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Sample records for boreal forest soil

  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. 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...

  3. Sorption of niobium on boreal forest soil

    Energy Technology Data Exchange (ETDEWEB)

    Soederlund, Mervi; Hakanen, Martti; Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry

    2015-07-01

    The sorption of niobium (Nb) was investigated on humus and mineral soil samples taken from various depths of a four-metre deep forest soil pit on Olkiluoto Island, southwestern Finland. Mass distribution coefficients, K{sub d}, were determined in batch sorption tests. The steady state of Nb sorption was observed in the mineral soil samples already after one week of equilibration, and sorption decreased with depth from a very high value of 185000 mL/g at 0.7 m to 54000 mL/g at 3.4 m. The reason behind this decrease is probably the tenfold reduction in the specific surface area of the soil at the same depth range. Distribution coefficients were clearly lower in the humus layer (1000 mL/g). The K{sub d} values determined in pure water at a pH range of 4.7-6.5 were at a high level (above 55000 mL/g), but decreased dramatically above pH 6.5, corresponding to the change in the major Nb species from the neutral Nb(OH){sub 5} to the low-sorbing anionic Nb(OH){sub 6}{sup -} and Nb(OH){sub 7}{sup 2-}. However, the K{sub d} values in the model soil solution were in the slightly alkaline range an order of magnitude higher than in pure water, which is probably caused by the formation of calcium niobate surface precipitate or electrostatic interaction between surface-sorbed calcium and solute Nb. Among nine soil constituent minerals kaolinite performed best in retaining Nb in both pure water and model soil solution at pH 8, whereas potassium feldspar showed the poorest sorption. The K{sub d} value for kaolinite was above 500000 mL/g in both solutions, while the respective potassium feldspar values were in the range of 120-220 mL/g.

  4. 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

  5. Evaporation Dynamics of Moss and Bare Soil in Boreal Forests

    Science.gov (United States)

    Dempster, S.; Young, J. M.; Barron, C. G.; Bolton, W. R.

    2013-12-01

    Evaporation dynamics of mosses is a critical process in boreal and arctic systems and represents a key uncertainty in hydrology and climate models. At this point, moss evaporation is not well quantified at the plot or landscape scale. Relative to bare soil or litter evaporation, moss evaporation can be challenging to predict because the water flux is not isolated to the moss surface. Evaporation can originate from nearly 10 cm below the surface. Some mosses can wick moisture from even deeper than 10 cm, which subsequently evaporates. The goal of this study was to use field measurements to quantify the moss evaporation dynamics in a coniferous forest relative to bare ground or litter evaporation dynamics in a deciduous forest in Interior Alaska. Measurements were made in two ecosystem types within the boreal forest of Interior Alaska: a deciduous forest devoid of moss and a coniferous forest with a thick moss layer. A small clear chamber was attached to a LiCor 840 infrared gas analyzer in a closed loop system with a low flow rate. Water fluxes were measured for ~ 90 seconds on each plot in dry and wet soil and moss conditions. Additional measurements included: soil temperature, soil moisture, air temperature, barometric pressure, dew point, relative humidity, and wind speed. Thermal infrared images were also captured in congruence with water flux measurements to determine skin temperature. We found that the moss evaporation rate was over 100% greater than the soil evaporation rate (0.057 g/min vs. 0.024 g/min), and evaporation rates in both systems were most strongly driven by relative humidity and surface temperature. Surface temperature was lower at the birch site than the black spruce site because trees shade the surface beneath the birch. High fluxes associated with high water content were sustained for a longer period of time over the mosses compared to the bare soil. The thermal IR data showed that skin temperature lagged the evaporation flux, such that the

  6. The effect of fire intensity on soil respiration in Siberia boreal forest

    Science.gov (United States)

    S. Baker; A. V. Bogorodskaya

    2010-01-01

    Russian boreal forests have an annual wildfire activity averaging 10 to 20 million ha, which has increased in recent years. This wildfire activity, in response to changing climate has the potential to significantly affect the carbon storage capacity of Siberian forests. A better understanding of the effect of fire on soil respiration rates in the boreal forest of...

  7. Atmospheric nitrous oxide uptake in boreal spruce forest soil

    Science.gov (United States)

    Siljanen, Henri; Welti, Nina; Heikkinen, Juha; Biasi, Christina; Martikainen, Pertti

    2017-04-01

    Nitrous oxide (N2O) uptake from the atmosphere has been found in forest soils but environmental factors controlling the uptake and its atmospheric impact are poorly known. We measured N2O fluxes over growing season in a boreal spruce forest having control plots and plots with long nitrogen fertilization history. Also methane (CH4) fluxes were measured to compare the atmospheric impact of N2O and CH4fluxes. Soil chemical and physical characteristics and climatic conditions were measured as background data. Nitrous oxide consumption and uptake mechanisms were measured in complementary laboratory incubation experiments using stable isotope approaches. Gene transcript numbers of nitrous oxide reductase (nosZ) I and II genes were quantified along the incubation with elevated N2O atmosphere. The spruce forests without fertilization history showed highest N2O uptake rates whereas pine forest had low emissions. Nitrous oxide uptake correlated positively with soil moisture, high soil silt content, and low temperature. Nitrous oxide uptake varied seasonally, being highest in spring and autumn when temperature was low and water content was high. The spruce forest was sink for CH4.Methane fluxes were decoupled from the N2O fluxes (i.e. when the N2O uptake was high the CH4 uptake was low). By using GWP approach, the cooling effect of N2O uptake was on average 30% of the cooling effect of CH4 uptake in spruce forest without fertilization. Anoxic conditions promoted higher N2O consumption rates in all soils. Gene transcription of nosZ-I genes were activated at beginning of the incubation. However, atypical/clade-II nosZ was not detected. These results suggests, that also N2O uptake rates have to be considered when accounting for the GHG budget of spruce forests.

  8. Boreal forests

    Energy Technology Data Exchange (ETDEWEB)

    Essen, P.A.; Ericson, L. [Univ. of Umeaa, Dept. of Ecological Botany, Umeaa (Sweden); Ehnstroem, B. [Swedish Univ., of Agricultural Sciences, Swedish Threatened Species Unit, Uppsala (Sweden); Sjoeberg, K. [Swedish Univ. of Agricultural Sciences, Dept. of Animal Ecology, Umeaa (Sweden)

    1997-10-01

    We review patterns and processes important for biodiversity in the Fennoscandian boreal forest, describe man`s past and present impact and outline a strategy for conservation. Natural disturbances, particularly forest fire and gap formation, create much of the structural and functional diversity in forest ecosystems. Several boreal plants and animals are adapted to fire regimes. In contrast, many organisms (epiphytic lichens, fungi, invertebrates) require stable conditions with long continuity in canopy cover. The highly mechanized and efficient Fennoscandian forest industry has developed during the last century. The result is that most natural forest has been lost and that several hundreds of species, mainly cryptograms and invertebrates, are threatened. The forestry is now in a transition from exploitation to sustainable production and has recently incorporated some measures to protect the environment. Programmes for maintaining biodiversity in the boreal forest should include at least three parts. First, the system of forest reserves must be significantly improved through protection of large representative ecosystems and key biotopes that host threatened species. Second, we must restore ecosystem properties that have been lost or altered. Natural disturbance regimes must be allowed to operate or be imitated, for example by artificial fire management. Stand-level management should particularly increase the amount of coarse woody debris, the number of old deciduous trees and large, old conifers, by using partial cutting. Third, natural variation should also be mimicked at the landscape level, for example, by reducing fragmentation and increasing links between landscape elements. Long-term experiments are required to evaluate the success of different management methods in maintaining biodiversity in the boreal forest. (au) 260 refs.

  9. Soil concentrations and soil-atmosphere exchange of alkylamines in a boreal Scots pine forest

    Science.gov (United States)

    Kieloaho, Antti-Jussi; Pihlatie, Mari; Launiainen, Samuli; Kulmala, Markku; Riekkola, Marja-Liisa; Parshintsev, Jevgeni; Mammarella, Ivan; Vesala, Timo; Heinonsalo, Jussi

    2017-03-01

    Alkylamines are important precursors in secondary aerosol formation in the boreal forest atmosphere. To better understand the behavior and sources of two alkylamines, dimethylamine (DMA) and diethylamine (DEA), we estimated the magnitudes of soil-atmosphere fluxes of DMA and DEA using a gradient-diffusion approximation based on measured concentrations in soil solution and in the canopy air space. The ambient air concentration of DMA used in this study was a sum of DMA and ethylamine. To compute the amine fluxes, we first estimated the soil air space concentration from the measured soil solution amine concentration using soil physical (temperature, soil water content) and chemical (pH) state variables. Then, we used the resistance analogy to account for gas transport mechanisms in the soil, soil boundary layer, and canopy air space. The resulting flux estimates revealed that the boreal forest soil with a typical long-term mean pH 5.3 is a possible source of DMA (170 ± 51 nmol m-2 day-1) and a sink of DEA (-1.2 ± 1.2 nmol m-2 day-1). We also investigated the potential role of fungi as a reservoir for alkylamines in boreal forest soil. We found high DMA and DEA concentrations both in fungal hyphae collected from field humus samples and in fungal pure cultures. The highest DMA and DEA concentrations were found in fungal strains belonging to decay and ectomycorrhizal fungal groups, indicating that boreal forest soil and, in particular, fungal biomass may be important reservoirs for these alkylamines.

  10. 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.

  11. Sorption and speciation of selenium in boreal forest soil.

    Science.gov (United States)

    Söderlund, Mervi; Virkanen, Juhani; Holgersson, Stellan; Lehto, Jukka

    2016-11-01

    Sorption and speciation of selenium in the initial chemical forms of selenite and selenate were investigated in batch experiments on humus and mineral soil samples taken from a 4-m deep boreal forest soil excavator pit on Olkiluoto Island, on the Baltic Sea coast in southwestern Finland. The HPLC-ICP-MS technique was used to monitor any possible transformations in the selenium liquid phase speciation and to determine the concentrations of selenite and selenate in the samples for calculation of the mass distribution coefficient, Kd, for both species. Both SeO3(2-) and SeO4(2-) proved to be resistant forms in the prevailing soil conditions and no changes in selenium liquid phase speciation were seen in the sorption experiments in spite of variations in the initial selenium species, incubation time or conditions, pH, temperature or microbial activity. Selenite sorption on the mineral soil increased with time in aerobic conditions whilst the opposite trend was seen for the anaerobic soil samples. Selenite retention correlated with the contents of organic matter and weakly crystalline oxides of aluminum and iron, solution pH and the specific surface area. Selenate exhibited poorer sorption on soil than selenite and on average the Kd values were 27-times lower. Mineral soil was more efficient in retaining selenite and selenate than humus, implicating the possible importance of weakly crystalline aluminum and iron oxides for the retention of oxyanions in Olkiluoto soil. Sterilization of the soil samples decreased the retention of selenite, thus implying some involvement of soil microbes in the sorption processes or a change in sample composition, but it produced no effect for selenate. There was no sorption of selenite by quartz, potassium feldspar, hornblende or muscovite. Biotite showed the best retentive properties for selenite in the model soil solution at about pH 8, followed by hematite, plagioclase and chlorite. The Kd values for these minerals were 18, 14, 8 and 7

  12. Vertical and seasonal dynamics of fungal communities in boreal Scots pine forest soil.

    Science.gov (United States)

    Santalahti, Minna; Sun, Hui; Jumpponen, Ari; Pennanen, Taina; Heinonsalo, Jussi

    2016-11-01

    Fungal communities are important for carbon (C) transformations in boreal forests that are one of the largest C pools in terrestrial ecosystems, warranting thus further investigation of fungal community dynamics in time and space. We investigated fungal diversity and community composition seasonally and across defined soil horizons in boreal Scots pine forest in Finland using 454 pyrosequencing. We collected a total of 120 samples from five vertical soil horizons monthly from March to October; in March, under snow. Boreal forest soil generally harbored diverse fungal communities across soil horizons. The communities shifted drastically and rapidly over time. In late winter, saprotrophs dominated the community and were replaced by ectomycorrhizal fungi during the growing season. Our studies are among the first to dissect the spatial and temporal dynamics in boreal forest ecosystems and highlights the ecological importance of vertically distinct communities and their rapid seasonal dynamics. As climate change is predicted to result in warmer and longer snow-free winter seasons, as well as increase the rooting depth of trees in boreal forest, the seasonal and vertical distribution of fungal communities may change. These changes are likely to affect the organic matter decomposition by the soil-inhabiting fungi and thus alter organic C pools. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  13. Climate Warming Can Increase Soil Carbon Fluxes Without Decreasing Soil Carbon Stocks in Boreal Forests

    Science.gov (United States)

    Ziegler, S. E.; Benner, R. H.; Billings, S. A.; Edwards, K. A.; Philben, M. J.; Zhu, X.; Laganiere, J.

    2016-12-01

    Ecosystem C fluxes respond positively to climate warming, however, the net impact of changing C fluxes on soil organic carbon (SOC) stocks over decadal scales remains unclear. Manipulative studies and global-scale observations have informed much of the existing knowledge of SOC responses to climate, providing insights on relatively short (e.g. days to years) and long (centuries to millennia) time scales, respectively. Natural climate gradient studies capture integrated ecosystem responses to climate on decadal time scales. Here we report the soil C reservoirs, fluxes into and out of those reservoirs, and the chemical composition of inputs and soil organic matter pools along a mesic boreal forest climate transect. The sites studied consist of similar forest composition, successional stage, and soil moisture but differ by 5.2°C mean annual temperature. Carbon fluxes through these boreal forest soils were greatest in the lowest latitude regions and indicate that enhanced C inputs can offset soil C losses with warming in these forests. Respiration rates increased by 55% and the flux of dissolved organic carbon from the organic to mineral soil horizons tripled across this climate gradient. The 2-fold increase in litterfall inputs to these soils coincided with a significant increase in the organic horizon C stock with warming, however, no significant difference in the surface mineral soil C stocks was observed. The younger mean age of the mineral soil C ( 70 versus 330 YBP) provided further evidence for the greater turnover of SOC in the warmer climate soils. In spite of these differences in mean radiocarbon age, mineral SOC exhibited chemical characteristics of highly decomposed material across all regions. In contrast with depth trends in soil OM diagenetic indices, diagenetic shifts with latitude were limited to increases in C:N and alkyl to O-alkyl ratios in the overlying organic horizons in the warmer relative to the colder regions. These data indicate that the

  14. Tree species partition N uptake by soil depth in boreal forests.

    Science.gov (United States)

    Houle, D; Moore, J D; Ouimet, R; Marty, C

    2014-05-01

    It is recognized that the coexistence of herbaceous species in N-depleted habitats can be facilitated by N partitioning; however, the existence of such a phenomenon for trees has not yet been demonstrated. Here, we show from both foliage and soil 15N natural abundance values and from a 12-year in situ 15N addition experiment, that black spruce (Picea mariana) and jack pine (Pinus banksiana), two widespread species of the Canadian boreal forest, take up N at different depths. While black spruce takes up N from the organic soil, jack pine acquires it deeper within the highly N-depleted mineral soil. Systematic difference in foliar 15N natural abundance between the two species across seven sites distributed throughout the eastern Canadian boreal forest shows that N spatial partitioning is a widespread phenomenon. Distinct relationships between delta15N and N concentration in leaves of both species further emphasize their difference in N acquisition strategies. This result suggests that such complementary mechanisms of N acquisition could facilitate tree species coexistence in such N-depleted habitats and could contribute to the positive biodiversity-productivity relationship recently revealed for the eastern Canadian boreal forest, where jack pine is present. It also has implications for forest management and provides new insights to interpret boreal forest regeneration following natural or anthropogenic perturbations.

  15. Changes in fungal communities along a boreal forest soil fertility gradient.

    Science.gov (United States)

    Sterkenburg, Erica; Bahr, Adam; Brandström Durling, Mikael; Clemmensen, Karina E; Lindahl, Björn D

    2015-09-01

    Boreal forests harbour diverse fungal communities with decisive roles in decomposition and plant nutrition. Although changes in boreal plant communities along gradients in soil acidity and nitrogen (N) availability are well described, less is known about how fungal taxonomic and functional groups respond to soil fertility factors. We analysed fungal communities in humus and litter from 25 Swedish old-growth forests, ranging from N-rich Picea abies stands to acidic and N-poor Pinus sylvestris stands. 454-pyrosequencing of ITS2 amplicons was used to analyse community composition, and biomass was estimated by ergosterol analysis. Fungal community composition was significantly related to soil fertility at the levels of species, genera/orders and functional groups. Ascomycetes dominated in less fertile forests, whereas basidiomycetes increased in abundance in more fertile forests, both in litter and humus. The relative abundance of mycorrhizal fungi in the humus layer remained high even in the most fertile soils. Tolerance to acidity and nitrogen deficiency seems to be of greater importance than plant carbon (C) allocation patterns in determining responses of fungal communities to soil fertility, in old-growth boreal forests. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  16. 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

  17. The impact of clearcutting in boreal forests of Russia on soils: A review

    Science.gov (United States)

    Dymov, A. A.

    2017-07-01

    Data on the impact of tree logging in boreal forests of Russia on soils are systematized. Patterns of soil disturbances and transformation of microclimatic parameters within clearcutting areas are discussed. Changes in the conditions of pedogenesis in secondary forests are analyzed. It is suggested that the changes in forest soils upon reforestation of clearcutting areas might be considered as specific post-logging soil successions. Data characterizing changes in the thickness of litter horizons and in the intensity of elementary pedogenic processes, acidity, and the content of exchangeable bases in soils of clearcutting areas in the course of their natural reforestation are considered. The examples of human-disturbed (turbated) soil horizons and newly formed anthropogenic soils on clearcutting areas are described. It is suggested that the soils on mechanically disturbed parts of clearcutting areas can be separated as a specific group of detritus turbozems.

  18. Soil organic matter composition and quality across fire severity gradients in coniferous and deciduous forests of the southern boreal region

    Science.gov (United States)

    Jessica R. Miesel; William C. Hockaday; Randy Kolka; Philip A. Townsend

    2015-01-01

    Recent patterns of prolonged regional drought in southern boreal forests of the Great Lakes region, USA, suggest that the ecological effects of disturbance by wildfire may become increasingly severe. Losses of forest soil organic matter (SOM) during fire can limit soil nutrient availability and forest regeneration. These processes are also influenced by the composition...

  19. 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...

  20. Radionuclide transport along a boreal hill slope - elevated soil water concentrations in riparian forest soils

    Energy Technology Data Exchange (ETDEWEB)

    Lidman, Fredrik; Boily, Aasa; Laudon, Hjalmar [Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences, 901 83 Umeaa (Sweden); Koehler, Stephan J. [Dept. of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, P.O. 7050, 750 07 Uppsala (Sweden)

    2014-07-01

    The transport of radionuclides from forest ecosystems and out into surface waters is a crucial process for understanding the long-term fate of radionuclides in the boreal landscape. Boreal forests are typically dominated by podzol soils, but the streams draining the forests are often lined by highly organic, often peat-like soils, which the radionuclides must pass through in order to reach the stream. This so-called riparian zone therefore represents a fundamentally different biogeochemical environment than ordinary forest soils, e.g. by exhibiting significantly lower pH and higher concentrations of organic colloids, which significantly can affect the mobility of many radionuclides. Since the riparian zone is the last terrestrial environment that the groundwater is in contact with before it enters the stream, previous research has demonstrated its profound impact on the stream water chemistry. Hence, the riparian soils should also be important for the transport and accumulation of radionuclides. Therefore, soil water was sampled using suction lysimeters installed at different depths along a 22 m long forested hill slope transect in northern Sweden, following the flow pathway of the groundwater from the uphill podzol to the riparian zone near the stream channel. The analyses included a wide range of hydrochemical parameters and many radiologically important elements, e.g. U, Th, Ni, C, Sr, Cs, REEs and Cl. The sampling was repeated ten times throughout a year in order to also capture the temporal variability of the soil water chemistry. The water chemistry of the investigated transect displayed a remarkable change as the groundwater approached the stream channel. Strongly increased concentrations of many elements were observed in the riparian soils. For instance, the concentrations of Th were more than 100 times higher than in the riparian zone than in the uphill forest, suggesting that the riparian zone may be a hotspot for radionuclide accumulation. The reason

  1. Effects of Dolomitic Limestone Application on Zinc Speciation in Boreal Forest Smelter-Contaminated Soils.

    Science.gov (United States)

    Hamilton, Jordan G; Farrell, Richard E; Chen, Ning; Reid, Joel; Feng, Renfei; Peak, Derek

    2016-11-01

    Anthropogenic activities at the HudBay Minerals, Inc., Flin Flon (Manitoba, Canada) mining and processing facility have severely affected the surrounding boreal forest ecosystem. Soil contamination occurred via a combination of metal and sulfuric acid deposition and has resulted in forest dieback and ineffective natural recovery. A community-led effort to revegetate areas of the landscape through the application of a dolomitic limestone has been met with varied success. Zinc (Zn) speciation has shown to be closely linked to the presence or absence of an invasive metal-tolerant grass species, with soils being broadly classed into two revegetation response groups. Group I, characterized by the absence of metal-tolerant grasses, and group II, characterized by the presence of metal-tolerant grasses. The systematic approach used to lime areas of the landscape produced a liming chronosequence for each group. This study used a combination of X-ray absorption spectroscopy, X-ray fluorescence mapping, and X-ray diffraction techniques to determine the effect of liming on Zn speciation in these chronosequences. Liming group I soils resulted in the formation of a neo-phase Zn-Al-hydroxy interlayer coprecipitate and subsequent rapid boreal forest revegetation. The effect of liming on Zn speciation on the group II soils resulted in a gradual transition of increasingly stable adsorption species, culminating with a stable Zn-Al-layered double hydroxide precipitate. Boreal forest vegetation has failed to recolonize group II soils during the study. However, the formation of the layered double hydroxide species resulted in a significant reduction in CaCl-extractable Zn. Further research is required to determine how to promote the revegetation of these soils. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  2. Boreal coniferous forest density leads to significant variations in soil physical and geochemical properties

    Science.gov (United States)

    Bastianelli, Carole; Ali, Adam A.; Beguin, Julien; Bergeron, Yves; Grondin, Pierre; Hély, Christelle; Paré, David

    2017-07-01

    At the northernmost extent of the managed forest in Quebec, Canada, the boreal forest is currently undergoing an ecological transition between two forest ecosystems. Open lichen woodlands (LW) are spreading southward at the expense of more productive closed-canopy black spruce-moss forests (MF). The objective of this study was to investigate whether soil properties could distinguish MF from LW in the transition zone where both ecosystem types coexist. This study brings out clear evidence that differences in vegetation cover can lead to significant variations in soil physical and geochemical properties.Here, we showed that soil carbon, exchangeable cations, and iron and aluminium crystallinity vary between boreal closed-canopy forests and open lichen woodlands, likely attributed to variations in soil microclimatic conditions. All the soils studied were typical podzolic soil profiles evolved from glacial till deposits that shared a similar texture of the C layer. However, soil humus and the B layer varied in thickness and chemistry between the two forest ecosystems at the pedon scale. Multivariate analyses of variance were used to evaluate how soil properties could help distinguish the two types at the site scale. MF humus (FH horizons horizons composing the O layer) showed significantly higher concentrations of organic carbon and nitrogen and of the main exchangeable base cations (Ca, Mg) than LW soils. The B horizon of LW sites held higher concentrations of total Al and Fe oxides and particularly greater concentrations of inorganic amorphous Fe oxides than MF mineral soils, while showing a thinner B layer. Overall, our results show that MF store three times more organic carbon in their soils (B+FH horizons, roots apart) than LW. We suggest that variations in soil properties between MF and LW are linked to a cascade of events involving the impacts of natural disturbances such as wildfires on forest regeneration that determines the vegetation structure (stand density

  3. 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

  4. Effect of climate change on soil temperature in Swedish boreal forests.

    Science.gov (United States)

    Jungqvist, Gunnar; Oni, Stephen K; Teutschbein, Claudia; Futter, Martyn N

    2014-01-01

    Complex non-linear relationships exist between air and soil temperature responses to climate change. Despite its influence on hydrological and biogeochemical processes, soil temperature has received less attention in climate impact studies. Here we present and apply an empirical soil temperature model to four forest sites along a climatic gradient of Sweden. Future air and soil temperature were projected using an ensemble of regional climate models. Annual average air and soil temperatures were projected to increase, but complex dynamics were projected on a seasonal scale. Future changes in winter soil temperature were strongly dependent on projected snow cover. At the northernmost site, winter soil temperatures changed very little due to insulating effects of snow cover but southern sites with little or no snow cover showed the largest projected winter soil warming. Projected soil warming was greatest in the spring (up to 4°C) in the north, suggesting earlier snowmelt, extension of growing season length and possible northward shifts in the boreal biome. This showed that the projected effects of climate change on soil temperature in snow dominated regions are complex and general assumptions of future soil temperature responses to climate change based on air temperature alone are inadequate and should be avoided in boreal regions.

  5. Soil moisture sensitivity of autotrophic and heterotrophic forest floor respiration in boreal xeric pine and mesic spruce forests

    Science.gov (United States)

    Ťupek, Boris; Launiainen, Samuli; Peltoniemi, Mikko; Heikkinen, Jukka; Lehtonen, Aleksi

    2016-04-01

    Litter decomposition rates of the most process based soil carbon models affected by environmental conditions are linked with soil heterotrophic CO2 emissions and serve for estimating soil carbon sequestration; thus due to the mass balance equation the variation in measured litter inputs and measured heterotrophic soil CO2 effluxes should indicate soil carbon stock changes, needed by soil carbon management for mitigation of anthropogenic CO2 emissions, if sensitivity functions of the applied model suit to the environmental conditions e.g. soil temperature and moisture. We evaluated the response forms of autotrophic and heterotrophic forest floor respiration to soil temperature and moisture in four boreal forest sites of the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) by a soil trenching experiment during year 2015 in southern Finland. As expected both autotrophic and heterotrophic forest floor respiration components were primarily controlled by soil temperature and exponential regression models generally explained more than 90% of the variance. Soil moisture regression models on average explained less than 10% of the variance and the response forms varied between Gaussian for the autotrophic forest floor respiration component and linear for the heterotrophic forest floor respiration component. Although the percentage of explained variance of soil heterotrophic respiration by the soil moisture was small, the observed reduction of CO2 emissions with higher moisture levels suggested that soil moisture response of soil carbon models not accounting for the reduction due to excessive moisture should be re-evaluated in order to estimate right levels of soil carbon stock changes. Our further study will include evaluation of process based soil carbon models by the annual heterotrophic respiration and soil carbon stocks.

  6. Characterizing Zinc Speciation in Soils from a Smelter-Affected Boreal Forest Ecosystem.

    Science.gov (United States)

    Hamilton, Jordan G; Farrell, Richard E; Chen, Ning; Feng, Renfei; Reid, Joel; Peak, Derek

    2016-03-01

    HudBay Minerals, Inc., has mined and/or processed Zn and Cu ore in Flin Flon, MB, Canada, since the 1930s. The boreal forest ecosystem and soil surrounding these facilities have been severely impacted by mixed metal contamination and HSO deposition. Zinc is one of the most prevalent smelter-derived contaminants and has been identified as a key factor that may be limiting revegetation. Metal toxicity is related to both total concentrations and speciation; therefore, X-ray absorption spectroscopy and X-ray fluorescence mapping were used to characterize Zn speciation in soils throughout the most heavily contaminated areas of the landscape. Zinc speciation was linked to two distinct soil types. Group I soils consist of exposed soils in weathered positions of bedrock outcrops with Zn present primarily as franklinite, a (ZnFeO) spinel mineral. Group II soils are stabilized by an invasive metal-tolerant grass species, with Zn found as a mixture of octahedral (Fe oxides) and tetrahedral Mn oxides) adsorption complexes with a franklinite component. Soil erosion influences Zn speciation through the redistribution of Zn and soil particulates from Group I landscape positions to Group II soils. Despite Group II soils having the highest concentrations of CaCl-extractable Zn, they support metal-tolerant plant growth. The metal-tolerant plants are probably preferentially colonizing these areas due to better soil and nutrient conditions as a result of soil deposition from upslope Group I areas. Zinc concentration and speciation appears to not influence the colonization by metal-tolerant grasses, but the overall soil properties and erosion effects prevent the revegetation by native boreal forest species. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  7. Contribution of understorey vegetation and soil processes to boreal forest isoprenoid exchange

    Science.gov (United States)

    Mäki, Mari; Heinonsalo, Jussi; Hellén, Heidi; Bäck, Jaana

    2017-03-01

    Boreal forest floor emits biogenic volatile organic compounds (BVOCs) from the understorey vegetation and the heterogeneous soil matrix, where the interactions of soil organisms and soil chemistry are complex. Earlier studies have focused on determining the net exchange of VOCs from the forest floor. This study goes one step further, with the aim of separately determining whether the photosynthesized carbon allocation to soil affects the isoprenoid production by different soil organisms, i.e., decomposers, mycorrhizal fungi, and roots. In each treatment, photosynthesized carbon allocation through roots for decomposers and mycorrhizal fungi was controlled by either preventing root ingrowth (50 µm mesh size) or the ingrowth of roots and fungi (1 µm mesh) into the soil volume, which is called the trenching approach. Isoprenoid fluxes were measured using dynamic (steady-state flow-through) chambers from the different treatments. This study aimed to analyze how important the understorey vegetation is as a VOC sink. Finally, a statistical model was constructed based on prevailing temperature, seasonality, trenching treatments, understory vegetation cover, above canopy photosynthetically active radiation (PAR), soil water content, and soil temperature to estimate isoprenoid fluxes. The final model included parameters with a statistically significant effect on the isoprenoid fluxes. The results show that the boreal forest floor emits monoterpenes, sesquiterpenes, and isoprene. Monoterpenes were the most common group of emitted isoprenoids, and the average flux from the non-trenched forest floor was 23 µg m-2 h-1. The results also show that different biological factors, including litterfall, carbon availability, biological activity in the soil, and physico-chemical processes, such as volatilization and absorption to the surfaces, are important at various times of the year. This study also discovered that understorey vegetation is a strong sink of monoterpenes. The

  8. Dominant Tree Species and Soil Type Affect the Fungal Community Structure in a Boreal Peatland Forest.

    Science.gov (United States)

    Sun, Hui; Terhonen, Eeva; Kovalchuk, Andriy; Tuovila, Hanna; Chen, Hongxin; Oghenekaro, Abbot O; Heinonsalo, Jussi; Kohler, Annegret; Kasanen, Risto; Vasander, Harri; Asiegbu, Fred O

    2016-05-01

    Boreal peatlands play a crucial role in global carbon cycling, acting as an important carbon reservoir. However, little information is available on how peatland microbial communities are influenced by natural variability or human-induced disturbances. In this study, we have investigated the fungal diversity and community structure of both the organic soil layer and buried wood in boreal forest soils using high-throughput sequencing of the internal transcribed spacer (ITS) region. We have also compared the fungal communities during the primary colonization of wood with those of the surrounding soils. A permutational multivariate analysis of variance (PERMANOVA) confirmed that the community composition significantly differed between soil types (Pstructure (Psoil nutrients (Ca [P= 0.002], Fe [P= 0.003], and P [P= 0.003]) within the site was an important factor in the fungal community composition. The species richness in wood was significantly lower than in the corresponding soil (P< 0.004). The results of the molecular identification were supplemented by fruiting body surveys. Seven of the genera of Agaricomycotina identified in our surveys were among the top 20 genera observed in pyrosequencing data. Our study is the first, to our knowledge, fungal high-throughput next-generation sequencing study performed on peatlands; it further provides a baseline for the investigation of the dynamics of the fungal community in the boreal peatlands.

  9. Testing Yasso07 and CENTURY soil C models with boreal forest soil C stocks and CO2 efflux measurements

    Science.gov (United States)

    Tupek, Boris; Peltoniemi, Mikko; Launiainen, Samuli; Kulmala, Liisa; Penttilä, Timo; Lehtonen, Aleksi

    2017-04-01

    Soil C models need further development, especially in terms of factors influencing spatial variability of soil C stocks and soil C stock changes. In this study we tested the estimates of soil C stocks and C stock changes of two widely used soil C models (Yasso07 and CENTURY) against measurements of the boreal forest soil C stock and CO2 efflux at four forest sites in Finland. In addition we evaluated the effects of using coarse versus detailed meteorological, soil, and plant litter input data on modeled monthly CO2 estimates. We found out that CO2 estimates of both models showed similar seasonal CO2 efflux pattern as the upscaled monthly measurements regardless of the fact whether the models used soil properties as input data. Winter and early summer CO2 fluxes agreed somewhat better between estimates and measurements than summer CO2 peaks and autumn CO2 levels, which were underestimated by models. Both models also underestimated equilibrium soil carbon (SOC) stocks, although SOC of CENTURY were larger than SOCs of Yasso07. CENTURY was more sensitive to variation in meteorological input data than Yasso07 and also to functional form of temperature response to decomposition. In conclusion, for modeling boreal forest soil C Yasso07 would benefit from including soil properties in the model structure, while Century would benefit from reformulation of temperature and moisture functions.

  10. Regional Assessment of soil organic matter profile distribution in the boreal forest ecosystems of Russia

    Science.gov (United States)

    Meshalkina, Joulia; Belousova, Nataliya; Vasenev, Ivan

    2015-04-01

    Boreal forest ecosystems play one of the key roles in the Global Change challenges responses. The soil carbon stocks are principal regulators of their environmental functions. Boreal forest soil cover is characterized by mutually increased spatial variability in soil organic matter content (SOMC) that one need to take into attention in its current and future environmental functions state assessment including the potential of regional soil organic matter stocks changes due to Global Change and inverse ones. Knowledge of the regional regularities in SOMC profile vertical distribution allows improving their soil environmental functions prediction land quality evaluation. More than 900 profiles of SOMC distribution were studied using the database Boreal that contains data on Russian boreal soils developed in drained conditions on loamy soil forming rocks. These soil profiles belong to seven main types of forest soils of Russian classification and six major regions of Russia. The predomination of accumulation profile type was observed for all cases. Thus the vertical distribution of OMC in the profiles of boreal soils can be described as follow: the layer of maximum OMC is replaced by the layer of dramatic OMC reduction; then the layer of minimal OMC extends up to 2.5 m. The layer of maximal OMC accumulation has the low depth of 5-15 cm. It carried out in different genetic horizons: A1, A1A2, A2, B, AB; sometimes it captures the A2B horizon or the upper part of the illuvial horizon. The OMC in this layer increases from the northern taiga to the southern taiga and from the European part of Russia to Siberia. The second layer is characterized by its depth and by the gradient of OMC decreasing. A great variety of the both parameters is observed. The layer of the sharp OMC fall most often fits with the eluvial horizons A2 or А2В or even the upper part of the Вt (textural) or Bm (metamorphic) horizons. The layer of permanently small OMC may begin in any genetic horizon

  11. Methyl Mercury Formation in Hillslope Soils of Boreal Forests: The Role of Forest Harvest and Anaerobic Microbes.

    Science.gov (United States)

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

    2016-09-06

    Final harvest (clear-cutting) of coniferous boreal forests has been shown to increase streamwater concentrations and export of the neurotoxin methyl mercury (MeHg) to freshwater ecosystems. Here, the spatial distribution of inorganic Hg and MeHg in soil as a consequence of clear-cutting is reported. A comparison of soils at similar positions along hillslopes in four 80 years old Norway spruce (Picea abies) stands (REFs) with those in four similar stands subjected to clear-cutting (CCs) revealed significantly (p forest harvest.

  12. Estimation of autotrophic soil respiration in a boreal forest using three different approaches

    Science.gov (United States)

    Kulmala, Liisa; Pumpanen, Jukka; Heinonsalo, Jussi

    2016-04-01

    It is generally challenging to separate autotrophic and heterotrophic soil respiration. The reason for these difficulties is connected with the intimate interaction of the key processes in soil. Root-associated microbes practically colonize the whole soil volume while decomposition processes occur in the same matrix. Therefore, autotrophic and heterotrophic processes cannot be separated in natural systems. However, there are several methods that can be used to better understand the dynamics of these two. A classical method is called 'trenching' where a trench is dug around a known volume of soil and the roots entering the soil are cut from the living trees thus blocking the C flow from them. The second way to separate autotrophic and heterotrophic respiration relies on the difference in the isotopic signature (13C) of plant-derived or decomposition-derived CO2. The third way to separate the sources is to study the differences in the short- and long-term temperature dependencies in CO2 soil emissions. This is possible especially in boreal forests where the biological activity has a strong seasonal cycle. We compared these three methods in an experiment conducted in a southern boreal middle-aged Scots pine stand in Finland. Our data provides a unique possibility to critically evaluate current methods for estimating autotrophic and heterotrophic soil respiration. The knowledge is needed to study further plant physiology and plant-microbe interactions in soil.

  13. Nitrous oxide uptake rates in boreal coniferous forests are associated with soil characteristics

    Science.gov (United States)

    Siljanen, Henri; Biasi, Christina; Martikainen, Pertti

    2014-05-01

    Nitrous oxide (N2O) is a strong greenhouse gas and a significant contributor to the destruction of the ozone layer. The radiative forcing of N2O is considered to be 320 more efficient than carbon dioxide.The major portion of global N2O is emitted from agricultural soils. There are studies suggesting that N2O has also a sink in forest soils. However there is relatively limited knowledge on factors controlling N2O consumption in forest soils. Hence N2O consumption was studied in boreal coniferous forests having different forest cover, soil chemical and physical structure and land-use history. The N2O consumption was measured by static chamber technique in the field across spatio-seasonal sampling design. Typical and atypical denitrifiers were quantified with nosZ functional gene marker. Additionally chemical and physical environmental parameters were analyzed to link N2O flux, microbial community and composition of soils. Nitrous oxide uptake could be associated with specific ecosystem and environmental conditions. Soil physical structure and land-use history were shown to be prior factors determining the strength of the uptake rate.

  14. Ectomycorrhizal fungi contribute to soil organic matter cycling in sub-boreal forests.

    Science.gov (United States)

    Phillips, Lori A; Ward, Valerie; Jones, Melanie D

    2014-03-01

    Soils of northern temperate and boreal forests represent a large terrestrial carbon (C) sink. The fate of this C under elevated atmospheric CO2 and climate change is still uncertain. A fundamental knowledge gap is the extent to which ectomycorrhizal fungi (EMF) and saprotrophic fungi contribute to C cycling in the systems by soil organic matter (SOM) decomposition. In this study, we used a novel approach to generate and compare enzymatically active EMF hyphae-dominated and saprotrophic hyphae-enriched communities under field conditions. Fermentation-humus (FH)-filled mesh bags, surrounded by a sand barrier, effectively trapped EMF hyphae with a community structure comparable to that found in the surrounding FH layer, at both trophic and taxonomic levels. In contrast, over half the sequences from mesh bags with no sand barrier were identified as belonging to saprotrophic fungi. The EMF hyphae-dominated systems exhibited levels of hydrolytic and oxidative enzyme activities that were comparable to or higher than saprotroph-enriched systems. The enzymes assayed included those associated with both labile and recalcitrant SOM degradation. Our study shows that EMF hyphae are likely important contributors to current SOM turnover in sub-boreal systems. Our results also suggest that any increased EMF biomass that might result from higher below-ground C allocation by trees would not suppress C fluxes from sub-boreal soils.

  15. 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.

  16. 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.

  17. 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.

  18. Effects of disturbance and vegetation type on total and methylmercury in boreal peatland and forest soils.

    Science.gov (United States)

    Braaten, Hans Fredrik Veiteberg; de Wit, Heleen A

    2016-11-01

    Mercury (Hg) concentrations in freshwater fish relates to aquatic Hg concentrations, which largely derives from soil stores of accumulated atmospheric deposition. Hg in catchment soils as a source for aquatic Hg is poorly studied. Here we test if i) peatland soils produce more methylmercury (MeHg) than forest soils; ii) total Hg (THg) concentrations in top soils are determined by atmospheric inputs, while MeHg is produced in the soils; and iii) soil disturbance promotes MeHg production. In two small boreal catchments, previously used in a paired-catchment forest harvest manipulation study, forest soils and peatlands were sampled and analysed for Hg species and additional soil chemistry. In the undisturbed reference catchment, soils were sampled in different vegetation types, of varying productivity as reflected in tree density, where historical data on precipitation and throughfall Hg and MeHg fluxes were available. Upper soil THg contents were significantly correlated to throughfall inputs of Hg, i.e. lowest in the tree-less peatland and highest in the dense spruce forest. For MeHg, top layer concentrations were similar in forest soils and peatlands, likely related to atmospheric input and local production, respectively. The local peatland MeHg production was documented through significantly higher MeHg-to-THg ratios in the deeper soil layer samples. In the disturbed catchment, soils were sampled in and just outside wheeltracks in an area impacted by forest machinery. Here, MeHg concentrations and the MeHg-to-THg ratios in the upper 5 cm were weakly significantly (p = 0.07) and significantly (p = 0.04) different in and outside of the wheeltracks, respectively, suggesting that soil disturbance promotes methylation. Differences in catchment Hg and MeHg streamwater concentrations were not explained by soil Hg and MeHg information, perhaps because hydrological pathways are a stronger determinant of streamwater chemistry than small variations in soil chemistry

  19. The Charcoal Component of Soil Organic Matter in the Boreal Forest of Western Quebec (Abitibi Region)

    Science.gov (United States)

    Preston, C. M.; Simard, M.; Kurz, W. A.; Rampley, G.; Wasylishen, R. E.; Bernard, G. M.; Bergeron, Y.; Lecomte, N.

    2009-05-01

    Despite high interest in pyrogenic carbon (PyC) as a stable and possibly major component of soil organic matter (SOM), there is surprisingly little information on production, stocks, longevity, chemical properties or ecological role of PyC in boreal forests. We define the whole range of fire-transformed biomass and SOM as pyrogenic C (PyC), black carbon (BC) as the fraction resistant to laboratory oxidation, and charcoal as that determined visually. Fire is the major disturbance in boreal forests, with panboreal production estimated at 12.7 Tg/y as solid PyC and 0.38 Tg/y as atmospheric soot (estimated as 5% and 0.15% of emissions, respectively). PyC is considered a highly-stable component of SOM, and thus should contribute to long-term C sequestration by partially offsetting C losses due to fire. Forest floor charcoal is considered to enhance N availability after fire, partly by sorbing phenolics and providing microsites for microbial activity, while other studies have indicated that BC enhances mineral soil fertility, mainly by enhancing cation exchange capacity as it oxidizes. However, studies of its ecological role in boreal forests have not sufficiently isolated charcoal effects per se from direct effects of fire. Without fire disturbance many boreal forests undergo gradual paludification, with increasing thickness of organic horizons and dominance of sphagnum moss and ericaceous shrubs. As part of extensive studies of fire history and paludification in the Abitibi region of Quebec, charcoal fragments (>2mm) were separated at 1 cm depth increments (organic horizons plus varying depths of mineral soil, 2-3 monoliths per plot) in 31 plots of black spruce (Picea mariana) and 19 of jack pine (Pinus banksiana). Plots included stands originating after high- and low-severity fires, the former defined as leaving <5 cm of organic horizon. Plots from low-severity fires (mainly black spruce, up to 229 y) generally had multiple layers of charcoal in the organic horizons

  20. 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.

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

    Science.gov (United States)

    Fan, Zhaosheng; Jastrow, Julie D; Liang, Chao; Matamala, Roser; Miller, Raymond Michael

    2013-01-01

    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.

