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Sample records for canadian boreal forest

  1. 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...

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

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    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

  3. Predicting Climate Change Impacts to the Canadian Boreal Forest

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    Trisalyn A. Nelson

    2014-03-01

    Full Text Available Climate change is expected to alter temperature, precipitation, and seasonality with potentially acute impacts on Canada’s boreal. In this research we predicted future spatial distributions of biodiversity in Canada’s boreal for 2020, 2050, and 2080 using indirect indicators derived from remote sensing and based on vegetation productivity. Vegetation productivity indices, representing annual amounts and variability of greenness, have been shown to relate to tree and wildlife richness in Canada’s boreal. Relationships between historical satellite-derived productivity and climate data were applied to modelled scenarios of future climate to predict and map potential future vegetation productivity for 592 regions across Canada. Results indicated that the pattern of vegetation productivity will become more homogenous, particularly west of Hudson Bay. We expect climate change to impact biodiversity along north/south gradients and by 2080 vegetation distributions will be dominated by processes of seasonality in the north and a combination of cumulative greenness and minimum cover in the south. The Hudson Plains, which host the world’s largest and most contiguous wetland, are predicted to experience less seasonality and more greenness. The spatial distribution of predicted trends in vegetation productivity was emphasized over absolute values, in order to support regional biodiversity assessments and conservation planning.

  4. 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.

  5. Models parameterization for SWE retrievals from passive microwave over Canadian boreal forest

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    Roy, A.; Royer, A.; Langlois, A.; Montpetit, B.

    2012-12-01

    Boreal forest is the world largest northern land biome and has important impact and feedback on climate. Snow in this ecosystem changed drastically surface energy balance (albedo, turbulent fluxes). Furthermore, snow is a freshwater reservoir influencing hydrological regime and is an important source of energy through hydroelectricity. Passive microwave remote sensing is an appealing approach for characterizing the properties of snow at the synoptic scale; images are available at least twice a day for northern regions where meteorological stations and networks are generally sparse. However, major challenge such as forest canopy contribution and snow grain size within the snowpack, which have both huge impact on passive microwave signature from space-born sensors, must be well parameterized to retrieve variables of interest like Snow water equivalent (SWE). In this presentation, we show advances made in boreal forest τ-ω (forest transmissivity and scattering) and QH (soil reflectivity) models parameterization, as well as snow grains consideration development in the microwave snow emission. In the perspective of AMSR-E brightness temperature (Tb) assimilation in the Canadian Land surface scheme (CLASS), we used a new version of a multi-layer snow emission model: DMRT-ML. First, based on two distinct Tb datasets (winter airborne and summer space-borne), τ-ω and QH models are parameterized at 4 frequencies (6.9, 10.7, 18.7 and 36.5 GHz) for dense boreal forest sites. The forest transmissivity is then spatialized by establishing a relationship with forest structure parameters (LAI and stem volume). Secondly, snow surface specific area (SSA) was parameterized in DMRT-ML based on SWIR reflectance measurements for SSA calculation, as well as snow characteristics (temperature, density, height) and radiometric (19 & 37 GHz) measurements conducted on 20 snowpits in different open environments (grass, tundra, dry fen). Analysis shows that a correction factor must be

  6. 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.

  7. Composition of carbonaceous smoke particles from prescribed burning of a Canadian boreal forest: 1. Organic aerosol characterization by gas chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Mazurek, M.A.; Laterza, C.; Newman, L.; Daum, P. [Brookhaven National Lab., Upton, NY (United States); Cofer, W.R. III; Levine, J.S. [National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center; Winstead, E.L. [Science Applications International Corporation, Hampton, VA (United States)

    1995-06-01

    In this study we examine the molecular organic constituents (C8 to C40 lipid compounds) collected as smoke particles from a Canadian boreal forest prescribed burn. Of special interest are (1) the molecular identity of polar organic aerosols, and (2) the amount of polar organic matter relative to the total mass of aerosol particulate carbon. Organic extracts of smoke aerosol particles show complex distributions of the lipid compounds when analyzed by capillary gas chromatography/mass spectrometry. The molecular constituents present as smoke aerosol are grouped into non-polar (hydrocarbons) and polar {minus}2 oxygen atoms) subtractions. The dominant chemical species found in the boreal forest smoke aerosol are unaltered resin compounds (C20 terpenes) which are abundant in unburned conifer wood, plus thermally altered wood lignins and other polar aromatic hydrocarbons. Our results show that smoke aerosols contain molecular tracers which are related to the biofuel consumed. These smoke tracers can be related structurally back to the consumed softwood and hardwood vegetation. In addition, combustion of boreal forest materials produces smoke aerosol particles that are both oxygen-rich and chemically complex, yielding a carbonaceous aerosol matrix that is enriched in polar substances. As a consequence, emissions of carbonaceous smoke particles from large-scale combustion of boreal forest land may have a disproportionate effect on regional atmospheric chemistry and on cloud microphysical processes.

  8. A Comparative Analysis of Burned Area Datasets in Canadian Boreal Forest in 2000

    Science.gov (United States)

    Núñez-Casillas, Laia; Moreno-Ruiz, José Andrés

    2013-01-01

    The turn of the new millennium was accompanied by a particularly diverse group of burned area datasets from different sensors in the Canadian boreal forests, brought together in a year of low global fire activity. This paper provides an assessment of spatial and temporal accuracy, by means of a fire-by-fire comparison of the following: two burned area datasets obtained from SPOT-VEGETATION (VGT) imagery, a MODIS Collection 5 burned area dataset, and three different datasets obtained from NOAA-AVHRR. Results showed that burned area data from MODIS provided accurate dates of burn but great omission error, partially caused by calibration problems. One of the VGT-derived datasets (L3JRC) represented the largest number of fire sites in spite of its great overall underestimation, whereas the GBA2000 dataset achieved the best burned area quantification, both showing delayed and very variable fire timing. Spatial accuracy was comparable between the 5 km and the 1 km AVHRR-derived datasets but was remarkably lower in the 8 km dataset leading, us to conclude that at higher spatial resolutions, temporal accuracy was lower. The probable methodological and contextual causes of these differences were analyzed in detail. PMID:23818817

  9. Impact of forest harvesting on trophic structure of eastern Canadian Boreal Shield lakes: insights from stable isotope analyses.

    Science.gov (United States)

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

    2014-01-01

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

  10. Patterns of cross-continental variation in tree seed mass in the Canadian Boreal Forest.

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    Jushan Liu

    Full Text Available Seed mass is an adaptive trait affecting species distribution, population dynamics and community structure. In widely distributed species, variation in seed mass may reflect both genetic adaptation to local environments and adaptive phenotypic plasticity. Acknowledging the difficulty in separating these two aspects, we examined the causal relationships determining seed mass variation to better understand adaptability and/or plasticity of selected tree species to spatial/climatic variation. A total of 504, 481 and 454 seed collections of black spruce (Picea mariana (Mill. B.S.P., white spruce (Picea glauca (Moench Voss and jack pine (Pinus banksiana Lamb across the Canadian Boreal Forest, respectively, were selected. Correlation analyses were used to determine how seed mass vary with latitude, longitude, and altitude. Structural Equation Modeling was used to examine how geographic and climatic variables influence seed mass. Climatic factors explained a large portion of the variation in seed mass (34, 14 and 29%, for black spruce, white spruce and jack pine, respectively, indicating species-specific adaptation to long term climate conditions. Higher annual mean temperature and winter precipitation caused greater seed mass in black spruce, but annual precipitation was the controlling factor for white spruce. The combination of factors such as growing season temperature and evapotranspiration, temperature seasonality and annual precipitation together determined seed mass of jack pine. Overall, sites with higher winter temperatures were correlated with larger seeds. Thus, long-term climatic conditions, at least in part, determined spatial variation in seed mass. Black spruce and Jack pine, species with relatively more specific habitat requirements and less plasticity, had more variation in seed mass explained by climate than did the more plastic species white spruce. As traits such as seed mass are related to seedling growth and survival, they

  11. Use of Large Clear-Cuts by Wilson's Warbler in an Eastern Canadian Boreal Forest

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    André Desrochers

    2012-12-01

    Full Text Available Wilson's Warbler (Cardellina pusilla; WIWA has been declining for several decades, possibly because of habitat loss. We compared occupancy of territorial males in two habitat types of Québec's boreal forest, alder (Alnus spp. scrubland and recent clear-cuts. Singing males occurred in clusters, their occupancy was similar in both habitats, but increased with the amount of alder or clear-cut within 400 m of point-count stations. A despotic distribution of males between habitats appeared unlikely, because there were no differences in morphology between males captured in clear-cuts vs. alder. Those results contrast with the prevailing view, mostly based on western populations, that WIWA are wetland or riparian specialists, and provide the first evidence for a preference for large tracts of habitat in this species. Clear-cuts in the boreal forest may benefit WIWA by supplying alternative nesting habitat. However, the role of clear-cuts as source or sink habitats needs to be addressed with data on reproduction.

  12. Analysis of the boreal forest-tundra ecotone: A test of AVIRIS capabilities in the Eastern Canadian subarctic

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    Goward, Samuel N.; Petzold, Donald E.

    1989-01-01

    A comparison was conducted between ground reflectance spectra collected in Schefferville, Canada and imaging spectrometer observations acquired by the AVIRIS sensor in a flight of the ER-2 Aircraft over the same region. The high spectral contrasts present in the Canadian Subarctic appeared to provide an effective test of the operational readiness of the AVIRIS sensor. Previous studies show that in this location various land cover materials possess a wide variety of visible/near infrared reflectance properties. Thus, this landscape served as an excellent test for the sensing variabilities of the newly developed AVIRIS sensor. An underlying hypothesis was that the unique visible/near infrared spectral reflectance patterns of Subarctic lichens could be detected from high altitudes by this advanced imaging spectrometer. The relation between lichen occurrence and boreal forest-tundra ecotone dynamics was investigated.

  13. Massive mortality of aspen following severe drought along the southern edge of the Canadian boreal forest

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    Michaelian, Michael; Hogg, Edward H; Hall, Ronald J; Arsenault, Eric

    2011-01-01

    Drought-induced, regional-scale dieback of forests has emerged as a global concern that is expected to escalate under model projections of climate change. Since 2000, drought of unusual severity, extent, and duration has affected large areas of western North America, leading to regional-scale dieback of forests in the southwestern US. We report on drought impacts on forests in a region farther north, encompassing the transition between boreal forest and prairie in western Canada. A central question is the significance of drought as an agent of large-scale tree mortality and its potential future impact on carbon cycling in this cold region. We used a combination of plot-based, meteorological, and remote sensing measures to map and quantify aboveground, dead biomass of trembling aspen (Populus tremuloides Michx.) across an 11.5 Mha survey area where drought was exceptionally severe during 2001–2002. Within this area, a satellite-based land cover map showed that aspen-dominated broadleaf forests occupied 2.3 Mha. Aerial surveys revealed extensive patches of severe mortality (>55%) resembling the impacts of fire. Dead aboveground biomass was estimated at 45 Mt, representing 20% of the total aboveground biomass, based on a spatial interpolation of plot-based measurements. Spatial variation in percentage dead biomass showed a moderately strong correlation with drought severity. In the prairie-like, southern half of the study area where the drought was most severe, 35% of aspen biomass was dead, compared with an estimated 7% dead biomass in the absence of drought. Drought led to an estimated 29 Mt increase in dead biomass across the survey area, corresponding to 14 Mt of potential future carbon emissions following decomposition. Many recent, comparable episodes of drought-induced forest dieback have been reported from around the world, which points to an emerging need for multiscale monitoring approaches to quantify drought effects on woody biomass and carbon cycling

  14. Effect of Organic Layer Thickness on Black Spruce Aging Mistakes in Canadian Boreal Forests

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    Ahmed Laamrani

    2016-03-01

    Full Text Available Boreal black spruce (Picea mariana forests are prone to developing thick organic layers (paludification. Black spruce is adapted to this environment by the continuous development of adventitious roots, masking the root collar and making it difficult to age trees. Ring counts above the root collar underestimate age of trees, but the magnitude of age underestimation of trees in relation to organic layer thickness (OLT is unknown. This age underestimation is required to produce appropriate age-correction tools to be used in land resource management. The goal of this study was to assess aging errors that are done with standard ring counts of trees growing in sites with different degrees of paludification (OLT; 0–25 cm, 26–65 cm, >65 cm. Age of 81 trees sampled at three geographical locations was determined by ring counts at ground level and at 1 m height, and real age of trees was determined by cross-dating growth rings down to the root collar (root/shoot interface. Ring counts at 1 m height underestimated age of trees by a mean of 22 years (range 13–49 and 52 years (range 14–112 in null to low vs. moderately to highly paludified stands, respectively. The percentage of aging-error explained by our linear model was relatively high (R2adj = 0.71 and showed that OLT class and age at 0-m could be used to predict total aging-error while neither DBH nor geographic location could. The resulting model has important implications for forest management to accurately estimate productivity of these forests.

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

    OpenAIRE

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

    2015-01-01

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

  16. Boreal forest fire emissions in fresh Canadian smoke plumes: C1-C10 volatile organic compounds (VOCs, CO2, CO, NO2, NO, HCN and CH3CN

    Directory of Open Access Journals (Sweden)

    M. Yang

    2011-07-01

    Full Text Available Boreal regions comprise about 17 % of the global land area, and they both affect and are influenced by climate change. To better understand boreal forest fire emissions and plume evolution, 947 whole air samples were collected aboard the NASA DC-8 research aircraft in summer 2008 as part of the ARCTAS-B field mission, and analyzed for 79 non-methane volatile organic compounds (NMVOCs using gas chromatography. Together with simultaneous measurements of CO2, CO, CH4, CH2O, NO2, NO, HCN and CH3CN, these measurements represent the most comprehensive assessment of trace gas emissions from boreal forest fires to date. Based on 105 air samples collected in fresh Canadian smoke plumes, 57 of the 80 measured NMVOCs (including CH2O were emitted from the fires, including 45 species that were quantified from boreal forest fires for the first time. After CO2, CO and CH4, the largest emission factors (EFs for individual species were formaldehyde (2.1 ± 0.2 g kg−1, followed by methanol, NO2, HCN, ethene, α-pinene, β-pinene, ethane, benzene, propene, acetone and CH3CN. Globally, we estimate that boreal forest fires release 2.4 ± 0.6 Tg C yr−1 in the form of NMVOCs, with approximately 41 % of the carbon released as C1-C2 NMVOCs and 21 % as pinenes. These are the first reported field measurements of monoterpene emissions from boreal forest fires, and we speculate that the pinenes, which are relatively heavy molecules, were detected in the fire plumes as the result of distillation of stored terpenes as the vegetation is heated. Their inclusion in smoke chemistry models is expected to improve model predictions of secondary organic aerosol (SOA formation. The fire-averaged EF of dichloromethane or CH2Cl2, (6.9 ± 8.6 × 10−4 g kg−1, was not significantly different from zero and supports recent findings that its global biomass burning source appears to have been overestimated. Similarly, we found no evidence for emissions of chloroform (CHCl3 or methyl

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

    Science.gov (United States)

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

    1997-12-01

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

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

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

    1997-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Ahmed El-Guellab

    2015-05-01

    Full Text Available 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 guide to determine sustainable forest harvesting levels, by reconstructing the Holocene fire history at the northern limit of commercial forestry in Quebec using charcoal particles preserved in lake sediments. Methods Sediment cores were sampled from four lakes located close to the northern limit of commercial forestry in Quebec. The cores were sliced into consecutive 0.5 cm thick subsamples from which 1 cm3 was extracted to count and measure charcoal particles larger than 150 microns. Age-depth models were obtained for each core based on accelerator mass spectroscopy (AMS radiocarbon dates. Holocene fire histories were reconstructed by combining charcoal counts and age-depth models to obtain charcoal accumulation rates and, after statistical treatment, long-term trends in fire occurrence (expressed as number of fires per 1000 years. Results Fire occurrence varied between the four studied sites, but fires generally occurred more often during warm and dry periods of the Holocene, especially during the Holocene Thermal Maximum (7000–3500 cal. BP, when fire occurrence was twice as high as at present. Conclusions The current fire regime in the study area is still within the natural range of variability observed over the Holocene. However, climatic conditions comparable to the Holocene Thermal Maximum could be reached within the next few decades, thus substantially reducing the amount of wood available to the forest industry.

  20. Response of canopy nitrogen uptake to a rapid decrease in bulk nitrate deposition in two eastern Canadian boreal forests.

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    Houle, D; Marty, C; Duchesne, L

    2015-01-01

    A few studies have reported a recent and rapid decline in NO3(-) deposition in eastern North America. Whether this trend can be observed at remote boreal sites with low rates of N deposition and how it could impact canopy uptake (CU) of N remain unknown. Here we report trends between 1997/1999 and 2012 for precipitation, throughfall N deposition as well as inorganic N CU for two boreal forest sites of Quebec, Canada, with contrasted N deposition rates and tree species composition. NO3(-) bulk deposition declined by approximately 50% at both sites over the studied period while no change was observed for NH4(+). As a result, the contribution of NH4(+) to inorganic N deposition changed from ~33% to more than 50% during the study period. On average, 52-59% of N deposition was intercepted by the canopy, the retention being higher for NH4(+) (60-67%) than for NO3(-) (45-54%). The decrease in NO3(-) bulk deposition and the increase in the NH4(+):NO3(-) ratio had important impacts on N-canopy interactions. The contribution of NH4(+) CU to that of total inorganic N CU increased at both sites but the trend was significant only at Tirasse (lowest N deposition). At this site, absolute NO3(-) CU significantly decreased (as did total N CU) during the study period, a consequence of the strong relationship (r(2) = 0.88) between NO3(-) bulk deposition and NO3(-) CU. Our data suggest that N interactions with forest canopies may change rapidly with changes in N deposition as well as with tree species composition.

  1. Boreal Forest Watch: A BOREAS Outreach Program

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    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.

  2. Boreal forest fire emissions in fresh Canadian smoke plumes: C1-C10 volatile organic compounds (VOCs), CO2, CO, NO2, NO, HCN and CH3CN

    Science.gov (United States)

    I. J. Simpson; S. K. Akagi; B. Barletta; N. J. Blake; Y. Choi; G. S. Diskin; A. Fried; H. E. Fuelberg; S. Meinardi; F. S. Rowland; S. A. Vay; A. J. Weinheimer; P. O. Wennberg; P. Wiebring; A. Wisthaler; M. Yang; R. J. Yokelson; D. R. Blake

    2011-01-01

    Boreal regions comprise about 17% of the global land area, and they both affect and are influenced by climate change. To better understand boreal forest fire emissions and plume evolution, 947 whole air samples were collected aboard the NASA DC-8 research aircraft in summer 2008 as part of the ARCTAS-B field mission, and analyzed for 79 non-methane volatile organic...

  3. Canadian boreal forest greening and browning trends: an analysis of biogeographic patterns and the relative roles of disturbance versus climate drivers

    Science.gov (United States)

    Sulla-Menashe, Damien; Woodcock, Curtis E.; Friedl, Mark A.

    2018-01-01

    Recent studies have used satellite-derived normalized difference vegetation index (NDVI) time series to explore geographic patterns in boreal forest greening and browning. A number of these studies indicate that boreal forests are experiencing widespread browning, and have suggested that these patterns reflect decreases in forest productivity induced by climate change. Here we use NDVI time series from Landsat, which has much higher quality and spatial resolution than imagery used in most previous studies, to characterize biogeographic patterns in greening and browning across Canada’s boreal forest and to explore the drivers behind observed trends. Our results show that the majority of NDVI changes in Canada’s boreal forest reflect disturbance-recovery dynamics not climate change impacts, that greening and browning trends outside of disturbed forests are consistent with expected ecological responses to regional changes in climate, and that observed NDVI changes are geographically limited and relatively small in magnitude. By examining covariance between changes in NDVI and temperature and precipitation in locations not affected by disturbance, our results isolate and characterize the nature and magnitude of greening and browning directly associated with climate change. Consistent with biogeographic theory, greening and browning unrelated to disturbance tended to be located in ecotones near boundaries of the boreal forest bioclimatic envelope. We observed greening to be most prevalent in Eastern Canada, which is more humid, and browning to be most prevalent in Western Canada, where forests are more prone to moisture stress. We conclude that continued long-term climate change has the potential to significantly alter the character and function of Canada’s boreal forest, but recent changes have been modest and near-term impacts are likely to be focused in or near ecotones.

  4. Browning boreal forests of western North America

    Science.gov (United States)

    Verbyla, David

    2011-12-01

    willow leaf blotch miner in boreal Alaska are likely to have resulted in decreased NDVI (Parent and Verbyla 2010). The NDVI browning trend has expanded in area in boreal North America (Beck and Goetz 2011). If the trend towards a warmer and drier climate continues, these areas may represent a future tipping point where drought-induced mortality across a boreal region may occur. Such events have already occurred in the western United States (van Mantgem et al 2009) and the aspen parklands of the southern Canadian boreal forest (Michaelian et al 2010). References Alcaraz-Segura D, Chuvieco E, Epstein H E, Kasischke E S and Trishchenko A 2010 Debating the greening vs. browning of the North American boreal forest: differences between satellite datasets Glob. Change Biol. 16 760-70 Anderson L, Abbott M B, Finney B P and Burns S J 2007 Late Holocene moisture balance variability in the southwest Yukon Territory, Canada Quatern. Sci. Rev. 26 130-41 Barber V A, Juday G P and Finney B P 2000 Reduced growth of Alaskan white spruce in the twentieth century from temperature-induced drought stress Nature 405 668-73 Barber V A, Juday G P, Finney B P and Wilmking M 2004 Reconstruction of summer temperatures in interior Alaska from tree-ring proxies: evidence for changing synoptic climate regimes Clim. Change 63 91-120 Beck P S A and Goetz S J 2011 Satellite observations of high northern latitude vegetation productivity changes between 1982 and 2008: ecological variability and regional differences Environ. Res. Lett. 6 045501 Beck P S A, Juday G P, Alix C, Barber V A, Winslow S E, Sousa E E, Heiser P, Herriges J D and Goetz S J 2011 Changes in forest productivity across Alaska consistent with biome shift Ecol. Lett. 14 373-9 Berg E E, Henry J D, Fastie C L, De Volder A D and Matsuoka S M 2006 Spruce beetle outbreaks on the Kenai Peninsula, Alaska, and Kluane National Park and Reserve, Yukon Territory: relationship to summer temperatures and regional differences in disturbance regimes

  5. 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.

  6. Carbon balance of the Alaskan boreal forest

    Science.gov (United States)

    John Yarie; Tim Hammond

    1996-01-01

    Determination of the carbon balance in a broad forest region like the Alaskan boreal forest requires the development of a number of important environmental (state factors) classes to allow for the development of carbon balance estimates.

  7. 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...

  8. 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.

