple linear regression. The variables with significant contributions to the models were water table, standing water above the vegetation surface, peat temperatures, and principal components of the near infrared reflectance spectra of peat samples reflecting variations in organic chemical composition. To account for the actual contribution of methane production and methane oxidation, variables describing the active parts of the vertically distributed potentials of methane production or oxidation were constructed. The interaction terms between these variables, respectively, describing the active proportion of methanogens and methanotrophs, and the temperature values representing the anoxic and oxic parts of the profile were significantly correlated to the methane emission rate; positively for the production zone and negatively for the consumption zone. By using this mechanistic approach, a significant temperature effect in both the methane production and consumption zone was detected. These constructed temperature variables explain 21% of the variance in the logarithmically transformed methane fluxes using the entire data set (n = 836) but only 5% of the variance using peat temperatures from fixed depths. Adding variables describing the organic chemical composition of the peat to the models improved the predictability in 10 of the 11 model sets tested, decreasing the unexplained variance by maximally 50% for a poor fen community model and increasing R2 from 0.40 to

  20. Spatially explicit estimation of aboveground boreal forest biomass in the Yukon River Basin, Alaska

    Science.gov (United States)

    Ji, Lei; Wylie, Bruce K.; Brown, Dana R. N.; Peterson, Birgit E.; Alexander, Heather D.; Mack, Michelle C.; Rover, Jennifer R.; Waldrop, Mark P.; McFarland, Jack W.; Chen, Xuexia; Pastick, Neal J.

    2015-01-01

    Quantification of aboveground biomass (AGB) in Alaska’s boreal forest is essential to the accurate evaluation of terrestrial carbon stocks and dynamics in northern high-latitude ecosystems. Our goal was to map AGB at 30 m resolution for the boreal forest in the Yukon River Basin of Alaska using Landsat data and ground measurements. We acquired Landsat images to generate a 3-year (2008–2010) composite of top-of-atmosphere reflectance for six bands as well as the brightness temperature (BT). We constructed a multiple regression model using field-observed AGB and Landsat-derived reflectance, BT, and vegetation indices. A basin-wide boreal forest AGB map at 30 m resolution was generated by applying the regression model to the Landsat composite. The fivefold cross-validation with field measurements had a mean absolute error (MAE) of 25.7 Mg ha−1 (relative MAE 47.5%) and a mean bias error (MBE) of 4.3 Mg ha−1(relative MBE 7.9%). The boreal forest AGB product was compared with lidar-based vegetation height data; the comparison indicated that there was a significant correlation between the two data sets.

  1. Balancing the Relationship Between Protection and Sustainable Management in Canada′s Boreal Forest

    Directory of Open Access Journals (Sweden)

    Matthew Carlson

    2015-01-01

    Full Text Available Protection and sustainable forest management are related but unique, with protection focusing on minimising risk to ecosystems and sustainable management emphasising economic development. Given these distinct roles, a defining characteristic of the relationship between the two approaches is their relative abundance and distribution. The relationship is currently imbalanced, with only 12% of Canada allocated to protection, indicating that ecological values have historically been traded off in favour of resource production. The intactness of Canada′s boreal forest provides an opportunity for a more holistic approach that conserves its globally significant environmental attributes while also supporting resource production. The Boreal Forest Conservation Framework proposes a balanced relationship that allocates land approximately equally between protection and sustainable management. It is a framework that has been endorsed by industry, Aboriginal, and conservation organisations, and is supported by conservation science. Recent commitments to comprehensive land-use planning at regional scales are consistent with the collaborative approach promoted by the Boreal Forest Conservation Framework, and suggest that conservation objectives are likely to receive increased attention in Canada′s boreal region relative to recent history. Ensuring that land-use planning is proactive and balanced will be essential to forging a cooperative relationship between sustainable management and protection in the region.

  2. The Elusive Boreal Forest Thaumarchaeota

    Directory of Open Access Journals (Sweden)

    Malin Bomberg

    2016-06-01

    Full Text Available In recent years, Archaea have, with increasing frequency, been found to colonize both agricultural and forest soils in temperate and boreal regions. The as yet uncultured group I.1c of the Thaumarchaeota has been of special interest. These Archaea are widely distributed in mature vegetated acidic soils, but little has been revealed of their physiological and biological characteristics. The I.1c Thaumarchaeota have been recognized as a microbial group influenced by plant roots and mycorrhizal fungi, but appear to have distinct features from their more common soil dwelling counterparts, such as the Nitrosotalea or Nitrososphaera. They appear to be highly dependent on soil pH, thriving in undisturbed vegetated soils with a pH of 5 or below. Research indicate that these Archaea require organic carbon and nitrogen sources for growth and that they may live both aerobically and anaerobically. Nevertheless, pure cultures of these microorganisms have not yet been obtained. This review will focus on what is known to date about the uncultured group I.1c Thaumarchaeota formerly known as the “Finnish Forest Soil” (FFS Archaea.

  3. Soligenous wetlands of North-western Poland as an environment for endangered mire species

    Directory of Open Access Journals (Sweden)

    Lesław Wołejko

    2014-01-01

    Full Text Available Environmental conditions and the occurrence of protected and rare species have been studied in 18 groundwater-fed wetland complexes in north-western Poland. The plant cover of studied objects consisted of 81 syntaxa of water-, spring-, rush and sedge-, mire-, meadow-, tall-forb-, willow carr- and alderwood communities, as well as of 4 syntaxa of the mesophytic forests. Their microhabitat differentiation has been discussed. The expression of environmental conditions in the groundwater-fed communities has been analysed on the basis of Ellenberg's indicator values and the occurrence of protected and rare species. A signifficant negative correlation has been found between the occurrence of rare species and the trophy index. The special position of the mesotrophic rich fen communities, concerning their role in preservation of a large number of endangered species, as well as of rare plant communities is emphasized.

  4. Carbon balance and greenhouse gas emissions of subarctic lowland palsa mires related to permafrost degradation.

    Science.gov (United States)

    Stiegler, Christian; Lindroth, Anders; Christensen, Torben R.; Johansson, Margareta

    2014-05-01

    The Torneträsk area in northern subarctic Sweden is particularly vulnerable to any further climate change since it is located on the 0-degree isotherm. Within the next decades a projected ongoing climate warming and increase in snow cover will most likely lead to the disappearance of lowland permafrost in this region, affecting greenhouse gas emissions, surface energy fluxes and vegetation cover. A previous study from the Torneträsk area has resulted in extensive data on the effects of permafrost degradation on surface energy balance. In this study we focus on the effects of different stages of permafrost degradation on carbon balance and emission of greenhouse gases. The study area covers several mires with similar local topographic conditions along an east-west oriented transect. Due to a strong climatic gradient, with maritime climate in the west and a more continental climate in the east, active layer thickness and permafrost temperatures generally increase from east to west while permafrost thickness decreases. In recent years permafrost has completely disappeared at the westernmost study site while at the other investigated locations the peat plateaus show varying stages of degradation. For our measurements we use both mobile and stationary energy balance and eddy covariance towers. Data has been collected during the growing season in 2013 by measuring flux densities of carbon dioxide and water vapour and all components of the surface energy budget, i.e. net radiation, turbulent fluxes of sensible and latent heat as well as ground heat fluxes. In addition, we measure active layer thickness and both soil moisture and soil temperature at various depths. In this study we aim to (A) investigate and better understand the effects of permafrost degradation on the CO2 dynamics in subarctic palsa mires, (B) assess variation in terrestrial CO2 and water vapour flux with changes in vegetation cover and soil moisture, (C) determine possible meteorological and

  5. Disturbance Regimes and Landscape Heterogeneity in the Boreal Forest

    OpenAIRE

    2015-01-01

    The boreal forest circles the high northern latitudes but it is far from a continuous carpet of evergreen trees. Rather, the boreal forest is a patchwork of land cover types in constant flux as they recover from wildfire and then are burned again. This fast turnover of land cover makes the boreal forest particularly susceptible to rapid change in response to climate. Furthermore, the boreal forest is an important component of the climate system that pumps heat into the atmosphere and signi...

  6. Pinus sylvestris as a missing source of nitrous oxide and methane in boreal forest.

    Science.gov (United States)

    Machacova, Katerina; Bäck, Jaana; Vanhatalo, Anni; Halmeenmäki, Elisa; Kolari, Pasi; Mammarella, Ivan; Pumpanen, Jukka; Acosta, Manuel; Urban, Otmar; Pihlatie, Mari

    2016-01-01

    Boreal forests comprise 73% of the world's coniferous forests. Based on forest floor measurements, they have been considered a significant natural sink of methane (CH4) and a natural source of nitrous oxide (N2O), both of which are important greenhouse gases. However, the role of trees, especially conifers, in ecosystem N2O and CH4 exchange is only poorly understood. We show for the first time that mature Scots pine (Pinus sylvestris L.) trees consistently emit N2O and CH4 from both stems and shoots. The shoot fluxes of N2O and CH4 exceeded the stem flux rates by 16 and 41 times, respectively. Moreover, higher stem N2O and CH4 fluxes were observed from wet than from dry areas of the forest. The N2O release from boreal pine forests may thus be underestimated and the uptake of CH4 may be overestimated when ecosystem flux calculations are based solely on forest floor measurements. The contribution of pine trees to the N2O and CH4 exchange of the boreal pine forest seems to increase considerably under high soil water content, thus highlighting the urgent need to include tree-emissions in greenhouse gas emission inventories.

  7. Glyphosate in northern ecosystems.

    Science.gov (United States)

    Helander, Marjo; Saloniemi, Irma; Saikkonen, Kari

    2012-10-01

    Glyphosate is the main nonselective, systemic herbicide used against a wide range of weeds. Its worldwide use has expanded because of extensive use of certain agricultural practices such as no-till cropping, and widespread application of glyphosate-resistant genetically modified crops. Glyphosate has a reputation of being nontoxic to animals and rapidly inactivated in soils. However, recent evidence has cast doubts on its safety. Glyphosate may be retained and transported in soils, and there may be cascading effects on nontarget organisms. These processes may be especially detrimental in northern ecosystems because they are characterized by long biologically inactive winters and short growing seasons. In this opinion article, we discuss the potential ecological, environmental and agricultural risks of intensive glyphosate use in boreal regions.

  8. Synchronous phase-demodulation of concentric-rings Placido mires in corneal topography and wavefront aberrometry (theoretical considerations)

    CERN Document Server

    Servin, Manuel

    2012-01-01

    This paper presents a digital interferometric method to demodulate Placido fringe patterns. This method uses a computer-stored conic-wavefront as reference carrier. Even though, Placido mires are widely used in corneal topographers. This is not however a paper on corneal topography and/or its clinical use. This paper focuses on the theoretical aspects to phase-demodulate Placido mires using synchronous interferometric techniques. Placido patterns may also be applied to test optical wavefronts using a Placido-Hartmann opaque plate with periodic annular apertures. This test is sensitive to the radial slope of the measuring wavefront. Another wavefront testing approach may use a Placido-Hartmann-Shack screen with a periodic array of toroidal lenslets. This periodic screen is sensitive to the wavefront's radial-slope at the focal plane of the lenslets. In brief, digital interferometric methods are herein applied for the first time to demodulate conic-carrier Placido images. Finally it should be mentioned that thi...

  9. Biomass and nutrient cycle in fertilized and unfertilized pine, mixed birch and pine and spruce stands on a drained mire.

    OpenAIRE

    Finér, Leena

    1989-01-01

    Biomass, biomass increment and nutrient cycling were studied in (1) a Scots pine (Pinus sylvestris) stand, (2) a Norway spruce (Picea abies) stand and (3) a mixed birch (Betula pubescens)/pine stand on a drained mire at Ilomantsi, eastern Finland in 1979-85. In addition, the effect of NPK and micronutrient fertilizer treatment was studied. Above-ground and root measurements were taken. These data formed the basis of stand biomass and nutrient cycle simulations of fertilized and unfertilized s...

  10. Linear disturbances in boreal peatlands: Hotspots of methane emission

    Science.gov (United States)

    Strack, Maria

    2016-04-01

    Across Canada's boreal forest, at least 600,000 km of linear disturbances including cutlines and roads crisscross the landscape to facilitate resource exploration and extraction. As the boreal forest consists of up to 50% peatland, many of these linear disturbances also cross peatland ecosystems. Although more permanent access roads may involve the placement of mineral soil fill, most linear disturbances only involve clearing the area of trees to allow the passage of equipment and vehicles. This change in canopy cover and the compression of the peat by heavy equipment alters local thermal, hydrological and ecological conditions, likely changing greenhouse gas flux on the disturbance and possibly in the adjacent peatland. I studied CO2 and CH4 along triplicate transects crossing a winter road through a poor fen near Peace River, Alberta, Canada. Sample plots were located 1, 5 and 10 m from the road on both upstream and downstream sides with an additional three plots in the centre of the road. Productivity of the overstory trees, when present, was also determined. The winter road thawed earlier, had a shallower water table and a significantly higher graminoid cover than the adjacent peatland. Tree productivity and CO2 varied between the plots in the adjacent peatland, but there was no clear pattern in relation to distance from the road. The plots on the winter road acted as a greater or similar sink of CO2 as the adjacent peatland, depending on the specific conditions at the study plot. The most significant change was a substantial increase in CH4 emissions, with plots on the winter road emitting on average (standard deviation) 1100 (550) mg CH4 m-2 d-1 compared to 49 (73) mg CH4 m-2 d-1 in the adjacent peatland. Since the hydrologic impact of cutlines is likely less than winter roads, the increase in CH4 efflux may not be as extreme in all cases. Nonetheless, assuming that peatland accounts for ˜30% of the boreal region and a 150 day emission period for CH4, and a

  11. Nitrogen balance of a boreal Scots pine forest

    Directory of Open Access Journals (Sweden)

    J. F. J. Korhonen

    2013-02-01

    Full Text Available The productivity of boreal forests is considered to be limited by low nitrogen (N availability. Increased atmospheric N deposition has altered the functioning and N cycling of these N-sensitive ecosystems by increasing the availability of reactive nitrogen. The most important components of N pools and fluxes were measured in a boreal Scots pine stand in Hyytiälä, Southern Finland. The measurements at the site allowed direct estimations of nutrient pools in the soil and biomass, inputs from the atmosphere and outputs as drainage flow and gaseous losses from two micro-catchments. N was accumulating in the system, mainly in woody biomass, at a rate of 7 kg N ha−1 yr−1. Nitrogen input as atmospheric deposition was 7.4 kg N ha−1 yr−1. Dry deposition and organic N in wet deposition contributed over half of the inputs in deposition. Total outputs were 0.4 kg N ha−1 yr−1, the most important outputs being N2O emission to the atmosphere and organic N flux in drainage flow. Nitrogen uptake and retranslocation were equally important sources of N for plant growth. Most of the assimilated N originated from decomposition of organic matter, and the fraction of N that could originate directly from deposition was about 30%. In conclusion, atmospheric N deposition fertilizes the site considerably, but there are no signs of N saturation. Further research is needed to estimate soil N2 fluxes (emission and fixation, which may amount up to several kg N ha−1 yr−1.

  12. Estimation of stand-level leaf area for boreal bryophytes.

    Science.gov (United States)

    Bond-Lamberty, Ben; Gower, Stith T

    2007-04-01

    Bryophytes dominate the carbon and nitrogen cycling of many poorly drained terrestrial ecosystems and are important in the vegetation-atmosphere exchange of carbon and water, yet few studies have estimated their leaf area at the stand scale. This study quantified the bryophyte-specific leaf area (SLA) and leaf area index (LAI) in a group of different-aged boreal forest stands in well and poorly drained soils. Species-specific SLA (for three feather mosses, four Sphagnum spp. and Aulacomnium palustre mixed with Tomentypnum nitens) was assessed by determining the projected area using a flatbed scanner and cross-sectional geometry using a dissecting microscope. The hemisurface leaf area was computed as the product of SLA and live biomass and was scaled by coverage data collected at all stands. Pleurozium schreberi dominated the spatial coverage, biomass and leaf area in the well-drained stands, particularly the oldest, while S. fuscum and A. palustre were important in the poorly drained stands. Live moss biomass ranged from 47 to 230 g m(-2) in the well-drained stands dominated by feather mosses and from 102 to 228 g m(-2) in the poorly drained stands. Bryophyte SLA varied between 135 and 473 cm(2) g(-1), for A. palustre and S. capillifolium, respectively. SLA was strongly and significantly affected by bryophyte species, but did not vary between stands; in general, there was no significant difference between the SLA of non-Sphagnum mosses. Bryophyte LAI increased with stand age, peaking at 3.1 and 3.7 in the well and poorly drained stands, respectively; this represented approximately 40% of the overstory LAI in the well-drained stands and 100-1,000% in the poorly drained stands, underscoring the important role bryophytes play in the water and carbon budgets of these boreal forests.

  13. Influence of spring and autumn phenological transitions on forest ecosystem productivit

    NARCIS (Netherlands)

    Richardson, A.D.; Black, T.A.; Ciais, P.; Delbart, N.; Moors, E.J.

    2010-01-01

    We use eddy covariance measurements of net ecosystem productivity (NEP) from 21 FLUXNET sites (153 site-years of data) to investigate relationships between phenology and productivity (in terms of both NEP and gross ecosystem photosynthesis, GEP) in temperate and boreal forests. Results are used to e

  14. Does the creation of a boreal hydroelectric reservoir result in a net change in evaporation?

    Science.gov (United States)

    Strachan, Ian B.; Tremblay, Alain; Pelletier, Luc; Tardif, Simon; Turpin, Christian; Nugent, Kelly A.

    2016-09-01

    Estimates of water consumption from hydroelectricity production are hampered by a lack of common methodological approaches. Studies typically use gross evaporation estimates which do not take into account the evaporative water loss from the pre-flooded ecosystems that would occur without the presence of a reservoir. We evaluate the net change in evaporation following the creation of a hydroelectric reservoir located in the Canadian boreal region. We use a direct measurement technique (eddy covariance) over four different ecosystems to evaluate the pre- and post-flood landscape water flux over a five-year period. The net effect of reservoir creation was to increase evaporation over that of the pre-flooded ecosystem. This change was dependent both on management and differences in the timing of the evaporation with nighttime and autumn contributing strongly to the reservoir evaporation. Managed reduction of water level, and thus the evaporating area, reduced the evaporation.

  15. Holocene variations of wildfire occurrence as a guide for sustainable management of the northeastern Canadian boreal forest

    OpenAIRE

    Ahmed El-Guellab; Hugo Asselin; Sylvie Gauthier; Yves Bergeron; Ali, Adam A.

    2015-01-01

    Background Cumulative impacts of wildfires and forest harvesting can cause shifts from closed-crown forest to open woodland in boreal ecosystems. To lower the probability of occurrence of such catastrophic regime shifts, forest logging must decrease when fire frequency increases, so that the combined disturbance rate does not exceed the Holocene maximum. Knowing how climate warming will affect fire regimes is thus crucial to sustainably manage the forest. This study aimed to provide a guid...

  16. Causes of degradation and erosion of a blanket mire in the southern Pennines, UK

    Directory of Open Access Journals (Sweden)

    D.E. Yeloff

    2006-02-01

    Full Text Available This study investigates the causes of erosion and degradation of March Haigh, a blanket mire in the southern Pennines (UK, over a period of 160 years starting in 1840 AD. Peat samples taken from the site were dated using 210Pb; their humification and magnetic susceptibility were measured; and they were examined for pollen, plant macrofossils and microscopic charcoal. Stratigraphic correlation with a dated ‘master’ sample was achieved using indicators of air pollution (magnetic susceptibility and climate (peat humification. The data were used in conjunction with documentary records to reconstruct past variations in grazing pressure, climate, moorland fires and air pollution. Three major vegetation changes have occurred on the moorland since 1840, namely: (1the disappearance of Sphagnum spp. in the mid 19th century; (2the replacement of Calluna vulgaris by Poaceae as the dominant vegetation type ca. 1918; and (3a reduction in vegetation cover and consequent erosion ca. 1959. The results concur with the findings of other investigations of ecological change in the southern Pennines insofar as degradation of vegetation prior to the mid 20th century appears to have been caused by air pollution, climate change and fire. Following the removal of vegetation by a severe fire during the summer of 1959, unprecedented sheep stocking levels maintained the bare peat surface and thus precipitated extensive erosion.

  17. The conundrum of coal bed thickness: a theory for stacked mire sequences

    Energy Technology Data Exchange (ETDEWEB)

    Shearer, J.C.; Staub, J.R.; Moore, T.A. (Geological Survey of Wyoming, Laramie, WY (United States))

    1994-09-01

    Maximum thicknesses for modern peats have been documented only up to about 20 m, whereas coal beds can often be as much as 90 m thick. Since peat is expected to compact appreciably during burial, there appears to be no modern analogue for the processes which formed thick coal beds, and this seems to challenge the Law of Uniformitarianism. However, the conundrum of coal bed thickness can be resolved by identification of discontinuities in coal beds. Coal beds are generally treated as single entities, created by a continuous process of peat deposition. It is more likely, however, that most thick coal beds are composed of multiple paleo-peat bodies, stacked one upon another, rather than a single paleo-peat body. it is suggested that there are three types of bounding surfaces seen in modern peat bodies that can be used to distinguish individual paleo-peats in coal beds; these bounding surfaces can be recognized both in the field and microscopically. Each of these surfaces represents cessation, or at least extreme slowing, of peat deposition. The presence of these surfaces, and thus stacked mire sequences, in modern and ancient equivalents shows that processes in peat bodies have been similar through time and therefore do not challenge the Law of Uniformitarianism.

  18. Logging and Fire Effects in Siberian Boreal Forests

    Science.gov (United States)

    Kukavskaya, E.; Buryak, L.; Ivanova, G.; Kalenskaya, O.; Bogorodskaya, A.; Zhila, S.; McRae, D.; Conard, S. G.

    2013-12-01

    The Russian boreal zone supports a huge terrestrial carbon pool. Moreover, it is a tremendous reservoir of wood products concentrated mainly in Siberia. The main natural disturbance in these forests is wildfire, which modifies the carbon budget and has potentially important climate feedbacks. In addition, both legal and illegal logging increase landscape complexity and fire hazard. We investigated a number of sites in different regions of Siberia to evaluate the impacts of fire and logging on fuel loads, carbon emissions, tree regeneration, soil respiration, and microbocenosis. We found large variations of fire and logging effects among regions depending on growing conditions and type of logging activity. Partial logging had no negative impact on forest conditions and carbon cycle. Illegal logging resulted in increase of fire hazard, and higher carbon emissions than legal logging. The highest fuel loads and carbon emissions were found on repeatedly burned unlogged sites where first fire resulted in total tree mortality. Repeated fires together with logging activities in drier conditions and on large burned sites resulted in insufficient regeneration, or even total lack of tree seedlings. Soil respiration was less on both burned and logged areas than in undisturbed forest. The highest structural and functional disturbances of the soil microbocenosis were observed on logged burned sites. Understanding current interactions between fire and logging is important for modeling ecosystem processes and for managers to develop strategies of sustainable forest management. Changing patterns in the harvest of wood products increase landscape complexity and can be expected to increase emissions and ecosystem damage from wildfires, inhibit recovery of natural ecosystems, and exacerbate impacts of wildland fire on changing climate and air quality. The research was supported by NASA LCLUC Program, RFBR grant # 12-04-31258, and Russian Academy of Sciences.

  19. Major losses of nutrients following a severe drought in a boreal forest.

    Science.gov (United States)

    Houle, Daniel; Lajoie, Geneviève; Duchesne, Louis

    2016-11-28

    Because of global warming, the frequency and severity of droughts are expected to increase, which will have an impact on forest ecosystem health worldwide(1). Although the impact of drought on tree growth and mortality is being increasingly documented(2-4), very little is known about the impact on nutrient cycling in forest ecosystems. Here, based on long-term monitoring data, we report nutrient fluxes in a boreal forest before, during and following a severe drought in July 2012. During and shortly after the drought, we observed high throughfall (rain collected below the canopy) concentrations of nutrient base cations (potassium, calcium and magnesium), chlorine, phosphorus and dissolved organic carbon (DOC), differing by one to two orders of magnitude relative to the long-term normal, and resulting in important canopy losses. The high throughfall fluxes had repercussions in the soil solution at a depth of 30 cm, leading to high DOC, chlorine and potassium concentrations. The net potassium losses (atmospheric deposition minus leaching losses) following the drought were especially important, being the equivalent of nearly 20 years of net losses under 'normal' conditions. Our data show that droughts have unexpected impacts on nutrient cycling through impacts on tree canopy and soils and may lead to important episodes of potassium losses from boreal forest ecosystems. The potassium losses associated with drought will add to those originating from tree harvesting and from forest fires and insect outbreaks(5-7) (with the last two being expected to increase in the future as a result of climate change), and may contribute to reduced potassium availability in boreal forests in a warming world.

  20. Understanding the Effect of Land Cover Classification on Model Estimates of Regional Carbon Cycling in the Boreal Forest Biome

    Science.gov (United States)

    Kimball, John; Kang, Sinkyu

    2003-01-01

    The original objectives of this proposed 3-year project were to: 1) quantify the respective contributions of land cover and disturbance (i.e., wild fire) to uncertainty associated with regional carbon source/sink estimates produced by a variety of boreal ecosystem models; 2) identify the model processes responsible for differences in simulated carbon source/sink patterns for the boreal forest; 3) validate model outputs using tower and field- based estimates of NEP and NPP; and 4) recommend/prioritize improvements to boreal ecosystem carbon models, which will better constrain regional source/sink estimates for atmospheric C02. These original objectives were subsequently distilled to fit within the constraints of a 1 -year study. This revised study involved a regional model intercomparison over the BOREAS study region involving Biome-BGC, and TEM (A.D. McGuire, UAF) ecosystem models. The major focus of these revised activities involved quantifying the sensitivity of regional model predictions associated with land cover classification uncertainties. We also evaluated the individual and combined effects of historical fire activity, historical atmospheric CO2 concentrations, and climate change on carbon and water flux simulations within the BOREAS study region.

  1. A Changing Number of Alternative States in the Boreal Biome: Reproducibility Risks of Replacing Remote Sensing Products.

    Science.gov (United States)

    Xu, Chi; Holmgren, Milena; Van Nes, Egbert H; Hirota, Marina; Chapin, F Stuart; Scheffer, Marten

    2015-01-01

    Publicly available remote sensing products have boosted science in many ways. The openness of these data sources suggests high reproducibility. However, as we show here, results may be specific to versions of the data products that can become unavailable as new versions are posted. We focus on remotely-sensed tree cover. Recent studies have used this public resource to detect multi-modality in tree cover in the tropical and boreal biomes. Such patterns suggest alternative stable states separated by critical tipping points. This has important implications for the potential response of these ecosystems to global climate change. For the boreal region, four distinct ecosystem states (i.e., treeless, sparse and dense woodland, and boreal forest) were previously identified by using the Collection 3 data of MODIS Vegetation Continuous Fields (VCF). Since then, the MODIS VCF product has been updated to Collection 5; and a Landsat VCF product of global tree cover at a fine spatial resolution of 30 meters has been developed. Here we compare these different remote-sensing products of tree cover to show that identification of alternative stable states in the boreal biome partly depends on the data source used. The updated MODIS data and the newer Landsat data consistently demonstrate three distinct modes around similar tree-cover values. Our analysis suggests that the boreal region has three modes: one sparsely vegetated state (treeless), one distinct 'savanna-like' state and one forest state, which could be alternative stable states. Our analysis illustrates that qualitative outcomes of studies may change fundamentally as new versions of remote sensing products are used. Scientific reproducibility thus requires that old versions remain publicly available.

  2. A Changing Number of Alternative States in the Boreal Biome: Reproducibility Risks of Replacing Remote Sensing Products.

    Directory of Open Access Journals (Sweden)

    Chi Xu

    Full Text Available Publicly available remote sensing products have boosted science in many ways. The openness of these data sources suggests high reproducibility. However, as we show here, results may be specific to versions of the data products that can become unavailable as new versions are posted. We focus on remotely-sensed tree cover. Recent studies have used this public resource to detect multi-modality in tree cover in the tropical and boreal biomes. Such patterns suggest alternative stable states separated by critical tipping points. This has important implications for the potential response of these ecosystems to global climate change. For the boreal region, four distinct ecosystem states (i.e., treeless, sparse and dense woodland, and boreal forest were previously identified by using the Collection 3 data of MODIS Vegetation Continuous Fields (VCF. Since then, the MODIS VCF product has been updated to Collection 5; and a Landsat VCF product of global tree cover at a fine spatial resolution of 30 meters has been developed. Here we compare these different remote-sensing products of tree cover to show that identification of alternative stable states in the boreal biome partly depends on the data source used. The updated MODIS data and the newer Landsat data consistently demonstrate three distinct modes around similar tree-cover values. Our analysis suggests that the boreal region has three modes: one sparsely vegetated state (treeless, one distinct 'savanna-like' state and one forest state, which could be alternative stable states. Our analysis illustrates that qualitative outcomes of studies may change fundamentally as new versions of remote sensing products are used. Scientific reproducibility thus requires that old versions remain publicly available.

  3. Growth decline linked to warming-induced water limitation in hemi-boreal forests.

    Science.gov (United States)

    Wu, Xiuchen; Liu, Hongyan; Guo, Dali; Anenkhonov, Oleg A; Badmaeva, Natalya K; Sandanov, Denis V

    2012-01-01

    Hemi-boreal forests, which make up the transition from temperate deciduous forests to boreal forests in southern Siberia, have experienced significant warming without any accompanying increase in precipitation during the last 80 years. This climatic change could have a profound impact on tree growth and on the stability of forest ecosystems in this region, but at present evidence for these impacts is lacking. In this study, we report a recent dramatic decline in the growth of hemi-boreal forests, based on ring width measurements from three dominant tree-species (Pinus sylvestris, Larix sibirica and Larix gmelinii), sampled from eight sites in the region. We found that regional tree growth has become increasingly limited by low soil water content in the pre- and early-growing season (from October of the previous year to July of the current year) over the past 80 years. A warming-induced reduction in soil water content has also increased the climate sensitivity of these three tree species. Beginning in the mid-1980s, a clear decline in growth is evident for both the pine forests and the larch forests, although there are increasing trends in the proxy of soil water use efficiencies. Our findings are consistent with those from other parts of the world and provide valuable insights into the regional carbon cycle and vegetation dynamics, and should be useful for devising adaptive forest management strategies.

  4. The impact of bryophytes on the carbon stocks of northern boreal forest soils

    Science.gov (United States)

    Hagemann, U.; Moroni, M. T.; Shaw, C. H.; Kurz, W. A.

    2012-04-01

    Dead organic matter (DOM), organic layer, and mineral soil carbon (C) dynamics in cool and humid northern boreal forests are expected to differ from those of drier or warmer boreal forests, because processes such as paludification and woody debris (WD) burial within the organic layer by overgrowing moss are more pronounced in regions with low average temperatures, vigorous moss layers, and long fire-return intervals. However, very few studies have provided field-measured data for these mostly remote regions. Hence, C cycling models such as the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) have rarely been validated with field data from northern boreal forest soils, resulting in large uncertainties for estimated C stocks in a large proportion of the boreal forest ecozone. We present (i) measured data on organic layer and mineral soil (0-45 cm) C stocks in 18 old-growth and disturbed high-boreal black spruce stands in Labrador, Canada; (ii) a comparison of field-measured soil C stocks with those predicted using the CBM-CFS3; and (iii) special characteristics of the DOM and soil C dynamics of northern boreal forest soils that require modifications of model parameters and structure. Measured organic layer C stocks (30.4-47.4 Mg C ha-1) were within the range reported for other boreal forests. However, mineral soil C stocks (121.5-208.1 Mg C ha-1) contributed 58-76% to total ecosystem C stocks. Mineral soil C stocks were thus considerably higher than observed in other upland boreal forests in drier or warmer regions, but similar to values reported for black spruce on poorly drained sites and peat soils. In addition, large amounts of deadwood C (4.7-18.2 Mg C ha-1) were found to be buried within the organic layer, contributing up to 31% to total organic layer C stocks. The comparison of field-measured and CBM-CFS3 modeled C stocks showed that organic layer and mineral soil DOM in Labrador black spruce stands likely decays at lower rates than assumed by CBM

  5. Diverse growth trends and climate responses across Eurasia’s boreal forest

    Science.gov (United States)

    Hellmann, Lena; Agafonov, Leonid; Charpentier Ljungqvist, Fredrik; Churakova (Sidorova, Olga; Düthorn, Elisabeth; Esper, Jan; Hülsmann, Lisa; Kirdyanov, Alexander V.; Moiseev, Pavel; Myglan, Vladimir S.; Nikolaev, Anatoly N.; Reinig, Frederick; Schweingruber, Fritz H.; Solomina, Olga; Tegel, Willy; Büntgen, Ulf

    2016-07-01

    The area covered by boreal forests accounts for ˜16% of the global and 22% of the Northern Hemisphere landmass. Changes in the productivity and functioning of this circumpolar biome not only have strong effects on species composition and diversity at regional to larger scales, but also on the Earth’s carbon cycle. Although temporal inconsistency in the response of tree growth to temperature has been reported from some locations at the higher northern latitudes, a systematic dendroecological network assessment is still missing for most of the boreal zone. Here, we analyze the geographical patterns of changes in summer temperature and precipitation across northern Eurasia >60 °N since 1951 AD, as well as the growth trends and climate responses of 445 Pinus, Larix and Picea ring width chronologies in the same area and period. In contrast to widespread summer warming, fluctuations in precipitation and tree growth are spatially more diverse and overall less distinct. Although the influence of summer temperature on ring formation is increasing with latitude and distinct moisture effects are restricted to a few southern locations, growth sensitivity to June-July temperature variability is only significant at 16.6% of all sites (p ≤ 0.01). By revealing complex climate constraints on the productivity of Eurasia’s northern forests, our results question the a priori suitability of boreal tree-ring width chronologies for reconstructing summer temperatures. This study further emphasizes regional climate differences and their role on the dynamics of boreal ecosystems, and also underlines the importance of free data access to facilitate the compilation and evaluation of massively replicated and updated dendroecological networks.

  6. Recent burning of boreal forests exceeds fire regime limits of the past 10,000 years.

    Science.gov (United States)

    Kelly, Ryan; Chipman, Melissa L; Higuera, Philip E; Stefanova, Ivanka; Brubaker, Linda B; Hu, Feng Sheng

    2013-08-06

    Wildfire activity in boreal forests is anticipated to increase dramatically, with far-reaching ecological and socioeconomic consequences. Paleorecords are indispensible for elucidating boreal fire regime dynamics under changing climate, because fire return intervals and successional cycles in these ecosystems occur over decadal to centennial timescales. We present charcoal records from 14 lakes in the Yukon Flats of interior Alaska, one of the most flammable ecoregions of the boreal forest biome, to infer causes and consequences of fire regime change over the past 10,000 y. Strong correspondence between charcoal-inferred and observational fire records shows the fidelity of sedimentary charcoal records as archives of past fire regimes. Fire frequency and area burned increased ∼6,000-3,000 y ago, probably as a result of elevated landscape flammability associated with increased Picea mariana in the regional vegetation. During the Medieval Climate Anomaly (MCA; ∼1,000-500 cal B.P.), the period most similar to recent decades, warm and dry climatic conditions resulted in peak biomass burning, but severe fires favored less-flammable deciduous vegetation, such that fire frequency remained relatively stationary. These results suggest that boreal forests can sustain high-severity fire regimes for centuries under warm and dry conditions, with vegetation feedbacks modulating climate-fire linkages. The apparent limit to MCA burning has been surpassed by the regional fire regime of recent decades, which is characterized by exceptionally high fire frequency and biomass burning. This extreme combination suggests a transition to a unique regime of unprecedented fire activity. However, vegetation dynamics similar to feedbacks that occurred during the MCA may stabilize the fire regime, despite additional warming.

  7. Improved estimates of boreal Fire Radiative Energy using high temporal resolution data and a modified active fire detection algorithm

    Science.gov (United States)

    Barrett, Kirsten

    2016-04-01

    Reliable estimates of biomass combusted during wildfires can be obtained from satellite observations of fire radiative power (FRP). Total fire radiative energy (FRE) is typically estimated by integrating instantaneous measurements of fire radiative power (FRP) at the time of orbital satellite overpass or geostationary observation. Remotely-sensed FRP products from orbital satellites are usually global in extent, requiring several thresholding and filtering operations to reduce the number of false fire detections. Some filters required for a global product may not be appropriate to fire detection in the boreal forest resulting in errors of omission and increased data processing times. We evaluate the effect of a boreal-specific active fire detection algorithm and estimates of FRP/FRE. Boreal fires are more likely to escape detection due to lower intensity smouldering combustion and sub canopy fires, therefore improvements in boreal fire detection could substantially reduce the uncertainty of emissions from biomass combustion in the region. High temporal resolution data from geostationary satellites have led to improvements in FRE estimation in tropical and temperate forests, but such a perspective is not possible for high latitude ecosystems given the equatorial orbit of geostationary observation. The increased density of overpasses in high latitudes from polar-orbiting satellites, however, may provide adequate temporal sampling for estimating FRE.

  8. Characterisation of organic carbon in mire and heath soils at the Elgea-Urkilla Wind Farm, northern Spain

    Directory of Open Access Journals (Sweden)

    Z. Azkorra

    2008-07-01

    Full Text Available This paper describes a detailed comparative study of carbon storage in mire and heath soils within the Elgea-Urkilla Wind Farm (Basque Country, northern Spain. Different methods for estimating organic C stocks in the uppermost 15 cm of the soil profile were evaluated in an attempt to determine whether there was any spatial variability. The dominant vegetation of the study area was acidophilic and Atlantic heathland, with scattered areas of mire vegetation associated with spring lines. Soils were classified as Haplic Leptic Umbrisols (Oxyaquic, Molliglosic. Two sampling plots (900 m2 and 600 m2 were established adjacent to wind turbines. Mire vegetation was present in the larger plot (PLOT-A and absent from the smaller one (PLOT-B. Fourier-transformed infra-red (FTIR spectra indicated no noteworthy structural dissimilarities in the organic matter characteristics of the soils beneath the two types of vegetation. Soil samples were taken every week at systematically chosen points lying on fixed transects. Estimates of organic C stocks based on single sampling dates were 94–141 t C ha-1 for PLOT-A and 70–105 t C ha-1 for PLOT-B, and tended to increase as the weather became drier. When the estimates were derived from samples taken on several dates but from single transects, the range of the estimate for each plot was reduced to 111–116 t ha-1 for PLOT-A and 81–89 t ha-1 for PLOT-B. The results suggest that organic C stocks vary seasonally, and highlight difficulties that may be encountered in attempting to detect long-term changes in C storage.

  9. Treefall inputs to boreal soils and implications for C dynamics

    Science.gov (United States)

    Manies, K.; Harden, J. W.

    2011-12-01

    Stand replacing fires are the dominant disturbance of black spruce-dominated boreal forests. A previous study (Manies et al. 2005) determined that fire-killed wood is the source of between 10% and 60% of the carbon (C) found in the deeper, more recalcitrant soil layers of these ecosystems, although these inputs vary spatially and temporally. In that study, we assumed that the turnover time for standing dead to be converted to woody debris was approximately nine years. Over the last decade, however, woody debris inventories within two Alaskan study sites, both of which burned in 1999, indicate a longer turnover time than previously estimated. We have used these new constraints on course woody debris inputs to update the original model and calculated the impact slower fall rates could have on C storage within the deep soil C pool. These new values increase the amount of wood-derived C by up to 20%, which in turn increases deep C storage. Understanding the source of soil C is important for modeling efforts, especially those that need to partition different sources of C to determine rates of C cycling. These results also have implications for land managers who are beginning to consider C storage as a part of their management strategies.

  10. The importance of colloids and mires for the transport of uranium isotopes through the Kalix River watershed and Baltic Sea

    Science.gov (United States)

    Porcelli, D.; Andersson, P. S.; Wasserburg, G. J.; Ingri, J.; Baskaran, M.

    1997-10-01

    The importance of colloids and organic deposits for the transport of uranium isotopes from continental source regions and through the estuarine environment was investigated in the mire-rich Kalix River drainage basin in northern Sweden and the Baltic Sea. Ultrafiltration techniques were used to separate uranium and other elements associated with colloids > 10 kD and >3 kD from "solute" uranium and provided consistent results and high recovery rates for uranium as well as for other elements from large volume samples. Uranium concentrations in 0.45 μm-filtered Kalix River water samples increased by a factor of 3 from near the headwaters in the Caledonides to the river mouth while major cation concentrations were relatively constant. 234U/238U ratios were high ( δ234U = 770-1500) throughout the basin, without showing any simple pattern, and required a supply of 234U-rich water. Throughout the Kalix River, a large fraction (30-90%) of the uranium is carried by >10 kD colloids, which is compatible with uranium complexation with humic acids. No isotopic differences were found between colloid-associated and solute uranium. Within the Baltic Sea, about half of the uranium is removed at low salinities. The proportion that is lost is equivalent to that of river-derived colloid-bound uranium, suggesting that while solute uranium behaves conservatively during estuarine mixing, colloid-bound uranium is lost due to rapid flocculation of colloidal material. The association of uranium with colloids therefore may be an important parameter in determining uranium estuarine behavior. Mire peats in the Kalix River highly concentrate uranium and are potentially a significant source of recoil 234U to the mirewaters and river waters. However, mirewater data clearly demonstrate that only small 234U/238U shifts are generated relative to inflowing groundwater. A simple box model of uranium accumulation in peat and transport through the mire that is compatible with the mire data

  11. Ecosystem Jenga!

    Science.gov (United States)

    Umphlett, Natalie; Brosius, Tierney; Laungani, Ramesh; Rousseau, Joe; Leslie-Pelecky, Diandra L.

    2009-01-01

    To give students a tangible model of an ecosystem and have them experience what could happen if a component of that ecosystem were removed; the authors developed a hands-on, inquiry-based activity that visually demonstrates the concept of a delicately balanced ecosystem through a modification of the popular game Jenga. This activity can be…

  12. Natural ecosystems

    Science.gov (United States)

    Fleishman, Erica; Belnap, Jayne; Cobb, Neil; Enquist, Carolyn A.F.; Ford, Karl; MacDonald, Glen; Pellant, Mike; Schoennagel, Tania; Schmit, Lara M.; Schwartz, Mark; van Drunick, Suzanne; Westerling, Anthony LeRoy; Keyser, Alisa; Lucas, Ryan

    2013-01-01

    Natural Ecosystems analyzes the association of observed changes in climate with changes in the geographic distributions and phenology (the timing of blossoms or migrations of birds) for Southwestern ecosystems and their species, portraying ecosystem disturbances—such as wildfires and outbreaks of forest pathogens—and carbon storage and release, in relation to climate change.

  13. Interfacing with in-Situ Data Networks during the Arctic Boreal Vulnerability Experiment (ABoVE)

    Science.gov (United States)

    McInerney, M.; Griffith, P. C.; Duffy, D.; Hoy, E.; Schnase, J. L.; Sinno, S.; Thompson, J. H.

    2014-12-01

    The Arctic Boreal Vulnerability Experiment (ABoVE) is designed to improve understanding of the causes and impacts of ecological changes in Arctic/boreal regions, and will integrate field-based studies, modeling, and data from airborne and satellite remote sensing. ABoVE will result in a fuller understanding of ecosystem vulnerability and resilience to environmental change in the Arctic and boreal regions of western North America, and provide scientific information required to develop options for societal responses to the impacts of these changes. The studies sponsored by NASA during ABoVE will be coordinated with research and in-situ monitoring activities being sponsored by a number of national and international partners. The NASA Center for Climate Simulation at the Goddard Space Flight Center has partnered with the NASA Carbon Cycle & Ecosystems Office to create a science cloud designed for this field campaign - the ABoVE Science Cloud (ASC). The ASC combines high performance computing with emerging technologies to create an environment specifically designed for large-scale modeling, analysis of remote sensing data, copious disk storage with integrated data management, and integration of core variables from in-situ networks identified by the ABoVE Science Definition Team. In this talk, we will present the scientific requirements driving the development of the ABoVE Science Cloud, discuss the necessary interfaces, both computational and human, with in-situ monitoring networks, and show examples of how the ASC is being used to meet the needs of the ABoVE campaign.