  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. Carbon input increases microbial nitrogen demand, but not microbial nitrogen mining in boreal forest soils

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    Wild, Birgit; Alaei, Saeed; Bengtson, Per; Bodé, Samuel; Boeckx, Pascal; Schnecker, Jörg; Mayerhofer, Werner; Rütting, Tobias

    2016-04-01

    Plant primary production at mid and high latitudes is often limited by low soil N availability. It has been hypothesized that plants can indirectly increase soil N availability via root exudation, i.e., via the release of easily degradable organic compounds such as sugars into the soil. These compounds can stimulate microbial activity and extracellular enzyme synthesis, and thus promote soil organic matter (SOM) decomposition ("priming effect"). Even more, increased C availability in the rhizosphere might specifically stimulate the synthesis of enzymes targeting N-rich polymers such as proteins that store most of the soil N, but are too large for immediate uptake ("N mining"). This effect might be particularly important in boreal forests, where plants often maintain high primary production in spite of low soil N availability. We here tested the hypothesis that increased C availability promotes protein depolymerization, and thus soil N availability. In a laboratory incubation experiment, we added 13C-labeled glucose to a range of soil samples derived from boreal forests across Sweden, and monitored the release of CO2 by C mineralization, distinguishing between CO2 from the added glucose and from the native, unlabeled soil organic C (SOC). Using a set of 15N pool dilution assays, we further measured gross rates of protein depolymerization (the breakdown of proteins into amino acids) and N mineralization (the microbial release of excess N as ammonium). Comparing unamended control samples, we found a high variability in C and N mineralization rates, even when normalized by SOC content. Both C and N mineralization were significantly correlated to SOM C/N ratios, with high C mineralization at high C/N and high N mineralization at low C/N, suggesting that microorganisms adjusted C and N mineralization rates to the C/N ratio of their substrate and released C or N that was in excess. The addition of glucose significantly stimulated the mineralization of native SOC in soils

  4. Carbon allocation patterns in boreal and hemiboreal forest ecosystems along the gradient of soil fertility

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    Kriiska, Kaie; Uri, Veiko; Frey, Jane; Napa, Ülle; Kabral, Naima; Soosaar, Kaido; Rannik, Kaire; Ostonen, Ivika

    2017-04-01

    Carbon (C) allocation plays a critical role in forest ecosystem carbon cycling. Changes in C allocation alter ecosystems carbon sequestration and plant-soil-atmosphere gas exchange, hence having an impact on the climate. Currently, there is lack of reliable indicators that show the direction of C accumulation patterns in forest ecosystems on regional scale. The first objective of our study was to determine the variability of carbon allocation in hemiboreal coniferous forests along the gradient of soil fertility in Estonia. We measured C stocks and fluxes, such as litter, fine root biomass and production, soil respiration etc. in 8 stands of different site types - Scots pine (Cladonia, Vaccinium, Myrtillus, Fragaria) and Norway spruce (Polytrichum, Myrtillus, Oxalis, Calamagrostis alvar). The suitability of above- and belowground litter production (AG/BG) ratio was analysed as a carbon allocation indicator. The second aim of the study was to analyse forest C allocation patterns along the north-south gradient from northern boreal Finland to hemiboreal Estonia. Finally, C sequestration in silver birch and grey alder stands were compared with coniferous stands in order to determine the impact of tree species on carbon allocation. Preliminary results indicate that estimated AG/BG ratio (0.5 ... 3.0) tends to decrease with increasing soil organic horizon C/N ratio, indicating that in less fertile sites more carbon is allocated into belowground through fine root growth and in consequence the soil organic carbon stock increases. Similar trends were found on the north-south forest gradient. However, there was a significant difference between coniferous and broadleaf stands in C allocation patterns. Net ecosystem exchange in Estonian coniferous stands varied from -1.64 ... 3.95 t C ha-1 yr-1, whereas older stands tended to be net carbon sources.

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

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    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.

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

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    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.

  7. The carbon balance of forest soils: detectability of changes in soil carbon stocks in temperate and Boreal forests.

    Science.gov (United States)

    Conen, Frauz; Zerva, Argyro; Arrouays, Dominique; Jolivet, Claude; Jarvis, Paul G; Grace, John; Mencuccini, Maurizio

    2005-01-01

    Estimating soil carbon content as the product of mean carbon concentration and bulk density can result in considerable overestimation. Carbon concentration and soil mass need to be measured on the same sample and carbon contents calculated for each individual sample before averaging. The effect of this bias is likely to be smaller (but still greater than zero) when the primary objective is to determine stock changes over time. Variance and mean carbon content are significantly and positively related to each other, although some sites showed much higher variability than predicted by this relationship, as a likely consequence of their particular site history, forest management, and micro-topography. Because of the proportionality between mean and variance, the number of samples required to detect a fixed change in soil carbon stocks varied directly with the site mean carbon content from less than 10 to several thousands across the range of carbon stocks normally encountered in temperate and Boreal forests. This raises important questions about how to derive an optimal sampling strategy across such a varied range of conditions so as to achieve the aims of the Kyoto Protocol. Overall, on carbon-poor forest sites with little or no disturbance to the soil profile, it is possible to detect changes in total soil organic carbon over time of the order of 0.5 kg (C) m(-2) with manageable sample sizes even using simple random sampling (i.e., about 50 samples per sampling point). More efficient strategies will reveal even smaller differences. On disturbed forest sites (ploughed, windthrow) this is no longer possible (required sample sizes are much larger than 100). Soils developed on coarse aeolian sediments (sand dunes), or where buried logs or harvest residues of the previous rotation are present, can also exhibit large spatial variability in soil carbon. Generally, carbon-rich soils will always require larger numbers of samples. On these sites, simple random sampling is

  8. Variation in soil carbon dioxide efflux at two spatial scales in a topographically complex boreal forest

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    Kelsey, Katharine C.; Wickland, Kimberly P.; Striegl, Rob; Neff, Jason C.

    2012-01-01

    Carbon dynamics of high-latitude regions are an important and highly uncertain component of global carbon budgets, and efforts to constrain estimates of soil-atmosphere carbon exchange in these regions are contingent on accurate representations of spatial and temporal variability in carbon fluxes. This study explores spatial and temporal variability in soilatmosphere carbon dynamics at both fine and coarse spatial scales in a high-elevation, permafrost-dominated boreal black spruce forest. We evaluate the importance of landscape-level investigations of soil-atmosphere carbon dynamics by characterizing seasonal trends in soil-atmosphere carbon exchange, describing soil temperature-moisture-respiration relations, and quantifying temporal and spatial variability at two spatial scales: the plot scale (0–5 m) and the landscape scale (500–1000 m). Plot-scale spatial variability (average variation on a given measurement day) in soil CO2 efflux ranged from a coefficient of variation (CV) of 0.25 to 0.69, and plot-scale temporal variability (average variation of plots across measurement days) in efflux ranged from a CV of 0.19 to 0.36. Landscape-scale spatial and temporal variability in efflux was represented by a CV of 0.40 and 0.31, respectively, indicating that plot-scale spatial variability in soil respiration is as great as landscape-scale spatial variability at this site. While soil respiration was related to soil temperature at both the plot- and landscape scale, landscape-level descriptions of soil moisture were necessary to define soil respiration-moisture relations. Soil moisture variability was also integral to explaining temporal variability in soil respiration. Our results have important implications for research efforts in high-latitude regions where remote study sites make landscape-scale field campaigns challenging.

  9. Mineralization of organic matter with warming in boreal forest soils is influenced by nitrogen dynamics

    Science.gov (United States)

    Li, J.; Ziegler, S. E.; Lane, C. S.; Billings, S. A.

    2011-12-01

    Temperature is an important factor in regulating soil organic matter (SOM) decomposition, but the drivers of microbial substrate choice with changing temperature regimes remain poorly elucidated. For example, nitrogen (N) dynamics play a key role in dictating activity levels of different microbial groupings, which in turn may influence who in a microbial community is better able to take advantage of more favorable energetics in a warmer soil profile. These issues are particularly important for large SOM reservoirs, such as those in the boreal biome. To address these issues, we collected soils in organic horizons from two forested sites along the Newfoundland-Labrador Boreal Ecosystem Latitude Transect (NL-BELT) in eastern Canada. Sites differ in latitude and mean annual temperature, but are similar in forest cover and soil type. We incubated humified Oe+Oa materials and replaced Oi with low or high C:N coniferous litter possessing a distinct δ13C signature for 120 days at 15°C and 20°C. During the incubation, we assessed respiratory CO2 losses and its origin via δ13C of CO2, microbial biomass, and the activity of multiple exo-enzymes associated with the mineralization of slow-turnover and more labile substrates. As predicted by enzyme kinetics, warming positively influenced respiratory loss and the proportion of CO2 derived from more humified SOM, particularly in late stages of the incubation. We observed no interaction effect of warming and Oi C:N on respired CO2 or microbial biomass C or N in soil from either site. Oi C:N influenced respiratory loss from higher latitude soils, with lower C:N Oi input dampening respiration rates early in the incubation, and promoting it at later stages. Late in the incubation, when the positive effect of warming on CO2 release from more humified SOM was most pronounced, the warming-induced increase in phenol oxidase activity was further enhanced when Oi material had a relatively low C:N by factors of 1.87 and 17 for lower vs

  10. Hydrologic Modeling of Boreal Forest Ecosystems

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    Haddeland, I.; Lettenmaier, D. P.

    1995-01-01

    This study focused on the hydrologic response, including vegetation water use, of two test regions within the Boreal-Ecosystem-Atmosphere Study (BOREAS) region in the Canadian boreal forest, one north of Prince Albert, Saskatchewan, and the other near Thompson, Manitoba. Fluxes of moisture and heat were studied using a spatially distributed hydrology soil-vegetation-model (DHSVM).

  11. Characteristics of soil-to-plant transfer of elements relevant to radioactive waste in boreal forest

    Energy Technology Data Exchange (ETDEWEB)

    Roivainen, P.

    2011-07-01

    The use of nuclear energy generates large amounts of different types of radioactive wastes that can be accidentally released into the environment. Soil-to-plant transfer is a key process for the dispersion of radionuclides in the biosphere and is usually described by a concentration ratio (CR) between plant and soil concentrations in radioecological models. Our knowledge of the soil-to-plant transfer of many radionuclides is currently limited and concerns mainly agricultural species and temperate environments. The validity of radioecological modelling is affected by the accuracy of the assumptions and parameters used to describe soil-to-plant transfer. This study investigated the soil-to-plant transfer of six elements (cobalt (Co), molybdenum (Mo), nickel (Ni), lead (Pb), uranium (U) and zinc (Zn)) relevant to radioactive waste at two boreal forest sites and assessed the factors affecting the CR values. May lily (Maianthemum bifolium), narrow buckler fern (Dryopteris carthusiana) and blueberry (Vaccinium myrtillus) were selected as representatives of understory species, while rowan (Sorbus aucuparia) and Norway spruce (Picea abies) represented trees in this study. All the elements studied were found to accumulate in plant roots, indicating that separate CR values for root and aboveground plant parts are needed. The between-species variation in CR values was not clearly higher than the within-species variation, suggesting that the use of generic CR values for understory species and trees is justified. No linear relationship was found between soil and plant concentrations for the elements studied and a non-linear equation was found to be the best for describing the dependence of CR values on soil concentration. Thus, the commonly used assumption of a linear relationship between plant and soil concentrations may lead to underestimation of plant root uptake at low soil concentrations. Plant nutrients potassium, magnesium, manganese, phosphorus and sulphur were found to

  12. Interactions among temperature, moisture, and oxygen concentrations in controlling decomposition rates in a boreal forest soil

    Science.gov (United States)

    Sierra, Carlos A.; Malghani, Saadatullah; Loescher, Henry W.

    2017-02-01

    Determining environmental controls on soil organic matter decomposition is of importance for developing models that predict the effects of environmental change on global soil carbon stocks. There is uncertainty about the environmental controls on decomposition rates at temperature and moisture extremes, particularly at high water content levels and high temperatures. It is uncertain whether observed declines in decomposition rates at high temperatures are due to declines in the heat capacity of extracellular enzymes as predicted by thermodynamic theory, or due to simultaneous declines in soil moisture. It is also uncertain whether oxygen limits decomposition rates at high water contents. Here we present the results of a full factorial experiment using organic soils from a boreal forest incubated at high temperatures (25 and 35 °C), a wide range of water-filled pore space (WFPS; 15, 30, 60, 90 %), and contrasting oxygen concentrations (1 and 20 %). We found support for the hypothesis that decomposition rates are high at high temperatures, provided that enough moisture and oxygen are available for decomposition. Furthermore, we found that decomposition rates are mostly limited by oxygen concentrations at high moisture levels; even at 90 % WFPS, decomposition proceeded at high rates in the presence of oxygen. Our results suggest an important degree of interaction among temperature, moisture, and oxygen in determining decomposition rates at the soil core scale.

  13. Decomposition of soil organic matter from boreal black spruce forest: Environmental and chemical controls

    Science.gov (United States)

    Wickland, K.P.; Neff, J.C.

    2008-01-01

    Black spruce forests are a dominant covertype in the boreal forest region, and they inhabit landscapes that span a wide range of hydrologic and thermal conditions. These forests often have large stores of soil organic carbon. Recent increases in temperature at northern latitudes may be stimulating decomposition rates of this soil carbon. It is unclear, however, how changes in environmental conditions influence decomposition in these systems, and if substrate controls of decomposition vary with hydrologic and thermal regime. We addressed these issues by investigating the effects of temperature, moisture, and organic matter chemical characteristics on decomposition of fibric soil horizons from three black spruce forest sites. The sites varied in drainage and permafrost, and included a "Well Drained" site where permafrost was absent, and "Moderately well Drained" and "Poorly Drained" sites where permafrost was present at about 0.5 m depth. Samples collected from each site were incubated at five different moisture contents (2, 25, 50, 75, and 100% saturation) and two different temperatures (10??C and 20??C) in a full factorial design for two months. Organic matter chemistry was analyzed using pyrolysis gas chromatography-mass spectrometry prior to incubation, and after incubation on soils held at 20??C, 50% saturation. Mean cumulative mineralization, normalized to initial carbon content, ranged from 0.2% to 4.7%, and was dependent on temperature, moisture, and site. The effect of temperature on mineralization was significantly influenced by moisture content, as mineralization was greatest at 20??C and 50-75% saturation. While the relative effects of temperature and moisture were similar for all soils, mineralization rates were significantly greater for samples from the "Well Drained" site compared to the other sites. Variations in the relative abundances of polysaccharide-derivatives and compounds of undetermined source (such as toluene, phenol, 4-methyl phenol, and

  14. Concentrations and flux measurements of volatile organic compounds (VOC) in boreal forest soil

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    Mäki, Mari; Aaltonen, Hermanni; Heinonsalo, Jussi; Hellén, Heidi; Pumpanen, Jukka; Bäck, Jaana

    2017-04-01

    Volatile organic compounds (VOC) impact soil processes as VOCs transmit signals between roots and rhizosphere (Ditengou et al., 2015), VOCs can regulate microbial activity (Asensio et al., 2012), and VOCs can also promote root growth (Hung et al., 2012). Belowground concentrations of VOCs have not been measured in situ and for this reason, knowledge of how different soil organisms such as roots, rhizosphere and decomposers contribute to VOC production is limited. The aim of this study was to determine and quantify VOC fluxes and concentrations of different horizons from boreal forest soil. The VOC concentrations and fluxes were measured from Scots pine (Pinus sylvestris) forest soil at the SMEAR II station in southern Finland from 21th of April to 2nd of December in 2016. VOC fluxes were measured using dynamic (flow-through) chambers from five soil collars placed on five different locations. VOC concentrations were also measured in each location from four different soil horizons with the measurement depth 1-107 cm. VOCs were collected from underground gas collectors into the Tenax-Carbopack-B adsorbent tubes using portable pumps ( 100 ml min-1). The VOC concentrations and fluxes of isoprene, 11 monoterpenes, 13 sesquiterpenes and different oxygenated VOCs were measured. Sample tubes were analyzed using thermal desorption-gas chromatograph-mass spectrometry (TD-GC-MS). Soil temperature and soil water content were continuously monitored for each soil horizon. Our preliminary results show that the primary source of VOCs is organic soil layer and the contribution of mineral soil to the VOC formation is minor. VOC fluxes and concentrations were dominated by monoterpenes such as α-pinene, camphene, β-pinene, and Δ3-carene. Monoterpene concentration is almost 10-fold in organic soil compared to the deeper soil layers. However, the highest VOC fluxes on the soil surface were measured in October, whereas the monoterpene concentrations in organic soil were highest in July

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

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    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.

  16. Control of Boreal Forest Soil Microbial Communities and Processes by Plant Secondary Compounds

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    Leewis, M. C.; Leigh, M. B.

    2016-12-01

    Plants release an array of secondary plant metabolites (SPMEs), which vary widely between plant species/progenies and may drive shifts in soil microbial community structure and function. We hypothesize that SPMEs released through litterfall and root turnover in the boreal forest control ecosystem carbon cycling by inhibiting microbial decomposition processes, which are overcome partially by increased aromatic biodegradation of microbial communities that also fortuitously prime soils for accelerated biodegradation of contaminants. Soils and litter (stems, roots, senescing leaves) were collected from 3 different birch progenies from Iceland, Finland, and Siberia that have been reported to contain different SPME content (low, medium, high, respectively) due to differences in herbivory pressure over their natural history, as well as black spruce, all growing in a long-term common tree garden at the Kevo Subarctic Field Research Institute, Finland. We characterized the SPME content of these plant progenies and used a variety of traditional microbiological techniques (e.g., enzyme assays, litter decomposition and contaminant biodegradation rates) and molecular techniques (e.g., high-throughput amplicon sequencing for bacteria and fungi) to assess how different levels of SPMEs may correlate to shifts in microbial community structure and function. Microbial communities (bacterial and fungal) significantly varied in composition as well as leaf litter and diesel biodegradation rates, in accordance with the phytochemistry of the trees present. This study offers novel, fundamental information about phytochemical controls on ecosystem processes, resilience to contaminants, and microbial decomposition processes.

  17. Trophic position of soil nematodes in boreal forests as indicated by stable isotope analysis

    Science.gov (United States)

    Kudrin, Alexey; Tsurikov, Sergey

    2016-04-01

    Despite the well-developed trophic classification of soil nematodes, their position in soil food webs is still little understood. Observed deviations from the typical feeding strategy indicate that a simplified trophic classification probably does not fully reflect actual trophic interactions. Furthermore, the extent and functional significance of nematodes as prey for other soil animals remains unknown. Stable isotope analysis (SIA) is powerful tool for investigating the structure of soil food webs, but its application to the study of soil nematodes has been limited to only a few studies. We used stable isotope analysis to gain a better understanding of trophic links of several groups of soil nematodes in two boreal forests on albeluvisol. We investigated four taxonomic groups of nematodes: Mononchida, Dorylaimida, Plectidae and Tylenchidae (mostly from the genus Filenchus), that according to the conventional trophic classification represent predators, omnivores, bacterivores and root-fungal feeders, respectively. To assess the trophic position of nematodes, we used a comparison against a set of reference species including herbivorous, saprophagous and predatory macro-invertebrates, oribatid and mesostigmatid mites, and collembolans. Our results suggest that trophic position of the investigated groups of soil nematodes generally corresponds to the conventional classification. All nematodes were enriched in 13C relative to Picea abies roots and litter, and mycorrhizal fungal mycelium. Root-fungal feeders Tylenchidae had δ15N values similar to those of earthworms, enchytraeids and Entomobrya collembolans, but slightly lower δ13C values. Bacterivorous Plectidae were either equal or enriched in 15N compared with saprophagous macroinvertebrates and most mesofauna species. Omnivorous Dorylaimida and predatory Mononchida were further enriched in 15N and their isotopic signature was similar to that of predatory arthropods. These data confirm a clear separation of

  18. Ectomycorrhizal-dominated boreal and tropical forests have distinct fungal communities, but analogous spatial patterns across soil horizons.

    Science.gov (United States)

    McGuire, Krista L; Allison, Steven D; Fierer, Noah; Treseder, Kathleen K

    2013-01-01

    Fungi regulate key nutrient cycling processes in many forest ecosystems, but their diversity and distribution within and across ecosystems are poorly understood. Here, we examine the spatial distribution of fungi across a boreal and tropical ecosystem, focusing on ectomycorrhizal fungi. We analyzed fungal community composition across litter (organic horizons) and underlying soil horizons (0-20 cm) using 454 pyrosequencing and clone library sequencing. In both forests, we found significant clustering of fungal communities by site and soil horizons with analogous patterns detected by both sequencing technologies. Free-living saprotrophic fungi dominated the recently-shed leaf litter and ectomycorrhizal fungi dominated the underlying soil horizons. This vertical pattern of fungal segregation has also been found in temperate and European boreal forests, suggesting that these results apply broadly to ectomycorrhizal-dominated systems, including tropical rain forests. Since ectomycorrhizal and free-living saprotrophic fungi have different influences on soil carbon and nitrogen dynamics, information on the spatial distribution of these functional groups will improve our understanding of forest nutrient cycling.

  19. CARBON MONOXIDE FLUXES OF DIFFERENT SOIL LAYERS IN UPLAND CANADIAN BOREAL FORESTS

    Science.gov (United States)

    Dark or low-light carbon monoxide fluxes at upland Canadian boreal forest sites were measured on-site with static chambers and with a laboratory incubation technique using cores from different depths at the same sites. Three different upland black spruce sites, burned in 1987,199...

  20. Long term implications of fire to soil C content and soil CO2 efflux in northern boreal forests

    Science.gov (United States)

    Koster, Kajar; Berninger, Frank; Pumpanen, Jukka

    2014-05-01

    Fire is the primary process which organizes the physical and biological attributes of the boreal biome and influences energy flows and biogeochemical cycles, particularly the carbon (C) cycle. Especially the soil organic matter pool in boreal forests is an important C storage with a long C turnover time, but fire frequencies that are expected to increase with changing climate, can change that. We compared the initial recovery of C pools and CO2 efflux following fire disturbance in Scots pine (Pinus sylvesteris) stands in the northern boreal forests, of eastern Lapland, Värriö Strict Nature Reserve, Finland (67°46' N, 29°35' E). The sites are situated north of the Arctic Circle, near to the northern timberline at an average of 300 m altitude. We have established 8 sample areas (with two replicate plots in each) in a chronosequence of 4 age classes (2 to 152 years since the last fire). The chronosequence consisted of four types of areas: (i) fire 2 years ago old areas, (ii) fire 42 years ago, (iii) fire around 60 years ago, (iv) fire 152years ago. The total C contents in the first 10 cm of the topsoil were highest on old areas (fire 150 years ago) and lowest on new areas (fire 2-40 years ago). The total C pool at the old site was 2411 g m-2. The area where the fire was 2 years ago had the lowest total C pools, 1474 g m-2 respectively. The lowest C pools were measured from area where the fire was 60 years ago, and from B horizon. The highest C pools were measured on old areas from top soil horizons (consisting of decomposing litter). When we compared the total C pools, the newly burned areas (areas where the fire was 2 - 40 years ago) formed one group (had similar values of total C) and old areas (areas where the fire was 60-150 years ago) formed another group with similar values. These results are also correlating to the soil respiration measurements. Soil CO2 efflux was lowest straight after the fire (0.042 mg CO2 m-2 s-1) and it reached a stable level of around

  1. 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.

  2. 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.

  3. The influence of vegetation and soil characteristics on active-layer thickness of permafrost soils in boreal forest.

    Science.gov (United States)

    Fisher, James P; Estop-Aragonés, Cristian; Thierry, Aaron; Charman, Dan J; Wolfe, Stephen A; Hartley, Iain P; Murton, Julian B; Williams, Mathew; Phoenix, Gareth K

    2016-09-01

    Carbon release from thawing permafrost soils could significantly exacerbate global warming as the active-layer deepens, exposing more carbon to decay. Plant community and soil properties provide a major control on this by influencing the maximum depth of thaw each summer (active-layer thickness; ALT), but a quantitative understanding of the relative importance of plant and soil characteristics, and their interactions in determine ALTs, is currently lacking. To address this, we undertook an extensive survey of multiple vegetation and edaphic characteristics and ALTs across multiple plots in four field sites within boreal forest in the discontinuous permafrost zone (NWT, Canada). Our sites included mature black spruce, burned black spruce and paper birch, allowing us to determine vegetation and edaphic drivers that emerge as the most important and broadly applicable across these key vegetation and disturbance gradients, as well as providing insight into site-specific differences. Across sites, the most important vegetation characteristics limiting thaw (shallower ALTs) were tree leaf area index (LAI), moss layer thickness and understory LAI in that order. Thicker soil organic layers also reduced ALTs, though were less influential than moss thickness. Surface moisture (0-6 cm) promoted increased ALTs, whereas deeper soil moisture (11-16 cm) acted to modify the impact of the vegetation, in particular increasing the importance of understory or tree canopy shading in reducing thaw. These direct and indirect effects of moisture indicate that future changes in precipitation and evapotranspiration may have large influences on ALTs. Our work also suggests that forest fires cause greater ALTs by simultaneously decreasing multiple ecosystem characteristics which otherwise protect permafrost. Given that vegetation and edaphic characteristics have such clear and large influences on ALTs, our data provide a key benchmark against which to evaluate process models used to predict

  4. Carbon fractions and stocks in organic layers in boreal forest soils. Impacts of climatic and nutritional conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hilli, S.

    2011-07-01

    The SOM in boreal forests contains non-living heterogeneous components resulting from microbial and chemical transformations of organic debris from plant litter. The major components in the plant biomass all decompose at different rates and therefore, contribute variably to the stable storages of soil C. The aims of the current thesis were (1) to explore how climate, soil fertility and initial litter quality affect the decomposition rate of litter, (2) to study how the different carbon fractions found in the plant litter relate to the quality and quantity of SOM in forest soils, (3) to determine whether the recalcitrant fraction of litter is derived from lignin and other polyphenols or from lipophilic compounds and carbohydrates, and (4) to determine whether the litter originating from different plant growth forms affects SOM formation in a similar way. The study was conducted in six north boreal and six south boreal study sites, half of which were mesic and half were sub-xeric. The overall initial litter quality and decomposition rate of carbon fractions did not differ between the two fertility levels and climate regimes. Litter with high initial water-soluble extractives (WSE) and nitrogen (N) decomposed at a faster rate than litter with lower initial WSE and N concentration irrespective of the soil fertility or climate conditions. Although decomposition rate varies among litter types, decomposition rate cannot explain differences in SOM quality or quantity between the northern and southern boreal forests. The organic matter accumulation and relative proportion of acid-insoluble residue (AIR) in SOM was higher in south boreal sites both in sub-xeric and mesic sites. Detailed characterization of the AIR fraction using pyrolysis-GC demonstrated that in the litter layer the concentration of AIR contains lignin and other insoluble polyphenols, but in the F and H layers, lignin-derived and chemically modified polyphenolics and decomposition products of resin acids

  5. 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

  6. 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.

  7. How mycorrhizal plant-soil interactions affect formation and degradation of soil organic matter in boreal forest

    Science.gov (United States)

    Adamczyk, Bartosz; Sietiö, Outi-Maaria; Ahvenainen, Anu; Strakova, Petra; Heinonsalo, Jussi

    2017-04-01

    Forest soil organic matter (SOM) contains more carbon (C) than all the flora and atmosphere combined and that is why C release as CO2 from SOM may have drastic consequences for climate globally. SOM is enormous C sink which has the potential to become C source (IPCC 2013). To predict long-term soil C storage and climate feedbacks we need profound understanding of dynamics and drivers of SOM decomposition. Ecosystem processes associated with C cycle are constrained by C and N interactions. At the level of ecosystem boreal forest is N-limited, as most of soil N is stored in recalcitrant organic form bound or complexed with soil compounds such as polyphenols. To improve N uptake, also from less available pools, plant species form symbioses with mycorrhizal fungi able to degrade recalcitrant N and sharing it with plants. As a feedback, plants provide to fungal symbiont assimilated C. Climate change through elevated CO2 level led to increases in photosynthesis which enhance the C flow belowground accelerating N uptake by plants also from more recalcitrant N pools. Increased SOM decomposition would possibly result also in increase of CO2 production from soil. Our field experiment was conducted at Hyytiälä forestry field station (SMEAR II, University of Helsinki) located in southern Finland (61°84'N, 24°26'E). In this 3-year long experiment, we discriminated SOM decomposition with different mesh bags filled with humus. These mesh bags allowed for the entrance of mycorrhiza and fine roots (1mm mesh size), or only mycorrhiza (50µm), or both were excluded (1µm). We followed changes in SOM content, N pools and enzymatic activity. The results suggests that plant-mycorrhiza interactions increase recalcitrant pool of organic N in SOM due to root-derived tannins, but mycorrhizal plants have still access to this N. Although mycorrhizal plant-soil interaction seems to strongly affect the formation of recalcitrant SOM, the net decomposition is not hindered by these chemical

  8. Plant Community and Nitrogen Deposition as Drivers of Alpha and Beta Diversities of Prokaryotes in Reconstructed Oil Sand Soils and Natural Boreal Forest Soils.

    Science.gov (United States)

    Masse, Jacynthe; Prescott, Cindy E; Renaut, Sébastien; Terrat, Yves; Grayston, Sue J

    2017-05-01

    The Athabasca oil sand deposit is one of the largest single oil deposits in the world. Following surface mining, companies are required to restore soil-like profiles that can support the previous land capabilities. The objective of this study was to assess whether the soil prokaryotic alpha diversity (α-diversity) and β-diversity in oil sand soils reconstructed 20 to 30 years previously and planted to one of three vegetation types (coniferous or deciduous trees and grassland) were similar to those found in natural boreal forest soils subject to wildfire disturbance. Prokaryotic α-diversity and β-diversity were assessed using massively parallel sequencing of 16S rRNA genes. The β-diversity, but not the α-diversity, differed between reconstructed and natural soils. Bacteria associated with an oligotrophic lifestyle were more abundant in natural forest soils, whereas bacteria associated with a copiotrophic lifestyle were more abundant in reconstructed soils. Ammonia-oxidizing archaea were most abundant in reconstructed soils planted with grasses. Plant species were the main factor influencing α-diversity in natural and in reconstructed soils. Nitrogen deposition, pH, and plant species were the main factors influencing the β-diversity of the prokaryotic communities in natural and reconstructed soils. The results highlight the importance of nitrogen deposition and aboveground-belowground relationships in shaping soil microbial communities in natural and reconstructed soils.IMPORTANCE Covering over 800 km(2), land disturbed by the exploitation of the oil sands in Canada has to be restored. Here, we take advantage of the proximity between these reconstructed ecosystems and the boreal forest surrounding the oil sand mining area to study soil microbial community structure and processes in both natural and nonnatural environments. By identifying key characteristics shaping the structure of soil microbial communities, this study improved our understanding of how

  9. Development of soft extraction method for structural characterization of boreal forest soil proteins with MALDI-TOF/MS

    Science.gov (United States)

    Kanerva, Sanna; Ketola, Raimo A.; Kitunen, Veikko; Smolander, Aino; Kotiaho, Tapio

    2010-05-01

    Nitrogen (N) is usually the nutrient restricting productivity in boreal forests. Forest soils contain a great amount of nitrogen, but only a small part of it is in mineral form. Most part of soil N is bound in the structures of different organic compounds such as proteins, peptides, amino acids and more stabilized, refractory compounds. Due to the fact that soil organic N has a very important role in soil nutrient cycling and in plant nutrition, there is a need for more detailed knowledge of its chemistry in soil. Conventional methods to extract and analyze soil organic N are usually very destructive for structures of higher molecular weight organic compounds, such as proteins. The aim of this study was to characterize proteins extracted from boreal forest soil by "soft" extraction methods in order to maintain their molecular structure. The organic layer (F) from birch forest floor containing 78% of organic matter was sieved, freeze dried, pulverized, and extracted with a citrate or phosphate buffer (pH 6 or 8). Sequential extraction with the citrate or phosphate buffer and an SDS buffer (pH 6.8), slightly modified from the method of Chen et al. (2009, Proteomics 9: 4970-4973), was also done. Proteins were purified from the soil extract by extraction with buffered phenol and precipitated with methanol + 0.1M ammonium acetate at -20°C. Characterization of proteins was performed with matrix assisted laser desorption ionization - time-of-flight mass spectrometry (MALDI-TOF/MS) and the concentration of total proteins was measured using Bradford's method. Bovine serum albumin (BSA) was used as a positive control in the extractions and as a standard protein in Bradford's method. Our results showed that sequential extraction increased the amount of extracted proteins compared to the extractions without the SDS-buffer; however, it must be noted that the use of SDS-buffer very probably increased denaturization of proteins. Purification of proteins from crude soil extracts

  10. Disturbances (fire and grazing by reindeer) and soil methane fluxes -- case studies from the subarctic boreal forest of Finish Lapland.

    Science.gov (United States)

    Köster, Kajar; Köster, Egle; Berninger, Frank; Pumpanen, Jukka

    2016-04-01

    In aerobic, well-drained environments such as boreal upland forest soils, methane (CH4) is oxidized by microbes, resulting into the soils acting as a sink of atmospheric CH4. The emission of CH4 is controlled primarily by soil moisture and temperature, but also by the availability of organic carbon. Forest fires are one of the predominant natural disturbances in subarctic boreal forests that strongly influence soil moisture and soil temperature values and carbon dynamics of the soils. At the same time also the effect of reindeer (Rangifer tarandus L.) grazing on soil moisture and temperature regimes in the lichen-dominated Arctic ecosystems has been found to be considerable. By removing the lichen carpet and damaging the secondary vegetation mat, reindeer make patches of bare soil common, and these factors in combination with trampling allow for soil to warm up faster, reach higher temperatures, and reduce the soil moisture content. We studied the effect of reindeer grazing and forest fire on fluxes of CH4 in northern boreal subarctic Scots pine forest stands. The study areas are in eastern Lapland, Värriö Strict Nature Reserve, Finland (67° 46' N, 29° 35' E). The sites are situated north of the Arctic Circle, near to the northern timberline at an average of 300 m altitude. For studing the effect of fire we have established sample areas (with three replicate plots in each) in a chronosequence of 4 age classes (2 to 152 years since the last fire). The fire chronosequence consisted of four types of areas with different time since the last forest fire: i) 5 years, ii) 45 years, iii) 70 years and iv) 155 years after fire. For studing the effect of reindeer grazing (comparison of grazed and non-grazed areas) we have established the study areas (10 sample plots in total established in year 2013) along the borderline between Finland and Russia. The ungrazed area was excluded from the reindeer grazing already in 1918, to prevent the Finnish reindeer from going to the

  11. 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

  12. Underestimation of soil carbon stocks by Yasso07, Q, and CENTURY models in boreal forest linked to overlooking site fertility

    Science.gov (United States)

    Ťupek, Boris; Ortiz, Carina; Hashimoto, Shoji; Stendahl, Johan; Dahlgren, Jonas; Karltun, Erik; Lehtonen, Aleksi

    2016-04-01

    The soil organic carbon stock (SOC) changes estimated by the most process based soil carbon models (e.g. Yasso07, Q and CENTURY), needed for reporting of changes in soil carbon amounts for the United Nations Framework Convention on Climate Change (UNFCCC) and for mitigation of anthropogenic CO2 emissions by soil carbon management, can be biased if in a large mosaic of environments the models are missing a key factor driving SOC sequestration. To our knowledge soil nutrient status as a missing driver of these models was not tested in previous studies. Although, it's known that models fail to reconstruct the spatial variation and that soil nutrient status drives the ecosystem carbon use efficiency and soil carbon sequestration. We evaluated SOC stock estimates of Yasso07, Q and CENTURY process based models against the field data from Swedish Forest Soil National Inventories (3230 samples) organized by recursive partitioning method (RPART) into distinct soil groups with underlying SOC stock development linked to physicochemical conditions. These models worked for most soils with approximately average SOC stocks, but could not reproduce higher measured SOC stocks in our application. The Yasso07 and Q models that used only climate and litterfall input data and ignored soil properties generally agreed with two third of measurements. However, in comparison with measurements grouped according to the gradient of soil nutrient status we found that the models underestimated for the Swedish boreal forest soils with higher site fertility. Accounting for soil texture (clay, silt, and sand content) and structure (bulk density) in CENTURY model showed no improvement on carbon stock estimates, as CENTURY deviated in similar manner. We highlighted the mechanisms why models deviate from the measurements and the ways of considering soil nutrient status in further model development. Our analysis suggested that the models indeed lack other predominat drivers of SOC stabilization

  13. Carbon and nitrogen pools and mineralization rates in boreal forest soil after stump harvesting

    Science.gov (United States)

    Kaarakka, Lilli; Hyvönen, Riitta; Strömgren, Monika; Palviainen, Marjo; Persson, Tryggve; Olsson, Bengt A.; Helmisaari, Heljä-Sisko

    2016-04-01

    The use of forest-derived biomass has steadily increased in the Finland and Sweden during the past decades. Thus, more intensive forest management practices are becoming more common in the region, such as whole-tree harvesting, both above- and belowground. Stump harvesting causes a direct removal of carbon (C) in the form of biomass from the stand and can cause extensive soil disturbance, which in turn can result in increased C mineralization. In this study, the effects of stump harvesting on soil C and nitrogen (N) mineralization, and soil surface disturbance were studied at two different clear-felled Norway spruce (Picea abies) stands in Central Finland. The treatments were conventional stem-only harvesting combined with mounding (WTH) and stump harvesting (i.e. complete tree harvesting) combined with mounding (WTH+S). Logging residues were removed from all study sites. Soil samples down to a depth of 20 cm were systematically collected from the different soil disturbance surfaces (undisturbed soil, the mounds and the pits) 12-13 years after final harvest. Soil samples were incubated in the laboratory to determine the C and N mineralization rates. In addition, total C and N pools were estimated for each disturbance class and soil layer. Soil C and N pools were lower following stump harvesting, however, no statistically significant treatment effect was detected. Instead, C mineralization responses to treatment intensity was site-specific. C/N-ratio and organic matter content were significantly affected by harvest intensity. The observed changes in C and N pools appear to be related to the intrinsic variation of the surface disturbance and soil characteristics, and harvesting per se, rather than treatment intensity. Long-term studies are however needed to draw long-term conclusions whether stump harvesting significantly changes soil C and nutrient dynamics.

  14. Influence of soil frost on the character and degradability of dissolved organic carbon in boreal forest soils

    Science.gov (United States)

    Panneer Selvam, B.; Laudon, H.; Guillemette, F.; Berggren, M.

    2016-03-01

    Recent studies suggest that increases in extent and duration of winter soil frost increases dissolved organic carbon (DOC) concentrations in boreal riparian soils and connected aquatic systems during the subsequent spring and summer. However, little is known about the impact of frost on DOC character and its degradability. We applied three experimental treatments to riparian soils in northern Sweden—shallow soil frost (insulated), deep soil frost (snow removed) and control plots—to test the effect of different soil frost regimes on the chemical characteristics and degradability of soil DOC. Soil pore water samples were analyzed using excitation-emission fluorescence (parallel factor analysis) combined with biological and photochemical degradation experiments. We found that the absolute bacterial metabolic rates were significantly lower in samples from the shallow soil frost treatments, compared with the other treatments. Explorative multivariate analyses indicate that increasing soil frost is contributing to increased protein-like fluorescence and to increased biological degradability of the DOC. Our study shows that decreases in riparian soil frost due to climate warming may not only contribute to decreased riparian DOC concentrations but also lead to shifts in the DOC composition, resulting in decreased biodegradability (yet similar photodegradability) of the DOC that is exported from riparian soils to streams.

  15. Occurrence and Distribution of Synthetic Organic Substances in Boreal Coniferous Forest Soils Fertilized with Hygienized Municipal Sewage Sludge.

    Science.gov (United States)

    Lindberg, Richard; Sahlén, Kenneth; Tysklind, Mats

    2013-07-17

    The occurrence and distribution of synthetic organic substances following application of dried and granulated (hygienized) municipal sewage sludge in Swedish boreal coniferous forests were investigated. Elevated concentrations of triclosan (TCS), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) were detected in the humus layer. Concentrations of ethinyl estradiol (EE2), norfloxacin, ciprofloxacin, ofloxacin (FQs), and polyaromatic hydrocarbons (PAHs) were not significantly influenced. Maximum concentrations in humus were as follows (in ng/g dry matter): TCS; 778; PBDEs; 25; and PCB7; 16.7. Fertilization did not alter the levels of the substances in mineral soil, ground water, and various types of samples related to air. Further research within this area is needed, including ecotoxicological effects and fate, in order to improve the knowledge regarding the use of sludge as a fertilizing agent. Continuous annual monitoring, with respect to sampling and analysis, should be conducted on the already-fertilized fields.

  16. Occurrence and Distribution of Synthetic Organic Substances in Boreal Coniferous Forest Soils Fertilized with Hygienized Municipal Sewage Sludge

    Directory of Open Access Journals (Sweden)

    Mats Tysklind

    2013-07-01

    Full Text Available The occurrence and distribution of synthetic organic substances following application of dried and granulated (hygienized municipal sewage sludge in Swedish boreal coniferous forests were investigated. Elevated concentrations of triclosan (TCS, polybrominated diphenyl ethers (PBDEs, and polychlorinated biphenyls (PCBs were detected in the humus layer. Concentrations of ethinyl estradiol (EE2, norfloxacin, ciprofloxacin, ofloxacin (FQs, and polyaromatic hydrocarbons (PAHs were not significantly influenced. Maximum concentrations in humus were as follows (in ng/g dry matter: TCS; 778; PBDEs; 25; and PCB7; 16.7. Fertilization did not alter the levels of the substances in mineral soil, ground water, and various types of samples related to air. Further research within this area is needed, including ecotoxicological effects and fate, in order to improve the knowledge regarding the use of sludge as a fertilizing agent. Continuous annual monitoring, with respect to sampling and analysis, should be conducted on the already-fertilized fields.

  17. 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

  18. 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.

  19. N cycling and the composition of terpenes and tannins in boreal forest soils: Effects of logging residues

    Science.gov (United States)

    Smolander, Aino; Kitunen, Veikko; Kukkola, Mikko; Tamminen, Pekka

    2014-05-01

    There is increasing evidence available that certain terpenes and tannins may mediate substantial changes in nitrogen cycling processes in boreal forest soils. Terpenes and tannins are two important groups of plant secondary metabolites: Terpenes are hydrocarbons having different number of isoprene-derived units and tannins are complex polyphenolic compounds able to interact with proteins. Logging residues, consisting of fresh tree tops and branches with needles contain large amounts of terpenes and tannins. Currently there is increasing demand for forest biomass for bioenergy production. Therefore, harvesting of logging residues has become more common from both clear-cutting and thinning stands, instead of conventional stem-only harvest where logging residues are retained on the site. Our aim was to determine how logging residues affect soil N cycling processes in Scots pine and Norway spruce thinning stands in long-term, and how these processes are related to the composition of terpenes and tannins in the soil. Samples were taken from the humus layer of pine and spruce experiments which had been thinned 4-to-19 years before; in the thinning different amounts of logging residues had been distributed on the plots. Logging residues had only little effect on soil microbial biomass N or C. However, in several sites logging residues increased the rate of net N mineralization and the ratios net N mineralization/ C mineralization and net N mineralization/microbial biomass N, and these positive effects were very long-lasting. Logging residues also changed the composition of different terpenes and condensed tannins in soil. In general, with regard to the processes and ratios indicating N availability, stem-only harvest seems to be more favorable than whole-tree harvest. The results from long-term field experiments will be discussed in relation to the effects of different terpenes and tannins, observed in short-term laboratory experiments, on N cycling processes.