  9. Traditional use of medicinal plants in the boreal forest of Canada: review and perspectives

    Science.gov (United States)

    2012-01-01

    Background The boreal forest of Canada is home to several hundred thousands Aboriginal people who have been using medicinal plants in traditional health care systems for thousands of years. This knowledge, transmitted by oral tradition from generation to generation, has been eroding in recent decades due to rapid cultural change. Until now, published reviews about traditional uses of medicinal plants in boreal Canada have focused either on particular Aboriginal groups or on restricted regions. Here, we present a review of traditional uses of medicinal plants by the Aboriginal people of the entire Canadian boreal forest in order to provide comprehensive documentation, identify research gaps, and suggest perspectives for future research. Methods A review of the literature published in scientific journals, books, theses and reports. Results A total of 546 medicinal plant taxa used by the Aboriginal people of the Canadian boreal forest were reported in the reviewed literature. These plants were used to treat 28 disease and disorder categories, with the highest number of species being used for gastro-intestinal disorders, followed by musculoskeletal disorders. Herbs were the primary source of medicinal plants, followed by shrubs. The medicinal knowledge of Aboriginal peoples of the western Canadian boreal forest has been given considerably less attention by researchers. Canada is lacking comprehensive policy on harvesting, conservation and use of medicinal plants. This could be explained by the illusion of an infinite boreal forest, or by the fact that many boreal medicinal plant species are widely distributed. Conclusion To our knowledge, this review is the most comprehensive to date to reveal the rich traditional medicinal knowledge of Aboriginal peoples of the Canadian boreal forest. Future ethnobotanical research endeavours should focus on documenting the knowledge held by Aboriginal groups that have so far received less attention, particularly those of the western

  10. Traditional use of medicinal plants in the boreal forest of Canada: review and perspectives.

    Science.gov (United States)

    Uprety, Yadav; Asselin, Hugo; Dhakal, Archana; Julien, Nancy

    2012-01-30

    The boreal forest of Canada is home to several hundred thousands Aboriginal people who have been using medicinal plants in traditional health care systems for thousands of years. This knowledge, transmitted by oral tradition from generation to generation, has been eroding in recent decades due to rapid cultural change. Until now, published reviews about traditional uses of medicinal plants in boreal Canada have focused either on particular Aboriginal groups or on restricted regions. Here, we present a review of traditional uses of medicinal plants by the Aboriginal people of the entire Canadian boreal forest in order to provide comprehensive documentation, identify research gaps, and suggest perspectives for future research. A review of the literature published in scientific journals, books, theses and reports. A total of 546 medicinal plant taxa used by the Aboriginal people of the Canadian boreal forest were reported in the reviewed literature. These plants were used to treat 28 disease and disorder categories, with the highest number of species being used for gastro-intestinal disorders, followed by musculoskeletal disorders. Herbs were the primary source of medicinal plants, followed by shrubs. The medicinal knowledge of Aboriginal peoples of the western Canadian boreal forest has been given considerably less attention by researchers. Canada is lacking comprehensive policy on harvesting, conservation and use of medicinal plants. This could be explained by the illusion of an infinite boreal forest, or by the fact that many boreal medicinal plant species are widely distributed. To our knowledge, this review is the most comprehensive to date to reveal the rich traditional medicinal knowledge of Aboriginal peoples of the Canadian boreal forest. Future ethnobotanical research endeavours should focus on documenting the knowledge held by Aboriginal groups that have so far received less attention, particularly those of the western boreal forest. In addition, several

  11. Boreal forest health and global change.

    Science.gov (United States)

    Gauthier, S; Bernier, P; Kuuluvainen, T; Shvidenko, A Z; Schepaschenko, D G

    2015-08-21

    The boreal forest, one of the largest biomes on Earth, provides ecosystem services that benefit society at levels ranging from local to global. Currently, about two-thirds of the area covered by this biome is under some form of management, mostly for wood production. Services such as climate regulation are also provided by both the unmanaged and managed boreal forests. Although most of the boreal forests have retained the resilience to cope with current disturbances, projected environmental changes of unprecedented speed and amplitude pose a substantial threat to their health. Management options to reduce these threats are available and could be implemented, but economic incentives and a greater focus on the boreal biome in international fora are needed to support further adaptation and mitigation actions. Copyright © 2015, American Association for the Advancement of Science.

  12. Origin and Availability of Large Cavities for Barrow’s Goldeneye (Bucephala islandica, a Species at Risk Inhabiting the Eastern Canadian Boreal Forest

    Directory of Open Access Journals (Sweden)

    Marie-Andrée Vaillancourt,

    2009-06-01

    Full Text Available Large secondary-nesting birds such as ducks rely on appropriate cavities for breeding. The main objective of this study was to assess the availability of large cavities and the potential of a managed boreal coniferous landscape to provide nesting trees within the breeding area of the eastern population of Barrow’s Goldeneye (Bucephala islandica, a cavity-nesting species at risk in Canada. Woodpecker surveys were conducted in both conifer and mixed-wood landscapes, and cavities were sought in line transects distributed in unharvested and linear remnant stands of balsam fir (Abies balsamea and black spruce (Picea mariana as well as in cutblocks. No Pileated Woodpeckers (Dryocopus pileatus were detected in the breeding area of Barrow’s Goldeneye, but the species was present in the nearby lowland area in which trembling aspen (Populus tremuloides is abundant. Only 10 trees (0.2% of those sampled supported cavities considered suitable for Barrow’s Goldeneye in terms of dimensions and canopy openness. Most of the suitable cavities found during this study were nonexcavated apical (chimney cavities in relatively short snags that showed advanced states of decay. A diameter-at-breast-height threshold was determined for each tree species, after which the probability of cavity occurrence was enhanced in terms of potential cavity trees for Barrow’s Goldeneye. Remnant linear forest sites had lower potential tree densities than did their unharvested equivalents. Large cavities were thus a rare component in this boreal landscape, suggesting that they may be a limiting factor for this population at risk. Current even-aged forest management that mainly relies on clear-cut practices is likely to further reduce the potential of this landscape to provide trees with suitable cavities.

  13. 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...

  14. 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…

  15. Nitrogen alters carbon dynamics during early succession in boreal forest

    Science.gov (United States)

    Steven D. Allison; Tracy B. Gartner; Michelle C. Mack; Krista McGuire; Kathleen. Treseder

    2010-01-01

    Boreal forests are an important source of wood products, and fertilizers could be used to improve forest yields, especially in nutrient poor regions of the boreal zone. With climate change, fire frequencies may increase, resulting in a larger fraction of the boreal landscape present in early successional stages. Since most fertilization studies have focused on mature...

  16. Boreal forest biomass classification with TanDEM-X

    OpenAIRE

    Torano Caicoya, Astor; Kugler, Florian; Papathanassiou, Kostas; Hajnsek, Irena

    2012-01-01

    High spatial resolution X-band interferometric SAR data from the TanDEM-X, in the operational DEM generation mode, are sensitive to forest structure and can therefore be used for thematic boreal forest classification of forest environments. The interferometric coherence in absence of temporal decorrelation depends strongly on forest height and structure. Due to the rather homogenous structure of boreal forest, forest biomass can be derived from forest height, on the basis of allometric equati...

  17. 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.

  18. Browning boreal forests of western North America

    Science.gov (United States)

    David. Verbyla

    2011-01-01

    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...

  19. 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.

  20. Controls on moss evaporation in a boreal black spruce forest

    NARCIS (Netherlands)

    Heijmans, M.M.P.D.; Arp, W.J.; Chapin, F.S.

    2004-01-01

    [1] Mosses are an important component of the boreal forest, but little is known about their contribution to ecosystem carbon, water, and energy exchange. We studied the role of mosses in boreal forest evapotranspiration by conducting two experiments in a black spruce forest in Fairbanks, Alaska.

  1. Traditional use of medicinal plants in the boreal forest of Canada: review and perspectives

    Directory of Open Access Journals (Sweden)

    Uprety Yadav

    2012-01-01

    Full Text Available Abstract Background The boreal forest of Canada is home to several hundred thousands Aboriginal people who have been using medicinal plants in traditional health care systems for thousands of years. This knowledge, transmitted by oral tradition from generation to generation, has been eroding in recent decades due to rapid cultural change. Until now, published reviews about traditional uses of medicinal plants in boreal Canada have focused either on particular Aboriginal groups or on restricted regions. Here, we present a review of traditional uses of medicinal plants by the Aboriginal people of the entire Canadian boreal forest in order to provide comprehensive documentation, identify research gaps, and suggest perspectives for future research. Methods A review of the literature published in scientific journals, books, theses and reports. Results A total of 546 medicinal plant taxa used by the Aboriginal people of the Canadian boreal forest were reported in the reviewed literature. These plants were used to treat 28 disease and disorder categories, with the highest number of species being used for gastro-intestinal disorders, followed by musculoskeletal disorders. Herbs were the primary source of medicinal plants, followed by shrubs. The medicinal knowledge of Aboriginal peoples of the western Canadian boreal forest has been given considerably less attention by researchers. Canada is lacking comprehensive policy on harvesting, conservation and use of medicinal plants. This could be explained by the illusion of an infinite boreal forest, or by the fact that many boreal medicinal plant species are widely distributed. Conclusion To our knowledge, this review is the most comprehensive to date to reveal the rich traditional medicinal knowledge of Aboriginal peoples of the Canadian boreal forest. Future ethnobotanical research endeavours should focus on documenting the knowledge held by Aboriginal groups that have so far received less attention

  2. Ecohydrology of Interior Alaska boreal forest systems

    Science.gov (United States)

    Cable, J.; Bolton, W. R.

    2012-12-01

    The ecohydrology of boreal forest ecosystems of Interior Alaska is not well understood largely because of challenges posed by the presence of discontinuous permafrost. Near-surface permafrost results in storage-dominated systems with cold, poorly drained soils, and slow growing, low statured coniferous trees (Picea mariana) or CDE's. The transition to permafrost-free areas can occur over a few meters and is accompanied by a vegetation community dominated by large deciduous trees (Populus sp. and Betula sp.) or DDE's. Typically, areas with permafrost are on north facing slopes and valley bottoms, and areas without permafrost are south facing. In Alaska's boreal forest, the permafrost is very warm and vulnerable to the effects of climate change. Once permafrost begins to thaw, the vegetation community shifts from coniferous to deciduous dominated. Streamflow in watersheds with a larger permafrost distribution tends to be higher and more responsive to precipitation events than in watersheds with low permafrost distribution. In fact, precipitation events in the low permafrost areas do not infiltrate past the rooting zone of the deciduous trees (~5-40 cm). This suggests that the deciduous trees may remove water from the system via uptake and transpiration. We focus on how vegetation water use affects boreal forest hydrology in areas of discontinuous permafrost. Specifically, we ask: what are the patterns of vegetation water use in areas with and without permafrost? This study focuses on the CDE and DDE systems. Our research sites are established on low and high locations on each aspect (south facing DDE, north facing CDE) to capture the variability associated with the different hillside drainage properties. At each of the four sites during the growing season, we measured various aspects of plant water use dynamics, including water flux, water content, water sources, depth of water uptake in the soil, and water stress. We use a Bayesian framework to analyze the data. We

  3. Rock, Paper, Protest: The Fight for the Boreal Forest

    Science.gov (United States)

    Gunz, Sally; Whittaker, Linda

    2016-01-01

    Canada's boreal forests are second only to the Amazon in producing life-giving oxygen and providing a habitat for thousands of species, from the large woodland caribou to the smallest organisms. The boreal forests are the lifeblood of many Aboriginal communities and the thousands of workers, Aboriginal and non-Aboriginal, who harvest and process…

  4. Ecology of Canada lynx in southern boreal forests [Chapter 13

    Science.gov (United States)

    Keith B. Aubry; Gary M. Koehler; John R. Squires

    2000-01-01

    Canada lynx occur throughout boreal forests of North America, but ecological conditions in southern regions differ in many respects from those in Canada and Alaska. To evaluate the extent to which lynx ecology and population biology may differ between these regions, we review existing information from southern boreal forests and compare our findings to...

  5. 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.

  6. Joint production of timber, carbon, and wildlife habitat in the Canadian boreal plains

    Energy Technology Data Exchange (ETDEWEB)

    McCarney, G.R.; Adamowicz, W.L. [Alberta Univ., Edmonton, AB (Canada). Dept. of Rural Economy; Armstrong, G.W. [Alberta Univ., Edmonton, AB (Canada). Dept. of Renewable Resources

    2008-06-15

    The relationships between forest carbon management, sustained timber yield, and the maintenance of wildlife habitats in the Canadian Boreal plain region were investigated. The aim of the study was to provide an estimation of the costs and challenges faced by forest managers in Canada's Boreal mixedwood region. The study used a model that previously analyzed the joint production of timber supplies and wildlife habitats using a natural disturbance model. A carbon budget model was used to separate biomass and dead organic matter carbon pools for individual forest cover types. An extensive marginal cost analysis of the production trade-offs between timber, carbon, and wildlife habitat was conducted. Results were used to demonstrate the potential for cost thresholds in timber supply and carbon sequestration. Thresholds were linked to switch-points in multiple use and specialized land management practices. Results showed that the optimal allocation of sequestered carbon across forest cover type differed with habitat constraints versus timber and carbon management alone. Results indicated that national policy discussions concerning carbon market regulations may wish to consider the potential for thresholds in production cost. Benefits of the management approach were influenced by ecological parameters, harvest flow regulations, and financial incentives for timber supply. 54 refs., 1 tab., 7 figs.

  7. 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

  8. Differential declines in Alaskan boreal forest vitality related to climate and competition.

    Science.gov (United States)

    Trugman, Anna T; Medvigy, David; Anderegg, William R L; Pacala, Stephen W

    2017-10-20

    Rapid warming and changes in water availability at high latitudes alter resource abundance, tree competition, and disturbance regimes. While these changes are expected to disrupt the functioning of boreal forests, their ultimate implications for forest composition are uncertain. In particular, recent site-level studies of the Alaskan boreal forest have reported both increases and decreases in productivity over the past few decades. Here, we test the idea that variations in Alaskan forest growth and mortality rates are contingent on species composition. Using forest inventory measurements and climate data from plots located throughout interior and south-central Alaska, we show significant growth and mortality responses associated with competition, midsummer vapor pressure deficit, and increased growing season length. The governing climate and competition processes differed substantially across species. Surprisingly, the most dramatic climate response occurred in the drought tolerant angiosperm species, trembling aspen, and linked high midsummer vapor pressure deficits to decreased growth and increased insect-related mortality. Given that species composition in the Alaskan and western Canadian boreal forests is projected to shift toward early-successional angiosperm species due to fire regime, these results underscore the potential for a reduction in boreal productivity stemming from increases in midsummer evaporative demand. © 2017 John Wiley & Sons Ltd.

  9. 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

    2017-11-01

    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.

  10. NPP Boreal Forest: Flakaliden, Sweden, 1986-1996, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains three files (.txt format) for an established 8.25 ha boreal forest dominated by Norway spruce, Picea abies, at Flakaliden (64.12 N 19.45 E) in...

  11. NPP Boreal Forest: Kuusamo, Finland, 1967-1972, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains three files (.txt format). One file provides stand characteristics, biomass, and production allocation data for an old-growth boreal forest...

  12. Forest and land inventory using ERTS imagery and aerial photography in the boreal forest region of Alberta, Canada

    Science.gov (United States)

    Kirby, C. L.

    1974-01-01

    Satellite imagery and small-scale (1:120,000) infrared ektachrome aerial photography for the development of improved forest and land inventory techniques in the boreal forest region are presented to demonstrate spectral signatures and their application. The forest is predominately mixed, stands of white spruce and poplar, with some pure stands of black spruce, pine and large areas of poorly drained land with peat and sedge type muskegs. This work is part of coordinated program to evaluate ERTS imagery by the Canadian Forestry Service.

  13. [A new source of methane in boreal forests].

    Science.gov (United States)

    Mukhin, V A; Voronin, P Iu

    2008-01-01

    Methane was found among the gases evolved during natural wood decay caused by bracket fungi in boreal forests. Methane was detected both in decaying wood and fungal fruiting bodies. A scheme of symbiotic association of wood-degrading fungi and anaerobic microorganisms providing the methanogenesis in the wood was proposed. The scale of mycogenic methane emission has to be consistent with the huge volume of decaying wood in boreal forest ecosystems.

  14. 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.

  15. Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest

    Directory of Open Access Journals (Sweden)

    F. Gennaretti

    2017-11-01

    Full Text Available A better understanding of the coupling between photosynthesis and carbon allocation in the boreal forest, together with its associated environmental factors and mechanistic rules, is crucial to accurately predict boreal forest carbon stocks and fluxes, which are significant components of the global carbon budget. Here, we adapted the MAIDEN ecophysiological forest model to consider important processes for boreal tree species, such as nonlinear acclimation of photosynthesis to temperature changes, canopy development as a function of previous-year climate variables influencing bud formation and the temperature dependence of carbon partition in summer. We tested these modifications in the eastern Canadian taiga using black spruce (Picea mariana (Mill. B.S.P. gross primary production and ring width data. MAIDEN explains 90 % of the observed daily gross primary production variability, 73 % of the annual ring width variability and 20–30 % of its high-frequency component (i.e., when decadal trends are removed. The positive effect on stem growth due to climate warming over the last several decades is well captured by the model. In addition, we illustrate how we improve the model with each introduced model adaptation and compare the model results with those of linear response functions. Our results demonstrate that MAIDEN simulates robust relationships with the most important climate variables (those detected by classical response-function analysis and is a powerful tool for understanding how environmental factors interact with black spruce ecophysiology to influence present-day and future boreal forest carbon fluxes.

  16. Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest

    Science.gov (United States)

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

    2017-11-01

    A better understanding of the coupling between photosynthesis and carbon allocation in the boreal forest, together with its associated environmental factors and mechanistic rules, is crucial to accurately predict boreal forest carbon stocks and fluxes, which are significant components of the global carbon budget. Here, we adapted the MAIDEN ecophysiological forest model to consider important processes for boreal tree species, such as nonlinear acclimation of photosynthesis to temperature changes, canopy development as a function of previous-year climate variables influencing bud formation and the temperature dependence of carbon partition in summer. We tested these modifications in the eastern Canadian taiga using black spruce (Picea mariana (Mill.) B.S.P.) gross primary production and ring width data. MAIDEN explains 90 % of the observed daily gross primary production variability, 73 % of the annual ring width variability and 20-30 % of its high-frequency component (i.e., when decadal trends are removed). The positive effect on stem growth due to climate warming over the last several decades is well captured by the model. In addition, we illustrate how we improve the model with each introduced model adaptation and compare the model results with those of linear response functions. Our results demonstrate that MAIDEN simulates robust relationships with the most important climate variables (those detected by classical response-function analysis) and is a powerful tool for understanding how environmental factors interact with black spruce ecophysiology to influence present-day and future boreal forest carbon fluxes.

  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. Snow and Vegetation Interactions at Boundaries in Alaska's Boreal Forest

    Science.gov (United States)

    Hiemstra, C. A.; Sturm, M.

    2012-12-01

    There has been increased attention on snow-vegetation interactions in Arctic tundra because of rapid climate-driven changes affecting that snow-dominated ecosystem. Yet, far less attention is paid to boreal forest snow-vegetation interactions even though climatic conditions are changing there as well. Further, it is the prevalent terrestrial biome on the planet. The forest is a variable patchwork of trees, shrubs, grasses, and forbs shaped by wind, fire, topography, water drainage, and permafrost. These patches and their boundaries have a corresponding effect on boreal snow distributions; however, measurements characterizing boreal snow are sparse and focus within patches (vs. between patches). Unfortunately, remote sensing approaches in such forested areas frequently fall short due to coarse footprint size and dense canopy cover. Over the last several years we have been examining the characteristics of snow cover within and across boundaries in the boreal forest, seeking to identify gradients in snow depth due to snow-vegetation interactions as well identifying methods whereby boreal forest surveys could be improved. Specifically, we collected end-of-season snow measurements in the Alaska boreal forest during long-distance traverses in the Tanana Basin in 2010 (26 sites) and within the Yukon Flats National Wildlife Refuge in 2011 (26 sites). At each site (all relatively flat), hundreds of snow depths were collected using a GPS-equipped Magnaprobe, which is an automated tool for measuring and locating individual snow depths. Corresponding canopy properties included NDVI determined from high-resolution satellite imagery; canopy properties were variable among the 1ha sites and some areas had recently burned. Among sites, NDVI had the largest correlation with snow depths; elevation was not significant. Vegetation transition zones play important roles in explaining observed snow depth. Similar to treeline work showing nutrient and energy gradients are influenced by

  19. Silviculture for restoration of degraded temperate and boreal forests

    Science.gov (United States)

    John A. Stanturf; Palle Madsen; Emile S. Gardiner

    2004-01-01

    Throughout the temperate and boreal zones, human intervention has influenced landscapes and forests for millennia. The degree of human disturbance has only been constrained by the technology and resources available to different cultures and by time since initial habitation. Humans have influenced forests by regulating populations of browsers, clearing for agriculture,...

  20. NPP Multi-Biome: Grassland, Boreal Forest, and Tropical Forest Sites, 1939-1996, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains one data file (.csv format) that provides net primary productivity (NPP) estimates for 34 grasslands, 14 tropical forests, and 5 boreal forest...

  1. 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.

  2. Boreal Forest Biomass Classification with TanDEM-X

    Science.gov (United States)

    Torano Caicoya, Astor; Kugler, Florian; Hajnsek, Irena; Papathanassiou, Kostas

    2013-08-01

    High spatial resolution X-band interferometric SAR data from TanDEM-X acquired in the operational DEM generation mode are sensitive to forest structure and can therefore be used for thematic boreal forest classification. The interferometric coherence in absence of temporal decorrelation depends strongly on forest height and structure. Due to the rather homogenous structure of boreal forest, forest biomass can be derived from forest height, on the basis of allometric equations with sufficient accuracy and can therefore, be used for thematic classification applications. Two test sites in mid- and southern Sweden are investigated. A maximum of 4 biomass classes, up to 150 Mg/ha, for a single baseline scenario and 5 biomass classes up to 250 Mg/ha for a dual baseline scenario, are achieved.

  3. 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.

  4. The distribution of radioactive caesium in boreal forest ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, R. [National Defence Research Establishment, Dept. of NBC Defence, Umeaa (Sweden)

    1994-12-31

    The behaviour of radioactive caesium (Cs-134 and Cs-137) in boreal forests of the Nordic countries is reviewed with emphasis on its distribution in various time perspectives. The analysis has thus been focused on data of relevance for both early and later phases after fallout over forest areas. Possibilities and limitation in using data from other time periods or regions, than that characterised by fallout over the boreal zones after the Chernobyl event are also discussed. This concerns extrapolations from information pertaining to neighbouring ecological areas - at higher altitudes (alpine, and sub-alpine regions) or below the southern limit (i.e. in the hemiboreal and nemoboreal zones), and to future time with respect to predictions of the behaviour of Cs-137, based on results for OLD (i.e. from atmospheric weapons tests - mainly in the sixties) versus CHERNOBYL caesium. Beside the principal terrestrial constituents of the soil-plant-animal system, the BOREAL FOREST ECOSYSTEM will for the present purpose be considered to comprise the semi-aquatic and aquatic components pertaining to peat, open peat bog, and ground water. This implies that run-off from a catchment constitutes the main link between the terrestrial part considered here and the aquatic ecosystem proper. In boreal forests the humus layer usually retains a major fraction of the fallout of radioactive caesium, evidently even several decades after deposition. This notable feature, as well as a persistent high availability in important food-chains, emerges from the present Nordic radioecological research. Both constitute facets of a singularity conservative - although not at all static - situation prevailing for radioactive caesium in the boreal forest. The implication is that for Cs-137 physical decay will be the major factor of loss from the boreal ecosystem in a long-term perspective, and that runoff, particularly from peat bogs, is expected to be the second in order of importance. (orig./HP).

  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...

  6. 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...

  7. 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...

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

    Science.gov (United States)

    Chapin, F.S.; McGuire, A. David; 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.

  9. 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...

  10. 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.