  14. Nitrogen and carbon reallocation in fungal mycelia during decomposition of boreal forest litter.

    Directory of Open Access Journals (Sweden)

    Johanna B Boberg

    Full Text Available Boreal forests are characterized by spatially heterogeneous soils with low N availability. The decomposition of coniferous litter in these systems is primarily performed by basidiomycete fungi, which often form large mycelia with a well-developed capacity to reallocate resources spatially- an advantageous trait in heterogeneous environments. In axenic microcosm systems we tested whether fungi increase their biomass production by reallocating N between Pinus sylvestris (Scots pine needles at different stages of decomposition. We estimated fungal biomass production by analysing the accumulation of the fungal cell wall compound chitin. Monospecific systems were compared with systems with interspecific interactions. We found that the fungi reallocated assimilated N and mycelial growth away from well-degraded litter towards fresh litter components. This redistribution was accompanied by reduced decomposition of older litter. Interconnection of substrates increased over-all fungal C use efficiency (i.e. the allocation of assimilated C to biomass rather than respiration, presumably by enabling fungal translocation of growth-limiting N to litter with higher C quality. Fungal connection between different substrates also restricted N-mineralization and production of dissolved organic N, suggesting that litter saprotrophs in boreal forest ecosystems primarily act to redistribute rather than release N. This spatial integration of different resource qualities was hindered by interspecific interactions, in which litters of contrasting quality were colonised by two different basidiomycete species. The experiments provide a detailed picture of how resource reallocation in two decomposer fungi leads to a more efficient utilisation of spatially separated resources under N-limitation. From an ecosystem point of view, such economic fungal behaviour could potentially contribute to organic matter accumulation in the litter layers of boreal forests.

  15. Identifying the main drivers of soil carbon response to climate change in arctic and boreal Alaska.

    Science.gov (United States)

    Genet, H.; McGuire, A. D.; He, Y.; Johnson, K.; Wylie, B. K.; Pastick, N. J.; Zhuang, Q.; Zhu, Z.

    2015-12-01

    Boreal and arctic regions represent the largest reservoir of carbon among terrestrial biomes. Most of this carbon is stored deep in the soil in permafrost where frozen organic matter is protected from decomposition. The vulnerability of soil carbon stocks to a changing climate in high latitudes depends on a number of physical and ecological processes. The importance of these processes in controlling the dynamics of soil carbon stocks vary across regions because of variability in vegetation composition, drainage condition, and permafrost characteristics. To better understand the main drivers of the vulnerability of soil carbon stocks to climate change in Alaska, we ran a process-based ecosystem model, the Terrestrial Ecosystem Model. This model explicitly simulates interactions between the carbon cycle and permafrost dynamics and was coupled with a disturbance model and a model of biogenic methane dynamics to assess historical and projected soil carbon dynamics in Alaska, from 1950 to 2100. The uncertainties related to climate, fire regime and atmospheric CO2projections on soil carbon dynamics were quantified by running simulations using climate projections from 2 global circulation models, 3 fossil fuel emission scenarios and 3 alternative fire management scenarios. During the historical period [1950-2009], soil carbon stocks increased by 4.7 TgC/yr in Alaska. Soil carbon stocks decreased in boreal Alaska due to substantial fire activity in the early 2000's. This loss was offset by carbon accumulation in the arctic. Changes in soil carbon stocks from 2010 to 2099 ranged from 8.9 to 25.6 TgC/yr, depending on the climate projections. Soil carbon accumulation was slower in lowlands than in uplands and slower in the boreal than in the arctic regions because of the negative effect of fire activity on soil carbon stocks. Tundra ecosystems were more vulnerable to carbon loss from fire than forest ecosystems because of a lower productivity. As a result, the increase in

  16. Detecting Local Drivers of Fire Cycle Heterogeneity in Boreal Forests: A Scale Issue

    Directory of Open Access Journals (Sweden)

    Annie Claude Bélisle

    2016-07-01

    Full Text Available Severe crown fires are determining disturbances for the composition and structure of boreal forests in North America. Fire cycle (FC associations with continental climate gradients are well known, but smaller scale controls remain poorly documented. Using a time since fire map (time scale of 300 years, the study aims to assess the relative contributions of local and regional controls on FC and to describe the relationship between FC heterogeneity and vegetation patterns. The study area, located in boreal eastern North America, was partitioned into watersheds according to five scales going from local (3 km2 to landscape (2800 km2 scales. Using survival analysis, we observed that dry surficial deposits and hydrography density better predict FC when measured at the local scale, while terrain complexity and slope position perform better when measured at the middle and landscape scales. The most parsimonious model was selected according to the Akaike information criterion to predict FC throughout the study area. We detected two FC zones, one short (159 years and one long (303 years, with specific age structures and tree compositions. We argue that the local heterogeneity of the fire regime contributes to ecosystem diversity and must be considered in ecosystem management.

  17. Large-scale variation in boreal and temperate forest carbon turnover rate related to climate

    Science.gov (United States)

    Thurner, Martin; Beer, Christian; Carvalhais, Nuno; Forkel, Matthias; Santoro, Maurizio; Tum, Markus; Schmullius, Christiane

    2016-05-01

    Vegetation carbon turnover processes in forest ecosystems and their dominant drivers are far from being understood at a broader scale. Many of these turnover processes act on long timescales and include a lateral dimension and thus can hardly be investigated by plot-level studies alone. Making use of remote sensing-based products of net primary production (NPP) and biomass, here we show that spatial gradients of carbon turnover rate (k) in Northern Hemisphere boreal and temperate forests are explained by different climate-related processes depending on the ecosystem. k is related to frost damage effects and the trade-off between growth and frost adaptation in boreal forests, while drought stress and climate effects on insects and pathogens can explain an elevated k in temperate forests. By identifying relevant processes underlying broadscale patterns in k, we provide the basis for a detailed exploration of these mechanisms in field studies, and ultimately the improvement of their representations in global vegetation models (GVMs).

  18. Contribution of vegetation and water table on isoprene emission from boreal peatland microcosms

    DEFF Research Database (Denmark)

    Tiiva, Päivi; Faubert, Patrick; Räty, Sanna;

    2009-01-01

    Boreal peatlands are substantial sources of isoprene, a reactive hydrocarbon. However, it is not known how much mosses, vascular plants and peat each contribute to isoprene emission from peatlands. Furthermore, there is no information on the effects of declining water table depth on isoprene emis....... In conclusion, isoprene emissions from peatlands will decrease, but the proportion of assimilated carbon lost as isoprene will increase, if the naturally high water table declines under the changing climate....... emission in these naturally wet ecosystems, although water table is predicted to decline due to climate warming. We studied the relative contribution of mosses vs. vascular plants to isoprene emission in boreal peatland microcosms in growth chambers by removing either vascular vegetation or both vascular...... hollows with intact vegetation, 45 ± 6 µg m-2 h-1, was decreased by 25% under water table drawdown. However, water table drawdown reduced net ecosystem carbon dioxide (CO2) exchange more dramatically than isoprene emission. Isoprene emission strongly correlated with both CO2 exchange and methane emission...

  19. Large carbon dioxide fluxes from headwater boreal and sub-boreal streams.

    Science.gov (United States)

    Venkiteswaran, Jason J; Schiff, Sherry L; Wallin, Marcus B

    2014-01-01

    Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that conventional methods of determining CO2 loss from streams necessarily underestimate the CO2 loss with results from two catchments. Dissolved carbon export from headwater catchments is similar to CO2 loss from stream surfaces. Most of the CO2 originating in high CO2 groundwaters has been lost before typical in-stream sampling occurs. In the Harp Lake catchment in Canada, headwater streams account for 10% of catchment net CO2 uptake. In the Krycklan catchment in Sweden, this more than doubles the CO2 loss from the catchment. Thus, even when corrected for aquatic CO2 loss measured by conventional methods, boreal and sub-boreal forest carbon budgets currently overestimate carbon sequestration on the landscape.

  20. Regulation of Boreal soil respiration: evidence from a Swedish forest fire chronosequence.

    Science.gov (United States)

    Mason, Kelly; Oakley, Simon; Ostle, Nicholas; DeLuca, Thomas; Arróniz-Crespo, María; Jones, Davey

    2014-05-01

    Globally, boreal forests occupy 14% of total land surface and are important regions for biogeochemical cycling of carbon (C) and nitrogen (N)1. They are recognised as stores of terrestrial C and reservoirs of uniquely adapted biodiversity. Like many forest biomes, boreal forests are under pressure from climate change and growing populations. C and N cycling in the boreal region is strongly influenced by the occurrence of forest fires, which return large amounts of stored N back into an otherwise N limited system2. The frequency and intensity of boreal forest fires is expected to increase in the next century as the global atmosphere warms and N deposition continues to increase due to human activities3,4. Despite the importance of these ecosystems, there is limited knowledge of the effects of interactions between climate and N limitation on soil respiration and feedbacks of carbon dioxide (CO2) and other greenhouse gases (GHGs) to the atmosphere. In this research we aimed to improve understanding of how changes in the frequency and intensity of fires might alter N and C dynamics in the boreal region. Specifically, we examined the degree of N limitation and the temperature sensitivity of GHG (CO2, N2O and CH4) fluxes from soils underlying carpets of Pleurozium schreberi, a feather moss known to form important symbiotic relationships with N-fixing cyanobacteria1, from a fire chronosequence of Swedish boreal forest stands. We hypothesised that: (1) soil respiration in late succession ecosystems is most N limited due to high soil C:N ratios and high microbial biomass; and (2) early succession forest soil respiration is most temperature sensitive due to higher N availability and higher bacterial biomass. To test these hypotheses, we took soil cores from a chronosequence of six sites in the northern boreal region of Sweden, including two early, two mid, and two late succession stands. These sites are dominated by mixed Pinus sylvestris and Picea abies, with an understory

  1. Phosphorus status of soils from contrasting forested ecosystems in Southwestern Siberia: combined effects of plant species and climate

    OpenAIRE

    2012-01-01

    The Russian boreal forest, which mainly consists of extensive forests in Siberia, is the largest continuous forest region on Earth and represents 70 % of the world's boreal forest. Siberian forest is a tremendous repository of terrestrial organic carbon (C), which may increase owing to climate change, potential increases in ecosystem productivity and hence C sequestration. Phosphorus (P) availability could limit the C sequestration potential, but tree roots may mine the soil deeper to ...

  2. Priming effects in boreal black spruce forest soils: quantitative evaluation and sensitivity analysis.

    Directory of Open Access Journals (Sweden)

    Zhaosheng Fan

    Full Text Available Laboratory studies show that introduction of fresh and easily decomposable organic carbon (OC into soil-water systems can stimulate the decomposition of soil OC (SOC via priming effects in temperate forests, shrublands, grasslands, and agro-ecosystems. However, priming effects are still not well understood in the field setting for temperate ecosystems and virtually nothing is known about priming effects (e.g., existence, frequency, and magnitude in boreal ecosystems. In this study, a coupled dissolved OC (DOC transport and microbial biomass dynamics model was developed to simultaneously simulate co-occurring hydrological, physical, and biological processes and their interactions in soil pore-water systems. The developed model was then used to examine the importance of priming effects in two black spruce forest soils, with and without underlying permafrost. Our simulations showed that priming effects were strongly controlled by the frequency and intensity of DOC input, with greater priming effects associated with greater DOC inputs. Sensitivity analyses indicated that priming effects were most sensitive to variations in the quality of SOC, followed by variations in microbial biomass dynamics (i.e., microbial death and maintenance respiration, highlighting the urgent need to better discern these key parameters in future experiments and to consider these dynamics in existing ecosystem models. Water movement carries DOC to deep soil layers that have high SOC stocks in boreal soils. Thus, greater priming effects were predicted for the site with favorable water movement than for the site with limited water flow, suggesting that priming effects might be accelerated for sites where permafrost degradation leads to the formation of dry thermokarst.

  3. Holocene history and environmental reconstruction of a Hercynian mire and surrounding mountain landscape based on multiple proxies

    Science.gov (United States)

    Dudová, Lydie; Hájková, Petra; Opravilová, Věra; Hájek, Michal

    2014-07-01

    We discovered the first peat section covering the entire Holocene in the Hrubý Jeseník Mountains, representing an island of unique alpine vegetation whose history may display transitional features between the Hercynian and Carpathian regions. We analysed pollen, plant macrofossils (more abundant in bottom layers), testate amoebae (more abundant in upper layers), peat stratigraphy and chemistry. We found that the landscape development indeed differed from other Hercynian mountains located westward. This is represented by Pinus cembra and Larix during the Pleistocene/Holocene transition, the early expansion of spruce around 10,450 cal yr BP, and survival of Larix during the climatic optimum. The early Holocene climatic fluctuations are traced in our profile by species compositions of both the mire and surrounding forests. The mire started to develop as a calcium-rich percolation fen with some species recently considered to be postglacial relicts (Meesia triquetra, Betula nana), shifted into ombrotrophy around 7450 cal yr BP by autogenic succession and changed into a pauperised, nutrient-enriched spruce woodland due to modern forestry activities. We therefore concluded that its recent vegetation is not a product of natural processes. From a methodological viewpoint we demonstrated how using multiple biotic proxies and extensive training sets in transfer functions may overcome taphonomic problems.

  4. Ecology of some mire and bog plant communities in the Western Italian Alps

    Directory of Open Access Journals (Sweden)

    Giorgio BUFFA

    2003-02-01

    Full Text Available During a mire vegetation study, conducted mainly in the subalpine-alpine sector of the Western Italian Alps, the ecology of several plant communities and numerous moss species of this kind of vegetation was evaluated. The study area covered the Piedmontese sector of the Graian Alps, the eastern sector of the Aosta Valley as well as certain localities of the Pennine Alps, the Canavese district and the Maritime Alps. They have a rocky substratum representative of the various regional lithologies and include the main sectors characterised by the highest precipitation. Three hundred and twenty two relevées were made using the phytosociological method and the pH and the conductivity of the water table and its depth were measured directly. Cluster Analysis allowed a classification of the samples and the identification of various groups of plant communities. Ordination performed by DCA and CCA allowed us to identify the ecological features of the various plant communities by using the values of the main environmental parameters, measured directly in the field, and certain climatic parameters (altitude and mean annual precipitation available. The use of climatic parameters is an important result for identifying communities which show greater oceanicity, something that is underlined also by the presence of indicator species such as Sphagnum papillosum and S. subnitens. Furthermore the communities are arranged in a "poor-rich" gradient, and are also profoundly influenced by depth to water table which is inversely correlated to the pH. Therefore we find certain kinds of communities all with a very low water table and which are little affected by its chemistry. Other groups share the fact that the water table is outcropping or near the surface and are distinguishable for their pH values and conductivity. We discuss the different response of the bryophytes and vascular plants of these communities to the environmental parameters considered, in light of their

  5. Understanding COS Fluxes in a Boreal Forest: Towards COS-Based GPP Estimates.

    Science.gov (United States)

    Chen, H.; Kooijmans, L.; Franchin, A.; Keskinen, H.; Levula, J.; Mammarella, I.; Maseyk, K. S.; Pihlatie, M.; Praplan, A. P.; Seibt, U.; Sun, W.; Vesala, T.

    2015-12-01

    Carbonyl Sulfide (COS) is a promising new tracer that can be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. COS and CO2 vegetation fluxes are closely related as these gases share the same diffusion pathway into stomata, which makes COS a potentially powerful tracer for GPP. While vegetative uptake is the largest sink of COS, the environmental drivers are poorly understood, and soil fluxes represent an important but relatively unconstrained component. Therefore, the realization of the COS tracer method requires proper characterization of both soil and ecosystem fluxes. A campaign to provide better constrained soil and ecosystem COS flux data for boreal forests took place in the summer of 2015 at the SMEAR II site in Hyytiälä, Finland. Eddy covariance flux measurements were made above the forest canopy on an Aerodyne continuous-wave quantum cascade laser (QCL) system that is capable of measuring COS, CO2, CO and H2O. Soil COS fluxes were obtained using modified LI-COR LI-8100 chambers together with high accuracy concentration measurements from another Aerodyne QCL instrument. The same instrument alternately measured concentrations in and above the canopy on a cycle through 4 heights, which will be used to calculate ecosystem fluxes using the Radon-tracer method, providing ecosystem fluxes under low-turbulent conditions. We will compare ecosystem fluxes from both eddy covariance and profile measurements and show estimates of the fraction of ecosystem fluxes attributed to the soil component. With the better understanding of ecosystem and soil COS fluxes, as obtained with this dataset, we will be able to derive COS-based GPP estimates for the Hyytiälä site.

  6. Responses of aboveground and belowground forest carbon stocks to disturbances in boreal forests of Northeastern China

    Science.gov (United States)

    Huang, Chao; He, Hong S.; Hawbaker, Todd J.; Liang, Yu; Gong, Peng; Wu, Wuzhiwei; Zhu, Zhiliang

    2016-04-01

    Boreal forests represents about 1/3 of forest area and 1/3 of forest carbon on earth. Carbon dynamics of boreal forests are sensitive to climate change, natural (e.g., fire) and anthropogenic (e.g., harvest) disturbances. Field-based studies suggest that disturbances alter species composition, stand structure, and litter decomposition, and have significant effects on boreal forest carbon dynamics. Most of these studies, however, covered a relatively short period of time (e.g., few decades), which is limited in revealing such long-term effects of disturbances. Models are therefore developed as important tools in exploring the long-term (e.g., hundreds of years) effects of disturbances on forest carbon dynamics. In this study, we applied a framework of coupling forest ecosystem and landscape model to evaluating the effect of fire, harvest and their interactions on carbon stocks in a boreal forest landscape of Northeastern China. We compared the simulation results under fire, harvest and fire-harvest interaction scenarios with the simulated value of succession scenario at 26 landtypes over 150 years at a 10-year time step. Our results suggest that aboveground and belowground carbon are significantly reduced by fire and harvest over 150years. Fire reduced aboveground carbon by 2.3±0.6 ton/ha, harvest by 6.0±1.4 ton/ha, and fire and harvest interaction by 8.0±1.9 tons/ha. Fire reduced belowground carbon by 4.6±3.4 ton/ha, harvest by 5.0±3.5 ton/ha, and fire-harvest interaction by 5.7±3.7 tons/ha. The divergent response of carbon stocks among landtypes and between disturbance scenarios was due to the spatial interactions between fire, harvest, and species composition. Our results indicated that boreal forests carbon stocks prediction needs to consider the effects of fire and harvest for improving the estimation accuracy.

  7. Quantifying CO2 Fluxes Across a Gradient of Permafrost in Boreal Alaska

    Science.gov (United States)

    Euskirchen, E. S.; Edgar, C.; Turetsky, M. R.; Harden, J. W.; McGuire, A. D.

    2011-12-01

    Changes in vegetation and soil properties following permafrost degradation and thermokarst development may cause changes in net carbon uptake, either by stimulating primary productivity due to changes in vegetation composition or by stimulating soil microbial decomposition. In order to better understand these dynamics, we established three sites in interior Alaska across a gradient of permafrost in which permafrost varies in presence and stability. These sites include a black spruce ecosystem with cold soils and stable permafrost, a permafrost collapse scar with thermokarst formation, and a moderately rich fen lacking near surface permafrost. Measurements at the sites include year-round eddy covariance estimates of CO2, water, and energy fluxes as well as the associated micrometeorological variables. During winter, the ecosystems each released approximately 15 - 25 g C m-2 mo-1. However, the black spruce ecosystem began to take up CO2 as soon as air temperatures increased in the spring, with an estimated accumulation of ~23 g C m-2 from late March to early May. During this same period, we observed unusually high rates of ecosystem respiration some days at the thermokarst site, potentially due to the release of trapped CO2 from frozen soil gas pockets. While the black spruce ecosystem continued to act as a net sink of CO2 in the summer, taking up ~2.5± 1 g C m-2 d-1, the thermokarst and fen ecosystems remained CO2 sources, respectively releasing ~2.4 ± 0.8 g C m-2 d-1 and ~1.9 ± 1.1 g C m-2 d-1. While ecosystem respiration was similar across all three ecosystems during the summer (~4.8 ± 1.0 g C m-2 d-1), gross primary productivity was much higher in the spruce ecosystem (~7.3 ± 1.4 g C m-2 d-1) compared to the thermokarst (~ 2.5 ± 0.9 g C m-2 d-1) and fen ecosystems (~ 3.0 ± 1.1 g C m-2 d-1). These results suggest that in these boreal peatland ecosystems, permafrost thaw and thermokarst development will increase CO2 emissions to the atmosphere due to

  8. Remote Sensing Techniques in Monitoring Post-Fire Effects and Patterns of Forest Recovery in Boreal Forest Regions: A Review

    Directory of Open Access Journals (Sweden)

    Thuan Chu

    2013-12-01

    Full Text Available The frequency and severity of forest fires, coupled with changes in spatial and temporal precipitation and temperature patterns, are likely to severely affect the characteristics of forest and permafrost patterns in boreal eco-regions. Forest fires, however, are also an ecological factor in how forest ecosystems form and function, as they affect the rate and characteristics of tree recruitment. A better understanding of fire regimes and forest recovery patterns in different environmental and climatic conditions will improve the management of sustainable forests by facilitating the process of forest resilience. Remote sensing has been identified as an effective tool for preventing and monitoring forest fires, as well as being a potential tool for understanding how forest ecosystems respond to them. However, a number of challenges remain before remote sensing practitioners will be able to better understand the effects of forest fires and how vegetation responds afterward. This article attempts to provide a comprehensive review of current research with respect to remotely sensed data and methods used to model post-fire effects and forest recovery patterns in boreal forest regions. The review reveals that remote sensing-based monitoring of post-fire effects and forest recovery patterns in boreal forest regions is not only limited by the gaps in both field data and remotely sensed data, but also the complexity of far-northern fire regimes, climatic conditions and environmental conditions. We expect that the integration of different remotely sensed data coupled with field campaigns can provide an important data source to support the monitoring of post-fire effects and forest recovery patterns. Additionally, the variation and stratification of pre- and post-fire vegetation and environmental conditions should be considered to achieve a reasonable, operational model for monitoring post-fire effects and forest patterns in boreal regions.

  9. Long-term fertilization of a boreal Norway spruce forest increases the temperature sensitivity of soil organic carbon mineralization.

    Science.gov (United States)

    Coucheney, Elsa; Strömgren, Monika; Lerch, Thomas Z; Herrmann, Anke M

    2013-12-01

    Boreal ecosystems store one-third of global soil organic carbon (SOC) and are particularly sensitive to climate warming and higher nutrient inputs. Thus, a better description of how forest managements such as nutrient fertilization impact soil carbon (C) and its temperature sensitivity is needed to better predict feedbacks between C cycling and climate. The temperature sensitivity of in situ soil C respiration was investigated in a boreal forest, which has received long-term nutrient fertilization (22 years), and compared with the temperature sensitivity of C mineralization measured in the laboratory. We found that the fertilization treatment increased both the response of soil in situ CO2 effluxes to a warming treatment and the temperature sensitivity of C mineralization measured in the laboratory (Q10). These results suggested that soil C may be more sensitive to an increase in temperature in long-term fertilized in comparison with nutrient poor boreal ecosystems. Furthermore, the fertilization treatment modified the SOC content and the microbial community composition, but we found no direct relationship between either SOC or microbial changes and the temperature sensitivity of C mineralization. However, the relation between the soil C:N ratio and the fungal/bacterial ratio was changed in the combined warmed and fertilized treatment compared with the other treatments, which suggest that strong interaction mechanisms may occur between nutrient input and warming in boreal soils. Further research is needed to unravel into more details in how far soil organic matter and microbial community composition changes are responsible for the change in the temperature sensitivity of soil C under increasing mineral N inputs. Such research would help to take into account the effect of fertilization managements on soil C storage in C cycling numerical models.

  10. Impact of Forest Harvesting on Trophic Structure of Eastern Canadian Boreal Shield Lakes: Insights from Stable Isotope Analyses

    Science.gov (United States)

    Glaz, Patricia; Sirois, Pascal; Archambault, Philippe; Nozais, Christian

    2014-01-01

    Perturbations on ecosystems can have profound immediate effects and can, accordingly, greatly alter the natural community. Land-use such as forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. The objective of this study was to evaluate the impact of forest harvesting on trophic structure in eastern Canadian Boreal Shield lakes. We measured carbon and nitrogen stable isotopes values for aquatic primary producers, terrestrial detritus, benthic macroinvertebrates, zooplankton and brook trout (Salvelinus fontinalis) over a three-year period in eight eastern Boreal Shield lakes. Four lakes were studied before, one and two years after forest harvesting (perturbed lakes) and compared with four undisturbed reference lakes (unperturbed lakes) sampled at the same time. Stable isotope mixing models showed leaf-litter to be the main food source for benthic primary consumers in both perturbed and unperturbed lakes, suggesting no logging impact on allochthonous subsidies to the littoral food web. Brook trout derived their food mainly from benthic predatory macroinvertebrates in unperturbed lakes. However, in perturbed lakes one year after harvesting, zooplankton appeared to be the main contributor to brook trout diet. This change in brook trout diet was mitigated two years after harvesting. Size-related diet shift were also observed for brook trout, indicating a diet shift related to size. Our study suggests that carbon from terrestrial habitat may be a significant contribution to the food web of oligotrophic Canadian Boreal Shield lakes. Forest harvesting did not have an impact on the diet of benthic primary consumers. On the other hand, brook trout diet composition was affected by logging with greater zooplankton contribution in perturbed lakes, possibly induced by darker-colored environment in these lakes one year after logging. PMID:24763366

  11. The Arctic Boreal Vulnerability Experiment: Observing, Understanding, and Predicting Social-Ecological Change in the Far North

    Science.gov (United States)

    Mack, M. C.; Goetz, S. J.; Kasischke, E. S.; Kimball, J. S.; Boelman, N.

    2015-12-01

    In the high northern latitudes, climate is warming more rapidly than anywhere else on Earth, transforming vulnerable arctic tundra and boreal forest landscapes. These changes are altering the structure and function of energy, water and carbon cycles, producing significant feedbacks to regional and global climate through changes in energy, water and carbon cycles. These changes are also challenging local and global society. At the local level, communities seek to adapt to new social-ecological regimes. At the global level, changing arctic and boreal systems are increasing becoming the focus of policy discussions at all levels of decision-making. National and international scientific efforts associated with a new NASA field campaign, the Arctic-Boreal Vulnerability Experiment (ABOVE) will advance our ability to observe, understand and predict the complex, multiscale and non-linear processes that are confronting the natural and social systems in this rapidly changing region. Over the next decade, the newly assembled ABOVE Science Team will pursue this overarching question: "How vulnerable or resilient are ecosystems and society to environmental change in the Arctic and boreal region of western North America?" Through integration of remote sensing and in situ observations with modeling of both ecological and social systems, the ABOVE Science Team will advance an interdisciplinary understanding of the Far North. In this presentation, we will discuss the conceptual basis for the ABOVE Field Campaign, describe Science Team composition and timeline, and update the community on activities. In addition, we will reflect on the visionary role of Dr. Diane Wickland, retired NASA Terrestrial Ecology Program Manager and lead of the Carbon Cycle & Ecosystems Focus Area, in the development and commencement of ABOVE.

  12. Boreal Forests of Kamchatka: Structure and Composition

    Directory of Open Access Journals (Sweden)

    Markus P. Eichhorn

    2010-09-01

    Full Text Available Central Kamchatka abounds in virgin old-growth boreal forest, formed primarily by Larix cajanderi and Betula platyphylla in varying proportions. A series of eight 0.25–0.30 ha plots captured the range of forests present in this region and their structure is described. Overall trends in both uplands and lowlands are for higher sites to be dominated by L. cajanderi with an increasing component of B. platyphylla with decreasing altitude. The tree line on wet sites is commonly formed by mono-dominant B. ermanii forests. Basal area ranged from 7.8–38.1 m2/ha and average tree height from 8.3–24.7 m, both being greater in lowland forests. Size distributions varied considerably among plots, though they were consistently more even for L. cajanderi than B. platyphylla. Upland sites also contained a dense subcanopy of Pinus pumila averaging 38% of ground area. Soil characteristics differed among plots, with upland soils being of lower pH and containing more carbon. Comparisons are drawn with boreal forests elsewhere and the main current threats assessed. These forests provide a potential baseline to contrast with more disturbed regions elsewhere in the world and therefore may be used as a target for restoration efforts or to assess the effects of climate change independent of human impacts.

  13. Ascertaining the nature and timing of mire degradation: using palaeoecology to assist future conservation management in Northern England

    Directory of Open Access Journals (Sweden)

    Frank Chambers

    2017-02-01

    Full Text Available Large areas of upland mire and moorland in Northwest Europe are regarded as degraded, not actively peat-forming, and releasing carbon. Conservation agencies have short-term targets to restore such areas, but often have no clear knowledge of the timing and nature of degradation. It has been suggested that palaeoecology can be used to inform conservation management about past vegetation states, so as to help identify feasible restoration targets. Our research study in northern England, commissioned by the national statutory conservation agency, applied multiple palaeoecological techniques to establish the vegetation history of several mire and moorland sites, specifically to ascertain the nature and timing of degradation. Techniques applied included pollen analysis, plant macrofossil and charcoal analyses, determination of peat humification and mineral magnetic susceptibility, with ages ascertained using spheroidal carbonaceous particle analysis, 210Pb and 14C dating. Data are presented from case-study sites in the North York Moors, North- and South Pennines to illustrate how palaeoecology can extend long-term monitoring and guide conservation management. Palaeoecological data from a site within a National Nature Reserve, subject to exceptionally long-term (half-centennial ecological monitoring, showed that this period does not include its pre-degradation state and that its current valued vegetation is novel and may have established after major fire. Overall, the studies suggest that the principal vegetation change at the sites took place after the start of the Industrial Revolution, and that the current landscape appearance not only has no long history, but that valued aspects, such as extensive heather moorland, feature only recently in the cultural landscape. These findings pose challenging questions for conservation management. We offer a non-specialist guide to the palaeoecological techniques that considers level of skill, cost, and

  14. Timing of plant phenophases since 1752 in the boreal forest environment

    Science.gov (United States)

    Kubin, Eero; Tolvanen, Anne; Karhu, Jouni; Valkama, Jari

    2016-04-01

    almost constant in the southern boreal zone. Effective temperature sum is important for the timing of the bud burst. The timing of phenological phenomena of forest vegetation, berry and seed crops reflects information about the response of the forest environment to the changes in the environmental factors. The global warming will be at its most powerful in the northern latitudes and this phenomenon is predicted to become increasingly more powerful in the future. Study of the regional differences will yield information about the changes in the northern limits of distribution of different plant species, and these changes can significantly affect the quantitative proportions of plant species. These changes, in turn, have an indirect impact on the entire ecosystem and the sources of livelihood relying on it. Phenological monitoring is nowadays more important than ever especially in boreal regions, where spring temperatures are elevated. Compilation and documentation of observations on plant phenophases play a key role in working out the rate of global climate change. To utilize citizen-science data together with the scientific monitoring will be discussed in the conference.

  15. Attaining Whole-Ecosystem Warming Using Air and Deep Soil Heating Methods with an Elevated CO2 Atmosphere

    OpenAIRE

    Hanson, Paul J.; Riggs, Jeffery S.; Nettles, W. Robert; Phillips, Jana R.; Krassovski, Misha B.; Hook, Leslie A.; Gu, Lianhong; Richardson, Andrew D.; Aubrecht, Donald M.; Ricciuto, Daniel M.; Warren, Jeffrey M.; Barbier, Charlotte

    2016-01-01

    This paper describes the operational methods to achieve and measure both deep soil heating (0–3 m) and whole-ecosystem warming (WEW) appropriate to the scale of tall-stature, high-carbon, boreal forest peatlands. The methods were developed to allow scientists to provide a plausible set of ecosystem warming scenarios within which immediate and longer term (one decade) responses of organisms (microbes to trees) and ecosystem functions (carbon, water and nutrient cycles) could be me...

  16. Management effects on carbon fluxes in boreal forests (Invited)

    Science.gov (United States)

    Lindroth, A.; Mölder, M.; Lagergren, F.; Vestin, P.; Hellström, M.; Sundqvist, E.; Norunda Bgs Team

    2010-12-01

    Disturbance by management or natural causes such as wind throw or fire are believed to be one of the main factors that are controlling the carbon balance of vegetation. In Northern Europe a large fraction of the forest area is managed with clear cutting and thinning as the main silvicultural methods. The effect of clear-cutting on carbon dioxide exchanges were studied in different chrono-sequences located in Sweden, Finland, UK and France, respectively. The combined results from these studies showed that a simple model could be developed describing relative net ecosystem exchange as a function of relative rotation length (age). A stand with a rotation length of 100 years, typical for Swedish conditions, looses substantial amounts of carbon during the first 12-15 years and the time it takes to reach cumulative balance after clear-cut, is 25-30 years. The mean net ecosystem exchange over the whole rotation length equals 50% of the maximum uptake. An interesting question is if it is possible to harvest without the substantial carbon losses that take place after clear-cutting. Selective harvest by thinning could potentially be such a method. We therefore studied the effect of thinning on soil and ecosystem carbon fluxes in a mixed pine and spruce forest in Central Sweden, the Norunda forest, located in the semi-boreal zone at 60.08°N, 17.48 °E. The CO2 fluxes from the forest were measured by eddy covariance method and soil effluxes were measured by automatic chambers. Maximum canopy height of the ca. 100 years-old forest was 28 m. The stand was composed of ca 72% pine, 28% before the thinning while the composition after the thinning became 82% pine and 18% spruce. The thinning was made in November/December 2008 in a half- circle from the tower with a radius of 200 m. The LAI decreased from 4.5 to 2.8 after the thinning operation. Immediately after the thinning, we found significantly higher soil effluxes, probably due to increased decomposition of dead roots. The

  17. Modeling the production, decomposition, and transport of dissolved organic carbon in boreal soils

    Science.gov (United States)

    Fan, Zhaosheng; Neff, Jason C.; Wickland, Kimberly P.

    2010-01-01

    The movement of dissolved organic carbon (DOC) through boreal ecosystems has drawn increased attention because of its potential impact on the feedback of OC stocks to global environmental change in this region. Few models of boreal DOC exist. Here we present a one-dimensional model with simultaneous production, decomposition, sorption/desorption, and transport of DOC to describe the behavior of DOC in the OC layers above the mineral soils. The field-observed concentration profiles of DOC in two moderately well-drained black spruce forest sites (one with permafrost and one without permafrost), coupled with hourly measured soil temperature and moisture, were used to inversely estimate the unknown parameters associated with the sorption/desorption kinetics using a global optimization strategy. The model, along with the estimated parameters, reasonably reproduces the concentration profiles of DOC and highlights some important potential controls over DOC production and cycling in boreal settings. The values of estimated parameters suggest that humic OC has a larger potential production capacity for DOC than fine OC, and most of the DOC produced from fine OC was associated with instantaneous sorption/desorption whereas most of the DOC produced from humic OC was associated with time-dependent sorption/desorption. The simulated DOC efflux at the bottom of soil OC layers was highly dependent on the component and structure of the OC layers. The DOC efflux was controlled by advection at the site with no humic OC and moist conditions and controlled by diffusion at the site with the presence of humic OC and dry conditions.

  18. Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests.

    Science.gov (United States)

    Kreyling, Juergen; Haei, Mahsa; Laudon, Hjalmar

    2012-02-01

    Snow regimes affect biogeochemistry of boreal ecosystems and are altered by climate change. The effects on plant communities, however, are largely unexplored despite their influence on relevant processes. Here, the impact of snow cover on understory community composition and below-ground production in a boreal Picea abies forest was investigated using a long-term (8-year) snow cover manipulation experiment consisting of the treatments: snow removal, increased insulation (styrofoam pellets), and control. The snow removal treatment caused longer (118 vs. 57 days) and deeper soil frost (mean minimum temperature -5.5 vs. -2.2°C) at 10 cm soil depth in comparison to control. Understory species composition was strongly altered by the snow cover manipulations; vegetation cover declined by more than 50% in the snow removal treatment. In particular, the dominant dwarf shrub Vaccinium myrtillus (-82%) and the most abundant mosses Pleurozium schreberi (-74%) and Dicranum scoparium (-60%) declined strongly. The C:N ratio in V. myrtillus leaves and plant available N in the soil indicated no altered nitrogen nutrition. Fine-root biomass in summer, however, was negatively affected by the reduced snow cover (-50%). Observed effects are attributed to direct frost damage of roots and/ or shoots. Besides the obvious relevance of winter processes on plant ecology and distribution, we propose that shifts in the vegetation caused by frost damage may be an important driver of the reported alterations in biogeochemistry in response to altered snow cover. Understory plant performance clearly needs to be considered in the biogeochemistry of boreal systems in the face of climate change.

  19. Patterns of NPP, GPP, Respiration and NEP During Boreal Forest Succession

    Energy Technology Data Exchange (ETDEWEB)

    Goulden, Michael L.; McMillan, Andrew; Winston, Greg; Rocha, Adrian; Manies, Kristen; Harden, Jennifer W.; Bond-Lamberty, Benjamin

    2010-12-15

    We deployed a mesonet of year-round eddy covariance towers in boreal forest stands that last burned in ~1850, ~1930, 1964, 1981, 1989, 1998, and 2003 to understand how CO2 exchange changes during secondary succession.The strategy of using multiple methods, including biometry and micrometeorology, worked well. In particular, the three independent measures of NEP during succession gave similar results. A stratified and tiered approach to deploying eddy covariance systems that combines many lightweight and portable towers with a few permanent ones is likely to maximize the science return for a fixed investment. The existing conceptual models did a good job of capturing the dominant patterns of NPP, GPP, Respiration and NEP during succession. The initial loss of carbon following disturbance was neither as protracted nor large as predicted. This muted response reflects both the rapid regrowth of vegetation following fire and the prevalence of standing coarse woody debris following the fire, which is thought to decay slowly. In general, the patterns of forest recovery from disturbance should be expected to vary as a function of climate, ecosystem type and disturbance type. The NPP decline at the older stands appears related to increased Rauto rather than decreased GPP. The increase in Rauto in the older stands does not appear to be caused by accelerated maintenance respiration with increased biomass, and more likely involves increased allocation to fine root turnover, root metabolism, alternative forms of respiration, mycorrhizal relationships, or root exudates, possibly associated with progressive nutrient limitation. Several studies have now described a similar pattern of NEP following boreal fire, with 10-to-15 years of modest carbon loss followed by 50-to-100 years of modest carbon gain. This trend has been sufficiently replicated and evaluated using independent techniques that it can be used to quantify the likely effects of changes in boreal fire frequency and

  20. Quantifying the missing link between forest albedo and productivity in the boreal zone

    Science.gov (United States)

    Hovi, Aarne; Liang, Jingjing; Korhonen, Lauri; Kobayashi, Hideki; Rautiainen, Miina

    2016-11-01

    Albedo and fraction of absorbed photosynthetically active radiation (FAPAR) determine the shortwave radiation balance and productivity of forests. Currently, the physical link between forest albedo and productivity is poorly understood, yet it is crucial for designing optimal forest management strategies for mitigating climate change. We investigated the relationships between boreal forest structure, albedo and FAPAR using a radiative transfer model called Forest Reflectance and Transmittance model FRT and extensive forest inventory data sets ranging from southern boreal forests to the northern tree line in Finland and Alaska (N = 1086 plots). The forests in the study areas vary widely in structure, species composition, and human interference, from intensively managed in Finland to natural growth in Alaska. We show that FAPAR of tree canopies (FAPARCAN) and albedo are tightly linked in boreal coniferous forests, but the relationship is weaker if the forest has broadleaved admixture, or if canopies have low leaf area and the composition of forest floor varies. Furthermore, the functional shape of the relationship between albedo and FAPARCAN depends on the angular distribution of incoming solar irradiance. We also show that forest floor can contribute to over 50 % of albedo or total ecosystem FAPAR. Based on our simulations, forest albedos can vary notably across the biome. Because of larger proportions of broadleaved trees, the studied plots in Alaska had higher albedo (0.141-0.184) than those in Finland (0.136-0.171) even though the albedo of pure coniferous forests was lower in Alaska. Our results reveal that variation in solar angle will need to be accounted for when evaluating climate effects of forest management in different latitudes. Furthermore, increasing the proportion of broadleaved trees in coniferous forests is the most important means of maximizing albedo without compromising productivity: based on our findings the potential of controlling forest

  1. Paleodata-model integration reveals uncertain boreal forest carbon balance due to rapid recent fire regime change

    Science.gov (United States)

    Kelly, R.; Genet, H.; McGuire, D.; Hu, F.

    2013-12-01

    Climate warming is expected to increase the frequency and severity of natural fires in the boreal forest biome. Boreal forests represent >30% of terrestrial carbon (C) stocks, and fire is a key component of the C cycle in these ecosystems. However, predictions of fire-regime change face substantial uncertainty, largely because complex fire-climate-vegetation interactions are poorly characterized in brief observational records. Furthermore, previous studies suggest that model projections of future C dynamics are sensitive to assumptions about the prehistoric fire regime. Paleofire reconstructions offer valuable insights to address these limitations. We collected 14 lake-sediment cores from the Yukon Flats, Alaska to elucidate patterns of long-term environmental change. We then converted fire-regime reconstructions from these data to input drivers for the Dynamic Organic Soils version of the Terrestrial Ecosystem Model (DOS-TEM). Combined with simulated paleoclimate from an Earth System Model and CO2 data from ice core analysis, these 'paleo-forcing' data allowed us to model past changes in ecosystem C storage in our study area to (1) assess the relative importance of climate, atmospheric CO2 concentration, and fire in driving C dynamics of the past millennium, and (2) evaluate the effect of assumptions about prehistoric fire regime on predictions of current and future boreal-forest C balance. Fire-regime variations were the dominant control on simulated C storage, producing fluctuations of ~3 kg C/m2 (~25% of total ecosystem C) on centennial timescales. By comparison, climate and CO2 concentration played minor roles. Fire frequency shifts were particularly influential, suggesting that the role of fire in dictating stand age distribution at the landscape scale is of paramount importance to net C dynamics. That shifts in fire-regime were responsible for large and rapid losses of C in the past emphasizes the importance of incorporating fire into methodologies that

  2. Effects of warming on the structure and function of a boreal black spruce forest

    Energy Technology Data Exchange (ETDEWEB)

    Stith T.Gower

    2010-03-03

    A strong argument can be made that there is a greater need to study the effect of warming on boreal forests more than on any other terrestrial biome. Boreal forests, the second largest forest biome, are predicted to experience the greatest warming of any forest biome in the world, but a process-based understanding of how warming will affect the structure and function of this economically and ecologically important forest biome is lacking. The effects of warming on species composition, canopy structure and biogeochemical cycles are likely to be complex; elucidating the underlying mechanisms will require long-term whole-ecosystem manipulation to capture all the complex feedbacks (Shaver et al. 2000, Rustad et al. 2001, Stromgren 2001). The DOE Program for Ecosystem Research funded a three year project (2002-2005) to use replicated heated chambers on soil warming plots in northern Manitoba to examine the direct effects of whole-ecosystem warming. We are nearing completion of our first growing season of measurements (fall 2004). In spite of the unforeseen difficulty of installing the heating cable, our heating and irrigation systems worked extremely well, maintaining environmental conditions within 5-10% of the specified design 99% of the time. Preliminary data from these systems, all designed and built by our laboratory at the University of Wisconsin, support our overall hypothesis that warming will increase the carbon sink strength of upland boreal black spruce forests. I request an additional three years of funding to continue addressing the original objectives: (1) Examine the effect of warming on phenology of overstory, understory and bryophyte strata. Sap flux systems and dendrometer bands, monitored by data loggers, will be used to quantify changes in phenology and water use. (2) Quantify the effects of warming on nitrogen and water use by overstory, understory and bryophytes. (3) Compare effects of warming on autotrophic respiration and above- and belowground

  3. Improvement of boreal vegetation modelling and climate interactions through the introduction of new bryophyte and artic-shrub plant functional types in a land surface model.