  20. Soil Moisture Limitations on Monitoring Boreal Forest Regrowth Using Spaceborne L-Band SAR Data

    Science.gov (United States)

    Kasischke, Eric S.; Tanase, Mihai A.; Bourgeau-Chavez, Laura L.; Borr, Matthew

    2011-01-01

    A study was carried out to investigate the utility of L-band SAR data for estimating aboveground biomass in sites with low levels of vegetation regrowth. Data to estimate biomass were collected from 59 sites located in fire-disturbed black spruce forests in interior Alaska. PALSAR L-band data (HH and HV polarizations) collected on two dates in the summer/fall of 2007 and one date in the summer of 2009 were used. Significant linear correlations were found between the log of aboveground biomass (range of 0.02 to 22.2 t ha-1) and (L-HH) and (L-HV) for the data collected on each of the three dates, with the highest correlation found using the LHV data collected when soil moisture was highest. Soil moisture, however, did change the correlations between L-band and aboveground biomass, and the analyses suggest that the influence of soil moisture is biomass dependent. The results indicate that to use L-band SAR data for mapping aboveground biomass and monitoring forest regrowth will require development of approaches to account for the influence that variations in soil moisture have on L-band microwave backscatter, which can be particularly strong when low levels of aboveground biomass occur

  1. Soil Moisture Limitations on Monitoring Boreal Forest Regrowth Using Spaceborne L-Band SAR Data

    Science.gov (United States)

    Kasischke, Eric S.; Tanase, Mihai A.; Bourgeau-Chavez, Laura L.; Borr, Matthew

    2011-01-01

    A study was carried out to investigate the utility of L-band SAR data for estimating aboveground biomass in sites with low levels of vegetation regrowth. Data to estimate biomass were collected from 59 sites located in fire-disturbed black spruce forests in interior Alaska. PALSAR L-band data (HH and HV polarizations) collected on two dates in the summer/fall of 2007 and one date in the summer of 2009 were used. Significant linear correlations were found between the log of aboveground biomass (range of 0.02 to 22.2 t ha-1) and (L-HH) and (L-HV) for the data collected on each of the three dates, with the highest correlation found using the LHV data collected when soil moisture was highest. Soil moisture, however, did change the correlations between L-band and aboveground biomass, and the analyses suggest that the influence of soil moisture is biomass dependent. The results indicate that to use L-band SAR data for mapping aboveground biomass and monitoring forest regrowth will require development of approaches to account for the influence that variations in soil moisture have on L-band microwave backscatter, which can be particularly strong when low levels of aboveground biomass occur

  2. 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.

  3. 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.

  4. 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

  5. Interannual variations in soil moisture and productivity of boreal forest in Eastern Siberia

    Science.gov (United States)

    Sugimoto, A.; Tei, S.; Ohte, N.; Osaka, K.; Naito, D.; Maximov, T. C.

    2008-12-01

    Interannual variations in soil moisture and vegetation parameters were observed for 9 years in a larch forest near Yakutsk, Russia in Eastern Siberia, to investigate the response of the ecosystem. Soil moisture varied depending on both the amount of summer rainfall in the year and soil moisture at the end of the previous summer carried over as ice. The annual water budget of soil moisture (dQs) from the previous August to the current year primarily corresponds to precipitation, with a deviations caused by runoff (decrease in dQs), limited transpiration and/or upward transport of ice meltwater from the bottom of the active layer (increase in dQs). The source of water for transpiration was inferred from sap water delta18O. Snow meltwater with low delta18O preset in spring was used in early summer (June) every year, while, summer precipitation with high delta18O was transpired in a wet summer and ice meltwater with low delta18O was a major contributor to transpiration during droughts. Tree growth (GBH increment) correlated with soil moisture in August of the same year, and there was no correlation observed with the date of snow thaw. Larch needle delta13C showed negative correlation with soil moisture in the previous August, indicating lowering of stomatal conductance during a drought and carrying over of carbon until the following year. Litter fall production seems to increase with a two-year time lag behind the increase in soil moisture due to carrying over of soil moisture and response of vegetation. Larch needle delta15N (-1.3?n on average) negatively correlated with C/N ratio, possibly caused by water and nutrient availability.

  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. Distribution of {sup 210}Pb and {sup 210}Po in boreal forest soil

    Energy Technology Data Exchange (ETDEWEB)

    Vaaramaa, Kaisa, E-mail: kaisa.vaaramaa@stuk.fi [Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Aro, Lasse [Finnish Forest Research Institute (METLA), Parkano Research Unit, Kaironiementie 54, 39700 Parkano (Finland); Solatie, Dina [STUK-Radiation and Nuclear Safety Authority, Regional Laboratory in Northern Finland, Laehteentie 2, 96400 Rovaniemi (Finland); Lehto, Jukka [Laboratory of Radiochemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland)

    2010-11-15

    Vertical distribution and activity contents of {sup 210}Pb and {sup 210}Po were investigated in forest soils of Scots pine-dominated (Pinus sylvestris L.) stands from seven different locations in Finland. The mean total inventory in the soil profile, up to 20 cm, of {sup 210}Pb was 4.0 kBq m{sup -2} (range 3.1-5.0 kBq m{sup -2}) and {sup 210}Po 5.5 kBq m{sup -2} (range 4.0-7.4 kBq m{sup -2}), the organic soil layer containing 45% of the total inventory of both nuclides. In both the organic and the mineral layers the {sup 210}Po/{sup 210}Pb ratio was close to unity indicating a radioactive equilibrium between them. In the litter layer there was, however, a clear excess of {sup 210}Po suggesting that polonium is recycled via root uptake from the root zone to the ground surface. The activity concentration (Bq kg{sup -1}) of {sup 210}Pb clearly correlated with organic matter and the Fe, Al and Mn concentrations in soil indicating that radioactive lead is associated both with humic substances and the oxides of iron, aluminium and manganese. Radioactive lead was also seen to follow the behavior of stable lead. No systematic correlation between polonium and soil properties was seen.

  8. Impacts of forestry on boreal forests: An ecosystem services perspective.

    Science.gov (United States)

    Pohjanmies, Tähti; Triviño, María; Le Tortorec, Eric; Mazziotta, Adriano; Snäll, Tord; Mönkkönen, Mikko

    2017-04-22

    Forests are widely recognized as major providers of ecosystem services, including timber, other forest products, recreation, regulation of water, soil and air quality, and climate change mitigation. Extensive tracts of boreal forests are actively managed for timber production, but actions aimed at increasing timber yields also affect other forest functions and services. Here, we present an overview of the environmental impacts of forest management from the perspective of ecosystem services. We show how prevailing forestry practices may have substantial but diverse effects on the various ecosystem services provided by boreal forests. Several aspects of these processes remain poorly known and warrant a greater role in future studies, including the role of community structure. Conflicts among different interests related to boreal forests are most likely to occur, but the concept of ecosystem services may provide a useful framework for identifying and resolving these conflicts.

  9. Autotrophic and heterotrophic soil respiration determined with trenching, soil CO2 fluxes and 13CO2/12CO2 concentration gradients in a boreal forest ecosystem

    Science.gov (United States)

    Pumpanen, Jukka; Shurpali, Narasinha; Kulmala, Liisa; Kolari, Pasi; Heinonsalo, Jussi

    2017-04-01

    in CO2 in different soil layers in a boreal forest in Southern Finland and compared them to seasonal variation in GPP. Our results show that Ra followed a seasonal variation in GPP with a time lag of about 2 weeks. The contribution of Ra on soil CO2 efflux was largest in July and August. There was also a distinct seasonal pattern in the vertical distribution of soil CO2 concentration and the abundances of natural isotopes 13C/12C in soil CO2 which reflected the changes in biological activity in the soil profile. Our results indicate that all methods were able to distinguish seasonal variability in Ra and Rh. The soil CO2 gradient method was able to reproduce the temporal variation in soil CO2 effluxes relatively well when compared to those measured with chambers. However, variation in soil moisture also causes significant variation in soil air CO2 concentrations which interferes with the variation resulted from soil temperatures and belowground allocation of carbon from recent photosynthate. Also, the assumptions used in gradient method calculations, such as soil porosity and transport distances have to be taken into account when interpreting the results.

  10. Soil biogeochemistry properties vary between two boreal forest ecosystems in Quebec: significant differences in soil carbon, available nutrients and iron and aluminium crystallinity

    Science.gov (United States)

    Bastianelli, Carole; Ali, Adam A.; Beguin, Julien; Bergeron, Yves; Grondin, Pierre; Hély, Christelle; Paré, David

    2017-04-01

    At the northernmost extent of the managed forest in Quebec, the boreal forest is currently undergoing an ecological transition from closed-canopy black spruce-moss forests towards open-canopy lichen woodlands, which spread southward. Our study aim was to determine whether this shift could impact soil properties on top of its repercussions on forest productivity or carbon storage. We studied the soil biogeochemical composition of three pedological layers in moss forests (MF) and lichen woodlands (LW) north of the Manicouagan crater in Quebec. The humus layer (FH horizons) was significantly thicker and held more carbon, nitrogen and exchangeable Ca and Mg in MF plots than in LW plots. When considering mineral horizons, we found that the deep C horizon had a very close composition in both ecosystem plots, suggesting that the parent material was of similar geochemical nature. This was expected as all selected sites developed from glacial deposit. Multivariate analysis of surficial mineral B horizon showed however that LW B horizon displayed higher concentrations of Al and Fe oxides than MF B horizon, particularly for inorganic amorphous forms. Conversely, main exchangeable base cations (Ca, Mg) were higher in B horizon of MF than that of LW. Ecosystem types explained much of the variations in the B horizon geochemical composition. We thus suggest that the differences observed in the geochemical composition of the B horizon have a biological origin rather than a mineralogical origin. We also showed that total net stocks of carbon stored in MF soils were three times higher than in LW soils (FH + B horizons, roots apart). Altogether, we suggest that variations in soil properties between MF and LW are linked to a cascade of events involving the impacts of natural disturbances such as wildfires on forest regeneration that determines the of vegetation structure (stand density) and composition (ground cover type) and their subsequent consequences on soil environmental

  11. Radon 222 tracing of soil and forest canopy trace gas exchange in an open canopy boreal forest

    Science.gov (United States)

    Ussler, William, III; Chanton, Jeffrey P.; Kelley, Cheryl A.; Martens, Christopher S.

    1994-01-01

    A set of continuous, high-resolution atmospheric radon (Rn-222) concentration time series and radon soil flux measurements were acquired during the summer of 1990 at a micrometeorological tower site 13 km northwest of Schefferville, Quebec, Canada. The tower was located in a dry upland, open-canopy lichen-spruce woodland. For the period July 23 to August 1, 1990, the mean radon soil flux was 41.1 +/- 4.8 Bq m(exp -2)/h. Radon surface flux from the two end-member forest floor cover types (lichen mat and bare soil) were 38.8 +/- 5.1 and 61.8 +/- 15.6 Bq m(exp -2)/h, respectively. Average total forest canopy resistances computed using a simple 'flux box' model for radon exchange between the forest canopy and the overlying atmosphere range from 0.47 +/- 0.24 s cm(exp -1) to 2.65 +/- 1.61 cm(exp -1) for daytime hours (0900-1700 LT) and from 3.44 +/- 0.91 s cm(exp -1) to 10.55 +/- 7.16 s cm(exp -1) for nighttime hours (2000-0600) for the period July 23 to August 6, 1990. Continuous radon profiling of canopy atmospheres is a suitable approach for determining rates of biosphere/atmosphere trace gas exchange for remote field sites where daily equipment maintenance is not possible. where daily equipment maintenance is not possible.

  12. Element interactions and soil properties affecting the soil-to-plant transfer of six elements relevant to radioactive waste in boreal forest

    Energy Technology Data Exchange (ETDEWEB)

    Roivainen, Paeivi; Makkonen, Sari; Holopainen, Toini; Juutilainen, Jukka [University of Eastern Finland, Department of Environmental Science, Kuopio (Finland)

    2012-03-15

    Cobalt (Co), lead (Pb), molybdenum (Mo), nickel (Ni), uranium (U), and zinc (Zn) are among the elements that have radioactive isotopes in radioactive waste. Soil-to-plant transfer is a key process for possible adverse effects if these radionuclides are accidentally released into the environment. The present study aimed at investigating factors affecting such transfer in boreal forest. The plant species studied were blueberry (Vaccinium myrtillus), May lily (Maianthemum bifolium), narrow buckler fern (Dryopteris carthusiana), rowan (Sorbus aucuparia) and Norway spruce (Picea abies). Regression analyses were carried out to investigate the effects of the chemical composition and physical properties of soil on the soil-to-leaf/needle concentration ratios of Co, Mo, Ni, Pb, U and Zn. Soil potassium (K), magnesium (Mg), manganese (Mn), phosphorus (P) and sulphur (S) concentrations were the most important factors affecting the soil-to-plant transfer of the elements studied. Soil clay and organic matter contents were found to significantly affect plant uptake of Mo, Pb and U. Knowledge of the effects of these factors is helpful for interpretation of the predictions of radioecological models describing soil-to-plant transfer and for improving such models. (orig.)

  13. 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.

  14. Variability of soil enzyme activities and vegetation succession following boreal forest surface soil transfer to an artificial hill

    Directory of Open Access Journals (Sweden)

    Maarit Niemi

    2014-08-01

    Full Text Available A landfill site in southern Finland was converted into urban green space by covering it with a layer of fresh forest humus transferred from nearby construction sites. The aim was to develop the 70 m high artificial hill into a recreational area with high biodiversity of flora and fauna. Forest humus was used as a source of organic matter, plant roots, seeds, soil fauna and microorganisms in order to enable rapid regeneration of diverse vegetation and soil biological functions. In this study we report the results of three years of monitoring of soil enzyme activity and plant species compositional patterns. Monthly soil samples were taken each year between June and September from four sites on the hill and from two standing reference forests using three replicate plots. Activities of 10 different enzymes, soil organic matter (SOM content, moisture, pH and temperature of the surface layer were monitored. Abundances of vascular plant species were surveyed on the same four hill sites between late May and early September, three times a season in 2004 and 2005. Although the addition of organic soil considerably increased soil enzyme activities (per dw, the activities at the covered hill sites were far lower than in the reference forests. Temporal changes and differences between sites were analysed in more detail per soil organic matter (SOM in order to reveal differences in the quality of SOM. All the sites had a characteristic enzyme activity pattern and two hill sites showed clear temporal changes. The enzyme activities in uncovered topsoil increased, whereas the activities at the covered Middle site decreased, when compared with other sites at the same time. The different trend between Middle and North sites in enzyme activities may reflect differences in humus material transferred to these sites, but difference in the succession of vegetation affects enzyme activities strongly. Middle yielded higher β-sitosterol content in 2004, as an indication

  15. Application of boreal forest toxicity data in the decision-making process for contaminated soil clean-up remediation at oil and gas fields in Western Canada

    Energy Technology Data Exchange (ETDEWEB)

    Scroggins, R.; Princz, J. [Environment Canada, Ottawa, ON (Canada); Moody, M. [Saskatchewan Research Council, Regina, SK (Canada); Olsgard-Dumanski, M.; Haderlein, L. [WorleyParsons Canada, Calgary, AB (Canada); Moore, B. [Devon Canada Corp., Calgary, AB (Canada)

    2010-07-01

    This presentation reported on a multi-year research project in which a broad range of boreal forest test methods for assessing petroleum hydrocarbon (PHC) toxicity in contaminated soil were used to show that clean-up decisions can be made on a field-wide basis through focused biological testing of typical drill sump and flare pit locations within an oil and gas field. Remediation at most sites will likely be limited to the Alberta soil eco-contact guidelines for PHC F2 and F3 fractions. Since Tier 1 eco-contact guidelines are derived using toxicity data from fresh crude and using agricultural plant species, it was more logical to follow a Tier 2 eco-contact pathway approach because most contamination was related to drilling sumps and flare pits containing highly weathered PHCs and species native to the boreal eco-zone of Canada. The site-specific remedial objective (SSRO) option within the Tier 2 guideline was used because of the large number of sites requiring remediation, and the similarity of sites within pre-determined Risk Assessment Zones. For representative contaminated soils, a SSRO was derived from the twenty-fifth percentile of the estimated species sensitivity distribution of all acceptable boreal plant, earthworm, springtail and mite test endpoints. The purpose of the project was to reduce soil volumes sent to landfill during site remediation by showing that residual impacts from weathered PHC in soil do not have damaging effects on boreal forest receptors following remediation. Data was included to show the value of this approach and the variability between sites and their effect on regionalizing a Tier 2 eco-contact guideline.

  16. The effect of wood ash fertilization on soil respiration and tree stand growth in boreal peatland forests

    Science.gov (United States)

    Liimatainen, Maarit; Maljanen, Marja; Hytönen, Jyrki

    2017-04-01

    Out of Finland's original 10 million hectares of peatlands over half has been drained for forestry. Natural peatlands act as a sink for carbon but when peatland is drained, increased oxygen concentration in the peat accelerates the aerobic decomposition of the old organic matter of the peat leading to carbon dioxide (CO2) emissions to atmosphere. Increasing use of bioenergy increases also the amount of ash produced as a byproduct in power plants. Wood ash contains all essential nutrients for trees to grow except nitrogen. Therefore, wood ash is ideal fertilizer for nitrogen rich peatland forests where lack of phosphorus or potassium may restrict tree growth. At the moment, wood ash is the only available PK-fertilizer for peatland forests in Finland and areas of peatland forests fertilized with ash are increasing annually. The effects of wood ash on vegetation, soil properties and tree growth are rather well known although most of the studies have been made using fine ash whereas nowadays mostly stabilized ash (e.g. granulated) is used. Transporting and spreading of stabilized ash is easier than that of dusty fine ash. Also, slower leaching rate of nutrients is environmentally beneficial and prolongs the fertilizer effect. The knowledge on the impact of granulated wood ash on greenhouse gas emissions is still very limited. The aim of this study was to examine the effects of granulated wood ash on CO2 emissions from peat and tree stand growth. Field measurements were done in two boreal peatland forests in 2011 and 2012. One of the sites is more nutrient rich with soil carbon to nitrogen ratio (C/N) of 18 whereas the other site is nutrient poor with C/N ratio of 82. Both sites were fertilized with granulated wood ash in 2003 (5000 kg ha-1). The effect of fertilization was followed with tree stand measurements conducted 0, 5 and 10 years after the fertilization. The CO2 emissions of the decomposing peat (heterotrophic respiration) were measured from study plots where

  17. Boreal forests, aerosols and the impacts on clouds and climate.

    Science.gov (United States)

    Spracklen, Dominick V; Bonn, Boris; Carslaw, Kenneth S

    2008-12-28

    Previous studies have concluded that boreal forests warm the climate because the cooling from storage of carbon in vegetation and soils is cancelled out by the warming due to the absorption of the Sun's heat by the dark forest canopy. However, these studies ignored the impacts of forests on atmospheric aerosol. We use a global atmospheric model to show that, through emission of organic vapours and the resulting condensational growth of newly formed particles, boreal forests double regional cloud condensation nuclei concentrations (from approx. 100 to approx. 200 cm(-3)). Using a simple radiative model, we estimate that the resulting change in cloud albedo causes a radiative forcing of between -1.8 and -6.7 W m(-2) of forest. This forcing may be sufficiently large to result in boreal forests having an overall cooling impact on climate. We propose that the combination of climate forcings related to boreal forests may result in an important global homeostasis. In cold climatic conditions, the snow-vegetation albedo effect dominates and boreal forests warm the climate, whereas in warmer climates they may emit sufficiently large amounts of organic vapour modifying cloud albedo and acting to cool climate.

  18. 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.

  19. Relationships between Structure, Composition, and Dynamics of the Pristine Northern Boreal Forest and Air Temperature, Precipitation, and Soil Texture in Quebec (Canada

    Directory of Open Access Journals (Sweden)

    Louis Duchesne

    2009-01-01

    Full Text Available This study reports on the contemporary structure, composition, and dynamics of the pristine northern boreal forest in Quebec, Canada, associated with air temperature, precipitation, and soil texture, using 147 permanent sample plots located at the limit of continuous forest in Quebec. The results show that tree species composition of stands is associated with stand age, soil texture, air temperature, and precipitation regime. After establishment of the pioneer cohort, the postsuccessional stand dynamics differed among temperature and precipitation regimes, probably because of their influence on tree growth. Our results support the hypothesis that shifts in forest composition related to stand dynamics and the subsequent senescing phase associated with the old growth stage generally occur sooner and proceed faster on more fertile sites due to quicker growth and the subsequent earlier mortality of pioneer species. This study suggests that climate warming should accelerate the successional dynamics of these ecosystems through its positive influence on tree growth.

  20. 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.

  1. Bioinduced weathering in Swedish boreal forest soil investigated by mineral amendment

    Science.gov (United States)

    Olofsson, Madelen; Ahmed, Engy; Bylund, Dan; Holmström, Sara

    2013-04-01

    The purpose of this study was to investigate how soil mineral amendment affects microbial composition and how different mineral composition and varied depth influence these changes. Apatite, biotite and oligoclase were placed at soil horizon interfaces in a podzole in Bispgården, central Sweden (63°07'N, 16°70'E), between the summer of 2009 and 2011. Continuous measurement of soil chemistry; pH, dissolved organic carbon (DOC) and low molecular mass organic acids (LMMOAs) was performed for the surrounding soil during the frost free months of the two-year incubation period. Mineral sample surfaces were investigated using scanning electron microscopy (SEM) pre and post soil incubation to give a visual verification of weathering effects. Evaluating soil chemistry data and data received at the end of the incubation period, results show that the highest concentration of LMMOAs is found in the E horizon and that it corresponds with the highest total fungal activity in the bulk soil. Total microbial activity was found to be highest in the O horizon. Measurements on the soil of the mineral surfaces show that in all cases, apatite stimulates the microbial activity the most, followed by biotite and last oligoclase. Comparing the soil horizons, effects on total microbial activity are the highest in the E horizon, but when looking at total fungal activity the biggest changes are found in O and B horizon indicating that bacterial and fungal activities are affected differently by mineral amendment. Using ANOVA followed by pair wise comparisons according to Tukey, significant differences were found in microbial activity between the soil horizons and also between most of the different minerals, compared with the bulk soil. Looking at the SEM images taken before and after weathering, minerals placed in the O and E horizon are clearly the most affected, and the magnitude of weathering between the different minerals corresponds to the microbial activity found.

  2. Soil-to-plant transfer of elements is not linear: Results for five elements relevant to radioactive waste in five boreal forest species

    Energy Technology Data Exchange (ETDEWEB)

    Tuovinen, Tiina S.; Roivainen, Paeivi, E-mail: paivi.roivainen@uef.fi; Makkonen, Sari; Kolehmainen, Mikko; Holopainen, Toini; Juutilainen, Jukka

    2011-12-01

    Element-specific concentration ratios (CRs) assuming that plant uptake of elements is linear are commonly used in radioecological modelling to describe the soil-to-plant transfer of elements. The goal of this study was to investigate the validity of the linearity assumption in boreal forest plants, for which only limited relevant data are available. The soil-to-plant transfer of three essential (Mo, Ni, Zn) and two non-essential (Pb, U) elements relevant to the safety of radioactive waste disposal was studied. Three understory species (blueberry, narrow buckler fern and May lily) and two tree species (Norway spruce and rowan) were included. Examining CRs as a function of soil concentration showed that CR was not constant but decreased with increasing soil concentrations for all elements and plant species. A non-linear equation fitted fairly well with the empirical data; the R{sup 2}-values for this equation were constantly higher than those for the linear fit. The difference between the two fits was most evident at low soil concentrations where the use of constant CRs underestimated transfer from soil to plants. Site-specific factors affected the transfer of Mo and Ni. The results suggested that systematic variation with soil concentrations explains a part of the large variation of empirically determined CRs, and the accuracy of modelling the soil-to-plant transfer might be improved by using non-linear methods. Non-linearity of soil-to-plant transfer has been previously reported for a few different species, elements and environments. The present study systematically tested the linearity assumption for five elements (both essential and non-essential) and in five boreal forest species representing different growth traits and phylogenies. The data supported non-linearity in all cases.

  3. 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.

  4. From soil water to surface water - how the riparian zone controls element transport from a boreal forest to a stream

    Science.gov (United States)

    Lidman, Fredrik; Boily, Åsa; Laudon, Hjalmar; Köhler, Stephan J.

    2017-06-01

    Boreal headwaters are often lined by strips of highly organic soils, which are the last terrestrial environment to leave an imprint on discharging groundwater before it enters a stream. Because these riparian soils are so different from the Podzol soils that dominate much of the boreal landscape, they are known to have a major impact on the biogeochemistry of important elements such as C, N, P and Fe and the transfer of these elements from terrestrial to aquatic ecosystems. For most elements, however, the role of the riparian zone has remained unclear, although it should be expected that the mobility of many elements is affected by changes in, for example, pH, redox potential and concentration of organic carbon as they are transported through the riparian zone. Therefore, soil water and groundwater was sampled at different depths along a 22 m hillslope transect in the Krycklan catchment in northern Sweden using soil lysimeters and analysed for a large number of major and trace elements (Al, As, B, Ba, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, La, Li, Mg, Mn, Na, Ni, Pb, Rb, Se, Si, Sr, Th, Ti, U, V, Zn, Zr) and other parameters such as sulfate and total organic carbon (TOC). The results showed that the concentrations of most investigated elements increased substantially (up to 60 times) as the water flowed from the uphill mineral soils and into the riparian zone, largely as a result of higher TOC concentrations. The stream water concentrations of these elements were typically somewhat lower than in the riparian zone, but still considerably higher than in the uphill mineral soils, which suggests that riparian soils have a decisive impact on the water quality of boreal streams. The degree of enrichment in the riparian zone for different elements could be linked to the affinity for organic matter, indicating that the pattern with strongly elevated concentrations in riparian soils is typical for organophilic substances. One likely explanation is that the solubility of many

  5. The incorporation of an organic soil layer in the Noah-MP land surface model and its evaluation over a boreal aspen forest

    Science.gov (United States)

    Chen, Liang; Li, Yanping; Chen, Fei; Barr, Alan; Barlage, Michael; Wan, Bingcheng

    2016-07-01

    A thick top layer of organic matter is a dominant feature in boreal forests and can impact land-atmosphere interactions. In this study, the multi-parameterization version of the Noah land surface model (Noah-MP) was used to investigate the impact of incorporating a forest-floor organic soil layer on the simulated surface energy and water cycle components at the BERMS Old Aspen site (OAS) field station in central Saskatchewan, Canada. Compared to a simulation without an organic soil parameterization (CTL), the Noah-MP simulation with an organic soil (OGN) improved Noah-MP-simulated soil temperature profiles and soil moisture at 40-100 cm, especially the phase and amplitude (Seasonal cycle) of soil temperature below 10 cm. OGN also enhanced the simulation of sensible and latent heat fluxes in spring, especially in wet years, which is mostly related to the timing of spring soil thaw and warming. Simulated top-layer soil moisture is better in OGN than that in CTL. The effects of including an organic soil layer on soil temperature are not uniform throughout the soil depth and are more prominent in summer. For drought years, the OGN simulation substantially modified the partitioning of water between direct soil evaporation and vegetation transpiration. For wet years, the OGN-simulated latent heat fluxes are similar to CTL except for the spring season when OGN produced less evaporation, which was closer to observations. Including organic soil produced more subsurface runoff and resulted in much higher runoff throughout the freezing periods in wet years.

  6. 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

  7. 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

  8. Modeling boreal fire and forest dynamics

    Science.gov (United States)

    de Groot, W. J.; McRae, D. J.; Cantin, A.

    2009-04-01

    The circumpolar boreal forest covers about 1.4 billion ha, representing 1/3 of global forest land. Approximately 2/3 of the boreal forest is located in Eurasia and the remainder in North America. Wildland fires annually burn an estimated 12-20 M ha across the entire boreal region, having a major influence on forest structure and composition. However, fire weather, fire behaviour, and fire ecology differ greatly between the boreal forests in eastern and western hemispheres, which have significant impact on tree survival, post-fire regeneration and forest succession. Every year, wildland fires in Canada and Alaska burn an average of 2-3 M ha, primarily by stand-replacing, high intensity crown fires. By comparison, Russian fires burn about 10-15 M ha annually, primarily by low to moderate intensity surface fires that cause minimal tree mortality. Fire weather conditions in the most fire prone regions of Russia are generally more severe than in similar regions of North America. Finally, the species composition of eastern and western boreal forests is also very different. Russian forests are dominated by larch (30%) and pine (28%) with lower components of spruce (14%) and poplar/birch hardwoods (18%) By contrast, Canadian forests are comprised mainly of spruce (35%), pine (22%), poplar/birch (16%), and fir (9%). All of these factors contribute to the variability in vegetation dynamics occurring within the circumpolar boreal region. This modeling study examines the interactions of fire weather, forest composition, fire behaviour, and fire ecology on forest vegetation dynamics within the boreal region. Similar active fire zones in western Canada and eastern Siberia were used as study sites. Historical weather data were collected for both locations and used to calculate fire weather data, which were used as primary driving variables for the Boreal Fire Effects model (BORFIRE). Fire behaviour was calculated in BORFIRE using data for major tree species at both study sites

  9. 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...

  10. The role of soil drainage class in carbon dioxide exchange and decomposition in boreal black spruce (Picea mariana) forest stands

    Science.gov (United States)

    Wickland, K.P.; Neff, J.C.; Harden, J.W.

    2010-01-01

    Black spruce (Picea mariana (Mill.) B.S.P.) forest stands range from well drained to poorly drained, typically contain large amounts of soil organic carbon (SOC), and are often underlain by permafrost. To better understand the role of soil drainage class in carbon dioxide (CO2) exchange and decomposition, we measured soil respiration and net CO2 fluxes, litter decomposition and litterfall rates, and SOC stocks above permafrost in three Alaska black spruce forest stands characterized as well drained (WD), moderately drained (MD), and poorly drained (PD). Soil respiration and net CO2 fluxes were not significantly different among sites, although the relation between soil respiration rate and temperature varied with site (Qw: WD > MD > PD). Annual estimated soil respiration, litter decomposition, and groundcover photosynthesis were greatest at PD. These results suggest that soil temperature and moisture conditions in shallow organic horizon soils at PD were more favorable for decomposition compared with the better drained sites. SOC stocks, however, increase from WD to MD to PD such that surface decomposition and C storage are diametric. Greater groundcover vegetation productivity, protection of deep SOC by permafrost and anoxic conditions, and differences in fire return interval and (or) severity at PD counteract the relatively high near-surface decomposition rates, resulting in high net C accumulation.

  11. Soil response to a 3-year increase in temperature and nitrogen deposition measured in a mature boreal forest using ion-exchange membranes.

    Science.gov (United States)

    D'Orangeville, Loïc; Houle, Daniel; Côté, Benoît; Duchesne, Louis

    2014-12-01

    The projected increase in atmospheric N deposition and air/soil temperature will likely affect soil nutrient dynamics in boreal ecosystems. The potential effects of these changes on soil ion fluxes were studied in a mature balsam fir stand (Abies balsamea [L.] Mill) in Quebec, Canada that was subjected to 3 years of experimentally increased soil temperature (+4 °C) and increased inorganic N concentration in artificial precipitation (three times the current N concentrations using NH4NO3). Soil element fluxes (NO3, NH4, PO4, K, Ca, Mg, SO4, Al, and Fe) in the organic and upper mineral horizons were monitored using buried ion-exchange membranes (PRS™ probes). While N additions did not affect soil element fluxes, 3 years of soil warming increased the cumulative fluxes of K, Mg, and SO4 in the forest floor by 43, 44, and 79 %, respectively, and Mg, SO4, and Al in the mineral horizon by 29, 66, and 23 %, respectively. We attribute these changes to increased rates of soil organic matter decomposition. Significant interactions of the heating treatment with time were observed for most elements although no clear seasonal patterns emerged. The increase in soil K and Mg in heated plots resulted in a significant but small K increase in balsam fir foliage while no change was observed for Mg. A 6-15 % decrease in foliar Ca content with soil warming could be related to the increase in soil-available Al in heated plots, as Al can interfere with the root uptake of Ca.

  12. DOM composition and transformation in boreal forest soils: The effects of temperature and organic-horizon decomposition state

    Science.gov (United States)

    O'Donnell, Jonathan A.; Aiken, George R.; Butler, Kenna D.; Guillemette, Francois; Podgorski, David C.; Spencer, Robert G. M.

    2016-10-01

    The boreal region stores large amounts of organic carbon (C) in organic-soil horizons, which are vulnerable to destabilization via warming and disturbance. Decomposition of soil organic matter (SOM) contributes to the production and turnover of dissolved organic matter (DOM). While temperature is a primary control on rates of SOM and DOM cycling, little is known about temperature effects on DOM composition in soil leachate. Here we conducted a 30 day incubation to examine the effects of temperature (20 versus 5°C) and SOM decomposition state (moss versus fibric versus amorphous horizons) on DOM composition in organic soils of interior Alaska. We characterized DOM using bulk dissolved organic C (DOC) concentration, chemical fractionation, optical properties, and ultrahigh-resolution mass spectrometry. We observed an increase in DOC concentration and DOM aromaticity in the 20°C treatment compared to the 5°C treatment. Leachate from fibric horizons had higher DOC concentration than shallow moss or deep amorphous horizons. We also observed chemical shifts in DOM leachate over time, including increases in hydrophobic organic acids, polyphenols, and condensed aromatics and decreases in low-molecular weight hydrophilic compounds and aliphatics. We compared ultrahigh-resolution mass spectrometry and optical data and observed strong correlations between polyphenols, condensed aromatics, SUVA254, and humic-like fluorescence intensities. These findings suggest that biolabile DOM was preferentially mineralized, and the magnitude of this transformation was determined by kinetics (i.e., temperature) and substrate quality (i.e., soil horizon). With future warming, our findings indicate that organic soils may release higher concentrations of aromatic DOM to aquatic ecosystems.

  13. DOM composition and transformation in boreal forest soils: The effects of temperature and organic-horizon decomposition state

    Science.gov (United States)

    O’Donnell, Jonathan A.; Aiken, George R.; Butler, Kenna D.; Guillemette, Francois; Podgorski, David C.; Spencer, Robert G. M.

    2016-01-01

    The boreal region stores large amounts of organic carbon (C) in organic-soil horizons, which are vulnerable to destabilization via warming and disturbance. Decomposition of soil organic matter (SOM) contributes to the production and turnover of dissolved organic matter (DOM). While temperature is a primary control on rates of SOM and DOM cycling, little is known about temperature effects on DOM composition in soil leachate. Here we conducted a 30 day incubation to examine the effects of temperature (20 versus 5°C) and SOM decomposition state (moss versus fibric versus amorphous horizons) on DOM composition in organic soils of interior Alaska. We characterized DOM using bulk dissolved organic C (DOC) concentration, chemical fractionation, optical properties, and ultrahigh-resolution mass spectrometry. We observed an increase in DOC concentration and DOM aromaticity in the 20°C treatment compared to the 5°C treatment. Leachate from fibric horizons had higher DOC concentration than shallow moss or deep amorphous horizons. We also observed chemical shifts in DOM leachate over time, including increases in hydrophobic organic acids, polyphenols, and condensed aromatics and decreases in low-molecular weight hydrophilic compounds and aliphatics. We compared ultrahigh-resolution mass spectrometry and optical data and observed strong correlations between polyphenols, condensed aromatics, SUVA254, and humic-like fluorescence intensities. These findings suggest that biolabile DOM was preferentially mineralized, and the magnitude of this transformation was determined by kinetics (i.e., temperature) and substrate quality (i.e., soil horizon). With future warming, our findings indicate that organic soils may release higher concentrations of aromatic DOM to aquatic ecosystems.

  14. Boreal Forest Watch: A BOREAS Outreach Program

    Science.gov (United States)

    Rock, Barrett N.

    1999-01-01

    The Boreal Forest Watch program was initiated in the fall of 1994 to act as an educational outreach program for the BOREAS project in both the BOREAS Southern Study Area (SSA) and Northern Study Area (NSA). Boreal Forest Watch (13FW) was designed to introduce area high school teachers and their students to the types of research activities occurring as part of the BOREAS study of Canadian boreal forests. Several teacher training workshops were offered to teachers from central and northern Saskatchewan and northern Manitoba between May, 1995 and February, 1999; teachers were introduced to techniques for involving their students in on-going environmental monitoring studies within local forested stands. Boreal Forest Watch is an educational outreach program which brings high school students and research scientists together to study the forest and foster a sustainable relationship between people and the planetary life-support system we depend upon. Personnel from the University of New Hampshire (UNH), Complex Systems Research Center (CSRC), with the cooperation from the Prince Albert National Park (PANP), instituted this program to help teachers within the BOREAS Study Areas offer real science research experience to their students. The program has the potential to complement large research projects, such as BOREAS, by providing useful student- collected data to scientists. Yet, the primary goal of BFW is to allow teachers and students to experience a hands-on, inquiry-based approach to leaming science - emulating the process followed by research scientists. In addition to introducing these teachers to on-going BOREAS research, the other goals of the BFW program were to: 1) to introduce authentic science topics and methods to students and teachers through hands-on, field-based activities; and, 2) to build a database of student-collected environmental monitoring data for future global change studies in the boreal region.

  15. Boreal Forest Fires - Behavior and Atmospheric Impacts

    Science.gov (United States)

    Stocks, B. J.

    2003-12-01

    Fire is a natural and essential stand-renewing agent in circumboreal forests, and eliminating fire in this region is neither economically possible nor ecologically desirable. In general, boreal fire is managed on the basis of values-at-risk, with high levels of protection afforded to economically and recreationally important areas, while fire is permitted to burn naturally in many remote areas. Current estimates are that an average of 5-15 million hectares burn annually across the boreal zone, with at least 50% of the area burning in largely unmanaged forest. High-intensity crown fires account for the vast majority of the area burned in the boreal zone, particularly in North America. These fires typically consume 20-30 tonnes/ha of fuel, spread at rates up to 100 m/min, and generate intensity levels (or energy release rates) approaching 100,000 kW/m of fire front. Deep forest floor (organic) layers common to boreal forests contribute significantly to high levels of fuel consumption and assist in the propagation of crown fires. When crown fires are sustained through a peak afternoon burning period, they usually produce towering convection columns that can reach the upper troposphere directly. Numerous boreal fires columns reaching 11-14 kilometres in height have been documented in the fire literature. Given the lower altitude of the tropopause at boreal zone latitudes it is not surprising that some boreal fire columns have been recently reported reaching the lower stratosphere. Current global and regional climate models suggest a significant increase in both the severity and frequency of boreal fires under a changing climate, with potentially major impacts on terrestrial carbon storage and the global carbon budget, as well as hemispheric smoke transport. Modelling convection column dynamics is essential to predicting the future transport and atmospheric impacts of boreal fire smoke, and this science requires a solid understanding of fuel consumption and fire

  16. The browning of Alaska's boreal forest

    Science.gov (United States)

    Mary Beth Parent; David. Verbyla

    2010-01-01

    We used twelve Landsat scenes from the 1980s-2009 and regional 2000-2009 MODIS data to examine the long-term trend in the normalized difference vegetation index (NDVI) within unburned areas of the Alaskan boreal forest. Our analysis shows that there has been a declining trend in NDVI in this region, with the strongest "browning trend" occurring in eastern...

  17. 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

  18. The Boreal Virtual Forest. [CD-ROM].

    Science.gov (United States)

    Indiana Univ.-Purdue Univ., Indianapolis.

    This CD-ROM is an educational CD-ROM aimed at classroom audiences in 5th grade and above. Using QuickTime Virtual Reality (QTVR), the Boreal Virtual Forest is designed so that students are able to see views from inside the central hardwood forest and look up or down or spin around 360 degrees. The program allows students to become familiar with…

  19. 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.

  20. Lichen conservation in heavily managed boreal forests.

    Science.gov (United States)

    McMullin, Richard Troy; Thompson, Ian D; Newmaster, Steven G

    2013-10-01

    Lichens are an important component of the boreal forest, where they are long lived, tend to accumulate in older stands, and are a major food source for the threatened woodland caribou (Rangifer tarandus caribou). To be fully sustainable, silvicultural practices in the boreal forest must include the conservation of ecological integrity. Dominant forest management practices, however, have short-term negative effects on lichen diversity, particularly the application of herbicides. To better understand the long-term effects of forest management, we examined lichen regeneration in 35 mixed black spruce (Picea mariana) and jack pine (Pinus banksiana) forest stands across northern Ontario to determine recovery following logging and postharvest silvicultural practices. Our forest stands were 25-40 years old and had undergone 3 common sivilcultural treatments that included harvested and planted; harvested, planted, and treated with N-[phosphonomethyl] glycine (glyphosate); and harvested, planted, and treated with 2,4-dichlorophenoxyacetic acid (2,4-D). Forest stands with herbicide treatments had lower lichen biomass and higher beta and gamma diversity than planted stands that were not treated chemically or control stands. In northwestern Ontario, planted stands that were not treated chemically had significantly greater (p < 0.05) alpha diversity than stands treated with herbicides or control stands. Our results show that common silvicultural practices do not emulate natural disturbances caused by wildfires in the boreal forest for the lichen community. We suggest a reduction in the amount of chemical application be considered in areas where lichen biomass is likely to be high and where the recovery of woodland caribou is an objective. © 2013 Society for Conservation Biology.

  1. Browning boreal forests of western North America

    Science.gov (United States)

    Verbyla, David

    2011-12-01

    The GIMMS NDVI dataset has been widely used to document a 'browning trend' in North American boreal forests (Goetz et al 2005, Bunn et al 2007, Beck and Goetz 2011). However, there has been speculation (Alcaraz-Segura et al 2010) that this trend may be an artifact due to processing algorithms rather than an actual decline in vegetation activity. This conclusion was based primarily on the fact that GIMMS NDVI did not capture NDVI recovery within most burned areas in boreal Canada, while another dataset consistently showed post-fire increasing NDVI. I believe that the results of Alcaraz-Segura et al (2010) were due simply to different pixel sizes of the two datasets (64 km2 versus 1 km2 pixels). Similar results have been obtained from tundra areas greening in Alaska, with the results simply due to these pixel size differences (Stow et al 2007). Furthermore, recent studies have documented boreal browning trends based on NDVI from other sensors. Beck and Goetz (2011) have shown the boreal browning trend derived from a different sensor (MODIS) to be very similar to the boreal browning trend derived from the GIMMS NDVI dataset for the circumpolar boreal region. Parent and Verbyla (2010) found similar declining NDVI patterns based on NDVI from Landsat sensors and GIMMS NDVI in boreal Alaska. Zhang et al (2008) found a similar 'browning trend' in boreal North America based on a production efficiency model using an integrated AVHRR and MODIS dataset. The declining NDVI trend in areas of boreal North America is consistent with tree-ring studies (D'Arrigo et al 2004, McGuire et al 2010, Beck et al 2011). The decline in tree growth may be due to temperature-induced drought stress (Barber et al 2000) caused by higher evaporative demands in a warming climate (Lloyd and Fastie 2002). In a circumpolar boreal study, Lloyd and Bunn (2007) found that a negative relationship between temperature and tree-ring growth occurred more frequently in warmer parts of species' ranges

  2. Effects of different tree species on soil organic matter composition, decomposition rates and temperature sensitivities in boreal forest

    Science.gov (United States)

    Segura, Javier; Nilsson, Mats B.; Erhagen, Björn; Sparrman, Tobias; Ilstedt, Ulrik; Schleucher, Jürgen; Öquist, Mats

    2017-04-01

    High-latitude ecosystems store a large proportion of the global soil organic matter (SOM) and its mineralization constitutes a major carbon flux to the atmosphere. It has been suggested that different tree species can significantly influence organo-chemical composition of SOM, and rate and temperature sensitivity of SOM decomposition. In this study we used surface soil samples (top 5 cm) from a field experiment where five different tree species (Pinus silvestrys L, Picea abies (L.) H. Karst., Larix decidua Mill., Betula pendula Roth, and Pinus contorta Douglas) were planted on a grass meadow in a randomized block design (n=3) ca. 40 years ago. The samples were incubated at 4, 9, 14, and 19 °C at a soil water potential of -25 kPa (previously determined as optimal water content for decomposition). CO2 production rates were measured hourly for 13 days. CO2 production rates were consequently lowest in the control plots and increased in the order Meadow< Contorta < Betula < Larix < Pinus < Picea. The values ranged between 0.03-0.1, 0.06-0.154, 0.1-0.24 and 0.13-0.36 mg CO2 g-1 OM (dw) h-1 at 4, 9, 14 and 19°C respectively. The temperature response of CO2 production corresponded to Q10s of 2.22 (±0.11), 2.22(±0.15), 2.66 (±0.18), 2.09 (±0.33), 2.38 (±0.31) and 2.31 (±0.09) for meadow, contorta, betula, larix, pinus and picea respectively. Only betula resulted in significantly higher Q10s as compared to the control plots, picea, contorta and larix treatments. These differences in tree species effects on SOM decomposition and its temperature sensitivity will be further discussed in relation to the organo-chemical composition of SOM as determined by pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) and nuclear magnetic resonance spectroscopy (NMR) techniques. We conclude that the temperature response of SOM decomposition rates is likely coupled to tree species composition and may have important implications for soil C dynamics. This finding can have

  3. 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.