  11. TALL-HERB BOREAL FORESTS ON NORTH URAL

    Directory of Open Access Journals (Sweden)

    A. A. Aleinikov

    2016-09-01

    Full Text Available Background. One of the pressing aims of today’s natural resource management is its re-orientation to preserving and restoring ecological functions of ecosystems, among which the function of biodiversity maintenance plays an indicator role. The majority of today’s forests have not retained their natural appearance as the result of long-standing human impact. In this connection, refugia studies are becoming particularly interesting, as they give us an insight into the natural appearance of forests. Materials and methods. Studies were performed in dark conifer forests of the Pechora–Ilych reserve, in the lower reaches of the Bol’shaya Porozhnyaya River in 2013 yr. Vegetation data sampling was done at 50 temporary square plots of a fixed size (100 m2 randomly placed within a forest type. A list of plant species with species abundance was made for each forest layer. The overstorey (or tree canopy layer was denoted by the Latin letter A. The understorey layer (indicated by the letter B included tree undergrowth and tall shrubs. Ground vegetation was subdivided into the layers C and D. Layer C (field layer comprised the herbaceous species (herbs, grasses, sedges and dwarf shrubs together with low shrubs, tree and shrub seedlings. The height of the field layer was defined by the maximal height of the herbaceous species, ferns, and dwarf shrubs; the height varied from several cm to more than 200 cm in the ‘tall-herb’ forest types. Layer D (bottom layer included cryptogamic species (bryophytes and lichens. Species abundance in the each layer was usually assessed using the Braun-Blanquet cover scale (Braun-Blanquet 1928. The nomenclature used follows Cherepanov’s (1995 for vascular plants, and Ignatov & Afonina’s (1992. Results. The present article contains descriptions of unique tall-herb boreal forests of European Russia preserved in certain refugia which did not experience prolonged anthropogenic impact or any other catastrophes

  12. Boreal forest albedo and its spatial and temporal variation

    OpenAIRE

    Kuusinen, Nea

    2014-01-01

    Surface albedo refers to the fraction of solar irradiance that is reflected by a surface. Accurate characterisation of the albedo of various land cover types is required for evaluating the energy exchange between the Earth s surface and the atmosphere. The optical and structural properties of a surface determine its albedo. Boreal forest albedo can vary due to factors such as tree species composition, forest structure, understorey vegetation composition, and seasonal changes in vegetation and...

  13. Carbon balance and climate change in boreal forests

    Energy Technology Data Exchange (ETDEWEB)

    Bhatti, J. S.; Laird, L. D.; Banfield, E. [Canadian Forest Service, Northern Forestry Centre, Edmonton, AB (Canada); Van Kooten, G. C. [Victoria Univ., Dept. of Economics, Victoria, BC (Canada); Apps, M. J. [Canadian Forest Service, Pacific Forestry Centre, Victoria, BC (Canada); Campbell, I. D. [Natural Resources Canada, Geological Survey of Canada, Ottawa, ON (Canada); Campbell, C. [Canadian Forest Service, Ottawa, ON (Canada); Turetsky, M. R. [U. S. Geological Survey, Western Region Center, Menlo Park, CA (United States); Yu, Z. [Lehigh Univ., Earth and Environmental Sciences, Bethlehem, PA (United States)

    2003-07-01

    Carbon is exchanged between terrestrial ecosystems and the atmosphere through photosynthesis, respiration, decomposition, and combustion, hence its importance to global climate. To explain that role, this chapter discusses the role of the boreal forest in the carbon cycle, the expected impacts of climate change on the boreal ecosystem, and the effects of various natural and human factors on the carbon balance of the forest. Economic and forest management issues in relation to carbon resources of the forest are also explored in light of the Kyoto Protocol commitments to reduce greenhouse gas emissions, along with challenges to sustainable forest management seen from the vantage point of climatic change. Among natural disasters, fire, infestation by insects and pathogens,storms, floods, and landslides receive attention, whereas in the area of human impacts attention is focused on land-use practices, and forest stand and landscape-level management. An overview of the Kyoto Protocol, Canada's commitments, the concepts of emissions trading, and carbon credits and the role of forestry, is provided. Other subjects explored include options for minimizing carbon emission in boreal forestry, and the economic impacts of adaptation to climate change on forestry. 245 refs., 5 tabs., 13 figs.

  14. Ecology of snowshoe hares in southern boreal and montane forests [Chapter 7

    Science.gov (United States)

    Karen E. Hodges

    2000-01-01

    Snowshoe hares occur in many of the montane and sub-boreal forests of the continental United States, as well as throughout the boreal forests of Canada and Alaska. Population dynamics in their southern range were previously thought to be noncyclic, in contrast to the strong 10-year fluctuation that typifies boreal populations of snowshoe hares. Time series data and...

  15. 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.

  16. Diverse growth trends and climate responses across Eurasia's boreal forest

    Czech Academy of Sciences Publication Activity Database

    Hellmann, L.; Agafonov, L.; Ljungqvist, F. C.; Churakova (Sidorova), O.; Duethorn, E.; Esper, J.; Hulsmann, L.; Kirdyanov, A. V.; Moiseev, P.; Myglan, V. S.; Nikolaev, A. N.; Reinig, F.; Schweingruber, F. H.; Solomina, O.; Tegel, W.; Büntgen, Ulf

    2016-01-01

    Roč. 11, č. 7 (2016), č. článku 074021. ISSN 1748-9326 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : 20th-century summer warmth * tree-ring chronology * scots pine * 2 millennia * temperature variability * northern-hemisphere * central siberia * worlds forest s * white spruce * carbon-cycle * boreal forest * climate variability * dendroecology * Eurasia * forest productivity * global warming * high northern latitudes Subject RIV: EH - Ecology, Behaviour Impact factor: 4.404, year: 2016

  17. 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...

  18. TCP Final Report: Measuring the Effects of Stand Age and Soil Drainage on Boreal Forest

    Energy Technology Data Exchange (ETDEWEB)

    Michael L. Goulden

    2007-05-02

    This was a 6-year research project in the Canadian boreal forest that focused on using field observations to understand how boreal forest carbon balance changes during recovery from catastrophic forest fire. The project began with two overarching goals: (1) to develop techniques that would all the year round operation of 7 eddy covariance sites in a harsh environment at a much lower cost than had previously been possible, and (2) to use these measurements to determine how carbon balance changes during secondary succession. The project ended in 2006, having accomplished its primary objectives. Key contributions to DOE during the study were: (1) Design, test, and demonstrate a lightweight, fully portable eddy flux system that exploits several economies of scale to allow AmeriFlux-quality measurements of CO{sub 2} exchange at many sites for a large reduction in cost (Goulden et al. 2006). (2) Added seven year-round sites to AmeriFlux, at a relatively low per site cost using the Eddy Covariance Mesonet approach (Goulden et al. 2006). These data are freely available on the AmeriFlux web site. (3) Tested and rejected the conventional wisdom that forests lose large amounts of carbon during the first decade after disturbance, then accumulate large amounts of carbon for {approx}several decades, and then return to steady state in old age. Rather, we found that boreal forests recovers quickly from fire and begins to accumulate carbon within {approx}5 years after disturbance. Additionally, we found no evidence that carbon accumulation declines in old stands (Goulden et al. 2006, Goulden et al. in prep). (4) Tested and rejected claims based on remote sensing observations (for example, Myneni et al 1996 using AVHRR) that regions of boreal forest have changed markedly in the last 20 years. Rather, we assembled a much richer data set than had been used in the past (eddy covariance observations, tree rings, biomass, NPP, AVHRR, and LandSat), which we used to establish that the

  19. Radar modeling of a boreal forest

    Science.gov (United States)

    Chauhan, Narinder S.; Lang, Roger H.; Ranson, K. J.

    1991-01-01

    Microwave modeling, ground truth, and SAR data are used to investigate the characteristics of forest stands. A mixed coniferous forest stand has been modeled at P, L, and C bands. Extensive measurements of ground truth and canopy geometry parameters were performed in a 200-m-square hemlock-dominated forest plot. About 10 percent of the trees were sampled to determine a distribution of diameter at breast height (DBH). Hemlock trees in the forest are modeled by characterizing tree trunks, branches, and needles as randomly oriented lossy dielectric cylinders whose area and orientation distributions are prescribed. The distorted Born approximation is used to compute the backscatter at P, L, and C bands. The theoretical results are found to be lower than the calibrated ground-truth data. The experiment and model results agree quite closely, however, when the ratios of VV to HH and HV to HH are compared.

  20. Evapotranspiration from understory vegetation in an eastern Siberian boreal larch forest, Agricultural and Forest Meteorology

    NARCIS (Netherlands)

    Iida, S.; Ohta, T.; Matsumoto, K.; Nakai, T.; Kuwada, T.; Konovov, A.V.; Maximov, T.C.; van der Molen, M.K.; Dolman, A.J.; Tanaka, H.; Yabuki, H.

    2009-01-01

    We measured evapotranspiration in an eastern Siberian boreal forest, in which the understory was cowberry and the overstory was larch, during the entire growing seasons of 2005 and 2006. We compared evapotranspiration from the understory vegetation above the forest floor E

  1. 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.

  2. 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.

  3. Pennsylvania boreal conifer forests and their bird communities: past, present, and potential

    Science.gov (United States)

    Douglas A. Gross

    2010-01-01

    Pennsylvania spruce (Picea spp.)- and eastern hemlock (Tsuga canadensis)-dominated forests, found primarily on glaciated parts of the Allegheny Plateau, are relicts of boreal forest that covered the region following glacial retreat. The timber era of the late 1800s and early 1900s (as late as 1942) destroyed most of the boreal...

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    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 and inorganic compounds......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. Trace gas emissions from chaparral and boreal forest fires

    Science.gov (United States)

    Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Winstead, Edward L.; Riggan, Philip J.; Stocks, Brian J.; Brass, James A.; Ambrosia, Vincent G.

    1989-01-01

    Using smoke samples collected during low-level helicopter flights, the mixing ratios of CO2, CO, CH4, total nonmethane hydrocarbons, H2, and N2O over burning chaparral in southern California and over a burning boreal forest site in northern Ontario, Canada, were determined. Carbon dioxide-normalized emission ratios were determined for each trace gas for conditions of flaming, mixed, and smoldering combustion. The emission ratios for these trace gases were found to be highest for the smoldering combustion, generally thought to be the least efficient combustion stage. However, high emission ratios for these gases could be also produced during very vigorous flaming combustion.

  6. 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

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

    OpenAIRE

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

    2016-01-01

    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...

  8. 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.

  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. Antioxidant Potential of Bark Extracts from Boreal Forest Conifers

    Science.gov (United States)

    Legault, Jean; Girard-Lalancette, Karl; Dufour, Dominic; Pichette, André

    2013-01-01

    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. PMID:26784337

  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. Influence of the forest canopy on total and methyl mercury deposition in the boreal forest

    Science.gov (United States)

    E.L. Witt; R.K. Kolka; E.A. Nater; T.R. Wickman

    2009-01-01

    Atmospheric mercury deposition by wet and dry processes contributes mercury to terrestrial and aquatic systems. Factors influencing the amount of mercury deposited to boreal forests were identified in this study. Throughfall and open canopy precipitation samples were collected in 2005 and 2006 using passive precipitation collectors from pristine sites located across...

  13. The effects of boreal forest expansion on the summer Arctic frontal zone

    Energy Technology Data Exchange (ETDEWEB)

    Liess, Stefan; Snyder, Peter K.; Harding, Keith J. [University of Minnesota, Department of Soil, Water, and Climate, Saint Paul, MN (United States)

    2012-05-15

    Over the last 100 years, Arctic warming has resulted in a longer growing season in boreal and tundra ecosystems. This has contributed to a slow northward expansion of the boreal forest and a decrease in the surface albedo. Corresponding changes to the surface and atmospheric energy budgets have contributed to a broad region of warming over areas of boreal forest expansion. In addition, mesoscale and synoptic scale patterns have changed as a result of the excess energy at and near the surface. Previous studies have identified a relationship between the positioning of the boreal forest-tundra ecotone and the Arctic frontal zone in summer. This study examines the climate response to hypothetical boreal forest expansion and its influence on the summer Arctic frontal zone. Using the Weather Research and Forecasting model over the Northern Hemisphere, an experiment was performed to evaluate the atmospheric response to expansion of evergreen and deciduous boreal needleleaf forests into open shrubland along the northern boundary of the existing forest. Results show that the lower surface albedo with forest expansion leads to a local increase in net radiation and an average hemispheric warming of 0.6 C at and near the surface during June with some locations warming by 1-2 C. This warming contributes to changes in the meridional temperature gradient that enhances the Arctic frontal zone and strengthens the summertime jet. This experiment suggests that continued Northern Hemisphere high-latitude warming and boreal forest expansion might contribute to additional climate changes during the summer. (orig.)

  14. Methane exchange in a boreal forest estimated by gradient method

    Directory of Open Access Journals (Sweden)

    Elin Sundqvist

    2015-07-01

    Full Text Available Forests are generally considered to be net sinks of atmospheric methane (CH4 because of oxidation by methanotrophic bacteria in well-aerated forests soils. However, emissions from wet forest soils, and sometimes canopy fluxes, are often neglected when quantifying the CH4 budget of a forest. We used a modified Bowen ratio method and combined eddy covariance and gradient methods to estimate net CH4 exchange at a boreal forest site in central Sweden. Results indicate that the site is a net source of CH4. This is in contrast to soil, branch and leaf chamber measurements of uptake of CH4. Wetter soils within the footprint of the canopy are thought to be responsible for the discrepancy. We found no evidence for canopy emissions per se. However, the diel pattern of the CH4 exchange with minimum emissions at daytime correlated well with gross primary production, which supports an uptake in the canopy. More distant source areas could also contribute to the diel pattern; their contribution might be greater at night during stable boundary layer conditions.

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

    Science.gov (United States)

    Girardin, Martin P.; 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

    2016-01-01

    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. PMID:27956624

  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. Modeling the Response of Boreal Forest Expansion on the Summer Arctic Frontal Zone

    Science.gov (United States)

    Liess, S.; Snyder, P. K.; Harding, K. J.

    2010-12-01

    Arctic warming over the last 100 years has resulted in a longer growing season in boreal and tundra ecosystems, especially during summertime. This has led to a northward expansion of the boreal forest and a decrease in the surface albedo. Corresponding changes to the surface and atmospheric energy budgets have generally contributed to a broad region of warming over areas where boreal forest has expanded into tundra. Mesoscale and synoptic scale dynamics are likewise affected. Previous studies have identified a relationship between the positioning of the boreal forest-tundra ecotone and the Arctic frontal zone in summer. This study focuses on the effects of boreal forest expansion on the summer Arctic frontal zone when albedo differences between tundra and boreal forest are at a maximum. The Arctic climate during the month of June was simulated with the WRF regional model coupled to the NOAH land surface model with 30 km horizontal resolution over the polar stereographic domain north of 50°N. The current distribution of vegetation is based on a recent MODIS-derived land cover data set. Two sets of experiments were conducted. One control experiment with observed land cover, and one sensitivity experiment where all grid points classified as open shrubland north of the boreal forest were replaced with either evergreen or deciduous boreal needleleaf forest depending on the type of boreal forest presently located south of a given open shrubland location. Both the boreal expansion and control simulations consist of 13 ensemble members. Results show a significant increase in storm track activity over areas with expanded boreal forest and to the north, where the increase in the meridional temperature gradient is strongest, particularly in eastern Russia, and eastern North America. A blocking high over eastern Russia contributes to a northward shift in the jet stream over this area. Storm track activity also increases over northern Europe and central Russia to the south of

  18. 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.

  19. Structuring Effects of Deer in Boreal Forest Ecosystems

    Directory of Open Access Journals (Sweden)

    Steeve D. Côté

    2014-01-01

    Full Text Available Many deer populations have recently increased worldwide leading to strong direct and indirect ecological and socioeconomical impacts on the composition, dynamic, and functions of forest ecosystems. Deer directly modify the composition and structure of vegetation communities, but they also indirectly affect other species of the ecosystem by modifying the structure of the vegetation. Here we review the results of a research program on overabundant white-tailed deer (Odocoileus virginianus in the boreal forest of Anticosti Island (Québec, Canada aimed at identifying deer densities compatible with forest regeneration. Various silvicultural systems and treatments failed to regenerate deer habitat at high deer densities, but planting size-adapted seedlings could be effective at moderate densities. Using a controlled deer density experiment, we found vegetation recovery at deer densities ≤ 15 deer/km2. The same experiment revealed that other groups of organisms such as insects and birds responded favorably to a reduction of deer density. We also found that alternative successional trajectories may occur after a certain period of heavy browsing during early succession. We conclude that one of the most important remaining research gaps is the need to identify habitat-specific threshold densities at which deer impacts occur and then to design effective wildlife and forest management strategies to limit deer impacts and sustain ecosystem integrity.

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

    Directory of Open Access Journals (Sweden)

    Marjo Palviainen

    Full Text Available 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.

  1. Modelling boreal forest CO{sub 2} exchange and seasonality

    Energy Technology Data Exchange (ETDEWEB)

    Thum, T.

    2009-07-01

    Man-induced climate change has raised the need to predict the future climate and its feedback to vegetation. These are studied with global climate models; to ensure the reliability of these predictions, it is important to have a biosphere description that is based upon the latest scientific knowledge. This work concentrates on the modelling of the CO{sub 2} exchange of the boreal coniferous forest, studying also the factors controlling its growing season and how these can be used in modelling. In addition, the modelling of CO{sub 2} gas exchange at several scales was studied. A canopy-level CO{sub 2} gas exchange model was developed based on the biochemical photosynthesis model. This model was first parameterized using CO{sub 2} exchange data obtained by eddy covariance (EC) measurements from a Scots pine forest at Sodankylae. The results were compared with a semi-empirical model that was also parameterized using EC measurements. Both of the models gave satisfactory results. The biochemical canopy-level model was further parameterized at three other coniferous forest sites located in Finland and Sweden. At all the sites, the two most important biochemical model parameters showed seasonal behaviour, i.e., their temperature responses changed according to the season. Modelling results were improved when these changeover dates were related to temperature indices. During summer-time the values of the biochemical model parameters were similar at all the four sites. Different control factors for CO{sub 2} gas exchange were studied at the four coniferous forests, including how well these factors can be used to predict the initiation and cessation of the CO{sub 2} uptake. Temperature indices, atmospheric CO{sub 2} concentration, surface albedo and chlorophyll fluorescence (CF) were all found to be useful and have predictive power. In Finnish Lapland a trend toward an earlier start of the CO{sub 2} uptake in spring was also observed. In addition, a detailed simulation study

  2. 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.

  3. 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.

  4. 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

  5. Disturbance in boreal forest ecosystems: human impacts and natural processes. Proceedings of the International Boreal Forest Research Association 1997 annual meeting; 1997 August 4-7; Duluth, Minnesota.

    Science.gov (United States)

    Susan G. Conard

    2000-01-01

    The papers in these proceedings cover a wide range of topics related to human and natural disturbance processes in forests of the boreal zone in North America and Eurasia. Topics include historic and predicted landscape change; forest management; disturbance by insects, fire, air pollution, severe weather, and global climate change; and carbon cycling.

  6. BOREAS (Boreal Ecosystem-Atmosphere Study): Global change and biosphere-atmosphere interactions in the boreal forest

    Science.gov (United States)

    Sellers, Piers J.

    1991-01-01

    The Boreal Ecosystems Atmosphere Study (BOREAS) is a cooperative field and analysis project involving elements of land surface climatology, tropospheric chemistry, and terrestrial ecology. The goal of the study is to understand the interactions between the boreal forest biome and the atmosphere in order to clarify their roles in global change. The study will be centered on two 20 by 20 km sites within the North American boreal forest region, located near the northern and southern limits of the biome. Studies based at these sites will be used to explore the roles of various environmental factors in controlling the extent and character of the biome. The sites will be the subject of surface, airborne, and satellite based observations which aim to improve understanding of the biological and physical processes and states which govern the exchanges of energy, water, carbon, and trace gases between boreal forest ecosystems and the atmosphere. Particular reference will be made to those processes and states that may be sensitive to global change. The study also aims to develop the use of remote sensing techniques to transfer understanding of the above process from local scales out to regional scales. The BOREAS project is being planned for 1992-1996, with a major field effort in 1994.

  7. 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

    Climate change appears to be altering boreal forests. One recently observed symptom of these changes has been an apparent weakening of the positive relationship between high-latitude boreal tree growth and temperature at some sites (D'Arrigo et al 2008). This phenomenon is referred to as the 'divergence problem' or 'divergence effect' and is thought to reflect a non-linear relationship between temperature and tree growth, where recent warming has allowed other factors besides growing-season temperature to emerge as dominant regulators of annual growth rates. Figure 1 demonstrates this divergence phenomenon with records of tree-ring widths collected from 59 populations of white spruce in Alaska 1. Key tendencies among these populations include: (1) growth is most sensitive to temperature during relatively cold growing seasons (figure 1(a)), (2) populations at colder sites are more sensitive to temperature than those at warmer sites are (figure 1(a)), and (3) growth at warmer sites may respond negatively to increased temperature beyond some optimal growing-season temperature (figure 1(b)). Since temperature is rising rapidly at high latitudes, one interpretation of figures 1(a) and (b) is that warming has promoted increased growth at colder sites, but caused growth to plateau or slow at warmer sites. Corroborating this interpretation, satellite imagery and tree-ring data indicate increasing vegetation productivity near the forest-tundra boundary but declining productivity in warmer regions within forest interiors (e.g., Bunn and Goetz 2006, Beck and Goetz 2011, Beck et al 2011, Berner et al 2011). Will continued warming cause a northward migration of boreal forests, with mortality in the warmer, southern locations and expansion into the colder tundra? This question is difficult to answer because many factors besides temperature influence boreal forest dynamics. Widespread productivity declines within interior boreal forests appear to be related to warming

  8. 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.

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

    Directory of Open Access Journals (Sweden)

    Paul D Pickell

    Full Text Available 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.

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

    National Research Council Canada - National Science Library

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

    2016-01-01

    .... 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...

  13. Russian Boreal Forest Disturbance Maps Derived from Landsat Imagery, 1984-2000

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides Boreal forest disturbance maps at 30-m resolution for 55 selected sites across Northern Eurasia within the Russian Federation. Disturbance...

  14. Fire Intensity and Burn Severity Metrics for Circumpolar Boreal Forests, 2001-2013

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides products characterizing immediate and longer-term ecosystem changes from fires in the circumpolar boreal forests of Northern Eurasia and North...

  15. The changing effects of Alaska's boreal forests on the climate system

    Energy Technology Data Exchange (ETDEWEB)

    Euskirchen, E.S.; Chapin, F.S. III [Alaska Univ., Fairbanks, AK (United States). Dept. of Biology, Inst. of Arctic Biology; McGuire, A.D. [United Sates Geological Survey, Fairbanks, AK (United States). Alaska Cooperative Fish and Wildlife Research Unit; Alaska Univ., Fairbanks, AK (United States); Rupp, T.S. [Alaska Univ., Fairbanks, AK (United States). Dept. of Forest Sciences

    2010-07-15

    The boreal forest is the northernmost forested biome and is expected to be sensitive to global warming. Recent climate warming in the boreal forests of Alaska has influenced the exchange of trace gases, water, and energy between the forests and the atmosphere. In turn, these changes in the structure and function of boreal forests can influence regional and global climates. This study examined the type and magnitude of the climate feedbacks from boreal forests in Alaska. Biogeophysical and biogeochemical feedbacks were examined with particular reference to surface energy balance across boreal ecosystems and over the full annual cycle. The impact of ground heat exchange on permafrost was studied in terms of vegetation dynamics and disturbance regimes such as fires and insect outbreaks. In general, research has indicated that the net effect of a warming climate is a positive regional feedback to warming. The main positive climate feedbacks are currently 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 dominant at the regional scale and reduce the resilience of the boreal vegetation by amplifying the rate of regional warming. This paper also described carbon and methane release from permafrost degradation, changes in lake area, changes in land use and snow season changes. The role of earth system models in representing climate feedbacks from Alaskan boreal forests was discussed. It was concluded that although the boreal forest provides climate regulation as an ecosystem service, the net effect of the climate feedbacks to climate warming are not fully understood. As such, there is a need to continue to evaluate feedback pathways, given the recent warming in Alaska and the large variety of associated mechanisms that can change terrestrial ecosystems and affect the climate system. 59 refs

  16. 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

    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....... While the ecosystem now loses N, the long-term fate of soil N is a key uncertainty in predicting the future response of boreal ecosystems to climate change....