    Science.gov (United States)

    Druel, Arsène; Krinner, Gerhard; Peylin, Philippe; Ciais, Philippe; Viovy, Nicolas; Peregon, Anna

    2016-04-01

    Boreal and tundra vegetation, which represents 22% of the global land area, has had a significant impact on climate through changes of albedo, snow cover, soil thermal dynamics, etc. However, it is frequently poorly represented in earth system models used for climate predictions. We improved the description of high-latitude vegetation and its interactions with the environment in the ORCHIDEE land surface model by creating new plant functional types with specific biogeochemical and biophysical properties: boreal shrubs, bryophytes (mosses and lichens) and boreal C3 grasses. The introduction of shrub specificities allows for an intermediate stratum between trees and grasses, with a new carbon allometry within the plant, inducing new interactions between wooden species and their environment, especially the complex snow-shrubs interaction. Similarly, the introduction of non-vascular plants (i.e. bryophytes) involves numerous changes both in physical and biological processes, such as the response of photosynthesis to surface humidity, the decomposition of carbon and the soil thermal conductivity. These changes in turn lead to new processes and interactions between vegetation and moisture (soil and air), carbon cycle, energy balance, etc. For the boreal C3 grasses we did not include new processes compared to the generic C3 grass PFT, but improved the realism of the carbon and water budgets with new boreal adjusted parameters. We assess the performance of the modified ORCHIDEE land surface model and in particular its ability to represent the new plant types (their phenology etc.), and evaluate the effects of these new PFTs on the simulated energy, water and carbon balances of boreal ecosystems. The potential impact of these refinements on future climate simulations will be discussed.

  4. The Jurassic of Denmark and Greenland: Early and Middle Jurassic mires of Bornholm and the Fennoscandian Border Zone: a comparison of depositional environments and vegetation

    Directory of Open Access Journals (Sweden)

    Koppelhus, Eva B.

    2003-10-01

    Full Text Available Suitable climatic conditions for peat formation existed during Early–Middle Jurassic times in the Fennoscandian Border Zone. Autochthonous peat and allochthonous organic matter were depositedfrom north Jylland, south-east through the Kattegat and Øresund area, to Skåne and Bornholm. The increase in coal seam abundance and thickness from north Jylland to Bornholm indicates that the most favourable peat-forming conditions were present towards the south-east. Peat formation and deposition of organic-rich muds in the Early Jurassic coastal mires were mainly controlled by a continuous rise of relative sea level governed by subsidence and an overall eustatic rise. Watertable rise repeatedly outpaced the rate of accumulation of organic matter and terminated peat formationby lacustrine or lagoonal flooding. Organic matter accumulated in open-water mires and in continuously waterlogged, anoxic and periodically marine-influenced mires. The latter conditionsresulted in huminite-rich coals containing framboidal pyrite. The investigated Lower Jurassic seams correspond to peat and peaty mud deposits that ranged from 0.5–5.7 m in thickness, but were generallyless than 3 m thick. It is estimated that on Bornholm, the mires existed on average for c. 1200 years in the Hettangian–Sinemurian and for c. 2300 years in the Late Pliensbachian; the Early Jurassic(Hettangian–Sinemurian mires in the Øresund area existed for c. 1850 years. Aalenian uplift of the Ringkøbing–Fyn High and major parts of the Danish Basin caused a significant change in the basinconfiguration and much reduced subsidence in the Fennoscandian Border Zone during the Middle Jurassic. This resulted in a more inland position for the Middle Jurassic mires which on occasionenabled peat accumulation to keep pace with, or temporarily outpace, watertable rise. Thus, peat formation was sometimes sustained for relatively long periods, and the mires may have existed for up to 7000 years in the

  5. Modelling the fate of hydrophobic organic contaminants in a boreal forest catchment: a cross disciplinary approach to assessing diffuse pollution to surface waters.

    Science.gov (United States)

    Bergknut, Magnus; Meijer, Sandra; Halsall, Crispin; Agren, Anneli; Laudon, Hjalmar; Köhler, Stephan; Jones, Kevin C; Tysklind, Mats; Wiberg, Karin

    2010-09-01

    The fate of hydrophobic organic compounds (HOCs) in soils and waters in a northern boreal catchment was explored through the development of a chemical fate model in a well-characterised catchment system dominated by two land types: forest and mire. Input was based solely on atmospheric deposition, dominated by accumulation in the winter snowpack. Release from soils was governed by the HOC concentration in soil, the soil organic carbon fraction and soil-water DOC content. The modelled export of selected HOCs in surface waters ranged between 11 and 250 ng day(-1) during the snow covered period, compared to 200 and 9600 ng/d during snow-melt; highlighting the importance of the snow pack as a source of these chemicals. The predicted levels of HOCs in surface water were in reasonable agreement to a limited set of measured values, although the model tended to over predict concentrations of HOCs for the forested sub-catchment, by over an order of magnitude in the case of hexachlorobenzene and PCB 180. This possibly reflects both the heterogeneity of the forest soils and the complicated and changing hydrology experienced between the different seasons.

  6. The human footprint in the carbon cycle of temperate and boreal forests

    Science.gov (United States)

    Magnani, Federico; Mencuccini, Maurizio; Borghetti, Marco; Berbigier, Paul; Berninger, Frank; Delzon, Sylvain; Grelle, Achim; Hari, Pertti; Jarvis, Paul G.; Kolari, Pasi; Kowalski, Andrew S.; Lankreijer, Harry; Law, Beverly E.; Lindroth, Anders; Loustau, Denis; Manca, Giovanni; Moncrieff, John B.; Rayment, Mark; Tedeschi, Vanessa; Valentini, Riccardo; Grace, John

    2007-06-01

    Temperate and boreal forests in the Northern Hemisphere cover an area of about 2×107square kilometres and act as a substantial carbon sink (0.6-0.7 petagrams of carbon per year). Although forest expansion following agricultural abandonment is certainly responsible for an important fraction of this carbon sink activity, the additional effects on the carbon balance of established forests of increased atmospheric carbon dioxide, increasing temperatures, changes in management practices and nitrogen deposition are difficult to disentangle, despite an extensive network of measurement stations. The relevance of this measurement effort has also been questioned, because spot measurements fail to take into account the role of disturbances, either natural (fire, pests, windstorms) or anthropogenic (forest harvesting). Here we show that the temporal dynamics following stand-replacing disturbances do indeed account for a very large fraction of the overall variability in forest carbon sequestration. After the confounding effects of disturbance have been factored out, however, forest net carbon sequestration is found to be overwhelmingly driven by nitrogen deposition, largely the result of anthropogenic activities. The effect is always positive over the range of nitrogen deposition covered by currently available data sets, casting doubts on the risk of widespread ecosystem nitrogen saturation under natural conditions. The results demonstrate that mankind is ultimately controlling the carbon balance of temperate and boreal forests, either directly (through forest management) or indirectly (through nitrogen deposition).

  7. Interactions between hydrology and water chemistry shape bacterioplankton biogeography across boreal freshwater networks.

    Science.gov (United States)

    Niño-García, Juan Pablo; Ruiz-González, Clara; Del Giorgio, Paul A

    2016-07-01

    Disentangling the mechanisms shaping bacterioplankton communities across freshwater ecosystems requires considering a hydrologic dimension that can influence both dispersal and local sorting, but how the environment and hydrology interact to shape the biogeography of freshwater bacterioplankton over large spatial scales remains unexplored. Using Illumina sequencing of the 16S ribosomal RNA gene, we investigate the large-scale spatial patterns of bacterioplankton across 386 freshwater systems from seven distinct regions in boreal Québec. We show that both hydrology and local water chemistry (mostly pH) interact to shape a sequential structuring of communities from highly diverse assemblages in headwater streams toward larger rivers and lakes dominated by fewer taxa. Increases in water residence time along the hydrologic continuum were accompanied by major losses of bacterial richness and by an increased differentiation of communities driven by local conditions (pH and other related variables). This suggests that hydrology and network position modulate the relative role of environmental sorting and mass effects on community assembly by determining both the time frame for bacterial growth and the composition of the immigrant pool. The apparent low dispersal limitation (that is, the lack of influence of geographic distance on the spatial patterns observed at the taxonomic resolution used) suggests that these boreal bacterioplankton communities derive from a shared bacterial pool that enters the networks through the smallest streams, largely dominated by mass effects, and that is increasingly subjected to local sorting of species during transit along the hydrologic continuum.

  8. The role of entrainment in surface-atmosphere interactions over the boreal forest

    Energy Technology Data Exchange (ETDEWEB)

    Davis, K.J. [Minnesota Univ., St. Paul, MN (United States). Dept. of Soil Science; Lenschow, D.H.; Oncley, S.P. [National Center for Atmospheric Research, Boulder, Colorado (United States); Kiemle, C.; Ehret, G.; Giez, A. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere; Mann, J. [Risoe National Lab., Roskilde (Denmark)

    1997-07-01

    We present a description of the evolution of the convective boundary layer (CBL) over the boreal forests of Saskatchewan and Manitoba, as observed by the national center for atmospheric research (NCAR) Electra research aircraft during the 1994 boreal ecosystem-atmosphere study (BOREAS). All observations were made between 1530 and 2230 UT (0930-1630 local solar time, LST). We show that the CBL flux divergence often led to drying of the CBL over the course of the day, with the greatest drying (approaching 0.5 gkg{sup -1}hr{sup -1}) observed in the morning, 1000-1200 LST, and decreasing over time to nearly no drying (0 to 0.1 gkg{sup -1}hr{sup -1}) by midafternoon (1500-1600 LST). The maximum warming (0.45 Khr{sup -1}) also occurred in the morning and decreased slightly to about 0.4 Khr{sup -1} by midafternoon. The CBL vapor pressure deficit (VPD) increases over the course of the day. A significant portion of this increase can be explained by the vertical flux divergence, though horizontal advection also appears to be important. We suggest a linkage between boundary layer growth, the vertical flux divergences, and boundary layer cloud formation, with cloud activity peaking at midday in response to rapid CBL growth, then decreasing somewhat later in the day in response to CBL warming and decreased growth. We also see evidence of feedback between increasing VPD and stomatal control. (orig.) 39 refs.

  9. Climbing the Slope of Enlightenment during NASA's Arctic Boreal Vulnerability Experiment

    Science.gov (United States)

    Griffith, P. C.; Hoy, E.; Duffy, D.; McInerney, M.

    2015-12-01

    The Arctic Boreal Vulnerability Experiment (ABoVE) is a new field campaign sponsored by NASA's Terrestrial Ecology Program and designed to improve understanding of the vulnerability and resilience of Arctic and boreal social-ecological systems to environmental change (http://above.nasa.gov). ABoVE is integrating field-based studies, modeling, and data from airborne and satellite remote sensing. The NASA Center for Climate Simulation (NCCS) has partnered with the NASA Carbon Cycle and Ecosystems Office (CCEO) to create a high performance science cloud for this field campaign. The ABoVE Science Cloud combines high performance computing with emerging technologies and data management with tools for analyzing and processing geographic information to create an environment specifically designed for large-scale modeling, analysis of remote sensing data, copious disk storage for "big data" with integrated data management, and integration of core variables from in-situ networks. The ABoVE Science Cloud is a collaboration that is accelerating the pace of new Arctic science for researchers participating in the field campaign. Specific examples of the utilization of the ABoVE Science Cloud by several funded projects will be presented.

  10. Simulating boreal forest carbon dynamics after stand-replacing fire disturbance: insights from a global process-based vegetation model

    Science.gov (United States)

    Yue, C.; Ciais, P.; Luyssaert, S.; Cadule, P.; Harden, J.; Randerson, J.; Bellassen, V.; Wang, T.; Piao, S.L.; Poulter, B.; Viovy, N.

    2013-01-01

    Stand-replacing fires are the dominant fire type in North American boreal forests. They leave a historical legacy of a mosaic landscape of different aged forest cohorts. This forest age dynamics must be included in vegetation models to accurately quantify the role of fire in the historical and current regional forest carbon balance. The present study adapted the global process-based vegetation model ORCHIDEE to simulate the CO2 emissions from boreal forest fire and the subsequent recovery after a stand-replacing fire; the model represents postfire new cohort establishment, forest stand structure and the self-thinning process. Simulation results are evaluated against observations of three clusters of postfire forest chronosequences in Canada and Alaska. The variables evaluated include: fire carbon emissions, CO2 fluxes (gross primary production, total ecosystem respiration and net ecosystem exchange), leaf area index, and biometric measurements (aboveground biomass carbon, forest floor carbon, woody debris carbon, stand individual density, stand basal area, and mean diameter at breast height). When forced by local climate and the atmospheric CO2 history at each chronosequence site, the model simulations generally match the observed CO2 fluxes and carbon stock data well, with model-measurement mean square root of deviation comparable with the measurement accuracy (for CO2 flux ~100 g C m−2 yr−1, for biomass carbon ~1000 g C m−2 and for soil carbon ~2000 g C m−2). We find that the current postfire forest carbon sink at the evaluation sites, as observed by chronosequence methods, is mainly due to a combination of historical CO2 increase and forest succession. Climate change and variability during this period offsets some of these expected carbon gains. The negative impacts of climate were a likely consequence of increasing water stress caused by significant temperature increases that were not matched by concurrent increases in precipitation. Our simulation

  11. Simulating boreal forest carbon dynamics after stand-replacing fire disturbance: insights from a global process-based vegetation model

    Directory of Open Access Journals (Sweden)

    C. Yue

    2013-04-01

    Full Text Available Stand-replacing fires are the dominant fire type in North American boreal forest and leave a historical legacy of a mosaic landscape of different aged forest cohorts. To accurately quantify the role of fire in historical and current regional forest carbon balance using models, one needs to explicitly simulate the new forest cohort that is established after fire. The present study adapted the global process-based vegetation model ORCHIDEE to simulate boreal forest fire CO2 emissions and follow-up recovery after a stand-replacing fire, with representation of postfire new cohort establishment, forest stand structure and the following self-thinning process. Simulation results are evaluated against three clusters of postfire forest chronosequence observations in Canada and Alaska. Evaluation variables for simulated postfire carbon dynamics include: fire carbon emissions, CO2 fluxes (gross primary production, total ecosystem respiration and net ecosystem exchange, leaf area index (LAI, and biometric measurements (aboveground biomass carbon, forest floor carbon, woody debris carbon, stand individual density, stand basal area, and mean diameter at breast height. The model simulation results, when forced by local climate and the atmospheric CO2 history on each chronosequence site, generally match the observed CO2 fluxes and carbon stock data well, with model-measurement mean square root of deviation comparable with measurement accuracy (for CO2 flux ~100 g C m−2 yr−1, for biomass carbon ~1000 g C m−2 and for soil carbon ~2000 g C m−2. We find that current postfire forest carbon sink on evaluation sites observed by chronosequence methods is mainly driven by historical atmospheric CO2 increase when forests recover from fire disturbance. Historical climate generally exerts a negative effect, probably due to increasing water stress caused by significant temperature increase without sufficient increase in precipitation. Our simulation results

  12. Simulating boreal forest carbon dynamics after stand-replacing fire disturbance: insights from a global process-based vegetation model

    Science.gov (United States)

    Yue, C.; Ciais, P.; Luyssaert, S.; Cadule, P.; Harden, J.; Randerson, J.; Bellassen, V.; Wang, T.; Piao, S. L.; Poulter, B.; Viovy, N.

    2013-12-01

    Stand-replacing fires are the dominant fire type in North American boreal forests. They leave a historical legacy of a mosaic landscape of different aged forest cohorts. This forest age dynamics must be included in vegetation models to accurately quantify the role of fire in the historical and current regional forest carbon balance. The present study adapted the global process-based vegetation model ORCHIDEE to simulate the CO2 emissions from boreal forest fire and the subsequent recovery after a stand-replacing fire; the model represents postfire new cohort establishment, forest stand structure and the self-thinning process. Simulation results are evaluated against observations of three clusters of postfire forest chronosequences in Canada and Alaska. The variables evaluated include: fire carbon emissions, CO2 fluxes (gross primary production, total ecosystem respiration and net ecosystem exchange), leaf area index, and biometric measurements (aboveground biomass carbon, forest floor carbon, woody debris carbon, stand individual density, stand basal area, and mean diameter at breast height). When forced by local climate and the atmospheric CO2 history at each chronosequence site, the model simulations generally match the observed CO2 fluxes and carbon stock data well, with model-measurement mean square root of deviation comparable with the measurement accuracy (for CO2 flux ~100 g C m-2 yr-1, for biomass carbon ~1000 g C m-2 and for soil carbon ~2000 g C m-2). We find that the current postfire forest carbon sink at the evaluation sites, as observed by chronosequence methods, is mainly due to a combination of historical CO2 increase and forest succession. Climate change and variability during this period offsets some of these expected carbon gains. The negative impacts of climate were a likely consequence of increasing water stress caused by significant temperature increases that were not matched by concurrent increases in precipitation. Our simulation results

  13. Spatial variations in the molecular diversity of dissolved organic matter in water moving through a boreal forest in eastern Finland

    Science.gov (United States)

    Ide, Jun’ichiro; Ohashi, Mizue; Takahashi, Katsutoshi; Sugiyama, Yuko; Piirainen, Sirpa; Kortelainen, Pirkko; Fujitake, Nobuhide; Yamase, Keitaro; Ohte, Nobuhito; Moritani, Mina; Hara, Miyako; Finér, Leena

    2017-01-01

    Dissolved organic matter (DOM) strongly affects water quality within boreal forest ecosystems. However, how the quality of DOM itself changes spatially is not well understood. In this study, to examine how the diversity of DOM molecules varies in water moving through a boreal forest, the number of DOM molecules in different water samples, i.e., rainwater, throughfall, soil water, groundwater, and stream water was determined using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in Norway spruce and Scots pine stands in eastern Finland during May and June 2010. The number of molecular compounds identified by FT-ICR MS (molecular diversity) ranged from 865 to 2,194, revealing large DOM molecular diversity in the water samples. Additionally, some of the molecular compounds were shared between different water samples. The DOM molecular diversity linearly correlated with the number of low-biodegradable molecules, such as, lignin-like molecules (lignins), but not with dissolved organic carbon concentration. The number of lignins shared between different sampling locations was larger than that of any other biomolecular class. Our results suggest that low-biodegradable molecules, especially lignins, regulate spatial variations in DOM molecular diversity in boreal forests. PMID:28186141

  14. Habitat associations drive species vulnerability to climate change in boreal forests

    DEFF Research Database (Denmark)

    Mazziotta, Adriano; Triviño, Maria; Tikkanen, Olli Pekka;

    2016-01-01

    Species climate change vulnerability, their predisposition to be adversely affected, has been assessed for a limited portion of biodiversity. Our knowledge of climate change impacts is often based only on exposure, the magnitude of climatic variation in the area occupied by the species, even...... scenarios. However, climate change will potentially reduce habitat suitability for ~9–43 % of the threatened deadwood-associated species. This loss is likely caused by future increase in timber extraction and decomposition rates causing higher deadwood turnover, which have a strong negative effect on boreal...... forest biodiversity. Our results are species- and scenario-specific. Diversified forest management and restoration ensuring deadwood resources in the landscape would allow the persistence of species whose capacity of delivering important supporting ecosystem services can be undermined by climate change....

  15. Riparian woodland encroachment following flow regulation: a comparative study of Mediterranean and Boreal streams

    Directory of Open Access Journals (Sweden)

    Dolores Bejarano M.

    2011-10-01

    Full Text Available Water development accompanying mankind development has turned rivers into endangered ecosystems. Improving the understanding of ecological responses to river management actions is a key issue for assuring sustainable water management. However, few studies have been published where ecological metrics have been quantified in response to various degrees of flow alteration. In this work, changes in natural distribution of trees and shrubs within the riparian corridor (as indicator of the ecological status of the fluvial ecosystem were quantified at multiple sites along a flow alteration gradient (as indicator of impact along two regulated river reaches, one Boreal and the other Mediterranean, each downstream of a dam. Based on the obtained relationships we evaluated differences in response trends related to local physico-climatic factors of the two biomes and regarding to differing life-forms. Woody vegetation establishment patterns represented objective indicators of ecological responses to flow alteration. We found different responses between life-forms. Both trees and shrubs migrated downwards to the channel after dam closure, but shrubs were most impacted under higher degrees of flow alteration in terms of lateral movement. In addition, our results show clear longitudinal recovery trends of natural patterns of tree and shrub distribution corresponding to a decrease in intensity of hydrologic alteration in the Boreal river. However, vegetation encroachment persisted along the entire Mediterranean study reach. This may result from a relatively low gradient of decrease of hydrologic alteration with distance from the dam, coupled with other overlapping pressures and the mediating effect of physico-climatic characteristics on vegetation responses.

  16. Increased autumn rainfall disrupts predator-prey interactions in fragmented boreal forests.

    Science.gov (United States)

    Terraube, Julien; Villers, Alexandre; Poudré, Léo; Varjonen, Rauno; Korpimäki, Erkki

    2016-07-02

    There is a pressing need to understand how changing climate interacts with land-use change to affect predator-prey interactions in fragmented landscapes. This is particularly true in boreal ecosystems facing fast climate change and intensification in forestry practices. Here, we investigated the relative influence of autumn climate and habitat quality on the food-storing behaviour of a generalist predator, the pygmy owl, using a unique data set of 15 850 prey items recorded in western Finland over 12 years. Our results highlighted strong effects of autumn climate (number of days with rainfall and with temperature abundance and were more prone to switch from main prey to alternative prey (passerine birds) depending on local climate conditions. High-quality habitat may allow pygmy owls to buffer negative effects of inclement weather and cyclic variation in vole abundance. Additionally, our results evidenced sex-specific trends in body condition, as the scaled mass index of smaller males increased while the scaled mass index of larger females decreased over the study period, probably due to sex-specific foraging strategies and energy requirements. Long-term temporal stability in local vole abundance refutes the hypothesis of climate-driven change in vole abundance and suggests that rainier autumns could reduce the vulnerability of small mammals to predation by pygmy owls. As small rodents are key prey species for many predators in northern ecosystems, our findings raise concern about the impact of global change on boreal food webs through changes in main prey vulnerability.

  17. Thermokarst Rates Intensify Due to Climate Change and Forest Fragmentation in an Alaskan Boreal Forest Lowland

    Science.gov (United States)

    Lara, M. J.; Genet, H.; McGuire, A. D.; Euskirchen, E. S.; Zhang, Y.; Brown, D. N.; Jorgenson, T.; Romanovsky, V. E.; Breen, A. L.; Bolton, W. R.

    2015-12-01

    Lowland boreal forest ecosystems in Alaska are dominated by wetlands comprised of a complex mosaic of fens, collapse scar-bogs, low shrub/scrub, and forests growing on elevated ice rich permafrost soils. Thermokarst has affected the lowlands of the Tanana Flats in central Alaska for centuries, as thawing permafrost collapses forests that transition to wetlands. Located within the discontinuous permafrost zone, this region has significantly warmed over the past half-century, and much of these carbon-rich permafrost soils are now within ~0.5o C of thawing. Increases in the collapse of lowland boreal forests in response to warming may have consequences for the climate system. This study evaluates the trajectories and potential drivers of 60 years of forest change in a landscape subjected to permafrost thaw in unburned dominant forest types (paper birch and black spruce) associated with location on elevated permafrost plateau and across multiple time periods (1949, 1978, 1986, 1998 and 2009) using historical and contemporary aerial and satellite images for change detection. We developed (i) a deterministic statistical model to evaluate the potential climatic controls on forest change using gradient boosting and regression tree analysis, and (ii) a 30x30 m land cover map of the Tanana Flats to estimate the potential landscape-level losses of forest area due to thermokarst from 1949 to 2009. Over the 60-year period, we observed a nonlinear loss of birch forests and a relatively continuous gain of spruce forest associated with thermokarst and forest succession, respectively. Gradient boosting and regression tree models identify precipitation and forest fragmentation as the primary factors controlling birch and spruce forest change, respectively. Between 1950-2009 landscape-level analysis estimates a transition of ~15 km² of birch forest area to wetlands on the Tanana Flats, where the greatest change followed warm periods. This work highlights the vulnerability of lowland

  18. Deciduous Tree Species Alter Nitrogen and Phosphorus Availability in Mid-successional Alaskan Boreal Forest

    Science.gov (United States)

    Melvin, A. M.; Mack, M. C.; Johnstone, J. F.; Schuur, E. A.

    2013-12-01

    In Alaskan boreal forest, increased fire severity associated with climate change is altering successional processes and ecosystem nutrient dynamics. Fire is a common disturbance in Interior Alaska and typically burns forests dominated by black spruce (Picea mariana), a tree species associated with slow nutrient turnover and high soil organic matter accumulation rates. Historically, low severity fires have driven black spruce regeneration post-fire, thereby maintaining slow nutrient cycling rates and large soil organic matter stocks. In contrast, high severity fires consume the organic layer and can lead to the establishment of deciduous tree species on exposed mineral soil, which produce less recalcitrant leaf litter and exhibit faster nutrient cycling rates. To improve our understanding of the long-term impacts of tree species composition on nutrient cycling in boreal forest, we quantified nitrogen (N) cycling rates and estimated soil N, phosphorus (P), and base cation pools in adjacent, mid-successional stands of black spruce and Alaska paper birch (Betula neoalaskana) that established following a 1960 fire near Fairbanks, Alaska. Results indicate significantly higher net N mineralization in paper birch soils relative to black spruce for both the fibric organic layer and top 10 cm of mineral soil during 30-day and 90-day lab incubation studies. Net nitrification was significantly higher in the paper birch fibric layer after 90 days. Total soil N concentrations did not differ between paper birch and black spruce stands, however the black spruce organic layer was significantly larger than that of birch, resulting in larger organic layer N stocks (130 vs. 87 g N m2). In contrast, total P concentrations were significantly higher in the organic layer in birch forest, but the total P stocks did not differ significantly between species because of the larger mass of soil organic matter in the black spruce. These findings suggest that a shift towards greater deciduous

  19. Precipitation-induced runoff and leaching from milled peat mining mires by peat types : a comparative method for estimating the loading of water bodies during peat pruduction

    OpenAIRE

    SvahnbÀck, Lasse

    2007-01-01

    Precipitation-induced runoff and leaching from milled peat mining mires by peat types: a comparative method for estimating the loading of water bodies during peat production. This research project in environmental geology has arisen out of an observed need to be able to predict more accurately the loading of watercourses with detrimental organic substances and nutrients from already existing and planned peat production areas, since the authorities capacity for insisting on such predicti...

  20. Estimating aboveground biomass in the boreal forests of the Yukon River Basin, Alaska

    Science.gov (United States)

    Ji, L.; Wylie, B. K.; Nossov, D.; Peterson, B.; Waldrop, M. P.; McFarland, J.; Alexander, H. D.; Mack, M. C.; Rover, J. A.; Chen, X.

    2011-12-01

    Quantification of aboveground biomass (AGB) in Alaska's boreal forests is essential to accurately evaluate terrestrial carbon stocks and dynamics in northern high-latitude ecosystems. However, regional AGB datasets with spatially detailed information (1 m tall), which were converted to plot-level AGB using allometric equations. We acquired Landsat Enhanced Thematic Mapper Plus (ETM+) images from the Web Enabled Landsat Data (WELD) that provides multi-date composites of top-of-atmosphere reflectance and brightness temperature for Alaska. From the WELD images, we generated a three-year (2008 - 2010) image composite for the Yukon River Basin using a series of compositing criteria including non-saturation, non-cloudiness, maximal normalize difference vegetation index (NDVI), and maximal brightness temperature. Airborne lidar datasets were acquired for two sub-regions in the central basin in 2009, which were converted to vegetation height datasets using the bare-earth digital surface model (DSM) and the first-return DSM. We created a multiple regression model in which the response variable was the field-observed AGB and the predictor variables were Landsat-derived reflectance, brightness temperature, and spectral vegetation indices including NDVI, soil adjusted vegetation index (SAVI), enhanced vegetation index (EVI), normalized difference infrared index (NDII), and normalized difference water index (NDWI). Principal component analysis was incorporated in the regression model to remedy the multicollinearity problems caused by high correlations between predictor variables. The model fitted the observed data well with an R-square of 0.62, mean absolute error of 29.1 Mg/ha, and mean bias error of 3.9 Mg/ha. By applying this model to the Landsat mosaic, we generated a 30-m AGB map for the boreal forests in the Yukon River Basin. Validation of the Landsat-derived AGB using the lidar dataset indicated a significant correlation between the AGB estimates and the lidar

  1. Carbon in boreal coniferous forest soil

    Energy Technology Data Exchange (ETDEWEB)

    Westman, C.J.; Ilvesniemi, H.; Liski, J.; Mecke, M. [Helsinki Univ. (Finland). Dept. of Forest Ecology; Fritze, H.; Helmisaari, H.S.; Pietikaeinen, J.; Smolander, A. [Finnish Forest Research Inst., Vantaa (Finland)

    1996-12-31

    The working hypothesis of the research was that the soil of boreal forests is a large carbon store and the amount of C is still increasing in young soils, like in the forest soils of Finland, which makes these soils important sinks for atmospheric CO{sub 2}. Since the processes defining the soil C balance, primary production of plants and decomposition, are dependent on environmental factors and site properties, it was assumed that the organic carbon pool in the soil is also dependent on the same factors. The soil C store is therefore likely to change in response to climatic warming. The aim of this research was to estimate the C balance of forest soil in Finland and predict changes in the balance in response to changes in climatic conditions. To achieve the aim (1) intensive empirical experimentation on the density of C in different pools in the soil and on fluxes between the pools was done was done, (2) the effect of site fertility and climate on the amount and properties of organic C in forest soil was investigated and (3) dynamic modelling for investigating dynamics of the soil C storage was used

  2. Upscaling methane emission hotspots in boreal peatlands

    Directory of Open Access Journals (Sweden)

    F. Cresto Aleina

    2015-10-01

    Full Text Available Upscaling the properties and the effects of small-scale surface heterogeneities to larger scales is a challenging issue in land surface modeling. We developed a novel approach to upscale local methane emissions in a boreal peatland from the micro-topographic scale to the landscape-scale. We based this new parameterization on the analysis of the water table pattern generated by the Hummock–Hollow model, a micro-topography resolving model for peatland hydrology. We introduce this parameterization of methane hotspots in a global model-like version of the Hummock–Hollow model, that underestimates methane emissions. We tested the robustness of the parameterization by simulating methane emissions for the next century forcing the model with three different RCP scenarios. The Hotspot parameterization, despite being calibrated for the 1976–2005 climatology, mimics the output of the micro-topography resolving model for all the simulated scenarios. The new approach bridges the scale gap of methane emissions between this version of the model and the configuration explicitly resolving micro-topography.

  3. Competitive interactions among raptors in boreal forests.

    Science.gov (United States)

    Hakkarainen, Harri; Mykrä, Sakari; Kurki, Sami; Tornberg, Risto; Jungell, Sven

    2004-11-01

    We examined inter-specific interactions among goshawks ( Accipiter gentilis), common buzzards (Buteo buteo) and honey buzzards (Pernis apivorus) in western Finland in 1983-1996. Because goshawks are among the largest birds of prey species in boreal forests they may take over the nest of smaller and less-competitive forest-dwelling raptors when searching for suitable places for breeding. Accordingly, more than half of newly established goshawk territories were found on the territories previously occupied by the common buzzard and the honey buzzard. Otherwise, territory sharing between these species was rare. Fledgling production of honey buzzards was not associated with the presence of goshawks, probably owing to the almost 2 months later onset of breeding. This probably decreases competitive interactions between these two species. An intensive interference competition, instead, seemed to be evident between common buzzards and goshawks, because the fledgling production of common buzzards was decreased by 20% as a result of failures during incubation and nestling period in the vicinity (raptors, imposing upon the original owners of the nest, because building a large stick nest is probably energetically costly. As a large raptor, the goshawk apparently has a competitive advantage over smaller ones, and may have an ever-increasing impact on smaller birds of prey, if there is a lack of sheltered forests inducing competition for the available nest sites.

  4. Long-term (∼57 ka) controls on mercury accumulation in the Southern Hemisphere reconstructed using a peat record from Pinheiro mire (Minas Gerais, Brazil).

    Science.gov (United States)

    Pérez-Rodríguez, Marta; Horák-Terra, Ingrid; Rodríguez-Lado, Luis; Aboal, Jesús R; Martínez Cortizas, Antonio

    2015-02-03

    Natural archives have been used to reconstruct mercury atmospheric deposition at different spatial and temporal scales during the Holocene in the Northern Hemisphere. In this study, we present the results from a Brazilian mountain mire (Pinheiro mire, Minas Gerais, SE Brazil), extending back to ∼57 ka. The core was analyzed for mercury concentration, organic matter content, organic carbon isotopic composition, and tracers of mineral matter flux. Principal components analysis followed by principal components regression enabled us to determine the evolution of the weight of the latent processes governing the accumulation of mercury through time. We show that climate change was the main driver for the variations of mercury concentrations, either indirectly by (i) enhancing soil erosion in the mire's catchment, which led to a decrease in mercury concentration due to dilution by low mercury-containing mineral matter, (ii) increasing regional dust deposition, which resulted in increased concentrations, or directly, by long-term changes in atmospheric wet deposition (arid vs humid periods). Internal peat processes (i.e., decomposition and mass loss) had a minor influence at the time scale represented by the core.

  5. Precipitation-induced runoff and leaching from milled peat mining mires by peat types: A comparative method for estimating the loading of water bodies during peat production

    Energy Technology Data Exchange (ETDEWEB)

    Svahnbaeck, L.

    2007-07-01

    Finland has some 10 million hectares of peatland, accounting for almost a third of its total area. Macroclimatic conditions have varied in the course of the Holocene growth and development of this peatland, and with them the habitats of the peat-forming plants. Temperatures and moisture conditions have played a significant role in determining the dominant species of mire plants growing there at any particular time, the resulting mire types and the accumulation and deposition of plant remains to form the peat. While in a natural state the mires of Finland have functioned as carbon dioxide sinks throughout the post-glacial period, but the ditching of peatland for forestry and agriculture, amounting to some 5,7 million hectares in Finland, has affected their water balance, especially over the last hundred years, and has thereby altered the quantity and species composition of the mire vegetation. The invasion of trees and woody plants to replace the typical mire plants following ditching for forestry purposes has stimulated the decomposition of the already accumulated peat and promoted the humification of the microbiologically active root system layer. The above climatic, environmental and mire development factors, together with ditching, have contributed, and continue to contribute, to the existence of peat horizons that differ in their physical and chemical properties, leading to differences in material transport between peatlands in a natural state and mires that have been ditched or prepared for forestry and peat production. Watercourse loading from the ditching of mires or their use for peat production can have detrimental effects on river and lake environments and their recreational use, especially where oxygen-consuming organic solids and soluble organic substances and nutrients are concerned. It has not previously been possible, however, to estimate in advance the watercourse loading likely to arise from ditching and peat production on the basis of the

  6. Spring Hydrology Determines Summer Net Carbon Uptake in Northern Ecosystems

    Science.gov (United States)

    Yi, Yonghong; Kimball, John; Reichle, Rolf H.

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the Normalized Difference Vegetation Index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (greater than or equal to 50N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

  7. Assessment of boreal forest historical C dynamics in Yukon River Basin: relative roles of warming and fire regime change

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Fengming [ORNL; Yi, Shuhua [Cold and Arid Regions Environmental and Engineering Research Institute, CAS; McGuire, A. David [University of Alaska; Johnson, Kristopher D [University of Alaska, Fairbanks; Liang, Jingjing [University of Alaska, Fairbanks; Harden, Jennifer [USGS, Menlo Park, CA; Kasischke, Eric S. [University of Maryland, College Park; Kurz, Werner [Canadian Forest Service

    2012-01-01

    Carbon (C) dynamics of boreal forest ecosystems have substantial implications for efforts to mitigate the rise of atmospheric CO2 and may be substantially influenced by warming and changing wildfire regimes. In this study we applied a large-scale ecosystem model that included dynamics of organic soil horizons and soil organic matter characteristics of multiple pools to assess forest C stock changes of the Yukon River Basin (YRB) in Alaska, USA, and Canada from 1960 through 2006, a period characterized by substantial climate warming and increases in wildfire. The model was calibrated for major forests with data from long-term research sites and evaluated using a forest inventory database. The regional assessment indicates that forest vegetation C storage increased by 46 Tg C, but that total soil C storage did not change appreciably during this period. However, further analysis suggests that C has been continuously lost from the mineral soil horizon since warming began in the 1970s, but has increased in the amorphous organic soil horizon. Based on a factorial experiment, soil C stocks would have increased by 158 Tg C if the YRB had not undergone warming and changes in fire regime. The analysis also identified that warming and changes in fire regime were approximately equivalent in their effects on soil C storage, and interactions between these two suggests that the loss of organic horizon thickness associated with increases in wildfire made deeper soil C stocks more vulnerable to loss via decomposition. Subbasin analyses indicate that C stock changes were primarily sensitive to the fraction of burned forest area within each subbasin and that boreal forest ecosystems in the YRB are currently transitioning from being sinks to sources at ;0.7% annual area burned. We conclude that it is important for international mitigation efforts focused on controlling atmospheric CO2 to consider how climate warming and changes in fire regime may concurrently affect the CO2 sink

  8. The summertime Boreal forest field measurement intensive (HUMPPA-COPEC-2010: an overview of meteorological and chemical influences

    Directory of Open Access Journals (Sweden)

    J. Williams

    2011-10-01

    Full Text Available This paper describes the background, instrumentation, goals, and the regional influences on the HUMPPA-COPEC intensive field measurement campaign, conducted at the Boreal forest research station SMEAR II (Station for Measuring Ecosystem-Atmosphere Relation in Hyytiälä, Finland from 12 July–12 August 2010. The prevailing meteorological conditions during the campaign are examined and contrasted with those of the past six years. Back trajectory analyses show that meteorological conditions at the site in 2010 were characterized by a higher proportion of southerly flow than in the other years studied. As a result the summer of 2010 was anomalously warm and high in ozone making the campaign relevant for the analysis of possible future climates. A comprehensive land use analysis, provided on both 5 and 50 km scales, shows that the main vegetation types surrounding the site on both the regional and local scales are: coniferous forest (Scots pine and/or Norway spruce; mixed forest (Birch and conifers; and woodland scrub (e.g. Willows, Aspen; indicating that the campaign results can be taken as representative of the Boreal forest ecosystem. In addition to the influence of biogenic emissions, the measurement site was occasionally impacted by sources other than vegetation. Specific tracers have been used here to identify the time periods when such sources have impacted the site namely: biomass burning (acetonitrile and CO, urban anthropogenic pollution (pentane and SO2 and the nearby Korkeakoski sawmill (enantiomeric ratio of chiral monoterpenes. None of these sources dominated the study period, allowing the Boreal forest summertime emissions to be assessed and contrasted with various other source signatures.

  9. The summertime Boreal forest field measurement intensive (HUMPPA-COPEC-2010: an overview of meteorological and chemical influences

    Directory of Open Access Journals (Sweden)

    J. Williams

    2011-05-01

    Full Text Available This paper describes the background, instrumentation, goals, and the regional influences on the HUMPPA-COPEC intensive field measurement campaign, conducted at the Boreal forest research station SMEAR II (Station for Measuring Ecosystem-Atmosphere Relation in Hyytiälä, Finland from 12 July–12 August 2010. The prevailing meteorological conditions during the campaign are examined and contrasted with those of the past six years. Back trajectory analyses show that meteorological conditions at the site were characterized by a higher proportion of southerly flow. As a result the summer of 2010 was anomalously warm and high in ozone making the campaign relevant for the analysis of possible future climates. A comprehensive land use analysis, provided on both 5 and 50 km scales, shows that the main vegetation types surrounding the site on both the regional and local scales are: coniferous forest (Scots pine and/or Norway spruce; mixed forest (Birch and conifers; and woodland scrub (e.g. Willows, Aspen; indicating that the campaign results can be taken as representative of the Boreal forest ecosystem. In addition to the influence of biogenic emissions, the measurement site was occasionally impacted by sources other than vegetation. Specific tracers have been used here to identify the time periods when such sources have impacted the site namely: biomass burning (acetonitrile and CO, urban anthropogenic pollution (pentane and SO2 and the nearby Korkeakoski sawmill (enantiomeric ratio of chiral monoterpenes. None of these sources dominated the study period, allowing the Boreal forest summertime emissions to be assessed and contrasted with various other source signatures.

  10. Long-term 15N tracking from biological N fixation across different plant and humus components of the boreal forest

    Science.gov (United States)

    Arroniz-Crespo, Maria; Jones, David L.; Zackrisson, Olle; Nilsson, Marie-Charlotte; DeLuca, Thomas H.

    2014-05-01

    Biological N2 fixation by cyanobacteria associated with feather mosses is an important cog in the nitrogen (N) cycle of boreal forests; still, our understanding of the turnover and fate of N fixed by this association remains greatly incomplete. The 15N signature of plants and soil serves as a powerful tool to explore N dynamics in forest ecosystems. In particular, in the present study we aimed to investigate the contribution of N2 fixation to δ15N signatures of plants and humus component of the boreal forest. Here we present results from a long-term (7 years) tacking of labelled 15N2 across the humus layer, seedlings of the tree species Pinus sylvestris, two common dwarf shrub species (Empetrum hermaphroditum and Vaccinium vitis-idaea) and the feather moss Pleurozium schreibery. The enriched experiment was conducted in 2005 in a natural boreal forest in northern Sweden. Two different treatments (10% 15N2 headspace enrichment and control) were setup in nine different plots (0.5 x 0.5 m) within the forest. We observed a significant reduction of δ15N signature of the 15N-enriched moss that could be explained by a growth dilution effect. Nevertheless, after 5 years since 15N2 enrichment some of the label 15N was still detected on the moss and in particular in the dead tissue. We could not detect a clear transfer of the labelled 15N2 from the moss-cyanobacteria system to other components of the ecosystem. However, we found consistence relationship through time between increments of δ15N signature of some of the forest components in plots which exhibited higher N fixation rates in the moss. In particular, changes in natural abundance δ15N that could be associated with N fixation were more apparent in the humus layer, the dwarf shrub Vaccinium vitis-idaea and the pine seedlings when comparing across plots and years.

  11. Widespread negative correlations between black spruce growth and temperature across topographic moisture gradients in the boreal forest

    Science.gov (United States)

    Walker, Xanthe; Johnstone, Jill F.

    2014-05-01

    The responses of tree growth to recent climate warming may signal changes in the susceptibility of forest communities to compositional change and consequently impact a wide range of ecosystem processes and services. Previous research in the boreal forest has largely documented negative growth responses to climate in forest species and habitats characteristic of drier conditions, emphasizing the sensitivity of drier or warmer landscape positions to climate warming. In this study, we explored relationships between climate and tree-ring growth of black spruce, a dominant tree species typical of cool and moist habitats in the boreal forests of North America. We assessed how these responses varied with stand characteristics and landscape position across four different regions in Alaska and Yukon Territory. Approximately half of the trees measured across regions and topographic gradients exhibited reduced radial growth in response to warm temperatures in the previous growing season and current spring, which we interpret as a signal of drought stress. Although we found considerable variation in the growth responses of individual trees within sites, landscape position and stand characteristics were weak predictors of this variability, explaining ≦̸12% of the variation in any region. Our results indicate that future warming, particularly in spring, is likely to result in drought stress and a reduction of black spruce radial growth independent of region, landscape position, or stand characteristics. The occurrence of negative growth responses to temperature, even in cool and moist habitats, suggests that drought stress limitations may be more widespread in the northern boreal forest than previously anticipated, indicating broad sensitivity of ecosystem processes and services to climate change across a diverse range of habitat types.