  4. Soil processes and tree growth at shooting ranges in a boreal forest reflect contamination history and lead-induced changes in soil food webs.

    Science.gov (United States)

    Selonen, Salla; Setälä, Heikki

    2015-06-15

    The effects of shooting-derived lead (Pb) on the structure and functioning of a forest ecosystem, and the recovery of the ecosystem after range abandonment were studied at an active shotgun shooting range, an abandoned shooting range where shooting ceased 20 years earlier and an uncontaminated control site. Despite numerous lead-induced changes in the soil food web, soil processes were only weakly related to soil food web composition. However, decomposition of Scots pine (Pinus sylvestris) needle litter was retarded at the active shooting range, and microbial activity, microbial biomass and the rate of decomposition of Pb-contaminated grass litter decreased with increasing soil Pb concentrations. Tree (P. sylvestris) radial growth was suppressed at the active shooting range right after shooting activities started. In contrast, the growth of pines improved at the abandoned shooting range after the cessation of shooting, despite reduced nitrogen and phosphorus contents of the needles. Higher litter degradation rates and lower Pb concentrations in the topmost soil layer at the abandoned shooting range suggest gradual recovery after range abandonment. Our findings suggest that functions in lead-contaminated coniferous forest ecosystems depend on the successional stage of the forest as well as the time since the contamination source has been eliminated, which affects, e.g., the vertical distribution of the contaminant in the soil. However, despite multiple lead-induced changes throughout the ecosystem, the effects were rather weak, indicating high resistance of coniferous forest ecosystems to this type of stress. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. 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

  6. 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.

  7. Nutrient leaching, soil pH and changes in microbial community increase with time in lead-contaminated boreal forest soil at a shooting range area.

    Science.gov (United States)

    Selonen, Salla; Setälä, Heikki

    2017-02-01

    Despite the known toxicity of lead (Pb), Pb pellets are widely used at shotgun shooting ranges over the world. However, the impacts of Pb on soil nutrients and soil microbes, playing a crucial role in nutrient cycling, are poorly understood. Furthermore, it is unknown whether these impacts change with time after the cessation of shooting. To shed light on these issues, three study sites in the same coniferous forest in a shooting range area were studied: an uncontaminated control site and an active and an abandoned shooting range, both sharing a similar Pb pellet load in the soil, but the latter with a 20-year longer contamination history. Soil pH and nitrate concentration increased, whilst soil phosphate concentration and fungal phospholipid fatty acid (PLFA) decreased due to Pb contamination. Our results imply that shooting-derived Pb can influence soil nutrients and microbes not only directly but also indirectly by increasing soil pH. However, these mechanisms cannot be differentiated here. Many of the Pb-induced changes were most pronounced at the abandoned range, and nutrient leaching was increased only at that site. These results suggest that Pb disturbs the structure and functions of the soil system and impairs a crucial ecosystem service, the ability to retain nutrients. Furthermore, the risks of shooting-derived Pb to the environment increase with time.

  8. 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

  9. Nitrogen balance along a northern boreal forest fire chronosequence.

    Science.gov (United States)

    Palviainen, Marjo; Pumpanen, Jukka; Berninger, Frank; Ritala, Kaisa; Duan, Baoli; Heinonsalo, Jussi; Sun, Hui; Köster, Egle; Köster, Kajar

    2017-01-01

    Fire is a major natural disturbance factor in boreal forests, and the frequency of forest fires is predicted to increase due to climate change. Nitrogen (N) is a key determinant of carbon sequestration in boreal forests because the shortage of N limits tree growth. We studied changes in N pools and fluxes, and the overall N balance across a 155-year non stand-replacing fire chronosequence in sub-arctic Pinus sylvestris forests in Finland. Two years after the fire, total ecosystem N pool was 622 kg ha-1 of which 16% was in the vegetation, 8% in the dead biomass and 76% in the soil. 155 years after the fire, total N pool was 960 kg ha-1, with 27% in the vegetation, 3% in the dead biomass and 69% in the soil. This implies an annual accumulation rate of 2.28 kg ha-1 which was distributed equally between soil and biomass. The observed changes in N pools were consistent with the computed N balance +2.11 kg ha-1 yr-1 over the 155-year post-fire period. Nitrogen deposition was an important component of the N balance. The biological N fixation increased with succession and constituted 9% of the total N input during the 155 post-fire years. N2O fluxes were negligible (≤ 0.01 kg ha-1 yr-1) and did not differ among post-fire age classes. The number and intensity of microbial genes involved in N cycling were lower at the site 60 years after fire compared to the youngest and the oldest sites indicating potential differences in soil N cycling processes. The results suggest that in sub-arctic pine forests, the non-stand-replacing, intermediate-severity fires decrease considerably N pools in biomass but changes in soil and total ecosystem N pools are slight. Current fire-return interval does not seem to pose a great threat to ecosystem productivity and N status in these sub-arctic forests.

  10. 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.

  11. Variation in carbon storage and its distribution by stand age and forest type in boreal and temperate forests in northeastern China.

    Science.gov (United States)

    Wei, Yawei; Li, Maihe; Chen, Hua; Lewis, Bernard J; Yu, Dapao; Zhou, Li; Zhou, Wangming; Fang, Xiangmin; Zhao, Wei; Dai, Limin

    2013-01-01

    The northeastern forest region of China is an important component of total temperate and boreal forests in the northern hemisphere. But how carbon (C) pool size and distribution varies among tree, understory, forest floor and soil components, and across stand ages remains unclear. To address this knowledge gap, we selected three major temperate and two major boreal forest types in northeastern (NE) China. Within both forest zones, we focused on four stand age classes (young, mid-aged, mature and over-mature). Results showed that total C storage was greater in temperate than in boreal forests, and greater in older than in younger stands. Tree biomass C was the main C component, and its contribution to the total forest C storage increased with increasing stand age. It ranged from 27.7% in young to 62.8% in over-mature stands in boreal forests and from 26.5% in young to 72.8% in over-mature stands in temperate forests. Results from both forest zones thus confirm the large biomass C storage capacity of old-growth forests. Tree biomass C was influenced by forest zone, stand age, and forest type. Soil C contribution to total forest C storage ranged from 62.5% in young to 30.1% in over-mature stands in boreal and from 70.1% in young to 26.0% in over-mature in temperate forests. Thus soil C storage is a major C pool in forests of NE China. On the other hand, understory and forest floor C jointly contained less than 13% and boreal and temperate forests respectively, and thus play a minor role in total forest C storage in NE China.

  12. Estimating post-fire organic soil depth in the Alaskan boreal forest using the Normalized Burn Ratio

    Science.gov (United States)

    D. Verbyla; R. Lord

    2008-01-01

    As part of a long-term moose browse/fire severity study, we used the Normalized Burn Ratio (NBR) with historic Landsat Thematic Mapper (TM) imagery to estimate fire severity from a 1983 wildfire in interior Alaska. Fire severity was estimated in the field by measuring the depth of the organic soil at 57 sites during the summer of 2006. Sites were selected for field...

  13. 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.

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

    Directory of Open Access Journals (Sweden)

    Xiuchen Wu

    Full Text Available 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.

  15. Fire and the changing face of the boreal forest

    Science.gov (United States)

    Lyons, E. A.

    2016-12-01

    Fire disturbance is a primary driver of land cover distributions in the boreal forest and it is broadly expected to increase in both intensity and area burned. This change will have impacts on the overall pattern of land cover within the boreal forest and on how it interacts with the atmosphere, neighboring biomes, and the global climate system. This study investigates changes to the spatial patterns of forest cover in boreal North America due to fire at the local and biome scale. First, at the local scale, the pattern of forest cover patches within burned areas were found to be larger, more regularly shaped, and clustered than unburned forest. These metrics, however, returned to pre-fire levels relatively quickly. Fires at the biome scale fires tended to decrease landscape heterogeneity.

  16. 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...

  17. The changing effects of Alaska's boreal forest on the climate system

    Science.gov (United States)

    E.S. Euskirchen; A.D. McGuire; F.S. Chapin; T.S. Rupp

    2010-01-01

    In the boreal forests of Alaska, recent changes in climate have influenced the exchange of trace gases, water, and energy between these forests and the atmosphere. These changes in the structure and function of boreal forests can then feed back to impact regional and global climates. We examine the type and magnitude of the climate feedbacks from boreal forests in...

  18. Deciduous trees are a large and overlooked sink for snowmelt water in the boreal forest

    Science.gov (United States)

    Young, Jessica; Bolton, W. Robert; Bhatt, Uma; Cristobal, Jordi; Thoman, Richard

    2016-01-01

    The terrestrial water cycle contains large uncertainties that impact our understanding of water budgets and climate dynamics. Water storage is a key uncertainty in the boreal water budget, with tree water storage often ignored. The goal of this study is to quantify tree water content during the snowmelt and growing season periods for Alaskan and western Canadian boreal forests. Deciduous trees reached saturation between snowmelt and leaf-out, taking up 21–25% of the available snowmelt water, while coniferous trees removed boreal deciduous tree area is expected to increase by 1–15%, potentially resulting in an additional 0.3–3 billion m3 of snowmelt water removed from the soil per year. This study is the first to show that deciduous tree water uptake of snowmelt water represents a large but overlooked aspect of the water balance in boreal watersheds.

  19. Large impacts of climatic warming on growth of boreal forests since 1960.

    Science.gov (United States)

    Kauppi, Pekka E; Posch, Maximilian; Pirinen, Pentti

    2014-01-01

    Boreal forests are sensitive to climatic warming, because low temperatures hold back ecosystem processes, such as the mobilization of nitrogen in soils. A greening of the boreal landscape has been observed using remote sensing, and the seasonal amplitude of CO2 in the northern hemisphere has increased, indicating warming effects on ecosystem productivity. However, field observations on responses of ecosystem productivity have been lacking on a large sub-biome scale. Here we report a significant increase in the annual growth of boreal forests in Finland in response to climatic warming, especially since 1990. This finding is obtained by linking meteorological records and forest inventory data on an area between 60° and 70° northern latitude. An additional increase in growth has occurred in response to changes in other drivers, such as forest management, nitrogen deposition and/or CO2 concentration. A similar warming impact can be expected in the entire boreal zone, where warming takes place. Given the large size of the boreal biome - more than ten million km2- important climate feedbacks are at stake, such as the future carbon balance, transpiration and albedo.

  20. 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.

  1. 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.

  2. 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.

  3. 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

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

    Science.gov (United States)

    Lara, Mark J; Genet, Hélène; McGuire, Anthony D; Euskirchen, Eugénie S; Zhang, Yujin; Brown, Dana R N; Jorgenson, Mark T; Romanovsky, Vladimir; Breen, Amy; Bolton, William R

    2016-02-01

    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

  5. 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

  6. 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

  7. Investigations of boreal forest bidirectional reflectance factor

    Science.gov (United States)

    White, H. Peter

    To monitor the Earth's biosphere using satellites, remote sensing science must develop robust forest reflectance models with which to extract canopy properties such as leaf area index, biomass, and percentage canopy cover from observed canopy reflectance values. At present such algorithms are generally based on regression equations which have been derived and evaluated at localized areas of solar zenith and view angles, and incorporate a priori knowledge of the scene. Of particular interest here is the treatment of the understorey which has distinct spectral reflectance properties. Recent studies suggest this layer in the boreal ecosphere has a significant influence on the CO2 budget during the northern growing season. Previous treatments of this layer in canopy reflectance models have been limited, often treating the layer as either non-reflecting, or isotropic with the same average reflectance as the overstorey. In-field observations demonstrate that this isn't the case. The recently developed Four-Scale Model [Chen and Leblanc, 1997] provides a new description of canopy reflectance that considers four levels of canopy architecture, the distributions of tree crowns, branches, shoots, and leaves. In doing so, the four proportions of sunlit and shaded overstorey and understorey are determined and treated as relevant contributors to the overall canopy reflectance. One purpose of this study is to examine the potential of further developing this model into a linear kernel form suitable for inversion, providing both the ability to extrapolate from observed reflectance values at certain view/illumination geometries to canopy BRF at other geometries and to allow extraction of information about the canopy based on observed BRF values. The FLAIR model (F_our- Scale L_inear Kernel Model for A_ni_sotropic R_eflectance) is the result of this development, following the philosophy that the model must remain applicable to a wide range of canopy types, understorey conditions, and

  8. Transpiration response of boreal forest plants to permafrost thaw

    Science.gov (United States)

    Cable, J.; Ogle, K.; Welker, J. M.

    2011-12-01

    than the site with stable permafrost. In terms of the "base" gs rate, current soil temperature positively affects gs in the deciduous functional types. The prior year's soil temperature positively affected the black spruce base rate at the end of the season, but negatively affected the evergreen sub-shrubs at the beginning of the season. Soil temperature the prior year's May was most important at the site with thawing permafrost, but May and June were important for the site with stable permafrost. These preliminary results suggest that (1) we must account for within-season and the prior year's antecedent conditions when quantifying the effects of permafrost thaw on plant function, and (2) permafrost thaw changes how boreal forest plant species respond to climate and soil conditions. Next, we must quantify the mechanisms of the antecedent response to determine thresholds in thaw that could result in shifts in species composition.

  9. Are ectomycorrhizal fungi alleviating or aggravating nitrogen limitation of tree growth in boreal forests?

    Science.gov (United States)

    Näsholm, Torgny; Högberg, Peter; Franklin, Oskar; Metcalfe, Daniel; Keel, Sonja G; Campbell, Catherine; Hurry, Vaughan; Linder, Sune; Högberg, Mona N

    2013-04-01

    Symbioses between plant roots and mycorrhizal fungi are thought to enhance plant uptake of nutrients through a favourable exchange for photosynthates. Ectomycorrhizal fungi are considered to play this vital role for trees in nitrogen (N)-limited boreal forests. We followed symbiotic carbon (C)-N exchange in a large-scale boreal pine forest experiment by tracing (13) CO(2) absorbed through tree photosynthesis and (15) N injected into a soil layer in which ectomycorrhizal fungi dominate the microbial community. We detected little (15) N in tree canopies, but high levels in soil microbes and in mycorrhizal root tips, illustrating effective soil N immobilization, especially in late summer, when tree belowground C allocation was high. Additions of N fertilizer to the soil before labelling shifted the incorporation of (15) N from soil microbes and root tips to tree foliage. These results were tested in a model for C-N exchange between trees and mycorrhizal fungi, suggesting that ectomycorrhizal fungi transfer small fractions of absorbed N to trees under N-limited conditions, but larger fractions if more N is available. We suggest that greater allocation of C from trees to ectomycorrhizal fungi increases N retention in soil mycelium, driving boreal forests towards more severe N limitation at low N supply. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  10. Water and heat transport in boreal soils: Implications for soil response to climate change

    Science.gov (United States)

    Fan, Z.; Neff, J.C.; Harden, J.W.; Zhang, T.; Veldhuis, H.; Czimczik, C.I.; Winston, G.C.; O'Donnell, J. A.

    2011-01-01

    Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4??C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30. years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate. ?? 2011 Elsevier B.V.

  11. Effects of wild fires on the emissions of reactive gases from boreal and subarctic soils

    Science.gov (United States)

    Zhang-Turpeinen, Huizhong; Pumpanen, Jukka; Kivimäenpää, Minna

    2017-04-01

    Wild fire has long-term effects on the ecosystem and biological processes of boreal forest, and the frequency of wild fires is increasing as a consequence of climate change. Boreal forests lie largely on permafrost area, and the increase in fire frequency or intensity will affect the depth of the active layer on top of permafrost. The thawing of permafrost soils and increase in the active layer depth could induce significant reactive trace gas emissions. Biogenic volatile organic compounds (BVOCs) and nitrous acid (HONO) are closely associated with air chemistry in the troposphere. They react easily with ozone, hydroxyl radicals, and the reaction products may condense into aerosol particles or affect the growth of atmospheric aerosols which act as cloud condensation nuclei. Forests, and in particular permafrost soils, could be potentially large sources of BVOCs and HONO, because of the large amount of decomposing litter and soil organic matter. However, the forest soil BVOC emissions are poorly known, in contrast to BVOCs emitted from branch and canopy levels in boreal forests. The production rates of HONO in various soils are also poorly known. We studied BVOC and HONO fluxes from boreal forest soils and the effects of wild fires and the time since the last fire on them. We measured BVOCs emissions in west Siberia larch forest stands on permafrost soil in a fire chronosequence where the last forest fires had occurred 2, 24, and more than 100 years ago. HONO emissions in northern boreal subarctic Scots pine forest stands in Eastern Lapland in Finland in a fire chronosequence where the last fires had occurred 7, 47, 72 and 157 years ago. BVOC flux measurements were carried out by drawing air samples from chamber headspace into a steel adsorbent tube containing Tenax TA and carbopack B. The sampling tubes were analyzed on gas chromatography-mass spectrometry (GC-MS). Soil samples were measured for HONO flux in laboratory with LOPAP (Long path absorption photometer

  12. 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.

  13. Boreal Forests Sequester Large Amounts of Mercury over Millennial Time Scales in the Absence of Wildfire.

    Science.gov (United States)

    Giesler, Reiner; Clemmensen, Karina E; Wardle, David A; Klaminder, Jonatan; Bindler, Richard

    2017-03-07

    Alterations in fire activity due to climate change and fire suppression may have profound effects on the balance between storage and release of carbon (C) and associated volatile elements. Stored soil mercury (Hg) is known to volatilize due to wildfires and this could substantially affect the land-air exchange of Hg; conversely the absence of fires and human disturbance may increase the time period over which Hg is sequestered. Here we show for a wildfire chronosequence spanning over more than 5000 years in boreal forest in northern Sweden that belowground inventories of total Hg are strongly related to soil humus C accumulation (R(2) = 0.94, p boreal forest soils have a strong sink capacity for Hg, and indicate that the sequestered Hg is bound in soil organic matter pools accumulating over millennia. Our results also suggest that more than half of the Hg stock in the sites with the longest time since fire originates from deposition predating the onset of large-scale anthropogenic emissions. This study emphasizes the importance of boreal forest humus soils for Hg storage and reveals that this pool is likely to persist over millennial time scales in the prolonged absence of fire.

  14. Resistance of the boreal forest to high burn rates.

    Science.gov (United States)

    Héon, Jessie; Arseneault, Dominique; Parisien, Marc-André

    2014-09-23

    Boreal ecosystems and their large carbon stocks are strongly shaped by extensive wildfires. Coupling climate projections with records of area burned during the last 3 decades across the North American boreal zone suggests that area burned will increase by 30-500% by the end of the 21st century, with a cascading effect on ecosystem dynamics and on the boreal carbon balance. Fire size and the frequency of large-fire years are both expected to increase. However, how fire size and time since previous fire will influence future burn rates is poorly understood, mostly because of incomplete records of past fire overlaps. Here, we reconstruct the length of overlapping fires along a 190-km-long transect during the last 200 y in one of the most fire-prone boreal regions of North America to document how fire size and time since previous fire will influence future fire recurrence. We provide direct field evidence that extreme burn rates can be sustained by a few occasional droughts triggering immense fires. However, we also show that the most fire-prone areas of the North American boreal forest are resistant to high burn rates because of overabundant young forest stands, thereby creating a fuel-mediated negative feedback on fire activity. These findings will help refine projections of fire effect on boreal ecosystems and their large carbon stocks.

  15. Hydrogen soil dynamics in northern boreal and subarctic Sweden

    Science.gov (United States)

    Steele, K. J.; Crill, P. M.; Oquist, M. G.; Varner, R. K.

    2011-12-01

    Wetland ecosystems store a large amount of organic carbon in the form of peat and are the largest natural source of CH4. Thawing of northern wetland permafrost results in an increase in the pool of soil carbon that is made available for decomposition processes and CH4 production. Some subarctic mire sites are also getting wetter as the climate warms. An increase in inundated areas in conjunction with increased amounts of organic matter could give rise to potential feedbacks to warming temperatures via increased emissions of reduced trace gases, such as CH4 and H2, to the atmosphere. H2 soil dynamics in peatlands and forests are complex because of the many microbial-mediated reactions driving H2 production and consumption. H2 couples oxidative and reductive processes in anaerobic environments. The aim of this project was to determine if high-latitude boreal and subarctic soils can change from a sink to a source of H2 to the atmosphere by identifying the microbial processes controlling the production and consumption of H2. Does H2 production and emissions to the atmosphere occur under temporary anoxia in organic -rich soils and soil horizons and do episodic weather events, particularly rain and freeze-thaw cycles, drive H2 production and release from natural soils due to the release of labile organic material and anaerobic conditions. Porewater soil gas profiles from different sub-habitats were determined in Stordalen mire in subarctic Sweden using buried ePTFE tubing and samples manually obtained using a stainless steel sipper. Trends in H2 concentration between the microporous tubing and sipper samples generally agree. The H2 concentration is higher in the tubing possibly due to preferential diffusion into the air-filled tubing by H2, which has a low solubility in water. The wettest site dominated by Eriophorum had the highest concentration of H2 with a maximum of 39.3 ppmv H2 at a depth of 30 cm. A mesic site dominated by Sphagnum had the next highest H2

  16. Light-induced diurnal pattern of methane exchange in a boreal forest

    Science.gov (United States)

    Sundqvist, Elin; Crill, Patrick; Mölder, Meelis; Vestin, Patrik; Lindroth, Anders

    2013-04-01

    Boreal forests represents one third of the Earth's forested land surface area and is a net sink of methane and an important component of the atmospheric methane budget. Methane is oxidized in well-aerated forest soils whereas ponds and bog soils are sources of methane. Besides the microbial processes in the soil also forest vegetation might contribute to methane exchange. Due to a recent finding of methane consumption by boreal plants that correlated with photosynthetic active radiation (PAR), we investigate the impact of PAR on soil methane exchange at vegetated plots on the forest floor. The study site, Norunda in central Sweden, is a 120 years old boreal forest stand, dominated by Scots pine and Norway spruce. We used continuous chamber measurements in combination with a high precision laser gas analyzer (Los Gatos Research), to measure the methane exchange at four different plots in July-November 2009, and April-June 2010. The ground vegetation consisted almost entirely of mosses and blueberry-shrubs. Two of the plots acted as stable sinks of methane whereas the other two plots shifted from sinks to sources during very wet periods. The preliminary results show a clear diurnal pattern of the methane exchange during the growing season, which cannot be explained by temperature. The highest consumption occurs at high PAR levels. The amplitude of the diurnal methane exchange during the growing season is in the order of 10 μmol m-2 h-1. This indicates that besides methane oxidation by methanotrophs in the soil there is an additional removal of methane at soil level by a process related to ground vegetation.

  17. 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.

  18. 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.

  19. Modeling Alaska boreal forests with a controlled trend surface approach

    Science.gov (United States)

    Mo Zhou; Jingjing Liang

    2012-01-01

    An approach of Controlled Trend Surface was proposed to simultaneously take into consideration large-scale spatial trends and nonspatial effects. A geospatial model of the Alaska boreal forest was developed from 446 permanent sample plots, which addressed large-scale spatial trends in recruitment, diameter growth, and mortality. The model was tested on two sets of...

  20. 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.

  1. Resilience of Alaska’s boreal forest to climatic change

    Science.gov (United States)

    Chapin, F.S.; McGuire, Anthony; Ruess, Roger W.; Hollingsworth, Teresa N.; Mack, M.C.; Johnstone, J.F.; Kasischke, E.S.; Euskirchen, E.S.; Jones, J.B.; Jorgenson, M.T.; Kielland, K.; Kofinas, G.; 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.

  2. 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.; hide

    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.

  3. Resilience of Alaska's boreal forest to climate change

    Science.gov (United States)

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

    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...

  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...

  5. 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.

  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. Contribution to climate stability via expansion of azonal boreal forests in the Ukrainian Carpathians

    Energy Technology Data Exchange (ETDEWEB)

    Nijnik, M. [Wageningen Univ. (Netherlands). Agricultural Economics and Rural Policy Group

    2002-10-01

    Since World War II, the forests in Ukraine's Carpathian region have suffered over exploitation. The upper border of the Carpathian forests crept to a lower elevation with the contraction of the azonal boreal forests of the Ukraine and the ability of the forests to perform their shelter functions and climate stabilization has decreased. For that reason, Ukraine has initiated a program for afforestation and reforestation which is aimed at planting trees in about 2 million hectares of low-productivity and waste lands and creating forest stands along rivers, canals and water bodies. It is expected that this program will increase the forest area by nearly 20 per cent, considerably improving the environmental situation in the country. Afforestation will lessen the threat of further degradation of the upper layer of fertile soil, and stabilize micro climate conditions as well as the water balance of the rivers. The forest resource base of the country will also increase. This study assessed the potential effects of the expansion of azonal boreal forests in the Carpathians on the carbon cycle and climate stability. It also addressed policy implementation costs. Initially, the study will consider a storage option, where trees are planted for a period of 50 years. Results show that afforestation and reforestation in the Carpathian mountains for the sole purpose of carbon uptake would not be very beneficial. However, the benefit would lie in soil and water protection. Future studies will focus on developing a dynamic optimization model to indicate optimal expansion of azonal boreal forests in the Carpathians. 15 refs., 2 tabs., 4 figs.

  8. High Upward Fluxes of Formic Acid from a Boreal Forest Canopy

    Science.gov (United States)

    Schobesberger, S.; Lopez-Hilfiker, F.; Taipale, D.; Millet, D. B.; D'Ambro, E.; Mammarella, I.; Zhou, P.; Wolfe, G.; Lee, B. H.; Boy, M.; Thornton, J. A.

    2016-12-01

    Formic acid, HCOOH, is one of the most abundant carboxylic acids found in the atmosphere, affecting cloud chemistry and acidity, and as a common product in the oxidative processing of volatile organic compounds (VOC), it provides constraints on the importance of various pathways and precursors. Yet, significant uncertainties in the sources and sinks of HCOOH concentrations remain. We present measurements of HCOOH mixing ratios and eddy fluxes over a boreal forest canopy in spring/summer. Boreal forests have been identified as a key region for much of the global production of HCOOH, as well as for our lack of understanding of the underlying processes. To our knowledge, these are the first direct measurements of HCOOH exchange above a boreal forest ecosystem. The measured HCOOH fluxes were bidirectional, but mostly upward during daytime, in contrast to studies made elsewhere that reported mostly downward fluxes. Episodes of downward flux were explained well by standard resistor models of dry deposition. The sum of net observed flux and modeled deposition yields an upward "gross flux" of HCOOH, which could not be quantitatively explained by literature estimates of direct vegetative/soil emissions nor by efficient chemical production from other VOC (e.g. monoterpenes). These observations suggest greatly underestimated HCOOH sources, by up to a factor of 10, of biogenic origin in the boreal forest. We implemented a vegetative HCOOH source into the GEOS-Chem chemical transport model to match our derived gross flux, and evaluated the updated model against air- and space-borne HCOOH observations. Model biases in the boundary layer were substantially reduced based on this revised treatment, suggesting that a significant fraction of the missing HCOOH source in boreal regions is located within or just above the forest canopy. Biases in the free troposphere remain unexplained.

  9. Snowpack concentrations and estimated fluxes of volatile organic compounds in a boreal forest

    Directory of Open Access Journals (Sweden)

    H. Aaltonen

    2012-06-01

    Full Text Available Soil provides an important source of volatile organic compounds (VOCs to atmosphere, but in boreal forests these fluxes and their seasonal variations have not been characterized in detail. Especially wintertime fluxes are almost completely unstudied. In this study, we measured the VOC concentrations inside the snowpack in a boreal Scots pine (Pinus sylvestris L. forest in southern Finland, using adsorbent tubes and air samplers installed permanently in the snow profile. Based on the VOC concentrations at three heights inside the snowpack, we estimated the fluxes of these gases. We measured 20 VOCs from the snowpack, monoterpenes being the most abundant group with concentrations varying from 0.11 to 16 μg m−3. Sesquiterpenes and oxygen-containing monoterpenes were also detected. Inside the pristine snowpack, the concentrations of terpenoids decreased from soil surface towards the surface of the snow, suggesting soil as the source for terpenoids. Forest damages (i.e. broken treetops and branches, fallen trees resulting from heavy snow loading during the measurement period increased the terpenoid concentrations dramatically, especially in the upper part of the snowpack. The results show that soil processes are active and efficient VOC sources also during winter, and that natural or human disturbance can increase forest floor VOC concentrations substantially. Our results stress the importance of soil as a source of VOCs during the season when other biological sources, such as plants, have lower activity.

  10. Snowpack concentrations and estimated fluxes of volatile organic compounds in a boreal forest

    Directory of Open Access Journals (Sweden)

    H. Aaltonen

    2012-01-01

    Full Text Available Soil forms an important source for volatile organic compounds (VOCs, but in boreal forests these fluxes and their seasonal variations have not been characterized in detail, especially wintertime fluxes, which are almost completely unstudied. In this study, we measured the VOC concentrations inside a snowpack in a boreal Scots pine (Pinus sylvestris L. forest in southern Finland, using adsorbent tubes and air samplers installed permanently in the snow profile. Based on the VOC concentrations at three heights inside the snowpack, we estimated the fluxes of these gases. We measured 20 VOCs from the snowpack, monoterpenes being the most abundant group with concentrations varying from 0.11 to 16 μg m−3. Sesquiterpenes and oxygen-containing monoterpenes were also detected. Inside the pristine snowpack, the concentrations of terpenoids decreased from the soil surface towards the snow surface, suggesting soil as being the source for terpenoids. Forest damages resulting from heavy snow loading during the measurement period increased the terpenoid concentrations dramatically, especially in the upper part of the snowpack. The results show that soil processes are also active and efficient VOC sources during winter and that natural or human disturbance can increase forest floor VOC concentrations substantially. Our results stress the importance of soil as a source of VOCs during the season when other biological sources, basically plants, have lower activity.

  11. 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.

  12. Global change induced biomass growth offsets carbon released via increased forest fire and respiration of the central Canadian boreal forest

    Science.gov (United States)

    Gonsamo, Alemu; Chen, Jing M.; Colombo, Stephen J.; Ter-Mikaelian, Michael T.; Chen, Jiaxin

    2017-05-01

    Northern boreal forests are sensitive to many effects of global change. This is of particular concern due to the proportionally greater climate change projected for the area in which these forests occur. One of the sensitive areas is the Far North of Ontario (FNO), consisting of one of the world's largest remaining tracts of unmanaged boreal forest, the world's third largest area of wetland, and the most southerly area of tundra. We studied past, present, and potential future carbon (C) balance of FNO forests using the Integrated Terrestrial Ecosystem Carbon Model and the Canadian Regional Climate Model with stand-replacing fire disturbance. The forced simulations of past (1901-2004) C balances indicated that vegetation C stock remained stable, while soil C stock gradually declined (-0.07 t C ha-1 yr-1, p forest age class structure resulting in an increase in total FNO ecosystem C stock by mid-21st century. However, the projected simulations also indicated that the relative sizes of forest C stocks will change, with relatively less in the soil and more in vegetation, increasing fuel loads and making the entire ecosystem susceptible to forest fire and insect disturbances.

  13. Boreal forests and atmosphere - Biosphere exchange of carbon dioxide

    Science.gov (United States)

    D'Arrigo, Rosanne; Jacoby, Gordon C.; Fung, Inez Y.

    1987-01-01

    Two approaches to investigating the role of boreal forests in the global carbon cycle are presented. First, a tracer support model which incorporates the normalized-difference vegetation index obtained from advanced, very high resolution radiometer radiances was used to simulate the annual cycle of CO2 in the atmosphere. Results indicate that the seasonal growth of the combined boreal forests of North America and Eurasia accounts for about 50 percent of the mean seasonal CO2 amplitude recorded at Pt. Barrow, Alaska and about 30 percent of the more globally representative CO2 signal at Mauna Loa, Hawaii. Second, tree-ring width data from four boreal treeline sites in northern Canada were positively correlated with Pt. Barrow CO2 drawdown for the period 1971-1982. These results suggest that large-scale changes in the growth of boreal forests may be contributing to the observed increasing trend in CO2 amplitude. They further suggest that tree-ring data may be applicable as indices for CO2 uptake and remote sensing estimates of photosynthetic activity.

  14. 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.

  15. Drought as a driver of declining boreal forest growth: Integrating forest inventory measurements with models to gain insight into underlying mechanisms

    Science.gov (United States)

    Trugman, A. T.; Medvigy, D.; Anderegg, W.; Caspersen, J.; Zeng, H.; Pacala, S. W.

    2016-12-01

    Boreal forests contain over 30% of Earth's terrestrial carbon and are an important component of the land carbon sink. However, the future ability of the boreal forest to maintain a net carbon sink is uncertain and depends on potentially compensating interactions of CO2 fertilization, warmer temperatures, and hotter drought conditions. Observational studies have attributed drought as a major driver of recent declines in growth and increases in mortality in many parts of the North American boreal forest. Yet, most vegetation models have a simplistic representation of vegetation water stress and fail to capture drought-associated growth and mortality trends, impacting our ability to accurately forecast the effects of climate change on the boreal forest. Here, we show additional evidence for widespread declines in boreal tree growth and increasing insect-related mortality in aspen trees based on a mixed model analysis of the Cooperative Alaska Forest Inventory. Our findings indicate that the growth decline is controlled by high midsummer potential evapotranspiration that overpowers any CO2 fertilization signal. We also observe a possible shift in the distribution of angiosperm and gymnosperm, a biological transition that could impact long-term local carbon dynamics. Using insight gained from our mixed model analysis, we perform a regional-scale model evaluation using the boreal forest version of Ecosystem Demography model 2 that includes a dynamic soil organic layer, 7 boreal-specific plant functional types, and a fully mechanistic plant hydraulic scheme. We then use both the Alaskan and Canadian Forest Inventories to constrain our hypotheses and assess whether drought related growth declines can be better attributed to tree drought response from (1) carbon starvation, (2) permanent damage of hydraulic machinery, or (3) delayed recovery of hydraulic machinery. Under each of these scenarios we forecast how drought potentially impacts decadal-scale boreal carbon dynamics.

  16. Decomposition of recalcitrant carbon under experimental warming in boreal forest.

    Science.gov (United States)

    Romero-Olivares, Adriana L; Allison, Steven D; Treseder, Kathleen K

    2017-01-01

    Over the long term, soil carbon (C) storage is partly determined by decomposition rate of carbon that is slow to decompose (i.e., recalcitrant C). According to thermodynamic theory, decomposition rates of recalcitrant C might differ from those of non-recalcitrant C in their sensitivities to global warming. We decomposed leaf litter in a warming experiment in Alaskan boreal forest, and measured mass loss of recalcitrant C (lignin) vs. non-recalcitrant C (cellulose, hemicellulose, and sugars) throughout 16 months. We found that these C fractions responded differently to warming. Specifically, after one year of decomposition, the ratio of recalcitrant C to non-recalcitrant C remaining in litter declined in the warmed plots compared to control. Consistent with this pattern, potential activities of enzymes targeting recalcitrant C increased with warming, relative to those targeting non-recalcitrant C. Even so, mass loss of individual C fractions showed that non-recalcitrant C is preferentially decomposed under control conditions whereas recalcitrant C losses remain unchanged between control and warmed plots. Moreover, overall mass loss was greater under control conditions. Our results imply that direct warming effects, as well as indirect warming effects (e.g. drying), may serve to maintain decomposition rates of recalcitrant C compared to non-recalcitrant C despite negative effects on overall decomposition.

  17. 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

  18. 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.

  19. First Polarimetric GNSS-R Measurements from a Stratospheric Flight over Boreal Forests

    Directory of Open Access Journals (Sweden)

    Hugo Carreno-Luengo

    2015-10-01

    Full Text Available The first-ever dual-frequency multi-constellation Global Navigation Satellite Systems Reflectometry (GNSS-R polarimetric measurements over boreal forests and lakes from the stratosphere are presented. Data were collected during the European Space Agency (ESA sponsored Balloon Experiments for University Students (BEXUS 19 stratospheric balloon experiment using the P(Y and C/A Reflect Ometer (PYCARO instrument operated in closed-loop mode. Maps of the polarimetric ratio for L1 and L2 Global Positioning System (GPS and GLObal Navigation Satellite System (GLONASS, and for E1 Galileo signals are derived from the float phase at 27,000 m height, and the specular points are geolocalized on the Earth’s surface. Polarimetric ratio ( maps over boreal forests are shown to be in the range 2–16 dB for the different GNSS codes. This result suggests that the scattering is taking place not only over the soil, but over the different forests elements as well. Additionally to the interpretation of the experimental results a theoretical investigation of the different contributions to the total reflectivity over boreal forests is performed using a bistatic scattering model. The simulated cross- (reflected Left Hand Circular Polarization LHCP and co-polar (reflected Right Hand Circular Polarization RHCP reflectivities are evaluated for the soil, the canopy, and the canopy–soil interactions for three different biomass densities: 725 trees/ha, 150 trees/ha and 72 trees/ha. For elevation angles larger than the Brewster angle, it is found that the cross-polar signal is dominant when just single reflections over the forests are evaluated, while in the case of multiple reflections the co-polar signal becomes the largest one. The first-ever dual-frequency multi-constellation Global Navigation Satellite Systems Reflectometry (GNSS-R polarimetric measurements over boreal forests and lakes from the stratosphere are presented. Data were collected during the European Space

  20. Studies of microwave scattering and canopy architecture for boreal forests

    Science.gov (United States)

    Lockhart, G. Lance; Gogineni, S. P.

    1995-01-01

    This is an annual report on the project titled 'Study of Microwave Scattering and Canopy Architecture for Boreal Forests.' The objectives of our work are to study the interaction of microwave signals with vegetation components and to determine the radar's ability to provide accurate estimates of biophysical parameters such as biomass. Our research is aimed at refining the current microwave models and using these improvements to facilitate more accurate interpretations of SAR (synthetic aperture radar) imagery.

  1. 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.

  2. Carbon dioxide, methane and nitrous oxide fluxes from a fire chronosequence in subarctic boreal forests of Canada.

    Science.gov (United States)

    Köster, Egle; Köster, Kajar; Berninger, Frank; Aaltonen, Heidi; Zhou, Xuan; Pumpanen, Jukka

    2017-12-01

    Forest fires are one of the most important natural disturbances in boreal forests, and their occurrence and severity are expected to increase as a result of climate warming. A combination of factors induced by fire leads to a thawing of the near-surface permafrost layer in subarctic boreal forest. Earlier studies reported that an increase in the active layer thickness results in higher carbon dioxide (CO2) and methane (CH4) emissions. We studied changes in CO2, CH4 and nitrous oxide (N2O) fluxes in this study, and the significance of several environmental factors that influence the greenhouse gas (GHG) fluxes at three forest sites that last had fires in 2012, 1990 and 1969, and we compared these to a control area that had no fire for at least 100years. The soils in our study acted as sources of CO2 and N2O and sinks for CH4. The elapsed time since the last forest fire was the only factor that significantly influenced all studied GHG fluxes. Soil temperature affected the uptake of CH4, and the N2O fluxes were significantly influenced by nitrogen and carbon content of the soil, and by the active layer depth. Results of our study confirm that the impacts of a forest fire on GHGs last for a rather long period of time in boreal forests, and are influenced by the fire induced changes in the ecosystem. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. 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

  4. Tree retention in boreal pine forest

    OpenAIRE

    Santaniello, Francesca

    2017-01-01

    Tree retention forestry aims at increasing structural diversity in managed forests. In this study, I have investigated the influence of tree retention forestry on delivery of two ecosystem services (wood production and carbon sequestration) and dead wood (as a proxy for biodiversity). Furthermore, habitat requirements of lichens dependent on dead wood were investigated. The study was conducted in 15 Scots pine forest stands with five various tree retention levels, in which four...

  5. Nitrogen Additions Increase the Diversity of Carbon Compounds Degraded by Fungi in Boreal Forests

    Science.gov (United States)

    Gartner, T. B.; Turner, K. M.; Treseder, K. K.

    2004-12-01

    Boreal forest soils in North America harbor a large reservoir of organic C, and this region is increasingly exposed to long-range atmospheric N transport from Eurasia. By examining the responses of decomposers to N deposition in these forests, we hope to improve predictions of the fate of boreal carbon pools under global change. We tested the hypothesis that the functional diversity of decomposer fungi would increase under N fertilization in boreal forests where fungal growth was otherwise N-limited, owing to a reduction in competitive exclusion of fungal groups. We collected soil and leaf litter from three Alaskan sites that represent different successional stages at 5, 17, or 80 years following severe forest fire. Each site had been exposed for two years to nitrogen and phosphorus fertilization in a factorial design, with four plots per treatment. Nutrient limitation of fungal growth varied depending on successional stage. The standing hyphal length of decomposer fungi in soil (i.e. Ascomycota and Basidiomycota) responded to neither N nor P in the 5-year old site, increased under N fertilization in the 17-year old site, and increased where N and P was added simultaneously in the 80-year old site (site x N x P interaction: P = 0.001). We used BIOLOG microplates for filamentous fungi to obtain an index of the diversity of carbon use by decomposer fungi; each of 95 wells of these plates contains a different carbon-based compound, as well as a dye that changes color upon metabolism of the compound. Saline leaf litter extracts were mixed with fungal growth medium and then added to the microplates. The number of wells displaying metabolic activity was counted following incubation for five days. We found that N fertilization raised the average number of positive wells per plate from 14 to 27 (P = 0.012), with no significant differences in responses among sites. Phosphorus additions did not alter functional diversity of fungi in any site. Since increases in functional

  6. 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

  7. Assessing vulnerability to climate-induced changes in ecosystem services of boreal croplands and forests

    Science.gov (United States)

    Rankinen, Katri; Akujärvi, Anu; Holmberg, Maria

    2017-04-01

    Croplands and forests of the boreal region supply a wide range of ecosystem services. The properties and processes of these ecosystems regulate water flow and climate, and retain nutrients and store carbon. The functioning of the ecosystem processes depends on ambient temperatures and precipitation patterns, which are likely to continue changing in the boreal zone. MONIMET (LIFE12 ENV/FI/000409, 9/2013 - 9/2017) is an EU Life funded project about Climate Change Indicators and Vulnerability of Boreal Zone Applying Innovative Observation and Modeling Techniques. In this project, we calculated future changes of carbon storage in soil, and nutrient loading from soil to surface waters and drinking water supplies. We calculated the carbon storage of forests and croplands using the dynamic YASSO litter and soil carbon model. The simulated carbon budget estimates were upscaled to the river basin by combining them with gridded data of land cover. We simulated nutrient loading from two boreal catchments to the receiving waters using the dynamic, catchment scale model INCA. We calculated land use specific loading values for these two well monitored catchments that belong to the LTER (The Long Term Ecological Research) monitoring network, and upscaled these results to the larger river basin based on grid-scaled data of land cover. We used population projections as proxies for the societal demand for the services of climate regulation and water purification, and assessed thereby the vulnerability of society to climate-induced changes in these services. In this poster we present the technical frame of combining models and data.