  17. Indirect effects of rodents on arthropods in a Scandinavian boreal forest

    OpenAIRE

    Malá, Barbora

    2016-01-01

    Rodents in boreal forest are an important component of food webs. Their role as drivers of the boreal forest ecosystem is debated. As herbivores they affect plant communities and alter qualities of plants. Consequently availability of food resources for other herbivorous species is altered. In my thesis I studied whether rodents indirectly influence communities of arthropods via plant resources. It is assumed that phytophagous arthropods respond to changes in plant resources by different feed...

  18. 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.

  19. Summary and synthesis: past and future changes in the Alaskan Boreal Forest.

    Science.gov (United States)

    F. Stuart Chapin; David McGuire; Roger W. Ruess; Marilyn W. Walker; Richard D. Boone; Mary E. Edwards; Bruce P. Finney; Larry D. Hinzman; Jeremy B. Jones; Glenn P. Juday; Eric S. Kasischke; Knut Kielland; Andrea H. Lloyd; Mark W. Oswood; Chien-Lu Ping; Eric Rexstad; Vladimir E. Romanovsky; Joshua P. Schimel; Elena B. Sparrow; Bjartmar Sveinbjörnsson; David W. Valentine; Keith Van Cleve; David L. Verbyla; Leslie A. Viereck; Richard A. Werner; Tricia L. Wurtz; John. Yarie

    2006-01-01

    Historically the boreal forest has experienced major changes, and it remains a highly dynamic biome today. During cold phases of Quaternary climate cycles, forests were virtually absent from Alaska, and since the postglacial re-establishment of forests ca 13,000 years ago, here have been periods of both relative stability and rapid change (Chapter 5). Today, the...

  20. Modeling impacts of fire severity on successional trajectories and future fire behavior in Alaskan boreal forests

    Science.gov (United States)

    Jill F. Johnstone; T. Scott Rupp; Mark Olson; David. Verbyla

    2011-01-01

    Much of the boreal forest in western North America and Alaska experiences frequent, stand-replacing wildfires. Secondary succession after fire initiates most forest stands and variations in fire characteristics can have strong effects on pathways of succession. Variations in surface fire severity that influence whether regenerating forests are dominated by coniferous...

  1. Restoration Concepts for Temperate and Boreal Forests of North America and Western Europe

    Science.gov (United States)

    John A. Stanturf; P. Madsen

    2002-01-01

    Throughout the boreal and temperate zones, forest restoration efforts attempt to counteract negative effects of conversion to other land use (afforestation and remediation) and disturbance and stress on existing forests (rehabilitation). Appropriate silvicultural practices can be designed for any forest restoration objective. Most common objectives include timber,...

  2. Decomposition of soil organic matter from boreal black spruce forest: environmental and chemical controls

    Science.gov (United States)

    Kimberly P. Wickland; Jason C. Neff

    2007-01-01

    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...

  3. 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.

  4. A Passive Microwave L-Band Boreal Forest Freeze/Thaw and Vegetation Phenology Study

    Science.gov (United States)

    Roy, A.; Sonnentag, O.; Pappas, C.; Mavrovic, A.; Royer, A.; Berg, A. A.; Rowlandson, T. L.; Lemay, J.; Helgason, W.; Barr, A.; Black, T. A.; Derksen, C.; Toose, P.

    2016-12-01

    The boreal forest is the second largest land biome in the world and thus plays a major role in the global and regional climate systems. The extent, timing and duration of seasonal freeze/thaw (F/T) state influences vegetation developmental stages (phenology) and, consequently, constitute an important control on how boreal forest ecosystems exchange carbon, water and energy with the atmosphere. The effective retrieval of seasonal F/T state from L-Band radiometry was demonstrated using satellite mission. However, disentangling the seasonally differing contributions from forest overstory and understory vegetation, and the soil surface to the satellite signal remains challenging. Here we present initial results from a radiometer field campaign to improve our understanding of the L-Band derived boreal forest F/T signal and vegetation phenology. Two L-Band surface-based radiometers (SBR) are installed on a micrometeorological tower at the Southern Old Black Spruce site in central Saskatchewan over the 2016-2017 F/T season. One radiometer unit is installed on the flux tower so it views forest including all overstory and understory vegetation and the moss-covered ground surface. A second radiometer unit is installed within the boreal forest overstory, viewing the understory and the ground surface. The objectives of our study are (i) to disentangle the L-Band F/T signal contribution of boreal forest overstory from the understory and ground surface, (ii) to link the L-Band F/T signal to related boreal forest structural and functional characteristics, and (iii) to investigate the use of the L-Band signal to characterize boreal forest carbon, water and energy fluxes. The SBR observations above and within the forest canopy are used to retrieve the transmissivity (γ) and the scattering albedo (ω), two parameters that describe the emission of the forest canopy though the F/T season. These two forest parameters are compared with boreal forest structural and functional

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

    OpenAIRE

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

    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. 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 man...

  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. The effects of boreal forest expansion on the summer Arctic frontal zone

    Science.gov (United States)

    Liess, Stefan; Snyder, Peter K.; Harding, Keith J.

    2012-05-01

    Over the last 100 years, Arctic warming has resulted in a longer growing season in boreal and tundra ecosystems. This has contributed to a slow northward expansion of the boreal forest and a decrease in the surface albedo. Corresponding changes to the surface and atmospheric energy budgets have contributed to a broad region of warming over areas of boreal forest expansion. In addition, mesoscale and synoptic scale patterns have changed as a result of the excess energy at and near the surface. Previous studies have identified a relationship between the positioning of the boreal forest-tundra ecotone and the Arctic frontal zone in summer. This study examines the climate response to hypothetical boreal forest expansion and its influence on the summer Arctic frontal zone. Using the Weather Research and Forecasting model over the Northern Hemisphere, an experiment was performed to evaluate the atmospheric response to expansion of evergreen and deciduous boreal needleleaf forests into open shrubland along the northern boundary of the existing forest. Results show that the lower surface albedo with forest expansion leads to a local increase in net radiation and an average hemispheric warming of 0.6°C at and near the surface during June with some locations warming by 1-2°C. This warming contributes to changes in the meridional temperature gradient that enhances the Arctic frontal zone and strengthens the summertime jet. This experiment suggests that continued Northern Hemisphere high-latitude warming and boreal forest expansion might contribute to additional climate changes during the summer.

  9. Overstory influences on light attenuation patterns and understory plant community diversity and composition in southern boreal forests of Quebec

    National Research Council Canada - National Science Library

    Bartemucci, Paula; Messier, Christian; Canham, Charles D

    2006-01-01

    We have characterized overstory light transmission, understory light levels, and plant communities in mixed wood boreal forests of northwestern Quebec with the objective of understanding how overstory...

  10. 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

  11. 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...... on SOC stocks in boreal and northern temperate forest ecosystems, which is in any case species-, site- and practice-specific. Properly conducted long-term experiments are therefore necessary to enable us to clarify the relative importance of different harvesting practices on the SOC stores, the key...

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

    Directory of Open Access Journals (Sweden)

    Adriana L Romero-Olivares

    Full Text Available 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.

  13. 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

  14. Observations of ozone depletion events in a Finnish boreal forest

    Directory of Open Access Journals (Sweden)

    X. Chen

    2018-01-01

    Full Text Available We investigated the concentrations and vertical profiles of ozone over a 20-year period (1996–2016 at the SMEAR II station in southern Finland. Our results showed that the typical daily median ozone concentrations were in the range of 20–50 ppb with clear diurnal and annual patterns. In general, the profile of ozone concentrations illustrated an increase as a function of heights. The main aim of our study was to address the frequency and strength of ozone depletion events at this boreal forest site. We observed more than a thousand of 10 min periods at 4.2 m, with ozone concentrations below 10 ppb, and a few tens of cases with ozone concentrations below 2 ppb. Among these observations, a number of ozone depletion events that lasted for more than 3 h were identified, and they occurred mainly in autumn and winter months. The low ozone concentrations were likely related to the formation of a low mixing layer under the conditions of low temperatures, low wind speeds, high relative humidities and limited intensity of solar radiation.

  15. 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.

  16. Observations of ozone depletion events in a Finnish boreal forest

    Science.gov (United States)

    Chen, Xuemeng; Quéléver, Lauriane L. J.; Fung, Pak L.; Kesti, Jutta; Rissanen, Matti P.; Bäck, Jaana; Keronen, Petri; Junninen, Heikki; Petäjä, Tuukka; Kerminen, Veli-Matti; Kulmala, Markku

    2018-01-01

    We investigated the concentrations and vertical profiles of ozone over a 20-year period (1996-2016) at the SMEAR II station in southern Finland. Our results showed that the typical daily median ozone concentrations were in the range of 20-50 ppb with clear diurnal and annual patterns. In general, the profile of ozone concentrations illustrated an increase as a function of heights. The main aim of our study was to address the frequency and strength of ozone depletion events at this boreal forest site. We observed more than a thousand of 10 min periods at 4.2 m, with ozone concentrations below 10 ppb, and a few tens of cases with ozone concentrations below 2 ppb. Among these observations, a number of ozone depletion events that lasted for more than 3 h were identified, and they occurred mainly in autumn and winter months. The low ozone concentrations were likely related to the formation of a low mixing layer under the conditions of low temperatures, low wind speeds, high relative humidities and limited intensity of solar radiation.

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

    Science.gov (United States)

    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. PMID:28622366

  18. Climate change implications of shifting forest management strategy in a boreal forest ecosystem of Norway.

    Science.gov (United States)

    Bright, Ryan M; Antón-Fernández, Clara; Astrup, Rasmus; Cherubini, Francesco; Kvalevåg, Maria; Strømman, Anders H

    2014-02-01

    Empirical models alongside remotely sensed and station measured meteorological observations are employed to investigate both the local and global direct climate change impacts of alternative forest management strategies within a boreal ecosystem of eastern Norway. Stand-level analysis is firstly executed to attribute differences in daily, seasonal, and annual mean surface temperatures to differences in surface intrinsic biophysical properties across conifer, deciduous, and clear-cut sites. Relative to a conifer site, a slight local cooling of −0.13 °C at a deciduous site and −0.25 °C at a clear-cut site were observed over a 6-year period, which were mostly attributed to a higher albedo throughout the year. When monthly mean albedo trajectories over the entire managed forest landscape were taken into consideration, we found that strategies promoting natural regeneration of coniferous sites with native deciduous species led to substantial global direct climate cooling benefits relative to those maintaining current silviculture regimes – despite predicted long-term regional warming feedbacks and a reduced albedo in spring and autumn months. The magnitude and duration of the cooling benefit depended largely on whether management strategies jointly promoted an enhanced material supply over business-as-usual levels. Expressed in terms of an equivalent CO2 emission pulse at the start of the simulation, the net climate response at the end of the 21st century spanned −8 to −159 Tg-CO2-eq., depending on whether near-term harvest levels increased or followed current trends, respectively. This magnitude equates to approximately −20 to −300% of Norway's annual domestic (production) emission impact. Our analysis supports the assertion that a carbon-only focus in the design and implementation of forest management policy in boreal and other climatically similar regions can be counterproductive – and at best – suboptimal if boreal forests are to be used as a

  19. Ground vegetation reduces forest floor net CH4 uptake in a boreal upland forest

    Science.gov (United States)

    Pihlatie, Mari; Kieloaho, Antti-Jussi; Halmeenmäki, Elisa; Ryhti, Kira; Heinonsalo, Jussi

    2017-04-01

    Boreal upland forests are considered as an important sink for the greenhouse gas methane (CH4) due to CH4 oxidizing microbes in the soil. Recent studies have reported significant CH4 emissions from trees in both upland and wetland forests, however, contribution of ground vegetation to the net CH4 exchange has not been assessed. As the processes and process drivers of the CH4 emissions from vegetation are still poorly understood, partitioning the CH4 exchange in forest ecosystems to soil, ground vegetation and trees is a way to improve our understanding of the CH4 cycling processes in forest ecosystems. We measured the forest floor CH4 exchange at a Scots pine dominated boreal upland forest in Southern Finland (SMEAR II station) during the growing season 2015. The forest floor consisted of mostly shrubs of bilberry (Vaccinium myrtillus), lingonberry (Vaccinium vitis-idaea), heather (Calluna vulgaris), and forest floor mosses (Pleurozium schreberi, Hylocomium splendens, and Dicranum polysetum). We measured the CH4 fluxes using transparent chambers under three vegetation treatments: normal vegetation (normal), shrubs only (shrubs), and non-vegetated (cut), and under three soil trenching treatments: control, 50 μm mesh (roots of trees and shrubs excluded), and 1 μm mesh (roots of trees and shrubs, and microbes excluded). Forest floor acted as a sink of CH4 in all the vegetation and trenching treatments. Presence of ground layer vegetation significantly reduced the forest floor CH4 uptake, whereas soil trenching did not affect the CH4 exchange. Over the period of May - October 2015, the mean forest floor CH4 fluxes were -53.7 (± 3.1 SE), -96.7 (± 3.7), and -91.4 (± 4.3) μg CH4 m2 h-1 from normal, shrubs and cut treatments, respectively. The presence of ground vegetation hence nearly halved the forest floor CH4 uptake compared to the shrubs only and cut treatments. As the largest difference between normal and shrubs treatments were the absence of mosses, our

  20. 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.

  1. 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.

  2. 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.

  3. Carbon dioxide and water vapour exchange from understory species in boreal forest.

    NARCIS (Netherlands)

    Heijmans, M.M.P.D.; Arp, W.J.; Chapin, F.S.

    2004-01-01

    Although recent eddy covariance measurements in boreal forests provide CO2 and energy exchange data for the whole ecosystem, very little is known about the role of the understory vegetation. We conducted chamber flux measurements in an Alaskan black spruce forest in order to compare CO2 and water

  4. 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

  5. Simulating restoration strategies for a southern boreal forest landscape with complex land ownership patterns

    Science.gov (United States)

    Douglas J. Shinneman; Meredith W. Cornett; Brian J. Palik

    2010-01-01

    Restoring altered forest landscapes toward their ranges of natural variability (RNV) may enhance ecosystem sustainability and resiliency, but such efforts can be hampered by complex land ownership and management patterns. We evaluated restoration potential for southern-boreal forests in the ~2.1 million ha Border Lakes Region of northern Minnesota (U.S.A.) and...

  6. Quantifying the effect of fuel reduction treatments on fire behavior in boreal forests

    Science.gov (United States)

    B.W. Butler; R.D. Ottmar; T.S. Rupp; R. Jandt; E. Miller; K. Howard; R. Schmoll; S. Theisen; R.E. Vihnanek; D. Jimenez

    2013-01-01

    Mechanical (e.g., shearblading) and manual (e.g., thinning) fuel treatments have become the preferred strategy of many fire managers and agencies for reducing fire hazard in boreal forests. This study attempts to characterize the effectiveness of four fuel treatments through direct measurement of fire intensity and forest floor consumption during a single prescribed...

  7. Saproxylic beetles in a Swedish boreal forest landscape managed according to 'new forestry'

    Science.gov (United States)

    Stig Larsson; Barbara Ekbom; L. Martin Schroeder; Melodie A. McGeoch

    2006-01-01

    A major threat to biodiversity in Swedish forests is the decline of Coarse Woody Debris (CWD), which is an essential resource for many organisms and plays an essential role for the structure and function of boreal forests. Removal of CWD in commercial forestry has depleted important resources for many rare wood-living (saproxylic) beetles. Replenishment of CWD has been...

  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. Scale-dependent controls on the area burned in the boreal forest of Canada, 1980-2005.

    Science.gov (United States)

    Parisien, Marc-André; Parks, Sean A; Krawchuk, Meg A; Flannigan, Mike D; Bowman, Lynn M; Moritz, Max A

    2011-04-01

    In the boreal forest of North America, as in any fire-prone biome, three environmental factors must coincide for a wildfire to occur: an ignition source, flammable vegetation, and weather that is conducive to fire. Despite recent advances, the relative importance of these factors remains the subject of some debate. The aim of this study was to develop models that identify the environmental controls on spatial patterns in area burned for the period 1980-2005 at several spatial scales in the Canadian boreal forest. Boosted regression tree models were built to relate high-resolution data for area burned to an array of explanatory variables describing ignitions, vegetation, and long-term patterns in fire-conducive weather (i.e., fire climate) at four spatial scales (10(2) km2, 10(3) km2, 10(4) km2, and 10(5) km2). We evaluated the relative contributions of these controls on area burned, as well as their functional relationships, across spatial scales. We also assessed geographic patterns of the influence of wildfire controls. The results indicated that extreme temperature during the fire season was a top control at all spatial scales, followed closely by a wind-driven index of ease of fire spread. However, the contributions of some variables differed substantially among the spatial scales, as did their relationship to area burned. In fact, for some key variables the polarity of relationships was inverted from the finest to the broadest spatial scale. It was difficult to unequivocally attribute values of relative importance to the variables chosen to represent ignitions, vegetation, and climate, as the interdependence of these factors precluded clear partitioning. Furthermore, the influence of a variable on patterns of area burned often changed enormously across the biome, which supports the idea that fire-environment relationships in the boreal forest are complex and nonstationary.

  10. 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.

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

    Science.gov (United States)

    Euskirchen, E.S.; McGuire, A. David; 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.

  12. Resilience of Alaska's boreal forest to climatic change

    Energy Technology Data Exchange (ETDEWEB)

    Chapin, F.S. III; Ruess, R.W.; Euskirchen, E.S.; Jones, J.B.; Kielland, K.; Taylor, D.L. [Alaska Univ., Fairbanks, AK (United States). Dept. of Biology, Inst. of Arctic Biology; McGuire, A.D. [United Sates Geological Survey, Fairbanks, AK (United States). Alaska Cooperative Fish and Wildlife Research Unit; Alaska Univ., Fairbanks, AK (United States); Hollingsworth, T.N. [United States Dept. of Agriculture, Portland, OR (United States). Forest Services, Pacific Northwest Research Station; Alaska Univ., Fairbanks, AK (United States); Mack, M.C. [Florida Univ., Gainesville, FL (United States). Dept. of Botany; Johnstone, J.F. [Saskatchewan Univ., Saskatoon, SK (Canada). Dept. of Biology; Kasischke, E.S. [Maryland Univ., College Park, MD (United States). Dept. of Geography; Jorgenson, M.T. [Alaska Ecoscience, Fairbanks, AK (United States); Kofinas, G.P. [Alaska Univ., Fairanks, AK (United States). School of Natural Resources and Agricultureal Sciences, Inst. of Arctic Biology; Turetsky, M.R. [Guelph Univ., Guelph, ON (Canada). Dept. of Integrative Biology; Yarie, J. [Alaska Univ., Fairbanks, AK (United States). Dept. of Forest Sciences, Forest Soils Laboratory; Lloyd, A.H. [Middlebury College, Middlebury, VT (United States). Dept. of Biology

    2010-07-15

    This paper reported on a study that evaluated the resilience of Alaska's boreal forest system to rapid climatic change. As the most northern and coldest forested biome, the boreal forest is underlain by discontinuous permafrost. High-latitude amplification of global warming has caused Alaska's boreal forest to warm twice as rapidly as the global average. Recent warming has resulted in reduced growth of dominant tree species, plant disease, insect outbreaks, thawing of permafrost, drying of lakes and increased wildfires. These changes have modified key structural features in the boreal forest, including long-term landscape-scale change in carbon stocks. This study reviewed the findings of the Bonanza Creek Long-Term Ecological Research program and determined that the Alaskan boreal system remains quite resilient but is undergoing changes in ecosystem and landscape structure, feedbacks, and interactions that, with continued warming, will likely cause reorganization or potentially transformation to a fundamentally different system. Permafrost will also remain relatively resilient to continued warming except in high-ice-content lowlands and in areas burned by severe wildfires. The greatest sources of uncertainty are changes in snow cover, which will influence the rate at which these changes occur. 71 refs., 2 figs.

  13. Mechanisms of Action of Indigenous Antidiabetic Plants from the Boreal Forest of Northeastern Canada

    Directory of Open Access Journals (Sweden)

    Hoda M. Eid

    2014-01-01

    Full Text Available Indigenous populations in Canada possess a wealth of native traditional knowledge. However, their rates of Type 2 diabetes mellitus (T2DM, a disease that was unheard of in their midst 50 years ago, are the highest in the country. In an effort to cut the impact of T2DM epidemic on Indigenous health, the Canadian Institutes of Health Research funded the “CIHR Team in Aboriginal Antidiabetic Medicines (CIHR-TAAM.” The goal was to explore Boreal forest medicinal plants stemming from Indigenous Traditional Medicine to be included in T2DM care. Six out of nine communities of the Cree of Eeyou Istchee (CEI participated in ethnobotanical studies that resulted in the identification of 17 potential antidiabetic plant species. These species were screened for antidiabetic activities using a platform of in vitro bioassays and in vivo models of T2DM. This paper summarizes results on the 10 most promising plant species, their active constituents, and the mechanisms behind their antidiabetic activities. In addition, potential herb-drug interactions were examined at the level of drug-metabolizing enzymes, notably the cytochrome P450 family. This review serves as a canvas onto which is discussed the value of Indigenous medicinal plants, future avenues of research, and the ethical approach required in this field.

  14. Effects of harvesting on spatial and temporal diversity of carbon stocks in a boreal forest landscape.

    Science.gov (United States)

    Ter-Mikaelian, Michael T; Colombo, Stephen J; Chen, Jiaxin

    2013-10-01

    Carbon stocks in managed forests of Ontario, Canada, and in harvested wood products originated from these forests were estimated for 2010-2100. Simulations included four future forest harvesting scenarios based on historical harvesting levels (low, average, high, and maximum available) and a no-harvest scenario. In four harvesting scenarios, forest carbon stocks in Ontario's managed forest were estimated to range from 6202 to 6227 Mt C (millions of tons of carbon) in 2010, and from 6121 to 6428 Mt C by 2100. Inclusion of carbon stored in harvested wood products in use and in landfills changed the projected range in 2100 to 6710-6742 Mt C. For the no-harvest scenario, forest carbon stocks were projected to change from 6246 Mt C in 2010 to 6680 Mt C in 2100. Spatial variation in projected forest carbon stocks was strongly related to changes in forest age (r = 0.603), but had weak correlation with harvesting rates. For all managed forests in Ontario combined, projected carbon stocks in combined forest and harvested wood products converged to within 2% difference by 2100. The results suggest that harvesting in the boreal forest, if applied within limits of sustainable forest management, will eventually have a relatively small effect on long-term combined forest and wood products carbon stocks. However, there was a large time lag to approach carbon equality, with more than 90 years with a net reduction in stored carbon in harvested forests plus wood products compared to nonharvested boreal forest which also has low rates of natural disturbance. The eventual near equivalency of carbon stocks in nonharvested forest and forest that is harvested and protected from natural disturbance reflects both the accumulation of carbon in harvested wood products and the relatively young age at which boreal forest stands undergo natural succession in the absence of disturbance.

  15. NPP Boreal Forest: Schefferville, Canada, 1974, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains two files (.txt format). One file provides above- and below-ground biomass, soil, and nutrient data for a mature boreal ecosystem (subarctic...

  16. NPP Boreal Forest: Schefferville, Canada, 1974, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set contains two files (.txt format). One file provides above- and below-ground biomass, soil, and nutrient data for a mature boreal ecosystem...

  17. NPP Boreal Forest: Kuusamo, Finland, 1967-1971, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set contains three files (.txt format). One file provides stand characteristics, biomass, and production allocation data for an old-growth boreal...

  18. 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.

  19. Transformations of snow chemistry in the boreal forest: Accumulation and volatilization

    Science.gov (United States)

    Pomeroy, J.W.; Davies, T.D.; Jones, H.G.; Marsh, P.; Peters, N.E.; Tranter, M.