  12. Soil carbon effluxes in ecosystems of Forsmark and Laxemar

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern (Dept. of Physical Geography and Ecosystem Analysis, Lund Univ. (Sweden))

    2007-12-15

    Soil carbon effluxes were estimated in a number of ecosystems in Laxemar and Forsmark investigations areas. It was done in a young Scots pine (Pinus sylvestris) stand, a wet deciduous stand, a poor fen and an agricultural field in the Laxemar investigation area in south-eastern Sweden (57 deg 5 min N, 16 deg 7 min E) and in a pasture, two Norway spruce (Picea abies) stands, a deciduous forest, a mire, a wet deciduous forest and a clear-cut in the Forsmark investigation area (60 deg 4 min N, 18 deg 2 min E). It was measured with the closed chamber technique in 2005 and 2006. Soil temperature at 10 cm depth, air temperature and photosynthetically active radiation (PAR) were also measured. Exponential regressions with soil respiration against air and soil temperature were used to estimate annual soil respiration. A hyperbolic curve with Gross Primary Production (GPP) against PAR was used for modelling GPP for the growing season in the poor fen and the agricultural area of Laxemar. The exponential regressions with soil respiration against air and soil temperature explained on average 33.6% and 44.0% of the variation, respectively. GPP of the ground vegetation were reducing soil carbon effluxes, in all stands but one of the spruce stands, the deciduous forest, the mire and the wet deciduous forest of Forsmark. The significant (all but spruce 2 in Forsmark) curves with GPP against PAR explained on average 22.7% of the variation in GPP. The cubic regressions with GPP against air temperature were only significant for the poor fen and the agricultural field in Laxemar and it explained on average 34.8% of the variation in GPP for these ecosystems. The exponential regressions with air and soil temperature against soil respiration could be used to temporally extrapolate the occasional field measurements. The hyperbolic curve with GPP against PAR could also be used for temporal extrapolation of GPP for the ecosystems without a tree layer, i.e. the poor fen and the agricultural

  13. Disturbance Regimes and Landscape Heterogeneity in the Boreal Forest

    Science.gov (United States)

    Lyons, E. A.; Sheng, Y.

    2014-12-01

    Circling the northern high latitudes, the boreal forest is the largest contiguous forest ecoregion in the world. Far from a homogeneous carpet of trees, the boreal forest is a patchwork of land cover types including evergreen and deciduous trees, meadows, lakes, and wetlands. Due to its size, location, and structure, the boreal forest is an important component of the regional and global climate system through storage of carbon in cold organic soils and direct influence on the solar energy budget. This study integrates remote sensing and GIS products from different sub-fields working in the pan-Arctic region to investigate fire and permafrost-degradation, the land cover shaping processes that help determine the fate of the boreal forest. These disturbance processes are subject to change with climate and hold the potential for rapid change to the structure of the boreal forest. We identify regions at risk for rapid change, quantify the contributions of different disturbance processes, and analyze patterns of post disturbance recovery.

  14. Designer ecosystems

    NARCIS (Netherlands)

    Awasthi, Ashutosh; Singh, Kripal; O'Grady, Audrey; Courtney, Ronan; Kalra, Alok; Singh, Rana Pratap; Cerda Bolinches, Artemio; Steinberger, Yosef; Patra, D.D.

    2016-01-01

    Increase in human population is accelerating the rate of land use change, biodiversity loss and habitat degradation, triggering a serious threat to life supporting ecosystem services. Existing strategies for biological conservation remain insufficient to achieve a sustainable human-nature relatio

  15. Twelve year interannual and seasonal variability of stream carbon export from a boreal peatland catchment

    Science.gov (United States)

    Leach, J. A.; Larsson, A.; Wallin, M. B.; Nilsson, M. B.; Laudon, H.

    2016-07-01

    Understanding stream carbon export dynamics is needed to accurately predict how the carbon balance of peatland catchments will respond to climatic and environmental change. We used a 12 year record (2003-2014) of continuous streamflow and manual spot measurements of total organic carbon (TOC), dissolved inorganic carbon (DIC), methane (CH4), and organic carbon quality (carbon-specific ultraviolet absorbance at 254 nm per dissolved organic carbon) to assess interannual and seasonal variability in stream carbon export for a peatland catchment (70% mire and 30% forest cover) in northern Sweden. Mean annual total carbon export for the 12 year period was 12.2 gCm-2 yr-1, but individual years ranged between 6 and 18 gCm-2 yr-1. TOC, which was primarily composed of dissolved organic carbon (>99%), was the dominant form of carbon being exported, comprising 63% to 79% of total annual exports, and DIC contributed between 19% and 33%. CH4 made up less than 5% of total export. When compared to previously published annual net ecosystem exchange (NEE) for the studied peatland system, stream carbon export typically accounted for 12 to 50% of NEE for most years. However, in 2006 stream carbon export accounted for 63 to 90% (estimated uncertainty range) of NEE due to a dry summer which suppressed NEE, followed by a wet autumn that resulted in considerable stream export. Runoff exerted a primary control on stream carbon export from this catchment; however, our findings suggest that seasonal variations in biologic and hydrologic processes responsible for production and transport of carbon within the peatland were secondary influences on stream carbon export. Consideration of these seasonal dynamics is needed when predicting stream carbon export response to environmental change.

  16. Epigeous fruiting bodies of ectomycorrhizal fungi as indicators of soil fertility and associated nitrogen status of boreal forests.

    Science.gov (United States)

    Kranabetter, J M; Friesen, J; Gamiet, S; Kroeger, P

    2009-10-01

    Soil fertility and associated nitrogen (N) status was a key ecosystem attribute, and surveys of ectomycorrhizal fungal (EMF) communities via epigeous fruiting bodies could provide an effective biotic indicator of forest soil productivity. We explored the utility of aboveground EMF communities in this regard by surveying sporocarps over a 3-year period from contrasting plant associations of southern old-growth boreal forests of British Columbia (Canada). Cumulative richness ranged from 39 to 89 EMF species per plot (0.15 ha) and followed a skewed parabolic correlation with foliar N concentrations and soil N availability. EMF species composition was consistently distinct in ordinations and strongly correlated to the increasing rates of N mineralization aligned with soil productivity. Approximately 40 EMF species were specialists, as they collectively indicated oligotrophic, mesotrophic, and eutrophic nutrient regimes, while the remaining species were categorized as broadly tolerant (distributed over 100% of the N gradient), partially intolerant (approximately 70%), or satellites (rare). The functional organization of EMF communities reflected by distribution classes could help define the ecological integrity of forests, which was characterized in this boreal landscape by an average allotment of 20 broadly tolerant, 25 partially intolerant, 15 specialist, and ten satellite species per plot. Epigeous fruiting bodies provided a disparate yet complementary view to the belowground assessment of EMF communities that was valuable in identifying indicators for ecosystem monitoring.

  17. Tracking changes of forest carbon density following mega-fires: comparison studies in the Yellowstone National Park and Boreal Forests of Northeast China

    Science.gov (United States)

    Zhao, Feng; Huang, Chengquan; Huang, Chao; He, Hong; Zhu, Zhiliang

    2016-04-01

    Wildfires and post-fire management directly change C stored in biomass and soil pools, and can have indirect impacts on long-term C balance. Two mega fires occurred in the Yellowstone National Park (YNP) and the boreal forests of Northeast China in 1988 and 1987, respectively, making them ideal sites to examine and compare the effects of management and disturbances on regional carbon dynamics. In this study, we quantified effects of the 1988 Yellowstone fires on YNP carbon storages and fluxes. And then we tracked and modeled post-1988 forest carbon stocks change in YNP, and compared with simulation results of carbon stock changes in post-1987 fire boreal forests of Northeast China. Preliminary results show that in YNP, the mega fires in 1988 were responsible for an immediate loss of 900 g/m2 ecosystem average C density and it would take about a decade before the YNP ecosystem recover to the pre-fire average C condition. In boreal forests of Northeast China, fire reduced aboveground and belowground carbon by 230±60 g/m2 and 460±340 g/m2, respectively.

  18. The impact of simulated chronic nitrogen deposition on the biomass and N₂-fixation activity of two boreal feather moss-cyanobacteria associations.

    Science.gov (United States)

    Gundale, Michael J; Bach, Lisbet H; Nordin, Annika

    2013-01-01

    Bryophytes achieve substantial biomass and play several key functional roles in boreal forests that can influence how carbon (C) and nitrogen (N) cycling respond to atmospheric deposition of reactive nitrogen (Nr). They associate with cyanobacteria that fix atmospheric N₂, and downregulation of this process may offset anthropogenic Nr inputs to boreal systems. Bryophytes also promote soil C accumulation by thermally insulating soils, and changes in their biomass influence soil C dynamics. Using a unique large-scale (0.1 ha forested plots), long-term experiment (16 years) in northern Sweden where we simulated anthropogenic Nr deposition, we measured the biomass and N₂-fixation response of two bryophyte species, the feather mosses Hylocomium splendens and Pleurozium schreberi. Our data show that the biomass declined for both species; however, N₂-fixation rates per unit mass and per unit area declined only for H. splendens. The low and high treatments resulted in a 29% and 54% reduction in total feather moss biomass, and a 58% and 97% reduction in total N₂-fixation rate per unit area, respectively. These results help to quantify the sensitivity of feather moss biomass and N₂ fixation to chronic Nr deposition, which is relevant for modelling ecosystem C and N balances in boreal ecosystems.

  19. Historical anthropogenic contributions to mercury accumulation recorded by a peat core from Dajiuhu montane mire, central China.

    Science.gov (United States)

    Li, Yuanping; Ma, Chunmei; Zhu, Cheng; Huang, Run; Zheng, Chaogui

    2016-09-01

    Mercury (Hg) accumulation records spanning the last 16,000 years before present (yr BP, relative to AD 1950) were derived from a peat core collected from Dajiuhu mire, central China. The natural Hg concentration and accumulation rate (free from anthropogenic influence) were 135.5 ± 53.9 ng g(-1) and 6.5 ± 4.5 μg m(-2) yr(-1), respectively. The increase in Hg flux that started from a core depth of 96.5 cm (3358 cal yr BP) is independent of soil erosion and organic matter content. We attribute this to an increase in atmospheric Hg deposition derived from regional anthropogenic activities. Anthropogenic Hg accumulation rates (Hg-ARA) in the pre-industrial period peaked during the Ming and the early Qing dynasties (582-100 cal yr BP), with Hg-ARA of 9.9-24.6 and 10.7-24.4 μg m(-2) yr(-1), respectively. In the industrial interval (post∼1850 AD), Hg-ARA increased progressively and reached 32.7 μg m(-2) yr(-1) at the top of the core. Our results indicate the existence of regional atmospheric Hg pollution spanning the past ∼3400 years, and place recent Hg enrichment in central China in a broader historical context.

  20. Element concentrations in mosses and surface waters of western Canadian mires relative to precipitation chemistry and hydrology

    Energy Technology Data Exchange (ETDEWEB)

    Malmer, N. (Dept. of Ecology, Plant Ecology, Lund Univ., Lund (SE)); Horton, D.G. (Dept. of Botany, the Univ. of Iowa, Iowa City (US)); Vitt, D.H. (Dept. of Botany, the Univ. of Alberta, Edmonton, Alberta (CA))

    1992-01-01

    Concentrations of N, P, S, Na, K, Mg, Ca, Mn, Fe, Cu, Cd, Zn, Pb, Al, and AIA (acid insoluble ash) in mosses (three Sphagnum species and Tomenthypnum nitens, all hummock species) from a variety of mires, both ombrotrophic and minerotrophic, in the coastal western and central parts of Canada are considered in relation to surface water pH and concentrations of Na{sup +}, K{sup +}, Mg{sup 2+}, Ca{sup 2+}, Cl{sup -}, and SO{sub 4}{sup 2-}. Distinct west-east concentration gradients were present for most elements in both mosses and water, but there were correlations between surface water and moss concentrations only for Ca and Mg. On ombrotrophic sites and sites characterized by poor fen vegetation, wet deposition is the main source of elements in the surface water. On rich fen sites, additional Ca and Mg from surrounding soils change the elemental proportions. We conclude that hydrochemically the limit between poor and rich fen sites is more decisive than between bog and fen. The increase in Ca may give brown mosses a competitive advantage over Sphagnum. Moss concentrations of Na and Mg are the only ones decreasing inland. The constancy or inland increase of moss elemental concentrations may depend on either an increasing atmospheric supply (e.g. Pb), differences in moss growth rates (Especially N, P, and K) or site conditions related to the water regime (e.g. Fe and Al). (au).

  1. Peat humification and climate change: a multi-site comparison from mires in south-east Alaska

    Directory of Open Access Journals (Sweden)

    R.J. Payne

    2008-11-01

    Full Text Available Peatland records of Holocene palaeoclimate have been widely used in Europe. Their potential in western North America remains largely unexploited despite an abundance of candidate sites. Peat humification analysis is a widely used technique for palaeoclimatic inference from peatlands. This study attempts to demonstrate a climatic role in determining peat humification by comparing low-resolution peat humification records from five mires in south-east Alaska. Humification was determined by alkali extraction and colorimetry and records dated by radiocarbon and tephrochronology. Testate amoebae analysis was carried out across a major humification-inferred wet shift in three of the sites. The humification results show variability down the length of the cores but there is only limited agreement between records from different sites. Many general trends in the data appear to be out of phase and periods of proxy 'complacency' are shown. This study does not provide strong evidence for climatic forcing of humification in these sites. Methodological issues including possible problems with the age-depth models and the role of a peat-forming plant species signal in the humification data are discussed. The results support previous studies in suggesting the value of employing a multi-proxy, multi-site, and possibly multi-core approach in peat-based palaeoclimatology.

  2. Ecosystem carbon dioxide fluxes after disturbance in forests of North America

    Science.gov (United States)

    Amiro, B. D.; Barr, A. G.; Barr, J. G.; Black, T. A.; Bracho, R.; Brown, M.; Chen, J.; Clark, K. L.; Davis, K. J.; Desai, A. R.; Dore, S.; Engel, V.; Fuentes, J. D.; Goldstein, A. H.; Goulden, M. L.; Kolb, T. E.; Lavigne, M. B.; Law, B. E.; Margolis, H. A.; Martin, T.; McCaughey, J. H.; Misson, L.; Montes-Helu, M.; Noormets, A.; Randerson, J. T.; Starr, G.; Xiao, J.

    2010-12-01

    Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included stand-replacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon, Quebec, Saskatchewan, and Wisconsin) events, insect infestations (gypsy moth, forest tent caterpillar, and mountain pine beetle), Hurricane Wilma, and silvicultural thinning (Arizona, California, and New Brunswick). Net ecosystem production (NEP) showed a carbon loss from all ecosystems following a stand-replacing disturbance, becoming a carbon sink by 20 years for all ecosystems and by 10 years for most. Maximum carbon losses following disturbance (g C m-2y-1) ranged from 1270 in Florida to 200 in boreal ecosystems. Similarly, for forests less than 100 years old, maximum uptake (g C m-2y-1) was 1180 in Florida mangroves and 210 in boreal ecosystems. More temperate forests had intermediate fluxes. Boreal ecosystems were relatively time invariant after 20 years, whereas western ecosystems tended to increase in carbon gain over time. This was driven mostly by gross photosynthetic production (GPP) because total ecosystem respiration (ER) and heterotrophic respiration were relatively invariant with age. GPP/ER was as low as 0.2 immediately following stand-replacing disturbance reaching a constant value of 1.2 after 20 years. NEP following insect defoliations and silvicultural thinning showed lesser changes than stand-replacing events, with decreases in the year of disturbance followed by rapid recovery. NEP decreased in a mangrove ecosystem following Hurricane Wilma because of a decrease in GPP and an increase in ER.

  3. Optimizing Photosynthetic and Respiratory Parameters Based on the Seasonal Variation Pattern in Regional Net Ecosystem Productivity Obtained from Atmospheric Inversion

    Science.gov (United States)

    Chen, Z.; Chen, J.; Zheng, X.; Jiang, F.; Zhang, S.; Ju, W.; Yuan, W.; Mo, G.

    2014-12-01

    In this study, we explore the feasibility of optimizing ecosystem photosynthetic and respiratory parameters from the seasonal variation pattern of the net carbon flux. An optimization scheme is proposed to estimate two key parameters (Vcmax and Q10) by exploiting the seasonal variation in the net ecosystem carbon flux retrieved by an atmospheric inversion system. This scheme is implemented to estimate Vcmax and Q10 of the Boreal Ecosystem Productivity Simulator (BEPS) to improve its NEP simulation in the Boreal North America (BNA) region. Simultaneously, in-situ NEE observations at six eddy covariance sites are used to evaluate the NEE simulations. The results show that the performance of the optimized BEPS is superior to that of the BEPS with the default parameter values. These results have the implication on using atmospheric CO2 data for optimizing ecosystem parameters through atmospheric inversion or data assimilation techniques.

  4. Multitemporal L- and C-Band Synthetic Aperture Radar To Highlight Differences in Water Status Among Boreal Forest and Wetland Systems in the Yukon Flats, Interior Alaska

    Science.gov (United States)

    Balser, Andrew W.; Wylie, Bruce K.

    2010-01-01

    Tracking landscape-scale water status in high-latitude boreal systems is indispensible to understanding the fate of stored and sequestered carbon in a climate change scenario. Spaceborne synthetic aperture radar (SAR) imagery provides critical information for water and moisture status in Alaskan boreal environments at the landscape scale. When combined with results from optical sensor analyses, a complementary picture of vegetation, biomass, and water status emerges. Whereas L-band SAR showed better inherent capacity to map water status, C-band had much more temporal coverage in this study. Analysis through the use of L- and C-band SARs combined with Landsat Enhanced Thematic Mapper Plus (ETM+) enables landscape stratification by vegetation and by seasonal and interannual hydrology. Resultant classifications are highly relevant to biogeochemistry at the landscape scale. These results enhance our understanding of ecosystem processes relevant to carbon balance and may be scaled up to inform regional carbon flux estimates and better parameterize general circulation models (GCMs).

  5. The impact of boreal forest fire on climate warming.

    Science.gov (United States)

    Randerson, J T; Liu, H; Flanner, M G; Chambers, S D; Jin, Y; Hess, P G; Pfister, G; Mack, M C; Treseder, K K; Welp, L R; Chapin, F S; Harden, J W; Goulden, M L; Lyons, E; Neff, J C; Schuur, E A G; Zender, C S

    2006-11-17

    We report measurements and analysis of a boreal forest fire, integrating the effects of greenhouse gases, aerosols, black carbon deposition on snow and sea ice, and postfire changes in surface albedo. The net effect of all agents was to increase radiative forcing during the first year (34 +/- 31 Watts per square meter of burned area), but to decrease radiative forcing when averaged over an 80-year fire cycle (-2.3 +/- 2.2 Watts per square meter) because multidecadal increases in surface albedo had a larger impact than fire-emitted greenhouse gases. This result implies that future increases in boreal fire may not accelerate climate warming.

  6. Development of biogenic VOC emission inventories for the boreal forest

    Energy Technology Data Exchange (ETDEWEB)

    Tarvainen, V.

    2008-07-01

    The volatile organic compounds (VOCs) emitted by vegetation, especially forests, can affect local and regional atmospheric photochemistry through their reactions with atmospheric oxidants. Their reaction products may also participate in the formation and growth of new particles which affect the radiation balance of the atmosphere, and thus climate, by scattering and absorbing shortwave and longwave radiation and by modifying the radiative properties, amount and lifetime of clouds. Globally, anthropogenic VOC emissions are far surpassed by the biogenic ones, making biogenic emission inventories an integral element in the development of efficient air quality and climate strategies. The inventories are typically constructed based on landcover information, measured emissions of different plants or vegetation types, and empirical dependencies of the emissions on environmental variables such as temperature and light. This thesis is focused on the VOC emissions from the boreal forest, the largest terrestrial biome with characteristic vegetation patterns and strong seasonality. The isoprene, monoterpene and sesquiterpene emissions of the most prevalent boreal tree species in Finland, Scots pine, have been measured and their seasonal variation and dependence on temperature and light have been studied. The measured emission data and other available observations of the emissions of the principal boreal trees have been used in a biogenic emission model developed for the boreal forests in Finland. The model utilizes satellite landcover information, Finnish forest classification and hourly meteorological data to calculate isoprene, monoterpene, sesquiterpene and other VOC emissions over the growing season. The principal compounds emitted by Scots pine are DELTA3-carene and alpha-pinene in the south boreal zone and alpha- and beta-pinene in the north boreal zone. The monoterpene emissions are dependent on temperature and have a clear seasonal cycle with high emissions in spring

  7. Methanotrophy Induces Nitrogen Fixation in Boreal Mosses

    Science.gov (United States)

    Tiirola, M. A.

    2014-12-01

    Many methanotrophic bacterial groups fix nitrogen in laboratory conditions. Furthermore, nitrogen (N) is a limiting nutrient in many environments where methane concentrations are highest. Despite these facts, methane-induced N fixation has previously been overlooked, possibly due to methodological problems. To study the possible link between methanotrophy and diazotrophy in terrestrial and aquatic habitats, we measured the co-occurrence of these two processes in boreal forest, peatland and stream mosses using a stable isotope labeling approach (15 N2 and 13 CH4 double labeling) and sequencing of the nifH gene marker. N fixation associated with forest mosses was dependent on the annual N deposition, whereas methane stimulate N fixation neither in high (>3 kg N ha -1 yr -1) nor low deposition areas, which was in accordance with the nifH gene sequencing showing that forest mosses (Pleurozium schreberi and Hylocomium splendens ) carried mainly cyanobacterial N fixers. On the other extreme, in stream mosses (Fontinalis sp.) methane was actively oxidized throughout the year, whereas N fixation showed seasonal fluctuation. The co-occurrence of the two processes in single cell level was proven by co-localizing both N and methane-carbon fixation with the secondary ion mass spectrometry (SIMS) approach. Methanotrophy and diazotrophy was also studied in peatlands of different primary successional stages in the land-uplift coast of Bothnian Bay, in the Siikajoki chronosequence, where N accumulation rates in peat profiles indicate significant N fixation. Based on experimental evidence it was counted that methane-induced N fixation explained over one-third of the new N input in the younger peatland successional stages, where the highest N fixation rates and highest methane oxidation activities co-occurred in the water-submerged Sphagnum moss vegetation. The linkage between methanotrophic carbon cycling and N fixation may therefore constitute an important mechanism in the rapid

  8. Environmental factors regulating winter CO2 flux in snow-covered boreal forest soil, interior Alaska

    Science.gov (United States)

    Kim, Y.; Kodama, Y.

    2012-01-01

    Winter CO2 flux is an important element to assess when estimating the annual carbon budget on regional and global scales. However, winter observation frequency is limited due to the extreme cold weather in sub-Arctic and Arctic ecosystems. In this study, the continuous monitoring of winter CO2 flux in black spruce forest soil of interior Alaska was performed using NDIR CO2 sensors at 10, 20, and 30 cm above the soil surface during the snow-covered period (DOY 357 to 466) of 2006/2007. The atmospheric pressure was divided into four phases: >1000 hPa (HP: high pressure); 985emission represents 20 % of the annual CO2 emissions in this boreal black spruce forest soil. Atmospheric temperature, pressure, and soil temperature correlate at levels of 56, 25, and 31 % to winter CO2 flux, respectively, during the snow-covered period of 2006/2007, when snow depth experienced one of its lowest totals of the past 80 years. Atmospheric temperature and soil temperature at 5 cm depth, modulated by atmospheric pressure, were found to be significant factors in determining winter CO2 emission and fluctuation in snowpack. Regional/global process-based carbon cycle models should be reassessed to account for the effect of winter CO2 emissions, regulated by temperature and soil latent-heat flux, in the snow-covered soils of Arctic and sub-Arctic terrestrial ecosystems of the Northern Hemisphere.

  9. Restoring the Nitrogen Cycle in the Boreal Forest - a Case Study from Northern Alberta

    Science.gov (United States)

    Masse, Jacynthe; Grayston, Sue; Prescott, Cindy; Quideau, Sylvie

    2014-05-01

    between nitrogen cycling processes in the different vegetation treatments and in the naturally disturbed sites were found. The reasons for these variances will be discussed. The oil sands will be Canada's environmental legacy for the next several hundred years and recreating functional soils is fundamental to our ability to restore boreal ecosystems after disturbance.

  10. Investigation and Quantification of Water Track Networks in Boreal Regions Using Remote Sensing and Geophysical Data

    Science.gov (United States)

    Mendbayar, U.; Misra, D.; Gupta, T.; Ghosh, T.

    2015-12-01

    Water tracks are the most prominent drainage pathways that route water through the soil over permafrost in the polar environment and thus play a major role in hydrology, geomorphology, and geochemistry of the polar ecosystem. Existing literature on water tracks is limited and is largely confined to tundra areas devoid of vegetation. The objective of this study is to initiate the investigation of water tracks in thickly vegetated boreal regions, many of which contain predominant engineered infrastructures. The ancillary objectives include the development of methods for mapping the distribution of water tracks in boreal regions and a preliminary analysis of the geotechnical impacts of water track interception on infrastructures. The study area is Goldstream Road in Fairbanks, Alaska. This road experiences high amounts of damage, possibly due to interception of prominent water tracks. To investigate the road damage, the Alaska Department of Transportation has collected geophysical data in 2012. We plan to create a water track distribution map around the Goldstream Road using high-spatial-and-spectral-resolution remote sensing imagery and correlate it with the geophysical data from 2012. We have collected ground data from two water tracks: one in a residence in Fairbanks and the other besides the Goldstream Road. The two tracks vary greatly in size and features. Both water tracks revealed different yet quite promising characteristics. These findings will be used to extract other water tracks from remotely sensed images of the Goldstream Road area. So far, a 2010 SPOT 5 image (2.5m x 2.5 m), an aerial orthophoto (14 cm x 14 cm) and a DEM (57 cm x 57 cm) from September 2014 have been acquired. Normalized Difference Vegetation Index (NDVI) processing was performed on the 2010 SPOT 5 image. A detailed water track database was created and water tracks are being manually digitized from the available imagery and Web Mapping Services (WMS). As a test, using FLIR, handheld

  11. Seasonal Variability in Boreal Wildfire Activity Associated with Landscape Patterns of Burned Area

    Science.gov (United States)

    Barrett, K. M.; Kasischke, E. S.

    2012-12-01

    Wildfire is the most prominent disturbance in the boreal forest, effecting changes in stand age and vegetation composition often over thousands of square kilometers. The effect of wildfire on ecosystem structure and function depends heavily on the seasonality of the burn, and periods of seasonally high fire activity are highly sporadic. The majority of area in Alaska that burns in a fire season does so during relatively short periods of high fire activity. These periods, which can be determined from active fire detections or fire management agency data records, are caused by elevated air temperatures and low precipitation which decrease fuel moisture and encourage the spread of fire. While fire fronts dominate during periods of low fire activity, more active periods have a higher proportion of residual burning which remains after a front has passed through. Residual burning is likely responsible for the extensive combustion of surface organic materials in the boreal forest, which can lead to post-fire changes in dominant vegetation type. Seasonal variations in fire activity are therefore an important factor in the mosaic of severity conditions across large burned areas and shifts in land cover over successional time scales. The purpose of this study is to characterize the temporal and spatial variability in periods of seasonal high fire activity that influence patterns of burned area. In large burns, unburned areas within a fire scar may serve as an important seed stock during post-fire recruitment. These areas may also feedback to future fire regimes through the preservation of more fire-resistant vegetation in unburned "islands".

  12. Moss species benefits from breakdown of cyclic rodent dynamics in boreal forests.

    Science.gov (United States)

    Rydgren, Knut; Økland, Rune H; Picó, F Xavier; de Kroon, Hans

    2007-09-01

    Bryophytes have increased in abundance in northern regions, and climate changes have been proposed to account for this change. However, changes in the population dynamics of microtine rodents may also contribute to changes in bryophyte abundance. New evidence indicates a tendency for microtine rodent population oscillations to change from periodicity of 3-5 years to become irregular or acyclic. The impact on ecosystem functioning is potentially great. We study the impact of variation in microtine rodent population characteristics, such as cycle length and amplitude, on the population dynamics of the boreal, clonal moss Hylocomium splendens. We use experimental and observational demographic data to construct 127 scenarios representing all combinations of disturbance type (gap formation and/or clipping), period (cyclic with 4, 6, 12, or 24 years between rodent peaks; or acyclic with constant or stochastically varying annual disturbance severity) and disturbance severity (fraction of individuals affected by disturbance in each year relative to the maximum disturbance carried out in the field experiment; seven levels). Population data collected in the field during 13 years were used as a baseline scenario. By subjecting all scenarios to stochastic matrix modeling, we demonstrate considerable impact of microtine rodent on the population dynamics of H. splendens, most notably when rodent populations fluctuate with short periods and high peak disturbance severities. Under the same average disturbance severity, H. splendens population growth rates are highest in acyclic scenarios and are progressively reduced with increasing peak disturbance severities (i.e., with increasing period). Stochastic elasticity analyses show that in less variable environments mature segment survival contributes more to the population growth rate, while in more variable environments the regeneration pathway (branching of older parts of the plant) plays a stronger role, inevitably leading to lower

  13. Mechanisms for success after long-term nutrient enrichment in a boreal forest understory.

    Directory of Open Access Journals (Sweden)

    Tess Nahanni Grainger

    Full Text Available Global levels of reactive nitrogen are predicted to rise in the coming decades as a result of increased deposition from the burning of fossil fuels and the large-scale conversion of nitrogen into a useable form for agriculture. Many plant communities respond strongly to increases in soil nitrogen, particularly in northern ecosystems where nitrogen levels are naturally very low. An experiment in northern Canada that was initiated in 1990 has been investigating the effects of long-term nutrient enrichment (fertilizer added annually on a boreal forest understory community. We used this experiment to investigate why some species increase in abundance under nutrient enrichment whereas others decline. We focused on four species that differed in their responses to fertilization: Mertensia paniculata and Epilobium angustifolium increased in abundance, Achillea millefolium remained relatively constant and Festuca altaica declined. We hypothesized that the two species that were successful in the new high-nutrient, light-limited environment would be taller, have higher specific leaf area, change phenology by growing earlier in the season and be more morphologically plastic than their less successful counterparts. We compared plant height, specific leaf area, growth spurt date and allocation to leaves in plants grown in control and fertilized plots. We demonstrated that each of the two species that came to dominate fertilized plots has a different combination of traits and responses that likely gave them a competitive advantage; M. paniculata has the highest specific leaf area of the four species whereas E. angustifolium is tallest and exhibits morphological plasticity when fertilized by increasing biomass allocation to leaves. These results indicate that rather than one strategy determining success when nutrients become available, a variety of traits and responses may contribute to a species' ability to persist in a nutrient-enriched boreal forest

  14. The influence of daily meteorology on boreal fire emissions and regional trace gas variability

    Science.gov (United States)

    Wiggins, E. B.; Veraverbeke, S.; Henderson, J. M.; Karion, A.; Miller, J. B.; Lindaas, J.; Commane, R.; Sweeney, C.; Luus, K. A.; Tosca, M. G.; Dinardo, S. J.; Wofsy, S.; Miller, C. E.; Randerson, J. T.

    2016-11-01

    Relationships between boreal wildfire emissions and day-to-day variations in meteorological variables are complex and have important implications for the sensitivity of high-latitude ecosystems to climate change. We examined the influence of environmental conditions on boreal fire emissions and fire contributions to regional trace gas variability in interior Alaska during the summer of 2013 using two types of analysis. First, we quantified the degree to which meteorological and fire weather indices explained regional variability in fire activity using four different products, including active fires, fire radiative power, burned area, and carbon emissions. Second, we combined daily emissions from the Alaskan Fire Emissions Database (AKFED) with the coupled Polar Weather Research and Forecasting/Stochastic Time-Inverted Lagrangian Transport model to estimate fire contributions to trace gas concentration measurements at the Carbon in Arctic Reservoirs Vulnerability Experiment-NOAA Global Monitoring Division (CRV) tower in interior Alaska. Tower observations during two high fire periods were used to estimate CO and CH4 emission factors. We found that vapor pressure deficit and temperature had a level of performance similar to more complex fire weather indices. Emission factors derived from CRV tower measurements were 134 ± 25 g CO per kg of combusted biomass and 7.74 ± 1.06 g CH4 per kg of combusted biomass. Predicted daily CO mole fractions from AKFED emissions were moderately correlated with CRV observations (r = 0.68) and had a high bias. The modeling system developed here allows for attribution of emission factors to individual fires and has the potential to improve our understanding of regional CO, CH4, and CO2 budgets.

  15. Mechanisms for success after long-term nutrient enrichment in a boreal forest understory.

    Science.gov (United States)

    Grainger, Tess Nahanni; Turkington, Roy

    2013-01-01

    Global levels of reactive nitrogen are predicted to rise in the coming decades as a result of increased deposition from the burning of fossil fuels and the large-scale conversion of nitrogen into a useable form for agriculture. Many plant communities respond strongly to increases in soil nitrogen, particularly in northern ecosystems where nitrogen levels are naturally very low. An experiment in northern Canada that was initiated in 1990 has been investigating the effects of long-term nutrient enrichment (fertilizer added annually) on a boreal forest understory community. We used this experiment to investigate why some species increase in abundance under nutrient enrichment whereas others decline. We focused on four species that differed in their responses to fertilization: Mertensia paniculata and Epilobium angustifolium increased in abundance, Achillea millefolium remained relatively constant and Festuca altaica declined. We hypothesized that the two species that were successful in the new high-nutrient, light-limited environment would be taller, have higher specific leaf area, change phenology by growing earlier in the season and be more morphologically plastic than their less successful counterparts. We compared plant height, specific leaf area, growth spurt date and allocation to leaves in plants grown in control and fertilized plots. We demonstrated that each of the two species that came to dominate fertilized plots has a different combination of traits and responses that likely gave them a competitive advantage; M. paniculata has the highest specific leaf area of the four species whereas E. angustifolium is tallest and exhibits morphological plasticity when fertilized by increasing biomass allocation to leaves. These results indicate that rather than one strategy determining success when nutrients become available, a variety of traits and responses may contribute to a species' ability to persist in a nutrient-enriched boreal forest understory.

  16. Resilience of Alaska's Boreal Forest to Climatic Change

    Science.gov (United States)

    Chapin, F. S., III; McGuire, A. D.; Ruess, R. W.; Hollingsworth, T. N.; Mack, M. C.; Johnstone, J. F.; Kasischke, E. S.; Euskirchen, E. S.; Jones, J. B.; Jorgenson, M. T.; Kielland, K.; Kofinas, G. P.; Turetsky, M. R.; Yarie, J.; Lloyd, A. H.; Taylor, D. L.

    2010-01-01

    This paper assesses the resilience of Alaska s boreal forest system to rapid climatic change. Recent warming is associated with reduced growth of dominant tree species, plant disease and insect outbreaks, warming and thawing of permafrost, drying of lakes, increased wildfire extent, increased postfire recruitment of deciduous trees, and reduced safety of hunters traveling on river ice. These changes have modified key structural features, feedbacks, and interactions in the boreal forest, including reduced effects of upland permafrost on regional hydrology, expansion of boreal forest into tundra, and amplification of climate warming because of reduced albedo (shorter winter season) and carbon release from wildfires. Other temperature-sensitive processes for which no trends have been detected include composition of plant and microbial communities, long-term landscape-scale change in carbon stocks, stream discharge, mammalian population dynamics, and river access and subsistence opportunities for rural indigenous communities. Projections of continued warming suggest that Alaska s boreal forest will undergo significant functional and structural changes within the next few decades that are unprecedented in the last 6000 years. The impact of these social ecological changes will depend in part on the extent of landscape reorganization between uplands and lowlands and on policies regulating subsistence opportunities for rural communities.

  17. Moss-nitrogen input to boreal forest soils

    DEFF Research Database (Denmark)

    Rousk, Kathrin; Jones, Davey; DeLuca, Thomas

    2014-01-01

    Cyanobacteria living epiphytically on mosses in pristine, unpolluted areas fix substantial amounts of atmospheric nitrogen (N) and therefore represent a primary source of N in N-limited boreal forests. However, the fate of this N is unclear, in particular, how the fixed N2 enters the soil...

  18. DOC Affinity as a Key Parameter for Explaining the Transport Patterns of U, Th and Other Elements in the Boreal Landscape

    Science.gov (United States)

    Lidman, F.; Köhler, S.; Björkvald, L.; Mörth, M.; Laudon, H.

    2009-04-01

    The 68 km2 Krycklan Catchment located in Northern Sweden has been studied intensely for more than 30 years. This has resulted in a good understanding of among all hydrological and biogeochemical processes. Currently, 18 sites within the catchment are regularly sampled and analyzed for major elements and other hydrochemical parameters. 10 of these sites have also been monitored for a wide range of trace elements, among all uranium and thorium, during a two-year period. Hence, there is a comprehensive dataset describing the export of a wide range of elements from these sub-catchments. For uranium and thorium large differences in stream water concentrations and, consequently, annual export from the different sub-catchments were observed. In order to explain these differences air-borne gamma spectrometry was used to measure uranium and thorium concentrations in the soils over the entire catchment. It could be expected that high concentrations in the soils of the sub-catchment would lead to a high export, but it turned out that the correlation was not particularly strong. Instead it was found that the export was strongly correlated to the wetland/lake coverage within each sub-catchment for both uranium and thorium. High wetland/lake coverage would lead to a low export, while high forest coverage would lead to a high export. In the case of uranium, for instance, the data show that a mire that covers 50% of a catchment will reduce the uranium export by approximately 90% as compared to the export from a completely forested catchment. This indicates that uranium is being accumulated in mires. If more elements are included in the analysis and the export of each element is compared to the landscape characteristics, some elements, e.g. cesium and potassium, turn out to be completely unaffected by the forest or mire coverage, while other elements such as lanthanum and copper behave similarly to uranium and thorium. Thermodynamic modeling using PHREEQC and Visual MINTEQ has been

  19. Forest harvest contribution to Boreal freshwater methyl mercury load

    Science.gov (United States)

    Kronberg, Rose-Marie; Drott, Andreas; Jiskra, Martin; Wiederhold, Jan G.; Björn, Erik; Skyllberg, Ulf

    2016-06-01

    Effects of Boreal forest harvest on mercury (Hg) and methyl mercury (MeHg) soil pools and export by stream runoff were quantified by comparing 10 reference watersheds (REFs) covered by >80 year old Norway spruce (Picea abies Karst.) forests with 10 similar watersheds subjected to clear-cutting (CCs). While total Hg soil storage did not change, MeHg pools increased seven times (p = 0.006) in the organic topsoil 2 years after clear-cutting. In undulating terrain, situated above the postglacial marine limit (ML) of the ancient Baltic Sea, the mass ratio between flux-weighted MeHg and dissolved organic carbon (MeHg/DOC) in stream runoff increased 1.8 times (p forest harvest. When recalculated to 100% clear-cutting of the watershed, the annual MeHg stream export increased 3.8 times (p = 0.047). Below the ML, where the terrain was flatter, neither the MeHg/DOC ratio nor the annual export of MeHg differed between REFs and CCs, likely because of the larger contribution of MeHg exported from peaty soils and small wetlands. The most robust measure, MeHg/DOC, was used to calculate MeHg loadings to Boreal headwaters. If the forest harvest effect lasts 10 years, clear-cutting increases MeHg runoff by 12-20% in Sweden and 2% in the Boreal zone as a whole. In Sweden, having intensely managed forests, 37% and 56% of MeHg are exported from peatlands and forest soils, respectively, and forest clear-cutting is adding another 6.6%. In the Boreal zone as a whole peatlands and forests soils contribute with 53% and 46%, respectively, and clear-cutting is estimated to add another 1.0%. An expected rapid increase in Boreal forest harvest and disturbance urge for inclusion of land use effects in mercury biogeochemical cycling models at different scales.

  20. Observing terrestrial ecosystems and the carbon cycle from space

    Energy Technology Data Exchange (ETDEWEB)

    Schimel, David [Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91101 USA; Pavlick, Ryan [Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91101 USA; Fisher, Joshua B. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91101 USA; Asner, Gregory P. [Department of Global Ecology, Carnegie Institution for Science, 260 Panama St. Stanford CA 94305 USA; Saatchi, Sassan [Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91101 USA; Townsend, Philip [University of Wisconsin-Madison, Madison WI 53706 USA; Miller, Charles [Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91101 USA; Frankenberg, Christian [Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA 91101 USA; Hibbard, Kathy [Pacific Northwest National Laboratory, PO Box 999 MSIN: K9-34 Richland WA 99352 USA; Cox, Peter [College of Engineering, Mathematics and Physical Sciences, University of Exeter, North Park Road Streatham Campus Harrison Building Exeter EX4 4QF UK

    2015-02-06

    Modeled terrestrial ecosystem and carbon cycle feedbacks contribute substantial uncertainty to projections of future climate. The limitations of current observing networks contribute to this uncertainty. Here we present a current climatology of global model predictions and observations for photosynthesis, biomass, plant diversity and plant functional diversity. Carbon cycle tipping points occur in terrestrial regions where fluxes or stocks are largest, and where biological variability is highest, the tropics and Arctic/Boreal zones. Global observations are predominately in the mid-latitudes and are sparse in high and low latitude ecosystems. Observing and forecasting ecosystem change requires sustained observations of sufficient density in time and space in critical regions. Using data and theory available now, we can develop a strategy to detect and forecast terrestrial carbon cycle-climate interactions, by combining in situ and remote techniques.

  1. Carbon balance of an old hemi-boreal pine forest in Southern Estonia determined by different methods

    Science.gov (United States)

    Soosaar, Kaido; Repp, Kalev; Lõhmus, Krista; Uri, Veiko; Rannik, Kaire; Krasnova, Alisa; Ostonen, Ivika; Kukumägi, Mai; Maddison, Martin; Mander, Ülo

    2016-04-01

    The Soontaga Forest Station is located in hemi-boreal 200-years old pine forest (South Estonia; 58o01'N 26o04'E) with a second layer of spruce. The station has the instrumentation to assess the exchange of carbon dioxide (net ecosystem exchange, NEE), soil respiration, tree biomass (above and below ground biomass) and different environmental and meteorological parameters. In this study we quantified carbon balance by analyzing eddy-covariance CO2 flux data (carbon exchange) vs chamber-based measurements (ecosystem respiration) and CO2assimilation (soil and biomass). The annual NEE in this mature coniferous forest was -2.3 t C ha yr-1, showing a clear diurnal and seasonal trend. During the daytime in summer the forest sequestered CO2, while during the night and late night CO2 emitted from the ecosystem to the atmosphere. Within the growing period, the sequestration of CO2 by plants was greater than soil respiration. Thus, the ecosystem sequestered carbon. Most of the carbon is bound in tree biomass (above and below ground biomass) but as well into soil, while the sequestration in soil increases with stand age. In addition, the biomass of understory, especially belowground litter, is playing essential part in carbon input. A modelling approach of long-term C budget in the Soontaga pine forest is presented.

  2. Who is the new sheriff in town regulating boreal forest growth?

    Science.gov (United States)

    Park Williams, A.; Xu, Chonggang; McDowell, Nate G.