  8. Assessing various drought indicators in representing summer drought in boreal forests in Finland

    Science.gov (United States)

    Gao, Y.; Markkanen, T.; Thum, T.; Aurela, M.; Lohila, A.; Mammarella, I.; Kämäräinen, M.; Hagemann, S.; Aalto, T.

    2016-01-01

    Droughts can have an impact on forest functioning and production, and even lead to tree mortality. However, drought is an elusive phenomenon that is difficult to quantify and define universally. In this study, we assessed the performance of a set of indicators that have been used to describe drought conditions in the summer months (June, July, August) over a 30-year period (1981-2010) in Finland. Those indicators include the Standardized Precipitation Index (SPI), the Standardized Precipitation-Evapotranspiration Index (SPEI), the Soil Moisture Index (SMI), and the Soil Moisture Anomaly (SMA). Herein, regional soil moisture was produced by the land surface model JSBACH of the Max Planck Institute for Meteorology Earth System Model (MPI-ESM). Results show that the buffering effect of soil moisture and the associated soil moisture memory can impact on the onset and duration of drought as indicated by the SMI and SMA, while the SPI and SPEI are directly controlled by meteorological conditions. In particular, we investigated whether the SMI, SMA and SPEI are able to indicate the Extreme Drought affecting Forest health (EDF), which we defined according to the extreme drought that caused severe forest damages in Finland in 2006. The EDF thresholds for the aforementioned indicators are suggested, based on the reported statistics of forest damages in Finland in 2006. SMI was found to be the best indicator in capturing the spatial extent of forest damage induced by the extreme drought in 2006. In addition, through the application of the EDF thresholds over the summer months of the 30-year study period, the SPEI and SMA tended to show more frequent EDF events and a higher fraction of influenced area than SMI. This is because the SPEI and SMA are standardized indicators that show the degree of anomalies from statistical means over the aggregation period of climate conditions and soil moisture, respectively. However, in boreal forests in Finland, the high initial soil moisture

  9. Carbon sequestration is related to mycorrhizal fungal community shifts during long-term succession in boreal forests.

    Science.gov (United States)

    Clemmensen, Karina E; Finlay, Roger D; Dahlberg, Anders; Stenlid, Jan; Wardle, David A; Lindahl, Björn D

    2015-03-01

    Boreal forest soils store a major proportion of the global terrestrial carbon (C) and below-ground inputs contribute as much as above-ground plant litter to the total C stored in the soil. A better understanding of the dynamics and drivers of root-associated fungal communities is essential to predict long-term soil C storage and climate feedbacks in northern ecosystems. We used 454-pyrosequencing to identify fungal communities across fine-scaled soil profiles in a 5000 yr fire-driven boreal forest chronosequence, with the aim of pinpointing shifts in fungal community composition that may underlie variation in below-ground C sequestration. In early successional-stage forests, higher abundance of cord-forming ectomycorrhizal fungi (such as Cortinarius and Suillus species) was linked to rapid turnover of mycelial biomass and necromass, efficient nitrogen (N) mobilization and low C sequestration. In late successional-stage forests, cord formers declined, while ericoid mycorrhizal ascomycetes continued to dominate, potentially facilitating long-term humus build-up through production of melanized hyphae that resist decomposition. Our results suggest that cord-forming ectomycorrhizal fungi and ericoid mycorrhizal fungi play opposing roles in below-ground C storage. We postulate that, by affecting turnover and decomposition of fungal tissues, mycorrhizal fungal identity and growth form are critical determinants of C and N sequestration in boreal forests. © 2014 The Authors New Phytologist © 2014 New Phytologist Trust.

  10. Scale-dependent variation in forest structures in naturally dynamic boreal forest landscapes

    Science.gov (United States)

    Kulha, Niko; Pasanen, Leena; De Grandpré, Louis; Kuuluvainen, Timo; Aakala, Tuomas

    2017-04-01

    Natural forest structures vary at multiple spatial scales. This variation reflects the occurrence of driving factors, such as disturbances and variation in soil or topography. To explore and understand the linkages of forest structural characteristics and factors driving their variation, we need to recognize how the structural characteristics vary in relation to spatial scale. This can be achieved by identifying scale-dependent features in forest structure within unmanaged forest landscapes. By identifying these features and examining their relationship with potential driving factors, we can better understand the dynamics of forest structural development. Here, we examine the spatial variation in forest structures at multiple spatial scales, utilizing data from old-growth boreal forests in two regions with contrasting disturbance regimes: northern Finland and north-eastern Québec, Canada ( 67° 45'N, 29° 36'E, 49° 39'N, 67° 55'W, respectively). The three landscapes (4 km2 each) in Finland are dominated by Pinus sylvestris and Picea abies, whereas the two landscapes in Québec are dominated by Abies balsamea and Picea mariana. Québec's forests are a subject to cyclic outbreaks of the eastern spruce budworm, causing extensive mortality especially in A. balsamea-dominated stands. In the Finnish landscapes, gap- to patch-scale disturbances due to tree senescence, fungi and wind, as well as infrequent surface fires in areas dominated by P. sylvestris, prevail. Owing to the differences in the species compositions and the disturbance regimes, we expect differing scales of variation between the landscapes. To quantify patterns of variation, we visually interpret stereopairs of recent aerial photographs. From the photographs, we collect information on forest canopy coverage, species composition and dead wood. For the interpretation, each 4 km2 plot is divided into 0.1ha square cells (4096 per plot). Interpretations are validated against field observations and compiled

  11. Patterns of Canopy and Surface Layer Consumption in a Boreal Forest Fire from Repeat Airborne Lidar

    Science.gov (United States)

    Alonzo, Michael; Morton, Douglas C.; Cook, Bruce D.; Andersen, Hans-Erik; Babcock, Chad; Pattison, Robert

    2017-01-01

    Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaskas Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broad leaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from above ground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn severity

  12. 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.

  13. 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.

  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, 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.

  15. Nitrous oxide fluxes from forest floor, tree stems and canopies of boreal tree species during spring

    Science.gov (United States)

    Haikarainen, Iikka; Halmeenmäki, Elisa; Machacova, Katerina; Pihlatie, Mari

    2017-04-01

    Boreal forests are considered as small sources of atmospheric nitrous oxide (N2O) due to microbial N2O production in the soils. Recent evidence shows that trees may play an important role in N2O exchange of forest ecosystems by offering pathways for soil produced N2O to the atmosphere. To confirm magnitude, variability and the origin of the tree mediated N2O emissions more research is needed, especially in boreal forests which have been in a minority in such investigation. We measured forest floor, tree stem and shoot N2O exchange of three boreal tree species at the beginning of the growing season (13.4.-13.6.2015) at SMEAR II station in Hyytiälä, located in Southern Finland (61˚ 51´N, 24˚ 17´E, 181 a.s.l.). The fluxes were measured in silver birch (Betula pendula), downy birch (B. pubescens) and Norway spruce (Picea abies) on two sites with differing soil type and characteristics (paludified and mineral soil), vegetation cover and forest structure. The aim was to study the vertical profile of N2O fluxes at stem level and to observe temporal changes in N2O fluxes over the beginning of the growing season. The N2O exchange was determined using the static chamber technique and gas chromatographic analyses. Scaffold towers were used for measurements at multiple stem heights and at the canopy level. Overall, the N2O fluxes from the forest floor and trees at both sites were very small and close to the detection limit. The measured trees mainly emitted N2O from their stems and shoots, while the forest floor acted as a sink of N2O at the paludified site and as a small source of N2O at the mineral soil site. Stem emissions from all the trees at both sites were on average below 0.5 μg N2O m-2 of stem area h-1, and the shoot emissions varied between 0.2 and 0.5 ng N2O m-2 g-1 dry biomass. When the N2O fluxes were scaled up to the whole forest ecosystem, based on the tree biomass and stand density, the N2O emissions from birch and spruce trees at the paludified site

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

    Science.gov (United States)

    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

  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. Fire Regime along Latitudinal Gradients of Continuous to Discontinuous Coniferous Boreal Forests in Eastern Canada

    National Research Council Canada - National Science Library

    Portier, Jeanne; Gauthier, Sylvie; Leduc, Alain; Arseneault, Dominique; Bergeron, Yves

    2016-01-01

      Fire is the main disturbance in North American coniferous boreal forests. In Northern Quebec, Canada, where forest management is not allowed, the landscape is gradually constituted of more opened lichen woodlands...

  19. 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

  20. 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

  1. Estimating energy balance fluxes above a boreal forest from radiometric temperature observations

    Science.gov (United States)

    The great areal extent of boreal forests confers these ecosystems potential to impact on the global surface-atmosphere energy exchange. A modeling approach, based on a simplified two-source energy balance model, was proposed to estimate energy balance fluxes above boreal forests using thermal infrar...

  2. Modeling Climate-Biosphere Interactions in the Boreal Forest

    Science.gov (United States)

    Frolking, Steve

    1998-01-01

    The overall goal of this BOREAS Program was to develop, test, and apply a model of the carbon balance of boreal forest sites with a significant groundcover component (moss or lichen). The basic question addressed with this model was: What is the sensitivity of the boreal forest carbon balance to weather variability? More specifically: What are the differences in the sensitivities of carbon gains (photosynthesis) and carbon losses (respiration) of the various components of the ecosystem? Are there different seasonalities to their sensitivities (e.g., warmer springs will have one effect, warmer summers a different effect)? What are the effects of different patterns of successive weather years (wet/dry, warm/cool)? What, for example, would be the difference in effects of two "warmer than normal" months-one with each day warmer than normal, and the other with three normal weeks and one very hot week? Due to weather variability, how "noisy" will any carbon flux or carbon pool signal be that we might use to try to detect change? The project resulted in the development of a new boreal forest ecosystem model. This model was the first model in the BOREAS project to look closely at the role of mosses in the ecosystem carbon balance, and also was the first model in the BOREAS project to look closely at interannual variability in carbon fluxes. Along with the work of many other groups, TE-19 modeling analysis pointed to the need for a second, longer field season in 1996, with particular focus on the spring and fall transitions and on ground vegetation. BOREAS groups TE-19 (Frolking), TGB-1 (Crill) & TGB-3 (Moore & Roulet) analyzed BOREAS data and other published and unpublished data to develop a relationship between peatland ecosystem productivity and incoming radiation, which is quite distinct from the upland ecosystem relationships observed in other studies.

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

    Science.gov (United States)

    Yuan, F.M.; Yi, S.H.; McGuire, A.D.; Johnson, K.D.; Liang, J.; Harden, J.W.; Kasischke, E.S.; Kurz, W.A.

    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

  4. 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

  5. Black (pyrogenic carbon in boreal forests: a synthesis of current knowledge and uncertainties

    Directory of Open Access Journals (Sweden)

    C. M. Preston

    2006-02-01

    Full Text Available The carbon (C cycle in boreal regions is strongly influenced by fire, which converts biomass and detrital C mainly to gaseous forms (CO2 and smaller proportions of CO and CH4, and some 1–7% of mass to pyrogenic C (PyC. PyC is mainly produced as solid charred residues, including visually-defined charcoal, and a black carbon (BC fraction chemically defined by its resistance to laboratory oxidation, plus much lower proportions of volatile soot and polycyclic aromatic hydrocarbons (PAHs. All PyC is characterized by fused aromatic rings, but varying in cluster sizes, and presence of other elements (N, O and functional groups. There are several reasons for current interest in defining more precisely the role of PyC in the C cycle of boreal regions. First, PyC is resistant to decomposition, and therefore contributes to very stable C pools in soils and sediments. Second, it influences soil processes, mainly through its sorption properties and cation exchange capacity, and third, soot aerosols absorb solar radiation and may contribute to global warming. However, there are large gaps in the basic information needed to address these topics. While charcoal is commonly defined by visual criteria, analytical methods for BC are mainly based on various measures of oxidation resistance, or on yield of benzenepolycarboxylic acids. These methods are still being developed, and capture different fractions of the PyC "continuum". There are few quantitative reports of PyC production and stocks in boreal forests (essentially none for boreal peatlands, and results are difficult to compare due to varying experimental goals and methods, as well as inconsistent terminology. There are almost no direct field measurements of BC aerosol production from boreal wildfires, and little direct information on rates and mechanisms for PyC loss. Structural characterization of charred biomass and forest floor from wildfires generally indicates a low level of

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Mechanisms influencing changes in lake area in Alaskan boreal forest

    Science.gov (United States)

    Roach, Jennifer K.; Griffith, Brad; Verbyla, David; Jones, Jeremy B.

    2011-01-01

    During the past ∼50 years, the number and area of lakes have declined in several regions in boreal forests. However, there has been substantial finer-scale heterogeneity; some lakes decreased in area, some showed no trend, and others increased. The objective of this study was to identify the primary mechanisms underlying heterogeneous trends in closed-basin lake area. Eight lake characteristics (δ18O, electrical conductivity, surface : volume index, bank slope, floating mat width, peat depth, thaw depth at shoreline, and thaw depth at the forest boundary) were compared for 15 lake pairs in Alaskan boreal forest where one lake had decreased in area since ∼1950, and the other had not. Mean differences in characteristics between paired lakes were used to identify the most likely of nine mechanistic scenarios that combined three potential mechanisms for decreasing lake area (talik drainage, surface water evaporation, and terrestrialization) with three potential mechanisms for nondecreasing lake area (subpermafrost groundwater recharge through an open talik, stable permafrost, and thermokarst). A priori expectations of the direction of mean differences between decreasing and nondecreasing paired lakes were generated for each scenario. Decreasing lakes had significantly greater electrical conductivity, greater surface : volume indices, shallower bank slopes, wider floating mats, greater peat depths, and shallower thaw depths at the forest boundary. These results indicated that the most likely scenario was terrestrialization as the mechanism for lake area reduction combined with thermokarst as the mechanism for nondecreasing lake area. Terrestrialization and thermokarst may have been enhanced by recent warming which has both accelerated permafrost thawing and lengthened the growing season, thereby increasing plant growth, floating mat encroachment, transpiration rates, and the accumulation of organic matter in lake basins. The transition to peatlands associated

  12. Validation of the Integrated Biosphere Simulator over Canadian deciduous and coniferous boreal forest stands

    Science.gov (United States)

    El Maayar, Mustapha; Price, David T.; Delire, Christine; Foley, Jonathan A.; Black, T. Andrew; Bessemoulin, Pierre

    2001-07-01

    Data collected during the Boreal Ecosystem-Atmosphere Study (BOREAS) at four different forest stands were used to test surface energy and carbon fluxes simulated by the Integrated Biosphere Simulator (IBIS). These stands included deciduous and conifer species and were located in both the BOREAS northern and southern study areas. Two runs were made: one using the original IBIS model and the other using a version modified to consider an organic soil layer (OSL) covering the mineral soil surface. Results show that the inclusion of the OSL substantially improved the simulation of soil heat flux, as well as of temperature and moisture in the topmost soil layer. Simulations show that latent and sensible heat fluxes, and net ecosystem exchange of carbon, were not affected appreciably by the presence of a thin (10 cm or less) OSL covering the forest floor. With a thick (50 cm) OSL, however, simulation of latent heat flux and net ecosystem exchange of carbon was substantially improved. Consideration of the OSL in the model also led to better simulation of the onsets of soil thawing. Correct estimation of heat diffusion to deep soil through thick organic layers requires a parameterization that accounts for the state of the organic material decomposition. Simulations presented here also show the necessity for using detailed information on soil physical properties for better evaluation of model performance.

  13. 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.

  14. Controls on and consequences of specific leaf area variation with permafrost depth in a boreal forest

    Science.gov (United States)

    Anderson, C.; Bond-Lamberty, B. P.; Huang, M.; Xu, Y.; Stegen, J.

    2016-12-01

    Specific leaf area (SLA, leaf area per unit dry mass) is an index of plant carbon captured by photosynthesis and an important input into many terrestrial process models. However, the controls on and consequences of SLA variation are poorly understood, especially in high latitude, climatically-sensitive permafrost regions. To address this, we measured SLA along with soil and topographic properties across a boreal forest permafrost transition, in which forest composition changed as permafrost deepened from 54 to >150 cm. Using replicated transects, we characterized both linear and threshold relationships between topographic and edaphic variables and SLA, and evaluated and expanded upon a conceptual model of environmental factors and vegetation patterns. We found that the depth of the soil active layer above permafrost (ALD) was highly correlated with SLA, for both coniferous and deciduous boreal tree species. Across a permafrost transition, intraspecific SLA variation was associated with a fivefold increase in NPP, suggesting that changes in ALD due to permafrost thaw could heavily influence ecosystem carbon accumulation. High levels of intraspecific trait variation suggest the need for flexible trait representation across plant functional types in Earth System Models. We thus incorporated our empirical environment-SLA relationships into spatially explicit spin-ups of the Community Land Model (CLM v4.5) in an effort to constrain model uncertainty. Dynamic representation of plant traits can improve our representation of intraspecific trait variability and its functional relationship with environmental gradients in models predicting ecosystem responses to ongoing climate change.

  15. 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 ...

  16. Effects of Sloped Terrain and Forest Stand Maturity on Evapotranspiration in a Boreal Forested Catchment

    Science.gov (United States)

    Isabelle, P. E.; Nadeau, D.; Parent, A. C.; Rousseau, A. N.; Jutras, S.; Anctil, F.

    2015-12-01

    The boreal forests are the predominant landscape of Canada, occupying 49% of its boreal zone or 27% of the country. Despite the tremendous amount of literature on such ecosystems, some gaps persist in our understanding of boreal forest evapotranspiration (ET), given that direct measurements are costly to obtain and therefore scarce in these remote territories. This is especially the case on sloped terrain, since the eddy covariance method is not traditionally used in such situations. These gaps lead to the implementation of the EVAP experimental project, which intends to produce a major leap in our understanding of the water and energy budgets of a sloped boreal forest. Starting in summer 2015, we heavily instrumented a watershed in the Montmorency Forest (47°17' N; 71°10' W), Quebec, Canada. Located in the Laurentian Mountains, the forest has a mean elevation of 750 m with peaks at 1000 m. The setup includes a 20-m flux tower with two separate sets of eddy correlation and net radiation measurements facing opposite directions, located over an almost mature boreal forest (logged ~20 years ago, 8-10 m trees). Eddy fluxes are also measured under the canopy with a similar setup, while a sub-watershed is instrumented with a 10-m flux tower using homologous instruments, this time on a much younger forest stand (logged ~10 years ago, 4-5 m trees). Both sites are characterized by a significant slope (~20%), facing northeast for the 20-m tower and west for the 10-m tower. With several other instruments, we are measuring every major components of both water and energy budgets, including the outgoing discharge of the watershed and subwatershed. The different slope orientations and local topography of both sites allow us to quantify the relationships between solar exposition, topographic shading and ET rates; these relationships being transposable to other mountainous forested catchments. We also investigate the presence of slope flows and assess their impact on local ET

  17. 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.

  18. Issues and potential in creating carbon sinks in the boreal forest; Potentiel et enjeux a propos de la creation de puits de carbone en foret boreale

    Energy Technology Data Exchange (ETDEWEB)

    Boucher, J.F.; Gagnon, R.; Villeneuve, C. [Quebec Univ., Chicoutimi, PQ (Canada); Gaboury, S. [Rio Tinto Alcan, Montreal, PQ (Canada); Lord, D. [Quebec Univ., Chicoutimi, PQ (Canada). Dept. des Sciences Fondamentales

    2008-09-15

    Although greenhouse gas (GHG) emissions are primarily associated with the combustion of fossil fuels, they are also linked to deforestation. This article discussed the contribution of the forestry sector in mitigating climate change in the province of Quebec, which has vast areas of barren deforested land. Recent studies have shown that boreal forests have significant potential for carbon sequestration, although much uncertainty remains regarding the ability to store carbon for the long-term due to the potential for fires. Concerns regarding climate change may provide opportunities to develop important synergies between the wood products industry and bioenergy developers. This article presented a typical case of afforestation of barren boreal lands and noted the benefits of reforestation in terms of creating new habitats for species. This article also included a chart indicating the carbon sequestration potential for different types of biomass, notably tree canopies, roots, forest litter, deadwood and soil. A map showing the spatial distribution of bare boreal regions in Quebec was also included along with the total cost per hectare of carbon sequestration per tonne of carbon dioxide. It was concluded that important reforestation projects can be undertaken in the context of mitigating climate change to restore the role of carbon sinks which were lost in the unproductive barren regions. 45 refs., 2 tabs., 3 figs.

  19. 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...

  20. Stocks, Chemistry, and Sensitivity to Climate Change of Dead Organic Matter Along the Canadian Boreal Forest Transect Case Study

    Energy Technology Data Exchange (ETDEWEB)

    Preston, C.M.; Norris, C. [Pacific Forestry Centre, Natural Resources Canada, Victoria, BC, V8Z 1M5 (Canada); Bhatti, J.S. [Northern Forestry Centre, Natural Resources Canada, Edmonton, AB, T6H 3S5 (Canada); Flanagan, L.B. [Department of Biological Sciences, University of Lethbridge, Lethbridge, AB, T1K 3M4 (Canada)

    2006-01-15

    Improving our ability to predict the impact of climate change on the carbon (C) balance of boreal forests requires increased understanding of site-specific factors controlling detrital and soil C accumulation. Jack pine (Pinus banksiana) and black spruce (Picea mariana) stands along the Boreal Forest Transect Case Study (BFTCS) in northern Canada have similar C stocks in aboveground vegetation and large woody detritus, but thick forest floors of poorly-drained black spruce stands have much higher C stocks, comparable to living biomass. Their properties indicate hindered decomposition and N cycling, with high C/N ratios, strongly stratified and depleted d13C and d15N values, high concentrations of tannins and phenolics, and 13C nuclear magnetic resonance (NMR) spectra typical of poorly decomposed plant material, especially roots and mosses. The thinner jack pine forest floor appears to be dominated by lichen, with char in some samples. Differences in quantity and quality of aboveground foliar and woody litter inputs are small and unlikely to account for the contrasts in forest floor accumulation and properties. These are more likely associated with site conditions, especially soil texture and drainage, exacerbated by increases in sphagnum coverage, forest floor depth, and tannins. Small changes in environmental conditions, especially reduced moisture, could trigger large C losses through rapid decomposition of forest floor in poorly drained black spruce stands in this region.

  1. 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.

  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

    -induced drought stress (Barber et al 2000). Notably, this response may be more complicated than simply a decline in soil moisture. Even when soil moisture is plentiful, warming can negatively impact plant growth and survival by causing increased respiratory consumption of stored carbohydrates (McDowell 2011) and decreased stomatal conductance due to hydraulic limitation (Flexas et al 2004). Some degree of acclimation may be occurring, as white spruce populations that experience moderate temperatures and precipitation have lower optimal growth temperatures than populations at warmer, drier sites do (figure 1(c)). Yet, populations at the warmest or driest sites show strong growth declines during warm periods, consistent with a decline in the viability of these populations in some regions (Goetz et al 2005, Beck and Goetz 2011, Beck et al 2011). Can interior boreal forests acclimate to the current era's rapid warming? Or will temperatures within interior boreal forests outpace or extend beyond the adaptive capabilities of boreal tree species? The answer remains a mystery, partly because important aspects of acclimation are still poorly understood, and partly because of other important processes such as wildfire and increases in CO2 concentration, nitrogen deposition, growing-season length, and tropospheric ozone concentration. Figure 1 Figure 1. Relationships between white spruce tree-ring widths and climate at 59 sites in Alaska. (a) Annual correlation between ring-width index and June-July average temperature during years when June--July temperature was colder (blue bars) and warmer (red bars) than average. Pairs of bars represent the coldest 20 sites (left), 19 sites with intermediate temperature (middle) and the warmest 20 sites (right). (b) Spline curves that represent the best-fit relationship between temperature (x-axis) and ring-width index variability (y-axis) at cold sites (blue line), intermediate sites (black line) and warm sites (orange line). (c) Same as (b) but for

  3. Uncovering the Minor Contribution of Land-Cover Change in Upland Forests to the Net Carbon Footprint of a Boreal Hydroelectric Reservoir.

    Science.gov (United States)

    Dessureault, Pierre-Luc; Boucher, Jean-François; Tremblay, Pascal; Bouchard, Sylvie; Villeneuve, Claude

    2015-07-01

    Hydropower in boreal conditions is generally considered the energy source emitting the least greenhouse gas per kilowatt-hour during its life cycle. The purpose of this study was to assess the relative contribution of the land-use change on the modification of the carbon sinks and sources following the flooding of upland forested territories to create the Eastmain-1 hydroelectric reservoir in Quebec's boreal forest using Carbon Budget Model of the Canadian Forest Sector. Results suggest a carbon sink loss after 100 yr of 300,000 ± 100,000 Mg CO equivalents (COe). A wildfire sensitivity analysis revealed that the ecosystem would have acted as a carbon sink as long as forests to the total net carbon footprint of a hydroelectric reservoir in the boreal zone can be. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  4. Preliminary Assessment of JERS-1 SAR to Discriminating Boreal Landscape Features for the Boreal Forest Mapping Project

    Science.gov (United States)

    McDonald, Kyle; Williams, Cynthia; Podest, Erika; Chapman, Bruce

    1999-01-01

    This paper presents an overview of the JERS-1 North American Boreal Forest Mapping Project and a preliminary assessment of JERS-1 SAR imagery for application to discriminating features applicable to boreal landscape processes. The present focus of the JERS-1 North American Boreal Forest Mapping Project is the production of continental scale wintertime and summertime SAR mosaics of the North American boreal forest for distribution to the science community. As part of this effort, JERS-1 imagery has been collected over much of Alaska and Canada during the 1997-98 winter and 1998 summer seasons. To complete the mosaics, these data will be augmented with data collected during previous years. These data will be made available to the scientific community via CD ROM containing these and similar data sets compiled from companion studies of Asia and Europe. Regional landscape classification with SAR is important for the baseline information it will provide about distribution of woodlands, positions of treeline, current forest biomass, distribution of wetlands, and extent of major rivercourses. As well as setting the stage for longer term change detection, comparisons across several years provides additional baseline information about short-term landscape change. Rapid changes, including those driven by fire, permafrost heat balance, flooding, and insect outbreaks can dominate boreal systems. We examine JERS-1 imagery covering selected sites in Alaska and Canada to assess quality and applicability to such relevant ecological and hydrological issues. The data are generally of high quality and illustrate many potential applications. A texture-based classification scheme is applied to selected regions to assess the applicability of these data for distinguishing distribution of such landcover types as wetland, tundra, woodland and forested landscapes.

  5. 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...

  6. 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.

  7. Long-term boreal forest dynamics and disturbances: a multi-proxy approach

    Science.gov (United States)

    Stivrins, Normunds; Aakala, Tuomas; Kuuluvainen, Timo; Pasanen, Leena; Ilvonen, Liisa; Holmström, Lasse; Seppä, Heikki

    2017-04-01

    The boreal forest provides a variety of ecosystem services that are threatened under the ongoing climate warming. Along with the climate, there are several factors (fire, human-impact, pathogens), which influence boreal forest dynamics. Combination of short and long-term studies allowing complex assessment of forest response to natural abiotic and biotic stress factors is necessary for sustainable management of the boreal forest now and in the future. The ongoing EBOR (Ecological history and long-term dynamics of the boreal forest ecosystem) project integrates forest ecological and palaeoecological approaches to study boreal forest dynamics and disturbances. Using pollen, non-pollen palynomorphs, micro- and macrocharcoal, tree rings and fire scars, we analysed forest dynamics at stand-scale by sampling small forest hollows (small paludified depressions) and the surrounding forest stands in Finland and western Russia. Using charcoal data, we estimated a fire return interval of 320 years for the Russian sites, and, based on the fungi Neurospora that can grow on charred tree bark after a low-intensity fire, we were able to distinguish low- and high-intensity fire-events. In addition to the influence of fire events and/or fire regime changes, we further assessed potential relationships between tree species and herbivore presence and pathogens. As an example of such a relationship, our preliminary findings indicated a negative relationship between Picea and fungi Lasiosphaeria (caudata), which occurred during times of Picea decline.

  8. Organic matter characteristics in boreal forest soils under stands of silver birch, Norway spruce, and Norway spruce with a mixture of silver birch

    Science.gov (United States)

    Smolander, A.; Kitunen, V.

    2012-04-01

    The aim was to study how tree species and a tree species mixture affect microbial C and N transformations and two major plant secondary compound groups, terpenes and phenolic compounds in soil. The study site was a tree-species experiment in middle-eastern part of Finland containing plots of 43-year-old silver birch, Norway spruce and Norway spruce with a mixture of silver birch (22 and 37 % birch of the total stem number). Soil was podzol and humus type mor. Samples were taken from the organic layer. C and N in the microbial biomass, rates of C mineralization (CO2 evolution), net N mineralization and nitrification, and concentrations of total water-soluble phenolic compounds, condensed tannins and different kind of terpenes were measured. Amounts of C and N in the microbial biomass and the rates of C mineralization and net N mineralization were all lower under spruce than birch, and particularly net N mineralization was stimulated by birch mixture. Concentrations of total water-soluble phenolic compounds were on a similar level, irrespective of tree species. However, there were less low-molecular-weight phenolics and more high-molecular-weight phenolics under spruce than birch. Concentrations of condensed tannins and both sesqui- and diterpenes were all higher under spruce than birch but the concentrations of triterpenes were similar in all soils. The difference between tree species was greatest with monoterpenes which were measured from both organic layer and soil atmosphere: high concentrations under spruce and negligible under birch. Birch mixture tended to decrease the concentrations of condensed tannins and mono-, sesqui- and diterpenes.

  9. Evolution of Canada’s Boreal Forest Spatial Patterns as Seen from Space

    Science.gov (United States)

    Pickell, Paul D.; Coops, Nicholas C.; Gergel, Sarah E.; Andison, David W.; Marshall, Peter L.

    2016-01-01

    Understanding the development of landscape patterns over broad spatial and temporal scales is a major contribution to ecological sciences and is a critical area of research for forested land management. Boreal forests represent an excellent case study for such research because these forests have undergone significant changes over recent decades. We analyzed the temporal trends of four widely-used landscape pattern indices for boreal forests of Canada: forest cover, largest forest patch index, forest edge density, and core (interior) forest cover. The indices were computed over landscape extents ranging from 5,000 ha (n = 18,185) to 50,000 ha (n = 1,662) and across nine major ecozones of Canada. We used 26 years of Landsat satellite imagery to derive annualized trends of the landscape pattern indices. The largest declines in forest cover, largest forest patch index, and core forest cover were observed in the Boreal Shield, Boreal Plain, and Boreal Cordillera ecozones. Forest edge density increased at all landscape extents for all ecozones. Rapidly changing landscapes, defined as the 90th percentile of forest cover change, were among the most forested initially and were characterized by four times greater decrease in largest forest patch index, three times greater increase in forest edge density, and four times greater decrease in core forest cover compared with all 50,000 ha landscapes. Moreover, approximately 18% of all 50,000 ha landscapes did not change due to a lack of disturbance. The pattern database results provide important context for forest management agencies committed to implementing ecosystem-based management strategies. PMID:27383055

  10. Evolution of Canada's Boreal Forest Spatial Patterns as Seen from Space.

    Science.gov (United States)

    Pickell, Paul D; Coops, Nicholas C; Gergel, Sarah E; Andison, David W; Marshall, Peter L

    2016-01-01

    Understanding the development of landscape patterns over broad spatial and temporal scales is a major contribution to ecological sciences and is a critical area of research for forested land management. Boreal forests represent an excellent case study for such research because these forests have undergone significant changes over recent decades. We analyzed the temporal trends of four widely-used landscape pattern indices for boreal forests of Canada: forest cover, largest forest patch index, forest edge density, and core (interior) forest cover. The indices were computed over landscape extents ranging from 5,000 ha (n = 18,185) to 50,000 ha (n = 1,662) and across nine major ecozones of Canada. We used 26 years of Landsat satellite imagery to derive annualized trends of the landscape pattern indices. The largest declines in forest cover, largest forest patch index, and core forest cover were observed in the Boreal Shield, Boreal Plain, and Boreal Cordillera ecozones. Forest edge density increased at all landscape extents for all ecozones. Rapidly changing landscapes, defined as the 90th percentile of forest cover change, were among the most forested initially and were characterized by four times greater decrease in largest forest patch index, three times greater increase in forest edge density, and four times greater decrease in core forest cover compared with all 50,000 ha landscapes. Moreover, approximately 18% of all 50,000 ha landscapes did not change due to a lack of disturbance. The pattern database results provide important context for forest management agencies committed to implementing ecosystem-based management strategies.

  11. Depression of belowground respiration rates at simulated high moose population densities in boreal forests.

    Science.gov (United States)

    Persson, Inga-Lill; Nilsson, Mats B; Pastor, John; Eriksson, Tobias; Bergström, Roger; Danell, Kjell

    2009-10-01

    Large herbivores can affect the carbon cycle in boreal forests by changing productivity and plant species composition, which in turn could ultimately alter litter production, nutrient cycling, and the partitioning between aboveground and belowground allocation of carbon. Here we experimentally tested how moose (Alces alces) at different simulated population densities affected belowground respiration rates (estimated as CO2 flux) in young boreal forest stands situated along a site productivity gradient. At high simulated population density, moose browsing considerably depressed belowground respiration rates (24-56% below that of no-moose controls) except during June, where the difference only was 10%. Moose browsing depressed belowground respiration the most on low-productivity sites. Soil moisture and temperature did not affect respiration rates. Impact of moose on belowground respiration was closely linked to litter production and followed Michaelis-Menten dynamics. The main mechanism by which moose decrease belowground respiration rates is likely their effect on photosynthetic biomass (especially decreased productivity of deciduous trees) and total litter production. An increased productivity of deciduous trees along the site productivity gradient causes an unequal effect of moose along the same gradient. The rapid growth of deciduous trees may offer higher resilience against negative effects of moose browsing on litter production and photosynthate allocation to roots.

  12. Contrasting responses of epiphytic and terricolous lichens to variations in forest characteristics in northern boreal ecosystems

    National Research Council Canada - National Science Library

    Boudreault, Catherine; Drapeau, Pierre; Bouchard, Mathieu; St-Laurent, Martin-Hugues; Imbeau, Louis; Bergeron, Yves

    2015-01-01

    ...) on fruticose epiphytic and terricolous lichen communities across a large region located at the interface between closed-crown boreal forests and northern open woodlands in the province of Quebec (Canada...

  13. 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

    The Athabasca oil sands deposit, located in the boreal forests of Northern Alberta, is one of the largest single oil deposits in the world. This deposit rests underneath 40,200 square kilometres of land. To date, an area of about 715 square kilometres has been disturbed by oil sands mining activity (Government of Alberta, 2013). Following surface mining, companies have the legal obligation to restore soil-like profiles that can support the previous land capabilities (Powter et al., 2012). Because of its importance for site productivity, re-establishment of the nitrogen cycle between these reconstructed soils and plants is one of the most critical factors required to insure long term sustainability of reclaimed boreal landscape. High nitrogen deposition recorded in the oil sands area combined with the high level of nitrate found in reclaimed soils raised concerns about the possibility of these reclaimed soils being in early stages of N saturation (Laxton et al 2010; Hemsley, 2012), although little evidence of net nitrification in these reclaimed soils suggests the contrary (Laxton et al. 2012). To date, results on the behaviour of the nitrogen cycle in the reclaimed sites are contradictory. A systematic study of the nitrogen cycle, and especially rates of gross mineralization, nitrification and denitrification, is needed. Our research aimed at 1) measuring the gross rates of nitrogen transformations under different vegetation treatments in both reclaimed and naturally-disturbed (fire) sites and 2) characterizing the microbial communities participating in the nitrogen cycle within the same soils. A series of 20 soils, covering different vegetation treatments (plots planted with aspen (Populus tremuloides), spruce (Picea glauca) and grassland) were investigated. Gross nitrogen transformation rates were measured using 15N pool-dilution (Müller et al. 2007). Microbial communities participating in the N-cycle were characterized using qPCR and pyrosequencing. Differences

  14. Nitrogen drives the growth of secondary forests in the Amazon: what analogies with temperate and boreal forests?

    Directory of Open Access Journals (Sweden)

    Tonon G

    2007-12-01

    Full Text Available Nitrogen drives the growth of secondary forests in the Amazon: what analogies with temperate and boreal forests? A comment is made on a recent paper published on Nature (Davidson et al. 2007, in which the authors demonstrate that in the young secondary forests in the Amazon a conservative nitrogen cycle prevails and nitrogen is a key factor driving forest growth. Analogies are also discussed with recent findings on the role of nitrogen deposition on the carbon balance of temperate and boreal forests (Magnani et al. 2007.

  15. 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.

  16. 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.

  17. 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.

  18. Patterns of canopy and surface layer consumption in a boreal forest fire from repeat airborne lidar

    Science.gov (United States)

    Alonzo, Michael; Morton, Douglas C.; Cook, Bruce D.; Andersen, Hans-Erik; Babcock, Chad; Pattison, Robert

    2017-05-01

    Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaska’s Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30 m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broadleaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from aboveground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn

  19. Ecosystem services of boreal forests - Carbon budget mapping at high resolution.

    Science.gov (United States)

    Akujärvi, Anu; Lehtonen, Aleksi; Liski, Jari

    2016-10-01

    The carbon (C) cycle of forests produces ecosystem services (ES) such as climate regulation and timber production. Mapping these ES using simple land cover -based proxies might add remarkable inaccuracy to the estimates. A framework to map the current status of the C budget of boreal forested landscapes was developed. The C stocks of biomass and soil and the annual change in these stocks were quantified in a 20 × 20 m resolution at the regional level on mineral soils in southern Finland. The fine-scale variation of the estimates was analyzed geo-statistically. The reliability of the estimates was evaluated by comparing them to measurements from the national multi-source forest inventory. The C stocks of forests increased slightly from the south coast to inland whereas the changes in these stocks were more uniform. The spatial patches of C stocks were larger than those of C stock changes. The patch size of the C stocks reflected the spatial variation in the environmental conditions, and that of the C stock changes the typical area of forest management compartments. The simulated estimates agreed well with the measurements indicating a good mapping framework performance. The mapping framework is the basis for evaluating the effects of forest management alternatives on C budget at high resolution across large spatial scales. It will be coupled with the assessment of other ES and biodiversity to study their relationships. The framework integrated a wide suite of simulation models and extensive inventory data. It provided reliable estimates of the human influence on C cycle in forested landscapes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. 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.

  1. Vulnerability of the boreal forest to climate change: are managed forests more susceptible?

    Energy Technology Data Exchange (ETDEWEB)

    Leduc, A. [Quebec Univ., Montreal, PQ (Canada); Gauthier, S. [Natural Resources Canada, Saint-Foy, PQ (Canada). Canadian Forest Service, Laurentian Forestry Centre; Bergeron, Y.; Harvey, B. [Quebec Univ., Abitibi-Temiscaminque, PQ (Canada)

    2004-02-01

    This paper postulates that forests dominated by younger seral stages are less vulnerable to climate change that those composed of mature and overmature stands. To support this analysis, an overview of expected changes in climate conditions was provided. Expected changes include higher maximum temperatures, higher minimum temperatures and a decrease in periods of intense cold and fewer frost days; reduction in the diurnal temperature range; an increase in the apparent heat index; greater numbers of intense precipitation; and, increased risk of drought associated with air mass movements. A comparison between conditions in a managed forest mosaic and natural forests was made, with managed forests differing due to efforts to regulate the age structure. The inversion in the age structure of forest mosaics creates significant changes in structural characteristics and composition, including greater hardwood components and more even-aged stands. It was concluded that in Canada, managed boreal forests are younger and have less black spruce and more hardwoods and fir, making younger forests less vulnerable to fire and more amenable to fire control due to increased accessibility. It was also noted that because of their relative youth, managed forests are more vulnerable to regeneration failure and that managed forests with more balsam fir and trembling aspen are at greater risk for insect outbreaks. In addition, wind throw, a threat to older forests, is not significant in managed forests. 15 refs., 1 tab., 2 figs.

  2. The likely impact of elevated [CO2], nitrogen deposition, increased temperature and management on carbon sequestration in temperate and boreal forest ecosystems: a literature review

    Science.gov (United States)

    Riitta Hyvönen; Göran I. Ågren; Sune Linder; Tryggve Persson; M. Francesca Cotrufo; Alf Ekblad; Michael Freeman; Achim Grelle; Ivan A. Janssens; Paul G. Jarvis; Seppo Kellomäki; Anders Lindroth; Denis Loustau; Tomas Lundmark; Richard J. Norby; Ram Oren; Kim Pilegaard; Michael G. Ryan; Bjarni D. Sigurdsson; Monika Strömgren; Marcel van Oijen; Göran Wallin

    2007-01-01

    Temperate and boreal forest ecosystems contain a large part of the carbon stored on land, in the form of both biomass and soil organic matter. Increasing atmospheric [CO2], increasing temperature, elevated nitrogen deposition and intensified management will change this C store. Well documented single-factor responses of net primary production are: higher photosynthetic...

  3. Workshop on Functional Aspects of Regeneration of the Boreal Forest in the Context of Sustainable Forest Management

    Science.gov (United States)

    Christian Messier; John Zasada; David Greene

    1999-01-01

    The three review papers presented in this issue of the Canadian Journal of Forest Research follow a 1-day workshop that was held in Montreal in early January 1997 entitled Functional Aspects of Regeneration In the Boreal Forest in the Context of Sustainable Forest Management. This workshop was held as part of the regeneration working group of Canada...

  4. 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.)

  5. 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

  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. Net aboveground biomass declines of four major forest types with forest ageing and climate change in western Canada's boreal forests.