    1999-01-01

    This paper examines the processes and dynamics of ecologically-important inorganic chemical (primarily NO3-N) accumulation and loss in boreal forest snow during the cold winter period at a northern and southern location in the boreal forest of western Canada. Field observations from Inuvik, Northwest Territories and Waskesiu, Saskatchewan, Canada were used to link chemical transformations and physical processes in boreal forest snow. Data on the disposition and overwinter transformation of snow water equivalent, NO3-, SO42- and other major ions were examined. No evidence of enhanced dry deposition of chemical species to intercepted snow was found at either site except where high atmospheric aerosol concentrations prevailed. At Inuvik, concentrations of SO42- and Cl- were five to six times higher in intercepted snow than in surface snow away from the trees. SO4-S and Cl loads at Inuvik were correspondingly enhanced three-fold within the nearest 0.5 m to individual tree stems. Measurements of snow affected by canopy interception without rapid sublimation provided no evidence of ion volatilization from intercepted snow. Where intercepted snow sublimation rates were significant, ion loads in sub-canopy snow suggested that NO3- volatized with an efficiency of about 62% per snow mass sublimated. Extrapolating this measurement from Waskesiu to sublimation losses observed in other southern boreal environments suggests that 19-25% of snow inputs of NO3- can be lost during intercepted snow sublimation. The amount of N lost during sublimation may be large in high-snowfall, high N load southern boreal forests (Quebec) where 0.42 kg NO3-N ha-1 is estimated as a possible seasonal NO3- volatilization. The sensitivity of the N fluxes to climate and forest canopy variation and implications of the winter N losses for N budgets in the boreal forest are discussed.This paper examines the processes and dynamics of ecologically-important inorganic chemical (primarily NO3-N) accumulation

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    Pekka E Kauppi

    Full Text Available 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.

  2. 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

  3. 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.

  4. 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 carbon flux estimate resulted in emissions of 4 ± 2 g COe kWh as a contribution to the carbon footprint calculation, one-eighth what was obtained in a recent study that used less precise and less sensitive estimates. Consequently, this study significantly reduces the reported net carbon footprint of this reservoir and reveals how negligible the relative contribution of the land-use change in upland 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.

  5. 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

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

    DEFF Research Database (Denmark)

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

    1997-01-01

    A major role of the National Center for Atmospheric Research (NCAR) Electra aircraft during the Boreal Ecosystem-Atmosphere Study (BOREAS) was to measure fluxes of momentum, sensible and latent heat, carbon dioxide, and ozone on a transect that crossed the entire boreal forest biome...... forests to be more photosynthetically active than nearby coniferous forests. Coniferous forest fluxes across the transect from the BOREAS southern to northern study areas show no apparent spatial trend, though smaller-scale variability is large. The fluxes make a smooth transition from the BOREAS northern...... study area to the subarctic tundra. Typical midsummer, midday, large-scale net ecosystem exchanges of carbon dioxide were about -10 mu mol m(-2) s(-1) for primarily deciduous forests, about -6 mu mol m(-2) s(-1) for the primarily coniferous regions between and including the two BOREAS study areas...

  7. 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.

  8. 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.

  9. Boreal forest BVOC exchange: emissions versus in-canopy sinks

    Science.gov (United States)

    Zhou, Putian; Ganzeveld, Laurens; Taipale, Ditte; Rannik, Üllar; Rantala, Pekka; Petteri Rissanen, Matti; Chen, Dean; Boy, Michael

    2017-12-01

    A multilayer gas dry deposition model has been developed and implemented into a one-dimensional chemical transport model SOSAA (model to Simulate the concentrations of Organic vapours, Sulphuric Acid and Aerosols) to calculate the dry deposition velocities for all the gas species included in the chemistry scheme. The new model was used to analyse in-canopy sources and sinks, including gas emissions, chemical production and loss, dry deposition, and turbulent transport of 12 featured biogenic volatile organic compounds (BVOCs) or groups of BVOCs (e.g. monoterpenes, isoprene+2-methyl-3-buten-2-ol (MBO), sesquiterpenes, and oxidation products of mono- and sesquiterpenes) in July 2010 at the boreal forest site SMEAR II (Station for Measuring Ecosystem-Atmosphere Relations). According to the significance of modelled monthly-averaged individual source and sink terms inside the canopy, the selected BVOCs were classified into five categories: 1. Most of emitted gases are transported out of the canopy (monoterpenes, isoprene + MBO). 2. Chemical reactions remove a significant portion of emitted gases (sesquiterpenes). 3. Bidirectional fluxes occur since both emission and dry deposition are crucial for the in-canopy concentration tendency (acetaldehyde, methanol, acetone, formaldehyde). 4. Gases removed by deposition inside the canopy are compensated for by the gases transported from above the canopy (acetol, pinic acid, β-caryophyllene's oxidation product BCSOZOH). 5. The chemical production is comparable to the sink by deposition (isoprene's oxidation products ISOP34OOH and ISOP34NO3). Most of the simulated sources and sinks were located above about 0.2 hc (canopy height) for oxidation products and above about 0.4 hc for emitted species except formaldehyde. In addition, soil deposition (including deposition onto understorey vegetation) contributed 11-61 % to the overall in-canopy deposition. The emission sources peaked at about 0.8-0.9 hc, which was higher than 0.6 hc

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

    Science.gov (United States)

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

    2016-03-21

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

  11. Disentangling Modern Fire-Climate-Vegetation Relationships across the Boreal Forest Biome

    Science.gov (United States)

    Young, A. M.; Boschetti, L.; Duffy, P.; Hu, F.; Higuera, P.

    2015-12-01

    Fire regimes differ between Eurasian and North American boreal forests, due in part to differences in climate and the dominant forest types. While North American boreal forests are dominated by stand-replacing fires, much of the Eurasian boreal forest is characterized by lower intensity surface fires. These different fire regimes have important consequences for continental-scale biogeochemical cycling and surface-energy fluxes1. Here, we use generalized linear models (GLM) and boosted regression trees (BRT) to explore the relative importance of vegetation, annual climatic factors, and their interactions in determining annual fire occurrence across Eurasian and North American boreal forests. We use remotely sensed burned area (MCD64A1), land cover (MCD12Q1), and observed climate data (CRU) from 2002-2012 at 0.25° spatial resolution to quantify these relationships at annual temporal scales and continental spatial scales. The spatial distribution of boreal fire occurrence was well explained with climate and vegetation variables, with similarities and differences in fire-climate-vegetation relationships between Eurasia and North America. For example, while GLMs indicate vegetation is a significant factor determining fire occurrence in both continents, the effect of climate differed. Spring temperature and precipitation are significant factors explaining fire occurrence in Eurasia, but no climate variables were significant for explaining fire occurrence in North America. BRTs complement this analysis, highlighting climatic thresholds to fire occurrence in both continents. The nature of these thresholds can vary among vegetation types, even within each continent, further implying regional sensitivity to climate-induced shifts in wildfire activity. To build on these results and better understand regional sensitivity of northern-high latitude fire regimes, future work will explore these relationships in forest-tundra and arctic tundra ecosystems, and apply historical

  12. Structural equation modelling reveals plant-community drivers of carbon storage in boreal forest ecosystems

    Science.gov (United States)

    Jonsson, Micael; Wardle, David A.

    2010-01-01

    Boreal forest ecosystems are important drivers of the global carbon (C) cycle by acting as both sinks and sources of atmospheric CO2. While several factors have been proposed as determining the ability of boreal forest to function as C sinks, little is known about their relative importance. In this study, we applied structural equation modelling to a previously published dataset involving 30 boreal-forested islands that vary greatly in their historic fire regime, in order to explore the simultaneous influence of several factors believed to be important in influencing above-ground, below-ground and total ecosystem C accumulation. We found that wildfire was a major driver of ecosystem C sequestration, and exerted direct effects on below-ground C storage (presumably through humus combustion) and indirect effects on both above-ground and below-ground C storage through altering plant-community composition. By contrast, plant diversity influenced only below-ground C storage (and even then only weakly), while net primary productivity and decomposition had no detectable effect. Our results suggest that while boreal forests have great potential for storing significant amounts of C, traits of dominant plant species that promote below-ground C accumulation and the absence of wildfire are the most important drivers of C sequestration in these ecosystems. PMID:19755530

  13. Energy, water and carbon exchange in a boreal forest - NOPEX experiences.

    NARCIS (Netherlands)

    Halldin, S.; Gottschalk, L.; Gryning, S.E.; Jochum, A.; Lundin, L.C.; vd Griend, A.A.

    1998-01-01

    The role of the land surface in controlling climate is still underestimated and access to information from the boreal-forest zone is instrumental to improve this situation. This motivated the organisation of NOPEX (Northern hemisphere climate-Processes land-surface Experiment) in the southern part

  14. 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...

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

    NARCIS (Netherlands)

    Janssen, R.; Ganzeveld, L.N.; Kabat, P.; Kulmala, M.; Nieminen, T.; Roebeling, R.A.

    2011-01-01

    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

  16. Fire spread probabilities for experimental beds composed of mixedwood boreal forest fuels

    Science.gov (United States)

    M.B. Dickinson; E.A. Johnson; R. Artiaga

    2013-01-01

    Although fuel characteristics are assumed to have an important impact on fire regimes through their effects on extinction dynamics, limited capabilities exist for predicting whether a fire will spread in mixedwood boreal forest surface fuels. To improve predictive capabilities, we conducted 347 no-wind, laboratory test burns in surface fuels collected from the mixed-...

  17. The role of mosses in ecosystem succession and function in Alaska's boreal forest

    Science.gov (United States)

    Merritt R. Turetsky; Michelle C. Mack; Teresa N. Hollingsworth; Jennifer W. Harden

    2010-01-01

    Shifts in moss communities may affect the resilience of boreal ecosystems to a changing climate because of the role of moss species in regulating soil climate and biogeochemical cycling. Here, we use long-term data analysis and literature synthesis to examine the role of moss in ecosystem succession, productivity, and decomposition. In Alaskan forests, moss abundance...

  18. 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.

  19. 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...

  20. Temperature regimes and turbulent heat fluxes across a heterogeneous canopy in an Alaskan boreal forest

    Science.gov (United States)

    We evaluate local differences in thermal regimes and turbulent heat fluxes across the heterogeneous canopy of a black spruce boreal forest on discontinuous permafrost in interior Alaska. The data was taken during an intensive observing period in the summer of 2013 from two micrometeorological tower...

  1. Correction to: Compositional Changes in Foliage Phenolics with Plant Age, a Natural Experiment in Boreal Forests.

    Science.gov (United States)

    Wam, Hilde Karine; Stolter, Caroline; Nybakken, Line

    2017-10-13

    The article Compositional Changes in Foliage Phenolics with Plant Age, a Natural Experiment in Boreal Forests, written by Hilde Karine Wam, Caroline Stolter and Line Nybakken, was originally published electronically on the publisher's internet portal (currently SpringerLink) on August 29, 2017 without open access.

  2. 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.

  3. Toward Conservation of Canada's Boreal Forest Avifauna: Design and Application of Ecological Models at Continental Extents

    Directory of Open Access Journals (Sweden)

    Steven G. Cumming

    2010-12-01

    Full Text Available Human development is increasing pressure on North America's mainly intact boreal forest. We outline the need for a comprehensive synthesis of existing data and for effective scientific tools to support conservation of this biome and of the birds that depend on it. To illustrate how broad collaborations can address these needs, we introduce and report on the Boreal Avian Modelling Project. This is a new partnership involving universities, government, private, and nongovernment groups that was created to develop spatially explicit, predictive models of boreal bird habitat associations across Canada. This initiative is designed to improve our understanding of the influence of environmental factors and human activities on boreal bird species, leading to spatially explicit predictive models of the distribution of avian populations. The intended applications of these models are land use planning and avian conservation across the nearctic boreal forest. In this essay, we present a description of the extensive collection of point count survey data assembled by the Project, and the library of spatial covariates used for modeling. We show how it is possible to account for a number of nuisance variables related to differences in survey protocol among source data sets and make some preliminary suggestions as to how future surveys could be standardized. We present a distance-sampling approach used to convert standardized point count data to density estimates, which we illustrate by providing habitat-specific densities and total population estimates for one species in a part of western Canada. We also illustrate the use of Classification and Regression Trees to develop species niche models from the standardized data. We conclude with a discussion of the need for a monitoring program for boreal birds in Canada, the role of predictive statistical models in developing such a program, and how monitoring could be related to boreal bird conservation through

  4. Trophic cascades, invasive species and body-size hierarchies interactively modulate climate change responses of ecotonal temperate–boreal forest

    OpenAIRE

    Frelich, Lee E.; Rolf O. Peterson; Dovčiak, Martin; Reich, Peter B.; John A Vucetich; Eisenhauer, Nico

    2012-01-01

    As the climate warms, boreal tree species are expected to be gradually replaced by temperate species within the southern boreal forest. Warming will be accompanied by changes in above- and below-ground consumers: large moose (Alces alces) replaced by smaller deer (Odocoileus virginianus) above-ground, and small detritivores replaced by larger exotic earthworms below-ground. These shifts may induce a cascade of ecological impacts across trophic levels that could alter the boreal to temperate f...

  5. Observations of total RONO2 over the boreal forest: NOx sinks and HNO3 sources

    Directory of Open Access Journals (Sweden)

    E. C. Browne

    2013-05-01

    Full Text Available In contrast with the textbook view of remote chemistry where HNO3 formation is the primary sink of nitrogen oxides, recent theoretical analyses show that formation of RONO2 (ΣANs from isoprene and other terpene precursors is the primary net chemical loss of nitrogen oxides over the remote continents where the concentration of nitrogen oxides is low. This then increases the prominence of questions concerning the chemical lifetime and ultimate fate of ΣANs. We present observations of nitrogen oxides and organic molecules collected over the Canadian boreal forest during the summer which show that ΣANs account for ~20% of total oxidized nitrogen and that their instantaneous production rate is larger than that of HNO3. This confirms the primary role of reactions producing ΣANs as a control over the lifetime of NOx (NOx = NO + NO2 in remote, continental environments. However, HNO3 is generally present in larger concentrations than ΣANs indicating that the atmospheric lifetime of ΣANs is shorter than the HNO3 lifetime. We investigate a range of proposed loss mechanisms that would explain the inferred lifetime of ΣANs finding that in combination with deposition, two processes are consistent with the observations: (1 rapid ozonolysis of isoprene nitrates where at least ~40% of the ozonolysis products release NOx from the carbon backbone and/or (2 hydrolysis of particulate organic nitrates with HNO3 as a product. Implications of these ideas for our understanding of NOx and NOy budget in remote and rural locations are discussed.

  6. A framework to optimize the restoration and retention of large mature forest tracts in managed boreal landscapes.

    Science.gov (United States)

    Bouchard, Mathieu; Garet, Jérôme

    The decreasing abundance of mature forests and their fragmentation have been identified as major threats for the preservation of biodiversity in managed landscapes. In this study, we developed a multi-level framework to coordinate forest harvestings so as to optimize the retention or restoration of large mature forest tracts in managed forests. We used mixed-integer programming for this optimization, and integrated realistic management assumptions regarding stand yield and operational harvest constraints. The model was parameterized for eastern Canadian boreal forests, where clear-cutting is the main silvicultural system, and is used to examine two hypotheses. First, we tested if mature forest tract targets had more negative impacts on wood supplies when implemented in landscapes that are very different from targeted conditions. Second, we tested the hypothesis that using more partial cuts can be useful to attenuate the negative impacts of mature forest targets on wood supplies. The results indicate that without the integration of an explicit mature forest tract target, the optimization leads to relatively high fragmentation levels. Forcing the retention or restoration of large mature forest tracts on 40% of the landscapes had negative impacts on wood supplies in all types of landscapes, but these impacts were less important in landscapes that were initially fragmented. This counter-intuitive result is explained by the presence in the models of an operational constraint that forbids diffuse patterns of harvestings, which are more costly. Once this constraint is applied, the residual impact of the mature forest tract target is low. The results also indicate that partial cuts are of very limited use to attenuate the impacts of mature forest tract targets on wood supplies in highly fragmented landscapes. Partial cuts are somewhat more useful in landscapes that are less fragmented, but they have to be well coordinated with clearcut schedules in order to contribute

  7. 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.

  8. 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.

  9. The effect of climate anomalies and human ignition factor on wildfires in Russian boreal forests.

    Science.gov (United States)

    Achard, Frédéric; Eva, Hugh D; Mollicone, Danilo; Beuchle, René

    2008-07-12

    Over the last few years anomalies in temperature and precipitation in northern Russia have been regarded as manifestations of climate change. During the same period exceptional forest fire seasons have been reported, prompting many authors to suggest that these in turn are due to climate change. In this paper, we examine the number and areal extent of forest fires across boreal Russia for the period 2002-2005 within two forest categories: 'intact forests' and 'non-intact forests'. Results show a far lower density of fire events in intact forests (5-14 times less) and that those events tend to be in the first 10 km buffer zone inside intact forest areas. Results also show that, during exceptional climatic years (2002 and 2003), fire event density is twice that found during normal years (2004 and 2005) and average areal extent of fire events (burned area) in intact forests is 2.5 times larger than normal. These results suggest that a majority of the fire events in boreal Russia are of human origin and a maximum of one-third of their impact (areal extension) can be attributed to climate anomalies alone, the rest being due to the combined effect of human disturbances and climate anomalies.

  10. The changing role of fire in mediating the relationships among oaks, grasslands, mesic temperate forests, and boreal forests in the Lake States

    Science.gov (United States)

    Lee E. Frelich; Peter B. Reich; David W. Peterson

    2017-01-01

    Historically, oak forests and woodlands intergraded with southern boreal forest, temperate mesic forest, and grassland biomes, forming complex fire-mediated relationships in the Great Lakes region of Minnesota, Wisconsin, and Michigan, USA. Variability in fire recurrence intervals allowed oaks to mix with grasses or with mesic forest species in areas with high (2–10 yr...

  11. 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

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

    Science.gov (United States)

    Kelly, Ryan; Genet, Helene; McGuire, A. David; 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.

  13. Effects of nitrogen fertilization on the forest floor carbon balance over the growing season in a boreal pine forest

    Science.gov (United States)

    Metcalfe, D. B.; Eisele, B.; Hasselquist, N. J.

    2013-12-01

    Boreal forests play a key role in the global carbon cycle and are facing rapid shifts in nitrogen availability with poorly understood consequences for ecosystem function and global climate change. We quantified the effects of increasing nitrogen availability on carbon fluxes from a relatively understudied component of these forests - the forest floor - at three intervals over the summer growing period in a northern Swedish Scots pine stand. Nitrogen addition altered both the uptake and release of carbon dioxide from the forest floor, but the magnitude and direction of this effect depended on the time during the growing season and the amount of nitrogen added. Specifically, nitrogen addition stimulated net forest floor carbon uptake only in the late growing season. We find evidence for species-specific control of forest floor carbon sink strength, as photosynthesis per unit ground area was positively correlated only with the abundance of the vascular plant Vaccinium myrtillus and no others. Comparison of understorey vegetation photosynthesis and respiration from the study site indicates that understorey vegetation photosynthate was mainly supplying respiratory demands for much of the year. Only in the late season with nitrogen addition did understorey vegetation appear to experience a large surplus of carbon in excess of respiratory requirements. Further work, simultaneously comparing all major biomass and respiratory carbon fluxes in forest floor and tree vegetation, is required to resolve the likely impacts of environmental changes on whole-ecosystem carbon sequestration in boreal forests.

  14. Estimation of Boreal Forest Attributes from Very High Resolution Pléiades Data

    Directory of Open Access Journals (Sweden)

    Henrik J. Persson

    2016-09-01

    Full Text Available In this study, the potential of using very high resolution Pléiades imagery to estimate a number of common forest attributes for 10-m plots in boreal forest was examined, when a high-resolution terrain model was available. The explanatory variables were derived from three processing alternatives. Height metrics were extracted from image matching of the images acquired from different incidence angles. Spectral derivatives were derived by performing principal component analysis of the spectral bands and lastly, second order textural metrics were extracted from a gray-level co-occurrence matrix, computed with an 11 × 11 pixels moving window. The analysis took place at two Swedish test sites, Krycklan and Remningstorp, containing boreal and hemi-boreal forest. The lowest RMSE was estimated with 1.4 m (7.7% for Lorey’s mean height, 1.7 m (10% for airborne laser scanning height percentile 90, 5.1 m2·ha−1 (22% for basal area, 66 m3·ha−1 (27% for stem volume, and 26 tons·ha−1 (26% for above-ground biomass, respectively. It was found that the image-matched height metrics were most important in all models, and that the spectral and textural metrics contained similar information. Nevertheless, the best estimations were obtained when all three explanatory sources were used. To conclude, image-matched height metrics should be prioritised over spectral metrics when estimation of forest attributes is concerned.

  15. OH reactivity measurements within a boreal forest: evidence for unknown reactive emissions.

    Science.gov (United States)

    Sinha, Vinayak; Williams, J; Lelieveld, J; Ruuskanen, T M; Kajos, M K; Patokoski, J; Hellen, H; Hakola, H; Mogensen, D; Boy, M; Rinne, J; Kulmala, M

    2010-09-01

    Boreal forests emit large amounts of volatile organic compounds (VOCs) which react with the hydroxyl radical (OH) to influence regional ozone levels and form secondary organic aerosol. Using OH reactivity measurements within a boreal forest in Finland, we investigated the budget of reactive VOCs. OH reactivity was measured using the comparative reactivity method, whereas 30 individual VOCs were measured using proton transfer reaction mass spectrometry, thermal-desorption gas chromatography mass spectrometry, and liquid chromatography mass spectrometry, in August 2008. The measured OH reactivity ranged from below detection limit (3.5 s(-1)), to approximately 60 s(-1) in a single pollution event. The average OH reactivity was approximately 9 s(-1) and no diel variation was observed in the profiles. The measured OH sinks (approximately 30 species) accounted for only 50% of the total measured OH reactivity, implying unknown reactive VOCs within the forest. The five highest measured OH sinks were: monoterpenes (1 s(-1)), CO (0.7 s(-1)), isoprene (0.5 s(-1)), propanal and acetone (0.3 s(-1)), and methane (0.3 s(-1)). We suggest that models be constrained by direct OH reactivity measurements to accurately assess the impact of boreal forest emissions on regional atmospheric chemistry and climate.

  16. The Perfect Fire? Aging Stands in the Alaskan Boreal Forest Encounter Global Warming

    Science.gov (United States)

    Mann, D.; Rupp, S.; Duffy, P.

    2008-12-01

    The ecological responses of the boreal forest to climate change have global significance because of the large amount of carbon stored in its soils and biomass. Fire, mostly ignited by lightning, is the keystone disturbance agent in this forest. It triggers cycles of forest succession in its wake, and burning is the main avenue for carbon release back to the atmosphere. We studied the interactions between climate, fires, forest succession, and the age distributions of forest stands in a 60-million hectare region of Interior Alaska over the past 150 years. First we developed a statistical model relating climate to area burned over the period of record (1950-2005). Next we combined this model with climate reconstructions to extend the estimates of area burned back to A.D. 1860. We checked the resultant fire history against stand-age data from 5000 living trees sampled in the study region. Then we fed the history of area burned into a computer model that simulates forest succession on real landscapes. Results show striking changes in the means and variances of stand ages over the last 150 years in response to interactions between climate change and the successional dynamics of the boreal forest. Average stand age increased steadily between 1880 and 1940 and has fluctuated at high levels since then, indicating a historically unusual abundance of flammable stands. This accumulation of old stands has created the potential for unusually large fires. Some support for this conclusion comes from the unprecedented large sizes of the areas burned in 2004 and 2005. Further support comes when we add to the analysis the forecasts made by global climate models for Alaska over the next twenty years. Bracketing estimates for climate warming and precipitation change suggest that warmer, drier summers combined with aging forest stands will cause a series of unusually large fires, the like of which have not occurred in the region for >150 years. We infer that the enhanced burning of the

  17. 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...