    2011-12-01

    G P, Alix C, Barber V A, Winslow S E, Sousa E E, Heiser P, Herriges J D and Goetz S J 2011 Changes in forest productivity across Alaska consistent with biome shift Ecol. Lett. 14 373-9 Berner L T, Beck P S A, Bunn A G, Lloyd A H and Goetz S J 2011 High-latitude tree growth and satellite vegetation indices: correlations and trends in Russia and Canada (1982-2008) J. Geophys. Res. 116 G01015 Bunn A G and Goetz S J 2006 Trends in satellite-observed circumpolar photosynthetic activity from 1982 to 2003: the influence of seasonality, cover type, and vegetation density Earth Interact. 10 1-19 D'Arrigo R, Jacoby G, Buckley B, Sakulich J, Frank D, Wilson R, Curtis A and Anchukaitis K 2009 Tree growth and inferred temperature variability at the North American Arctic treeline Glob. Planet. Change 65 71-82 D'Arrigo R, Wilson R, Liepert B, Cherubini P 2008 On the 'divergence problem' in northern forests: a review of the tree-ring evidence and possible causes Glob. Planet. Change 60 289-305 Davi N K, Jacoby G C and Wiles G C 2003 Boreal temperature variability inferred from maximum latewood density and tree-ring width data, Wrangell Mountain region, Alaska Quatern. Res. 60 252-62 Flexas J, Bota J, Loreto F, Cornic G and Sharkey T 2004 Diffusive and metabolic limitations to photosynthesis under drought and salinity in C3 plants Plant Biol. 6 269-79 Goetz S J, Bunn A G, Fiske G J and Houghton R 2005 Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance Proc. Natl Acad. Sci. USA 102 13521-5 Goetz S J, Kimball J S, Mack M C and Kasischke E S 2011 Scoping completed for an experiment to assess vulnerability of Arctic and boreal ecosystems EOS Trans. Am. Geophys. Union 92 150-1 McDowell N G 2011 Mechanisms linking drought, hydraulics, carbon metabolism, and vegetation mortality Plant Physiol. 155 1051-9 McGuire A D, Ruess R W, Lloyd A, Yarie J, Clein J S and Juday G P 2010 Vulnerability of white spruce tree growth in interior

  3. Simple proxies for estimating the concentrations of monoterpenes and their oxidation products at a boreal forest site

    Science.gov (United States)

    Kontkanen, Jenni; Paasonen, Pauli; Aalto, Juho; Bäck, Jaana; Rantala, Pekka; Petäjä, Tuukka; Kulmala, Markku

    2016-10-01

    The oxidation products of monoterpenes likely have a crucial role in the formation and growth of aerosol particles in boreal forests. However, the continuous measurements of monoterpene concentrations are usually not available on decadal timescales, and the direct measurements of the concentrations of monoterpene oxidation product have so far been scarce. In this study we developed proxies for the concentrations of monoterpenes and their oxidation products at a boreal forest site in Hyytiälä, southern Finland. For deriving the proxies we used the monoterpene concentration measured with a proton transfer reaction mass spectrometer (PTR-MS) during 2006-2013. Our proxies for the monoterpene concentration take into account the temperature-controlled emissions from the forest ecosystem, the dilution caused by the mixing within the boundary layer and different oxidation processes. All the versions of our proxies captured the seasonal variation of the monoterpene concentration, the typical proxy-to-measurements ratios being between 0.8 and 1.3 in summer and between 0.6 and 2.6 in winter. In addition, the proxies were able to describe the diurnal variation of the monoterpene concentration rather well, especially in summer months. By utilizing one of the proxies, we calculated the concentration of oxidation products of monoterpenes by considering their production in the oxidation and their loss due to condensation on aerosol particles. The concentration of oxidation products was found to have a clear seasonal cycle, with a maximum in summer and a minimum in winter. The concentration of oxidation products was lowest in the morning or around noon and highest in the evening. In the future, our proxies for the monoterpene concentration and their oxidation products can be used, for example, in the analysis of new particle formation and growth in boreal environments.

  4. Singular and interactive effects of blowdown, salvage logging, and wildfire in sub-boreal pine systems

    Science.gov (United States)

    D'Amato, A.W.; Fraver, S.; Palik, B.J.; Bradford, J.B.; Patty, L.

    2011-01-01

    The role of disturbance in structuring vegetation is widely recognized; however, we are only beginning to understand the effects of multiple interacting disturbances on ecosystem recovery and development. Of particular interest is the impact of post-disturbance management interventions, particularly in light of the global controversy surrounding the effects of salvage logging on forest ecosystem recovery. Studies of salvage logging impacts have focused on the effects of post-disturbance salvage logging within the context of a single natural disturbance event. There have been no formal evaluations of how these effects may differ when followed in short sequence by a second, high severity natural disturbance. To evaluate the impact of this management practice within the context of multiple disturbances, we examined the structural and woody plant community responses of sub-boreal Pinus banksiana systems to a rapid sequence of disturbances. Specifically, we compared responses to Blowdown (B), Fire (F), Blowdown-Fire, and Blowdown-Salvage-Fire (BSF) and compared these to undisturbed control (C) stands. Comparisons between BF and BSF indicated that the primary effect of salvage logging was a decrease in the abundance of structural legacies, such as downed woody debris and snags. Both of these compound disturbance sequences (BF and BSF), resulted in similar woody plant communities, largely dominated by Populus tremuloides; however, there was greater homogeneity in community composition in salvage logged areas. Areas experiencing solely fire (F stands) were dominated by P. banksiana regeneration, and blowdown areas (B stands) were largely characterized by regeneration from shade tolerant conifer species. Our results suggest that salvage logging impacts on woody plant communities are diminished when followed by a second high severity disturbance; however, impacts on structural legacies persist. Provisions for the retention of snags, downed logs, and surviving trees as part

  5. New insights on the link between phenology and productivity of temperate and boreal broadleaf deciduous forests across the globe

    Science.gov (United States)

    Sonnentag, O.; Hufkens, K.; Keenan, T. F.; Friedl, M. A.; Richardson, A. D.

    2011-12-01

    Shifts in the timing of key phenological phases in plants have been indentified as useful indicators to track the impact of ongoing climate change. Phenological responses themselves provide important feedbacks to the climate system as they exert control over most above- and belowground ecosystem processes and productivity. Recent advances in near-surface remote sensing enable automated and consistent observation of vegetation status at spatial and temporal scales suitable for integration with eddy covariance measurements. This allows us to gain phenological understanding of biosphere-atmosphere energy, water vapor and trace gas exchanges and thus productivity. Several previous studies have investigated the link between key phenological phases in temperate and boreal forests and their productivity across sites and years. Most of these studies focused on shifts in the timing of spring phenological events such as budburst. Few studies, however, have investigated the importance of the rates of changes across key phenological phases such as leaf development and senescence in spring and autumn, respectively, as explanatory variables of observed interannual and across-site variability in forest productivity. To shed light on this question we first optimized and evaluated a popular bioclimatic index (the growing season index of Jolly et al., 2005) that integrates known controls on temperate and boreal forest canopy development (i.e., air temperature, photoperiod, soil water balance) with multiple years of digital repeat photography at different sites from the PhenoCam network. Next, using meteorological and eddy covariance measurements from 24 temperate and boreal broadleaf deciduous forest sites across the globe (113 site years) as provided by the FLUXNET 'La Thuile' data set, we characterized continuous canopy development with the optimized bioclimatic index and derived spring and autumn phenological dates and rates and annual integrals of net ecosystem productivity (NEP

  6. Organic Carbon Dynamics beyond the Perspective of Monitoring: Impact of Historical Landscape Utilization on the Past Lake-Water Carbon Trajectory in Central Boreal Sweden

    Science.gov (United States)

    Meyer-Jacob, C.; Tolu, J.; Bigler, C.; Bindler, R.

    2014-12-01

    To date, the key drivers behind the recent observed increase in organic carbon (OC) concentrations in surface waters are still controversial. The lack of long-term monitoring data - over centuries and millennia - leaves us with an ambiguous understanding of the past trajectory of OC concentrations in surface waters, and inhibits a better mechanistic understanding of past and a reliable prediction of future changes in OC levels.By using a paleolimnological approach, we reconstructed past lake-water total organic carbon (TOC) concentrations in lakes across the boreal landscape of central Sweden. Reconstructions are based on a transfer function between visible near-infrared spectra of surface sediments and the corresponding TOC concentration in the water column. Potential drivers behind changes in TOC were determined by a multi-proxy analysis of one of the studied lake sediment records including organic and inorganic geochemistry as well as biological proxies (pollen, diatoms).Our results show a significant decrease in lake-water TOC beginning already ~550 years ago. This decline continued until the mid-20th century when TOC concentrations started to increase again. These dynamics in TOC coincide with changes in proxies indicating catchment disturbance by human activities. The chronology of these changes corresponds to the expansion and decline of a landscape-wide system of summer forest grazing and farming in central Sweden from the 15th century to the turn of the 20th century. Frequent grazing and exploitation of forests and mires reduce aboveground vegetation and physically disturb soils. This further affects the carbon cycling by enhancing carbon turnover, reducing the thickness of organic soils and consequently altering the transport of OC from the catchment to lakes.Our findings suggest that recent changes in lake-water TOC in Sweden are strongly associated with historical patterns in land use and not only on-going changes in climate or sulfur deposition.

  7. Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction

    Science.gov (United States)

    Zatoń, Michał; Niedźwiedzki, Grzegorz; Blom, Henning; Kear, Benjamin P.

    2016-11-01

    The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic. Its aftermath was characterized by harsh marine conditions incorporating volcanically induced oceanic warming, widespread anoxia and acidification. Bio-productivity accordingly experienced marked fluctuations. In particular, low palaeolatitude hard substrate communities from shallow seas fringing Western Pangaea and the Tethyan Realm were extremely impoverished, being dominated by monogeneric colonies of filter-feeding microconchid tubeworms. Here we present the first equivalent field data for Boreal hard substrate assemblages from the earliest Triassic (Induan) of East Greenland. This region bordered a discrete bio-realm situated at mid-high palaeolatitude (>30°N). Nevertheless, hard substrate biotas were compositionally identical to those from elsewhere, with microconchids encrusting Claraia bivalves and algal buildups on the sea floor. Biostratigraphical correlation further shows that Boreal microconchids underwent progressive tube modification and unique taxic diversification concordant with changing habitats over time. We interpret this as a post-extinction recovery and adaptive radiation sequence that mirrored coeval subequatorial faunas, and thus confirms hard substrate ecosystem depletion as a hallmark of the earliest Triassic interval globally.

  8. Impact of forest harvesting on water quality and fluorescence characteristics of dissolved organic matter in Eastern Canadian Boreal Shield lakes

    Directory of Open Access Journals (Sweden)

    P. Glaz

    2015-06-01

    Full Text Available Forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. Water quality and fluorescence characteristics of dissolved organic matter (DOM were measured over a three-year period in eight Eastern Boreal Shield lakes: four lakes were studied before, one and two years after forest harvesting (perturbed lakes and compared with four undisturbed reference lakes (unperturbed lakes sampled at the same time. ANOVAs showed a significant increase in total phosphorus (TP in perturbed lakes when the three sampling dates were considered and in DOC concentrations when considering one year before and one year after the perturbation only. At one year post-clear cutting DOC concentrations were about 15 % greater in the perturbed lakes at ~15 mg C L−1 compared to 12.5 mg C L−1 in the unperturbed lakes. In contrast, absorbance and fluorescence measurements showed that all metrics remained within narrow ranges compared to the range observed in natural waters, indicating that forest harvesting did not affect the nature of DOM characterised with spectroscopic techniques. Multivariate statistical analysis showed lakes to be significantly different one year after the perturbation. These results confirm an impact of forestry activities one year after the perturbation. However, this effect seems to be mitigated two years after, indicating that the system shows high resilience and may be able to return to its original condition.

  9. Nonlinear response of canopy developmental rate to temperature in temperate and boreal forest in the Northern Hemisphere

    Science.gov (United States)

    Park, H.; Ho, C. H.; Jeong, S. J.

    2015-12-01

    Understanding the changes in vegetation annual cycle is crucial for improving our knowledge about various interactions between the terrestrial ecosystem and climate. However, our understanding about the vegetation seasonality is mostly confined to some phenological timings such as spring emergence and fall senescence. This study assessed large-scale variations in the vegetation green-up rate (VGrate), which indicates the rate of canopy development from winter dormancy to summer maturity, and its relationship over Northern Hemisphere temperate and boreal forests for 1982-2011. VGrate and local temperature changes show a positive correlation over the region of interest, and it indicates that a temperature increase during green-up period leads to faster canopy development. The responses of VGrate tend to be more sensitive to positive temperature anomalies than negative anomalies despite same magnitude of the temperature changes. These nonlinear responsiveness of VGrate to local temperature change is clearly observed in deciduous broadleaf forests over Eurasia compared to woodlands over North America. These results suggest that anomalous warming in green-up period would make canopy developments faster over wide temperate and boreal forest areas.

  10. Spatially explicit fire-climate history of the boreal forest-tundra (Eastern Canada) over the last 2000 years.

    Science.gov (United States)

    Payette, Serge; Filion, Louise; Delwaide, Ann

    2008-07-12

    Across the boreal forest, fire is the main disturbance factor and driver of ecosystem changes. In this study, we reconstructed a long-term, spatially explicit fire history of a forest-tundra region in northeastern Canada. We hypothesized that current occupation of similar topographic and edaphic sites by tundra and forest was the consequence of cumulative regression with time of forest cover due to compounding fire and climate disturbances. All fires were mapped and dated per 100 year intervals over the last 2,000 years using several fire dating techniques. Past fire occurrences and post-fire regeneration at the northern forest limit indicate 70% reduction of forest cover since 1800 yr BP and nearly complete cessation of forest regeneration since 900 yr BP. Regression of forest cover was particularly important between 1500s-1700s and possibly since 900 yr BP. Although fire frequency was very low over the last 100 years, each fire event was followed by drastic removal of spruce cover. Contrary to widespread belief of northward boreal forest expansion due to recent warming, lack of post-fire recovery during the last centuries, in comparison with active tree regeneration more than 1,000 years ago, indicates that the current climate does not favour such expansion.

  11. Thermokarst rates intensify due to climate change and forest fragmentation in an Alaskan boreal forest lowland

    Science.gov (United States)

    Lara, M.; Genet, Helene; McGuire, Anthony; Euskirchen, Eugénie S.; Zhang, Yujin; Brown, Dana R. N.; Jorgenson, M.T.; Romanovsky, V.; Breen, Amy L.; Bolton, W.R.

    2016-01-01

    Lowland boreal forest ecosystems in Alaska are dominated by wetlands comprised of a complex mosaic of fens, collapse-scar bogs, low shrub/scrub, and forests growing on elevated ice-rich permafrost soils. Thermokarst has affected the lowlands of the Tanana Flats in central Alaska for centuries, as thawing permafrost collapses forests that transition to wetlands. Located within the discontinuous permafrost zone, this region has significantly warmed over the past half-century, and much of these carbon-rich permafrost soils are now within ~0.5 °C of thawing. Increased permafrost thaw in lowland boreal forests in response to warming may have consequences for the climate system. This study evaluates the trajectories and potential drivers of 60 years of forest change in a landscape subjected to permafrost thaw in unburned dominant forest types (paper birch and black spruce) associated with location on elevated permafrost plateau and across multiple time periods (1949, 1978, 1986, 1998, and 2009) using historical and contemporary aerial and satellite images for change detection. We developed (i) a deterministic statistical model to evaluate the potential climatic controls on forest change using gradient boosting and regression tree analysis, and (ii) a 30 × 30 m land cover map of the Tanana Flats to estimate the potential landscape-level losses of forest area due to thermokarst from 1949 to 2009. Over the 60-year period, we observed a nonlinear loss of birch forests and a relatively continuous gain of spruce forest associated with thermokarst and forest succession, while gradient boosting/regression tree models identify precipitation and forest fragmentation as the primary factors controlling birch and spruce forest change, respectively. Between 1950 and 2009, landscape-level analysis estimates a transition of ~15 km² or ~7% of birch forests to wetlands, where the greatest change followed warm periods. This work highlights that the vulnerability and resilience of

  12. The role of sustained water table drawdown and wildfire on C emissions in boreal peatlands

    Science.gov (United States)

    Kotowska, A.; Turetsky, M. R.; Benscoter, B.

    2011-12-01

    Northern peatlands store up to 370 Pg C, or ~80% of boreal soil carbon (C). In general, peat accumulates where water table (WT) levels at or near the soil surface lead to high primary productivity and low rates of decomposition. However, increased evapotranspiration under warmer, drier conditions predicted for boreal peatlands under future climate change are expected to decrease seasonal WT levels and increase the potential for deep peat fires. The effects of long-term changes in hydrology on northern peatland vegetation and C cycling are not well understood, nor are the effects of wildfire on interactions between C cycling and peatland hydrology. The objective of this study was to examine the net effects of fire and long-term water table drawdown on CO2 and CH4 fluxes. We utilized a rich fen impacted by road construction in the early 1990's and a bog that experienced a severe fire 4 years prior to study initiation to examine drought and fire disturbances, respectively. We found that 20 years of sustained WT drawdown had no effect on understory net ecosystem exchange (NEE) of CO2. However, WT drawdown did increase ecosystem respiration (ER) and gross primary productivity (GPP) relative to pristine plots. WT drawdown also altered the response of GPP to light availability and WT position, as well as the temperature sensitivity (Q10) of ER. Surprisingly, mean CH4 emissions did not change as a result of WT drawdown, though fewer ebullition events were observed in the drought plot. Four years post-fire, NEE was higher (net C sink) in the burned plot compared to the unburned (75 years since fire) plot. As expected, we found a negative relationship between ER and WT in the unburned plot, but this pattern was reversed in the burned plot, where ER was highest under relatively wet conditions. Despite lower plant cover in the burned plot, there were no differences in GPP between the sites, indicating high photosynthetic capacity in surviving and newly-colonizing vegetation

  13. Thorium and uranium in soil fractions and certain macromycete species in boreal forest ecosystems

    Directory of Open Access Journals (Sweden)

    M. M. Vinichuk

    2012-07-01

    Full Text Available The content of thorium (Th and uranium (U in fractions of soil edaphosphere, rhizosphere, rhizoplane, fungal mycelium and fruit bodies were investigated. The concentrations of thorium in edaphosphere and rhizosphere fractions and mycelia of fungi are not different significantly and vary in the range of 0.74–1.45 mg kg–1 dry matter. The concentration of thorium in the rhizoplane fraction is 4 times lower than in the bulk soil – edaphosphere. The concentrations of uranium in edaphosphere, rhizosphere and rhizoplane fractions and fungi mycelium are not significantly different and vary between 3.11 and 9.36 mg kg–1 dry matter. The content of the studied natural isotopes in fruit bodies of fungi is 270 times lower than in the bulk soil: biological absorption coefficients of uranium and thorium in fruit bodies are on average 0.035 and 0.006, respectively. The contents of thorium and uranium in fungal mycelium and fruit bodies increase with increasing their concentrations in the soil. It is shown that in the fungi mycelium of the upper (0–5 cm layer of forest soil can be allocated 2.0–5.0 and 1.4–2.7 % of the total thorium and uranium soil content, respectively.

  14. Bioaccumulation of microcystins in invasive bivalves: A case study from the boreal lagoon ecosystem

    Directory of Open Access Journals (Sweden)

    Aistė Paldavičienė

    2015-01-01

    Full Text Available In the current study we present the first report on the bioaccumulation of microcystins (MC in zebra mussel Dreissena polymorpha from the eutrophic brackish water Curonian Lagoon. The bioaccumulation capacity was related to age structure of mussels and ambient environmental conditions. We also discuss the relevant implications of these findings for biomonitoring of toxic cyanobacteria blooms in the Curonian Lagoon and potential consequences for D. polymorpha cultivation activities considered for the futures as remediation measure. Samples for the analysis were collected twice per year, in June and September, in 2006, 2007 and 2008, from two sites within the littoral zone of the lagoon. The highest microcystin concentrations were measured in mussels larger than 30 mm length and sampled in 2006 (when a severe toxic cyanobacteria bloom occurred. In the following years, a consistent reduction in bioaccumulated MC concentration was noticed. However, certain amount of microcystin was recorded in mussel tissues in 2007 and 2008, when no cyanotoxins were reported in the phytoplankton. Considering high depuration rates and presence of cyanotoxins in the bottom sediments well after the recorded toxic blooms, we assume mechanism of secondary contamination when microcystin residuals could be uptaken by mussels with resuspended sediment particles.

  15. Remote Sensing of Forest Cover in Boreal Zones of the Earth

    Science.gov (United States)

    Sedykh, V. N.

    2011-12-01

    Ecological tension resulting from human activities generates a need for joint efforts of countries in the boreal zone aimed at sustainable forest development, including: conservation of forests binding carbon and ensuring stability of the atmosphere gas composition; preservation of purity and water content of forest areas as conditions ensuring sustainability of the historically formed structure of forest landscapes; and preservation of all flora and fauna species composition diversity as a condition for sustainable existence and functioning of forest ecosystems. We have to address these problems urgently due to climate warming which can interact with the forest cover. In particular, in the forest zone of Siberia, the climate aridization will inevitably result in periodic drying of shallow bogs and upland forests with thick forest litter. This will bring fires of unprecedented intensity which will lead to catastrophic atmospheric pollution. In this connection, the above problems can be solved only by the united efforts of boreal-zone countries, through establishing a uniform system for remote sensing of forests aimed at obtaining and periodic update of comprehensive information for rational decision-making in prevention of adverse human effect on the forest. A need to join efforts in this field of natural resource management is determined by disparate data which were created expressly for economic accounting units used mainly for the solution of economic timber resource problems. However, ecological tasks outlined above can be solved appropriately only by using uniform technologies that are registered within natural territorial complexes (landscapes) established throughout the entire boreal zone. Knowledge of forest state within natural territorial entities having specific physiographic conditions, with account for current and future anthropogenic load, allow one to define evidence-based forest growth potential at these landscapes to ensure development of

  16. Vegetation and climate in the Western Sayan Mts according to pollen data from Lugovoe Mire as a background for prehistoric cultural change in southern Middle Siberia

    Science.gov (United States)

    Blyakharchuk, Tatiana A.; Chernova, Natalia A.

    2013-09-01

    On the basis of pollen and spore analyses and radiocarbon dating of peat deposits of Lugovoe Mire in southern Middle Siberia, changes of vegetation and climate of the Western Sayan Mts and the Khakasia Republic (Russia) since 6000 yr 14C BP (5000 cal yr BC) are found to correspond with the development of archaeological cultures and with the pollen-based palaeoclimatic reconstruction of Levina and Orlova (1993) constructed for the forest-steppe zone of the south of West Siberia. Three phases in the development of the regional vegetation (Abies, Betula, and Pinus) are distinguished in the pollen diagram of Lugovoe Mire, which form the environmental background for the archaeological cultures developed in this region. The first penetration of ancient hunting-fishing tribes into this area occurred during the ‘Abies stage' of the vegetation. Bronze Age cultures practiced agriculture and animal husbandry mostly during the ‘Betula stage'. Beginning in the Iron Age, archaeological cultures bloomed in the study area on the background of expanding Pinus sylvestris forests. The origin of all these cultures was connected with migrations of people from the southwest or southeast. An important reason for these migrations was dry climatic phases at millennial intervals, which influenced especially strongly the more southerly homelands of the migrating ancient tribes.

  17. Developing Dynamic Reference Models and a Decision Support Framework for Southeastern Ecosystems: An Integrated Approach

    Science.gov (United States)

    2015-06-01

    matter content. Communications in Soil Science and Plant Analysis 37:939-943. Perié, C. and R. Ouimet. 2008. Organic carbon, organic matter and...bulk density relationships in boreal forest soils . Canandian Journal of Soil Science 88:315-325. Pinheiro, J., D. Bates, S. DebRoy, and D. Sarkar...Long Term Biodiversity Trends in a Spatially and Temporally Dynamic Ecosystem. Ecological Society of America Annual Meeting, Austin, Texas, 2011

  18. Land cover mapping, fire regeneration, and scaling studies in the Canadian boreal forest with 1 km AVHRR and Landsat TM data

    Science.gov (United States)

    Steyaert, L.T.; Hall, F.G.; Loveland, T.R.

    1997-01-01

    A multitemporal 1 km advanced very high resolution radiometer (AVHRR) land cover analysis approach was used as the basis for regional land cover mapping, fire disturbance-regeneration, and multiresolution land cover scaling studies in the boreal forest ecosystem of central Canada. The land cover classification was developed by using regional field observations from ground and low-level aircraft transits to analyze spectral-temporal clusters that were derived from an unsupervised cluster analysis of monthly normalized difference vegetation index (NDVI) image composites (April-September 1992). Quantitative areal proportions of the major boreal forest components were determined for a 821 km ?? 619 km region, ranging from the southern grasslands-boreal forest ecotone to the northern boreal transitional forest. The boreal wetlands (mostly lowland black spruce, tamarack, mosses, fens, and bogs) occupied approximately 33% of the region, while lakes accounted for another 13%. Upland mixed coniferous-deciduous forests represented 23% of the ecosystem. A SW-NE productivity gradient across the region is manifested by three levels of tree stand density for both the boreal wetland conifer and the mixed forest classes, which are generally aligned with isopleths of regional growing degree days. Approximately 30% of the region was directly affected by fire disturbance within the preceding 30-35 years, especially in the Canadian Shield Zone where large fire-regeneration patterns contribute to the heterogeneous boreal landscape. Intercomparisons with land cover classifications derived from 30-m Landsat Thematic Mapper (TM) data provided important insights into the relative accuracy of the 1 km AVHRR land cover classification. Primarily due to the multitemporal NDVI image compositing process, the 1 km AVHRR land cover classes have an effective spatial resolution in the 3-4 km range; therefore fens, bogs, small water bodies, and small patches of dry jack pine cannot be resolved within

  19. Microbial Ecosystems, Protection of

    NARCIS (Netherlands)

    Bodelier, P.L.E.; Nelson, K.E.

    2014-01-01

    Synonyms Conservation of microbial diversity and ecosystem functions provided by microbes; Preservation of microbial diversity and ecosystem functions provided by microbes Definition The use, management, and conservation of ecosystems in order to preserve microbial diversity and functioning. Introdu

  20. Net Ecosystem Carbon Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Net Ecosystem Carbon Flux is defined as the year-over-year change in Total Ecosystem Carbon Stock, or the net rate of carbon exchange between an ecosystem and the...

  1. Astronomical Ecosystems

    Science.gov (United States)

    Neuenschwander, D. E.; Finkenbinder, L. R.

    2004-05-01

    Just as quetzals and jaguars require specific ecological habitats to survive, so too must planets occupy a tightly constrained astronomical habitat to support life as we know it. With this theme in mind we relate the transferable features of our elementary astronomy course, "The Astronomical Basis of Life on Earth." Over the last five years, in a team-taught course that features a spring break field trip to Costa Rica, we have introduced astronomy through "astronomical ecosystems," emphasizing astronomical constraints on the prospects for life on Earth. Life requires energy, chemical elements, and long timescales, and we emphasize how cosmological, astrophysical, and geological realities, through stabilities and catastrophes, create and eliminate niches for biological life. The linkage between astronomy and biology gets immediate and personal: for example, studies in solar energy production are followed by hikes in the forest to examine the light-gathering strategies of photosynthetic organisms; a lesson on tides is conducted while standing up to our necks in one on a Pacific beach. Further linkages between astronomy and the human timescale concerns of biological diversity, cultural diversity, and environmental sustainability are natural and direct. Our experience of teaching "astronomy as habitat" strongly influences our "Astronomy 101" course in Oklahoma as well. This "inverted astrobiology" seems to transform our student's outlook, from the universe being something "out there" into something "we're in!" We thank the SNU Science Alumni support group "The Catalysts," and the SNU Quetzal Education and Research Center, San Gerardo de Dota, Costa Rica, for their support.

  2. Using Support Vector Machines to Automatically Extract Open Water Signatures from POLDER Multi-Angle Data Over Boreal Regions

    Science.gov (United States)

    Pierce, J.; Diaz-Barrios, M.; Pinzon, J.; Ustin, S. L.; Shih, P.; Tournois, S.; Zarco-Tejada, P. J.; Vanderbilt, V. C.; Perry, G. L.; Brass, James A. (Technical Monitor)

    2002-01-01

    This study used Support Vector Machines to classify multiangle POLDER data. Boreal wetland ecosystems cover an estimated 90 x 10(exp 6) ha, about 36% of global wetlands, and are a major source of trace gases emissions to the atmosphere. Four to 20 percent of the global emission of methane to the atmosphere comes from wetlands north of 4 degrees N latitude. Large uncertainties in emissions exist because of large spatial and temporal variation in the production and consumption of methane. Accurate knowledge of the areal extent of open water and inundated vegetation is critical to estimating magnitudes of trace gas emissions. Improvements in land cover mapping have been sought using physical-modeling approaches, neural networks, and active microwave, examples that demonstrate the difficulties of separating open water, inundated vegetation and dry upland vegetation. Here we examine the feasibility of using a support vector machine to classify POLDER data representing open water, inundated vegetation and dry upland vegetation.

  3. Climate, soil organic layer, and nitrogen jointly drive forest development after fire in the North American boreal zone

    Science.gov (United States)

    Trugman, A. T.; Fenton, N. J.; Bergeron, Y.; Xu, X.; Welp, L. R.; Medvigy, D.

    2016-09-01

    Previous empirical work has shown that feedbacks between fire severity, soil organic layer thickness, tree recruitment, and forest growth are important factors controlling carbon accumulation after fire disturbance. However, current boreal forest models inadequately simulate this feedback. We address this deficiency by updating the ED2 model to include a dynamic feedback between soil organic layer thickness, tree recruitment, and forest growth. The model is validated against observations spanning monthly to centennial time scales and ranging from Alaska to Quebec. We then quantify differences in forest development after fire disturbance resulting from changes in soil organic layer accumulation, temperature, nitrogen availability, and atmospheric CO2. First, we find that ED2 accurately reproduces observations when a dynamic soil organic layer is included. Second, simulations indicate that the presence of a thick soil organic layer after a mild fire disturbance decreases decomposition and productivity. The combination of the biological and physical effects increases or decreases total ecosystem carbon depending on local conditions. Third, with a 4°C temperature increase, some forests transition from undergoing succession to needleleaf forests to recruiting multiple cohorts of broadleaf trees, decreasing total ecosystem carbon by ˜40% after 300 years. However, the presence of a thick soil organic layer due to a persistently mild fire regime can prevent this transition and mediate carbon losses even under warmer temperatures. Fourth, nitrogen availability regulates successional dynamics; broadleaf species are less competitive with needleleaf trees under low nitrogen regimes. Fifth, the boreal forest shows additional short-term capacity for carbon sequestration as atmospheric CO2 increases.

  4. Diatoms in peat – dominant producers in a changing environment?

    DEFF Research Database (Denmark)

    Kokfelt, Ulla; Struyf, Eric; Randsalu, Linda

    2009-01-01

    Changes in hydrology and temperature can induce rapid changes in boreal wetland ecosystems. Factors such as hydrosere, permafrost, climate and human interference may disturb the prevailing mire vegetation, whereby a new dominant assemblage can develop. At the transition from one vegetation type...... content. Biogenic silica and other nutrients that would otherwise be lost during mineralization in runoff are in this way retained in the ecosystem. Our results imply that silica storage originating from diatoms can be expected to increase in today's rapidly changing boreal wetlands. The impacts...

  5. Disrupted trophic interactions affect recruitment of boreal deciduous and coniferous trees in northern Europe.

    Science.gov (United States)

    Angelstam, Per; Manton, Michael; Pedersen, Simen; Elbakidze, Marine

    2017-01-23

    Loss of large carnivore populations may lead to increased population densities of large herbivores, and subsequent cascading effects on the composition, structure and function of ecosystems. Using a macroecological approach based on studies in multiple boreal forest landscapes in the Baltic Sea region and Russia, we tested the hypothesis that disrupted trophic interactions among large carnivores and large herbivores affect the recruitment of both ecologically and economically valuable tree species. We measured damage levels on young trees and large herbivore density in 10 local landscapes representing a gradient from extinct to extant populations of both large carnivores and large herbivores. We also tested the alternative hypothesis that forest management intensity is correlated to reduced recruitment of these tree species. At the macroecological scale there was an inverse relationship between the number of large carnivores and large herbivores. This coincided with a steep gradient in browsing damage on the ecologically important aspen, rowan and sallow as hosts for specialised species, as well as the economically important Scots pine. In one landscape hunting had replaced the presence of carnivores. Mean damage levels of these four tree species were correlated with large herbivore abundance, but not with forest management intensity. We discuss the pros and cons of this macroecological approach, as well as the challenge of governing and managing trophic interactions at multiple scales. This article is protected by copyright. All rights reserved.

  6. Effects of Lakes on Wildfire Activity in the Boreal Forests of Saskatchewan, Canada

    Directory of Open Access Journals (Sweden)

    Scott E. Nielsen

    2016-11-01

    Full Text Available Large lakes can act as firebreaks resulting in distinct patterns in the forest mosaic. Although this is well acknowledged, much less is known about how wildfire is affected by different landscape measures of water and their interactions. Here we examine how these factors relate to historic patterns of wildfire over a 35-year period (1980–2014 for the boreal forest of Saskatchewan, Canada. This includes the amount of water in different-sized neighborhoods, the presence of islands, and the direction, distance, and shape of nearest lake of different sizes. All individual factors affected wildfire presence, with lake sizes ≥5000 ha and amount of water within a 1000-ha surrounding area the most supported spatial scales. Overall, wildfires were two-times less likely on islands, more likely further from lakes that were circular in shape, and in areas with less surrounding water. Interactive effects were common, including the effect of direction to lake as a function of distance from lakeshore and amount of surrounding water. Our results point to a strong, but complex, bottom-up control of local wildfire activity based on the configuration of natural firebreaks. In fact, fire rotation periods predicted for one area varied more than 15-fold (<47 to >700 years depending on local patterns in lakes. Old-growth forests within this fire-prone ecosystem are therefore likely to depend on the surrounding configuration of larger lakes.

  7. Sunscreening fungal pigments influence the vertical gradient of pendulous lichens in boreal forest canopies.

    Science.gov (United States)

    Färber, Leonie; Sølhaug, Knut Asbjorn; Esseen, Per-Anders; Bilger, Wolfgang; Gauslaa, Yngvar

    2014-06-01

    Pendulous lichens dominate canopies of boreal forests, with dark Bryoria species in the upper canopy vs. light Alectoria and Usnea species in lower canopy. These genera offer important ecosystem services such as winter forage for reindeer and caribou. The mechanism behind this niche separation is poorly understood. We tested the hypothesis that species-specific sunscreening fungal pigments protect underlying symbiotic algae differently against high light, and thus shape the vertical canopy gradient of epiphytes. Three pale species with the reflecting pigment usnic acid (Alectoria sarmentosa, Usnea dasypoga, U. longissima) and three with dark, absorbing melanins (Bryoria capillaris, B. fremontii, B. fuscescens) were compared. We subjected the lichens to desiccation stress with and without light, and assessed their performance with chlorophyll fluorescence. Desiccation alone only affected U. longissima. By contrast, light in combination with desiccation caused photoinhibitory damage in all species. Usnic lichens were significantly more susceptible to light during desiccation than melanic ones. Thus, melanin is a more efficient light-screening pigment than usnic acid. Thereby, the vertical gradient of pendulous lichens in forest canopies is consistent with a shift in type and functioning of sunscreening pigments, from high-light-tolerant Bryoria in the upper to susceptible Alectoria and Usnea in the lower canopy.

  8. Krupneishi v mire muzei

    Index Scriptorium Estoniae

    2006-01-01

    Egiptuses Aleksandrias avatakse vabaõhu antiikmuuseum. Muuseumi ekspositsioonideks on kultuuri- ja arhitektuurimälestised nagu taastatud rooma amfiteater, saunad, sfinkid, obeliskid. 2010. aastaks planeeritakse Giza püramiidide juurde ehitada maailma suurim muuseumikompleks

  9. Bacterial Genomics Reveal the Complex Epidemiology of an Emerging Pathogen in Arctic and Boreal Ungulates

    Directory of Open Access Journals (Sweden)

    Taya L. Forde

    2016-11-01

    Full Text Available Northern ecosystems are currently experiencing unprecedented ecological change, largely driven by a rapidly changing climate. Pathogen range expansion, and emergence and altered patterns of infectious disease, are increasingly reported in wildlife at high latitudes. Understanding the causes and consequences of shifting pathogen diversity and host-pathogen interactions in these ecosystems is important for wildlife conservation, and for indigenous populations that depend on wildlife. Among the key questions are whether disease events are associated with endemic or recently introduced pathogens, and whether emerging strains are spreading throughout the region. In this study, we used a phylogenomic approach to address these questions of pathogen endemicity and spread for Erysipelothrix rhusiopathiae, an opportunistic multi-host bacterial pathogen associated with recent mortalities in arctic and boreal ungulate populations in North America. We isolated E. rhusiopathiae from carcasses associated with large-scale die-offs of muskoxen in the Canadian Arctic Archipelago, and from contemporaneous mortality events and/or population declines among muskoxen in northwestern Alaska and caribou and moose in western Canada. Bacterial genomic diversity differed markedly among these locations; minimal divergence was present among isolates from muskoxen in the Canadian Arctic, while in caribou and moose populations, strains from highly divergent clades were isolated from the same location, or even from within a single carcass. These results indicate that mortalities among northern ungulates are not associated with a single emerging strain of E. rhusiopathiae, and that alternate hypotheses need to be explored. Our study illustrates the value and limitations of bacterial genomic data for discriminating between ecological hypotheses of disease emergence, and highlights the importance of studying emerging pathogens within the broader context of environmental and host

  10. Flow regulation effects on the hydrogeochemistry of the hyporheic zone in boreal rivers.

    Science.gov (United States)

    Siergieiev, D; Widerlund, A; Ingri, J; Lundberg, A; Öhlander, B

    2014-11-15

    River-aquifer interfaces are essential for ecosystem functioning in terms of nutrient exchange and biological habitat, but are greatly threatened world-wide. This study examined geochemical aspects of river-aquifer interaction in one regulated and one unregulated boreal river in Northern Sweden to determine whether the geochemical functioning of the hyporheic zone is affected by hydrological alterations, e.g. regulated river discharge and river-aquifer connectivity. In the unregulated Kalix River, the hyporheic pore water was well-oxygenated with orthogonal fluxes (≈0.6-0.7 m d(-1)) and acted as a sink for Fe, Mn, Al, NH4, and Ca, with fractional losses of 95%, 92%, 45%, 31%, and 15%, respectively. A corresponding elevation in the concentrations of these elements in the hyporheic sediment was observed, with higher saturation indices of Fe-, Mn-, and Al-bearing secondary minerals in hyporheic waters. In the regulated Lule River, hydraulic connectivity at the river-aquifer interface was altered by the presence of a clogging layer (0.04 m d(-1)). In addition, the river discharge oscillated daily, severely reducing exchange flows across the riverbed (<0.01 m d(-1)). As a result, the hyporheic pore water was suboxic, with elevated concentrations of filtered Fe and Mn (fractional increases of ≈3700% and ≈2500%, respectively) and other solutes (NH4, Si, S, Ca). A conceptual model revealed functional differences between geochemical features of the hyporheic zone of regulated and unregulated rivers. Overall, the results showed that hyporheic processes are altered along regulated rivers, with resulting impacts on the geochemistry of riverine, riparian and related marine ecosystems.

  11. Potential effects of climate change on ecosystem distribution in Alberta

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, R.R.; Farr, D.; Boutin, S. [Alberta Univ., Edmonton, AB (Canada). Dept. of Biological Sciences; Hamann, A.; Wang, X. [Alberta Univ., Edmonton, AB (Canada). Dept of Renewable Resources

    2009-05-15

    This paper proposed a method of extending the utility of bioclimatic envelope models for land use planning and adaptation under climate change. The trajectory of vegetation changes was set by the model, while the rate of transition was determined using a disturbance model. The method was used to explore potential changes to the distribution of ecosystems in Alberta under various climate and disturbance scenarios. The study showed that use of the disturbance model slowed the rate of ecosystem transition when compared with the results obtained from the bioclimatic envelope model alone. A northward shift of grasslands into large areas of existing parklands occurred over the simulation's 50-year time period. Between 12 and 21 per cent of Alberta's Boreal region was converted to parklands. Boreal transitions will initially occur in forests adjacent to current parklands and spread outwards. Fires over 100 km {sup 2} provided an indication of the anticipated size of potential transition patches. It was concluded that using a disturbance model to quantify transition logs can improve uncertainties in the parameter estimates of bioclimatic envelope models. 43 refs., 3 tabs., 3 figs.

  12. Determination of elemental baseline using peltigeralean lichens from Northeastern Canada (Québec): Initial data collection for long term monitoring of the impact of global climate change on boreal and subarctic area in Canada.

    Science.gov (United States)

    Darnajoux, Romain; Lutzoni, François; Miadlikowska, Jolanta; Bellenger, Jean-Philippe

    2015-11-15

    Northeastern Canada is mostly free of anthropogenic activities. The extent to which this territory has been impacted by anthropogenic atmospheric depositions remains to be studied. The main goal of our study was to establish background levels for metals in boreal muscicolous/terricolous macrolichens over non-urbanized areas of northeastern Canada (Québec). Concentrations of 18 elements (Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, and Pb) were determined for three species of the genus Peltigera (Peltigera aphthosa (L.) Willd. s.l., Peltigera neopolydactyla (Gyeln.) Gyeln. s.l., Peltigera scabrosa Th. Fr. s.l.), and Nephroma arcticum (L.) Torss., along a 1080 km south-north transect and along a of 730 km west-east transect. We report that elemental contents in the sampled lichen thalli are very low and similar to background levels found in other studies performed in pristine places (high elevation or remote ecosystems) throughout the world. Overall, our results demonstrate that most of the boreal and subarctic zone of Québec (northeastern Canada) is still pristine. The elemental baseline established in these lichen populations will contribute to monitor metal pollution in boreal and sub-polar ecosystems due to global climate change and future industrial expansion.

  13. Discrimination of rewetted / renaturated habitats from natural moist habitat in a mire by means of DOM quality differences using fluorescence indices

    Science.gov (United States)

    Herzsprung, Peter; Osterloh, Katja; von Tümpling, Wolf; Harir, Mourad; Hertkorn, Norbert; Meissner, Ralf; Friese, Kurt; Bernsdorf, Sabine; Schmitt-Kopplin, Philippe

    2015-04-01

    Discrimination of rewetted / renaturated habitats from natural moist habitat in a mire by means of DOM quality differences using fluorescence indices Mires can be a potential source of dissolved organic matter load (DOC) in fresh water catchment areas. Renaturation and rewetting of formerly drained mire sites is often debated in terms of nature protection aspects as well as in terms of climatic and adjacent water protection. Latter aspect is closely connected with the drinking water supply and thus of major human interest. In this case the Central German uplands play an important role. For estimation of potential leaching of humic substances the principal comparison of natural habitat with artificially rewetted habitats concerning dissolved organic matter quality can be of interest. In this regard a partly rewetted mire in the Harz Mountains, Germany was investigated. Seven locations, one oligotrophic natural, one mesotrophic natural, and together 5 rewetted locations were investigated. The soil water of all sites was sampled monthly and its quality was analysed by bulk parameters like DOC and bulk optical parameters like excitation emission matrix fluorescence (EEM) and UV spectra. Water was pumped from piezometers and immediately filtered. Each site consisted of four parallel piezometers in the peat soil. Samples were stored at 4° C before analysis. All spectroscopic data, both UV spectra and EEM were recorded simultaneously. Fluorescence EEMs were collected using a spectrofluorometer (AQUALOG, HORIBA Jobin Yvon, USA). Fluorescence intensity was measured during emission scans (240 nm - 600 nm every 3.27 nm, 8 pixel) at set excitation wavelength in 3 nm increments from 240 nm to 600 nm. The fluorescence indices freshness (ß/α), Fluorescence Index (FI), and Humification Index (HIX) were calculated [1] from the inner filter effect (IFE) corrected EEM spectra. The natural habitat could be clearly discriminated from the rewetted sites. The DOC, UV absorption at 254

  14. The influence of storm-induced microsites to tree regeneration patterns in boreal and hemiboreal forest

    NARCIS (Netherlands)

    Vodde, F.; Jogiste, K.; Kubota, Y.; Kuuluvainen, T.; Koster, K.; Lukjanova, A.; Metslaid, M.; Yoshida, T.