    Science.gov (United States)

    Chen, Han Y H; Luo, Yong

    2015-10-01

    Biomass change of the world's forests is critical to the global carbon cycle. Despite storing nearly half of global forest carbon, the boreal biome of diverse forest types and ages is a poorly understood component of the carbon cycle. Using data from 871 permanent plots in the western boreal forest of Canada, we examined net annual aboveground biomass change (ΔAGB) of four major forest types between 1958 and 2011. We found that ΔAGB was higher for deciduous broadleaf (DEC) (1.44 Mg ha(-1)  year(-1) , 95% Bayesian confidence interval (CI), 1.22-1.68) and early-successional coniferous forests (ESC) (1.42, CI, 1.30-1.56) than mixed forests (MIX) (0.80, CI, 0.50-1.11) and late-successional coniferous (LSC) forests (0.62, CI, 0.39-0.88). ΔAGB declined with forest age as well as calendar year. After accounting for the effects of forest age, ΔAGB declined by 0.035, 0.021, 0.032 and 0.069 Mg ha(-1)  year(-1) per calendar year in DEC, ESC, MIX and LSC forests, respectively. The ΔAGB declines resulted from increased tree mortality and reduced growth in all forest types except DEC, in which a large biomass loss from mortality was accompanied with a small increase in growth. With every degree of annual temperature increase, ΔAGB decreased by 1.00, 0.20, 0.55 and 1.07 Mg ha(-1)  year(-1) in DEC, ESC, MIX and LSC forests, respectively. With every cm decrease of annual climatic moisture availability, ΔAGB decreased 0.030, 0.045 and 0.17 Mg ha(-1)  year(-1) in ESC, MIX and LSC forests, but changed little in DEC forests. Our results suggest that persistent warming and decreasing water availability have profound negative effects on forest biomass in the boreal forests of western Canada. Furthermore, our results indicate that forest responses to climate change are strongly dependent on forest composition with late-successional coniferous forests being most vulnerable to climate changes in terms of aboveground biomass. © 2015 John Wiley & Sons Ltd.

  8. Microbial life in frozen boreal soils-environmental constraints on catabolic and anabolic activity

    Science.gov (United States)

    Oquist, M. G.; Sparrman, T.; Haei, M.; Segura, J.; Schleucher, J.; Nilsson, M. B.

    2013-12-01

    Microbial activity in frozen soils has recently gained increasing attention and the fact that soil microorganisms can perform significant metabolic activity at temperatures below freezing is apparent. However, to what extent microbial activity is constrained by the environmental conditions prevailing in a frozen soil matrix is still very uncertain. This presentation will address how the fundamental environmental factors of temperature, liquid water availability and substrate availability combine to regulate rates of catabolic and anabolic microbial processes in frozen soils. The presented results are gained from investigations of the surface layers of boreal forest soils with 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. In turn, the capacity for a specific soil to retain liquid water at sub-zero temperatures is controlled by the structural composition of the soil, and especially the soil organic matter is of integral importance. 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. 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

  9. Effect of ditching operations on stream-water chemistry in a boreal forested catchment.

    Science.gov (United States)

    Aström, M; Aaltonen, E K; Koivusaari, J

    2001-11-12

    The effects of ditching of boreal forest land on stream-water quality and quantity was assessed by comparing, over a 4-year-period, the physicochemical properties of the water in two small streams (western Finland), one whose catchment was ditched for forestry halfway through the sampling period and another nearby (control) stream whose catchment was not ditched ('paired catchment method'). While the artificial drainage did not have any significant effect on the hydrograph, it resulted in an increase in the aquatic concentrations of Mn, Ca, Mg, suspended material and alkalinity, a decrease in the concentrations of TOC and H3O+, while for Al and Fe there was a change in control mechanisms. The concentration and control changes after ditching are related to changes in hydrological pathways and to the exposure of both organic (peat) and inorganic (mineral soil) layers on the ditch slopes.

  10. 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

  11. 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

  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. Assessing various drought indicators in representing drought in boreal forests in Finland

    Science.gov (United States)

    Gao, Y.; Markkanen, T.; Thum, T.; Aurela, M.; Lohila, A.; Mammarella, I.; Hagemann, S.; Aalto, T.

    2015-08-01

    Droughts can impact on forest functioning and production, and even lead to tree mortality. However, drought is an elusive phenomenon that is difficult to quantify and define universally. In this study, we assessed the performance of a set of indicators that have been used to describe drought conditions in the summer months (June, July, August) over a 30 year period (1981-2010) in Finland. Those indicators include the Standardized Precipitation Index (SPI), the Standardized Precipitation-Evapotranspiration Index (SPEI), the Soil Moisture Index (SMI) and the Soil Moisture Anomaly (SMA). Herein, regional soil moisture was produced by the land surface model JSBACH. While SPI, SPEI, and SMA show a degree of anomalies from the statistical means over a period, SMI is directly connected to plant available water and closely dependent on soil properties. Moreover, the buffering effect of soil moisture and the associated soil moisture memory can impact on the onset and duration of drought as indicated by the SMI and SMA, whereas SPI and SPEI are directly controlled by meteorological conditions. In particular, we investigated whether the SMI, SMA and SPEI are able to indicate the Extreme Drought affecting Forest health (EDF) in Finland. EDF thresholds for these indicators are suggested, based on the spatially representative statistics of forest health observations in the exceptional dry year 2006. Our results showed that SMI was the best indicator in capturing the spatial extent of forest damage induced by the extreme drought in 2006. In addition, the derived thresholds were applied to those indicators to capture EDF events over the summer months of the 30 year study period. The SPEI and SMA showed more frequent EDF events over the 30 year period, and typically described a higher fraction of influenced area than SMI. In general, the suggested EDF thresholds for those indicators may be used for the indication of EDF events in Finland or other boreal forests areas in the context

  14. Assessing various drought indicators in representing drought in boreal forests in Finland

    Directory of Open Access Journals (Sweden)

    Y. Gao

    2015-08-01

    Full Text Available Droughts can impact on forest functioning and production, and even lead to tree mortality. However, drought is an elusive phenomenon that is difficult to quantify and define universally. In this study, we assessed the performance of a set of indicators that have been used to describe drought conditions in the summer months (June, July, August over a 30 year period (1981–2010 in Finland. Those indicators include the Standardized Precipitation Index (SPI, the Standardized Precipitation–Evapotranspiration Index (SPEI, the Soil Moisture Index (SMI and the Soil Moisture Anomaly (SMA. Herein, regional soil moisture was produced by the land surface model JSBACH. While SPI, SPEI, and SMA show a degree of anomalies from the statistical means over a period, SMI is directly connected to plant available water and closely dependent on soil properties. Moreover, the buffering effect of soil moisture and the associated soil moisture memory can impact on the onset and duration of drought as indicated by the SMI and SMA, whereas SPI and SPEI are directly controlled by meteorological conditions. In particular, we investigated whether the SMI, SMA and SPEI are able to indicate the Extreme Drought affecting Forest health (EDF in Finland. EDF thresholds for these indicators are suggested, based on the spatially representative statistics of forest health observations in the exceptional dry year 2006. Our results showed that SMI was the best indicator in capturing the spatial extent of forest damage induced by the extreme drought in 2006. In addition, the derived thresholds were applied to those indicators to capture EDF events over the summer months of the 30 year study period. The SPEI and SMA showed more frequent EDF events over the 30 year period, and typically described a higher fraction of influenced area than SMI. In general, the suggested EDF thresholds for those indicators may be used for the indication of EDF events in Finland or other boreal forests

  15. Microbial community response to permafrost thaw after wildfire in an Alaskan upland boreal forest

    Science.gov (United States)

    Tas, N.; Jorgenson, M. T.; Wang, S.; Berhe, A. A.; Wickland, K. P.; Waldrop, M. P.; Jansson, J. K.

    2012-12-01

    Fire is a major factor controlling the long-term dynamics of soil carbon in Alaskan boreal forests. Wildfire not only contributes to a significant global emission of greenhouse gasses but also can indirectly result in the deepening of the active layer and thawing of near-surface permafrost due to reductions in organic layer depth and increases in heat flux through soil. Although boreal ecosystems are fire-adapted, increased fire frequency and rising global temperatures may result in warmer soils and therefore increase the metabolic rates of decomposer microbes and result in accelerated permafrost decomposition and greenhouse gas fluxes. In addition to fire-mediated changes in soil and vegetation structure, changes in the soil microbial community structure are likely to have consequences for rates of soil carbon cycling. In this study we aimed to define the impact of fire on soil microbial communities in an upland black spruce forest and to assess microbial metabolic potential for soil respiration, methanogenesis, and nitrous oxide (N2O) flux. Soil samples from two fire impacted and three control (unburned) locations were collected near Nome Creek, AK, an upland moderately drained black spruce forest. This location was within the Boundary fire that burned between mid-June and the end of August 2004. Soil temperature measurements from before and after the fire showed that soils were warmer after the fire event and the permafrost thawed below 1m. At each sampling location, soil and permafrost samples were collected every 10 cm to a depth of 1 m. Besides biochemical characterization, CO2, CH4, N2O fluxes and potential activities of enzymes involved in extracellular decomposition of complex organic molecules (hemicellulose, chitin and lignin) were measured. The microbial community composition in the samples was determined by sequencing of 16S rRNA genes and microbial metabolic potential was assessed via sequencing of total genomic DNA (metagenomics) in selected active

  16. No growth stimulation of Canada's boreal forest under half-century of combined warming and CO2 fertilization.

    Science.gov (United States)

    Girardin, Martin P; Bouriaud, Olivier; Hogg, Edward H; Kurz, Werner; Zimmermann, Niklaus E; Metsaranta, Juha M; de Jong, Rogier; Frank, David C; Esper, Jan; Büntgen, Ulf; Guo, Xiao Jing; Bhatti, Jagtar

    2016-12-27

    Considerable evidence exists that current global temperatures are higher than at any time during the past millennium. However, the long-term impacts of rising temperatures and associated shifts in the hydrological cycle on the productivity of ecosystems remain poorly understood for mid to high northern latitudes. Here, we quantify species-specific spatiotemporal variability in terrestrial aboveground biomass stem growth across Canada's boreal forests from 1950 to the present. We use 873 newly developed tree-ring chronologies from Canada's National Forest Inventory, representing an unprecedented degree of sampling standardization for a large-scale dendrochronological study. We find significant regional- and species-related trends in growth, but the positive and negative trends compensate each other to yield no strong overall trend in forest growth when averaged across the Canadian boreal forest. The spatial patterns of growth trends identified in our analysis were to some extent coherent with trends estimated by remote sensing, but there are wide areas where remote-sensing information did not match the forest growth trends. Quantifications of tree growth variability as a function of climate factors and atmospheric CO2 concentration reveal strong negative temperature and positive moisture controls on spatial patterns of tree growth rates, emphasizing the ecological sensitivity to regime shifts in the hydrological cycle. An enhanced dependence of forest growth on soil moisture during the late-20th century coincides with a rapid rise in summer temperatures and occurs despite potential compensating effects from increased atmospheric CO2 concentration.

  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. Global greenhouse to icehouse and back again: The origin and future of the Boreal Forest biome

    Science.gov (United States)

    Taggart, Ralph E.; Cross, Aureal T.

    2009-02-01

    The Boreal Forest biome (Taiga), dominated by evergreen and deciduous coniferous trees (Pinaceae), is circumpolar in its present distribution, covering a significant part of the total land area of the Northern Hemisphere and representing perhaps a third of the total forest area of the planet. Nothing comparable to this extant biome existed during the global "greenhouse" interval of the Late Mesozoic and Paleogene. Latitudinal temperature gradients should have confined boreal taxa to extremely high latitudes, but evergreen taxa do not appear to have been competitive in the lowlands of the high arctic, where the vegetation consisted of a unique circumpolar forest dominated by deciduous conifers and broad-leaved taxa. Probable sources for the pinaceous taxa that now characterize boreal latitudes were the Paleogene evergreen montane coniferous forests of the western North American Cordillera. Taphonomic factors limit the fossil record for such forests, but assemblages such as the Eocene Thunder Mountain (Idaho) and Bull Run (Nevada) floras were dominated by evergreen and deciduous Pinaceae that dominate extant montane, subalpine, and Boreal Forest associations. In response to post-Eocene global cooling, such forests presumably would have migrated to lower elevations, eventually spreading across high-latitude North America, subsequently reaching Eurasia via the Beringian corridor. This high-diversity coniferous forest was differentially winnowed and modified during subsequent migration southward in both the New and Old World. Despite its extensive geographic distribution, the Boreal Forest may be the youngest of the major forest biomes. If global warming ultimately results in a significant redistribution of terrestrial vegetation, the history of the Boreal Forest may well be reversed. Northward migration of the Boreal Forest may be characterized by loss of taxa and extensive community reorganization as individual taxa are pushed to their limits with respect to rates of

  19. Effects of an Experimental Drought on Balsam Fir Xylogenesis in the Eastern Canada Boreal Forest.

    Science.gov (United States)

    D'Orangeville, L.; Côté, B.; Houle, D.; Morin, H.

    2014-12-01

    A 20-40% reduction in soil moisture is projected for the boreal forest of Eastern Canada for the period 2070-99 relative to 1971-2000. In order to better predict the effects of a reduced water supply on the growth of balsam fir (Abies balsamea (L.) Mill.), a dominant tree species of the boreal forest, we simulated 2 consecutive years of summer droughts (starting in July) by means of throughfall exclusion. Four 100-m2 plots were established in 2010 with polyethylene sheets maintained 1.3-2 m aboveground and redirecting the water outside the plots. Wood microcores were extracted weekly from mature trees from April to October 2011 to analyse the time dynamics of wood formation in that year. The number of tracheids formed during and before treatment and their anatomical characteristics were determined through microscopic analyses. The growth of lateral and terminal branches and the water potential of balsam fir seedlings were also monitored. Throughfall exclusion significantly reduced soil water content by 5.8% in 2010 and 10.5% in 2011. Xylogenesis was affected significantly by the treatment. Tracheids were 16.1% smaller in diameter and their cell wall was 14.1% thicker during both years. The treatment delayed by more than a week the start of the tracheid differentiation process in the second year with a concomitant decrease (26%) in the number of tracheids produced. The seedlings displayed a 32% reduction in growth and a 40% reduction in leaf water potential. Our results suggest that a future regime of increased frequency and intensity of droughts could have nega­tive effects on the duration of xylogenesis and the amount of carbon sequestrated in balsam fir.

  20. 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

  1. 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

  2. Oxygenated VOC and monoterpene emissions from a boreal coniferous forest

    Science.gov (United States)

    Taipale, R.; Rantala, P.; Kajos, M. K.; Patokoski, J.; Ruuskanen, T. M.; Aalto, J.; Kolari, P.; Bäck, J.; Hari, P.; Kulmala, M.; Rinne, J.

    2012-04-01

    Compared with terpenoids, emissions of oxygenated volatile organic compounds (VOCs) from boreal ecosystems have been poorly characterized. We measured ecosystem scale emissions of three oxygenated compounds (methanol, acetaldehyde, and acetone) and monoterpenes from a Scots pine dominated forest in southern Finland during the summers 2006-2008. The measurements were conducted using the disjunct eddy covariance method combined with proton transfer reaction mass spectrometry. The contribution of the three oxygenated compounds to the measured total emissions was 40-60 %. The highest oxygenated VOC emissions were those of methanol, comprising 20-30 % of the total, followed by acetone with a share of 10-20 %. The acetaldehyde emissions were 5-10 % of the total. This emission composition will be compared with that obtained from shoot enclosure measurements. Methanol showed deposition during some periods although its overall flux was towards the atmosphere. The monoterpene emissions had a light dependent component, suggesting that part of the emissions originated directly from monoterpene biosynthesis. Diurnal, seasonal, and inter-annual variations in the emissions, along with temperature and light dependencies, will be discussed.

  3. Earthworm impacts on organo-mineral interactions and soil carbon inventories in Fennoscandian boreal and sub-arctic landscapes

    Science.gov (United States)

    Wackett, Adrian; Yoo, Kyungsoo; Cameron, Erin; Klaminder, Jonatan

    2017-04-01

    Boreal and sub-arctic environments sustain some of the most pristine and fragile ecosystems in the world and house a disproportionate amount of the global soil carbon pool. Although the historical view of soil carbon turnover has focused on the intrinsic molecular structure of organic matter, recent work has highlighted the importance of stabilizing soil carbon on reactive mineral surfaces. However, the rates and mechanisms controlling these processes at high latitudes are poorly understood. Here we explored the biogeochemical impacts of deep-burrowing earthworm species on a range of Fennoscandian forest soils to investigate how earthworms impact soil carbon inventories and organo-mineral associations across boreal and sub-arctic landscapes. We sampled soils and earthworms at six sites spanning almost ten degrees latitude and encompassing a wide range of soil types and textures, permitting simultaneous consideration of how climate and mineralogy affect earthworm-mediated shifts in soil carbon dynamics. Across all sites, earthworms significantly decreased the carbon and nitrogen contents of the upper 10 cm, presumably through consumption of the humus layer and subsequent incorporation of the underlying mineral soil into upper organic horizons. Their mixing of humus and underlying soil also generally increased the proportion of mineral surface area occluded by organic matter, although the extent to which earthworms facilitate such organo-mineral interactions appears to be controlled by soil texture and mineralogy. This work indicates that quantitative measurements of mineral surface area and its extent of coverage by soil organic matter facilitate scaling up of molecular interactions between organic matter and minerals to the level of soil profiles and landscapes. Our preliminary data also strongly suggests that earthworms have profound effects on the fate of soil carbon and nitrogen in boreal and sub-arctic environments, highlighting the need for a better

  4. 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.

  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. Measurement and modeling of bryophyte evaporation in a boreal forest chronosequence

    Energy Technology Data Exchange (ETDEWEB)

    Bond-Lamberty, Benjamin; Gower, Stith T.; Amiro, Brian; Ewers, Brent

    2011-01-19

    The effects of changing climate and disturbance on forest water cycling are not well understood. In particular bryophytes contribute significantly to forest evapotranspiration (ET) in poorly-drained boreal forests, but few studies have directly measured this flux and how it changes with stand age and soil drainage. We used large chambers to measure bryophyte evaporation (E) in Canadian Picea mariana forests of varying ages and soil drainages, as well under controlled laboratory conditions, and modeled daily E using site-specific meteorological data to drive a Penman-Monteith-based model. Field measurements of E averaged 0.37 mm day-1, and ranged from 0.03 (Pleurozium schreberii in a 77-year-old dry stand) to 1.43 mm day-1 (Sphagnum riparium in a 43-year-old bog). canopy resistance ranged from ~0 (at 25 °C, some values were <0) to ~1500 s m-1 for dry, cold (5 °C) mosses. In the laboratory, moss canopy resistance was constant until a moss water content of ~6 g g-1 and then climbed sharply with further drying; no difference was observed between the three moss groups (feather mosses, hollow mosses, and hummock mosses) tested. Modeled annual E fluxes from bryophytes ranged from 0.4 mm day-1, in the well-drained stands, to ~1 mm day-1 in the 43-year-old bog, during the growing season. Eddy covariance data imply that bryophytes contributed 18-31% and 49-69% to the total ET flux, at the well- and poorly-drained stands respectively. Bryophyte E was greater in bogs than in upland stands, was driven by low-lying mosses, and did not vary with stand age; this suggests that shifts in forest age due to increasing fire will have little effect on the bryophyte contribution to ET.

  7. 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.

  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. Effects of Nitrogen Fertilization of Boreal Forest Land on Greenhouse Gas Flows

    Science.gov (United States)

    Gustavsson, L.; Sathre, R. C.

    2011-12-01

    Forest growth on mineral soils in boreal regions is often limited by a low availability of nitrogen (N), and fertilization has shown particular promise in increasing yields in productive boreal forests. In this study we analyze the greenhouse gas (GHG) implications of increasing forest biomass production through N fertilization and using the increased production for bioenergy and biomaterials in place of non-renewable fuels and materials. We begin with a stand-level analysis of the radiative forcing implications of forest fertilization and biomass substitution, with explicit consideration of the temporal patterns of GHG emissions to and removals from the atmosphere. We model and compare the production and use of biomass from a hectare of fertilized and non-fertilized forest land in northern Sweden. We calculate the annual net emissions of CO2, N2O and CH4 for each system, over a 225-year period with 1-year time steps. We calculate the annual atmospheric concentration decay of each of these emissions, and calculate the resulting annual changes in instantaneous and cumulative radiative forcing. We find that forest fertilization can significantly increase biomass production, which increases the potential for material and energy substitution. The average carbon stock in tree biomass, forest soils and wood products all increase when fertilization is used. The additional GHG emissions due to fertilizer production and application are small compared to increases in carbon stock and substitution benefits. By the end of the 225-year simulation period, the cumulative radiative forcing reduction of the fertilized stand is over twice that of the non-fertilized stand. We then consider a steady-state landscape-level scenario where 10% of Swedish forest land is fertilized. We estimate the primary energy use and GHG emissions from forest management including production and application of N and NPK fertilizers. Based on modelled growth response, we then estimate the net GHG benefits

  10. Estimation of above ground biomass in boreal forest using ground-based Lidar

    Science.gov (United States)

    Taheriazad, L.; Moghadas, H.; Sanchez-Azofeifa, A.

    2017-05-01

    Assessing above ground biomass of forest is important for carbon storage monitoring in boreal forest. In this study, a new model is developed to estimate the above ground biomass using ground based Lidar data. 21 trees were measured and scanned across the plot area study in boreal forests of Alberta, Canada. The study area was scanned in the summer season 2014 to quantify the green biomass. The average of total crown biomass and green biomass in this study was 377 kg (standard deviation, S.D. = 243 kg) and 6.42 kg (S.D. = 2.69 m), respectively.

  11. Defining fire environment zones in the boreal forests of northeastern China.

    Science.gov (United States)

    Wu, Zhiwei; He, Hong S; Yang, Jian; Liang, Yu

    2015-06-15

    Fire activity in boreal forests will substantially increase with prolonged growing seasons under a warming climate. This trend poses challenges to managing fires in boreal forest landscapes. A fire environment zone map offers a basis for evaluating these fire-related problems and designing more effective fire management plans to improve the allocation of management resources across a landscape. Toward that goal, we identified three fire environment zones across boreal forest landscapes in northeastern China using analytical methods to identify spatial clustering of the environmental variables of climate, vegetation, topography, and human activity. The three fire environment zones were found to be in strong agreement with the spatial distributions of the historical fire data (occurrence, size, and frequency) for 1966-2005. This paper discusses how the resulting fire environment zone map can be used to guide forest fire management and fire regime prediction. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Lightning as a major driver of recent large fire years in North American boreal forests

    Science.gov (United States)

    Veraverbeke, Sander; Rogers, Brendan M.; Goulden, Mike L.; Jandt, Randi R.; Miller, Charles E.; Wiggins, Elizabeth B.; Randerson, James T.

    2017-07-01

    Changes in climate and fire regimes are transforming the boreal forest, the world's largest biome. Boreal North America recently experienced two years with large burned area: 2014 in the Northwest Territories and 2015 in Alaska. Here we use climate, lightning, fire and vegetation data sets to assess the mechanisms contributing to large fire years. We find that lightning ignitions have increased since 1975, and that the 2014 and 2015 events coincided with a record number of lightning ignitions and exceptionally high levels of burning near the northern treeline. Lightning ignition explained more than 55% of the interannual variability in burned area, and was correlated with temperature and precipitation, which are projected to increase by mid-century. The analysis shows that lightning drives interannual and long-term ignition and burned area dynamics in boreal North America, and implies future ignition increases may increase carbon loss while accelerating the northward expansion of boreal forest.

  13. Evaluating hillslope and riparian contributions to dissolved nitrogen (N) export from a boreal forest catchment

    Science.gov (United States)

    Blackburn, M.; Ledesma, José L. J.; Näsholm, Torgny; Laudon, Hjalmar; Sponseller, Ryan A.

    2017-02-01

    Catchment science has long held that the chemistry of small streams reflects the landscapes they drain. However, understanding the contribution of different landscape units to stream chemistry remains a challenge which frequently limits our understanding of export dynamics. For limiting nutrients such as nitrogen (N), an implicit assumption is that the most spatially extensive landscape units (e.g., uplands) act as the primary sources to surface waters, while near-stream zones function more often as sinks. These assumptions, based largely on studies in high-gradient systems or in regions with elevated inputs of anthropogenic N, may not apply to low-gradient, nutrient-poor, and peat-rich catchments characteristic of many northern ecosystems. We quantified patterns of N mobilization along a hillslope transect in a northern boreal catchment to assess the extent to which organic matter-rich riparian soils regulate the flux of N to streams. Contrary to the prevailing view of riparian functioning, we found that near-stream, organic soils supported concentrations and fluxes of ammonium (NH4+) and dissolved organic nitrogen that were much higher than the contributing upslope forest soils. These results suggest that stream N chemistry is connected to N mobilization and mineralization within the riparian zone rather than the wider landscape. Results further suggest that water table fluctuation in near-surface riparian soils may promote elevated rates of net N mineralization in these landscapes.

  14. 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

  15. Relative importance of different secondary successional pathways in an Alaskan boreal forest

    Science.gov (United States)

    Thomas A. Kurkowski; Daniel H. Mann; T. Scott Rupp; David L. Verbyla

    2008-01-01

    Postfire succession in the Alaskan boreal forest follows several different pathways, the most common being self-replacement and species-dominance relay. In self-replacement, canopy-dominant tree species replace themselves as the postfire dominants. It implies a relatively unchanging forest composition through time maintained by trees segregated within their respective...

  16. 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.

  17. 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.

  18. 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.

  19. The changing effects of Alaska’s boreal forests on the climate system

    Science.gov (United States)

    Euskirchen, E.S.; McGuire, Anthony; Chapin, F.S.; Rupp, T.S.

    2010-01-01

    In the boreal forests of Alaska, recent changes in climate have influenced the exchange of trace gases, water, and energy between these forests and the atmosphere. These changes in the structure and function of boreal forests can then feed back to impact regional and global climates. In this manuscript, we examine the type and magnitude of the climate feedbacks from boreal forests in Alaska. Research generally suggests that the net effect of a warming climate is a positive regional feedback to warming. Currently, the primary positive climate feedbacks are likely related to decreases in surface albedo due to decreases in snow cover. Fewer negative feedbacks have been identified, and they may not be large enough to counterbalance the large positive feedbacks. These positive feedbacks are most pronounced at the regional scale and reduce the resilience of the boreal vegetation – climate system by amplifying the rate of regional warming. Given the recent warming in this region, the large variety of associated mechanisms that can alter terrestrial ecosystems and influence the climate system, and a reduction in the boreal forest resilience, there is a strong need to continue to quantify and evaluate the feedback pathways.

  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. Comparison of coniferous forest carbon stocks between old-growth and young second-growth forests on two soil types in central British Columbia, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Fredeen, A.L.; Bois, C.H.; Janzen, D.T.; Sanborn, P.T. [Northern British Columbia Univ., Prince George, BC (Canada). Faculty of Natural Resources and Environmental Studies

    2005-06-01

    More than half of the world's terrestrial organic soil and vegetation carbon (C) currently resides in forests, with one half of this in boreal forests alone. Forests therefore represent significant reservoirs of carbon. A study was conducted at the Aleza Lake Research Forest (ALRF) near Prince George, British Columbia to compare the C stocks in 4 old-growth sub-boreal spruce (SBS) forests with 4 corresponding young, planted second-growth stands in soils of contrasting textures. The 2 dominant soil textures were coarse and fine grained soils over a total of 16 plots. The C stocks were assessed for hybrid interior spruce-dominated upland forests within the ALRF. For each plot, the carbon content of tree biomass was estimated using the measured values of Lamlom and Savidge. All woody debris stocks including tree stumps were also evaluated and soil C stocks were sampled according to modified National Forest Inventory Sampling Guidelines. C stocks were also tested for mineral soil texture, age-class and their interaction effects. The average total C stocks for old-growth stands ranged from 423 Mg C per hectare to 324 Mg C per hectare, between Pacific Northwest temperate forest and upland boreal forests. It was concluded that sub-boreal forests of central British Columbia are intermediate in terms of aboveground and total carbon stocks between the wetter and more productive coastal forests to the south and west and the less productive boreal stands to the north and east. It was concluded that conservation of non-biomass C stocks in old-growth forests is important in minimizing greenhouse gas emissions resulting from sub-boreal forest management activities. 60 refs., 2 tabs., 4 figs.

  2. 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.

  3. 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

  4. Spectral reflectance patterns and temporal dynamics of common understory types in hemi-boreal forests in Järvselja, Estonia

    Science.gov (United States)

    Nikopensius, Maris; Raabe, Kairi; Pisek, Jan

    2014-05-01

    The knowledge about spectral properties and seasonal dynamics of understory layers in boreal forests currently holds several gaps. This introduces severe uncertainties while modelling the carbon balance of this ecosystem, which is expected to be prone to major shifts with climate change in the future. In this work the seasonal reflectance dynamics in European hemi-boreal forests are studied. The data for this study was collected at Järvselja Training and Experimental Forestry District (Estonia, 27.26°E 58.30°N). Measurements were taken in three different stands. The silver birch (Betula Pendula Roth) stand grows on typical brown gley-soil and its understory vegetation is dominated by a mixture of several grass species. The Scots pine (Pinus sylvestris) stand grows on a bog with understory vegetation composed of sparse labrador tea, cotton grass, and a continuous Sphagnum moss layer. The third stand, Norway spruce (Picea abies), grows on a Gleyi Ferric Podzol site with understory vegetation either partially missing or consisting of mosses such as Hylocomium splendens or Pleurozium schreberi [1]. The sampling design was similar to the study by Rautiainen et al. [3] in northern European boreal forests. At each study site, a 100 m long permanent transect was marked with flags. In addition, four intensive study plots (1 m × 1 m) were marked next to the transects at 20 m intervals. The field campaign lasted from May to September 2013. For each site the fractional cover of understory and understory spectra were estimated ten times i.e. every 2 to 3 weeks. Results from Järvselja forest were compared with the seasonal profiles from boreal forests in Hyytiälä, Finland [2]. References [1] A. Kuusk, M. Lang, J. Kuusk, T. Lükk, T. Nilson, M. Mõttus, M. Rautiainen, and A. Eenmäe, "Database of optical and structural data for validation of radiative transfer models", Technical Report, September 2009 [2] M. Rautiainen, M. Mõttus, J. Heiskanen, A. Akujärvi, T. Majasalmi

  5. 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

  6. 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.

  7. 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 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. © 2016 John Wiley & Sons Ltd.

  8. 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

  9. Modelling black spruce primary production and carbon allocation in the Quebec boreal forest

    Science.gov (United States)

    Gennaretti, Fabio; Guiot, Joel; Berninger, Frank; Boucher, Etienne; Gea-Izquierdo, Guillermo

    2017-04-01

    Boreal ecosystems are crucial carbon stores that must be urgently quantified and preserved. Their future evolution is extremely important for the global carbon budget. Here, we will show the progresses achieved with the MAIDEN forest ecophysiological model in simulating carbon fluxes of black spruce (Picea mariana (Mill.) B.S.P.) forests, the most representative ecosystem of the North American boreal biome. Starting from daily minimum-maximum air temperature, precipitation and CO2 atmospheric concentration, MAIDEN models the phenological (5 phenological phases are simulated each year) and meteorological controls on gross primary production (GPP) and carbon allocation to stem. The model is being calibrated on eddy covariance and tree-ring data. We will discuss the model's performance and the modifications introduced in MAIDEN to adapt the model to temperature sensitive forests of the boreal region.

  10. 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. Copyright © 2016, American Association for the Advancement of Science.

  11. Observation and modelling of HOx radicals in a boreal forest

    Directory of Open Access Journals (Sweden)

    K. Hens

    2014-08-01

    Full Text Available Measurements of OH and HO2 radicals were conducted in a pine-dominated forest in southern Finland during the HUMPPA-COPEC-2010 (Hyytiälä United Measurements of Photochemistry and Particles in Air – Comprehensive Organic Precursor Emission and Concentration study field campaign in summer 2010. Simultaneous side-by-side measurements of hydroxyl radicals were conducted with two instruments using chemical ionization mass spectrometry (CIMS and laser-induced fluorescence (LIF, indicating small systematic disagreement, OHLIF / OHCIMS = (1.31 ± 0.14. Subsequently, the LIF instrument was moved to the top of a 20 m tower, just above the canopy, to investigate the radical chemistry at the ecosystem–atmosphere interface. Comprehensive measurements including observations of many volatile organic compounds (VOCs and the total OH reactivity were conducted and analysed using steady-state calculations as well as an observationally constrained box model. Production rates of OH calculated from measured OH precursors are consistent with those derived from the steady-state assumption and measured total OH loss under conditions of moderate OH reactivity. The primary photolytic sources of OH contribute up to one-third to the total OH production. OH recycling, which occurs mainly by HO2 reacting with NO and O3, dominates the total hydroxyl radical production in this boreal forest. Box model simulations agree with measurements for hydroxyl radicals (OHmod. / OHobs. = 1.00 ± 0.16, while HO2 mixing ratios are significantly under-predicted (HO2mod. / HO2obs. = 0.3 ± 0.2, and simulated OH reactivity does not match the observed OH reactivity. The simultaneous under-prediction of HO2 and OH reactivity in periods in which OH concentrations were simulated realistically suggests that the missing OH reactivity is an unaccounted-for source of HO2. Detailed analysis of the HOx production, loss, and recycling pathways suggests that in periods of high total OH reactivity

  12. Persistent and pervasive compositional shifts of western boreal forest plots in Canada.

    Science.gov (United States)

    Searle, Eric B; Chen, Han Y H

    2017-02-01

    Species compositional shifts have important consequences to biodiversity and ecosystem function and services to humanity. In boreal forests, compositional shifts from late-successional conifers to early-successional conifers and deciduous broadleaves have been postulated based on increased fire frequency associated with climate change truncating stand age-dependent succession. However, little is known about how climate change has affected forest composition in the background between successive catastrophic fires in boreal forests. Using 1797 permanent sample plots from western boreal forests of Canada measured from 1958 to 2013, we show that after accounting for stand age-dependent succession, the relative abundances of early-successional deciduous broadleaves and early-successional conifers have increased at the expense of late-successional conifers with climate change. These background compositional shifts are persistent temporally, consistent across all forest stand ages and pervasive spatially across the region. Rising atmospheric CO2 promoted early-successional conifers and deciduous broadleaves, and warming increased early-successional conifers at the expense of late-successional conifers, but compositional shifts were not associated with climate moisture index. Our results emphasize the importance of climate change on background compositional shifts in the boreal forest and suggest further compositional shifts as rising CO2 and warming will continue in the 21st century. © 2016 John Wiley & Sons Ltd.

  13. The impact of climate change on forest fire danger rating in China's boreal forest

    Institute of Scientific and Technical Information of China (English)

    YANG Guang; DI Xue-ying; GUO Qing-xi; SHU Zhan; ZENG Tao; YU Hong-zhou; WANG Chao

    2011-01-01

    The Great Xing'an Mountains boreal forests were focused on in the northeastern China.The simulated future climate scenarios of IPCC SRES A2a and B2a for both the baseline period of 1961-1990 and the future scenario periods were downscaled by the Delta Method and the Weather Generator to produce daily weather data.After the verification with local weather and fire data, the Canadian Forest Fire Weather Index System was used to assess the forest fire weather situation under climate change in the study region.An increasing trend of fire weather severity was found over the 21st century in the study region under the both future climate change scenarios, compared to the 1961-1990 baseline period.The annual mean/maximum fire weather index was predicted to rise continuously during 2010-2099, and by the end of the 21st century it is predicted to rise by 22%-52% across much of China's boreal forest.The significant increases were predicted in the spring from of April to June and in the summer from July to August.In the summer, the fire weather index was predicted to be higher than the current index by as much as 148% by the end of the 21st century.Under the scenarios of SRES A2a and B2a, both the chance of extremely high fire danger occurrence and the number of days of extremely high fire danger occurrence was predieted to increase in the study region.It is anticipated that the number of extremely high fire danger days would increase from 44 days in 1980s to 53-75 days by the end of the 21st century.

  14. Overview of a prescribed burning experiment within a boreal forest in Finland

    Directory of Open Access Journals (Sweden)

    A. Virkkula

    2013-08-01

    Full Text Available A prescribed burning of a boreal forest was conducted on 26 June 2009 in Hyytiälä, Finland, to study aerosol and trace gas emissions from wildfires and the effects of fire on soil properties in a controlled environment. A 0.8 ha forest near the SMEAR II was cut clear; some tree trunks, all tree tops and branches were left on the ground and burned. The amount of burned organic material was ~46.8 t (i.e., ~60 t ha−1. The flaming phase lasted 2 h 15 min, the smoldering phase 3 h. Measurements were conducted on the ground with both fixed and mobile instrumentation, and from a research aircraft. In the middle of the burning area, CO2 concentration peaks were around 2000–3000 ppm above the baseline and peak vertical flow velocities were 6 ± 3 m s−1, as measured a 10-Hz 3-D sonic anemometer placed within the burn area. Peak particle number concentrations were approximately 1–2 × 106 cm−3 in the plume at a distance of 100–200 m from the burn area. The geometric mean diameter of the mode with the highest concentration was at 80 ± 1 nm during the flaming phase and in the middle of the smoldering phase but at the end of the smoldering phase the largest mode was at 122 nm. In the volume size distributions geometric mean diameter of the largest volume mode was at 153 nm during the flaming phase and at 300 nm during the smoldering phase. The lowest single-scattering albedo of the ground-level measurents was 0.7 in the flaming-phase plume and ~0.9 in the smoldering phase. The radiative forcing efficiency was negative above dark surfaces, in other words, the particles cool the atmosphere. Elevated concentrations of several VOCs (including acetonitrile which is a biomass burning marker were observed in the smoke plume at ground level. The forest floor (i.e., richly organic layer of soil and debris, characteristic of forested land measurements showed that VOC fluxes were generally low and consisted mainly of monoterpenes, but a clear peak of VOC

  15. Regional atmospheric cooling and wetting effect of permafrost thaw-induced boreal forest loss.

    Science.gov (United States)

    Helbig, Manuel; Wischnewski, Karoline; Kljun, Natascha; Chasmer, Laura E; Quinton, William L; Detto, Matteo; Sonnentag, Oliver

    2016-12-01

    In the sporadic permafrost zone of North America, thaw-induced boreal forest loss is leading to permafrost-free wetland expansion. These land cover changes alter landscape-scale surface properties with potentially large, however, still unknown impacts on regional climates. In this study, we combine nested eddy covariance flux tower measurements with satellite remote sensing to characterize the impacts of boreal forest loss on albedo, eco-physiological and aerodynamic surface properties, and turbulent energy fluxes of a lowland boreal forest region in the Northwest Territories, Canada. Planetary boundary layer modelling is used to estimate the potential forest loss impact on regional air temperature and atmospheric moisture. We show that thaw-induced conversion of forests to wetlands increases albedo: and bulk surface conductance for water vapour and decreases aerodynamic surface temperature. At the same time, heat transfer efficiency is reduced. These shifts in land surface properties increase latent at the expense of sensible heat fluxes, thus, drastically reducing Bowen ratios. Due to the lower albedo of forests and their masking effect of highly reflective snow, available energy is lower in wetlands, especially in late winter. Modelling results demonstrate that a conversion of a present-day boreal forest-wetland to a hypothetical homogeneous wetland landscape could induce a near-surface cooling effect on regional air temperatures of up to 3-4 °C in late winter and 1-2 °C in summer. An atmospheric wetting effect in summer is indicated by a maximum increase in water vapour mixing ratios of 2 mmol mol(-1) . At the same time, maximum boundary layer heights are reduced by about a third of the original height. In fall, simulated air temperature and atmospheric moisture between the two scenarios do not differ. Therefore, permafrost thaw-induced boreal forest loss may modify regional precipitation patterns and slow down regional warming trends. © 2016 John Wiley

  16. 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.

  17. Contrasting total carbon and nitrogen stocks between ecological site types in a Sub-Boreal research forest in central British Columbia

    Energy Technology Data Exchange (ETDEWEB)

    Bois, C.H.; Janzen, D.T. [Northern British Columbia Univ., Prince George, BC (Canada). Ecosystem Science and Management Program; Sanborn, P.T.; Fredeen, A.L. [Northern British Columbia Univ., Prince George, BC (Canada). Ecosystem Science and Management Program]|[Northern British Columbia Univ., Prince George, BC (Canada). Natural Resources and Environmental Studies Inst.

    2006-07-01

    Carbon (C) sequestration and carbon stocks within managed and natural forests have become topical issues since the adoption of the Kyoto Protocol. A multi-year study was conducted to evaluate the total C stocks present in a 10 km{sup 2} area of University of British Columbia's Aleza Lake Research Forest located 60 km east of Prince George in the Sub-Boreal Spruce biogeoclimatic zone of east-central British Columbia. The purpose was to address gaps in knowledge about forest C budgets, total pool sizes, dynamics of forest floor and mineral soil carbon by studying the effects of forest management. Sampling plots were chosen randomly within strata composed of the dominant ecological site classes, soil textures and management histories. The study involved the creation of 137 plots, of which 108 and 29 were located on fine and coarse textured soils, respectively. Sampling was reduced in these strata due to a shortage of middle-aged stands and the near lack of coarse textured soils. Data collection and sampling methodology were adapted from the National Forest Inventory Ground Sampling Guidelines of the Canadian Forest Service. Carbon stocks were measured in forest floor and mineral soil to a depth of 1 metre. The Dumas-combustion method was used to determine C and nitrogen (N) concentrations. It was determined that stand age did not decidedly change the forest floor or mineral soil total C and N in either fine or coarse textured soil plots. However, forest floor C and N were considerably higher in coarse textured soils compared to C and N measured in fine soil plots. Mineral soil C concentration decreased methodically with depth from 4.6 per cent C at 0 cm to 0.2 per cent at 100 cm. The paper also addressed the breakdown of forest floor and mineral soil C and N pools according to ecological site series.

  18. Effects of disturbance and climate change on ecosystem performance in the Yukon River Basin boreal forest

    Science.gov (United States)

    Wylie, Bruce K.; Rigge, Matthew B.; Brisco, Brian; Mrnaghan, Kevin; Rover, Jennifer R.; Long, Jordan

    2014-01-01

    A warming climate influences boreal forest productivity, dynamics, and disturbance regimes. We used ecosystem models and 250 m satellite Normalized Difference Vegetation Index (NDVI) data averaged over the growing season (GSN) to model current, and estimate future, ecosystem performance. We modeled Expected Ecosystem Performance (EEP), or anticipated productivity, in undisturbed stands over the 2000–2008 period from a variety of abiotic data sources, using a rule-based piecewise regression tree. The EEP model was applied to a future climate ensemble A1B projection to quantify expected changes to mature boreal forest performance. Ecosystem Performance Anomalies (EPA), were identified as the residuals of the EEP and GSN relationship and represent performance departures from expected performance conditions. These performance data were used to monitor successional events following fire. Results suggested that maximum EPA occurs 30–40 years following fire, and deciduous stands generally have higher EPA than coniferous stands. Mean undisturbed EEP is projected to increase 5.6% by 2040 and 8.7% by 2070, suggesting an increased deciduous component in boreal forests. Our results contribute to the understanding of boreal forest successional dynamics and its response to climate change. This information enables informed decisions to prepare for, and adapt to, climate change in the Yukon River Basin forest.

  19. Chemical characteristics of Siberian boreal forest fire emissions

    Science.gov (United States)

    Engling, G.; Popovicheva, O.; Fan, T. S.; Eleftheriadis, K.; Diapouli, E.; Kozlov, V.