  18. Fungal Community Shifts in Structure and Function across a Boreal Forest Fire Chronosequence.

    Science.gov (United States)

    Sun, Hui; Santalahti, Minna; Pumpanen, Jukka; Köster, Kajar; Berninger, Frank; Raffaello, Tommaso; Jumpponen, Ari; Asiegbu, Fred O; Heinonsalo, Jussi

    2015-11-01

    Forest fires are a common natural disturbance in forested ecosystems and have a large impact on the microbial communities in forest soils. The response of soil fungal communities to forest fire is poorly documented. Here, we investigated fungal community structure and function across a 152-year boreal forest fire chronosequence using high-throughput sequencing of the internal transcribed spacer 2 (ITS2) region and a functional gene array (GeoChip). Our results demonstrate that the boreal forest soil fungal community was most diverse soon after a fire disturbance and declined over time. The differences in the fungal communities were explained by changes in the abundance of basidiomycetes and ascomycetes. Ectomycorrhizal (ECM) fungi contributed to the increase in basidiomycete abundance over time, with the operational taxonomic units (OTUs) representing the genera Cortinarius and Piloderma dominating in abundance. Hierarchical cluster analysis by using gene signal intensity revealed that the sites with different fire histories formed separate clusters, suggesting differences in the potential to maintain essential biogeochemical soil processes. The site with the greatest biological diversity had also the most diverse genes. The genes involved in organic matter degradation in the mature forest, in which ECM fungi were the most abundant, were as common in the youngest site, in which saprotrophic fungi had a relatively higher abundance. This study provides insight into the impact of fire disturbance on soil fungal community dynamics. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

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

    Science.gov (United States)

    McGuire, A. David; 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?”

  20. Effects of ionizing radiation on the boreal forest: Canada's FIG experiment, with implications for radionuclides

    Energy Technology Data Exchange (ETDEWEB)

    Amiro, B.D.; Sheppard, S.C

    1994-07-01

    The Field-Irradiator Gamma (FIG) experiment chronically irradiated a section of the Canadian boreal forest over a period of 14 years. Forest trees were affected at dose rates >0.1 mGy{center_dot}h{sup -1}, but a berbaceous plant community thrived at dose rates up to 65 mGy{center_dot}h{sup -1}. Irradiation resulted in the establishment of four zones of vegetation: a herbaceous community, a shrub community, a narrow zone of dying trees, and a zone with no apparent impacts. Concentrations of {sup 14}C, {sup 99}Tc, {sup 129}I, {sup 137}Cs and {sup 226}Ra that could cause a dose rate of 0.1 mGy{center_dot}h{sup -1} within vegetation were calculated. Chemical toxic effects on plants would be caused by {sup 99}Tc and {sup 129}I before radiological effects are predicted to occur. The calculated {sup 226}Ra concentration is about a factor of 10 greater than that measured at some natural sites. Sufficiently high concentrations of {sup 14}C and {sup 137}Cs to cause an impact are unlikely unless a site is severely contaminated. (author)

  1. Introduction: Forest restoration in temperate and boreal zones

    Science.gov (United States)

    Emile Gardiner; Katrine Hahn; Magnus Löf

    2003-01-01

    The past decade has witnessed an acceleration of forest restoration activities around the globe. Afforestation of former agricultural land, rehabilitation of natural forest processes and structures at the stand and landscape levels, and conversion of single-species plantations to mixed-species stands are among the prominent types of restoration practices currently...

  2. Patterns of total ecosystem carbon storage with changes in soil temperature in boreal black spruce forests

    Science.gov (United States)

    E.S. Kane; J.G. Vogel

    2009-01-01

    To understand how carbon (C) pools in boreal ecosystems may change with warming, we measured above- and belowground C pools and C increment along a soil temperature gradient across 16 mature upland black spruce (Picea mariana Mill. [B•S.P]) forests in interior Alaska. Total spruce C stocks (stand and root C) increased from 1.3 to 8.5 kg C m

  3. Alaska's changing fire regime--implications for the vulnerability of its boreal forests

    Science.gov (United States)

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

    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...

  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. A molecular identification protocol for roots of boreal forest tree species.

    Science.gov (United States)

    Randall, Morgan J; Karst, Justine; Pec, Gregory J; Davis, Corey S; Hall, Jocelyn C; Cahill, James F

    2014-11-01

    Roots play a key role in many ecological processes, yet our ability to identify species from bulk root samples is limited. Molecular tools may be used to identify species from root samples, but they have not yet been developed for most systems. Here we present a PCR-based method previously used to identify roots of grassland species, modified for use in boreal forests. • We used repeatable interspecific size differences in fluorescent amplified fragment length polymorphisms of three noncoding chloroplast DNA regions to identify seven woody species common to boreal forests in Alberta, Canada. • Abies balsamea, Alnus crispa, Betula papyrifera, Pinus contorta, and Populus tremuloides were identifiable to species, while Picea glauca and Picea mariana were identifiable to genus. In mixtures of known composition of foliar DNA, species were identified with 98% accuracy using one region. Mixed root samples of unknown composition were identified with 100% accuracy; four species were identified using one region, while three species were identified using two regions. • This methodology is accurate, efficient, and inexpensive, and thus a valuable approach for ecological studies of roots. Furthermore, this method has now been validated for both grassland and boreal forest systems, and thus may also have applications in any plant community.

  8. 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

  9. Soil-to-plant transfer of uranium and its distribution between plant parts in boreal forest; Forests ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Roivainen, P.; Makkonen, S.; Holopainen, T.; Juutilainen, J. (Univ. of Kuopio, Dept. of Environmental Science, Kuopio (Finland))

    2009-06-15

    This study focused on investigating the soil-to-plant transfers of natural uranium and its distribution in the vegetative parts of four plant species representing different plant types common in boreal forest: May lily (Maianthemum bifolium), narrow buckler fern (Dryopteris carthusiana), rowan (Sorbus aucuparia) and spruce (Picea abies). The results were also used to assess concentration ratios between soil and different plant parts. (LN)

  10. 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.

  11. 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 worldwide1. Although the impact of drought on tree growth and mortality is being increasingly documented2-4, 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 outbreaks5-7 (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.

  12. 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

  13. 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.

  14. 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

  15. The importance of micrometeorological variations for photosynthesis and transpiration in a boreal coniferous forest

    DEFF Research Database (Denmark)

    Schurgers, Guy; Lagergren, F.; Molder, M.

    2015-01-01

    the importance of vertical variations in light, temperature, CO2 concentration and humidity within the canopy for fluxes of photosynthesis and transpiration of a boreal coniferous forest in central Sweden. A leaf-level photosynthesis-stomatal conductance model was used for aggregating these processes to canopy...... fluxes, where discrepancies are largely attributable to a lack of forest floor evaporation in the model. Simulations in which vertical heterogeneity was artificially suppressed revealed that the vertical distribution of light is the driver of vertical heterogeneity. Despite large differences between...

  16. Satellite microwave detection of boreal forest recovery from the extreme 2004 wildfires in Alaska and Canada.

    Science.gov (United States)

    Jones, Matthew O; Kimball, John S; Jones, Lucas A

    2013-10-01

    The rate of vegetation recovery from boreal wildfire influences terrestrial carbon cycle processes and climate feedbacks by affecting the surface energy budget and land-atmosphere carbon exchange. Previous forest recovery assessments using satellite optical-infrared normalized difference vegetation index (NDVI) and tower CO(2) eddy covariance techniques indicate rapid vegetation recovery within 5-10 years, but these techniques are not directly sensitive to changes in vegetation biomass. Alternatively, the vegetation optical depth (VOD) parameter from satellite passive microwave remote sensing can detect changes in canopy biomass structure and may provide a useful metric of post-fire vegetation response to inform regional recovery assessments. We analyzed a multi-year (2003-2010) satellite VOD record from the NASA AMSR-E (Advanced Microwave Scanning Radiometer for EOS) sensor to estimate forest recovery trajectories for 14 large boreal fires from 2004 in Alaska and Canada. The VOD record indicated initial post-fire canopy biomass recovery within 3-7 years, lagging NDVI recovery by 1-5 years. The VOD lag was attributed to slower non-photosynthetic (woody) and photosynthetic (foliar) canopy biomass recovery, relative to the faster canopy greenness response indicated from the NDVI. The duration of VOD recovery to pre-burn conditions was also directly proportional (P estimated tree cover loss used as a metric of fire severity. Our results indicate that vegetation biomass recovery from boreal fire disturbance is generally slower than reported from previous assessments based solely on satellite optical-infrared remote sensing, while the VOD parameter enables more comprehensive assessments of boreal forest recovery. © 2013 John Wiley & Sons Ltd.

  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. 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

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

    Science.gov (United States)

    Mazziotta, Adriano; Pouzols, Federico Montesino; Mönkkönen, Mikko; Kotiaho, Janne S; Strandman, Harri; Moilanen, Atte

    2016-09-15

    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 standard forest management rules, setting aside of mature stands, or setting aside of clear-cuts. We first estimated how habitat availability for focal indicator species and economic returns from timber harvesting develop through time as a function of forest type and action chosen. We then developed an optimal resource allocation by accounting for budget size and habitat availability of indicator species in different forest types. We also accounted for the perspective adopted towards sustainability, modeled via temporal preference and economic and ecological time discounting. Controversially, we found 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Disturbance-mediated heterogeneity drives pollinator diversity in boreal managed forest ecosystems.

    Science.gov (United States)

    Rodríguez, Antonio; Kouki, Jari

    2017-03-01

    Intensive forest management, together with fire suppression, have decreased structural complexity and altered dynamics of boreal forests profoundly. Such management threatens forest biodiversity and can reduce the provision of ecosystem services. Although the importance of ecosystem services is widely acknowledged, conservation strategies are hindered by poor knowledge about diversity patterns of service provider species as well as on mechanisms affecting these assemblages at different spatial and temporal scales. In this study, we assessed the effect of disturbance management on forest pollinator communities. To do so, we used a large-scale ecological experiment conducted in the year 2000, where forest complexity was manipulated with different harvest regimes and prescribed fire. Results were consistent with a positive response of pollinators to increasing habitat heterogeneity driven by past disturbances. Harvested sites harbored a diverse pollinator community, and showed higher spatial and temporal turnover in species richness. Conversely, old-growth forest communities were a nested subset of harvested sites and contained half of their total diversity. Variation in community composition (β diversity) was primarily affected by species temporal turnover. Throughout the season, β diversity was controlled by fire and harvesting legacies, which provide environmental heterogeneity in the form of flowering and nesting resources over space and time. Conservation strategies may undervalue ecosystem services in dynamic, naturally disturbance-driven, landscapes when relying solely on undisturbed forests areas. However, maintaining natural dynamics in early successional forests, by emulating natural disturbances at harvesting, hold promise for the conservation of both biodiversity and ecosystem services in boreal forests. © 2016 by the Ecological Society of America.

  1. 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

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

    Czech Academy of Sciences Publication Activity Database

    Lukeš, Petr; Stenberg, P.; Mottus, M.; Manninen, T.; Rautiainen, M.

    2016-01-01

    Roč. 52, OCT (2016), s. 296-305 ISSN 0303-2434 R&D Projects: GA MŠk(CZ) LM2010007; GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : Albedo * fAPAR * LAI * NDVI * Time series * Seasonal trends * Forest structure Subject RIV: EH - Ecology, Behaviour Impact factor: 3.930, year: 2016

  3. 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

  4. Vulnerability of carbon storage in North American boreal forests to wildfires during the 21st century

    Science.gov (United States)

    Balshi, M. S.; McGuire, Anthony David; Duffy, P.; Flannigan, M.; Kicklighter, David W.; Melillo, J.

    2009-01-01

    The boreal forest contains large reserves of carbon. Across this region, wildfires influence the temporal and spatial dynamics of carbon storage. In this study, we estimate fire emissions and changes in carbon storage for boreal North America over the 21st century. We use a gridded data set developed with a multivariate adaptive regression spline approach to determine how area burned varies each year with changing climatic and fuel moisture conditions. We apply the process-based Terrestrial Ecosystem Model to evaluate the role of future fire on the carbon dynamics of boreal North America in the context of changing atmospheric carbon dioxide (CO2) concentration and climate in the A2 and B2 emissions scenarios of the CGCM2 global climate model. Relative to the last decade of the 20th century, decadal total carbon emissions from fire increase by 2.5–4.4 times by 2091–2100, depending on the climate scenario and assumptions about CO2fertilization. Larger fire emissions occur with warmer climates or if CO2 fertilization is assumed to occur. Despite the increases in fire emissions, our simulations indicate that boreal North America will be a carbon sink over the 21st century if CO2 fertilization is assumed to occur in the future. In contrast, simulations excluding CO2 fertilization over the same period indicate that the region will change to a carbon source to the atmosphere, with the source being 2.1 times greater under the warmer A2 scenario than the B2 scenario. To improve estimates of wildfire on terrestrial carbon dynamics in boreal North America, future studies should incorporate the role of dynamic vegetation to represent more accurately post-fire successional processes, incorporate fire severity parameters that change in time and space, account for human influences through increased fire suppression, and integrate the role of other disturbances and their interactions with future fire regime.

  5. Snow ablation modeling at the stand scale in a boreal jack pine forest

    Science.gov (United States)

    Hardy, J. P.; Davis, R. E.; Jordan, R.; Li, X.; Woodcock, C.; Ni, W.; McKenzie, J. C.

    1997-12-01

    The purpose of this study is to predict spatial distributions of snow properties important to the hydrology and the remote sensing signatures of the boreal ecosystem. This study is part of the Boreal Ecosystems Atmosphere Study (BOREAS) of central Saskatchewan and northern Manitoba. Forested environments provide unique problems for snow cover process modeling due to the complex interactions among snow, energy transfer, and trees. These problems are approached by coupling a modified snow process model with a model of radiative interactions with forest canopies. Additionally, a tree well model describes the influence of individual trees on snow distribution on the ground. The snow process and energy budget model calculates energy exchange at the snow surface, in-pack snow processes, melting and liquid water flow, heat conduction, and vapor diffusion. The surface radiation model provides input on the radiation receipt at the snow surface for model runs in the jack pine forest. Field data consisted of measured meteorological parameters above and within the canopy, spatial variability of snow properties, and variations of incoming solar irradiance beneath the forest canopy. Results show that the area beneath tree canopies accumulated 60% of the snow accumulated in forest openings. Peak solar irradiance on the snow cover was less than one half that measured above the canopy. Model runs are compared between the open and the forested sites and show the open area ablating four days before areas beneath the canopy and eight days before forest openings and compare favorably with measured data. Physically based modeling of snow ablation was successful at the forested site and nearby open area.

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

    Science.gov (United States)

    Schobesberger, Siegfried; Lopez-Hilifiker, Felipe D.; Taipale, Ditte; Millet, Dylan B.; D'Ambro, Emma L.; Rantala, Pekka; Mammarella, Ivan; Zhou, Putian; Wolfe, Glenn M.; Lee, Ben H.; hide

    2016-01-01

    Eddy covariance fluxes of formic acid, HCOOH, were measured over a boreal forest canopy in spring/summer 2014. The HCOOH fluxes were bidirectional but mostly upward during daytime, in contrast to studies elsewhere that reported mostly downward fluxes. Downward flux episodes were explained well by modeled dry deposition rates. The sum of net observed flux and modeled dry 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 volatile organic compounds, suggesting missing or greatly underestimated HCOOH sources in the boreal ecosystem. 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 airborne and spaceborne observations. Model biases in the boundary layer were substantially reduced based on this revised treatment, but biases in the free troposphere remain unexplained.

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

    DEFF Research Database (Denmark)

    Mazziotta, Adriano; Triviño, María; Tikkanen, Olli-Pekka

    2016-01-01

    if species sensitivity, the species ability to tolerate climatic variations determined by traits, plays a key role in determining vulnerability. We analyse the role of species’ habitat associations, a proxy for sensitivity, in explaining vulnerability for two poorly-known but species-rich taxa in boreal...... forest, saproxylic beetles and fungi, using three IPCC emissions scenarios. Towards the end of the 21st century we projected an improvement in habitat quality associated with an increase of deadwood, an important resource for species, as a consequence of increased tree growth under high emissions...... scenarios. However, climate change will potentially reduce habitat suitability for ~9–43 % of the threatened deadwood-associated species. This loss is likely caused by future increase in timber extraction and decomposition rates causing higher deadwood turnover, which have a strong negative effect on boreal...

  8. 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

  9. Holocene changes in fire frequency in north-western boreal forest of Quebec, Canada

    Science.gov (United States)

    Cyr, D.; Bergeron, Y.; Carcaillet, C.; Gauthier, S.; Hely-Alleaume, C.; Flannigan, M.

    2004-12-01

    Changes in fire frequency were reconstructed for the last 8,000 yrs in the boreal forest of north-western Quebec using dendrochronology and charcoal records in lake sediments and organic soils. During the middle Holocene, fire frequency was characterized by a long period of low frequency between ca. 7500 and 2000 yrs BP. The high fire frequency during the last 2000 years was interrupted by periods of lower fire frequency notably since the end of the Little Ice Age ca 1850 AD. Climate appears to be the main process triggering fire. Simulations using GCMs (2xCO2 scenarios), buttressed by palaeoecological and dendrochronological evidence, suggest that future warming is unlikely to significantly increase fire frequency in the boreal forest of north-eastern Quebec since higher temperature appears to be associated with less frequent drought in this area. Palaeoecological and dendrochronological data clearly demonstrate the changing nature of forest ecosystem dynamics. We discuss the implications of these dynamics on disturbance-based forest management strategies

  10. 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.

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

    Science.gov (United States)

    Aaltonen, H.; Pumpanen, J.; Hakola, H.; Vesala, T.; Rasmus, S.; Bäck, J.

    2012-06-01

    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.

  12. 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.

  13. 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.

  14. 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.

  15. Boreal forest fires in 1997 and 1998: a seasonal comparison using transport model simulations and measurement data

    Directory of Open Access Journals (Sweden)

    N. Spichtinger

    2004-01-01

    Full Text Available Forest fire emissions have a strong impact on the concentrations of trace gases and aerosols in the atmosphere. In order to quantify the influence of boreal forest fire emissions on the atmospheric composition, the fire seasons of 1997 and 1998 are compared in this paper. Fire activity in 1998 was very strong, especially over Canada and Eastern Siberia, whereas it was much weaker in 1997. According to burned area estimates the burning in 1998 was more than six times as intense as in 1997. Based on hot spot locations derived from ATSR (Along Track Scanning Radiometer data and official burned area data, fire emissions were estimated and their transport was simulated with a Lagrangian tracer transport model. Siberian and Canadian forest fire tracers were distinguished to investigate the transport of both separately. The fire emissions were transported even over intercontinental distances. Due to the El Niño induced meteorological situation, transport from Siberia to Canada was enhanced in 1998. Siberian fire emissions were transported towards Canada and contributed concentrations more than twice as high as those due to Canada's own CO emissions by fires. In 1998 both tracers arrive at higher latitudes over Europe, which is due to a higher North Atlantic Oscillation (NAO index in 1998. The simulated emission plumes are compared to CMDL (Climate Monitoring and Diagnostics Laboratory CO2 and CO data, Total Ozone Mapping Spectrometer (TOMS aerosol index (AI data and Global Ozone Monitoring Experiment (GOME tropospheric NO2 and HCHO columns. All the data show clearly enhanced signals during the burning season of 1998 compared to 1997. The results of the model simulation are in good agreement with ground-based as well as satellite-based measurements.

  16. Scaling Hydrologic Processes in Boreal Forest Stands: New Eco-hydrological Perspectives or Deja vu?

    Science.gov (United States)

    Silins, U.; Lieffers, V. J.; Landhausser, S. M.; Mendoza, C. A.; Devito, K. J.; Petrone, R. M.; Gan, T. Y.

    2006-12-01

    The leaf area of forest canopies is both main attribute of stands controlling water balance through transpiration and interception, and "engine" driving stand growth, stand dynamics, and forest succession. While transpiration and interception dynamics are classic themes in forest hydrology, we present results from our eco-hydrological research on boreal trees to highlight how more recent eco-physiological insights into species specific controls over water use and leaf area such as hydraulic architecture, cavitation, sapwood-leaf area relationships, and root system controls over water uptake are providing new insights into integrated atmospheric-autecological controls over these hydrologic processes. These results are discussed in the context of newer eco-hydrological frameworks which may serve to aid in exploring how forest disturbance and subsequent trajectories of hydrologic recovery are likely to affect both forest growth dynamics and hydrology of forested landscapes in response to forest management, severe forest pest epidemics such as the Mountain Pine Beetle epidemic in Western Canada, and climate change.

  17. A decision-tree-based method for reconstructing disturbance history in the Russia boreal forests over 30 years

    Science.gov (United States)

    Chen, D.; Loboda, T. V.

    2012-12-01

    The boreal forest is one of the largest biomes on Earth and carries crucial significance in numerous aspects. Located in the high latitude region of the Northern Hemisphere, it is predicted that the boreal forest is subject to the highest level of influence under the changing climate, which may impose profound impacts on the global carbon and energy budget. Of the entire boreal biome, approximately two thirds consists of the Russian boreal forest, which is also the largest forested zone in the world. Fire and logging have been the predominant disturbance types in the Russian boreal forest, which accelerate the speed of carbon release into the atmosphere. To better understand these processes, records of past disturbance are in great need. However, there has been no comprehensive and unbiased multi-decadal record of forest disturbance in this region. This paper illustrates a method for reconstructing disturbance history in the Russia boreal forests over 30 years. This method takes advantage of data from both Landsat, which has a long data record but limited spatial coverage, and the Moderate Resolution Spectroradiometer (MODIS), which has wall-to-wall spatial coverage but limited period of observations. We developed a standardized and semi-automated approach to extract training and validation data samples from Landsat imagery. Landsat data, dating back to 1984, were used to generate maps of forest disturbance using temporal shifts in Disturbance Index through the multi-temporal stack of imagery in selected locations. The disturbed forests are attributed to logging or burning causes by means of visual examination. The Landsat-based disturbance maps are then used as reference data to train a decision tree classifier on 2003 MODIS data. This classifier utilizes multiple direct MODIS products including the BRDF-adjusted surface reflectance, a suite of vegetation indices, and land surface temperature. The algorithm also capitalizes on seasonal variability in class

  18. 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

  19. 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.

  20. Mites (Acari, Mesostigmata) in boreal Scots pine forest floors: effect of distance to stumps.

    Science.gov (United States)

    Kamczyc, Jacek; Gwiazdowicz, Dariusz J; Teodorowicz, Ewa; Strzymińska, Katarzyna

    2014-01-01

    Coarse woody debris (CWD) is a basic component of forest ecosystems and it plays a crucial role in species-poor boreal forests. Generally, previous studies have focused on differences between the forest floor and decaying logs of various tree species. The impact of distance to CWD has been investigated mainly for forest-floor snails and some groups of macrofauna, but not yet for mesostigmatid mites communities. We hypothesized that the effect of CWD decreases with increasing distance from CWD. To test this hypothesis we conducted a study in relatively species-poor Finnish boreal forest (at ca. 100 km northwest of Helsinki). In total, 81 samples were collected in 2007 from nine Scots pine (Pinus sylvestris) stumps, three microhabitats (CWD, soil/litter at 0.5 m from a stump and soil/litter at 1.5 m from a stump) and in three main directions (9 stumps × 3 microhabitats × 3 directions). Overall, 1965 mesostigmatid mites were collected representing 24 species. The mean number of mite species collected was significantly different between decaying stumps and forest litter; however, there was no significant difference between the litter samples at 0.5 and 1.5 m distance. The evenness index was significantly lower for samples collected from stumps than for litter in close (0.5 m) or far (1.5 m) distance. The most frequently encountered mite species were Veigaia nemorensis, Parazercon radiatus and Zercon zelawaiensis.