    2011-01-01

    We reviewed studies dealing with regeneration under variable conditions in boreal and hemiboreal forests as affected by different microsite types by tree species functional groups. Generally, the importance of storm-induced microsites for regeneration dynamics in boreal forests depends on several fa

  15. Comprehensive radiative forcing assesment highlights trade-offs in climate mitigation potential of managed boreal forests

    Science.gov (United States)

    Kalliokoski, Tuomo; Berninger, Frank; Bäck, Jaana; Boy, Michael; Kuusinen, Nea; Mäkelä, Annikki; Matthies, Brent; Minkkinen, Kari; Mogensen, Ditte; Peltoniemi, Mikko; Sievänen, Risto; Zhou, Luxi; Vanhatalo, Anni; Valsta, Lauri; Nikinmaa, Eero

    2016-04-01

    Boreal forests have an important role in the mitigation of climate change. In this study we evaluated four key climate impacts of forest management: (1) carbon sequestration (in forest ecosystems and wood products), (2) surface albedo of forest area, (3) forest originating Secondary Organic Aerosols (SOA) and (4) avoided CO2-emissions from wood energy and product substitution. We calculated their net effect at both a single stand and regional level using Finland as a case study. We made analyses both in current climate up to a year 2050 and in the projected climate of year 2050. At the stand level, the carbon sequestration effect and avoided CO2 emissions due to substituted materials dominated in net RF in current climate. The warming effect of surface albedo of forest cover was lower or of same magnitude than cooling effect of SOAs. Together, the rarely considered SOAs and product substitution corresponded over 70% of the total cooling effect of forest cover. The cooling effect of net radiative forcing increased along the increasing site fertility. Although the carbon stocks of broadleaved trees were smaller than that of conifers their total radiative cooling effect was larger due to the integrated albedo and aerosol effects. In the projected climate of 2050, the radiative cooling of aerosols approached the level of forest carbon fixation. These results emphasize the need for holistic evaluation of climate impacts over simple carbon sequestration analysis to understand the role of forest management in climate change mitigation. Landscape level analyses emphasized the broad range of options to reach the cooling effect. The lowest harvest regime, 50% of current annual increment (CAI), yielded the largest cooling effect. Yet, harvests up to CAI produced only slightly less cooling RF if avoided emissions were considered. This result was highly sensitive to used substitution factors. Our result highlights that the combination of intensive harvests and the use of wood

  16. Simulating ozone dry deposition at a boreal forest with a multi-layer canopy deposition model

    Science.gov (United States)

    Zhou, Putian; Ganzeveld, Laurens; Rannik, Üllar; Zhou, Luxi; Gierens, Rosa; Taipale, Ditte; Mammarella, Ivan; Boy, Michael

    2017-01-01

    A multi-layer ozone (O3) dry deposition model has been implemented into SOSAA (a model to Simulate the concentrations of Organic vapours, Sulphuric Acid and Aerosols) to improve the representation of O3 concentration and flux within and above the forest canopy in the planetary boundary layer. We aim to predict the O3 uptake by a boreal forest canopy under varying environmental conditions and analyse the influence of different factors on total O3 uptake by the canopy as well as the vertical distribution of deposition sinks inside the canopy. The newly implemented dry deposition model was validated by an extensive comparison of simulated and observed O3 turbulent fluxes and concentration profiles within and above the boreal forest canopy at SMEAR II (Station to Measure Ecosystem-Atmosphere Relations II) in Hyytiälä, Finland, in August 2010. In this model, the fraction of wet surface on vegetation leaves was parametrised according to the ambient relative humidity (RH). Model results showed that when RH was larger than 70 % the O3 uptake onto wet skin contributed ˜ 51 % to the total deposition during nighttime and ˜ 19 % during daytime. The overall contribution of soil uptake was estimated about 36 %. The contribution of sub-canopy deposition below 4.2 m was modelled to be ˜ 38 % of the total O3 deposition during daytime, which was similar to the contribution reported in previous studies. The chemical contribution to O3 removal was evaluated directly in the model simulations. According to the simulated averaged diurnal cycle the net chemical production of O3 compensated up to ˜ 4 % of dry deposition loss from about 06:00 to 15:00 LT. During nighttime, the net chemical loss of O3 further enhanced removal by dry deposition by a maximum ˜ 9 %. Thus the results indicated an overall relatively small contribution of airborne chemical processes to O3 removal at this site.

  17. Methane emission modeling with MCMC calibration for a boreal peatland

    Science.gov (United States)

    Raivonen, Maarit; Smolander, Sampo; Susiluoto, Jouni; Backman, Leif; Li, Xuefei; Markkanen, Tiina; Kleinen, Thomas; Makela, Jarmo; Aalto, Tuula; Rinne, Janne; Brovkin, Victor; Vesala, Timo

    2016-04-01

    Natural wetlands, particularly peatlands of the boreal latitudes, are a significant source of methane (CH4). At the moment, the emission estimates are highly uncertain. These natural emissions respond to climatic variability, so it is necessary to understand their dynamics, in order to be able to predict how they affect the greenhouse gas balance in the future. We have developed a model of CH4 production, oxidation and transport in boreal peatlands. It simulates production of CH4 as a proportion of anaerobic peat respiration, transport of CH4 and oxygen between the soil and the atmosphere via diffusion in aerenchymatous plants and in peat pores (water and air filled), ebullition and oxidation of CH4 by methanotrophic microbes. Ultimately, we aim to add the model functionality to global climate models such as the JSBACH (Reick et al., 2013), the land surface scheme of the MPI Earth System Model. We tested the model with measured methane fluxes (using eddy covariance technique) from the Siikaneva site, an oligotrophic boreal fen in southern Finland (61°49' N, 24°11' E), over years 2005-2011. To give the model estimates regional reliability, we calibrated the model using Markov chain Monte Carlo (MCMC) technique. Although the simulations and the research are still ongoing, preliminary results from the MCMC calibration can be described as very promising considering that the model is still at relatively early stage. We will present the model and its dynamics as well as results from the MCMC calibration and the comparison with Siikaneva flux data.

  18. A new model for estimating boreal forest fPAR

    Science.gov (United States)

    Majasalmi, Titta; Rautiainen, Miina; Stenberg, Pauline

    2014-05-01

    Life on Earth is continuously sustained by the extraterrestrial flux of photosynthetically active radiation (PAR, 400-700 nm) from the sun. This flux is converted to biomass by chloroplasts in green vegetation. Thus, the fraction of absorbed PAR (fPAR) is a key parameter used in carbon balance studies, and is listed as one of the Essential Climate Variables (ECV). Temporal courses of fPAR for boreal forests are difficult to measure, because of the complex 3D structures. Thus, they are most often estimated based on models which quantify the dependency of absorbed radiation on canopy structure. In this study, we adapted a physically-based canopy radiation model into a fPAR model, and compared modeled and measured fPAR in structurally different boreal forest stands. The model is based on the spectral invariants theory, and uses leaf area index (LAI), canopy gap fractions and spectra of foliage and understory as input data. The model differs from previously developed more detailed fPAR models in that the complex 3D structure of coniferous forests is described using an aggregated canopy parameter - photon recollision probability p. The strength of the model is that all model inputs are measurable or available through other simple models. First, the model was validated with measurements of instantaneous fPAR obtained with the TRAC instrument in nine Scots pine, Norway spruce and Silver birch stands in a boreal forest in southern Finland. Good agreement was found between modeled and measured fPAR. Next, we applied the model to predict temporal courses of fPAR using data on incoming radiation from a nearby flux tower and sky irradiance models. Application of the model to simulate diurnal and seasonal values of fPAR indicated that the ratio of direct-to-total incident radiation and leaf area index are the key factors behind the magnitude and variation of stand-level fPAR values.

  19. Nitrogen fixation in boreal peatlands: the effects of increased N deposition on N2-fixation

    Science.gov (United States)

    Popma, J. M.; Wieder, R.; Lamers, L.; Vile, M. A.

    2013-12-01

    -1 yr-1, mean × std err for 2012 and 2013, respectively) followed by progressively lower rates with a low of 5.02 × 0.87 in 2012 and 8.94 × 3.09 in 2013 (mean × std err). As biological N2-fixation is an energetically costly process, up-regulating enzyme activity when N availability is low and down-regulating activity when N deposition is enhanced makes thermodynamic and evolutionary sense. N2-fixation shows to be one of the most early-warning indicators to the early response of boreal peatlands to increased N deposition, and can aid in setting critical loads to protect these historically pristine ecosystems.

  20. Stomata-controlled nighttime COS fluxes in a boreal forest: implications for the use of COS as a GPP tracer

    Science.gov (United States)

    Kooijmans, Linda M. J.; Maseyk, Kadmiel; Seibt, Ulli; Vesala, Timo; Mammarella, Ivan; Baker, Ian T.; Franchin, Alessandro; Kolari, Pasi; Sun, Wu; Keskinen, Helmi; Levula, Janne; Chen, Huilin

    2016-04-01

    Carbonyl Sulfide (COS) is a promising new tracer that can be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. COS and CO2 vegetation fluxes are closely related as these gases share the same diffusion pathway into stomata. This close coupling is the fundamental principle for the use of COS as tracer for GPP. Nonetheless, in contrast to CO2 , the uptake of COS by vegetation is not light-dependent, and therefore the vegetative uptake of COS can continue during the night as long as stomata are open. Nighttime stomatal conductance is observed in a variety of studies, and also nighttime depletion of COS concentrations is reported several times but it is not confirmed with field measurements that the depletion of COS in the night is indeed driven by stomatal opening. In the summer of 2015 a campaign took place at the SMEAR II site in Hyytiälä, Finland to provide better constrained COS flux data for boreal forests using a combination of COS measurements, i.e. atmospheric profile concentrations up to 125 m, eddy-covariance fluxes and soil chamber fluxes, and collocated measurements of stomatal conductance and 222Radon. A high correlation between concentrations of 222Radon and COS implies that the radon-tracer method is a valuable tool to derive nighttime ecosystem COS fluxes. We find that soils contribute to 17% of the total ecosystem COS flux during nighttime in the peak growing season. Nighttime ecosystem COS fluxes show a correlation with stomatal conductance (R2 = 0.3), indicating that nighttime COS fluxes are primarily driven by vegetation. The COS vegetation fluxes will be compared with calculated fluxes from the Simple Biosphere model. Furthermore, the nighttime vegetative COS uptake covers a substantial fraction (25%) of the daily maximum COS uptake by vegetation. Accurate quantification of nighttime COS uptake is required to be able to use COS as a useful tracer for GPP.

  1. Host associations between fungal root endophytes and boreal trees.

    Science.gov (United States)

    Kernaghan, Gavin; Patriquin, Glenn

    2011-08-01

    Fungal root endophytes colonize root tissue concomitantly with mycorrhizal fungi, but their identities and host preferences are largely unknown. We cultured fungal endophytes from surface-sterilized Cenococcum geophilum ectomycorrhizae of Betula papyrifera, Abies balsamea, and Picea glauca from two boreal sites in eastern Canada. Isolates were initially grouped on the basis of cultural morphology and then identified by internal transcribed spacer ribosomal DNA sequencing or by PCR restriction fragment length polymorphism. Phylogenetic analysis of the sequence data revealed 31 distinct phylotypes among the isolates, comprising mainly members of the ascomycete families Helotiaceae, Dermateaceae, Myxotrichaceae, and Hyaloscyphaceae, although other fungi were also isolated. Multivariate analyses indicate a clear separation among the endophyte communities colonizing each host tree species. Some phylotypes were evenly distributed across the roots of all three host species, some were found preferentially on particular hosts, and others were isolated from single hosts only. The results indicate that fungal root endophytes of boreal trees are not randomly distributed, but instead form relatively distinct assemblages on different host tree species.

  2. Antioxidant Potential of Bark Extracts from Boreal Forest Conifers

    Directory of Open Access Journals (Sweden)

    Jean Legault

    2013-07-01

    Full Text Available The bark of boreal forest conifers has been traditionally used by Native Americans to treat various ailments and diseases. Some of these diseases involve reactive oxygen species (ROS that can be prevented by the consumption of antioxidants such as phenolic compounds that can be found in medicinal plants. In this study, ultrasonic assisted extraction has been performed under various solvent conditions (water:ethanol mixtures on the bark of seven boreal forest conifers used by Native Americans including: Pinus strobus, Pinus resinosa, Pinus banksiana, Picea mariana, Picea glauca, Larix laricina, and Abies balsamea. The total phenolic content, as well as ORACFL potency and cellular antioxidant activity (IC50, were evaluated for all bark extracts, and compared with the standardized water extract of Pinus maritima bark (Pycnogenol, which showed clinical efficiency to prevent ROS deleterious effects. The best overall phenolic extraction yield and antioxidant potential was obtained with Picea glauca and Picea mariana. Interestingly, total phenolic content of these bark extracts was similar to Pycnogenol but their antioxidant activity were higher. Moreover, most of the extracts did not inhibit the growth of human skin fibroblasts, WS1. A significant correlation was found between the total phenolic content and the antioxidant activity for water extracts suggesting that these compounds are involved in the activity.

  3. Elevated ozone in boreal fire plumes - the 2013 smoke season

    Science.gov (United States)

    Trickl, T.; Vogelmann, H.; Flentje, H.; Ries, L.

    2015-05-01

    In July 2013 very strong boreal fire plumes were observed at the northern rim of the Alps by lidar and ceilometer measurements of aerosol, ozone and water vapour for about three weeks. In addition, some of the lower-tropospheric components of these layers were analyzed at the Global Atmosphere Watch laboratory at the Schneefernerhaus high-altitude research station (2650 m a.s.l., located a few hundred metres south-west of the Zugspitze summit). The high amount of particles confirms our hypothesis that fires in the Arctic regions of North America have a much stronger impact on the Central European atmosphere than the multitude of fires in the United States. This has been ascribed to the prevailing anticyclonic advection pattern during favourable periods and subsidence, in contrast to warm-conveyor-belt export, rainout and dilution frequently found for lower latitudes. A high number of the pronounced aerosol structures were positively correlated with elevated ozone. Chemical ozone formation in boreal fire plumes is known to be rather limited. Indeed, these air masses could be attributed to stratospheric air intrusions over remote high latitude regions obviously picking up the aerosol on their way across Canada. In one case subsidence from the stratosphere over Siberia over as many as 15 to 20 days without increase in humidity was observed although a significant amount of Canadian smoke was trapped. These coherent air streams lead to rather straight and rapid transport of the particles to Europe.

  4. Fire dynamics and implications for nitrogen cycling in boreal forests

    Science.gov (United States)

    Harden, Jennifer W.; Mack, Michelle; Veldhuis, Hugo; Gower, S. T.

    2003-02-01

    We used a dynamic, long-term mass balance approach to track cumulative carbon (C) and nitrogen (N) losses to fire in boreal Manitoba over the 6500 years since deglaciation. Estimated C losses to decomposition and fire, combined with measurements of N pools in mature and burned forest floors, suggest that loss of N by combustion has likely resulted in a long-term loss that exceeds the amount of N stored in soil today by 2 to 3 times. These estimates imply that biological N fixation rates could be as high as 5 to 10 times atmospheric deposition rates in boreal regions. At the site scale, the amount of N lost is due to N content of fuels, which varies by stand type and fire severity, which in turn vary with climate and fire dynamics. The interplay of fire frequency, fire severity, and N partitioning during regrowth are important for understanding rates and sustainability of nutrient and carbon cycling over millenia and over broad regions.

  5. Antioxidant Potential of Bark Extracts from Boreal Forest Conifers.

    Science.gov (United States)

    Legault, Jean; Girard-Lalancette, Karl; Dufour, Dominic; Pichette, André

    2013-07-11

    The bark of boreal forest conifers has been traditionally used by Native Americans to treat various ailments and diseases. Some of these diseases involve reactive oxygen species (ROS) that can be prevented by the consumption of antioxidants such as phenolic compounds that can be found in medicinal plants. In this study, ultrasonic assisted extraction has been performed under various solvent conditions (water:ethanol mixtures) on the bark of seven boreal forest conifers used by Native Americans including: Pinus strobus, Pinus resinosa, Pinus banksiana, Picea mariana, Picea glauca, Larix laricina, and Abies balsamea. The total phenolic content, as well as ORACFL potency and cellular antioxidant activity (IC50), were evaluated for all bark extracts, and compared with the standardized water extract of Pinus maritima bark (Pycnogenol), which showed clinical efficiency to prevent ROS deleterious effects. The best overall phenolic extraction yield and antioxidant potential was obtained with Picea glauca and Picea mariana. Interestingly, total phenolic content of these bark extracts was similar to Pycnogenol but their antioxidant activity were higher. Moreover, most of the extracts did not inhibit the growth of human skin fibroblasts, WS1. A significant correlation was found between the total phenolic content and the antioxidant activity for water extracts suggesting that these compounds are involved in the activity.

  6. What governs the presence of residual vegetation in boreal wildfires?

    Science.gov (United States)

    Araya, Yikalo H.; Remmel, Tarmo K.; Perera, Ajith H.

    2016-04-01

    Wildfires are frequent boreal forest disturbances in Canada, and emulating their patterns with forest harvesting has emerged as a common forest management goal. Wildfires contain many patches of residual vegetation of various size, shape, and composition; understanding their characteristics provides insights for improved emulation criteria. We studied the occurrence of residual vegetation within eleven boreal wildfire events in a natural setting; fires ignited by lightning, no suppression efforts, and no prior anthropogenic disturbances. Relative importance of the measurable geo-environmental factors and their marginal effects on residual presence are studied using Random Forests. These factors included distance from natural firebreaks (wetland, bedrock and non-vegetated areas, and water), land cover, and topographic variables (elevation, slope, and ruggedness index). We present results at spatial resolutions ranging from four to 64 m while emphasizing four and 32 m since they mimic IKONOS- and Landsat-type images. Natural firebreak features, especially the proximity to wetlands, are among the most important variables that explain the likelihood residual occurrence. The majority of residual vegetation areas are concentrated within 100 m of wetlands. Topographic variables, typically important in rugged terrain, are less important in explaining the presence of residuals within our study fires.

  7. Coral reefs - Specialized ecosystems

    Digital Repository Service at National Institute of Oceanography (India)

    Wafar, M.V.M.

    This paper discusses briefly some aspects that characterize and differentiate coral reef ecosystems from other tropical marine ecosystems. A brief account on the resources that are extractable from coral reefs, their susceptibility to natural...

  8. Sinks for inorganic nitrogen deposition in forest ecosystems with low and high nitrogen deposition in China.

    Science.gov (United States)

    Sheng, Wenping; Yu, Guirui; Fang, Huajun; Jiang, Chunming; Yan, Junhua; Zhou, Mei

    2014-01-01

    We added the stable isotope (15)N in the form of ((15)NH4)2SO4 and K(15)NO3 to forest ecosystems in eastern China under two different N deposition levels to study the fate of the different forms of deposited N. Prior to the addition of the (15)N tracers, the natural (15)N abundance ranging from -3.4‰ to +10.9‰ in the forest under heavy N deposition at Dinghushan (DHS), and from -3.92‰ to +7.25‰ in the forest under light N deposition at Daxinganling (DXAL). Four months after the tracer application, the total (15)N recovery from the major ecosystem compartments ranged from 55.3% to 90.5%. The total (15)N recoveries were similar under the ((15)NH4)2SO4 tracer treatment in both two forest ecosystems, whereas the total (15)N recovery was significantly lower in the subtropical forest ecosystem at DHS than in the boreal forest ecosystem at DXAL under the K(15)NO3 tracer treatment. The (15)N assimilated into the tree biomass represented only 8.8% to 33.7% of the (15)N added to the forest ecosystems. In both of the tracer application treatments, more (15)N was recovered from the tree biomass in the subtropical forest ecosystem at DHS than the boreal forest ecosystem at DXAL. The amount of (15)N assimilated into tree biomass was greater under the K(15)NO3 tracer treatment than that of the ((15)NH4)2SO4 treatment in both forest ecosystems. This study suggests that, although less N was immobilized in the forest ecosystems under more intensive N deposition conditions, forest ecosystems in China strongly retain N deposition, even in areas under heavy N deposition intensity or in ecosystems undergoing spring freezing and thawing melts. Compared to ammonium deposition, deposited nitrate is released from the forest ecosystem more easily. However, nitrate deposition could be retained mostly in the plant N pool, which might lead to more C sequestration in these ecosystems.

  9. Global Ecosystem Restoration Index

    DEFF Research Database (Denmark)

    Fernandez, Miguel; Garcia, Monica; Fernandez, Nestor

    2015-01-01

    The Global ecosystem restoration index (GERI) is a composite index that integrates structural and functional aspects of the ecosystem restoration process. These elements are evaluated through a window that looks into a baseline for degraded ecosystems with the objective to assess restoration...

  10. Carbon stock and carbon turnover in boreal and temperate forests - Integration of remote sensing data and global vegetation models

    Science.gov (United States)

    Thurner, Martin; Beer, Christian; Carvalhais, Nuno; Forkel, Matthias; Tito Rademacher, Tim; Santoro, Maurizio; Tum, Markus; Schmullius, Christiane

    2016-04-01

    Long-term vegetation dynamics are one of the key uncertainties of the carbon cycle. There are large differences in simulated vegetation carbon stocks and fluxes including productivity, respiration and carbon turnover between global vegetation models. Especially the implementation of climate-related mortality processes, for instance drought, fire, frost or insect effects, is often lacking or insufficient in current models and their importance at global scale is highly uncertain. These shortcomings have been due to the lack of spatially extensive information on vegetation carbon stocks, which cannot be provided by inventory data alone. Instead, we recently have been able to estimate northern boreal and temperate forest carbon stocks based on radar remote sensing data. Our spatially explicit product (0.01° resolution) shows strong agreement to inventory-based estimates at a regional scale and allows for a spatial evaluation of carbon stocks and dynamics simulated by global vegetation models. By combining this state-of-the-art biomass product and NPP datasets originating from remote sensing, we are able to study the relation between carbon turnover rate and a set of climate indices in northern boreal and temperate forests along spatial gradients. We observe an increasing turnover rate with colder winter temperatures and longer winters in boreal forests, suggesting frost damage and the trade-off between frost adaptation and growth being important mortality processes in this ecosystem. In contrast, turnover rate increases with climatic conditions favouring drought and insect outbreaks in temperate forests. Investigated global vegetation models from the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP), including HYBRID4, JeDi, JULES, LPJml, ORCHIDEE, SDGVM, and VISIT, are able to reproduce observation-based spatial climate - turnover rate relationships only to a limited extent. While most of the models compare relatively well in terms of NPP, simulated

  11. Retrieval of seasonal dynamics of forest understory reflectance from semi-arid to boreal forests using MODIS BRDF data

    Science.gov (United States)

    Pisek, Jan; Chen, Jing; Kobayashi, Hideki; Rautiainen, Miina; Schaepman, Michael; Karnieli, Arnon; Sprintsin, Michael; Ryu, Youngryel; Nikopensius, Maris; Raabe, Kairi

    2016-04-01

    Ground vegetation (understory) provides an essential contribution to the whole-stand reflectance signal in many boreal, sub-boreal, and temperate forests. Accurate knowledge about forest understory reflectance is urgently needed in various forest reflectance modelling efforts. However, systematic collections of understory reflectance data covering different sites and ecosystems are almost missing. Measurement of understory reflectance is a real challenge because of an extremely high variability of irradiance at the forest floor, weak signal in some parts of the spectrum, spectral separability issues of over- and understory and its variable nature. Understory can consist of several sub-layers (regenerated tree, shrub, grasses or dwarf shrub, mosses, lichens, litter, bare soil), it has spatially-temporally variable species composition and ground coverage. Additional challenges are introduced by patchiness of ground vegetation, ground surface roughness, and understory-overstory relations. Due to this variability, remote sensing might be the only means to provide consistent data at spatially relevant scales. In this presentation, we report on retrieving seasonal courses of understory Normalized Difference Vegetation Index (NDVI) from multi-angular MODIS BRDF/Albedo data. We compared satellite-based seasonal courses of understory NDVI against an extended collection of different types of forest sites with available in-situ understory reflectance measurements. These sites are distributed along a wide latitudinal gradient on the Northern hemisphere: a sparse and dense black spruce forests in Alaska and Canada, a northern European boreal forest in Finland, hemiboreal needleleaf and deciduous stands in Estonia, a mixed temperate forest in Switzerland, a cool temperate deciduous broadleaf forest in Korea, and a semi-arid pine plantation in Israel. Our results indicated the retrieval method performs well particularly over open forests of different types. We also demonstrated

  12. Do the energy fluxes and surface conductance of boreal coniferous forests in Europe scale with leaf area?

    Science.gov (United States)

    Launiainen, Samuli; Katul, Gabriel G; Kolari, Pasi; Lindroth, Anders; Lohila, Annalea; Aurela, Mika; Varlagin, Andrej; Grelle, Achim; Vesala, Timo

    2016-12-01

    Earth observing systems are now routinely used to infer leaf area index (LAI) given its significance in spatial aggregation of land surface fluxes. Whether LAI is an appropriate scaling parameter for daytime growing season energy budget, surface conductance (Gs ), water- and light-use efficiency and surface-atmosphere coupling of European boreal coniferous forests was explored using eddy-covariance (EC) energy and CO2 fluxes. The observed scaling relations were then explained using a biophysical multilayer soil-vegetation-atmosphere transfer model as well as by a bulk Gs representation. The LAI variations significantly alter radiation regime, within-canopy microclimate, sink/source distributions of CO2 , H2 O and heat, and forest floor fluxes. The contribution of forest floor to ecosystem-scale energy exchange is shown to decrease asymptotically with increased LAI, as expected. Compared with other energy budget components, dry-canopy evapotranspiration (ET) was reasonably 'conservative' over the studied LAI range 0.5-7.0 m(2) m(-2) . Both ET and Gs experienced a minimum in the LAI range 1-2 m(2) m(-2) caused by opposing nonproportional response of stomatally controlled transpiration and 'free' forest floor evaporation to changes in canopy density. The young forests had strongest coupling with the atmosphere while stomatal control of energy partitioning was strongest in relatively sparse (LAI ~2 m(2) m(-2) ) pine stands growing on mineral soils. The data analysis and model results suggest that LAI may be an effective scaling parameter for net radiation and its partitioning but only in sparse stands (LAI energy exchange. In denser forests, any LAI dependency varies with physiological traits such as light-saturated water-use efficiency. The results suggest that incorporating species traits and site conditions are necessary when LAI is used in upscaling energy exchanges of boreal coniferous forests.

  13. Radioactive caesium in Boreal forest landscapes - Dynamics and transport in food webs. Summary of research 1986-1996

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, R.; Nylen, T.; Palo, T

    1998-12-01

    The need for - but also the paucity of - radioecological knowledge concerning the boreal forest became particularly apparent after the nuclear power plant accident in Chernobyl in April 1986. As a consequence several new projects were initiated in the Nordic countries with particular focus on the behaviour of radioactivecaesium in terrestrial and aquatic systems characteristic for the Fenno-Scandinavian landscapes. Among these new projects a multi-disciplinary co-operation in Umeaa between scientists at the Swedish University of Agricultural Sciences, and the Defence Research Establishment emerged. Initially this joint work focused mainly on descriptions of the dynamic changes of the content of radioactive caesium in soil-plant and animal communities in the county of Vaesterbotten. Most of the studies have been performed at the Vindeln experimental forest, 60 km NW of Umeaa. Plants of key interest were: bilberry (Vaccinium myrtillus), birch (Betula spp.), and pine (Pinus sylvestris), and among the animals: the moose (Alces alces) and a small rodent, the forest vole (Clethrionomus glareolus). Gradually over the past ten years the research has entered the stage where the specific causes of the caesium behaviour have been addressed - partly by the help of models developed for simulating forest ecosystems, partly by complementary field experiments. This paper reviews our main findings on this theme concerning the behaviour of radioactive caesium in boreal landscapes and significant pathways to man, as has become apparent from the radioecological co-operation dating from about ten years back. A list of the publications arising from these studies since 1986 is also presented in this report.

  14. Climate sensitivity of reproduction in a mast-seeding boreal conifer across its distributional range from lowland to treeline forests.

    Science.gov (United States)

    Roland, Carl A; Schmidt, Joshua H; Johnstone, Jill F

    2014-03-01

    Mast-seeding conifers such as Picea glauca exhibit synchronous production of large seed crops over wide areas, suggesting climate factors as possible triggers for episodic high seed production. Rapidly changing climatic conditions may thus alter the tempo and spatial pattern of masting of dominant species with potentially far-reaching ecological consequences. Understanding the future reproductive dynamics of ecosystems including boreal forests, which may be dominated by mast-seeding species, requires identifying the specific cues that drive variation in reproductive output across landscape gradients and among years. Here we used annual data collected at three sites spanning an elevation gradient in interior Alaska, USA between 1986 and 2011 to produce the first quantitative models for climate controls over both seedfall and seed viability in P. glauca, a dominant boreal conifer. We identified positive associations between seedfall and increased summer precipitation and decreased summer warmth in all years except for the year prior to seedfall. Seed viability showed a contrasting response, with positive correlations to summer warmth in all years analyzed except for one, and an especially positive response to warm and wet conditions in the seedfall year. Finally, we found substantial reductions in reproductive potential of P. glauca at high elevation due to significantly reduced seed viability there. Our results indicate that major variation in the reproductive potential of this species may occur in different landscape positions in response to warming, with decreasing reproductive success in areas prone to drought stress contrasted with increasing success in higher elevation areas currently limited by cool summer temperatures.

  15. National recovery strategy for woodland caribou (Rangifer tarandus caribou, boreal population, in Canada

    Directory of Open Access Journals (Sweden)

    Dave Hervieux

    2007-04-01

    Full Text Available Recovery planning for the boreal population of woodland caribou is a complex task, spanning eight Canadian provinces and territories. To accommodate unique situations across the country, recovery planning for this Species at Risk Act-listed threatened species is occurring at both provincial/ territorial and national levels. The national recovery strategy strives to identify nationally important issues and provide direction for provinces and territories as they plan and implement boreal caribou recovery within their jurisdictions. The national vision is to conserve and recover boreal caribou and their habitat across Canada. Specific goals are to: 1 Prevent extirpation of local boreal caribou populations from all existing caribou ranges; and 2 Maintain or enhance local boreal caribou populations at or to self-sustaining levels within all existing caribou ranges; and 3 Maintain or enhance boreal caribou habitat to support self-sustaining local populations. Nineteen broad national approaches are identified. These approaches include items relating to: habitat planning and management, caribou population monitoring and management, management of human-caused mortality, management of other wildlife species, consideration of government legislation and policy,promotion of stewardship and public outreach, and research. Specific outcomes are provided for each stated recovery approach. For more information on Canada's national recovery strategy for the boreal population of woodland caribou please see www.speciesatrisk.gc.ca/recovery/default_e.cfm

  16. Wood phenology: from organ-scale processes to terrestrial ecosystem models

    Science.gov (United States)

    Delpierre, Nicolas; Guillemot, Joannès

    2016-04-01

    In temperate and boreal trees, a dormancy period prevents organ development during adverse climatic conditions. Whereas the phenology of leaves and flowers has received considerable attention, to date, little is known regarding the phenology of other tree organs such as wood, fine roots, fruits and reserve compounds. In this presentation, we review both the role of environmental drivers in determining the phenology of wood and the models used to predict its phenology in temperate and boreal forest trees. Temperature is a key driver of the resumption of wood activity in spring. There is no such clear dominant environmental cue involved in the cessation of wood formation in autumn, but temperature and water stress appear as prominent factors. We show that wood phenology is a key driver of the interannual variability of wood growth in temperate tree species. Incorporating representations of wood phenology in a terrestrial ecosystem model substantially improved the simulation of wood growth under current climate.

  17. Seventeen-year trends in spring and autumn phenophases of Betula pubescens in a boreal environment

    Science.gov (United States)

    Poikolainen, Jarmo; Tolvanen, Anne; Karhu, Jouni; Kubin, Eero

    2016-08-01

    Trends in the timing of spring and autumn phenophases of Betula pubescens were investigated in the southern, middle, and northern boreal zones in Finland. The field observations were carried out at 21 sites in the Finnish National Phenological Network in 1997-2013. The effective temperature sum of the thermal growth period, i.e. the sum of the positive differences between diurnal mean temperatures and 5 °C (ETS1), increased annually on average by 6-7 degree day units. Timing of bud burst remained constant in the southern and middle boreal zones but advanced annually by 0.5 day in the northern boreal zone. The effective temperature sum at bud burst (ETS2) showed no trend in the southern and middle boreal zones, whereas ETS2 increased on average from 20-30 to 50 degree day units in the northern boreal zone, almost to the same level as in the other zones. Increase in ETS2 indicates that the trees did not start their growth in very early spring despite warmer spring temperatures. The timing of leaf colouring and leaf fall remained almost constant in the southern boreal zones, whereas these advanced annually by 0.3 and 0.6 day in the middle boreal zone and by 0.6 and 0.4 day in the northern boreal zone, respectively. The duration of the growth period remained constant in all boreal zones. The results indicate high buffering capacity of B. pubescens against temperature changes. The study also shows the importance of the duration of phenological studies: some trends in spring phenophases had levelled out, while new trends in autumn phases had emerged after earlier studies in the same network for a shorter observation period.

  18. Decreases in Soil Moisture and Organic Matter Quality Suppress Microbial Decomposition Following a Boreal Forest Fire

    Energy Technology Data Exchange (ETDEWEB)

    Holden, Sandra R.; Berhe, Asmeret A.; Treseder, Kathleen K.

    2015-08-01

    Climate warming is projected to increase the frequency and severity of wildfires in boreal forests, and increased wildfire activity may alter the large soil carbon (C) stocks in boreal forests. Changes in boreal soil C stocks that result from increased wildfire activity will be regulated in part by the response of microbial decomposition to fire, but post-fire changes in microbial decomposition are poorly understood. Here, we investigate the response of microbial decomposition to a boreal forest fire in interior Alaska and test the mechanisms that control post-fire changes in microbial decomposition. We used a reciprocal transplant between a recently burned boreal forest stand and a late successional boreal forest stand to test how post-fire changes in abiotic conditions, soil organic matter (SOM) composition, and soil microbial communities influence microbial decomposition. We found that SOM decomposing at the burned site lost 30.9% less mass over two years than SOM decomposing at the unburned site, indicating that post-fire changes in abiotic conditions suppress microbial decomposition. Our results suggest that moisture availability is one abiotic factor that constrains microbial decomposition in recently burned forests. In addition, we observed that burned SOM decomposed more slowly than unburned SOM, but the exact nature of SOM changes in the recently burned stand are unclear. Finally, we found no evidence that post-fire changes in soil microbial community composition significantly affect decomposition. Taken together, our study has demonstrated that boreal forest fires can suppress microbial decomposition due to post-fire changes in abiotic factors and the composition of SOM. Models that predict the consequences of increased wildfires for C storage in boreal forests may increase their predictive power by incorporating the observed negative response of microbial decomposition to boreal wildfires.

  19. Ecosystem services in ECOCLIM

    DEFF Research Database (Denmark)

    Sørensen, Lise Lotte; Boegh, Eva; Bendtsen, J;

    that actions initiated to reduce anthropogenic GHG emissions are sustainable and not destructive to existing ecosystem services. Therefore it is important to address i.e. land use change in relation to the regulating services of the ecosystems, such as carbon sequestration and climate regulation. At present...... a thorough understanding of the ecosystem processes controlling the uptake or emissions of GHG is fundamental. Here we present ECOCLIM in the context of ecosystem services and the experimental studies within ECOCLIM which will lead to an enhanced understanding of Danish ecosystems....

  20. Effect of inorganic N enrichment on basal pelagic production in boreal unproductive lakes along a gradient of DOC concentration - results after 1 year of fertilization

    Science.gov (United States)

    Deininger, Anne; Bergström, Ann-Kristin

    2013-04-01

    Input of inorganic nitrogen (N) in boreal unproductive lakes is steadily increasing due to anthropogenic deposition and usage of artificial fertilizers. N enrichment is predicted to have a major impact on the ecosystem productivity and food web structure in unproductive clear-water and humic lakes. For a long time, pelagic primary production (PP) has been mainly regarded as being phosphorus (P) limited. However, recent studies have shown that this is not true for unproductive lakes in northern Sweden, where phytoplankton is mainly N limited. Addition of inorganic N should therefore increase phytoplankton growth in these lake ecosystems. Bacterial production (BP) in the pelagic habitat, on the other hand, is usually limited by P. Nevertheless, elevated N could have a stimulating effect on BP through enhanced leakage of dissolved organic carbon (DOC) from phytoplankton following enhanced N availability and higher PP. Further, unproductive lakes vary naturally in their DOC content which affects overall nutrient- (N and P), energy- and carbon availability (light, C) for the basal producers (phytoplankton, bacteria). It is still not clear how higher inorganic N availability affects primary- and bacterial production in the pelagic in lakes with varying DOC content. We subsequently assessed this question by conducting whole-lake fertilization experiments with inorganic N additions in 6 lakes with varying DOC concentrations (2 low DOC; 2 medium DOC; 2 high DOC). For each DOC level one lake functioned as a reference and one was fertilized with N. Year 2011 was a reference year (all lakes) and 2012 was the first year of fertilization (i.e. in 3 lakes). Measurements included basal productivity such as primary production and bacteria production, lake water chemistry and physical parameters (i.e. light, temperature). The results of this study will help to develop a conceptual understanding of how increased inorganic N availability (through land use such as forestry and

  1. Fishing for ecosystem services

    Science.gov (United States)

    Pope, Kevin L.; Pegg, Mark A.; Cole, Nicholas W.; Siddons, Stephen F.; Fedele, Alexis D.; Harmon, Brian S.; Ruskamp, Ryan L.; Turner, Dylan R.; Uerling, Caleb C.

    2016-01-01

    Ecosystems are commonly exploited and manipulated to maximize certain human benefits. Such changes can degrade systems, leading to cascading negative effects that may be initially undetected, yet ultimately result in a reduction, or complete loss, of certain valuable ecosystem services. Ecosystem-based management is intended to maintain ecosystem quality and minimize the risk of irreversible change to natural assemblages of species and to ecosystem processes while obtaining and maintaining long-term socioeconomic benefits. We discuss policy decisions in fishery management related to commonly manipulated environments with a focus on influences to ecosystem services. By focusing on broader scales, managing for ecosystem services, and taking a more proactive approach, we expect sustainable, quality fisheries that are resilient to future disturbances. To that end, we contend that: (1) management always involves tradeoffs; (2) explicit management of fisheries for ecosystem services could facilitate a transition from reactive to proactive management; and (3) adaptive co-management is a process that could enhance management for ecosystem services. We propose adaptive co-management with an ecosystem service framework where actions are implemented within ecosystem boundaries, rather than political boundaries, through strong interjurisdictional relationships.

  2. Columbia River Estuary Ecosystem Classification Ecosystem Complex

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Estuarine ecosystems are controlled by a variety of processes that operate at multiple spatial and temporal scales. Understanding the hierarchical nature of these...

  3. Modeling micro-topographic controls on boreal peatland hydrology and methane fluxes

    Directory of Open Access Journals (Sweden)

    F. Cresto Aleina

    2015-07-01

    Full Text Available Small-scale surface heterogeneities can influence land–atmosphere fluxes and therefore carbon, water and energy budgets on larger scale. This effect is of particular relevance for high-latitude ecosystems, because of the great amount of carbon stored in their soils. We introduce a novel micro-topographic model, the Hummock–Hollow (HH model, which explicitly represents small-scale surface elevation changes. By computing the water table at the small scale, and by coupling the model with a process-based model for soil methane processes, we are able to model effects of micro-topography on hydrology and methane emissions in a typical boreal peatland. In order to assess the effect of micro-topography on water balance and methane emissions of the peatland we compare two versions of the model, one with a representation of micro-topography and a classical single-bucket model version, and show that the temporal variability in the model version with micro-topography performs better if compared with local data. Accounting for micro-topography almost triples the cumulative methane flux over the simulated time-slice. We found that the single-bucket model underestimates methane emissions because of its poor performance in representing hydrological dynamics. The HH model with micro-topography captures the spatial dynamics of water and methane fluxes, being able to identify the hotspots for methane emissions. The model also identifies a critical scale (0.01 km2 which marks the minimal resolution for the explicit representation of micro-topography in larger-scale models.

  4. Organic matter mineralization in frozen boreal soils-environmental constraints on catabolic and anabolic microbial activity

    Science.gov (United States)

    Oquist, Mats G.; Sparrman, Tobias; Schleucher, Jürgen; Nilsson, Mats B.

    2014-05-01

    Heterotrophic microbial mineralization of soil organic matter (SOM) and associated production and emission of atmospheric trace gases proceed during the winter months in the frozen soils of high latitude ecosystems. However, in what ways this microbial activity is constrained by the environmental conditions prevailing in a frozen soil matrix is uncertain. This presentation will address how temperature, water availability and substrate availability combine to regulate rates of microbial activity at below freezing temperatures and the implications of this activity for SOM mineralization in the surface layers of boreal forest soils experiencing seasonal freezing. We show that the amount and availability of liquid water is an integral factor regulating rates of microbial activity in the frozen soil matrix and can also explain frequently observed deviations in the temperature responses of biogenic CO2 production in frozen soils, as compared to unfrozen soils. Using stable isotope labeling (13C) we also show that the partitioning of substrate carbon, in the form of monomeric sugar (glucose), for catabolic and anabolic metabolism remain constant in the temperature range of -4C to 9C. This confirms that microbial growth may proceed even when soils are frozen. In addition we present corresponding data for organisms metabolizing polymeric substrates (cellulose) requiring exoenzymatic activity prior to substrate uptake. We conclude that the metabolic response of soil microorganism to controlling factors may change substantially across the freezing point of soil water, and also the patterns of interaction among controlling factors are affected. Thus, it is evident that metabolic response functions derived from investigations of unfrozen soils cannot be superimposed on frozen soils. Nonetheless, the soil microbial population appear very adapted to seasonal freezing with respect to their metabolic performance.

  5. Soil carbon stock increases in the organic layer of boreal middle-aged stands

    Science.gov (United States)

    Häkkinen, M.; Heikkinen, J.; Mäkipää, R.

    2011-05-01

    Changes in the soil carbon stock can potentially have a large influence on global carbon balance between terrestrial ecosystems and atmosphere. Since carbon sequestration of forest soils is influenced by human activities, reporting of the soil carbon pool is a compulsory part of the national greenhouse gas (GHG) inventories. Various soil carbon models are applied in GHG inventories, however, the verification of model-based estimates is lacking. In general, the soil carbon models predict accumulation of soil carbon in the middle-aged stands, which is in good agreement with chronosequence studies and flux measurements of eddy sites, but they have not been widely tested with repeated measurements of permanent plots. The objective of this study was to evaluate soil carbon changes in the organic layer of boreal middle-aged forest stands. Soil carbon changes on re-measured sites were analyzed by using soil survey data that was based on composite samples as a first measurement and by taking into account spatial variation on the basis of the second measurement. By utilizing earlier soil surveys, a long sampling interval, which helps detection of slow changes, could be readily available. The range of measured change in the soil organic layer varied from -260 to 1260 g m-2 over the study period of 16-19 years and 23 ± 2 g m-2 per year, on average. The increase was significant in 6 out of the 38 plots from which data were available. Although the soil carbon change was difficult to detect at the plot scale, the overall increase measured across the middle-aged stands agrees with predictions of the commonly applied soil models. Further verification of the soil models is needed with larger datasets that cover wider geographical area and represent all age classes, especially young stands with potentially large soil carbon source.

  6. Soil carbon stock increases in the organic layer of boreal middle-aged stands

    Directory of Open Access Journals (Sweden)

    M. Häkkinen

    2011-05-01

    Full Text Available Changes in the soil carbon stock can potentially have a large influence on global carbon balance between terrestrial ecosystems and atmosphere. Since carbon sequestration of forest soils is influenced by human activities, reporting of the soil carbon pool is a compulsory part of the national greenhouse gas (GHG inventories. Various soil carbon models are applied in GHG inventories, however, the verification of model-based estimates is lacking. In general, the soil carbon models predict accumulation of soil carbon in the middle-aged stands, which is in good agreement with chronosequence studies and flux measurements of eddy sites, but they have not been widely tested with repeated measurements of permanent plots. The objective of this study was to evaluate soil carbon changes in the organic layer of boreal middle-aged forest stands. Soil carbon changes on re-measured sites were analyzed by using soil survey data that was based on composite samples as a first measurement and by taking into account spatial variation on the basis of the second measurement. By utilizing earlier soil surveys, a long sampling interval, which helps detection of slow changes, could be readily available.