    2014-12-01

    Smoke emissions from Siberian boreal forest fires exert critical impacts on the aerosol/climate system of subarctic regions and the Arctic. It is, therefore, crucial to assess the ability of such particles to absorb/scatter incoming solar radiation as well as act as cloud condensation nuclei, which is closely linked to the physical and chemical aerosol properties. However, observations of Siberian wildfire emissions are limited, and no systematic database of smoke particle properties is available for this region to date. As part of this study, ambient aerosol samples were collected during two smoke episodes in Tomsk, Siberia, in the summers of 2012 and 2013. In addition, the chemical composition and optical properties of smoke particles derived from the combustion of typical Siberian fuels, including pine wood and debris, were determined during chamber burn experiments in a large aerosol/combustion chamber under controlled combustion conditions representative of wildfires and prescribed burns. Detailed multi-component characterization of individual particles and bulk properties was accomplished with a suite of techniques, including various types of chromatography, microscopy, spectroscopy, and thermo-optical analysis. Individual particle analysis by SEM-EDX combined with cluster analysis revealed characteristic smoke structural components and major types of particles, which allowed to discriminate between flaming and smoldering regimes, reflected in specific morphological and chemical microstructure. The physicochemical properties representing the combustion phase (smoldering versus flaming) and the degree of processing (fresh versus aged) were assessed in the ambient aerosol based on the chamber burn results. For instance, some chemical transformation (aging of smoke particles) was noticed over a period of two days in the absence of sun light in the combustion chamber for certain chemical species, while the molecular tracer levoglucosan appeared to be rather

  20. Short-term effects of thinning, clear-cutting and stump harvesting on methane exchange in a boreal forest

    Directory of Open Access Journals (Sweden)

    E. Sundqvist

    2014-03-01

    Full Text Available Forest management practices can alter soil conditions, affecting the consumption and production processes that control soil methane (CH4 exchange. We studied the short-term effects of thinning, clear-cutting and stump harvesting on the CH4 exchange between soil and atmosphere at a boreal forest site in central Sweden, using an undisturbed plot as the control. Chambers in combination with a high precision laser gas analyser were used for continuous measurements. Both the undisturbed plot and the thinned plot were net sinks of CH4, whereas the clear-cut plot and the stump harvested plot were net CH4 sources. The CH4 uptake at the thinned plot was reduced in comparison to the undisturbed plot. The shift from sink to source at the clear-cut and stump harvested plots was probably due to a rise of the water table and an increase in soil moisture, leading to lower gas diffusivity and more reduced conditions which favour CH4 production by archea. Reduced evapotranspiration after harvesting leads to wetter soils, decreased CH4 consumption and increased CH4 production, and should be accounted for in the CH4 budget of managed forests.

  1. Emissions of forest floor and mineral soil carbon, nitrogen and mercury pools and relationships with fire severity for the Pagami Creek Fire in the Boreal Forest of northern Minnesota

    Science.gov (United States)

    Randall K. Kolka; Brian R. Sturtevant; Jessica R. Miesel; Aditya Singh; Peter T. Wolter; Shawn Fraver; Thomas M. DeSutter; Phil A. Townsend

    2017-01-01

    Forest fires cause large emissions of C (carbon), N (nitrogen) and Hg (mercury) to the atmosphere and thus have important implications for global warming (e.g. via CO2 and N2O emissions), anthropogenic fertilisation of natural ecosystems (e.g. via N deposition), and bioaccumulation of harmful metals in aquatic and...

  2. Forecasting the development of boreal paludified forests in response to climate change: a case study using Ontario ecosite classification

    Directory of Open Access Journals (Sweden)

    Benoit Lafleur

    2015-01-01

    Full Text Available Background Successional paludification, a dynamic process that leads to the formation of peatlands, is influenced by climatic factors and site features such as surficial deposits and soil texture. In boreal regions, projected climate change and corresponding modifications in natural fire regimes are expected to influence the paludification process and forest development. The objective of this study was to forecast the development of boreal paludified forests in northeastern North America in relation to climate change and modifications in the natural fire regime for the period 2011–2100. Methods A paludification index was built using static (e.g. surficial deposits and soil texture and dynamic (e.g. moisture regime and soil organic layer thickness stand scale factors available from forest maps. The index considered the effects of three temperature increase scenarios (i.e. +1°C, +3°C and +6°C and progressively decreasing fire cycle (from 300 years for 2011–2041, to 200 years for 2071–2100 on peat accumulation rate and soil organic layer (SOL thickness at the stand level, and paludification at the landscape level. Results Our index show that in the context where in the absence of fire the landscape continues to paludify, the negative effect of climate change on peat accumulation resulted in little modification to SOL thickness at the stand level, and no change in the paludification level of the study area between 2011 and 2100. However, including decreasing fire cycle to the index resulted in declines in paludified area. Overall, the index predicts a slight to moderate decrease in the area covered by paludified forests in 2100, with slower rates of paludification. Conclusions Slower paludification rates imply greater forest productivity and a greater potential for forest harvest, but also a gradual loss of open paludified stands, which could impact the carbon balance in paludified landscapes. Nonetheless, as the thick Sphagnum layer

  3. Soil strength and forest operations.

    NARCIS (Netherlands)

    Beekman, F.

    1987-01-01

    The use of heavy machinery and transport vehicles is an integral part of modern forest operations. This use often causes damage to the standing trees and to the soil. In this study the effects of vehicle traffic on the soil are analysed and the possible consequences for forest management discussed.

  4. Boreal forest riparian zones regulate stream sulfate and dissolved organic carbon.

    Science.gov (United States)

    Ledesma, José L J; Futter, Martyn N; Laudon, Hjalmar; Evans, Christopher D; Köhler, Stephan J

    2016-08-01

    In boreal forest catchments, solute transfer to streams is controlled by hydrological and biogeochemical processes occurring in the riparian zone (RZ). However, RZs are spatially heterogeneous and information about solute chemistry is typically limited. This is problematic when making inferences about stream chemistry. Hypothetically, the strength of links between riparian and stream chemistry is time-scale dependent. Using a ten-year (2003-2012) dataset from a northern Swedish catchment, we evaluated the suitability of RZ data to infer stream dynamics at different time scales. We focus on the role of the RZ versus upslope soils in controlling sulfate (SO4(2)(-)) and dissolved organic carbon (DOC). A priori, declines in acid deposition and redox-mediated SO4(2)(-) pulses control sulfur (S) fluxes and pool dynamics, which in turn affect dissolved organic carbon (DOC). We found that the catchment is currently a net source of S, presumably due to release of the S pool accumulated during the acidification period. In both, RZ and stream, SO4(2-) concentrations are declining over time, whereas DOC is increasing. No temporal trends in SO4(2-) and DOC were observed in upslope mineral soils. SO4(2-) explained the variation of DOC in stream and RZ, but not in upslope mineral soil. Moreover, as SO4(2-) decreased with time, temporal variability of DOC increased. These observations indicate that: (1) SO4(2-) is still an important driver of DOC trends in boreal catchments and (2) RZ processes control stream SO4(2-) and subsequently DOC independently of upslope soils. These phenomena are likely occurring in many regions recovering from acidification. Because water flows through a heterogeneous mosaic of RZs before entering the stream, upscaling information from limited RZ data to the catchment level is problematic at short-time scales. However, for long-term trends and annual dynamics, the same data can provide reasonable representations of riparian processes and support

  5. Measuring forest structure along productivity gradients in the Canadian boreal with small-footprint Lidar.

    Science.gov (United States)

    Bolton, Douglas K; Coops, Nicholas C; Wulder, Michael A

    2013-08-01

    The structure and productivity of boreal forests are key components of the global carbon cycle and impact the resources and habitats available for species. With this research, we characterized the relationship between measurements of forest structure and satellite-derived estimates of gross primary production (GPP) over the Canadian boreal. We acquired stand level indicators of canopy cover, canopy height, and structural complexity from nearly 25,000 km of small-footprint discrete return Light Detection and Ranging (Lidar) data and compared these attributes to GPP estimates derived from the MODerate resolution Imaging Spectroradiometer (MODIS). While limited in our capacity to control for stand age, we removed recently disturbed and managed forests using information on fire history, roads, and anthropogenic change. We found that MODIS GPP was strongly linked to Lidar-derived canopy cover (r = 0.74, p Lidar-derived canopy height and structural complexity as these attributes are largely a function of stand age. A relationship was apparent between MODIS GPP and the maximum sampled heights derived from Lidar as growth rates and resource availability likely limit tree height in the prolonged absence of disturbance. The most structurally complex stands, as measured by the coefficient of variation of Lidar return heights, occurred where MODIS GPP was highest as productive boreal stands are expected to contain a wider range of tree heights and transition to uneven-aged structures faster than less productive stands. While MODIS GPP related near-linearly to Lidar-derived canopy cover, the weaker relationships to Lidar-derived canopy height and structural complexity highlight the importance of stand age in determining the structure of boreal forests. We conclude that an improved quantification of how both productivity and disturbance shape stand structure is needed to better understand the current state of boreal forests in Canada and how these forests are changing in

  6. 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.

  7. Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

    Directory of Open Access Journals (Sweden)

    R. H. H. Janssen

    2011-08-01

    Full Text Available Seasonal variations in cloud droplet number concentration (NCD in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An uncertainty analysis of the cloud model is included to reveal the main sensitivities of the cloud model. We compared the seasonal cycle in NCD, obtained using 9 yr of satellite data, to surface concentrations of potential cloud activating aerosols, measured at the SMEAR II station at Hyytiälä in Finland. The results show that NCD and cloud condensation nuclei (CCN concentrations have no clear correlation at seasonal time scale. The fraction of aerosols that actually activate as cloud droplet decreases sharply with increasing aerosol concentrations. Furthermore, information on the stability of the atmosphere shows that low NCD is linked to stable atmospheric conditions. Combining these findings leads to the conclusion that cloud droplet activation for the studied clouds over the boreal forest is limited by convection. Our results suggest that it is important to take the strength of convection into account when studying the influence of aerosols from the boreal forest on cloud formation, although they do not rule out the possibility that aerosols from the boreal forest affect other types of clouds with a closer coupling to the surface.

  8. 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.

  9. Interactive effects of burn severity and canopy cover on ecophysiology of tree seedlings in boreal forests

    Science.gov (United States)

    Wildfires are an important disturbance because they improve habitat conditions for establishing plants. Fires of differing severity can have dramatically different impacts on habitat, particularly when coupled with canopy-level disturbances. In a boreal forest, we outplanted seedlings of four specie...

  10. 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.

  11. Dynamics of change in Alaska's boreal forests: resilience and vulnerability in response to climate warming

    Science.gov (United States)

    A. David McGuire; F.S. Chapin; R.W. Ruess

    2010-01-01

    Long-term research by the Bonanza Creek (BNZ) Long Term Ecological Research (LTER) program has documented natural patterns of interannual and successional variability of the boreal forest in interior Alaska against which we can detect changes in system behavior. Between 2004 and 2010 the BNZ LTER program focused on understanding the dynamics of change through studying...

  12. Dynamics of phytophagous insects and their pathogens in Alaskan boreal forests

    Science.gov (United States)

    Richard A. Werner; Kenneth F. Raffa; Barbara L. Illman

    2006-01-01

    Boreal forests support an array of insects, including phytophagous (plant-eating) insects, saprophagous (detritus-eating) insects, and their associated parasites, predators, and symbionts. The phytophagous species include folivorous leaf chewers and miners, phloeophagous cambial and sapwood borers, stem gallers, and root feeders. Biological diversity and distribution...

  13. 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.

  14. 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

  15. Fire severity filters regeneration traits to shape community assembly in Alaska's boreal forest.

    Directory of Open Access Journals (Sweden)

    Teresa N Hollingsworth

    Full Text Available Disturbance can both initiate and shape patterns of secondary succession by affecting processes of community assembly. Thus, understanding assembly rules is a key element of predicting ecological responses to changing disturbance regimes. We measured the composition and trait characteristics of plant communities early after widespread wildfires in Alaska to assess how variations in disturbance characteristics influenced the relative success of different plant regeneration strategies. We compared patterns of post-fire community composition and abundance of regeneration traits across a range of fire severities within a single pre-fire forest type- black spruce forests of Interior Alaska. Patterns of community composition, as captured by multivariate ordination with nonmetric multidimensional scaling, were primarily related to gradients in fire severity (biomass combustion and residual vegetation and secondarily to gradients in soil pH and regional climate. This pattern was apparent in both the full dataset (n = 87 sites and for a reduced subset of sites (n = 49 that minimized the correlation between site moisture and fire severity. Changes in community composition across the fire-severity gradient in Alaska were strongly correlated to variations in plant regeneration strategy and rooting depth. The tight coupling of fire severity with regeneration traits and vegetation composition after fire supports the hypothesis that disturbance characteristics influence patterns of community assembly by affecting the relative success of different regeneration strategies. This study further demonstrated that variations in disturbance characteristics can dominate over environmental constraints in determining early patterns of community assembly. By affecting the success of regeneration traits, changes in fire regime directly shape the outcomes of community assembly, and thus may override the effects of slower environmental change on boreal forest

  16. Fire severity filters regeneration traits to shape community assembly in Alaska's boreal forest.

    Science.gov (United States)

    Hollingsworth, Teresa N; Johnstone, Jill F; Bernhardt, Emily L; Chapin, F Stuart

    2013-01-01

    Disturbance can both initiate and shape patterns of secondary succession by affecting processes of community assembly. Thus, understanding assembly rules is a key element of predicting ecological responses to changing disturbance regimes. We measured the composition and trait characteristics of plant communities early after widespread wildfires in Alaska to assess how variations in disturbance characteristics influenced the relative success of different plant regeneration strategies. We compared patterns of post-fire community composition and abundance of regeneration traits across a range of fire severities within a single pre-fire forest type- black spruce forests of Interior Alaska. Patterns of community composition, as captured by multivariate ordination with nonmetric multidimensional scaling, were primarily related to gradients in fire severity (biomass combustion and residual vegetation) and secondarily to gradients in soil pH and regional climate. This pattern was apparent in both the full dataset (n = 87 sites) and for a reduced subset of sites (n = 49) that minimized the correlation between site moisture and fire severity. Changes in community composition across the fire-severity gradient in Alaska were strongly correlated to variations in plant regeneration strategy and rooting depth. The tight coupling of fire severity with regeneration traits and vegetation composition after fire supports the hypothesis that disturbance characteristics influence patterns of community assembly by affecting the relative success of different regeneration strategies. This study further demonstrated that variations in disturbance characteristics can dominate over environmental constraints in determining early patterns of community assembly. By affecting the success of regeneration traits, changes in fire regime directly shape the outcomes of community assembly, and thus may override the effects of slower environmental change on boreal forest composition.

  17. 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

  18. 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

  19. The interactive effects of temperature and light on biological nitrogen fixation in boreal forests.

    Science.gov (United States)

    Gundale, Michael J; Nilsson, Madeleine; Bansal, Sheel; Jäderlund, Anders

    2012-04-01

    Plant productivity is predicted to increase in northern latitudes as a result of climate warming; however, this may depend on whether biological nitrogen (N)-fixation also increases. We evaluated how the variation in temperature and light affects N-fixation by two boreal feather mosses, Pleurozium schreberi and Hylocomium splendens, which are the primary source of N-fixation in most boreal environments. We measured N-fixation rates 2 and 4 wk after exposure to a factorial combination of environments of normal, intermediate and high temperature (16.3, 22.0 and 30.3°C) and light (148.0, 295.7 and 517.3 μmol m(-2) s(-1)). Our results showed that P. schreberi achieved higher N-fixation rates relative to H. splendens in response to warming treatments, but that the highest warming treatment eventually caused N-fixation to decline for both species. Light strongly interacted with warming treatments, having positive effects at low or intermediate temperatures and damaging effects at high temperatures. These results suggest that climate warming may increase N-fixation in boreal forests, but that increased shading by the forest canopy or the occurrence of extreme temperature events could limit increases. They also suggest that P. schreberi may become a larger source of N in boreal forests relative to H. splendens as climate warming progresses. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

  20. 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.

  1. Effect of granulated wood ash fertilization on N2O emissions in boreal peat forests

    Science.gov (United States)

    Liimatainen, Maarit; Martikainen, Pertti J.; Hytönen, Jyrki; Maljanen, Marja

    2016-04-01

    explain this decrease in N2O production. Despite of the granulation process some nutrients (e.g. K, Na, B, S) still leach quickly from the ash in form of ions, which was observed as an increased electrical conductivity. Granulated ash contains a high concentration of sulfates and we created in the laboratory experiments with the addition of K2SO4 or (NH4)2SO4 similar decrease in N2O production as observed with the addition of granulated wood ash. Our results indicate that quickly leaching ions inhibit nitrification in peat. In the field experiments the same phenomena was not observed, probably due to leaching of the nutrients (ions) deeper into the soil and due to the competition of vegetation which outcompetes microbes for available nutrients. In conclusion, the use of granulated wood ash does not increase N2O emissions in boreal peat forests.

  2. Using Landsat data to assess fire and burn severity in the North American boreal forest region: an overview and summary of results

    Science.gov (United States)

    Nancy H.F. French; Eric S. Kasischke; Ronald J. Hall; Karen A. Murphy; David L. Verbyla; Elizabeth E. Hoy; Jennifer L. Allen

    2008-01-01

    There has been considerable interest in the recent literature regarding the assessment of post-fire effects on forested areas within the North American boreal forest. Assessing the physical and ecological effects of fire in boreal forests has far-reaching implications for a variety of ecosystem processes -- such as post-fire forest succession -- and land management...

  3. Chronic Nitrogen Deposition Has a Minor Effect on the Quantity and Quality of Aboveground Litter in a Boreal Forest.

    Science.gov (United States)

    Maaroufi, Nadia I; Nordin, Annika; Palmqvist, Kristin; Gundale, Michael J

    2016-01-01

    There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal soils. However, key underlying mechanisms explaining this increase have not been resolved. Two potentially important mechanisms are that aboveground litter production increases, or that litter quality changes in response to N enrichment. As such, our aim was to quantify whether simulated chronic N deposition caused changes in aboveground litter production or quality in a boreal forest. We conducted a long-term (17 years) stand-scale (0.1 ha) forest experiment, consisting of three N addition levels (0, 12.5, and 50 kg N ha-1 yr-1) in northern Sweden, where background N deposition rates are very low. We measured the annual quantity of litter produced for 8 different litter categories, as well as their concentrations of C, N, phosphorus (P), lignin, cellulose and hemi-cellulose. Our results indicate that mosses were the only major litter component showing significant quantitative and qualitative alterations in response to the N additions, indicative of their ability to intercept a substantial portion of the N added. These effects were, however, offset by the other litter fractions where we found no changes in the total litter fluxes, or individual chemical constituents when all litter categories were summed. This study indicates that the current annual litter fluxes cannot explain the increase in soil C that has occurred in our study system in response to simulated chronic N application. These results suggest that other mechanisms are likely to explain the increased soil C accumulation rate we have observed, such as changes in soil microbial activity, or potentially transient changes in aboveground litter inputs that were no longer present at the time of our study.

  4. 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).

  5. Contrasting responses of epiphytic and terricolous lichens to variations in forest characteristics in northern boreal ecosystems1

    National Research Council Canada - National Science Library

    St-Laurent, Martin-Hugues; Drapeau, Pierre; Imbeau, Louis; Boudreault, Catherine; Bouchard, Mathieu; Bergeron, Yves

    2015-01-01

    ...) on fruticose epiphytic and terricolous lichen communities across a large region located at the interface between closed-crown boreal forests and northern open woodlands in the province of Quebec (Canada...

  6. Underestimation of boreal soil carbon stocks by mathematical soil carbon models linked to soil nutrient status

    Science.gov (United States)

    Ťupek, Boris; Ortiz, Carina A.; Hashimoto, Shoji; Stendahl, Johan; Dahlgren, Jonas; Karltun, Erik; Lehtonen, Aleksi

    2016-08-01

    Inaccurate estimate of the largest terrestrial carbon pool, soil organic carbon (SOC) stock, is the major source of uncertainty in simulating feedback of climate warming on ecosystem-atmosphere carbon dioxide exchange by process-based ecosystem and soil carbon models. Although the models need to simplify complex environmental processes of soil carbon sequestration, in a large mosaic of environments a missing key driver could lead to a modeling bias in predictions of SOC stock change.We aimed to evaluate SOC stock estimates of process-based models (Yasso07, Q, and CENTURY soil sub-model v4) against a massive Swedish forest soil inventory data set (3230 samples) organized by a recursive partitioning method into distinct soil groups with underlying SOC stock development linked to physicochemical conditions.For two-thirds of measurements all models predicted accurate SOC stock levels regardless of the detail of input data, e.g., whether they ignored or included soil properties. However, in fertile sites with high N deposition, high cation exchange capacity, or moderately increased soil water content, Yasso07 and Q models underestimated SOC stocks. In comparison to Yasso07 and Q, accounting for the site-specific soil characteristics (e. g. clay content and topsoil mineral N) by CENTURY improved SOC stock estimates for sites with high clay content, but not for sites with high N deposition.Our analysis suggested that the soils with poorly predicted SOC stocks, as characterized by the high nutrient status and well-sorted parent material, indeed have had other predominant drivers of SOC stabilization lacking in the models, presumably the mycorrhizal organic uptake and organo-mineral stabilization processes. Our results imply that the role of soil nutrient status as regulator of organic matter mineralization has to be re-evaluated, since correct SOC stocks are decisive for predicting future SOC change and soil CO2 efflux.

  7. Multidecadal analysis of forest growth and albedo in boreal Finland

    Science.gov (United States)

    Lukeš, Petr; Stenberg, Pauline; Mõttus, Matti; Manninen, Terhikki; Rautiainen, Miina

    2016-10-01

    It is well known that forests serve as carbon sinks. However, the balancing effect of afforestation and increased forest density on global warming due to carbon storage may be lost by low albedo (thus high absorption) of the forests. In the last 30 years, there has been a steady increase in the growing stock of Finnish forests by nearly a quarter while the area of the forests has remained virtually unchanged. Such increase in forest density together with the availability of detailed forest inventories provided by the Multi-Source National Forest Inventory (MS-NFI) in high spatial resolution makes Finland an ideal candidate for exploring the effects of increased forest density on satellite derived estimates of bio-geochemical products e.g. albedo (directional-hemispherical reflectance, DHR), fraction of photosynthetically active radiation absorbed by canopies (fAPAR), leaf area index (LAI) and normalized difference vegetation index (NDVI) in both current and long-term perspective. In this study, we first used MODIS-based vegetation satellite products for Finnish forests to study their seasonal patterns and interrelations. Next, the peak growing season observations are linked to the MS-NFI database to yield the generic relationships between forest density and the satellite-derived vegetation indicators. Finally, long-term GIMMS3g datasets between 1982 and 2011 (2008 for DHR) are analyzed and interpreted using forest inventory data. The vegetation peak growing season NIR DHR and VIS DHR showed weak to moderate negative correlation with fAPAR, whereas there was no correlation between NIR DHR and fAPAR. Next, we show that the spectral albedos in the near-infrared region (NIR DHR) showed weak negative correlation with forest biomass, basal area or canopy cover whereas, as expected, the spectral albedo in the visible region (VIS DHR) correlated negatively with these measures of forest density. Interestingly, the increase in forest density (biomass per ha) of Finnish

  8. Regional drought-induced reduction in the biomass carbon sink of Canada's boreal forests.

    Science.gov (United States)

    Ma, Zhihai; Peng, Changhui; Zhu, Qiuan; Chen, Huai; Yu, Guirui; Li, Weizhong; Zhou, Xiaolu; Wang, Weifeng; Zhang, Wenhua

    2012-02-14

    The boreal forests, identified as a critical "tipping element" of the Earth's climate system, play a critical role in the global carbon budget. Recent findings have suggested that terrestrial carbon sinks in northern high-latitude regions are weakening, but there has been little observational evidence to support the idea of a reduction of carbon sinks in northern terrestrial ecosystems. Here, we estimated changes in the biomass carbon sink of natural stands throughout Canada's boreal forests using data from long-term forest permanent sampling plots. We found that in recent decades, the rate of biomass change decreased significantly in western Canada (Alberta, Saskatchewan, and Manitoba), but there was no significant trend for eastern Canada (Ontario and Quebec). Our results revealed that recent climate change, and especially drought-induced water stress, is the dominant cause of the observed reduction in the biomass carbon sink, suggesting that western Canada's boreal forests may become net carbon sources if the climate change-induced droughts continue to intensify.

  9. Continental divide: Predicting climate-mediated fragmentation and biodiversity loss in the boreal forest

    Science.gov (United States)

    Murray, Dennis L.; Peers, Michael J. L.; Majchrzak, Yasmine N.; Wehtje, Morgan; Ferreira, Catarina; Pickles, Rob S. A.; Row, Jeffrey R.; Thornton, Daniel H.

    2017-01-01

    Climate change threatens natural landscapes through shifting distribution and abundance of species and attendant change in the structure and function of ecosystems. However, it remains unclear how climate-mediated variation in species’ environmental niche space may lead to large-scale fragmentation of species distributions, altered meta-population dynamics and gene flow, and disrupted ecosystem integrity. Such change may be especially relevant when species distributions are restricted either spatially or to a narrow environmental niche, or when environments are rapidly changing. Here, we use range-wide environmental niche models to posit that climate-mediated range fragmentation aggravates the direct effects of climate change on species in the boreal forest of North America. We show that climate change will directly alter environmental niche suitability for boreal-obligate species of trees, birds and mammals (n = 12), with most species ranges becoming smaller and shifting northward through time. Importantly, species distributions will become increasingly fragmented, as characterized by smaller mean size and greater isolation of environmentally-suitable landscape patches. This loss is especially pronounced along the Ontario-Québec border, where the boreal forest is narrowest and roughly 78% of suitable niche space could disappear by 2080. Despite the diversity of taxa surveyed, patterns of range fragmentation are remarkably consistent, with our models predicting that spruce grouse (Dendragapus canadensis), boreal chickadee (Poecile hudsonicus), moose (Alces americanus) and caribou (Rangifer tarandus) could have entirely disjunct east-west population segments in North America. These findings reveal potentially dire consequences of climate change on population continuity and species diversity in the boreal forest, highlighting the need to better understand: 1) extent and primary drivers of anticipated climate-mediated range loss and fragmentation; 2) diversity of

  10. Continental divide: Predicting climate-mediated fragmentation and biodiversity loss in the boreal forest.

    Science.gov (United States)

    Murray, Dennis L; Peers, Michael J L; Majchrzak, Yasmine N; Wehtje, Morgan; Ferreira, Catarina; Pickles, Rob S A; Row, Jeffrey R; Thornton, Daniel H

    2017-01-01

    Climate change threatens natural landscapes through shifting distribution and abundance of species and attendant change in the structure and function of ecosystems. However, it remains unclear how climate-mediated variation in species' environmental niche space may lead to large-scale fragmentation of species distributions, altered meta-population dynamics and gene flow, and disrupted ecosystem integrity. Such change may be especially relevant when species distributions are restricted either spatially or to a narrow environmental niche, or when environments are rapidly changing. Here, we use range-wide environmental niche models to posit that climate-mediated range fragmentation aggravates the direct effects of climate change on species in the boreal forest of North America. We show that climate change will directly alter environmental niche suitability for boreal-obligate species of trees, birds and mammals (n = 12), with most species ranges becoming smaller and shifting northward through time. Importantly, species distributions will become increasingly fragmented, as characterized by smaller mean size and greater isolation of environmentally-suitable landscape patches. This loss is especially pronounced along the Ontario-Québec border, where the boreal forest is narrowest and roughly 78% of suitable niche space could disappear by 2080. Despite the diversity of taxa surveyed, patterns of range fragmentation are remarkably consistent, with our models predicting that spruce grouse (Dendragapus canadensis), boreal chickadee (Poecile hudsonicus), moose (Alces americanus) and caribou (Rangifer tarandus) could have entirely disjunct east-west population segments in North America. These findings reveal potentially dire consequences of climate change on population continuity and species diversity in the boreal forest, highlighting the need to better understand: 1) extent and primary drivers of anticipated climate-mediated range loss and fragmentation; 2) diversity of

  11. Palaeodata-informed modelling of large carbon losses from recent burning of boreal forests

    Science.gov (United States)

    Kelly, Ryan; Genet, Helene; McGuire, Anthony; Hu, Feng Sheng

    2016-01-01

    Wildfires play a key role in the boreal forest carbon cycle1, 2, and models suggest that accelerated burning will increase boreal C emissions in the coming century3. However, these predictions may be compromised because brief observational records provide limited constraints to model initial conditions4. We confronted this limitation by using palaeoenvironmental data to drive simulations of long-term C dynamics in the Alaskan boreal forest. Results show that fire was the dominant control on C cycling over the past millennium, with changes in fire frequency accounting for 84% of C stock variability. A recent rise in fire frequency inferred from the palaeorecord5 led to simulated C losses of 1.4 kg C m−2 (12% of ecosystem C stocks) from 1950 to 2006. In stark contrast, a small net C sink of 0.3 kg C m−2 occurred if the past fire regime was assumed to be similar to the modern regime, as is common in models of C dynamics. Although boreal fire regimes are heterogeneous, recent trends6 and future projections7 point to increasing fire activity in response to climate warming throughout the biome. Thus, predictions8 that terrestrial C sinks of northern high latitudes will mitigate rising atmospheric CO2 may be over-optimistic.

  12. 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.

  13. 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.

  14. 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

  15. Foreword: The dynamics of change in Alaska’s boreal forests: Resilience and vulnerability in response to climate warming

    Science.gov (United States)

    McGuire, Anthony; Chapin, F. Stuart; Ruess, Roger W.

    2016-01-01

    Long-term research by the Bonanza Creek (BNZ) Long Term Ecological Research (LTER) program has documented natural patterns of interannual and successional variability of the boreal forest in interior Alaska against which we can detect changes in system behavior. Between 2004 and 2010 the BNZ LTER program focused on understanding the dynamics of change through studying the resilience and vulnerability of Alaska's boreal forest in response to climate warming. The overarching question in this endeavor has been “How are boreal ecosystems responding, both gradually and abruptly, to climate warming, and what new landscape patterns are emerging?”

  16. Frost heaving of planted tree seedlings in the boreal forest of northern Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Goulet, France

    2000-07-01

    Frost heaving can be a leading cause of tree seedling mortality in many places in the boreal forest of Northern Sweden. The aim of this investigation was to improve our understanding of frost heaving of planted tree seedlings as related to snow cover, scarification, planting methods and soil types. The thesis is based on a review paper, three field experiments and one laboratory experiment. The experiments focus on different methods to control frost heaving of forest tree seedlings and on a number of factors affecting the extent of frost heaving. The review paper identifies the many aspects of frost heaving of forest tree seedlings and agricultural crops based on an intensive review of the research contributions made during the last century. Even if many investigations have been carried out with the aim to decrease the extent of frost heaving, very little quantitative results are available for tree seedlings. In a field experiment, the choice of planting positions was effective in decreasing frost heaving of planted seedlings following mounding or disc-trenching. Seedlings planted in the depressions were largely affected by frost heaving with a maximal vertical displacement of 5.4 cm while frost heaving did not occur on the top of the mound. On the other hand, the planting time and planting depth had no influence on the extent of frost heaving. In another field experiment the size of the scarified patches was strongly correlated to frost heaving which reached between 7.6 and 11.5 cm in 4 and 8-dm patches compared to between 4.4 and 5.3 in non-scarified soil and in a 1-dm patch. Ground vegetation probably decreases the diurnal temperature variation and the number of freezing-thawing cycles. The duration and magnitude of frost temperatures, the frost hour sum, increased with patch size. The difference between the 8-dm and 1-dm patch increased to 2064 hour-degrees at the end of the winter. In larger patches, the planting depth seemed to be effective in reducing the

  17. 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.

  18. 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

  19. 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.

  20. Optimal conservation resource allocation under variable economic and ecological time discounting rates in boreal forest

    DEFF Research Database (Denmark)

    Mazziotta, Adriano; Montesino Pouzols, Federico; Mönkkönen, Mikko

    2016-01-01

    that in boreal forest set-aside followed by protection of clear-cuts can become a winning cost-effective strategy when accounting for habitat requirements of multiple species, long planning horizon, and limited budget. It is particularly effective when adopting a long-term sustainability perspective......, and accounting for present revenues from timber harvesting. The present analysis assesses the cost-effective conditions to allocate resources into an inexpensive conservation strategy that nevertheless has potential to produce high ecological values in the future.......Resource allocation to multiple alternative conservation actions is a complex task. A common trade-off occurs between protection of smaller, expensive, high-quality areas versus larger, cheaper, partially degraded areas. We investigate optimal allocation into three actions in boreal forest: current...

  1. 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.

  2. What makes segmentation good? A case study in boreal forest habitat mapping

    OpenAIRE

    Räsänen, Aleksi; Rusanen, Antti; Kuitunen, Markku; Lensu, Anssi

    2013-01-01

    Segmentation goodness evaluation is a set of approaches meant for deciding which segmentation is good. In this study, we tested different supervised segmentation evaluation measures and visual interpretation in the case of boreal forest habitat mapping in Southern Finland. The data used were WorldView-2 satellite imagery, a lidar digital elevation model (DEM), and a canopy height model (CHM) in 2 m resolution. The segmentation methods tested were the fractal net evolution approach (FNEA) and ...

  3. Biotic stress accelerates formation of climate-relevant aerosols in boreal forests

    Science.gov (United States)

    Joutsensaari, J.; Yli-Pirilä, P.; Korhonen, H.; Arola, A.; Blande, J. D.; Heijari, J.; Kivimäenpää, M.; Mikkonen, S.; Hao, L.; Miettinen, P.; Lyytikäinen-Saarenmaa, P.; Faiola, C. L.; Laaksonen, A.; Holopainen, J. K.

    2015-11-01

    Boreal forests are a major source of climate-relevant biogenic secondary organic aerosols (SOAs) and will be greatly influenced by increasing temperature. Global warming is predicted to not only increase emissions of reactive biogenic volatile organic compounds (BVOCs) from vegetation directly but also induce large-scale insect outbreaks, which significantly increase emissions of reactive BVOCs. Thus, climate change factors could substantially accelerate the formation of biogenic SOAs in the troposphere. In this study, we have combined results from field and laboratory experiments, satellite observations and global-scale modelling in order to evaluate the effects of insect herbivory and large-scale outbreaks on SOA formation and the Earth's climate. Field measurements demonstrated 11-fold and 20-fold increases in monoterpene and sesquiterpene emissions respectively from damaged trees during a pine sawfly (Neodiprion sertifer) outbreak in eastern Finland. Laboratory chamber experiments showed that feeding by pine weevils (Hylobius abietis) increased VOC emissions from Scots pine and Norway spruce seedlings by 10-50 fold, resulting in 200-1000-fold increases in SOA masses formed via ozonolysis. The influence of insect damage on aerosol concentrations in boreal forests was studied with a global chemical transport model GLOMAP and MODIS satellite observations. Global-scale modelling was performed using a 10-fold increase in monoterpene emission rates and assuming 10 % of the boreal forest area was experiencing outbreak. Results showed a clear increase in total particulate mass (local max. 480 %) and cloud condensation nuclei concentrations (45 %). Satellite observations indicated a 2-fold increase in aerosol optical depth over western Canada's pine forests in August during a bark beetle outbreak. These results suggest that more frequent insect outbreaks in a warming climate could result in substantial increase in biogenic SOA formation in the boreal zone and, thus

  4. Summer movements, predation and habitat use of wolves in human modified boreal forests.

    Science.gov (United States)

    Gurarie, Eliezer; Suutarinen, Johanna; Kojola, Ilpo; Ovaskainen, Otso

    2011-04-01

    Grey wolves (Canis lupus), formerly extirpated in Finland, have recolonized a boreal forest environment that has been significantly altered by humans, becoming a patchwork of managed forests and clearcuts crisscrossed by roads, power lines, and railways. Little is known about how the wolves utilize this impacted ecosystem, especially during the pup-rearing summer months. We tracked two wolves instrumented with GPS collars transmitting at 30-min intervals during two summers in eastern Finland, visiting all locations in the field, identifying prey items and classifying movement behaviors. We analyzed preference and avoidance of habitat types, linear elements and habitat edges, and tested the generality of our results against lower resolution summer movements of 23 other collared wolves. Wolves tended to show a strong preference for transitional woodlands (mostly harvested clearcuts) and mixed forests over coniferous forests and to use forest roads and low use linear elements to facilitate movement. The high density of primary roads in one wolf's territory led to more constrained use of the home territory compared to the wolf with fewer roads, suggesting avoidance of humans; however, there did not appear to be large differences on the hunting success or the success of pup rearing for the two packs. In total, 90 kills were identified, almost entirely moose (Alces alces) and reindeer (Rangifer tarandus sspp.) calves of which a large proportion were killed in transitional woodlands. Generally, wolves displayed a high level of adaptability, successfully exploiting direct and indirect human-derived modifications to the boreal forest environment.

  5. Are Boreal Ovenbirds, Seiurus aurocapilla, More Prone to Move across Inhospitable Landscapes in Alberta's Boreal Mixedwood Forest than in Southern Québec's Temperate Deciduous Forest?

    Directory of Open Access Journals (Sweden)

    Marc Bélisle

    2007-12-01

    Full Text Available Population life-history traits such as the propensity to move across inhospitable landscapes should be shaped by exposure to landscape structure over evolutionary time. Thus, birds that recently evolved in landscapes fragmented by natural disturbances such as fire would be expected to show greater behavioral and morphological vagility relative to conspecifics that evolved under less patchy landscapes shaped by fewer and finer-scaled disturbances, i.e., the resilience hypothesis. These predictions are not new, but they remain largely untested, even for well-studied taxa such as neotropical migrant birds. We combined two experimental translocation, i.e., homing, studies to test whether Ovenbird, Seiurus aurocapilla, from the historically dynamic boreal mixedwood forest of north-central Alberta (n = 55 is more vagile than Ovenbird from historically less dynamic deciduous forest of southern Québec (n = 89. We found no regional difference in either wing loading or the response of homing Ovenbird to landscape structure. Nevertheless, this study presents a heuristic framework that can advance the understanding of boreal landscape dynamics as an evolutionary force.

  6. High-latitude cooling associated with landscape changes from North American boreal forest fires

    Directory of Open Access Journals (Sweden)

    B. M. Rogers

    2013-02-01

    Full Text Available Fires in the boreal forests of North America are generally stand-replacing, killing the majority of trees and initiating succession that may last over a century. Functional variation during succession can affect local surface energy budgets and, potentially, regional climate. Burn area across Alaska and Canada has increased in the last few decades and is projected to be substantially higher by the end of the 21st century because of a warmer climate with longer growing seasons. Here we simulated changes in forest composition due to altered burn area using a stochastic model of fire occurrence, historical fire data from national inventories, and succession trajectories derived from remote sensing. When coupled to an Earth system model, younger vegetation from increased burning cooled the high-latitude atmosphere, primarily in the winter and spring, with noticeable feedbacks from the ocean and sea ice. Results from multiple scenarios suggest that a doubling of burn area would cool the surface by 0.23 ± 0.09 °C across boreal North America during winter and spring months (December through May. This could provide a negative feedback to winter warming on the order of 3–5% for a doubling, and 14–23% for a quadrupling, of burn area. Maximum cooling occurs in the areas of greatest burning, and between February and April when albedo changes are largest and solar insolation is moderate. Further work is needed to integrate all the climate drivers from boreal forest fires, including aerosols and greenhouse gasses.

  7. Waterfowl populations are resilient to immediate and lagged impacts of wildfires in the boreal forest

    Science.gov (United States)

    Lewis, Tyler; Schmutz, Joel A.; Amundson, Courtney L.; Lindberg, Mark S.

    2016-01-01

    Summary 1. Wildfires are the principal disturbance in the boreal forest, and their size and frequency are increasing as the climate warms. Impacts of fires on boreal wildlife are largely unknown, especially for the tens of millions of waterfowl that breed in the region. This knowledge gap creates significant barriers to the integrative management of fires and waterfowl, leading to fire policies that largely disregard waterfowl. 2. Waterfowl populations across the western boreal forest of North America have been monitored annually since 1955 by the Waterfowl Breeding Population and Habitat Survey (BPOP), widely considered the most extensive wildlife survey in the world. Using these data, we examined impacts of forest fires on abundance of two waterfowl guilds – dabblers and divers. We modelled waterfowl abundance in relation to fire extent (i.e. amount of survey transect burned) and time since fire, examining both immediate and lagged fire impacts. 3. From 1955 to 2014, >1100 fires in the western boreal forest intersected BPOP survey transects, and many transects burned multiple times. Nonetheless, fires had no detectable impact on waterfowl abundance; annual transect counts of dabbler and diver pairs remained stable from the pre- to post-fire period. 4. The absence of fire impacts on waterfowl abundance extended from the years immediately following the fire to those more than a decade afterwards. Likewise, the amount of transect burned did not influence waterfowl abundance, with similar pair counts from the pre- to post-fire period for small (1–20% burned), medium (21–60%) and large (>60%) burns. 5. Policy implications. Waterfowl populations appear largely resilient to forest fires, providing initial evidence that current policies of limited fire suppression, which predominate throughout much of the boreal forest, have not been detrimental to waterfowl populations. Likewise, fire-related management actions, such as prescribed burning or targeted suppression

  8. 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

    Global warming and climate change will significantly affect on forest environment in northern latitudes. There is the strong evidence that increase of early spring and late autumn temperatures will have impacts on growth and growth cycles. In Finland the Finnish Forest Research Institute (Luke since 2015) established in 1996 National Phenological Network to study changes of phenophases all over the country representing southern, middle and northern boreal forest zones. Continuous detailed scientific monitoring includes eleven forest plant species and it forms an excellent basis to evaluate responses of forest vegetation in respect to climate change. Monitoring is done together with Universities and other Institutes. Prior to the establishment of the Finnish National Phenological Network observations has been made solely based on volunteers since 1752. This citizen-science data is very important to analyze phenophases together with the results of the National Network. The long-term data since 1752 shows e.g. an advancement in the onset of Prunus padus flowering by five days per 100 years and correspondingly three days in the rowan (Sorbus aucuparia). The latest results of the Finnish National Network (1996 - 2014) fits well to this long term trend. In the Finnish National Phenological Network we have monitored phenophases of forest spieces throughout the growth period, focusing on nine forest tree species and two dwarf shrubs. The results can be followed in real time at: http://www.metla.fi/metinfo/fenologia/index-en.htm. We have observed big differences in phenophases between southern and northern boreal zone. Onset of downy birch leafing happens one month later in the north compared with southern boreal zone. Coming into leaf has clearly occurred earlier during the research period since 1996 in the northern boreal zone compared with southern boreal zone. This indicates the response of climate change. The timing of leaf colouring and leaf fall was observed remained

  9. 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

  10. 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

    forested peatlands might be counterproductive as it promotes fire vulnerability even in cold boreal regions.

  11. The accuracy of large-area forest canopy cover estimation using Landsat in boreal region

    Science.gov (United States)

    Hadi; Korhonen, Lauri; Hovi, Aarne; Rönnholm, Petri; Rautiainen, Miina

    2016-12-01

    Large area prediction of continuous field of tree cover i.e., canopy cover (CC) using Earth observation data is of high interest in practical forestry, ecology, and climate change mitigation activities. We report the accuracy of using Landsat images for CC prediction in boreal forests validated with field reference plots (N = 250) covering large variation in latitude, forest structure, species composition, and site type. We tested two statistical models suitable for estimating CC: the beta regression (BetaReg) and random forest (RanFor). Landsat-based predictors utilized include individual bands, spectral vegetation indices (SVI), and Tasseled cap (Tass) features. Additionally, we tested an alternative model based on spectral mixture analysis (SMA). Finally, we carried out a first validation in boreal forests of the recently published Landsat Tree Cover Continuous (TCC) global product. Results showed simple BetaReg with red band reflectance provided the highest prediction accuracy (leave-site-out RMSECV 13.7%; R2CV 0.59; biasCV 0.5%). Spectral transformations into SVI and Tass did not improve accuracy. Including additional predictors did not significantly improve accuracy either. Nonlinear model RanFor did not outperform BetaReg. The alternative SMA model did not outperform the empirical models. However, empirical models cannot resolve the underestimation of high cover and overestimation of low cover. SMA prediction errors appeared less dependent on forest structure, while there seemed to be a potential for improvement by accounting for endmember variability of different tree species. Finally, using temporally concurrent observations, we showed the reasonably good accuracy of Landsat TCC product in boreal forests (RMSE 13.0%; R2 0.53; bias -2.1%), however with a tendency to underestimate high cover.