  1. The influence of canopy snow parameterizations on snow albedo feedback in boreal forest regions

    Science.gov (United States)

    Thackeray, Chad W.; Fletcher, Christopher G.; Derksen, Chris

    2014-08-01

    Variation in snow albedo feedback (SAF) among Coupled Model Intercomparison Project phase 5 climate models has been shown to explain much of the variation in projected 21st century warming over Northern Hemisphere land. Prior studies using observations and models have demonstrated both considerable spread in the albedo and a negative bias in the simulated strength of SAF, over snow-covered boreal forests. Boreal evergreen needleleaf forests are capable of intercepting snowfall throughout the winter and consequently exert a significant impact on seasonal surface albedo. Two satellite data products and tower-based observations of albedo are compared with simulations from multiple versions of the Community Climate System Model (CCSM4) to investigate the causes of weak simulated SAF over the boreal forest. The largest bias occurs in April and May, when simulated SAF is one half the strength of SAF in observations. This is traced to two features of the canopy snow parameterizations used in the land model. First, there is no mechanism for the dynamic removal of snow from the canopy when temperatures are below freezing, which results in albedo values in midwinter that are biased high. Second, when temperatures do rise above freezing, all snow on the canopy is melted instantaneously, which results in an unrealistically early transition from a snow-covered to a snow-free canopy. These processes combine to produce large differences between simulated and observed monthly albedo and are the source of the weak bias in SAF. This analysis highlights the importance of canopy snow parameterizations for simulating the hemispheric scale climate response to surface albedo perturbations.

  2. 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.

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

    Directory of Open Access Journals (Sweden)

    Victoria A Hudspith

    Full Text Available 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.

  4. 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.

  5. Changes in the parkland-boreal forest boundary in northwestern Ontario over the Holocene

    Science.gov (United States)

    Moos, Melissa T.; Cumming, Brian F.

    2011-05-01

    Changes in vegetation were tracked from a well-dated sediment core from a boreal lake, Lake 239, at ˜200-year resolution over the Holocene. This presently oligotrophic lake is located ˜100-km east from the present-day parkland-forest ecotone in northwestern Ontario. Near-shore sediment core transects from Lake 239 have previously shown this lake was at least 8-m lower than present in the mid-Holocene, or ˜58% less lake volume in comparison to today. Large shifts were expected in the terrestrial vegetation if the low lake levels were related to climate. The core from Lake 239 shows increases in the relative abundance and concentration of pollen such as Cupressaceae and Ambrosia, indicating a more open boreal forest between ˜4500-8000 cal yr BP. Pollen-based inferences of average, summer and winter temperatures suggest that temperatures were on average up to 1-2 °C warmer than today, with winter temperatures up to 4 °C warmer. The pollen inferences also suggest enhanced precipitation, likely in the summer, but with an overall increase in evaporation and evapotranspiration resulting in reduced effective moisture. To assess regional climate changes, pollen-based reconstructions of temperature and precipitation were developed and synthesized from sediment cores from eight previously published lakes, from which pollen sites were available to both the west and east of Lake 239, spanning present-day prairie lakes to forested lakes up to 300 km east of the prairie-boreal ecotone. All sites show shifts in pollen assemblages that indicate a warm mid-Holocene period; prairie sites west of the Experimental Lakes Area (ELA) show mid-Holocene decreases in precipitation relative to today, whereas sites near or east of ELA show consistent increases in precipitation, but with increased temperatures and enhanced evaporation during the mid-Holocene.

  6. 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

  7. Adaptive root foraging strategies along a boreal-temperate forest gradient.

    Science.gov (United States)

    Ostonen, Ivika; Truu, Marika; Helmisaari, Heljä-Sisko; Lukac, Martin; Borken, Werner; Vanguelova, Elena; Godbold, Douglas L; Lõhmus, Krista; Zang, Ulrich; Tedersoo, Leho; Preem, Jens-Konrad; Rosenvald, Katrin; Aosaar, Jürgen; Armolaitis, Kęstutis; Frey, Jane; Kabral, Naima; Kukumägi, Mai; Leppälammi-Kujansuu, Jaana; Lindroos, Antti-Jussi; Merilä, Päivi; Napa, Ülle; Nöjd, Pekka; Parts, Kaarin; Uri, Veiko; Varik, Mats; Truu, Jaak

    2017-08-01

    The tree root-mycorhizosphere plays a key role in resource uptake, but also in the adaptation of forests to changing environments. The adaptive foraging mechanisms of ectomycorrhizal (EcM) and fine roots of Picea abies, Pinus sylvestris and Betula pendula were evaluated along a gradient from temperate to subarctic boreal forest (38 sites between latitudes 48°N and 69°N) in Europe. Variables describing tree resource uptake structures and processes (absorptive fine root biomass and morphology, nitrogen (N) concentration in absorptive roots, extramatrical mycelium (EMM) biomass, community structure of root-associated EcM fungi, soil and rhizosphere bacteria) were used to analyse relationships between root system functional traits and climate, soil and stand characteristics. Absorptive fine root biomass per stand basal area increased significantly from temperate to boreal forests, coinciding with longer and thinner root tips with higher tissue density, smaller EMM biomass per root length and a shift in soil microbial community structure. The soil carbon (C) : N ratio was found to explain most of the variability in absorptive fine root and EMM biomass, root tissue density, N concentration and rhizosphere bacterial community structure. We suggest a concept of absorptive fine root foraging strategies involving both qualitative and quantitative changes in the root-mycorrhiza-bacteria continuum along climate and soil C : N gradients. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  8. 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.

  9. 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

  10. Effect of Tree Species and Mycorrhizal Colonization on the Archaeal Population of Boreal Forest Rhizospheres▿

    Science.gov (United States)

    Bomberg, Malin; Timonen, Sari

    2009-01-01

    Group 1.1c Crenarchaeota are the predominating archaeal group in acidic boreal forest soils. In this study, we show that the detection frequency of 1.1c crenarchaeotal 16S rRNA genes in the rhizospheres of the boreal forest trees increased following colonization by the ectomycorrhizal fungus Paxillus involutus. This effect was very clear in the fine roots of Pinus sylvestris, Picea abies, and Betula pendula, the most common forest trees in Finland. The nonmycorrhizal fine roots had a clearly different composition of archaeal 16S rRNA genes in comparison to the mycorrhizal fine roots. In the phylogenetic analysis, the 1.1c crenarchaeotal 16S rRNA gene sequences obtained from the fine roots formed a well-defined cluster separate from the mycorrhizal ones. Alnus glutinosa differed from the other trees by having high diversity and detection levels of Crenarchaeota both on fine roots and on mycorrhizas as well as by harboring a distinct archaeal flora. The similarity of the archaeal populations in rhizospheres of the different tree species was increased upon colonization by the ectomycorrhizal fungus. A minority of the sequences obtained from the mycorrhizas belonged to Euryarchaeota (order Halobacteriales). PMID:18978075

  11. 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. Some characteristics of mega-fires may emulate historical fire regimes and can therefore sustain healthy fire-prone ecosystems, but other attributes decrease ecosystem resiliency. A good example of a program that seeks to mitigate mega-fires is located in Western Australia, where prescribed burning reduces wildfire intensity while conserving ecosystems. Crown-fire-adapted ecosystems are likely at higher risk of frequent mega-fires as a result of climate change, as compared with other ecosystems once subject to frequent less severe fires. Fire and forest managers should recognize that mega-fires will be a part of future wildland fire regimes and should develop strategies to reduce their undesired impacts.

  12. 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. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

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

    Science.gov (United States)

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

    2016-01-01

    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 (P soil 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 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. PMID:26896139

  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. Mapping permafrost in the boreal forest with Thematic Mapper satellite data

    Science.gov (United States)

    Morrissey, L. A.; Strong, L. L.; Card, D. H.

    1986-01-01

    A geographic data base incorporating Landsat TM data was used to develop and evaluate logistic discriminant functions for predicting the distribution of permafrost in a boreal forest watershed. The data base included both satellite-derived information and ancillary map data. Five permafrost classifications were developed from a stratified random sample of the data base and evaluated by comparison with a photo-interpreted permafrost map using contingency table analysis and soil temperatures recorded at sites within the watershed. A classification using a TM thermal band and a TM-derived vegetation map as independent variables yielded the highest mapping accuracy for all permafrost categories.

  16. Effects of Intensified 21st Century Drought on the Boreal Forest of Alaska

    Science.gov (United States)

    Juday, G. P.; Alix, C. M.; Jess, R.; Grant, T. A., III

    2014-12-01

    A long term perspective on several quasi-decadal cycles of intensifying drought stress across boreal Alaska has been synthesized from monitoring of forest reference stands at Bonanza Creek LTER, Interior Alaska Research Natural Areas, and tree ring sampling across Alaska. The Alaska boreal forest is largely made up of tree populations with two growth responses to temperature increases. Negative responders are more common, and found across the warm, dry Interior. Positive responders are largely in western Alaska, a maritime climate region near the Bering Sea, and at high elevation of the Brooks and Alaska Ranges. Following the North Pacific climate regime shift in 1976-77, negative responder Interior white and black spruce, aspen, and birch all experienced major growth reductions, particularly in warm drought years. Elevated summer temperatures and low annual precipitation of recent decades at low elevations of the Tanana and central Yukon Valleys were outside the values which previously defined the species distributions limits, Long term survival prospects are questionable. Simultaneously, recent elevated temperatures were associated with growth increases of positive responders. On fertile floodplain sites of the lower Yukon and Kuskokwim Rivers, the growth rate of positive responding white spruce is now greater than negative responders for the first time in centuries. NDVI trends in recent decades confirm these opposite growth trends in their respective regions. During peak warm/dry anomalies, forest disturbance, an important process for tree regeneration over the long term, intensified in boreal Alaska. Several insect outbreaks of wood-boring and defoliating species associated with warm temperature/drought stress anomalies appeared, many of them severe, and some not previously known to outbreak. Significant tree injury (e.g. top dieback) and mortality resulted. Wildfire extent and severity increased and reached record levels. The overall pattern has been

  17. 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

  18. 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

  19. Belowground Competition Directs Spatial Patterns of Seedling Growth in Boreal Pine Forests in Fennoscandia

    Directory of Open Access Journals (Sweden)

    E. Petter Axelsson

    2014-09-01

    Full Text Available Aboveground competition is often argued to be the main process determining patterns of natural forest regeneration. However, the theory of multiple resource limitation suggests that seedling performance also depends on belowground competition and, thus, that their relative influence is of fundamental importance. Two approaches were used to address the relative importance of above- and below-ground competition on regeneration in a nutrient-poor pine (Pinus sylvestris boreal forest. Firstly, seedling establishment beneath trees stem-girdled 12 years ago show that a substantial proportion of the seedlings were established within two years after girdling, which corresponds to a time when nutrient uptake by tree roots was severely reduced without disrupting water transport to the tree canopy, which consequently was maintained. The establishment during these two years also corresponds to abundances high enough for normal stand replacement. Secondly, surveys of regeneration within forest gaps showed that surrounding forests depressed seedlings, so that satisfactory growth occurred only more than 5 m from forest edges and that higher solar radiation in south facing edges was not enough to mediate these effects. We conclude that disruption of belowground competitive interactions mediates regeneration and, thus, that belowground competition has a strong limiting influence on seedling establishment in these forests.

  20. Anthropogenic nitrogen deposition in boreal forests has a minor impact on the global carbon cycle.

    Science.gov (United States)

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

    2014-01-01

    It is proposed that increases in anthropogenic reactive nitrogen (Nr ) deposition may cause temperate and boreal forests to sequester a globally significant quantity of carbon (C); however, long-term data from boreal forests describing how C sequestration responds to realistic levels of chronic Nr deposition are scarce. Using a long-term (14-year) stand-scale (0.1 ha) N addition experiment (three levels: 0, 12.5, and 50 kg N ha(-1)  yr(-1) ) in the boreal zone of northern Sweden, we evaluated how chronic N additions altered N uptake and biomass of understory communities, and whether changes in understory communities explained N uptake and C sequestration by trees. We hypothesized that understory communities (i.e. mosses and shrubs) serve as important sinks for low-level N additions, with the strength of these sinks weakening as chronic N addition rates increase, due to shifts in species composition. We further hypothesized that trees would exhibit nonlinear increases in N acquisition, and subsequent C sequestration as N addition rates increased, due to a weakening understory N sink. Our data showed that understory biomass was reduced by 50% in response to the high N addition treatment, mainly due to reduced moss biomass. A (15) N labeling experiment showed that feather mosses acquired the largest fraction of applied label, with this fraction decreasing as the chronic N addition level increased. Contrary to our hypothesis, the proportion of label taken up by trees was equal (ca. 8%) across all three N addition treatments. The relationship between N addition and C sequestration in all vegetation pools combined was linear, and had a slope of 16 kg C kg(-1)  N. While canopy retention of Nr deposition may cause C sequestration rates to be slightly different than this estimate, our data suggest that a minor quantity of annual anthropogenic CO2 emissions are sequestered into boreal forests as a result of Nr deposition. © 2013 John Wiley & Sons Ltd.

  1. APPLICATION OF REMOTE SENSING DATA FOR THE ASSESSMENT OF THE UJUK MOUNTAIN BOREAL FORESTS (THE TYVA REPUBLIC, RUSSIA

    Directory of Open Access Journals (Sweden)

    Khulermaa B. Kuular

    2016-01-01

    Full Text Available This paper discusses some issues related to assessment and monitoring of forests insouthern Siberia. This study aims to evaluate the response of southern boreal forests to climate warming at local scale. Estimating the impacts of climate change on mountain boreal forests requires a more complete accounting of tree growth/climate interaction. We used both remote sensing and field data. Field measurements were made from the upper to lower timberline of dark deciduous forest in 2005 and 2012. The remote sensing datasets were generated from LANDSAT scenes of different dates (19.08.1988, 25.06.1992 and 18.08.2011. For estimation of forests changes, we used values of NDVI (Normalized Difference Vegetation Index and NBR (Normalized Burn Ratio.

  2. Source tracing of natural organic matter bound mercury in boreal forest runoff with mercury stable isotopes.

    Science.gov (United States)

    Jiskra, Martin; Wiederhold, Jan G; Skyllberg, Ulf; Kronberg, Rose-Marie; Kretzschmar, Ruben

    2017-10-18

    Terrestrial runoff represents a major source of mercury (Hg) to aquatic ecosystems. In boreal forest catchments, such as the one in northern Sweden studied here, mercury bound to natural organic matter (NOM) represents a large fraction of mercury in the runoff. We present a method to measure Hg stable isotope signatures of colloidal Hg, mainly complexed by high molecular weight or colloidal natural organic matter (NOM) in natural waters based on pre-enrichment by ultrafiltration, followed by freeze-drying and combustion. We report that Hg associated with high molecular weight NOM in the boreal forest runoff has very similar Hg isotope signatures as compared to the organic soil horizons of the catchment area. The mass-independent fractionation (MIF) signatures (Δ 199 Hg and Δ 200 Hg) measured in soils and runoff were in agreement with typical values reported for atmospheric gaseous elemental mercury (Hg 0 ) and distinctly different from reported Hg isotope signatures in precipitation. We therefore suggest that most Hg in the boreal terrestrial ecosystem originated from the deposition of Hg 0 through foliar uptake rather than precipitation. Using a mixing model we calculated the contribution of soil horizons to the Hg in the runoff. At moderate to high flow runoff conditions, that prevailed during sampling, the uppermost part of the organic horizon (Oe/He) contributed 50-70% of the Hg in the runoff, while the underlying more humified organic Oa/Ha and the mineral soil horizons displayed a lower mobility of Hg. The good agreement of the Hg isotope results with other source tracing approaches using radiocarbon signatures and Hg : C ratios provides additional support for the strong coupling between Hg and NOM. The exploratory results from this study illustrate the potential of Hg stable isotopes to trace the source of Hg from atmospheric deposition through the terrestrial ecosystem to soil runoff, and provide a basis for more in-depth studies investigating the

  3. Tree species richness decreases while species evenness increases with disturbance frequency in a natural boreal forest landscape.

    Science.gov (United States)

    Yeboah, Daniel; Chen, Han Y H; Kingston, Steve

    2016-02-01

    Understanding species diversity and disturbance relationships is important for biodiversity conservation in disturbance-driven boreal forests. Species richness and evenness may respond differently with stand development following fire. Furthermore, few studies have simultaneously accounted for the influences of climate and local site conditions on species diversity. Using forest inventory data, we examined the relationships between species richness, Shannon's index, evenness, and time since last stand-replacing fire (TSF) in a large landscape of disturbance-driven boreal forest. TSF has negative effect on species richness and Shannon's index, and a positive effect on species evenness. Path analysis revealed that the environmental variables affect richness and Shannon's index only through their effects on TSF while affecting evenness directly as well as through their effects on TSF. Synthesis and applications. Our results demonstrate that species richness and Shannon's index decrease while species evenness increases with TSF in a boreal forest landscape. Furthermore, we show that disturbance frequency, local site conditions, and climate simultaneously influence tree species diversity through complex direct and indirect effects in the studied boreal forest.

  4. 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.

  5. Ericoid Roots and Mycospheres Govern Plant-Specific Bacterial Communities in Boreal Forest Humus.

    Science.gov (United States)

    Timonen, Sari; Sinkko, Hanna; Sun, Hui; Sietiö, Outi-Maaria; Rinta-Kanto, Johanna M; Kiheri, Heikki; Heinonsalo, Jussi

    2017-05-01

    In this study, the bacterial populations of roots and mycospheres of the boreal pine forest ericoid plants, heather (Calluna vulgaris), bilberry (Vaccinium myrtillus), and lingonberry (Vaccinium vitis-idaea), were studied by qPCR and next-generation sequencing (NGS). All bacterial communities of mycosphere soils differed from soils uncolonized by mycorrhizal mycelia. Colonization by mycorrhizal hyphae increased the total number of bacterial 16S ribosomal DNA (rDNA) gene copies in the humus but decreased the number of different bacterial operational taxonomic units (OTUs). Nevertheless, ericoid roots and mycospheres supported numerous OTUs not present in uncolonized humus. Bacterial communities in bilberry mycospheres were surprisingly similar to those in pine mycospheres but not to bacterial communities in heather and lingonberry mycospheres. In contrast, bacterial communities of ericoid roots were more similar to each other than to those of pine roots. In all sample types, the relative abundances of bacterial sequences belonging to Alphaproteobacteria and Acidobacteria were higher than the sequences belonging to other classes. Soil samples contained more Actinobacteria, Deltaproteobacteria, Opitutae, and Planctomycetia, whereas Armatimonadia, Betaproteobacteria, Gammaproteobacteria, and Sphingobacteriia were more common to roots. All mycosphere soils and roots harbored bacteria unique to that particular habitat. Our study suggests that the habitation by ericoid plants increases the overall bacterial diversity of boreal forest soils.

  6. 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

  7. Modelling Variable Fire Severity in Boreal Forests: Effects of Fire Intensity and Stand Structure.

    Science.gov (United States)

    Miquelajauregui, Yosune; Cumming, Steven G; Gauthier, Sylvie

    2016-01-01

    It is becoming clear that fires in boreal forests are not uniformly stand-replacing. On the contrary, marked variation in fire severity, measured as tree mortality, has been found both within and among individual fires. It is important to understand the conditions under which this variation can arise. We integrated forest sample plot data, tree allometries and historical forest fire records within a diameter class-structured model of 1.0 ha patches of mono-specific black spruce and jack pine stands in northern Québec, Canada. The model accounts for crown fire initiation and vertical spread into the canopy. It uses empirical relations between fire intensity, scorch height, the percent of crown scorched and tree mortality to simulate fire severity, specifically the percent reduction in patch basal area due to fire-caused mortality. A random forest and a regression tree analysis of a large random sample of simulated fires were used to test for an effect of fireline intensity, stand structure, species composition and pyrogeographic regions on resultant severity. Severity increased with intensity and was lower for jack pine stands. The proportion of simulated fires that burned at high severity (e.g. >75% reduction in patch basal area) was 0.80 for black spruce and 0.11 for jack pine. We identified thresholds in intensity below which there was a marked sensitivity of simulated fire severity to stand structure, and to interactions between intensity and structure. We found no evidence for a residual effect of pyrogeographic region on simulated severity, after the effects of stand structure and species composition were accounted for. The model presented here was able to produce variation in fire severity under a range of fire intensity conditions. This suggests that variation in stand structure is one of the factors causing the observed variation in boreal fire severity.

  8. 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

  9. Effects of lightning and other meteorological factors on fire activity in the North American boreal forest: implications for fire weather forecasting

    Directory of Open Access Journals (Sweden)

    D. Peterson

    2010-07-01

    Full Text Available The effects of lightning and other meteorological factors on wildfire activity in the North American boreal forest are statistically analyzed during the fire seasons of 2000–2006 through an integration of the following data sets: the MODerate Resolution Imaging Spectroradiometer (MODIS level 2 fire products, the 3-hourly 32-km gridded meteorological data from North American Regional Reanalysis (NARR, and the lightning data collected by the Canadian Lightning Detection Network (CLDN and the Alaska Lightning Detection Network (ALDN. Positive anomalies of the 500 hPa geopotential height field, convective available potential energy (CAPE, number of cloud-to-ground lightning strikes, and the number of consecutive dry days are found to be statistically important to the seasonal variation of MODIS fire counts in a large portion of Canada and the entirety of Alaska. Analysis of fire occurrence patterns in the eastern and western boreal forest regions shows that dry (in the absence of precipitation lightning strikes account for only 20% of the total lightning strikes, but are associated with (and likely cause 40% of the MODIS observed fire counts in these regions. The chance for ignition increases when a threshold of at least 10 dry strikes per NARR grid box and at least 10 consecutive dry days is reached. Due to the orientation of the large-scale pattern, complex differences in fire and lightning occurrence and variability were also found between the eastern and western sub-regions. Locations with a high percentage of dry strikes commonly experience an increased number of fire counts, but the mean number of fire counts per dry strike is more than 50% higher in western boreal forest sub-region, suggesting a geographic and possible topographic influence. While wet lightning events are found to occur with a large range of CAPE values, a high probability for dry lightning occurs only when 500 hPa geopotential heights are above ~5700 m and CAPE values are

  10. High diversity of arbuscular mycorrhizal fungi in a boreal herb-rich coniferous forest.

    Science.gov (United States)

    Opik, Maarja; Moora, Mari; Zobel, Martin; Saks, Ulle; Wheatley, Ron; Wright, Frank; Daniell, Tim

    2008-01-01

    * Here, the diversity of arbuscular mycorrhizal (AM) fungi was determined in a boreal herb-rich coniferous forest in relation to environmental variables. * Root samples of five plant species (Fragaria vesca, Galeobdolon luteum, Hepatica nobilis, Oxalis acetosella and Trifolium pratense) were analysed from stands differing in age and forest management intensity. * Thirty-four Glomeromycota taxa (small-subunit ribosomal RNA gene (SSU rDNA) sequence groups) were detected from 90 root samples (911 clones), including eight new taxa. Sequence groups related to Glomus intraradices were most common (MO-G3 and MO-G13). Samples of H. nobilis were colonized by more AM fungal taxa (3.68 +/- 0.31) than those of O. acetosella (2.69 +/- 0.34), but did not differ significantly in this respect from those of F. vesca (3.15 +/- 0.38). Effects of forest management, host plant species (except above) or season on the number or composition of fungal taxa in root samples were not detected, and neither were they explained by environmental variables (vegetation, soil and light conditions). * This is the most taxon-rich habitat described to date in terms of root-colonizing Glomeromycota. The data demonstrate the importance of temperate coniferous forests as habitats for AM fungi and plants. Lack of obvious fungal community patterns suggests more complex effects of biotic and abiotic factors, and possibly no adverse effect of common forest management practices on AM fungal diversity.

  11. Retrieving forest background reflectance in a boreal region from Compact Airborne Spectrographic Imager (CASI) data

    Science.gov (United States)

    Pisek, J.; Chen, J. M.; Miller, J. R.