    The range of measured change in the soil organic layer varied from −260 to 1260 g m−2 over the study period of 16–19 years and 23 ± 2 g m−2 per year, on average. The increase was significant in 6 out of the 38 plots from which data were available. Although the soil carbon change was difficult to detect at the plot scale, the overall increase measured across the middle-aged stands agrees with predictions of the commonly applied soil models. Further verification of the soil models is needed with larger datasets that cover wider geographical area and represent all age classes, especially young stands with potentially large soil carbon source.

  7. Soil carbon stock increases in the organic layer of boreal middle-aged stands

    Directory of Open Access Journals (Sweden)

    M. Häkkinen

    2011-02-01

    Full Text Available Changes in the soil carbon stock can potentially have a large influence on global carbon balance between terrestrial ecosystems and atmosphere. Since carbon sequestration of forest soils is influenced by human activities, reporting of the soil carbon pool is a compulsory part of the national greenhouse gas (GHG inventories. Various soil carbon models are applied in GHG inventories, however, the verification of model-based estimates is lacking. In general, the soil carbon models predict accumulation of soil carbon in the middle-aged stands, which is in good agreement with chronosequence studies and flux measurements of eddy sites, but they have not been widely tested with repeated measurements of permanent plots. The objective of this study was to evaluate soil carbon changes in the organic layer of boreal middle-aged forest stands. Soil carbon changes on re-measured sites were analyzed by using soil survey data that was based on composite samples as a first measurement and by taking into account spatial variation on the basis of the second measurement. By utilizing earlier soil surveys, a long sampling interval, which helps detection of slow changes, could be readily available.

    The range of measured change in the soil organic layer varied from −260 to 1260 g m−2 over the study period of 16–19 years and 23 ± 2 g m−2 per year, on average. The increase was significant in 6 out of the 38 plots from which data were available. Although the soil carbon change was difficult to detect at the plot scale, the overall increase measured across the middle-aged stands agrees with predictions of the commonly applied soil models. Further verification of the soil models is needed with larger datasets that cover wider geographical area and represent all age classes, especially young stands with potentially large soil carbon source.

  8. Mapping Above- and Below-Ground Carbon Pools in Boreal Forests: The Case for Airborne Lidar.

    Science.gov (United States)

    Kristensen, Terje; Næsset, Erik; Ohlson, Mikael; Bolstad, Paul V; Kolka, Randall

    2015-01-01

    A large and growing body of evidence has demonstrated that airborne scanning light detection and ranging (lidar) systems can be an effective tool in measuring and monitoring above-ground forest tree biomass. However, the potential of lidar as an all-round tool for assisting in assessment of carbon (C) stocks in soil and non-tree vegetation components of the forest ecosystem has been given much less attention. Here we combine the use airborne small footprint scanning lidar with fine-scale spatial C data relating to vegetation and the soil surface to describe and contrast the size and spatial distribution of C pools within and among multilayered Norway spruce (Picea abies) stands. Predictor variables from lidar derived metrics delivered precise models of above- and below-ground tree C, which comprised the largest C pool in our study stands. We also found evidence that lidar canopy data correlated well with the variation in field layer C stock, consisting mainly of ericaceous dwarf shrubs and herbaceous plants. However, lidar metrics derived directly from understory echoes did not yield significant models. Furthermore, our results indicate that the variation in both the mosses and soil organic layer C stock plots appears less influenced by differences in stand structure properties than topographical gradients. By using topographical models from lidar ground returns we were able to establish a strong correlation between lidar data and the organic layer C stock at a stand level. Increasing the topographical resolution from plot averages (~2000 m2) towards individual grid cells (1 m2) did not yield consistent models. Our study demonstrates a connection between the size and distribution of different forest C pools and models derived from airborne lidar data, providing a foundation for future research concerning the use of lidar for assessing and monitoring boreal forest C.

  9. Unusual forest growth decline in boreal North America covaries with the retreat of Arctic sea ice.

    Science.gov (United States)

    Girardin, Martin P; Guo, Xiao Jing; De Jong, Rogier; Kinnard, Christophe; Bernier, Pierre; Raulier, Frédéric

    2014-03-01

    The 20th century was a pivotal period at high northern latitudes as it marked the onset of rapid climatic warming brought on by major anthropogenic changes in global atmospheric composition. In parallel, Arctic sea ice extent has been decreasing over the period of available satellite data records. Here, we document how these changes influenced vegetation productivity in adjacent eastern boreal North America. To do this, we used normalized difference vegetation index (NDVI) data, model simulations of net primary productivity (NPP) and tree-ring width measurements covering the last 300 years. Climatic and proxy-climatic data sets were used to explore the relationships between vegetation productivity and Arctic sea ice concentration and extent, and temperatures. Results indicate that an unusually large number of black spruce (Picea mariana) trees entered into a period of growth decline during the late-20th century (62% of sampled trees; n = 724 cross sections of age >70 years). This finding is coherent with evidence encoded in NDVI and simulated NPP data. Analyses of climatic and vegetation productivity relationships indicate that the influence of recent climatic changes in the studied forests has been via the enhanced moisture stress (i.e. greater water demands) and autotrophic respiration amplified by the declining sea ice concentration in Hudson Bay and Hudson Strait. The recent decline strongly contrasts with other growth reduction events that occurred during the 19th century, which were associated with cooling and high sea ice severity. The recent decline of vegetation productivity is the first one to occur under circumstances related to excess heat in a 300-year period, and further culminates with an intensifying wildfire regime in the region. Our results concur with observations from other forest ecosystems about intensifying temperature-driven drought stress and tree mortality with ongoing climatic changes.

  10. Temperature and moisture effects on greenhouse gas emissions from deep active-layer boreal soils

    Energy Technology Data Exchange (ETDEWEB)

    Bond-Lamberty, Benjamin; Smith, Ashly P.; Bailey, Vanessa L.

    2016-12-21

    Rapid climatic changes, rising air temperatures, and increased fires are expected to drive permafrost degradation and alter soil carbon (C) cycling in many high-latitude ecosystems. How these soils will respond to changes in their temperature, moisture, and overlying vegetation is highly uncertain, but critical to understand given the large soil C stocks in these regions. We used a laboratory experiment to examine how temperature and moisture control CO2 and CH4 emissions from mineral soils sampled from the bottom of the annual active layer, i.e. directly above permafrost, in an Alaskan boreal forest. Gas emissions from thirty cores, subjected to two temperatures and either field moisture conditions or experimental drought, were tracked over a 100-day incubation; we also measured a variety of physical and chemical characteristics of the cores. Gravimetric water content was 0.31 ± 0.12 (unitless) at the beginning of the incubation; cores at field moisture were unchanged at the end, but drought cores had declined to 0.06 ± 0.04. Carbon dioxide fluxes were strongly influenced by incubation chamber temperature, core water content, and percent soil nitrogen, and had a temperature sensitivity (i.e. Q10) of 1.3 and 1.9 for the field moisture and drought treatments, respectively. Methane emissions were most strongly correlated with percent nitrogen, but neither temperature nor water content was a significant first-order predictor of CH4 fluxes. The cumulative production of C from CO2 was over six orders of magnitudes higher than that from CH4. These results suggest that deep active-layer soils may be much more sensitive to changes in moisture than to temperature, a critical factor as discontinuous permafrost melts in interior Alaska. Deep but unfrozen high-latitude soils have been shown to be strongly affected by long-term experimental warming, and these results provide insight into their future dynamics and feedback potential with future climate change.

  11. Hydrological and thermal controls of ice formation in 25 boreal stream reaches

    Science.gov (United States)

    Lind, Lovisa; Alfredsen, Knut; Kuglerová, Lenka; Nilsson, Christer

    2016-09-01

    The Northern Hemisphere has a high density of fluvial freshwater ecosystems, many of which become ice-covered during winter. The development and extent of ice have both ecological and socio-economic implications. For example, ice can cause freezing of riparian vegetation and fish eggs as well as influence hydropower production; however, when, where and why ice develops in small streams is not well known. We used observations from 25 stream reaches to study the factors controlling ice development during two consecutive winters, addressing where in the catchment surface or anchor-ice is most likely to develop, how stream morphology influences ice formation, and how climate influences ice processes. Reaches far downstream from lake outlets, or without any upstream lakes, were most prone to develop anchor-ice, but other factors also influenced ice formation. Anchor-ice was most common where water temperature and groundwater inputs were low and stream power high. Given cold air temperature and water supercooling, the in-stream substrate as well as the current velocity were also important for the development of anchor-ice. Climate and substrate seemed to be important factors for the development of surface ice. This study shows that ice processes are substantial during the hydrological year and may therefore have large implications for the ecology and engineering around boreal streams. The study also demonstrates that ice formation in the studied streams was complex, involving many variables and physical processes. We constructed a conceptual model describing the likelihood for various ice types to develop, based on the large dataset. As such, this model will be useful for practitioners and scientists working in small watercourses in the Northern Hemisphere.

  12. Effect of Forest Fire on Regional Carbon Dioxide Exchange Over Boreal Forest in Interior Alaska

    Science.gov (United States)

    Iwata, H.; Otsuki, M.; Harazono, Y.; Ueyama, M.; Iwata, T.

    2010-12-01

    Forest fire is a major disturbance in boreal forest ecosystems and significantly influences carbon exchange processes by combustion of vegetation and surface organic soils. In Interior Alaska, area of 7.6x106 ha was burned during 2000-2009 by forest fires. Fire occurrence frequency in the next decade may increase with current warming trend. Hence, it is important to include carbon dioxide (CO2) exchange at fire scars to accurately estimate regional CO2 exchange. To quantify CO2 exchange, CO2 flux and meteorological data were obtained at an undisturbed black spruce forest and a fire scar (five years after fire) in Interior Alaska, and responses of photosynthesis and respiration to meteorological variables were examined in each site. Photosynthesis at the fire scar was reduced to approximately 50 % of photosynthesis at the undisturbed black spruce forest due to loss of vegetation. Respiration at the fire scar was also reduced to 50 % of the undisturbed black spruce forest. This is attributable to decrease of biomass and surface organic matter. Annual net exchanges of CO2 at both sites were uptake of 519 and 256 gCO2/m2/year for the undisturbed black spruce forest and the fire scar, respectively. We used light-use efficiency model to estimate spatial distributions of photosynthesis and respiration using remote sensing imagery, NCEP/NCAR reanalysis meteorology and NASA solar radiation. The model was parameterized using observations at the undisturbed black spruce forest and the fire scar. Estimated regional average of CO2 uptake was reduced by 10 % compared to an estimated value with which fire scars were not included. Further improvement is expected by incorporating severity of forest fires that determine reduction of photosynthesis and respiration after fires.

  13. No increase in colonization rate of boreal bryophytes close to propagule sources.

    Science.gov (United States)

    Hylander, Kristoffer

    2009-01-01

    Knowledge of the process of recolonization, and which temporal and spatial scale it operates on, is central to our understanding of species distributions, metapopulation dynamics, regional extinction risks, and ecosystem resilience. In this study the recolonization pattern of boreal forest bryophytes was investigated in stands that had been clear-cut approximately 50 years ago. Species known to be sensitive to clear-cutting were inventoried in 23 mature forest stands and in adjacent young stands at 10, 20, 40, and 80 m from the former forest-clear-cut edge. Based on previous studies showing that bryophytes tend to be dispersal limited at local population levels, it was hypothesized that the recolonizaton of many bryophyte species should be higher closer to the mature forest edge. It was also hypothesized that some species would show full recovery, while for others the young stands would still be inhospitable. All these patterns were found for individual species, but the main pattern was, however, quite different. Most species had started to recolonize the young stands (i.e., little or much, depending on species), but without any tendency of a higher colonization rate close to the mature stands. Possible explanations for the limited signs of positive influence of local propagule sources might be microsite limitation or that the local propagule availability displays a rapid decline from its sources and is masked by a higher regional propagule rain. For organisms with light propagules able to build up a regional background level, the role of mature forest stands in the recolonization process of the matrix may rather be to contribute to the regional background level of spores in the landscape than to affect the adjacent stands directly.

  14. Modelling Temporal Variability in the Carbon Balance of a Spruce/Moss Boreal Forest

    Science.gov (United States)

    Frolking, S.; Goulden, M. L.; Wofsy, S. C.; Fan, S.-M.; Sutton, D. J.; Munger, J. W.; Bazzaz, A. M.; Daube, B. C.; Crill, P. M.; Aber, J. D.; Band, L. E.; Wang, X.; Savages, K.; Moore, T.; Harriss, R. C.

    1996-01-01

    A model of the daily carbon balance of a black spruce/feathermoss boreal forest ecosystem was developed and results compared to preliminary data from the 1994 BOREAS field campaign in northern Manitoba, Canada. The model, driven by daily weather conditions, simulated daily soil climate status (temperature and moisture profiles), spruce photosynthesis and respiration, moss photosynthesis and respiration, and litter decomposition. Model agreement with preliminary field data was good for net ecosystem exchange (NEE), capturing both the asymmetrical seasonality and short-term variability. During the growing season simulated daily NEE ranged from -4 g C m(exp -2) d(exp -1) (carbon uptake by ecosystem) to + 2 g C m(exp -2) d(exp -1) (carbon flux to atmosphere), with fluctuations from day to day. In the early winter simulated NEE values were + 0.5 g C m(exp -2) d(exp -1), dropping to + 0.2 g C m(exp -2) d(exp -1) in mid-winter. Simulated soil respiration during the growing season (+ 1 to + 5 g C m(exp -2) d(exp -1)) was dominated by metabolic respiration of the live moss, with litter decomposition usually contributing less than 30% and live spruce root respiration less than 10% of the total. Both spruce and moss net primary productivity (NPP) rates were higher in early summer than late summer. Simulated annual NEE for 1994 was -51 g C m(exp -2) y(exp -1), with 83% going into tree growth and 17% into the soil carbon accumulation. Moss NPP (58 g C m(exp -2) d(exp -1)) was considered to be litter (i.e. soil carbon input; no net increase in live moss biomass). Ecosystem respiration during the snow-covered season (84 g Cm(exp -2)) was 58% of the growing season net carbon uptake. A simulation of the same site for 1968-1989 showed about 10-20% year-to-year variability in heterotrophic respiration (mean of + 113 g C m-2 y@1). Moss NPP ranged from 19 to 114 g C m(exp -2) y(exp -1); spruce NPP from 81 to 150 g C nt-2 y,@l; spruce growth (NPP minus litterfall) from 34 to 103 g C m

  15. Attenuation of rare earth elements in a boreal estuary

    Science.gov (United States)

    Åström, Mats E.; Österholm, Peter; Gustafsson, Jon Petter; Nystrand, Miriam; Peltola, Pasi; Nordmyr, Linda; Boman, Anton

    2012-11-01

    This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (<0.45 μm) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations.

  16. Regional boreal biodiversity peaks at intermediate human disturbance.

    Science.gov (United States)

    Mayor, S J; Cahill, J F; He, F; Sólymos, P; Boutin, S

    2012-01-01

    The worldwide biodiversity crisis has intensified the need to better understand how biodiversity and human disturbance are related. The 'intermediate disturbance hypothesis' suggests that disturbance regimes generate predictable non-linear patterns in species richness. Evidence often contradicts intermediate disturbance hypothesis at small scales, and is generally lacking at large regional scales. Here, we present the largest extent study of human impacts on boreal plant biodiversity to date. Disturbance extent ranged from 0 to 100% disturbed in vascular plant communities, varying from intact forest to agricultural fields, forestry cut blocks and oil sands. We show for the first time that across a broad region species richness peaked in communities with intermediate anthropogenic disturbance, as predicted by intermediate disturbance hypothesis, even when accounting for many environmental covariates. Intermediate disturbance hypothesis was consistently supported across trees, shrubs, forbs and grasses, with temporary and perpetual disturbances. However, only native species fit this pattern; exotic species richness increased linearly with disturbance.

  17. Boreal fire records in Northern Hemisphere ice cores: a review

    Science.gov (United States)

    Legrand, Michel; McConnell, Joseph; Fischer, Hubertus; Wolff, Eric W.; Preunkert, Susanne; Arienzo, Monica; Chellman, Nathan; Leuenberger, Daiana; Maselli, Olivia; Place, Philip; Sigl, Michael; Schüpbach, Simon; Flannigan, Mike

    2016-10-01

    Here, we review different attempts made since the early 1990s to reconstruct past forest fire activity using chemical signals recorded in ice cores extracted from the Greenland ice sheet and a few mid-northern latitude, high-elevation glaciers. We first examined the quality of various inorganic (ammonium, nitrate, potassium) and organic (black carbon, various organic carbon compounds including levoglucosan and numerous carboxylic acids) species proposed as fire proxies in ice, particularly in Greenland. We discuss limitations in their use during recent vs. pre-industrial times, atmospheric lifetimes, and the relative importance of other non-biomass-burning sources. Different high-resolution records from several Greenland drill sites and covering various timescales, including the last century and Holocene, are discussed. We explore the extent to which atmospheric transport can modulate the record of boreal fires from Canada as recorded in Greenland ice. Ammonium, organic fractions (black and organic carbon), and specific organic compounds such as formate and vanillic acid are found to be good proxies for tracing past boreal fires in Greenland ice. We show that use of other species - potassium, nitrate, and carboxylates (except formate) - is complicated by either post-depositional effects or existence of large non-biomass-burning sources. The quality of levoglucosan with respect to other proxies is not addressed here because of a lack of high-resolution profiles for this species, preventing a fair comparison. Several Greenland ice records of ammonium consistently indicate changing fire activity in Canada in response to past climatic conditions that occurred during the last millennium and since the last large climatic transition. Based on this review, we make recommendations for further study to increase reliability of the reconstructed history of forest fires occurring in a given region.

  18. Decadal change in the boreal summer intraseasonal oscillation

    Science.gov (United States)

    Yamaura, Tsuyoshi; Kajikawa, Yoshiyuki

    2016-06-01

    A decadal change in activity of the boreal summer intraseasonal oscillation (BSISO) was identified at a broad scale. The change was more prominent during August-October in the boreal summer. The BSISO activity during 1999-2008 (P2) was significantly greater than that during 1984-1998 (P1). Compared to P1, convection in the BSISO was enhanced and the phase speed of northward-propagating convection was reduced in P2. Under background conditions, warm sea surface temperature (SST) anomalies in P2 were apparent over the tropical Indian Ocean and the western tropical Pacific. The former supplied favorable conditions for the active convection of the BSISO, whereas the latter led to a strengthened Walker circulation through enhanced convection. This induced descending anomalies over the tropical Indian Ocean. Thermal convection tends to be suppressed by descending anomalies, whereas once an active BSISO signal enters the Indian Ocean, convection is enhanced through convective instability by positive SST anomalies. After P2, the BSISO activity was weakened during 2009-2014 (P3). Compared to P2, convective activity in the BSISO tended to be inactive over the southern tropical Indian Ocean in P3. The phase speed of the northward-propagating convection was accelerated. Under background conditions during P3, warmer SST anomalies over the maritime continent enhance convection, which strengthened the local Hadley circulation between the western tropical Pacific and the southern tropical Indian Ocean. Hence, the convection in the BSISO over the southern tropical Indian Ocean was suppressed. The decadal change in BSISO activity correlates with the variability in seasonal mean SST over the tropical Asian monsoon region, which suggests that it is possible to predict the decadal change.

  19. Forest productivity decline caused by successional paludification of boreal soils.

    Science.gov (United States)

    Simard, Martin; Lecomte, Nicolas; Bergeron, Yves; Bernier, Pierre Y; Paré, David

    2007-09-01

    Long-term forest productivity decline in boreal forests has been extensively studied in the last decades, yet its causes are still unclear. Soil conditions associated with soil organic matter accumulation are thought to be responsible for site productivity decline. The objectives of this study were to determine if paludification of boreal soils resulted in reduced forest productivity, and to identify changes in the physical and chemical properties of soils associated with reduction in productivity. We used a chronosequence of 23 black spruce stands ranging in postfire age from 50 to 2350 years and calculated three different stand productivity indices, including site index. We assessed changes in forest productivity with time using two complementary approaches: (1) by comparing productivity among the chronosequence stands and (2) by comparing the productivity of successive cohorts of trees within the same stands to determine the influence of time independently of other site factors. Charcoal stratigraphy indicates that the forest stands differ in their fire history and originated either from high- or low-severity soil burns. Both chronosequence and cohort approaches demonstrate declines in black spruce productivity of 50-80% with increased paludification, particularly during the first centuries after fire. Paludification alters bryophyte abundance and succession, increases soil moisture, reduces soil temperature and nutrient availability, and alters the vertical distribution of roots. Low-severity soil burns significantly accelerate rates of paludification and productivity decline compared with high-severity fires and ultimately reduce nutrient content in black spruce needles. The two combined approaches indicate that paludification can be driven by forest succession only, independently of site factors such as position on slope. This successional paludification contrasts with edaphic paludification, where topography and drainage primarily control the extent and rate

  20. Riparian zone control on base cation concentration in boreal streams

    Directory of Open Access Journals (Sweden)

    J. L. J. Ledesma

    2013-06-01

    Full Text Available Riparian zones (RZ are a major factor controlling water chemistry in forest streams. Base cations' (BC concentrations, fluxes, and cycling in the RZ merit attention because a changing climate and increased forest harvesting could have negative consequences, including re-acidification, for boreal surface waters. We present a two-year study of BC and silica (Si flow-weighted concentrations from 13 RZ and 14 streams in different landscape elements of a boreal catchment in northern Sweden. The spatial variation in BC and Si dynamics in both RZ and streams was explained by differences in landscape element type, with highest concentrations in silty sediments and lowest concentrations in peat-dominated wetland areas. Temporal stability in BC and Si concentrations in riparian soil water, remarkably stable Mg/Ca ratios, and homogeneous mineralogy suggest that patterns found in the RZ are a result of a distinct mineralogical upslope signal in groundwater. Stream water Mg/Ca ratios indicate that the signal is subsequently maintained in the streams. Flow-weighted concentrations of Ca, Mg, and Na in headwater streams were represented by the corresponding concentrations in the RZ, which were estimated using the Riparian Flow-Concentration Integration Model (RIM approach. Stream and RZ flow-weighted concentrations differed for K and Si, suggesting a stronger biogeochemical influence on these elements, including K recirculation by vegetation and retention of Si within the RZ. Potential increases in groundwater levels linked to forest harvesting or changes in precipitation regimes would tend to reduce BC concentrations from RZ to streams, potentially leading to episodic acidification.

  1. Transport and transformation of soil-derived CO2, CH4 and DOC sustain CO2 supersaturation in small boreal streams.

    Science.gov (United States)

    Rasilo, Terhi; Hutchins, Ryan H S; Ruiz-González, Clara; Del Giorgio, Paul A

    2017-02-01

    Streams are typically supersaturated in carbon dioxide (CO2) and methane (CH4), and are recognized as important components of regional carbon (C) emissions in northern landscapes. Whereas there is consensus that in most of the systems the CO2 emitted by streams represents C fixed in the terrestrial ecosystem, the pathways delivering this C to streams are still not well understood. We assessed the contribution of direct soil CO2 injection versus the oxidation of soil-derived dissolved organic C (DOC) and CH4 in supporting CO2 supersaturation in boreal streams in Québec. We measured the concentrations of CO2, CH4 and DOC in 43 streams and adjacent soil waters during summer base-flow period. A mass balance approach revealed that all three pathways are significant, and that the mineralization of soil-derived DOC and CH4 accounted for most of the estimated stream CO2 emissions (average 75% and 10%, respectively), and that these estimated contributions did not change significantly between the studied low order (≤3) streams. Whereas some of these transformations take place in the channel proper, our results suggest that they mainly occur in the hyporheic zones of the streams. Our results further show that stream CH4 emissions can be fully explained by soil CH4 inputs. This study confirms that these boreal streams, and in particular their hyporheic zones, are extremely active processors of soil derived DOC and CH4, not just vents for soil produced CO2.

  2. Impact of forest harvesting on water quality and fluorescence characteristics of dissolved organic matter in eastern Canadian Boreal Shield lakes in summer

    Science.gov (United States)

    Glaz, P.; Gagné, J.-P.; Archambault, P.; Sirois, P.; Nozais, C.

    2015-12-01

    Forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. Water quality and fluorescence characteristics of dissolved organic matter (DOM) were measured over a 3-year period in eight eastern Boreal Shield lakes: four lakes were studied before, 1 and 2 years after forest harvesting (perturbed lakes) and compared with four undisturbed reference lakes (unperturbed lakes) sampled at the same time. ANOVAs showed a significant increase in total phosphorus (TP) in perturbed lakes when the three sampling dates were considered and in DOC concentrations when considering 1 year before and 1 year after the perturbation only. At 1 year post-clear cutting DOC concentrations were about 15 % greater in the perturbed lakes at ~ 15 mgC L-1 compared to 12.5 mgC L-1 in the unperturbed lakes. In contrast, absorbance and fluorescence measurements showed that all metrics remained within narrow ranges compared to the range observed in natural waters, indicating that forest harvesting did not affect the nature of DOM characterized with spectroscopic techniques. These results confirm an impact of forestry activities 1 year after the perturbation. However, this effect seems to be mitigated 2 years after, indicating that the system shows high resilience and may be able to return to its original condition in terms of water quality parameters assessed in this study.

  3. Emergy and ecosystem complexity

    Science.gov (United States)

    Ulgiati, Sergio; Brown, Mark T.

    2009-01-01

    The question "What drives complexity?" is addressed in this paper. To answer this question, we explore the way energy and material resources of different quality flow through ecosystems and support, directly and indirectly, ecosystems growth and development. Processes of resource transformation throughout the ecosystem build order, cycle materials, generate and sustain information. Energy drives all these processes and energetic principles explain much of what is observed, including energy degradation according to the laws of thermodynamics. Emergy, a quantitative measure of the global environmental work supporting ecosystem dynamics, is used here in order to provide a deeper understanding of complexity growth and decline in ecosystems. Ecosystem complexity is discussed in this paper in relation to changes in structure, organization and functional capacity, as explained by changes in emergy, empower, and transformity.

  4. Soil fluxes of carbonyl sulfide (COS) across four distinct ecosystems

    Science.gov (United States)

    Sun, W.; Maseyk, K. S.; Lett, C.; Juarez, S.; Kooijmans, L.; Mammarella, I.; Vesala, T.; Chen, H.; Seibt, U.

    2015-12-01

    Soils are additional but poorly resolved sinks of carbonyl sulfide (COS) in terrestrial ecosystems. COS has been proposed as a tracer for quantifying gross photosynthesis based on the coupled stomatal uptake of COS and CO2. But applying this tracer requires the soil COS flux to be subtracted from the ecosystem flux to obtain the actual plant flux. To simulate soil COS fluxes, we have built a 1-D diffusion-reaction model accounting for vertical transport in the soil, microbial sinks and sources, and a litter layer. Uptake and production of COS in the soil column are linked with soil temperature and moisture through empirical functions adapted from enzyme kinetics and lab incubations. We have measured soil COS fluxes and the related soil variables in four distinct ecosystems: a wheat field (Southern Great Plains, OK, USA), an oak woodland (Santa Monica Mountains, CA, USA), a tropical rainforest (La Selva Biological Station, Costa Rica) and a boreal pine forest (Hyytiälä, Finland). Across all sites, a lower soil temperature and a humid climate are generally favorable to soil COS uptake. Strong COS emissions were observed in the wheat field at high soil temperatures after harvesting but were absent in other ecosystems, indicating that COS exchange may behave differently in agricultural soils. We simulated the soil fluxes in all ecosystems using the diffusion-reaction model, and optimized the source/sink strength parameters with field data. The optimized model provides insights that are not attainable from data analysis alone: For example, the wheat field soil must have continued uptake activity even when it showed net emissions, and leaf litter contributed dominantly to the COS sink after rain in the oak woodland. We expect the new model to be useful for simulating global soil COS fluxes as field data on soil fluxes from a broader range of ecosystems become available.

  5. Examining mechanisms in the final stages of the elimination of boreal tree species on vulnerable sites in boreal Alaska

    Science.gov (United States)

    Juday, G. P.; Jess, R.; Alix, C. M.; Verbyla, D.

    2015-12-01

    The boreal forest of Alaska and western Canada exist in a complex mosaic of environments determined by elevation, aspect of exposure, and longitudinal and latitudinal gradients of change from warm, dry continental to maritime-influenced conditions. This forest region is largely made up of trees with two growth responses to temperature increases. Trees that decrease in growth are termed negative responders, and occupy warm, dry sites at low elevations. Trees that increase in radial growth are termed positive responders, and are largely in western Alaska, and at high elevation of the Brooks and Alaska Ranges. Since the Pacific climate regime shift of the 1970s, mature trees at low elevation sites have experienced increasing climate stress in several quasi-decadal cycles of intensifying drought stress. NDVI trends and tree ring records demonstrating radial growth decline are coherent. Phenological monitoring of spruce height growth also indicates that depletion of spring soil moisture is a critical process driven by the interaction of early warm season temperatures and precipitation. Novel biotic disturbance agents including spruce budworm, outbreaks of which are triggered by warm temperature anomalies related to its biology, and aspen leaf miner are depressing realized growth below climatically predicted levels, suggesting a pathway by which tree death is likely to occur before absolute temperature limits. As a result, insect outbreaks are degrading the otherwise strong long-term climate signal in Alaska boreal trees. However, young tree (> 40 yrs.) regeneration generally does not yet display the symptoms of acute high temperature stress. Overall, on these vulnerable sites, if temperature increases similar to the past 40 years continue, long term survival prospects are questionable because the climate conditions would be outside the limits that have historically defined the species ranges of aspen, Alaska birch, and black and white spruce.

  6. Bridging the Mire between E-Research and E-Publishing for Multimedia Digital Scholarship in the Humanities and Social Sciences: An Australian Case Study

    Directory of Open Access Journals (Sweden)

    Andrew Jakubowicz

    2007-03-01

    Full Text Available Digital media developments confront the humanities and social sciences with major challenges in exploiting multimedia rich data sets. A critical need is demonstrated to bridge the divide between the building of multimedia digital repositories, and the publishing of research outcomes that exploit the interactive potential of digital media. Software that melds the steps in digital research and publishing, now disparate environments, into a single sequence of integrated procedures can provide a critical innovation for the transformation of digital research and publishing from a quasi-craft-like and demanding set of skills, into a transparent and user-directed flow process. Humanities and social science (HSS researchers who use multimedia data could be working more collaboratively, creatively and with far more international impact. The HSS have not yet exploited the interactive and collaborative potential offered by interactive computer technologies, and the expansion of digital repositories. Digital publishing has opened opportunities to incorporate both interactivity and multimedia into scholarly publishing, permitting new modes of visualization and creating ever mutable texts. Open Source software, can offer an internationally significant break-through in research definition, data collection and management, and interactive publishing, leading to a major paradigm shift in eHumanities and eSocialScience. The article proposes a framework for bridging the gap, overcoming the silo problem and building an interactive multimedia research environment (m.i.r.e..

  7. A Decade of Plant Species Changes on a Mire in the Italian Alps. Vegetation-Controlled or Climate-Driven Mechanisms?

    Energy Technology Data Exchange (ETDEWEB)

    Bragazza, L. [Department of Natural and Cultural Resources, University of Ferrara, Corso Porta Mare 2, I-44100 Ferrara (Italy)

    2006-08-15

    Variation of plant species cover on a Sphagnum-dominated mire in the south-eastern Alps of Italy was assessed over a 10-year period in relation to depth to the water table, peat accumulation rate, and climate. Population dynamics of vascular species appeared to be primarily affected by the autogenic process of peat accumulation, which determined the lowering of water-table position at microhabitat scale. Increase of depth to the water table through peat accumulation resulted in increased cover of ericaceous shrubs at previously moister microhabitats. Conversely, graminoid species such as Eriophorum vaginatum, Trichophorum caespitosum, and Scheuchzeria palustris being negatively affected by autogenic peat growth, were forced to shift their niche towards the wetter end of the water-table gradient. Carex limosa and Carex rostrata decreased their cover along the whole gradient in depth to the water table, likely due to multiple processes related to peat accumulation, competition with bryophytes, and a negative feedback due to increased litter deposition. Bryophytes, in particular Sphagnum mosses, appeared more sensitive to climatic conditions, with higher precipitation favouring faster-growing species. Accordingly, Sphagnum fallax and Sphagnum magellanicum increased their cover much more than Sphagnum capillifolium, whereas Polytrichum strictum showed the strongest decrease at sites where S. magellanicum cover increased most.

  8. Managed island ecosystems

    Science.gov (United States)

    McEachern, Kathryn; Atwater, Tanya; Collins, Paul W.; Faulkner, Kate R.; Richards, Daniel V.

    2016-01-01

    This long-anticipated reference and sourcebook for California’s remarkable ecological abundance provides an integrated assessment of each major ecosystem type—its distribution, structure, function, and management. A comprehensive synthesis of our knowledge about this biologically diverse state, Ecosystems of California covers the state from oceans to mountaintops using multiple lenses: past and present, flora and fauna, aquatic and terrestrial, natural and managed. Each chapter evaluates natural processes for a specific ecosystem, describes drivers of change, and discusses how that ecosystem may be altered in the future. This book also explores the drivers of California’s ecological patterns and the history of the state’s various ecosystems, outlining how the challenges of climate change and invasive species and opportunities for regulation and stewardship could potentially affect the state’s ecosystems. The text explicitly incorporates both human impacts and conservation and restoration efforts and shows how ecosystems support human well-being. Edited by two esteemed ecosystem ecologists and with overviews by leading experts on each ecosystem, this definitive work will be indispensable for natural resource management and conservation professionals as well as for undergraduate or graduate students of California’s environment and curious naturalists.

  9. Interannual variability of Antarctic Oscillation and its influence on East Asian climate during boreal winter and spring

    Institute of Scientific and Technical Information of China (English)

    FAN; Ke; WANG; Huijun

    2006-01-01

    The interannual variability of Antarctic Oscillation (AAO) and its influence on East Asian climate during both boreal winter and spring are addressed. The results show that the positive AAO anomaly decreases the cold activity over East Asia during both boreal winter and spring. AAO-related barotropic meridional teleconnection from Antarctic to Arctic is found through analysis of mean meridional circulations. This meridional teleconnection is remarkable over Eurasia during boreal winter and over the Pacific Ocean during boreal spring. The results also show that zonal mean zonal wind at high latitudes in Southern Hemisphere has well positive correlation with that of Eurasia during boreal winter and has negative correlation with Pacific North American teleconnection (PNA) during boreal spring, which again display the meridional teleconnection. Thus, local meridional teleconnection is a possible linkage for interaction of circulations at mid-high latitudes between both hemispheres.

  10. Assessing the response of area burned to changing climate in western boreal North America using a Multivariate Adaptive Regression Splines (MARS) approach

    Science.gov (United States)

    Balshi, M. S.; McGuire, A.D.; Duffy, P.; Flannigan, M.; Walsh, J.; Melillo, J.

    2009-01-01

    Fire is a common disturbance in the North American boreal forest that influences ecosystem structure and function. The temporal and spatial dynamics of fire are likely to be altered as climate continues to change. In this study, we ask the question: how will area burned in boreal North America by wildfire respond to future changes in climate? To evaluate this question, we developed temporally and spatially explicit relationships between air temperature and fuel moisture codes derived from the Canadian Fire Weather Index System to estimate annual area burned at 2.5?? (latitude ?? longitude) resolution using a Multivariate Adaptive Regression Spline (MARS) approach across Alaska and Canada. Burned area was substantially more predictable in the western portion of boreal North America than in eastern Canada. Burned area was also not very predictable in areas of substantial topographic relief and in areas along the transition between boreal forest and tundra. At the scale of Alaska and western Canada, the empirical fire models explain on the order of 82% of the variation in annual area burned for the period 1960-2002. July temperature was the most frequently occurring predictor across all models, but the fuel moisture codes for the months June through August (as a group) entered the models as the most important predictors of annual area burned. To predict changes in the temporal and spatial dynamics of fire under future climate, the empirical fire models used output from the Canadian Climate Center CGCM2 global climate model to predict annual area burned through the year 2100 across Alaska and western Canada. Relative to 1991-2000, the results suggest that average area burned per decade will double by 2041-2050 and will increase on the order of 3.5-5.5 times by the last decade of the 21st century. To improve the ability to better predict wildfire across Alaska and Canada, future research should focus on incorporating additional effects of long-term and successional

  11. The quickening pace and widening scope of ecosystem transformation under climate change (Invited)

    Science.gov (United States)

    Graumlich, L. J.; Bunn, A. G.

    2013-12-01

    When will we see climate-driven impacts on ecosystems and the associated services they provide to humans? Two large ecosystems stand out as heading towards tipping points: arctic ecosystems, and the forests of western North America. While each ecosystem is structurally distinct (i.e., tundra and sparse boreal forests vs. closed canopy forest) and proximate drivers of change are different (i.e., warming vs. drought), commonalities between them offer insights into what processes lead to the kind of ecosystem changes that have the potential to truly 'tip' into a novel regime. First, scale matters: in both ecosystems the spatial scale of change is unprecedented since the Holocene Climate Optimum more than 5,000 years ago. In the Arctic we see widespread changes in the timing and magnitude of ecosystem productivity, which affects biogeochemical cycling, evapotranspiration, and albedo. In western US forests, large fires have increased in frequency by a factor of 4 over the past few decades, driven in large part by broad-scale, severe droughts. Second, timing is everything: changing phenology is associated with unraveling ecological relationships. In the Arctic we see a reduction of seasonality in temperature and vegetation production equivalent to several degrees of latitudinal shift towards the equator. In western US forests, relatively small advances in the timing of snowmelt are associated with earlier dry down of fine fuels, which, in turn, lengthens the fire season. Finally, and perhaps most importantly, ecosystem change can and will accelerate climate change. This can be seen in high latitude systems, as well as in the American West, as changes in microclimate, albedo, and ecosystem function feed back to atmospheric processes. Such large-scale, abrupt and non-linear changes in ecosystems and the associated provision of ecosystem services are one of the greatest challenges society faces in adapting to climate change.

  12. BUSINESS ECOSYSTEMS VS BUSINESS DIGITAL ECOSYSTEMS

    Directory of Open Access Journals (Sweden)

    Marinela Lazarica

    2006-05-01

    Full Text Available E-business is often described as the small organisations’ gateway to global business and markets. The adoption of Internet-based technologies for e-business is a continuous process, with sequential steps of evolution. The latter step in the adoption of Internet-based technologies for business, where the business services and the software components are supported by a pervasive software environment, which shows an evolutionary and self-organising behaviour are named digital business ecosystems. The digital business ecosystems are characterized by intelligent software components and services, knowledge transfer, interactive training frameworks and integration of business processes and e-government models.

  13. Transpiration response of boreal forest plants to permafrost thaw

    Science.gov (United States)

    Cable, J.; Ogle, K.; Welker, J. M.

    2011-12-01

    Shifts in the rate and patterns of evapotranspiration with permafrost thaw, vegetation change, and altered climatic conditions are unknown in boreal systems. Specifically, the response of transpiration is not well understood but critical to quantify given its non-linear response to climate. We asked: what is the effect of permafrost thaw on the transpiration dynamics of sub-Arctic boreal plants? We utilized a Bayesian analysis approach to quantify the responses of plants located in areas with and without stable permafrost to current and antecedent vapor pressure deficit, soil moisture, soil temperature, and the prior year's soil temperature. We measured stomatal conductance (gs) on six species of plants over two summers. For the analysis, the plants were grouped into three functional types: deciduous shrubs, evergreen sub-shrubs, and black spruce trees. The model we constructed includes a VPD (current and antecedent) sensitivity term modeled as a function of soil moisture (current and antecedent), and a "base" gs term modeled as a function of current soil temperature (at different depths), thaw depth, and the prior growing season's soil temperature (for each month, May - September). Current VPD was more important early in the growing season, but antecedent VPD was more important later in the growing season. The memory of gs for antecedent VPD was ~ three weeks in the past. The daily trends were less resolved for the site with degrading permafrost. Deeper thaw resulted in higher sensitivity to VPD and higher gs, particularly at the site with stable permafrost. Deciduous shrubs showed the strongest effect. At the site with thawing permafrost, soil water positively affected the sensitivity of gs to VPD for the deciduous shrubs but had a negative effect on black spruce. Current soil moisture was important early in the growing season but antecedent moisture was important at the end. The site with thawing permafrost had a longer memory (two weeks) for antecedent moisture

  14. Atmospheric ions, boreal forests and impacts on climate

    Science.gov (United States)

    Manninen, H. E.; Nieminen, T.; Franchin, A.; Järvinen, E.; Kontkanen, J.; Hirsikko, A.; Hõrrak, U.; Mirme, A.; Tammet, H.; Kerminen, V.-M.; Petäjä, T.; Kulmala, M.

    2012-04-01

    than 2 nm in diameter by charging the aerosol sample with unipolar corona chargers (Manninen et al., 2009). According to earlier studies, the atmospheric nucleation and cluster activation take place at the mobility diameter range of 1.5-2 nm. Therefore, the ion spectrometers allow direct measurements at exactly the size where atmospheric nucleation takes place. The results indicate that the ion-induced nucleation contributes ~1-30% to the NPF events in most atmospheric conditions (Manninen et al., 2010). In other words, neutral particle formation seems to dominate over ion-mediated mechanisms, at least in the boreal forest conditions. Acknowledgements. This research was supported by the Academy of Finland Center of Excellence program (project number 1118615). Hirsikko, A. et al.: Atmospheric ions and nucleation: a review of observations, Atmos. Chem. Phys., 11, 767-798, 2011. IPCC, Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK and New York, NY, USA, 996 pp, 2007. Kulmala, M., and Kerminen, V.-M.: On the growth of atmospheric nanoparticles, Atmos. Res., 90, 132-150, 2008. Manninen, H.E. et al.: Long-term field measurements of charged and neutral clusters using Neutral cluster and Air Ion Spectrometer (NAIS). Boreal Env. Res. 14, 591-605, 2009. Manninen, H.E. et al., EUCAARI ion spectrometer measurements at 12 European sites - analysis of new particle formation events, Atmos. Chem. Phys., 10, 7907-7927, 2010. Mirme, A. et al.: A Wide-range multi-channel Air Ion Spectrometer, Boreal Environ. Res., 12, 247-264, 2007. Tammet, H.: Symmetric inclined grid mobility analyzer for the measurement of charged clusters and fine nanoparticles in atmospheric air. Aerosol Science and Technology, 45, 468 - 479, 2011.

  15. On the Karst Ecosystem

    Institute of Scientific and Technical Information of China (English)

    袁道先

    2001-01-01

    In this paper the author gives a definition of the karst ecosystem and discusses the characteristics of the karst environment and karst ecosystem and the relationship between life and the karst environment. Finally he clarifies the structure, driving force and functions of the karst system.``

  16. Arctic Boreal Vulnerability Experiment (ABoVE) Science Cloud

    Science.gov (United States)

    Duffy, D.; Schnase, J. L.; McInerney, M.; Webster, W. P.; Sinno, S.; Thompson, J. H.; Griffith, P. C.; Hoy, E.; Carroll, M.