  12. Responses of fungal and plant communities to partial humus removal in mid-boreal N-enriched forests.

    Science.gov (United States)

    Tarvainen, Oili; Hamberg, Leena; Ohenoja, Esteri; Strömmer, Rauni; Markkola, Annamari

    2012-10-15

    Partial removal of the forest humus layer was performed in nitrogen-enriched urban Scots pine forest stands in the northern Finland in order to improve soil conditions for ectomycorrhizal (ECM) fungi, important symbionts of trees. Aboveground part of understory vegetation and the uppermost half of the humus layer were removed (REMOVAL treatment) from sample plots in six urban and eight rural reference forest sites at the beginning of the 2001 growing season. During the seasons 2001-2005, we inventoried sporocarp production of ECM and saprophytic fungi, and in 2003 the recovery of understory vegetation. The REMOVAL treatment resulted in a higher number of fruiting ECM species and sporocarps than controls at the rural, but not at urban sites. The sporocarp number of saprophytic fungi declined in the REMOVAL subplots at the urban sites. The recovery of bryophytes and lichens in the REMOVAL treatment was slow at both the urban and rural sites, whereas Vaccinium dwarf shrub cover, and herb and grass cover returned rapidly at the urban sites. We conclude that the partial vegetation and humus layer removal as a tool to promote the reproduction of ECM fungal species is limited in the boreal urban forests.

  13. Seasonal and inter annual variability of energy exchange above a boreal Scots pine forest

    Directory of Open Access Journals (Sweden)

    S. Launiainen

    2010-08-01

    Full Text Available Twelve-years of eddy-covariance measurements conducted above a boreal Scots pine forest in Hyytiälä, Southern Finland, were analyzed to assess the seasonal and inter-annual variability of surface conductance (gs and energy partitioning. The gs had distinct annual course, driven by the seasonal cycle of the Scots pine. Low gs (2–3 mm s−1 in April restricted transpiration in springtime and caused the sensible heat flux to peak in May–June while evapotranspiration takes over later in July–August when gs is typically 5–7 mm s−1. Hence, during normal years Bowen ratio decreases from 4–6 in April to 0.7–0.9 in August. Sensitivity of gs to ambient vapor pressure deficit (D was relatively constant but the reference value at D=1 kPa varied seasonally and between years. Only two drought episodes when volumetric soil moisture content in upper mineral soil decreased below 0.15 m3 m−3 occurred during the period. Below this threshold value transpiration was strongly reduced, which promoted sensible heat exchange increasing Bowen ratio to 3–4. Annual evapotranspiration varied between 218 and 361 mm and accounted between 50% and 90% of equilibrium evaporation. The forest floor contributed between 16 and 25% of the total evapotranspiration on annual scale. The fraction stayed similar over the observed range of environmental conditions including drought. The inter-annual variability of evapotranspiration could not be linked to any mean climate parameter while the summertime sensible heat flux and net radiation were well explained by global radiation. The energy balance closure varied annually between 0.66 and 0.95 and had a distinct seasonal cycle with worse closure in spring when large proportion of available energy is partitioned into sensible heat.

  14. Seasonal and inter-annual variability of energy exchange above a boreal Scots pine forest

    Directory of Open Access Journals (Sweden)

    S. Launiainen

    2010-12-01

    Full Text Available Twelve-years of eddy-covariance measurements conducted above a boreal Scots pine forest in Hyytiälä, Southern Finland, were analyzed to assess the seasonal and inter-annual variability of surface conductance (gs and energy partitioning. The gs had distinct annual course, driven by the seasonal cycle of the Scots pine. Low gs (2–3 mm s−1 in April cause the sensible heat flux to peak in May–June while evapotranspiration takes over later in July–August when gs is typically 5–7 mm s−1. Hence, during normal years Bowen ratio decreases from 4–6 in April to 0.7–0.9 in August. Sensitivity of gs to ambient vapor pressure deficit (D was relatively constant but the reference value at D = 1 kPa varied seasonally and between years. Only two drought episodes when volumetric soil moisture content in upper mineral soil decreased below 0.15 m3 m−3 occurred during the period. Below this threshold value, transpiration was strongly reduced, which promoted sensible heat exchange increasing Bowen ratio to 3–4. Annual evapotranspiration varied between 218 and 361 mm and accounted between 50% and 90% of equilibrium evaporation. The forest floor contributed between 16 and 25% of the total evapotranspiration on annual scale. The fraction stayed similar over the observed range of environmental conditions including drought periods. The inter-annual variability of evapotranspiration could not be linked to any mean climate variable while the summertime sensible heat flux and net radiation were well explained by global radiation. The energy balance closure varied annually between 0.66 and 0.95 and had a distinct seasonal cycle with worse closure in spring when a large proportion of available energy is partitioned into sensible heat.

  15. Rating a Wildfire Mitigation Strategy with an Insurance Premium: A Boreal Forest Case Study

    Directory of Open Access Journals (Sweden)

    Georgina Rodriguez-Baca

    2016-05-01

    Full Text Available Risk analysis entails the systematic use of historical information to determine the frequency, magnitude and effects of unexpected events. Wildfire in boreal North America is a key driver of forest dynamics and may cause very significant economic losses. An actuarial approach to risk analysis based on cumulative probability distributions was developed to reduce the adverse effects of wildfire. To this effect, we developed spatially explicit landscape models to simulate the interactions between harvest, fire and forest succession over time in a boreal forest of eastern Canada. We estimated the amount of reduction of timber harvest necessary to build a buffer stock of sufficient size to cover fire losses and compared it to an insurance premium estimated in units of timber volume from the probability of occurrence and the amount of damage. Overall, the timber harvest reduction we applied was much more costly than the insurance premium even with a zero interest rate. This is due to the fact that the insurance premium is directly related to risk while the timber harvest reduction is not and, as a consequence, is much less efficient. These results, especially the comparison with a standard indicator such as an insurance premium, have useful implications at the time of choosing a mitigation strategy to protect timber supplies against risk without overly diminishing the provision of services from the forest. They are also promoting the use of insurance against disastrous events in forest management planning.

  16. 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

  17. Maintaining animal assemblages through single-species management: the case of threatened caribou in boreal forest.

    Science.gov (United States)

    Bichet, Orphé; Dupuch, Angélique; Hébert, Christian; Le Borgne, Hélène Le; Fortin, Daniel

    2016-03-01

    With the intensification of human activities, preserving animal populations is a contemporary challenge of critical importance. In this context, the umbrella species concept is appealing because preserving a single species should result in the protection of multiple co-occurring species. Practitioners, though, face the task of having to find suitable umbrellas to develop single-species management guidelines. In North America, boreal forests must be managed to facilitate the recovery of the threatened boreal caribou (Rangifer tarandus). Yet, the effect of caribou conservation on co-occurring animal species remains poorly documented. We tested if boreal caribou can constitute an effective umbrella for boreal fauna. Birds, small mammals, and insects were sampled along gradients of post-harvest and post-fire forest succession. Predictive models of occupancy were developed from the responses of 95 species to characteristics of forest stands and their surroundings. We then assessed the similarity of species occupancy expected between simulated harvested landscapes and a 90 000-km2 uncut landscape. Managed landscapes were simulated based on three levels of disturbance, two timber-harvest rotation cycles, and dispersed or aggregated cut-blocks. We found that management guidelines that were more likely to maintain caribou populations should also better preserve animal assemblages. Relative to fragmentation or harvest cycle, we detected a stronger effect of habitat loss on species assemblages. Disturbing 22%, 35%, and 45% of the landscape should result, respectively, in 80%, 60%, and 40% probability for caribou populations to be sustainable; in turn, this should result in regional species assemblages with Jaccard similarity indices of 0.86, 0.79, and 0.74, respectively, relative to the uncut landscape. Our study thus demonstrates the value of single-species management for animal conservation. Our quantitative approach allows for the evaluation of management guidelines prior

  18. 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.

  19. 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

  20. 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...

  1. 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. PMID:23785359

  2. 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.

  3. 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.

  4. 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

  5. Fire Regime along Latitudinal Gradients of Continuous to Discontinuous Coniferous Boreal Forests in Eastern Canada

    Directory of Open Access Journals (Sweden)

    Jeanne Portier

    2016-09-01

    Full Text Available Fire is the main disturbance in North American coniferous boreal forests. In Northern Quebec, Canada, where forest management is not allowed, the landscape is gradually constituted of more opened lichen woodlands. Those forests are discontinuous and show a low regeneration potential resulting from the cumulative effects of harsh climatic conditions and very short fire intervals. In a climate change context, and because the forest industry is interested in opening new territories to forest management in the north, it is crucial to better understand how and why fire risk varies from the north to the south at the transition between the discontinuous and continuous boreal forest. We used time-since-fire (TSF data from fire archives as well as a broad field campaign in Quebec’s coniferous boreal forests along four north-south transects in order to reconstruct the fire history of the past 150 to 300 years. We performed survival analyses in each transect in order to (1 determine if climate influences the fire risk along the latitudinal gradient; (2 fractionate the transects into different fire risk zones; and (3 quantify the fire cycle—defined as the time required to burn an area equivalent to the size of the study area—of each zone and compare its estimated value with current fire activity. Results suggest that drought conditions are moderately to highly responsible for the increasing fire risk from south to north in the three westernmost transects. No climate influence was observed in the last one, possibly because of its complex physical environment. Fire cycles are shortening from south to north, and from east to west. Limits between high and low fire risk zones are consistent with the limit between discontinuous and continuous forests, established based on recent fire activity. Compared to the last 40 years, fire cycles of the last 150–300 years are shorter. Our results suggest that as drought episodes are expected to become more frequent

  6. Variation in moss-associated nitrogen fixation in boreal forest stands.

    Science.gov (United States)

    Markham, John H

    2009-08-01

    Traditionally it has been thought that most boreal forest communities lack a significant input of biologically fixed nitrogen. Recent discoveries of nitrogen fixation by cyanobacteria associated with mosses have resulted in a re-evaluation of this view. While it is recognized that rates of nitrogen fixation in mosses can be highly variable, there is little understanding as to why this occurs. I monitored nitrogen fixation, using acetylene reduction, in wet lowland and dry upland boreal forest communities, in central Canada, over a growing season. At the peak of nitrogen fixation in mid summer, Sphagnum capillifolium had an 11 times higher rate of fixation than Pleurozium schreberi. Variation in canopy openness and precipitation had no effect on rates of fixation over the growing season. In P. schreberi fixation rates did not vary between sites. Temperature had a positive effect on fixation rates in both S. capillifolium and P. schreberi, but the effect was 4 times more pronounced in S. capillifolium. Seasonal rates of nitrogen fixation were estimated at 193 mg N m(-2) for S. capillifolium and 23 mg N m(-2) for P. schreberi. With moderate increases in climate warming, predicted increases in nitrogen fixation in S. capillifolium are sufficient to raise its decomposition rate. Increased temperatures may therefore act synergistically to change boreal systems from a sink to a source of carbon.

  7. Wintertime photosynthetic capacity of black spruce (Picea mariana) in boreal forests in interior Alaska

    Science.gov (United States)

    Fujino, T.; Koyama, L. A.; Kielland, K.

    2015-12-01

    In boreal forests, the growing season is short, and winter temperature is low and fluctuates from considerably below freezing point to intermittent warm spells. Under such conditions, it is important for plants to retain their photosynthetic capacity throughout the winter. To understand the importance of wintertime photosynthetic activity for evergreen boreal coniferous species, the light response curve of black spruce (Picea mariana) was monitored in Fairbanks, interior Alaska (64°86'N, 147°84'W) throughout the winter, and compared with those in the summer. Cuttings of black spruce were collected, and gas exchange of their needles was measured in the incubator set to 0 °C using a gas analyzer (LI-6400, Li-Cor Inc.). A non-rectangular hyperbolic model was fitted to these data, and physiological parameters such as the maximum photosynthesis rate, dark respiration rate and quantum yield of photosynthesis were extracted. The apparent quantum yield of photosynthesis remained low throughout the winter for black spruce. The maximum photosynthesis rate was downregulated as air temperature fell in early winter, but did not increase in March when air temperature rose. This suggests that photoinhibition may occur more strongly in March than in early winter. The average maximum rates of photosynthesis in winter were almost 10% of the value measured in summer. On the other hand, the dark respiration rate did not considerably differ between seasons. These results provide new insights into winter photosynthetic activity and its role in boreal forest ecosystems.

  8. 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

  9. 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

  10. Carbon isotope labeling in boreal forests to assess roles of fungal species in decomposition

    Science.gov (United States)

    Treseder, K. K.; Czimczik, C. I.; Trumbore, S. E.; Allison, S. D.

    2006-12-01

    We used 14C and 13C labeling to assess the in situ respiration of alanine-, starch-, and lignocellulose-derived carbon from the sporocarps of particular fungal species fruiting in a boreal forest in Alaska. By measuring isotopically-labeled respiration of sporocarps, which can be identified to species, we were able to attribute turnover of carbon compounds to specific fungal groups. Moreover, collection of sporocarp respiration is non-destructive, so we could return to the same sporocarps to collect a time series of measurements that spanned hours to days. We tested the hypotheses that alanine and starch turn over more quickly than lignocellulose, and that saprotrophic fungi would use starch-C and lignocellulose-C but ectomycorrhizal fungi would not. Small amounts of 14C-labeled alanine (about 100,000 permil) were dispensed into the soil within three meters of sporocarps of the ectomycorrhizal fungus Lactarius alnicola. Δ14CO2 values of sporocarp respiration climbed from 75.8 +/- 6.3 permil to 7855 +/- 3940 permil within one hour of additions, indicating that the fungus quickly acquired, transported, and transformed the alanine-C. In a separate approach, a mixture of 13C-labeled starch (about 15,000 permil) and 14C-labeled lignocellulose (about 36,000 permil) was applied in 9 m2 plots containing sporocarps of the ectomycorrhizal genera Phellodon and Sarcodon and the saprotrophic genera Lycoperdon and Polyporus. An unlabeled control plot was also established. We observed no detectable increase in 14CO2 or 13CO2 over a 144 hour period, suggesting that neither ectomycorrhizal nor saprotrophic fungi significantly broke down starch or lignocellulose during this time. The alanine experiment is one of the first to indicate that ectomycorrhizal fungi can influence the spatial distribution and storage of soil carbon over short time scales. This influence may be restricted to carbon of organic compounds like amino acids. In contrast, starch was not transformed quickly even

  11. Changes in very fine root respiration and morphology with time since last fire in a boreal forest

    Science.gov (United States)

    Makita, Naoki; Pumpanen, Jukka; Köster, Kajar; Berninger, Frank

    2016-04-01

    We examined the physiological and morphological responses of individual fine root segments in boreal forests stands with different age since the last fire to determine changes in specific fine root respiration and morphological traits during forest succession. We investigated the respiration of fine roots divided into three diameter classes (geographic area, we suggest that the recovery of boreal forests following wildfire induces a strategy that favors carbon investment in nutrient and water exploitation efficiency with consequences for higher respiration, length, and lower tissue density of very fine roots.

  12. Winter soil CO2 efflux in two contrasting forest ecosystems on the eastern Tibetan Plateau, China

    Institute of Scientific and Technical Information of China (English)

    Zhenfeng Xu; Feifei Zhou; Huajun Yin; Qing Liu

    2015-01-01

    Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and estimated annual soil respiration in two contrasting coniferous forest ecosystems (a Picea asperata plantation and a natural forest). Mean winter soil CO2 effluxes were 1.08 lmol m-2 s-1 in the plantation and 1.16 lmol m-2 s-1 in the natural forest. These values are higher than most reported winter soil CO2 efflux values for temperate or boreal forest ecosystems. Winter soil respiration rates were similar for our two forest ecosystems but mean soil CO2 efflux over the growing season was higher in the natural forest than in the plantation. The estimated winter and annual soil effluxes for the natural forest were 176.3 and 1070.3 g m-2, respectively, based on the relationship between soil respiration and soil temperature, which were 17.2 and 9.7 % greater than their counterparts in the plantation. The contributions of winter soil respiration to annual soil efflux were 15.4 % for the plantation and 16.5 % for the natural forest and were statistically similar. Our results indicate that winter soil CO2 efflux from frozen soils in the alpine coniferous forest ecosystems of the eastern Tibetan Plateau was considerable and was an important component of annual soil respiration. Moreover, reforestation (natural coniferous forests were deforested and reforested with P. asperata plantation) may reduce soil respiration by reducing soil carbon substrate availability and input.

  13. Alaska’s changing fire regime - Implications for the vulnerability of its boreal forests

    Science.gov (United States)

    Kasischke, Eric S.; Verbyla, David L.; Rupp, T. Scott; McGuire, Anthony; Murphy, Karen A.; Jandt, R.; Barnes, Jennifer L.; Hoy, E.; Duffy, Paul A; Calef, Monika; Turetsky, Merritt R.

    2010-01-01

    A synthesis was carried out to examine Alaska’s boreal forest fire regime. During the 2000s, an average of 767 000 ha·year–1 burned, 50% higher than in any previous decade since the 1940s. Over the past 60 years, there was a decrease in the number of lightning-ignited fires, an increase in extreme lightning-ignited fire events, an increase in human-ignited fires, and a decrease in the number of extreme human-ignited fire events. The fraction of area burned from human-ignited fires fell from 26% for the 1950s and 1960s to 5% for the 1990s and 2000s, a result from the change in fire policy that gave the highest suppression priorities to fire events that occurred near human settlements. The amount of area burned during late-season fires increased over the past two decades. Deeper burning of surface organic layers in black spruce (Picea mariana (Mill.) BSP) forests occurred during late-growing-season fires and on more well-drained sites. These trends all point to black spruce forests becoming increasingly vulnerable to the combined changes of key characteristics of Alaska’s fire regime, except on poorly drained sites, which are resistant to deep burning. The implications of these fire regime changes to the vulnerability and resilience of Alaska’s boreal forests and land and fire management are discussed.

  14. Alaska's Changing Fire Regime - Implications for the Vulnerability of Its Boreal Forests

    Science.gov (United States)

    Kasischke, E. S.; Hoy, E. E.; Verbyla, D. L.; Rupp, T. S.; Duffy, P. A.; McGuire, A. D.; Murphy, K. A.; Jandt, R.; Barnes, J. L.; Calef, M.; hide

    2010-01-01

    A synthesis was carried out to examine Alaska s boreal forest fire regime. During the 2000s, an average of 767 000 ha/year burned, 50% higher than in any previous decade since the 1940s. Over the past 60 years, there was a decrease in the number of lightning-ignited fires, an increase in extreme lightning-ignited fire events, an increase in human-ignited fires, and a decrease in the number of extreme human-ignited fire events. The fraction of area burned from humanignited fires fell from 26% for the 1950s and 1960s to 5% for the 1990s and 2000s, a result from the change in fire policy that gave the highest suppression priorities to fire events that occurred near human settlements. The amount of area burned during late-season fires increased over the past two decades. Deeper burning of surface organic layers in black spruce (Picea mariana (Mill.) BSP) forests occurred during late-growing-season fires and on more well-drained sites. These trends all point to black spruce forests becoming increasingly vulnerable to the combined changes of key characteristics of Alaska s fire regime, except on poorly drained sites, which are resistant to deep burning. The implications of these fire regime changes to the vulnerability and resilience of Alaska s boreal forests and land and fire management are discussed.

  15. 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).

  16. Vegetation Mortality within Natural Wildfire Events in the Western Canadian Boreal Forest: What Burns and Why?

    Directory of Open Access Journals (Sweden)

    Colin J. Ferster

    2016-08-01

    Full Text Available Wildfires are a common disturbance event in the Canadian boreal forest. Within event boundaries, the level of vegetation mortality varies greatly. Understanding where surviving vegetation occurs within fire events and how this relates to pre-fire vegetation, topography, and fire weather can inform forest management decisions. We used pre-fire forest inventory data, digital elevation maps, and records of fire weather for 37 naturally-occurring wildfires (1961 to 1982; 30 to 5500 ha covering a wide range of conditions in the western Canadian boreal forest to investigate these relationships using multinomial logistic models. Overall, vegetation mortality related to a combination of factors representing different spatial scales. Lower vegetation mortality occurred where there was lower fuel continuity and when fires occurred under non-drought conditions. Higher classification accuracy occurred for class extremes of no mortality (i.e., unburned areas within the burn event and high mortality; partial vegetation mortality classes were harder to distinguish. This research contributes to the knowledge required for natural pattern emulation strategies, and developing responses to climate change.

  17. Stable carbon isotope analysis reveals widespread drought stress in boreal black spruce forests.

    Science.gov (United States)

    Walker, Xanthe J; Mack, Michelle C; Johnstone, Jill F

    2015-08-01

    Unprecedented rates of climate warming over the past century have resulted in increased forest stress and mortality worldwide. Decreased tree growth in association with increasing temperatures is generally accepted as a signal of temperature-induced drought stress. However, variations in tree growth alone do not reveal the physiological mechanisms behind recent changes in tree growth. Examining stable carbon isotope composition of tree rings in addition to tree growth can provide a secondary line of evidence for physiological drought stress. In this study, we examined patterns of black spruce growth and carbon isotopic composition in tree rings in response to climate warming and drying in the boreal forest of interior Alaska. We examined trees at three nested scales: landscape, toposequence, and a subsample of trees within the toposequence. At each scale, we studied the potential effects of differences in microclimate and moisture availability by sampling on northern and southern aspects. We found that black spruce radial growth responded negatively to monthly metrics of temperature at all examined scales, and we examined ∆(13)C responses on a subsample of trees as representative of the wider region. The negative ∆(13)C responses to temperature reveal that black spruce trees are experiencing moisture stress on both northern and southern aspects. Contrary to our expectations, ∆(13)C from trees on the northern aspect exhibited the strongest drought signal. Our results highlight the prominence of drought stress in the boreal forest of interior Alaska. We conclude that if temperatures continue to warm, we can expect drought-induced productivity declines across large regions of the boreal forest, even for trees located in cool and moist landscape positions. © 2015 John Wiley & Sons Ltd.

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

    Science.gov (United States)

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

    2014-01-01

    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 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.

  20. 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.

  1. Enzyme activity and microorganisms diversity in soil contaminated with the Boreal 58 WG herbicide.

    Science.gov (United States)

    Kucharski, Jan; Tomkiel, Monika; Baćmaga, Małgorzata; Borowik, Agata; Wyszkowska, Jadwiga

    2016-07-02

    Next-generation herbicides are relatively safe when used properly, but the recommended rates are relatively low, which can lead to overdosing. This study evaluated the responses of soil-dwelling microorganisms and soil enzymes to contamination with the Boreal 58 WG herbicide. The analyzed product contains active ingredients flufenacet and isoxaflutole. All tests were performed under laboratory conditions. The analyzed material was sandy clay. Boreal 58 WG was introduced to soil in four doses. Soil without the addition of the herbicide served as the control. The soil was mixed with the tested herbicide, and its moisture content was maintained at 50% of capillary water capacity. Biochemical and microbiological analyses were performed on experimental days 0, 20, 40, 80 and 160. Accidental contamination of soil with the Boreal 58 WG herbicide led to a relatively minor imbalance in the soil microbiological and biochemical profile. The herbicide dose influenced dehydrogenase activity in only 0.84%, urease activity in 2.04%, β-glucosidase activity in 8.26%, catalase activity in 12.40%, arylsulfatase activity in 12.54%, acid phosphatase activity in 42.11%, numbers of organotrophic bacteria in 18.29%, actinomyces counts in 1.31% and fungi counts in 6.86%.

  2. The role of novel forest ecosystems in the conservation of wood-inhabiting fungi in boreal broadleaved forests.

    Science.gov (United States)

    Juutilainen, Katja; Mönkkönen, Mikko; Kotiranta, Heikki; Halme, Panu

    2016-10-01

    The increasing human impact on the earth's biosphere is inflicting changes at all spatial scales. As well as deterioration and fragmentation of natural biological systems, these changes also led to other, unprecedented effects and emergence of novel habitats. In boreal zone, intensive forest management has negatively impacted a multitude of deadwood-associated species. This is especially alarming given the important role wood-inhabiting fungi have in the natural decay processes. In the boreal zone, natural broad-leaved-dominated, herb-rich forests are threatened habitats which have high wood-inhabiting fungal species richness. Fungal diversity in other broadleaved forest habitat types is poorly known. Traditional wood pastures and man-made afforested fields are novel habitats that could potentially be important for wood-inhabiting fungi. This study compares species richness and fungal community composition across the aforementioned habitat types, based on data collected for wood-inhabiting fungi occupying all deadwood diameter fractions. Corticioid and polyporoid fungi were surveyed from 67 130 deadwood particles in four natural herb-rich forests, four birch-dominated wood pastures, and four birch-dominated afforested field sites in central Finland. As predicted, natural herb-rich forests were the most species-rich habitat. However, afforested fields also had considerably higher overall species richness than wood pastures. Many rare or rarely collected species were detected in each forest type. Finally, fungal community composition showed some divergence not only among the different habitat types, but also among deadwood diameter fractions. Synthesis and applications: In order to maintain biodiversity at both local and regional scales, conserving threatened natural habitat types and managing traditional landscapes is essential. Man-made secondary woody habitats could provide the necessary resources and serve as surrogate habitats for many broadleaved deadwood

  3. Quantifying the missing link between albedo and productivity of boreal forests

    Science.gov (United States)

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

    2016-04-01

    Albedo and fraction of absorbed photosynthetically active radiation (FAPAR) determine the shortwave radiation balance and productivity of forests. Several studies have examined the relation between forest structure and albedo in the boreal zone. Studies regarding FAPAR are fewer and the relations between albedo and FAPAR are still poorly understood. To study these relations we simulated shortwave black sky albedo and canopy FAPAR, using the FRT forest reflectance model. We used two sets of field plots as input data. The plots were located in Alaska, USA (N = 584) and in Finland (N = 506) between Northern latitudes of 60° and 68° , and they represent naturally grown and more intensively managed (regularly thinned) forests, respectively. The simulations were carried out with sun zenith angles (SZA) typical to the biome, ranging from 40° to 80° . The simulated albedos in coniferous plots decreased with increasing tree height, whereas canopy FAPAR showed an opposite trend. The albedo of broadleaved plots was notably higher than that of coniferous plots. No species differences in canopy FAPAR were seen, except for pine forests in Finland that showed lowest FAPAR among species. Albedo and canopy FAPAR were negatively correlated (r ranged from -0.93 to -0.69) in coniferous plots. The correlations were notably weaker (r ranged from -0.64 to 0.05) if plots with broadleaved trees were included. To show the influence of forest management, we further examined the response of albedo and FAPAR to forest density (basal area) and fraction of broadleaved trees. Plots with low basal area showed high albedos but also low canopy FAPAR. When comparing the sparse plots to dense ones, the relative decrease in canopy FAPAR was larger than the relative increase in albedo. However, at large SZAs the basal area could be lowered to approx. 20 m2 ha-1 before FAPAR was notably reduced. Increasing the proportion of broadleaved trees from 0% to 100% increased the albedos to approximately

  4. Terrestrial laser scanning and pin meter measurements for erosion and roughness assessment in boreal peatland forest ditches

    Science.gov (United States)

    Stenberg, Leena; Tuukkanen, Tapio; Finér, Leena; Marttila, Hannu; Piirainen, Sirpa; Kløve, Bjørn; Koivusalo, Harri

    2016-04-01

    Drainage and the maintenance of drainage ditches in peatland forests increase erosion and sediment load reducing water quality downstream. The understanding of the sediment source area processes requires reliable methods for topographical change detection in the peatland forest ditches. The objective of this study was to quantify erosion and changes in surface roughness with two different methods: terrestrial laser scanning (TLS) and manual pin meter measurements. Two newly cleaned boreal peatland forest ditches were studied, one peat ditch and one with exposed till soil under the thin peat layer. The topographies of a 4-meter-long section of the ditches were measured sequentially during the 11-20 months study period. In the ditch with thin peat layer, erosion estimates were quite similar with both methods. However, in the peat ditch the erosion measured with the pin meter considerably exceeded the results provided by TLS. Surface roughness indicated by the TLS data was greater than the surface roughness calculated from the pin meter data. According to both methods, surface roughness increased more at the ditch with thin peat layer. Both methods could be adopted to measure erosion and surface roughness in peatland forest conditions. However, the methods had difficulties to distinguish the bed of the peat ditch. TLS encountered problems to detect dark peat soil bed under shallow layer of humic ditch water resulting in no-data areas at the bed of the ditch. Pin meter device was able to measure under the water but the soft peat bed increased the uncertainty of the measurements.

  5. Impact of fire on active layer and permafrost microbial communities and metagenomes in an upland Alaskan boreal forest.

    Science.gov (United States)

    Taş, Neslihan; Prestat, Emmanuel; McFarland, Jack W; Wickland, Kimberley P; Knight, Rob; Berhe, Asmeret Asefaw; Jorgenson, Torre; Waldrop, Mark P; Jansson, Janet K

    2014-09-01

    Permafrost soils are large reservoirs of potentially labile carbon (C). Understanding the dynamics of C release from these soils requires us to account for the impact of wildfires, which are increasing in frequency as the climate changes. Boreal wildfires contribute to global emission of greenhouse gases (GHG-CO2, CH4 and N2O) and indirectly result in the thawing of near-surface permafrost. In this study, we aimed to define the impact of fire on soil microbial communities and metabolic potential for GHG fluxes in samples collected up to 1 m depth from an upland black spruce forest near Nome Creek, Alaska. We measured geochemistry, GHG fluxes, potential soil enzyme activities and microbial community structure via 16SrRNA gene and metagenome sequencing. We found that soil moisture, C content and the potential for respiration were reduced by fire, as were microbial community diversity and metabolic potential. There were shifts in dominance of several microbial community members, including a higher abundance of candidate phylum AD3 after fire. The metagenome data showed that fire had a pervasive impact on genes involved in carbohydrate metabolism, methanogenesis and the nitrogen cycle. Although fire resulted in an immediate release of CO2 from surface soils, our results suggest that the potential for emission of GHG was ultimately reduced at all soil depths over the longer term. Because of the size of the permafrost C reservoir, these results are crucial for understanding whether fire produces a positive or negative feedback loop contributing to the global C cycle.

  6. Nematode community shifts in response to experimental warming and canopy conditions are associated with plant community changes in the temperate-boreal forest ecotone.

    Science.gov (United States)

    Thakur, Madhav Prakash; Reich, Peter B; Fisichelli, Nicholas A; Stefanski, Artur; Cesarz, Simone; Dobies, Tomasz; Rich, Roy L; Hobbie, Sarah E; Eisenhauer, Nico

    2014-06-01

    Global climate warming is one of the key forces driving plant community shifts, such as range shifts of temperate species into boreal forests. As plant community shifts are slow to observe, ecotones, boundaries between two ecosystems, are target areas for providing early evidence of ecological responses to warming. The role of soil fauna is poorly explored in ecotones, although their positive and negative effects on plant species can influence plant community structure. We studied nematode communities in response to experimental warming (ambient, +1.7, +3.4 °C) in soils of closed and open canopy forest in the temperate-boreal ecotone of Minnesota, USA and calculated various established nematode indices. We estimated species-specific coverage of understory herbaceous and shrub plant species from the same experimental plots and tested if changes in the nematode community are associated with plant cover and composition. Individual nematode trophic groups did not differ among warming treatments, but the ratio between microbial-feeding and plant-feeding nematodes increased significantly and consistently with warming in both closed and open canopy areas and at both experimental field sites. The increase in this ratio was positively correlated with total cover of understory plant species, perhaps due to increased predation pressure on soil microorganisms causing higher nutrient availability for plants. Multivariate analyses revealed that temperature treatment, canopy conditions and nematode density consistently shaped understory plant communities across experimental sites. Our findings suggest that warming-induced changes in nematode community structure are associated with shifts in plant community composition and productivity in the temperate-boreal forest ecotones.

  7. The importance of phenology for the evaluation of impact of climate change on growth of boreal, temperate and Mediterranean forests [sic] ecosystems: an overview

    NARCIS (Netherlands)

    Kramer, K.; Leinonen, I.; Loustau, D.

    2000-01-01

    An overview is presented of the phenological models relevant for boreal coniferous, temperate-zone deciduous and Mediterranean coniferous forest ecosystems. The phenology of the boreal forests is mainly driven by temperature, affecting the timing of the start of the growing season and thereby its

  8. Charcoal reflectance reveals early holocene boreal deciduous forests burned at high intensities.

    Science.gov (United States)

    Hudspith, Victoria A; Belcher, Claire M; Kelly, Ryan; Hu, Feng Sheng

    2015-01-01

    Wildfire size, frequency, and severity are increasing in the Alaskan boreal forest in response to climate warming. One of the potential impacts of this changing fire regime is the alteration of successional trajectories, from black spruce to mixed stands dominated by aspen, a vegetation composition not experienced since the early Holocene. Such changes in vegetation composition may consequently alter the intensity of fires, influencing fire feedbacks to the ecosystem. Paleorecords document past wildfire-vegetation dynamics and as such, are imperative for our understanding of how these ecosystems will respond to future climate warming. For the first time, we have used reflectance measurements of macroscopic charcoal particles (>180μm) from an Alaskan lake-sediment record to estimate ancient charring temperatures (termed pyrolysis intensity). We demonstrate that pyrolysis intensity increased markedly from an interval of birch tundra 11 ky ago (mean 1.52%Ro; 485°C), to the expansion of trees on the landscape ~10.5 ky ago, remaining high to the present (mean 3.54%Ro; 640°C) irrespective of stand composition. Despite differing flammabilities and adaptations to fire, the highest pyrolysis intensities derive from two intervals with distinct vegetation compositions. 1) the expansion of mixed aspen and spruce woodland at 10 cal. kyr BP, and 2) the establishment of black spruce, and the modern boreal forest at 4 cal. kyr BP. Based on our analysis, we infer that predicted expansion of deciduous trees into the boreal forest in the future could lead to high intensity, but low severity fires, potentially moderating future climate-fire feedbacks.

  9. Response of female beetles to LIDAR derived topographic variables in Eastern boreal mixedwood forests (Coleoptera, Carabidae).

    Science.gov (United States)

    Work, Timothy T; Onge, Benoit St; Jacobs, J M

    2011-01-01

    Biodiversity monitoring is increasingly being bolstered with high resolution data derived from remote sensing such as LIDAR (Light Detection and Ranging). We derived a series of topographical variables, including slope, azimuth, ground curvature and flow accumulation from LIDAR images and compared these to captures of female carabids in pitfall traps in Eastern boreal mixedwood forests. We developed a series of species-specific logistic models predicting the proportion of females for eight dominant species, including Agonum retractum, Calathus ingratus, Platynus decentis, Pterostichus adstrictus, Pterostichus coracinus, Pterostichus pensylvanicus, Sphaeroderus nitidicollis and Synuchus impunctatus. We used these models to test three hypotheses related to how the modest topography in boreal forests could influence the availability of microhabitats and possibly potential sites for oviposition and larval development. In general, topographic features such as north facing slopes and high flow accumulation were important predictors of the proportion of females. Models derived from larger scale topography, such as hillsides or small watersheds on the order of ¼-1 ha were better predictors of the proportion of females than were models derived from finer scale topography such as hummocks and small depressions. We conclude that topography likely influences the distribution of carabids based on hydrological mechanisms rather than factors related to temperature. We further suggest based on the scale of responses that these hydrological mechanisms may be linked to the attenuation of past disturbances by wildfire and the propensity of unburned forest patches and fire skips.

  10. Postfire Succession of Ants (Hymenoptera: Formicidae) Nesting in Dead Wood of Northern Boreal Forest.

    Science.gov (United States)

    Boucher, Philippe; Hébert, Christian; Francoeur, André; Sirois, Luc

    2015-10-01

    Dead wood decomposition begins immediately after tree death and involves a large array of invertebrates. Ecological successions are still poorly known for saproxylic organisms, particularly in boreal forests. We investigated the use of dead wood as nesting sites for ants along a 60-yr postfire chronosequence in northeastern coniferous forests. We sampled a total of 1,625 pieces of dead wood, in which 263 ant nests were found. Overall, ant abundance increased during the first 30 yr after wildfire, and then declined. Leptothorax cf. canadensis Provancher, the most abundant species in our study, was absent during the first 2 yr postfire, but increased steadily until 30 yr after fire, whereas Myrmica alaskensis Wheeler, second in abundance, was found at all stages of succession in the chronosequence. Six other species were less frequently found, among which Camponotus herculeanus (Linné), Formica neorufibarbis Emery, and Formica aserva Forel were locally abundant, but more scarcely distributed. Dead wood lying on the ground and showing numerous woodborer holes had a higher probability of being colonized by ants. The C:N ratio was lower for dead wood colonized by ants than for noncolonized dead wood, showing that the continuous occupation of dead wood by ants influences the carbon and nitrogen dynamics of dead wood after wildfire in northern boreal forests. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  11. High latitude cooling associated with landscape changes from North American boreal forest fires

    Directory of Open Access Journals (Sweden)

    B. M. Rogers

    2012-09-01

    Full Text Available Fires in the boreal forests of North America are generally stand-replacing, killing the majority of trees and initiating succession that may last over a century. Functional variation during succession can affect local surface energy budgets and, potentially, regional climate. Burn area across Alaska and Canada has increased in the last few decades and is projected to be substantially higher by the end of the 21st century because of a warmer climate with longer growing seasons. Here we simulated the changes in forest composition due to altered burn area using a stochastic model of fire occurrence, historical fire data from national inventories, and succession trajectories derived from remote sensing. When coupled to an Earth system model, younger vegetation from increased burning cooled the high-latitude atmosphere, primarily in the winter and spring, with noticeable feedbacks from the ocean and sea ice. Results from multiple scenarios suggest that a doubling of burn area would result in surface cooling of 0.23 ± 0.09 °C and 0.43 ± 0.12 °C for winter–spring and February–April time periods, respectively. This could provide a negative feedback to high-latitude terrestrial warming during winter on the order of 4–6% for a doubling, and 14–23% for a quadrupling, of burn area. Further work is needed to integrate all the climate drivers from boreal forest fires, including aerosols and greenhouse gasses.

  12. Why Do the Boreal Forest Ecosystems of Northwestern Europe Differ from Those of Western North America?

    Science.gov (United States)

    Boonstra, Rudy; Andreassen, Harry P.; Boutin, Stan; Hušek, Jan; Ims, Rolf A.; Krebs, Charles J.; Skarpe, Christina; Wabakken, Petter

    2016-01-01

    Abstract The boreal forest is one of the largest terrestrial biomes on Earth. Conifers normally dominate the tree layer across the biome, but other aspects of ecosystem structure and dynamics vary geographically. The cause of the conspicuous differences in the understory vegetation and the herbivore–predator cycles between northwestern Europe and western North America presents an enigma. Ericaceous dwarf shrubs and 3– to 4-year vole–mustelid cycles characterize the European boreal forests, whereas tall deciduous shrubs and 10-year snowshoe hare–lynx cycles characterize the North American ones. We discuss plausible explanations for this difference and conclude that it is bottom-up: Winter climate is the key determinant of the dominant understory vegetation that then determines the herbivore–predator food-web interactions. The crucial unknown for the twenty-first century is how climate change and increasing instability will affect these forests, both with respect to the dynamics of individual plant and animal species and to their community interactions. PMID:28533563

  13. Divergence in foraging behavior of foliage-gleaning birds of Canadian and Russian boreal forests.

    Science.gov (United States)

    Greenberg, Russell; Pravosudov, Vladimir; Sterling, John; Kozlenko, Anna; Kontorschikov, Vitally

    1999-08-01

    We compared foraging behavior of foliage-gleaning birds of the boreal forest of two Palaearctic (central Siberia and European Russia) and two Nearctic (Mackenzie and Ontario, Canada) sites. Using discriminant function analysis on paired sites we were able to distinguish foliage-gleaning species from the Nearctic and Palaearctic with few misclassifications. The two variables that most consistently distinguished species of the two avifaunas were the percentage use of conifer foliage and the percentage use of all foliage. Nearctic foliage-gleaner assemblages had more species that foraged predominantly from coniferous foliage and displayed a greater tendency to forage from foliage, both coniferous and broad-leafed, rather than twigs, branches, or other substrates. The greater specialization on foliage and, in particular, conifer foliage by New World canopy foliage insectivores is consistent with previously proposed hypotheses regarding the role of Pleistocene vegetation history on ecological generalization of Eurasian species. Boreal forest, composed primarily of spruce and pine, was widespread in eastern North America, whereas pockets of forest were scattered in Eurasia (mostly the mountains of southern Europe and Asia). This may have affected the populations of birds directly or indirectly through reduction in the diversity and abundance of defoliating outbreak insects. Loss of habitat and resources may have selected against ecological specialization on these habitats and resources.

  14. 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

  15. Long-Term Record of Sampled Disturbances in Northern Eurasian Boreal Forest from Pre-2000 Landsat Data

    Directory of Open Access Journals (Sweden)

    Dong Chen

    2014-06-01

    Full Text Available Stand age distribution is an important descriptor of boreal forest structure, which is directly linked to many ecosystem processes including the carbon cycle, the land–atmosphere interaction and ecosystem services, among others. Almost half of the global boreal biome is located in Russia. The vast extent, remote location, and limited accessibility of Russian boreal forests make remote sensing the only feasible approach to characterize these forests to their full extent. A wide variety of satellite observations are currently available to monitor forest change and infer its structure; however, the period of observations is mostly limited to the 2000s era. Reconstruction of wall-to-wall maps of stand age distribution requires merging longer-term site observations of forest cover change available at the Landsat scale at a subset of locations in Russia with the wall-to-wall coverage available from coarse resolution satellites since 2000. This paper presents a dataset consisting of a suite of multi-year forest disturbance samples and samples of undisturbed forests across Russia derived from Landsat Thematic Mapper and Enhanced Thematic Mapper Plus images from 1985 to 2000. These samples provide crucial information regarding disturbance history in selected regions across the Russian boreal forest and are designed to serve as a training and/or validation dataset for coarse resolution data products. The overall accuracy and Kappa coefficient for the entire sample collection was found to be 83.98% and 0.83%, respectively. It is hoped that the presented dataset will benefit subsequent studies on a variety of aspects of the Russian boreal forest, especially in relation to the carbon budget and climate.

  16. Temperate and boreal forest mega-fires: characteristics and challenges

    Science.gov (United States)

    Stephens, Scott L.; Burrows, Neil; Buyantuyev, Alexander; Gray, Robert W.; Keane, Robert E.; Kubian, Rick; Liu, Shirong; Seijo, Francisco; Shu, Lifu; Tolhurst, Kevin G.; Van Wagtendonk, Jan W.

    2014-01-01

    Mega-fires are often defined according to their size and intensity but are more accurately described by their socioeconomic impacts. Three factors – climate change, fire exclusion, and antecedent disturbance, collectively referred to as the “mega-fire triangle” – likely contribute to today's mega-fires