    2014-12-01

    The effects of climate change are being revealed at alarming rates in the Arctic and Boreal regions of the planet. NASA's Terrestrial Ecology Program has launched a major field campaign to study these effects over the next 5 to 8 years. The Arctic Boreal Vulnerability Experiment (ABoVE) will challenge scientists to take measurements in the field, study remote observations, and even run models to better understand the impacts of a rapidly changing climate for areas of Alaska and western Canada. The NASA Center for Climate Simulation (NCCS) at the Goddard Space Flight Center (GSFC) has partnered with the Terrestrial Ecology Program to create a science cloud designed for this field campaign - the ABoVE Science Cloud. The cloud combines traditional high performance computing with emerging technologies to create an environment specifically designed for large-scale climate analytics. The ABoVE Science Cloud utilizes (1) virtualized high-speed InfiniBand networks, (2) a combination of high-performance file systems and object storage, and (3) virtual system environments tailored for data intensive, science applications. At the center of the architecture is a large object storage environment, much like a traditional high-performance file system, that supports data proximal processing using technologies like MapReduce on a Hadoop Distributed File System (HDFS). Surrounding the storage is a cloud of high performance compute resources with many processing cores and large memory coupled to the storage through an InfiniBand network. Virtual systems can be tailored to a specific scientist and provisioned on the compute resources with extremely high-speed network connectivity to the storage and to other virtual systems. In this talk, we will present the architectural components of the science cloud and examples of how it is being used to meet the needs of the ABoVE campaign. In our experience, the science cloud approach significantly lowers the barriers and risks to organizations

  17. Microwave snow emission modeling uncertainties in boreal and subarctic environments

    Directory of Open Access Journals (Sweden)

    A. Roy

    2015-10-01

    Full Text Available This study aims to better understand and quantify the uncertainties in microwave snow emission models using the Dense Media Radiative Theory-Multilayer model (DMRT-ML with in situ measurements of snow properties. We use surface-based radiometric measurements at 10.67, 19 and 37 GHz in boreal forest and subarctic environments and a new in situ dataset of measurements of snow properties (profiles of density, snow grain size and temperature, soil characterization and ice lens detection acquired in the James Bay and Umijuaq regions of Northern Québec, Canada. A snow excavation experiment – where snow was removed from the ground to measure the microwave emission of bare frozen ground – shows that small-scale spatial variability in the emission of frozen soil is small. Hence, variability in the emission of frozen soil has a small effect on snow-covered brightness temperature (TB. Grain size and density measurement errors can explain the errors at 37 GHz, while the sensitivity of TB at 19 GHz to snow increases during the winter because of the snow grain growth that leads to scattering. Furthermore, the inclusion of observed ice lenses in DMRT-ML leads to significant improvements in the simulations at horizontal polarization (H-pol for the three frequencies (up to 20 K of root mean square error. However, the representation of the spatial variability of TB remains poor at 10.67 and 19 GHz at H-pol given the spatial variability of ice lens characteristics and the difficulty in simulating snowpack stratigraphy related to the snow crust. The results also show that for ground-based radiometric measurements, forest emission reflected by the surface leads to TB underestimation of up to 40 K if neglected. We perform a comprehensive analysis of the components that contribute to the snow-covered microwave signal, which will help to develop DMRT-ML and to improve the required field measurements. The analysis shows that a better consideration of ice lenses and

  18. Ecosystem Viable Yields

    CERN Document Server

    De Lara, Michel; Oliveros-Ramos, Ricardo; Tam, Jorge

    2011-01-01

    The World Summit on Sustainable Development (Johannesburg, 2002) encouraged the application of the ecosystem approach by 2010. However, at the same Summit, the signatory States undertook to restore and exploit their stocks at maximum sustainable yield (MSY), a concept and practice without ecosystemic dimension, since MSY is computed species by species, on the basis of a monospecific model. Acknowledging this gap, we propose a definition of "ecosystem viable yields" (EVY) as yields compatible i) with biological viability levels for all time and ii) with an ecosystem dynamics. To the difference of MSY, this notion is not based on equilibrium, but on viability theory, which offers advantages for robustness. For a generic class of multispecies models with harvesting, we provide explicit expressions for the EVY. We apply our approach to the anchovy--hake couple in the Peruvian upwelling ecosystem between the years 1971 and 1981.

  19. Annual variations of atmospheric VOC concentrations in a boreal forest

    Energy Technology Data Exchange (ETDEWEB)

    Hakola, H.; Hellen, H.; Tarvainen, V. (Finnish Meteorological Institute Air Quality Research, Helsinki (Finland)); Baeck, J. (Dept. of Forest Ecology, Univ. of Helsinki (Finland)); Patokoski, J.; Rinne, J. (Dept. of Physics, Univ. of Helsinki (Finland))

    2009-07-01

    Ambient atmospheric concentrations of monoterpene compounds were measured above a boreal forest in Hyytiaelae, Finland during 2000-2007. For most of the time, two samples per week were collected, although there are some gaps in the data due to analytical or other issues. The monoterpene concentrations reached their maximum in summer, although they were found to be quite high also during winter. The main compounds found during winter were alpha-pinene, DELTA3-carene, beta-pinene and camphene. In summer 1,8-cineol and sabinene were also present in the samples. The concentrations of alpha-pinene, beta-pinene/myrcene, camphene, DELTA3-carene increased during the measurement period both in winter and in summer. This increase cannot be explained by meteorological conditions. The possible explanations could be human activities in the vicinity of the sampling site in addition to forest growth. The seasonal cycles of daytime concentrations were found to follow emission fluxes modeled using a simple temperature dependent parameterisation. The measured monoterpene concentrations were used, together with emission rate measurements, for estimating ambient atmospheric beta-caryophyllene concentration which cannot be directly measured due to its high reactivity against ozone. (orig.)

  20. Community structure of ectomycorrhizal fungi in Swedish boreal forests

    Energy Technology Data Exchange (ETDEWEB)

    Jonsson, Lena [Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Forest Mycology and Pathology

    1998-12-31

    The main aim of this work has been to elucidate the species composition and community structure of ectomycorrhizal fungi associated with mature trees and naturally regenerated seedlings in natural boreal forests in Sweden. Further, the effects of disturbances, such as wildfire and nitrogen inputs, were studied. Sporocarp surveys, morphological stratification and DNA-based analyses of mycorrhizas were used to describe the mycorrhizal fungal communities. In addition, a reference database useful for identifying individual mycorrhizas was developed based on analyses of sporocarp tissue. Overall, the species richness of ectomycorrhizal fungi was at least 30 to 40 times higher than that of their host trees. Naturally regenerated seedlings were colonized by the ectomycorrhizal fungal species present in the mycelial network of the old trees, indicating that the species composition will remain about the same provided that the host does not disappear. Wildfire, disturbing the fungal continuum, caused a shift in the frequencies of ectomycorrhizal fungi rather than a change in species composition. Nitrogen addition did not have any detectable effect on the abundance or species richness of mycorrhizas, but led to a decrease in sporocarp production. In all the studies, there was little resemblance between the species composition of sporocarps and that of mycorrhizas. The ITS-RFLP reference database was very useful in identifying single mycorrhizas, and proved to be a powerful tool for species identification of unknown mycorrhizas 76 refs, 2 figs, 2 tabs

  1. Quantum and Ecosystem Entropies

    Directory of Open Access Journals (Sweden)

    A. D. Kirwan

    2008-06-01

    Full Text Available Ecosystems and quantum gases share a number of superficial similarities including enormous numbers of interacting elements and the fundamental role of energy in such interactions. A theory for the synthesis of data and prediction of new phenomena is well established in quantum statistical mechanics. The premise of this paper is that the reason a comparable unifying theory has not emerged in ecology is that a proper role for entropy has yet to be assigned. To this end, a phase space entropy model of ecosystems is developed. Specification of an ecosystem phase space cell size based on microbial mass, length, and time scales gives an ecosystem uncertainty parameter only about three orders of magnitude larger than Planck’s constant. Ecosystem equilibria is specified by conservation of biomass and total metabolic energy, along with the principle of maximum entropy at equilibria. Both Bose - Einstein and Fermi - Dirac equilibrium conditions arise in ecosystems applications. The paper concludes with a discussion of some broader aspects of an ecosystem phase space.

  2. Danger in the nursery : impact on birds of tar sands oil development in Canada's boreal forest

    Energy Technology Data Exchange (ETDEWEB)

    Wells, J. [Boreal Songbird Initiative, Seattle, WA (United States); Casey-Lefkowitz, S.; Chavarria, G. [Natural Resources Defense Council, New York, NY (United States); Dyer, S. [Pembina Institute, Drayton Valley, AB (Canada)

    2008-07-01

    This report discussed the impacts of tar sands oil development in Canada's boreal forest. The Canadian boreal forest is one of the world's most important breeding areas for migratory birds, with 1 billion to 3 billion individual birds from at least 300 species known to regularly breed there. Approximately 30 per cent of all shorebirds and 30 per cent of all landbirds that breed in the United States and Canada do so within the boreal. The section of the boreal forest that sits over the tar sands region of Alberta is rapidly being fragmented by oil development. As much as 34 to 66 per cent of the Canadian boreal forest, up to 438 million acres, may no longer be intact. In Alberta, 86 per cent of the boreal forest is no longer considered intact, thus putting valuable bird habitat at risk. This report first provided background information on Canada's boreal forest as North America's nesting bird destination. It then reviewed the dangers created by tar sands operations for boreal birds. It noted that tar sands mining destroys boreal bird habitat; tailings ponds trap birds in oil waste; tar sands drilling fragments bird habitat; tar sands water withdrawals harm wetlands and water habitats; and tar sands toxins weaken and kill boreal birds. The impacts of tar sands pipelines and refineries were also discussed along with global warming impacts on boreal birds and the path forward for habitat protection. It was recommended that Alberta should implement a moratorium on new tar sands lease sales, and that Alberta and Canada should halt project approvals until long-term mitigation strategies and conservation measures are in place. refs., tabs., figs.

  3. Production of biomass on the fields and mires, and utilisation of it for energy production; Biomassan tuotanto pelloilla ja soilla sekae kaeyttoe energiantuotantoon

    Energy Technology Data Exchange (ETDEWEB)

    Mela, T.; Hoemmoe, L.; Partala, A. [Agricultural Research Center, Jokioinen (Finland)] [and others

    1996-12-31

    The research will be carried out as five sub-projects. The first sub-project `Production and breeding of reed canary grass` the biomass production of the reed canary grass will be studied. The breeding material consists of 101 populations collected from various parts of the country in summer 1993, breeder`s lines obtained from Svaloef-Weibull Ab from Sweden (13 populations), and 7 reed canary grass species. A breeding field for reed canary grass was founded in summer 1994. The field was supplemented in the summer 1995. The first selection of the breeding material was made in 1995. The volume of the seed harvest, the germination capacity and development were studied with harvesting time study. Five different plantations were made for the nutrient cycling and nutrient balance of the reed canary grass at Jokioinen in the summer 1995. Two liming and nitrogen-fertilization test areas were made in Northern Ostrobothnia in 1994. The evaporation potential of reed canary grass was studied in connection with drying of a peat production field was studied in the sub-project no. 2, `Cultivation of energy plants at the mire, and the drying of peat production area`, during the summer 1995, and the biomass production using greenhouse-plantations founded in 1994. The plantations evaporated from carex peat bases during the inspection season depending on fertilization 171-450 mm of water, and from the Sphagnum peat base 105-160 mm of water. Average daily evaporations from Carex peat bases were 2.6 - 6.8 mm and from Sphagnum peat bases 1.6 - 2.4 mm

  4. Climate as a driver of continent-wide irruptions in boreal seed-eating birds (Invited)

    Science.gov (United States)

    Strong, C.; Zuckerberg, B.; Betancourt, J. L.

    2013-12-01

    Boreal seed-eating birds regularly breed and overwinter throughout Canada and Alaska, but every few years these species demonstrate impressive irruptive migrations out of the boreal forest and into more southerly regions. It is thought that irruptive migrations are inversely dependent on a circumboreally synchronized pattern of seed crop fluctuations in boreal trees; seed-eating boreal birds stay in the north when food is plentiful, but sojourn south when food is scarce. Because both seed production and bird irruptions are characterized by periodicity ranging from biennial to decadal cycles, there is a strong possibility that these ecological phenomena are driven by climate variability. Using over twenty years of data from Project FeederWatch (a national citizen science project), we found that 'super irruptions' are correlated with continent-wide irruptive events in pine siskin population, and that these irruptions are associated with multi-decadal climate variability of Pacific origin. We also investigate how climate variability may influence the distribution of boreal bird species across different regions of North America during winter, and evaluate results in the context of limited banding data to assess possible geographic pathways of irruptions.

  5. CO2 balance of boreal, temperate, and tropical forests

    NARCIS (Netherlands)

    Luyssaert, S.; Inglima, I.; Jungs, M.; Richardson, A.; Reichsteins, M.; Papale, D.; Piao, S.L.; Schulzes, E.D.; Wingate, L.; Matteucci, G.; Aragaoss, L.; Aubinet, M.; Beers, van C.; Bernhofer, C.; Black, K.G.; Bonal, D.; Bonnefonds, J.M.; Chambers, J.; Ciais, P.; Cook, B.; Davis, K.J.; Dolman, A.J.; Gielen, B.; Goulden, M.; Grace, J.; Granier, A.; Grelle, A.; Griffis, T.; Grunwald, T.; Guidolotti, G.; Hanson, P.J.; Harding, R.; Hollinger, D.Y.; Hutyra, L.R.; Kolari, P.; Kruijt, B.; Kutsch, W.; Lagergren, F.; Laurila, T.; Law, B.E.; Maire, Le G.; Lindroth, A.; Loustau, D.; Malhi, Y.; Mateus, J.; Migliavacca, M.; Misson, L.; Montagnani, L.; Moncrief, J.; Moors, E.J.; Munger, J.W.; Nikinmaa, E.; Ollinger, S.V.; Pita, G.; Rebmann, C.; Roupsard, O.; Saigusa, N.; Sanz, M.J.; Seufert, G.; Sierra, C.; Smith, M.; Tang, J.; Valentini, R.; Vesala, T.; Janssens, I.A.

    2007-01-01

    Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are be

  6. Total Ecosystem Carbon Stock

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Total ecosystem carbon includes above- and below-ground live plant components (such as leaf, branch, stem and root), dead biomass (such as standing dead wood, down...

  7. Revisiting software ecosystems research

    DEFF Research Database (Denmark)

    Manikas, Konstantinos

    2016-01-01

    ‘Software ecosystems’ is argued to first appear as a concept more than 10 years ago and software ecosystem research started to take off in 2010. We conduct a systematic literature study, based on the most extensive literature review in the field up to date, with two primarily aims: (a) to provide...... an updated overview of the field and (b) to document evolution in the field. In total, we analyze 231 papers from 2007 until 2014 and provide an overview of the research in software ecosystems. Our analysis reveals a field that is rapidly growing both in volume and empirical focus while becoming more mature...... from evolving. We propose means for future research and the community to address them. Finally, our analysis shapes the view of the field having evolved outside the existing definitions of software ecosystems and thus propose the update of the definition of software ecosystems....

  8. Formation of Service Ecosystems

    DEFF Research Database (Denmark)

    Jonas, Julia M.; Sörhammar, David; Satzger, Gerhard

    – i.e. the “birth phase” (Moore, 2009) of a service ecosystem. This paper, therefore, aims to explore how the somewhat “magic” processes of service ecosystem formation that are being taken for granted actually occur. Methodology/Approach: Building on a review of core elements in the definitions......Purpose: Researchers in several different academic disciplines (such as marketing, information systems, and organization) have focused on investigating service and business ecosystems (e.g. Lusch and Nambisan, 2015; Gawer and Cusumano, 2014; Kude et al. 2012). We reviewed 69 papers in service...... science, operations management, marketing, and organization journals. The majority of these papers focus on describing established service ecosystems,often on a more abstract “meso-level” (Akaka et al., 2015). Key notions are “…self-contained, self-adjusting system[s] of resource integrating actors...

  9. Chinese Ecosystem Research Network

    Institute of Scientific and Technical Information of China (English)

    Huang Tieqing; Liu Jian; Chen Panqin; Fu Bojie

    2002-01-01

    The article analyzes the development of the Chinese Ecosystem Research Network, and its mission, mandate, and management mechanisms, with examples of research, demonstration and consultation for policy-setting.

  10. The Future of Eurasian Boreal Forests: Ecological Modeling Projections in the Russian Federation

    Science.gov (United States)

    Lutz, D.; Shugart, H.

    2008-12-01

    Ecological modeling is one of the primary methodologies for making predictions on future changes in forested ecosystems such as those occurring in Northern Eurasia and Siberia. In particular, combining ecological modeling with global circulation model simulation outputs is a method in which scientists can forecast the impact of climate change on biodiversity (Thuiller, 2007) as well as the forested landscape. Dynamic global vegetation models (DGVMs) have been designed for specifically this purpose, however, these vegetation models run at large spatial scales and as a result make predictions that are highly uncertain (Purves and Pacala, 2008). In previous papers, we discussed the FAREAST forest gap model and its ability to accurately predict boreal forest dynamics at smaller scales and higher resolution than DGVMs. This presentation investigates the use of the FAREAST gap model, modified for spatial expansion to cover the entire country of Russia, to predict future land cover trends under different warming scenarios. The poster provides the initial framework for the project, as well as some initial results. The collection of input variables needed by FAREAST to model the Russian continent will involve collaboration with the Russian Academy of Sciences (CEPF). Together we have developed a framework in which to amalgamate both original (temperature, precipitation, soil values) parameters as well as new parameters (fire probability, logging probability) into a GIS database that can be integrated with the FAREAST model. This framework will be capable of providing visual and graphical output for interpretation of large model runs. In order to ensure accuracy in FAREAST's ability to simulate the current environment, a run of the model under current-day conditions will be compared to recent remote sensing land cover maps. The GLC2000 land cover classification project (EU JRC) will be the primary validation method with additional validation through other biophysical

  11. Ten-year responses of ground-dwelling spiders to retention harvest in the boreal forest.

    Science.gov (United States)

    Pinzon, Jaime; Spence, John R; Langor, David W; Shorthouse, David P

    2016-12-01

    The Ecosystem Management Emulating Natural Disturbances (EMEND) project tests the hypothesis that varying levels of green tree retention maintain and retain forest biodiversity better than conventional clear-cutting. We studied epigaeic spiders to assess biodiversity changes 2, 5, and 10 yr following a range of partial retention harvests (clear-cut, 10-75% retention) and unharvested controls in four boreal mixedwood cover types. A total of 56 371 adult spiders representing 220 species was collected using pitfall traps. Lasting effects on forest structure were proportional to harvest intensity. These changes strongly influenced spider richness, abundance, and species composition, as well as assemblage recovery. Distinctive assemblages were associated with disturbance level, especially with partial harvests (≤50% retention), and these were dominated by open-habitat species even 10 yr after harvest. Assemblages were more similar to those of controls in the highest (75%) retention treatment, but significant recovery toward the structure of pre-disturbance assemblages was not detected for any prescription in any cover type. Although early responses to retention harvest suggested positive effects on spider assemblages, these are better explained as lag effects after harvest because assemblages were less similar to those of unharvested controls 5 yr post-harvest, and only minor recovery was observed 10 yr following harvest. Retention of forest biodiversity decreased over time, especially in conifer stands and the lower (10-50%) retention treatments. Overall, retention harvests retained biodiversity and promoted landscape heterogeneity somewhat better than clear-cutting; however, there was a clear gradient of response and no retention "threshold" for conservation can be recommended on the basis of our data. Furthermore, results suggest that retention harvest prescriptions should be adjusted for cover type. We show that low retention ameliorated impacts in broadleaved

  12. Boreal ditched forest and peatland are more vulnerable to forest fire than unditched areas

    Science.gov (United States)

    Köhler, Stephan J.; Granath, Gustav; Landahl, Anna; Fölster, Jens

    2016-04-01

    During summer of 2014 the largest wildfire in Swedish modern history occurred. The fire was ignited in a forest close to the Swedish town Sala and incinerated a total of 14 000 ha. The frequency of wildfires is expected to increase, due to effects of climate change such as increased temperature and decreased precipitation during the summer months. Wildfires can have a considerable impact on aquatic ecosystems and previous studies of wildfires have shown elevated concentrations of nutrients, cat- and anions. The area of the fire mainly consists of forestland, peatland and lakes and has been affected by acidification and intensive forestry. To assess the fire severity and the effects on the water chemistry, the fire severity were analyzed and classified using aerial phtographs and high resolution LIDAR data. The analysis indicated that increased fire intensity caused increased fire severity and that drained forested areas were more vulnerable to fire than undrained peatland. Measurements of water chemistry were conducted at nine streams and ten lakes inside the affected area. At two sites sensors for multiple parameters were deployed. During the initial three months of the post-fire period large peaks of ammonia-N and sulphate were observed in the streams and in a majority of the lakes while DOC was suppressed. In one stream Gärsjöbäcken the median concentrations of ammonia-N were 79 times higher after the fire. Due to nitrification the elevated concentrations of ammonia-N-nitrogen caused elevated concentrations of nitrate-nitrogen. The initial peak of sulphate caused a drop in ANC but after the peak had past ANC increased due to elevated concentrations of base cations. Correlation analysis of fire severity and water chemistry indicated that the maximum concentrations of ammonia-N increased with severely burned canopies in drained forested peatlands and in scorched open peatland. In a future climate with increased dry spells extensive ditching operations in

  13. Temperature and moisture effects on greenhouse gas emissions from deep active-layer boreal soils

    Science.gov (United States)

    Bond-Lamberty, Ben; Smith, A. Peyton; Bailey, Vanessa

    2016-12-01

    Rapid climatic changes, rising air temperatures, and increased fires are expected to drive permafrost degradation and alter soil carbon (C) cycling in many high-latitude ecosystems. How these soils will respond to changes in their temperature, moisture, and overlying vegetation is uncertain but critical to understand given the large soil C stocks in these regions. We used a laboratory experiment to examine how temperature and moisture control CO2 and CH4 emissions from mineral soils sampled from the bottom of the annual active layer, i.e., directly above permafrost, in an Alaskan boreal forest. Gas emissions from 30 cores, subjected to two temperatures and either field moisture conditions or experimental drought, were tracked over a 100-day incubation; we also measured a variety of physical and chemical characteristics of the cores. Gravimetric water content was 0.31 ± 0.12 (unitless) at the beginning of the incubation; cores at field moisture were unchanged at the end, but drought cores had declined to 0.06 ± 0.04. Daily CO2 fluxes were positively correlated with incubation chamber temperature, core water content, and percent soil nitrogen. They also had a temperature sensitivity (Q10) of 1.3 and 1.9 for the field moisture and drought treatments, respectively. Daily CH4 emissions were most strongly correlated with percent nitrogen, but neither temperature nor water content was a significant first-order predictor of CH4 fluxes. The cumulative production of C from CO2 was over 6 orders of magnitude higher than that from CH4; cumulative CO2 was correlated with incubation temperature and moisture treatment, with drought cores producing 52-73 % lower C. Cumulative CH4 production was unaffected by any treatment. These results suggest that deep active-layer soils may be sensitive to changes in soil moisture under aerobic conditions, a critical factor as discontinuous permafrost thaws in interior Alaska. Deep but unfrozen high-latitude soils have been shown to be

  14. Impacts of Thermokarst Formation and Wildfire on Boreal Forest Carbon Cycling

    Science.gov (United States)

    Fisher, J. P.; Estop-Aragones, C.; Thierry, A.; Hartley, I. P.; Murton, J.; Charman, D.; Williams, M.; Phoenix, G. K.

    2014-12-01

    At the global scale permafrost temperatures are increasing, leading to a thickening of the active layer and an increase in the amount of previously immobilised C exposed to microbial decay and subsequent release to the atmosphere. Against the backdrop of this overall trend, perturbations to permafrost systems caused by wildfires or thermokarst driven wetland formation can cause dramatic shifts in the C exchange of these ecosystems as a result of the changes in plant communities and soil thermal regimes they cause. These dynamic components of permafrost landscapes are often neglected in coupled climate-C models. However, a clear understanding of the impact of these perturbations on C cycling is crucial if we are to accurately predict future permafrost feedbacks to climate change. This is particularly pertinent given that the frequency of both forest fires and thermokarst formation is likely to increase with future climate warming. In order to assess the impact of these perturbations on C cycling we established paired burned and unburned spruce forest and paired peat plateau and thaw feature field sites near Whitehorse, YT and Yellowknife, NT within the boreal region of Canada. At each site tree photosynthetic biomass was quantified using DBH based allometric scaling equations. A combination of percentage cover surveys, biomass harvests, and leaf area determination were used to calculate understory and wetland photosynthetic biomass. Measurements of spruce and understory photosynthesis and plant and soil respiration were made using specialised acrylic chambers and an IRGA. Combining these data has allowed us to determine the impact of thermokarst formation and wildfire on C exchange with the atmosphere. This has allowed us to assess whether the dramatic increase in plant productivity between peat plateau and wetland habitats has the potential to offset thermokarst associated C losses. We have also gained an understanding of whether increases in light availability for

  15. Regional Instability in the Abundance of Open Stands in the Boreal Forest of Eastern Canada

    Directory of Open Access Journals (Sweden)

    Rija Rapanoela

    2016-05-01

    Full Text Available Fires are a key disturbance of boreal forests. In fact, they are the main source of renewal and evolution for forest stands. The variability of fire through space and time results in a diversified forest mosaic, altering their species composition, structure and productivity. A resilient forest is assumed to be in a state of dynamic equilibrium with the fire regime, so that the composition, age structure and succession stages of forests should be consistent with the fire regime. Dense spruce-moss stands tend, however, to diminish in favour of more open stands similar to spruce-lichen stands when subjected to more frequent and recurring disturbances. This study therefore focused on the effects of spatial and temporal variations in burn rates on the proportion of open stands over a large geographic area (175,000 km2 covered by black spruce (Picea mariana (Mill. Britton, Sterns, Poggenb.. The study area was divided into 10 different zones according to burn rates, as measured using fire-related data collected between 1940 and 2006. To test if the abundance of open stands was unstable over time and not in equilibrium with the current fire regime, forest succession was simulated using a landscape dynamics model that showed that the abundance of open stands should increase progressively over time in zones where the average burn rate is high. The proportion of open stands generated during a specific historical period is correlated with the burn rate observed during the same period. Rising annual burn rates over the past two decades have thereby resulted in an immediate increase in the proportion of open stands. There is therefore a difference between the current proportion of open stands and the one expected if vegetation was in equilibrium with the disturbance regime, reflecting an instability that may significantly impact the way forest resources are managed. It is apparent from this study that forestry planning should consider the risks associated

  16. Functional roles affect diversity-succession relationships for boreal beetles.

    Directory of Open Access Journals (Sweden)

    Heloise Gibb

    Full Text Available Species diversity commonly increases with succession and this relationship is an important justification for conserving large areas of old-growth habitats. However, species with different ecological roles respond differently to succession. We examined the relationship between a range of diversity measures and time since disturbance for boreal forest beetles collected over a 285 year forest chronosequence. We compared responses of "functional" groups related to threat status, dependence on dead wood habitats, diet and the type of trap in which they were collected (indicative of the breadth of ecologies of species. We examined fits of commonly used rank-abundance models for each age class and traditional and derived diversity indices. Rank abundance distributions were closest to the Zipf-Mandelbrot distribution, suggesting little role for competition in structuring most assemblages. Diversity measures for most functional groups increased with succession, but differences in slopes were common. Evenness declined with succession; more so for red-listed species than common species. Saproxylic species increased in diversity with succession while non-saproxylic species did not. Slopes for fungivores were steeper than other diet groups, while detritivores were not strongly affected by succession. Species trapped using emergence traps (log specialists responded more weakly to succession than those trapped using flight intercept traps (representing a broader set of ecologies. Species associated with microhabitats that accumulate with succession (fungi and dead wood thus showed the strongest diversity responses to succession. These clear differences between functional group responses to forest succession should be considered in planning landscapes for optimum conservation value, particularly functional resilience.

  17. Eastward propagating MJO during boreal summer and Indian monsoon droughts

    Science.gov (United States)

    Joseph, Susmitha; Sahai, A. K.; Goswami, B. N.

    2009-06-01

    Improved understanding of underlying mechanism responsible for Indian summer monsoon (ISM) droughts is important due to their profound socio-economic impact over the region. While some droughts are associated with ‘external forcing’ such as the El-Niño and Southern Oscillation (ENSO), many ISM droughts are not related to any known ‘external forcing’. Here, we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics. We show that most ISM droughts are associated with at least one very long break (VLB; breaks with duration of more than 10 days) and that the processes responsible for VLBs may also be the mechanism responsible for ISM droughts. Our analysis also reveals that all extended monsoon breaks (whether co-occurred with El-Niño or not) are associated with an eastward propagating Madden-Julian Oscillation (MJO) in the equatorial Indian Ocean and western Pacific extending to the dateline and westward propagating Rossby waves between 10° and 25°N. The divergent Rossby wave associated with the dry phase of equatorial convection propagates westward towards Indian land, couple with the northward propagating dry phase and leads to the sustenance of breaks. Thus, the propensity of eastward propagating MJO during boreal summer is largely the cause of monsoon droughts. While short breaks are not accompanied by westerly wind events (WWE) over equatorial western Pacific favorable for initiating air-sea interaction, all VLBs are accompanied by sustained WWE. The WWEs associated with all VLB during 1975-2005 initiate air-sea interaction on intraseasonal time scale, extend the warm pool eastward allowing the convectively coupled MJO to propagate further eastward and thereby sustaining the divergent circulation over India and the monsoon break. The ocean-atmosphere coupling on interannual time scale (such as El-Niño) can also produce VLB, but not necessary.

  18. boreal forest when timber prices and tree growth are stochastic

    Institute of Scientific and Technical Information of China (English)

    Timo Pukkala

    2015-01-01

    Background:Decisions on forest management are made under risk and uncertainty because the stand development cannot be predicted exactly and future timber prices are unknown. Deterministic calculations may lead to biased advice on optimal forest management. The study optimized continuous cover management of boreal forest in a situation where tree growth, regeneration, and timber prices include uncertainty. Methods:Both anticipatory and adaptive optimization approaches were used. The adaptive approach optimized the reservation price function instead of fixed cutting years. The future prices of different timber assortments were described by cross-correlated auto-regressive models. The high variation around ingrowth model was simulated using a model that describes the cross-and autocorrelations of the regeneration results of different species and years. Tree growth was predicted with individual tree models, the predictions of which were adjusted on the basis of a climate-induced growth trend, which was stochastic. Residuals of the deterministic diameter growth model were also simulated. They consisted of random tree factors and cross-and autocorrelated temporal terms. Results:Of the analyzed factors, timber price caused most uncertainty in the calculation of the net present value of a certain management schedule. Ingrowth and climate trend were less significant sources of risk and uncertainty than tree growth. Stochastic anticipatory optimization led to more diverse post-cutting stand structures than obtained in deterministic optimization. Cutting interval was shorter when risk and uncertainty were included in the analyses. Conclusions:Adaptive optimization and management led to 6%–14%higher net present values than obtained in management that was based on anticipatory optimization. Increasing risk aversion of the forest landowner led to earlier cuttings in a mature stand. The effect of risk attitude on optimization results was small.

  19. Stochastic processes dominate during boreal bryophyte community assembly.

    Science.gov (United States)

    Fenton, Nicole J; Bergeron, Yves

    2013-09-01

    Why are plant species found in certain locations and not in others? The study of community assembly rules has attempted to answer this question, and many studies articulate the historic dichotomy of deterministic (predictable niches) vs. stochastic (random or semi-random processes). The study of successional sequences to determine whether they converge, as would be expected by deterministic theory, or diverge, as stochastic theory would suggest, has been one method used to investigate this question. In this article we ask the question: Do similar boreal bryophyte communities develop in the similar habitat created by convergent succession after fires of different severities? Or do the stochastic processes generated by fires of different severity lead to different communities? Specifically we predict that deterministic structure will be more important for large forest-floor species than stochastic processes, and that the inverse will be true for small bryophyte species. We used multivariate regression trees and model selection to determine the relative weight of structure (forest structure, substrates, soil structure) and processes (fire severity) for two groups of bryophyte species sampled in 12 sites (seven high-severity and five low-severity fires). Contrary to our first hypothesis, processes were as important for large forest-floor bryophytes as for small pocket species. Fire severity, its interaction with the quality of available habitat, and its impact on the creation of biological legacies played dominant roles in determining community structure. In this study, sites with nearly identical forest structure, generated via convergent succession after high- and low-severity fire, were compared to see whether these sites supported similar bryophyte communities. While similar to some degree, both the large forest-floor species and the pocket species differed after high-severity fire compared to low-severity fire. This result suggests that the "how," or process of

  20. Downscaling GISS ModelE Boreal Summer Climate over Africa

    Science.gov (United States)

    Druyan, Leonard M.; Fulakeza, Matthew

    2015-01-01

    The study examines the perceived added value of downscaling atmosphere-ocean global climate model simulations over Africa and adjacent oceans by a nested regional climate model. NASA/Goddard Institute for Space Studies (GISS) coupled ModelE simulations for June- September 1998-2002 are used to form lateral boundary conditions for synchronous simulations by the GISS RM3 regional climate model. The ModelE computational grid spacing is 2deg latitude by 2.5deg longitude and the RM3 grid spacing is 0.44deg. ModelE precipitation climatology for June-September 1998-2002 is shown to be a good proxy for 30-year means so results based on the 5-year sample are presumed to be generally representative. Comparison with observational evidence shows several discrepancies in ModelE configuration of the boreal summer inter-tropical convergence zone (ITCZ). One glaring shortcoming is that ModelE simulations do not advance the West African rain band northward during the summer to represent monsoon precipitation onset over the Sahel. Results for 1998-2002 show that onset simulation is an important added value produced by downscaling with RM3. ModelE Eastern South Atlantic Ocean computed sea-surface temperatures (SST) are some 4 K warmer than reanalysis, contributing to large positive biases in overlying surface air temperatures (Tsfc). ModelE Tsfc are also too warm over most of Africa. RM3 downscaling somewhat mitigates the magnitude of Tsfc biases over the African continent, it eliminates the ModelE double ITCZ over the Atlantic and it produces more realistic orographic precipitation maxima. Parallel ModelE and RM3 simulations with observed SST forcing (in place of the predicted ocean) lower Tsfc errors but have mixed impacts on circulation and precipitation biases. Downscaling improvements of the meridional movement of the rain band over West Africa and the configuration of orographic precipitation maxima are realized irrespective of the SST biases.

  1. Downscaling GISS ModelE boreal summer climate over Africa

    Science.gov (United States)

    Druyan, Leonard M.; Fulakeza, Matthew

    2016-12-01

    The study examines the perceived added value of downscaling atmosphere-ocean global climate model simulations over Africa and adjacent oceans by a nested regional climate model. NASA/Goddard Institute for Space Studies (GISS) coupled ModelE simulations for June-September 1998-2002 are used to form lateral boundary conditions for synchronous simulations by the GISS RM3 regional climate model. The ModelE computational grid spacing is 2° latitude by 2.5° longitude and the RM3 grid spacing is 0.44°. ModelE precipitation climatology for June-September 1998-2002 is shown to be a good proxy for 30-year means so results based on the 5-year sample are presumed to be generally representative. Comparison with observational evidence shows several discrepancies in ModelE configuration of the boreal summer inter-tropical convergence zone (ITCZ). One glaring shortcoming is that ModelE simulations do not advance the West African rain band northward during the summer to represent monsoon precipitation onset over the Sahel. Results for 1998-2002 show that onset simulation is an important added value produced by downscaling with RM3. ModelE Eastern South Atlantic Ocean computed sea-surface temperatures (SST) are some 4 K warmer than reanalysis, contributing to large positive biases in overlying surface air temperatures (Tsfc). ModelE Tsfc are also too warm over most of Africa. RM3 downscaling somewhat mitigates the magnitude of Tsfc biases over the African continent, it eliminates the ModelE double ITCZ over the Atlantic and it produces more realistic orographic precipitation maxima. Parallel ModelE and RM3 simulations with observed SST forcing (in place of the predicted ocean) lower Tsfc errors but have mixed impacts on circulation and precipitation biases. Downscaling improvements of the meridional movement of the rain band over West Africa and the configuration of orographic precipitation maxima are realized irrespective of the SST biases.

  2. Movements of boreal caribou in the James Bay lowlands

    Directory of Open Access Journals (Sweden)

    Megan E. Hazell

    2011-09-01

    Full Text Available Little is known about the movements and home range of boreal woodland caribou (Rangifer tarandus in the James Bay lowlands, northern Ontario. Our preliminary study involves the use of GPS collars with Argos satellite system uplink to monitor movements of caribou and 10 animals were collared in December 2004. Animals appeared to have reduced rates of daily movement starting approximately in mid to late December and stretching until late February. Similarly, most animals appeared to have very reduced rates of movement from the beginning of May to the end of June indicating that this is their calving period (includes both parturition as well as the period immediately after parturition. Thus the over-wintering range was assumed to be where the animals were from mid-December to late February and the calving range was defined as the area they were in from the beginning of May to the end of June. Individual home-ranges were typically large, the mean 90% kernel home range for 2004 - 2007 was 41 579 km2. Over wintering areas and calving areas were small when compared to annual home-range size and reflect the reduced rates of movement during these time periods. Female caribou show site fidelity to calving grounds, using the same core areas year after year. However, the same level of site fidelity was not observed in over-wintering areas. The caribou in the James Bay lowlands display behaviours that are characteristic of both the forest-tundra and forest-forest ecotypes which may warrant the reconsideration of the validity of proposed ecotypes with respect to protection under species-at-risk legislation.

  3. Simulation of Snow Processes Beneath a Boreal Scots Pine Canopy

    Institute of Scientific and Technical Information of China (English)

    LI Weiping; LUO Yong; XIA Kun; LIU Xin

    2008-01-01

    A physically-based multi-layer snow model Snow-Atmosphere-Soil-Transfer scheme (SAST) and a land surface model Biosphere-Atmosphere Transfer Scheme (BATS) were employed to investigate how boreal forests influence snow accumulation and ablation under the canopy. Mass balance and energetics of snow beneath a Scots pine canopy in Finland at different stages of the 2003-2004 and 2004-2005 snow seasons are analyzed. For the fairly dense Scots pine forest, drop-off of the canopy-intercepted snow contributes, in some cases, twice as much to the underlying snowpack as the direct throughfall of snow. During early winter snow melting, downward turbulent sensible and condensation heat fluxes play a dominant role together with downward net longwave radiation. In the final stage of snow ablation in middle spring, downward net all-wave radiation dominates the snow melting. Although the downward sensible heat flux is comparable to the net solar radiation during this period, evaporative cooling of the melting snow surface makes the turbulent heat flux weaker than net radiation. Sensitivities of snow processes to leaf area index (LAI) indicate that a denser canopy speeds up early winter snowmelt, but also suppresses melting later in the snow season. Higher LAI increases the interception of snowfall, therefore reduces snow accumulation under the canopy during the snow season; this effect and the enhancement of downward longwave radiation by denser foliage outweighs the increased attenuation of solar radiation, resulting in earlier snow ablation under a denser canopy. The difference in sensitivities to LAI in two snow seasons implies that the impact of canopy density on the underlying snowpack is modulated by interannual variations of climate regimes.

  4. Eastward propagating MJO during boreal summer and Indian monsoon droughts

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Susmitha; Sahai, A.K.; Goswami, B.N. [Indian Institute of Tropical Meteorology, Climate and Global Modeling Division, Pune (India)

    2009-06-15

    Improved understanding of underlying mechanism responsible for Indian summer monsoon (ISM) droughts is important due to their profound socio-economic impact over the region. While some droughts are associated with 'external forcing' such as the El-Nino and Southern Oscillation (ENSO), many ISM droughts are not related to any known 'external forcing'. Here, we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics. We show that most ISM droughts are associated with at least one very long break (VLB; breaks with duration of more than 10 days) and that the processes responsible for VLBs may also be the mechanism responsible for ISM droughts. Our analysis also reveals that all extended monsoon breaks (whether co-occurred with El-Nino or not) are associated with an eastward propagating Madden-Julian Oscillation (MJO) in the equatorial Indian Ocean and western Pacific extending to the dateline and westward propagating Rossby waves between 10 and 25 N. The divergent Rossby wave associated with the dry phase of equatorial convection propagates westward towards Indian land, couple with the northward propagating dry phase and leads to the sustenance of breaks. Thus, the propensity of eastward propagating MJO during boreal summer is largely the cause of monsoon droughts. While short breaks are not accompanied by westerly wind events (WWE) over equatorial western Pacific favorable for initiating air-sea interaction, all VLBs are accompanied by sustained WWE. The WWEs associated with all VLB during 1975-2005 initiate air-sea interaction on intraseasonal time scale, extend the warm pool eastward allowing the convectively coupled MJO to propagate further eastward and thereby sustaining the divergent circulation over India and the monsoon break. The ocean-atmosphere coupling on interannual time scale (such as El-Nino) can also produce VLB, but not necessary. (orig.)

  5. Riparian zone controls on base cation concentrations in boreal streams

    Directory of Open Access Journals (Sweden)

    J. L. J. Ledesma

    2013-01-01

    Full Text Available Forest riparian zones are a major in control of surface water quality. Base cation (BC concentrations, fluxes, and cycling in the riparian zone merit attention because of increasing concern of negative consequences for re-acidification of surface waters from future climate and forest harvesting scenarios. We present a two-year study of BC and silica (Si flow-weighted concentrations from 13 riparian zones and 14 streams in a boreal catchment in northern Sweden. The Riparian Flow-Concentration Integration Model (RIM was used to estimate riparian zone flow-weighted concentrations and tested to predict the stream flow-weighted concentrations. Spatial variation in BC and Si concentrations as well as in flow-weighted concentrations was related to differences in Quaternary deposits, with the largest contribution from lower lying silty sediments and the lowest contribution from wetland areas higher up in the catchment. Temporal stability in the concentrations of most elements, a remarkably stable Mg / Ca ratio in the soil water and a homogeneous mineralogy suggest that the stable patterns found in the riparian zones are a result of distinct mineralogical upslope groundwater signals integrating the chemical signals of biological and chemical weathering. Stream water Mg / Ca ratio indicates that the signal is subsequently maintained in the streams. RIM gave good predictions of Ca, Mg, and Na flow-weighted concentrations in headwater streams. The difficulty in modelling K and Si suggests a stronger biogeochemical influence on these elements. The observed chemical dilution effect with flow in the streams was related to variation in groundwater levels and element concentration profiles in the riparian zones. This study provides a first step toward specific investigations of the vulnerability of riparian zones to changes induced by forest management or climate change, with focus on BC or other compounds.

  6. Modeling Anthropogenic Fire Occurrence in the Boreal Forest of China Using Logistic Regression and Random Forests

    Directory of Open Access Journals (Sweden)

    Futao Guo

    2016-10-01

    Full Text Available Frequent and intense anthropogenic fires present meaningful challenges to forest management in the boreal forest of China. Understanding the underlying drivers of human-caused fire occurrence is crucial for making effective and scientifically-based forest fire management plans. In this study, we applied logistic regression (LR and Random Forests (RF to identify important biophysical and anthropogenic factors that help to explain the likelihood of anthropogenic fires in the Chinese boreal forest. Results showed that the anthropogenic fires were more likely to occur at areas close to railways and were significantly influenced by forest types. In addition, distance to settlement and distance to road were identified as important predictors for anthropogenic fire occurrence. The model comparison indicated that RF had greater ability than LR to predict forest fires caused by human activity in the Chinese boreal forest. High fire risk zones in the study area were identified based on RF, where we recommend increasing allocation of fire management resources.

  7. Northeastern North America as a potential refugium for boreal forests in a warming climate.

    Science.gov (United States)

    D'Orangeville, L; Duchesne, L; Houle, D; Kneeshaw, D; Côté, B; Pederson, N

    2016-06-17

    High precipitation in boreal northeastern North America could help forests withstand the expected temperature-driven increase in evaporative demand, but definitive evidence is lacking. Using a network of tree-ring collections from 16,450 stands across 583,000 km(2) of boreal forests in Québec, Canada, we observe a latitudinal shift in the correlation of black spruce growth with temperature and reduced precipitation, from negative south of 49°N to largely positive to the north of that latitude. Our results suggest that the positive effect of a warmer climate on growth rates and growing season length north of 49°N outweighs the potential negative effect of lower water availability. Unlike the central and western portions of the continent's boreal forest, northeastern North America may act as a climatic refugium in a warmer climate.