    2008-05-01

    Leaf area index (LAI) is one of the most important Earth's surface parameters in carbon balance and climate models. However, vegetation background (soil/moss/grass/shrub in forests) is a recognized problem that limits the accuracy of satellite-estimated forest LAI. In this study, we verify the feasibility of using multi-angle remote sensing to determine the optical properties of the vegetation background. Studies of the bidirectional behavior of forest canopy have shown that the total reflectance of a forest canopy is the combination of illuminated and shaded components of the tree crown as well as the background. Data from Compact Airborne Spectrographic Imager (CASI) positioned at the nadir and 40° forward directions over a boreal forest site near Sudbury, Ontario, Canada, were used to derive the reflectivity of the forest background based on the probabilities of viewing the illuminated tree crown and background at those view angles. The probabilities were estimated using the Four-Scale model. The derived values were then compared with in-situ background reflectance measured at the test sites. The modification of the background by white and black plastic sheets, together with the unmodified understory in the immediate neighborhood of the sites, provided us with two extreme limits and intermediate cases for the development and testing of the model for the successful retrieval of the information from the data. The results show that the developed methodology is capable of obtaining background reflectance for various forest stand conditions. This verification of the concept in the field is an important step towards the operational estimation of the forest background reflectance from the bidirectional reflections observed by Multi-angle Imaging SpectroRadiometer (MISR) instrument. Preliminary Canada-wide maps of background reflectance in red and NIR bands have been produced using MISR data.

  12. Environmental Studies in the Boreal Forest Zone: Summer IPY Institute at Central Boreal Forest Reserve, Fedorovskoe, Tver area, Russia (14-28 August, 2007)

    Science.gov (United States)

    Sparrow, E. B.; Kurbatova, Y.; Groisman, P.; Alexeev, V.

    2007-12-01

    The Summer Institute was organized by the International Arctic Research Center (IARC) at the University of Alaska Fairbanks, in collaboration with the A.N. Severtsov Institute for Ecology and Evolution of the Russian Academy of Sciences in Moscow, Russia, and the Central Forest State Nature Biosphere Reserve in Fedorovskoe, Russia. The Institute was arranged as a part of the education/outreach activities of the International Polar Year (IPY) at the University of Alaska and the Northern Eurasia Earth Science Partnership Initiative (NEESPI) and was held in Russia. The Institute provided a unique opportunity for participants to learn about the climate and environment of Northern Eurasia from leading scientists and educators, in a wide spectrum of polar and Earth system science disciplines from meteorology, biology, chemistry, and earth system modeling. Additionally, the Institute attendees observed and participated in the biospheric research activities under the guidance of experienced scientists. During a two-week-interval, the School attendees heard 40 lectures, attended several field trips and participated in three brainstorming Round Table Workshop Sessions devoted to perspectives of the boreal forest zone research and major unresolved problems that it faces. Thirty professors and experts in different areas of climate and biosphere research from Russia, the United States, Germany, Finland, and Japan, shared their expertise in lectures and in round table discussions with the Institute participants. Among the Institute participants there were 31 graduate students/early career scientists from six countries (China, Russia, Estonia, Finland, UK, and the United States) and eight K-12 teachers from Russia. The two groups joined together for several workshop sessions and for the field work components of the Institute. The field work was focused on land-atmosphere interactions and wetland studies in the boreal forest zone. Several field trips in and outside the Forest

  13. Scale-dependent controls on the area burned in the boreal forest of Canada, 1980-2005

    Science.gov (United States)

    Marc-Andre Parisien; Sean A. Parks; Meg A. Krawchuck; Mike D. Flannigan; Lynn M. Bowman; Max A. Moritz

    2011-01-01

    In the boreal forest of North America, as in any fire-prone biome, three environmental factors must coincide for a wildfire to occur: an ignition source, flammable vegetation, and weather that is conducive to fire. Despite recent advances, the relative importance of these factors remains the subject of some debate. The aim of this study was to develop models that...

  14. Decay of aspen (Populus tremuloides Michx.) wood in moist and dry boreal, temperate, and tropical forest fragments

    Science.gov (United States)

    Grizelle Gonzalez; William Gould; Andrew T. Hudak; Teresa Nettleton Hollingsworth

    2008-01-01

    In this study, we set up a wood decomposition experiment to i) quantify the percent of mass remaining, decay constant and performance strength of aspen stakes (Populus tremuloides) in dry and moist boreal (Alaska and Minnesota, USA), temperate (Washington and Idaho, USA), and tropical (Puerto Rico) forest types, and ii) determine the effects of...

  15. Impact of wildfire on stream nutrient chemistry and ecosystem metabolism in boreal forest catchments of interior Alaska

    Science.gov (United States)

    Emma F. Betts; Jeremy B. Jones

    2009-01-01

    With climatic warming, wildfire occurrence is increasing in the boreal forest of interior Alaska. Loss of catchment vegetation during fire can impact streams directly through altered solute and debris inputs and changed light and temperature regimes. Over longer time scales, fire can accelerate permafrost degradation, altering catchment hydrology and stream nutrient...

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

    NARCIS (Netherlands)

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

    2011-01-01

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

  17. Establishment and growth of white spruce on a boreal forest floodplain: interactions between microclimate and mammalian herbivory

    Science.gov (United States)

    Amy C. Angell; Knut. Kielland

    2009-01-01

    White spruce (Picea glauca (Moench) Voss) is a dominant species in late-successional ecosystems along the Tanana River, interior Alaska, and the most important commercial timber species in these boreal floodplain forests. Whereas white spruce commonly seed in on young terraces in early primary succession, the species does not become a conspicuous...

  18. Linking sediment-charcoal records and ecological modeling to understand causes of fire-regime change in boreal forests

    Science.gov (United States)

    Linda B. Brubaker; Philip E. Higuera; T. Scott Rupp; Mark A. Olson; Patricia M. Anderson; Feng Sheng. Hu

    2009-01-01

    Interactions between vegetation and fire have the potential to overshadow direct effects of climate change on fire regimes in boreal forests of North America. We develop methods to compare sediment-charcoal records with fire regimes simulated by an ecological model, ALFRESCO (Alaskan Frame-based Ecosystem Code) and apply these methods to evaluate potential causes of a...

  19. BOREAL FOREST CARBON STOCKS AND WOOD SUPPLY: PAST, PRESENT AND FUTURE RESPONSES TO CHANGING CLIMATE, AGRICULTURE AND SPECIES AVAILABILITY

    Science.gov (United States)

    The paper assesses the role in boreal forest growth played by environment. It examines past changes in climate coupled with glaciation, and future changes in climate coupled with agricultural land use and tree species availability. The objective was to define and evaluate potenti...

  20. Comparison of regression and geostatistical methods for mapping Leaf Area Index (LAI) with Landsat ETM+ data over a boreal forest.

    Science.gov (United States)

    Mercedes Berterretche; Andrew T. Hudak; Warren B. Cohen; Thomas K. Maiersperger; Stith T. Gower; Jennifer Dungan

    2005-01-01

    This study compared aspatial and spatial methods of using remote sensing and field data to predict maximum growing season leaf area index (LAI) maps in a boreal forest in Manitoba, Canada. The methods tested were orthogonal regression analysis (reduced major axis, RMA) and two geostatistical techniques: kriging with an external drift (KED) and sequential Gaussian...

  1. Modelling evapotranspiration at three boreal forest stands using the CLASS: tests of parameterizations for canopy conductance and soil evaporation

    Science.gov (United States)

    Bartlett, Paul A.; McCaughey, J. Harry; Lafleur, Peter M.; Verseghy, Diana L.

    2003-03-01

    The performance of the Canadian Land Surface Scheme (CLASS) was evaluated in off-line runs, using data collected at three boreal forest stands located near Thompson, Manitoba: young jack pine, mature jack pine, and mature black spruce. The data were collected in the late spring through autumn of 1994 and 1996, as part of the Boreal Ecosystem-Atmosphere Study (BOREAS).The diurnal range in modelled soil heat flux was exaggerated at all sites. Soil evaporation was modelled poorly at the jack pine stands, with overestimation common and a step change to low evaporation as the soil dried. Replacing the soil evaporation algorithm, which was based on the estimation of a surface relative humidity value, with one based on soil moisture in the top soil layer reduced the overestimation and eliminated the step changes. Modelled water movement between soil layers was too slow at the jack pine stands. Modifying the soil hydraulic parameters to match an observed characteristic curve at the young jack pine stand produced a soil water suction that agreed more closely with measurements and improved drainage between soil layers.The latent heat flux was overestimated and the sensible heat flux underestimated at all three stands. New Jarvis-Stewart-type canopy conductance algorithms were developed from stomatal conductance measurements. At the jack pine stands, stomatal conductance scaled by leaf area index reproduced canopy conductance, but a reduction in the scaled stomatal conductance by one half was necessary at the black spruce stand, indicating a nonlinearity in the scaling of stomatal conductance for this ecosystem. The root-mean-squared error for daily average latent heat flux for the control run of the CLASS and for the best test run are 49 W m-2 and 14 W m-2 respectively at the young jack pine stand, 50 W m-2 and 15 W m-2 respectively at the old jack pine stand, and 48 W m-2 and 13 W m-2 respectively at the old black spruce stand.

  2. Changes in growth of pristine boreal North American forests from 1950 to 2005 driven by landscape demographics and species traits

    Science.gov (United States)

    Girardin, M. P.; Guo, X. J.; Bernier, P. Y.; Raulier, F.; Gauthier, S.

    2012-07-01

    In spite of the many factors that are occurring and known for positively affecting the growth of forests, some boreal forests across North America have recently felt the adverse impacts of environmental changes. Knowledge of causes for productivity declines in North American boreal forests remains limited, and this is owed to the large spatial and temporal scales involved, and the many plant processes affected. Here, the response of pristine eastern boreal North American (PEBNA) forests to ongoing climatic changes is examined using in situ data, community ecology statistics, and species-specific model simulations of carbon exchanges forced by contemporary climatic data. To examine trends in forest growth, we used a recently acquired collection of tree-ring width data from 252 sample plots distributed in PEBNA forests dominated by black spruce (Picea mariana [Mill.] B.S.P.) and jack pine (Pinus banksiana Lamb.). Results of linear trend analysis on the tree growth data highlight a dominating forest growth decline in overmature forests (age > 120 years) from 1950 to 2005. In contrast, improving growth conditions are seen in jack pine and mature (70-120 years) black spruce stands. Multivariate analysis of climate and growth relationships suggests that responses of PEBNA forests to climate are dependent on demographic and species traits via their mediation of temperature and water stress constraints. In support of this hypothesis, the simulation experiment suggests that in old-growth black spruce stands the benefit to growth brought on by a longer growing season may have been low in comparison with the increasing moisture stress and respiration losses caused by warmer summer temperatures. Predicted increases in wildfire frequency in PEBNA forests will likely enhance the positive response of landscape-level forest growth to climate change by shifting the forest distribution to younger age classes while also enhancing the jack pine component.

  3. Trophic cascades, invasive species and body-size hierarchies interactively modulate climate change responses of ecotonal temperate-boreal forest.

    Science.gov (United States)

    Frelich, Lee E; Peterson, Rolf O; Dovčiak, Martin; Reich, Peter B; Vucetich, John A; Eisenhauer, Nico

    2012-11-05

    As the climate warms, boreal tree species are expected to be gradually replaced by temperate species within the southern boreal forest. Warming will be accompanied by changes in above- and below-ground consumers: large moose (Alces alces) replaced by smaller deer (Odocoileus virginianus) above-ground, and small detritivores replaced by larger exotic earthworms below-ground. These shifts may induce a cascade of ecological impacts across trophic levels that could alter the boreal to temperate forest transition. Deer are more likely to browse saplings of temperate tree species, and European earthworms favour seedlings of boreal tree species more than temperate species, potentially hindering the ability of temperate tree species to expand northwards. We hypothesize that warming-induced changes in consumers will lead to novel plant communities by changing the filter on plant species success, and that above- and below-ground cascades of trophic interactions will allow boreal tree species to persist during early phases of warming, leading to an abrupt change at a later time. The synthesis of evidence suggests that consumers can modify the climate change-induced transition of ecosystems.

  4. Sixty years of vegetation dynamics in a south boreal coniferous forest in southern Norway

    Energy Technology Data Exchange (ETDEWEB)

    Nygaard, P.H. [Norwegian Forest Research Inst., Aas (Norway); Oedegaard, T. [Hamar Teacher Training School (Norway)

    1999-02-01

    Vegetation data from permanent plots were collected in 1931, 1961 and 1991 in a south boreal forest 20 km north of Oslo in southern Norway. Major changes were found in the vegetation composition during those 60 years. The main changes were a reduction in the frequency of species and the frequency of joint occurrences of vascular species such as Andromeda polifolia, Calluna vulgaris, Cornus suecica, Eriophorum vaginatum, Maianthemum bifolium, Melampyrum pratense, Trientalis europaea, Vaccinium uliginosum and V. oxycoccus, and mosses, e.g. Dicranum fuscescens, Hylocomium splendens, Pleurozium schreberi, Ptilidium ciliare and Ptilium crista-castrensis. The observed changes were interpreted as being induced by internal processes e.g. notably a long-term change from paludified forest to mesic forest. In particular the growth of Picea abies seems to be a main driving force. The dominance of Picea abies and Vaccinium myrtillus appears to have rendered the conditions more unfavourable for other species. A doubling of the living stem biomass of P. abies during the last 67 yr shows that this old-growth forest has not yet reached a steady state. It was demonstrated that species such as Deschampsia flexuosa and Molinia caerulea did not increase in frequency in response to nitrogen deposition, as has occurred elsewhere in northern Europe. pH in the humus layer increased with 0.2 units from 1961 to 1991. The results of this study indicate that protection from logging has initiated the reduction of species in the field layer and bottom layer. This study questions if monitoring of forest vegetation should be restricted to protected forests as is the practice in Scandinavia today. We recommend that also areas with some kind of selective cutting will be used for monitoring of forest vegetation 68 refs, 4 figs, 9 tabs

  5. 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.

  6. Using InSAR Coherence to Map Stand Age in a Boreal Forest

    Directory of Open Access Journals (Sweden)

    Naiara Pinto

    2012-12-01

    Full Text Available The interferometric coherence parameter γ estimates the degree of correlation between two Synthetic Aperture Radar (SAR images and can be influenced by vegetation structure. Here, we investigate the use of repeat-pass interferometric coherence γ to map stand age, an important parameter for the study of carbon stocks and forest regeneration. In August 2009 NASA’s L-band airborne sensor UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar acquired zero-baseline data over Quebec with temporal separation ranging between 45 min and 9 days. Our analysis focuses on a 66 km2 managed boreal forest and addresses three questions: (i Can coherence from L-band systems be used to model forest age? (ii Are models sensitive to weather events and temporal baseline? and (iii How is model accuracy impacted by the spatial scale of analysis? Linear regression models with 2-day baseline showed the best results and indicated an inverse relationship between γ and stand age. Model accuracy improved at 5 ha scale (R2 = 0.75, RMSE = 5.3 as compared to 1 ha (R2 = 0.67, RMSE = 5.8. Our results indicate that coherence measurements from L-band repeat-pass systems can estimate forest age accurately and with no saturation. However, empirical model relationships and their accuracy are sensitive to weather events, temporal baseline, and spatial scale of analysis.

  7. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-31

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

  9. Newtonian boreal forest ecology: The Scots pine ecosystem as an example.

    Directory of Open Access Journals (Sweden)

    Pertti Hari

    Full Text Available Isaac Newton's approach to developing theories in his book Principia Mathematica proceeds in four steps. First, he defines various concepts, second, he formulates axioms utilising the concepts, third, he mathematically analyses the behaviour of the system defined by the concepts and axioms obtaining predictions and fourth, he tests the predictions with measurements. In this study, we formulated our theory of boreal forest ecosystems, called NewtonForest, following the four steps introduced by Newton. The forest ecosystem is a complicated entity and hence we needed altogether 27 concepts to describe the material and energy flows in the metabolism of trees, ground vegetation and microbes in the soil, and to describe the regularities in tree structure. Thirtyfour axioms described the most important features in the behaviour of the forest ecosystem. We utilised numerical simulations in the analysis of the behaviour of the system resulting in clear predictions that could be tested with field data. We collected retrospective time series of diameters and heights for test material from 6 stands in southern Finland and five stands in Estonia. The numerical simulations succeeded to predict the measured diameters and heights, providing clear corroboration with our theory.

  10. Newtonian boreal forest ecology: The Scots pine ecosystem as an example.

    Science.gov (United States)

    Hari, Pertti; Aakala, Tuomas; Aalto, Juho; Bäck, Jaana; Hollmén, Jaakko; Jõgiste, Kalev; Koupaei, Kourosh Kabiri; Kähkönen, Mika A; Korpela, Mikko; Kulmala, Liisa; Nikinmaa, Eero; Pumpanen, Jukka; Salkinoja-Salonen, Mirja; Schiestl-Aalto, Pauliina; Simojoki, Asko; Havimo, Mikko

    2017-01-01

    Isaac Newton's approach to developing theories in his book Principia Mathematica proceeds in four steps. First, he defines various concepts, second, he formulates axioms utilising the concepts, third, he mathematically analyses the behaviour of the system defined by the concepts and axioms obtaining predictions and fourth, he tests the predictions with measurements. In this study, we formulated our theory of boreal forest ecosystems, called NewtonForest, following the four steps introduced by Newton. The forest ecosystem is a complicated entity and hence we needed altogether 27 concepts to describe the material and energy flows in the metabolism of trees, ground vegetation and microbes in the soil, and to describe the regularities in tree structure. Thirtyfour axioms described the most important features in the behaviour of the forest ecosystem. We utilised numerical simulations in the analysis of the behaviour of the system resulting in clear predictions that could be tested with field data. We collected retrospective time series of diameters and heights for test material from 6 stands in southern Finland and five stands in Estonia. The numerical simulations succeeded to predict the measured diameters and heights, providing clear corroboration with our theory.

  11. Radiative forcing impacts of boreal forest biofuels: a scenario study for Norway in light of albedo.

    Science.gov (United States)

    Bright, Ryan M; Strømman, Anders Hammer; Peters, Glen P

    2011-09-01

    Radiative forcing impacts due to increased harvesting of boreal forests for use as transportation biofuel in Norway are quantified using simple climate models together with life cycle emission data, MODIS surface albedo data, and a dynamic land use model tracking carbon flux and clear-cut area changes within productive forests over a 100-year management period. We approximate the magnitude of radiative forcing due to albedo changes and compare it to the forcing due to changes in the carbon cycle for purposes of attributing the net result, along with changes in fossil fuel emissions, to the combined anthropogenic land use plus transport fuel system. Depending on albedo uncertainty and uncertainty about the geographic distribution of future logging activity, we report a range of results, thus only general conclusions about the magnitude of the carbon offset potential due to changes in surface albedo can be drawn. Nevertheless, our results have important implications for how forests might be managed for mitigating climate change in light of this additional biophysical criterion, and in particular, on future biofuel policies throughout the region. Future research efforts should be directed at understanding the relationships between the physical properties of managed forests and albedo, and how albedo changes in time as a result of specific management interventions.

  12. Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

    Science.gov (United States)

    Gao, Yao; Markkanen, Tiina; Aurela, Mika; Mammarella, Ivan; Thum, Tea; Tsuruta, Aki; Yang, Huiyi; Aalto, Tuula

    2017-09-01

    The influence of drought on plant functioning has received considerable attention in recent years, however our understanding of the response of carbon and water coupling to drought in terrestrial ecosystems still needs to be improved. A severe soil moisture drought occurred in southern Finland in the late summer of 2006. In this study, we investigated the response of water use efficiency to summer drought in a boreal Scots pine forest (Pinus sylvestris) on the daily time scale mainly using eddy covariance flux data from the Hyytiälä (southern Finland) flux site. In addition, simulation results from the JSBACH land surface model were evaluated against the observed results. Based on observed data, the ecosystem level water use efficiency (EWUE; the ratio of gross primary production, GPP, to evapotranspiration, ET) showed a decrease during the severe soil moisture drought, while the inherent water use efficiency (IWUE; a quantity defined as EWUE multiplied with mean daytime vapour pressure deficit, VPD) increased and the underlying water use efficiency (uWUE, a metric based on IWUE and a simple stomatal model, is the ratio of GPP multiplied with a square root of VPD to ET) was unchanged during the drought. The decrease in EWUE was due to the stronger decline in GPP than in ET. The increase in IWUE was because of the decreased stomatal conductance under increased VPD. The unchanged uWUE indicates that the trade-off between carbon assimilation and transpiration of the boreal Scots pine forest was not disturbed by this drought event at the site. The JSBACH simulation showed declines of both GPP and ET under the severe soil moisture drought, but to a smaller extent compared to the observed GPP and ET. Simulated GPP and ET led to a smaller decrease in EWUE but a larger increase in IWUE because of the severe soil moisture drought in comparison to observations. As in the observations, the simulated uWUE showed no changes in the drought event. The model deficiencies exist

  13. Experimental Warming Effects on Soil Respiration at the Temperate Boreal Forest Ecotone

    Science.gov (United States)

    Eddy, W. C.; Hobbie, S. E.; Reich, P. B.; Rich, R. L.; Montgomery, R. A.; Oleksyn, J.

    2010-12-01

    Climate models project that global mean annual temperature will increase by 1.1-6.4°C by the end of the 21st century. Whether terrestrial ecosystem feedbacks will mitigate or enhance warming represents a significant uncertainty in such projections of future climate. One of the largest potential positive feedbacks to climate warming is that arising from enhanced release of CO2 from warmer soils. Soils contain approximately twice as much carbon (C) as the atmosphere and microbial decomposition of soil C is expected to increase with climate warming, as temperature is often the most important factor in determining rates of soil organic matter decomposition. Thus, the aim of this investigation is to determine the soil respiration response to warming in a highly replicated open-air ecosystem warming experiment in two southern boreal forests of Minnesota. We measured in situ soil respiration response to ecosystem warming in an open-air warming experiment at two southern boreal forest sites in northern Minnesota. The experiment uses infrared heat lamps and soil heating cables (at 10-cm depth) to heat 7-m2 plots continuously by during the growing season by 2 or 4°C above ambient. Additionally, there are two ambient temperature treatments, one undisturbed, and the other with inactive soil warming cables (n=6). We measured soil CO2 flux every two weeks during the snow free season for two growing seasons (2009-2010) using a portable infrared gas analyzer with soil chamber attached. To date, we found slight increases in soil respiration in the two heated treatments relative to the disturbed soil control, corresponding to a 13% (2009) and 14% (2010) increase in soil CO2 flux in the +4°C treatment. These treatment effects are smaller than initial warming effects on soil respiration in many other studies. Several untested mechanisms could explain the smaller than expected warming effects on soil respiration. One likely explanation is that warming has significantly reduced soil

  14. Mapping forest composition from the Canadian National Forest Inventory and land cover classification maps.

    Science.gov (United States)

    Yemshanov, Denys; McKenney, Daniel W; Pedlar, John H

    2012-08-01

    Canada's National Forest Inventory (CanFI) provides coarse-grained, aggregated information on a large number of forest attributes. Though reasonably well suited for summary reporting on national forest resources, the coarse spatial nature of this data limits its usefulness in modeling applications that require information on forest composition at finer spatial resolutions. An alternative source of information is the land cover classification produced by the Canadian Forest Service as part of its Earth Observation for Sustainable Development of Forests (EOSD) initiative. This product, which is derived from Landsat satellite imagery, provides relatively high resolution coverage, but only very general information on forest composition (such as conifer, mixedwood, and deciduous). Here we link the CanFI and EOSD products using a spatial randomization technique to distribute the forest composition information in CanFI to the forest cover classes in EOSD. The resultant geospatial coverages provide randomized predictions of forest composition, which incorporate the fine-scale spatial detail of the EOSD product and agree in general terms with the species composition summaries from the original CanFI estimates. We describe the approach and provide illustrative results for selected major commercial tree species in Canada.

  15. Drought effect on methane, nitrous oxide and carbon dioxide dynamics along boreal forest-mire ecotone

    Science.gov (United States)

    Ťupek, Boris; Minkkinen, Kari; Vesala, Timo; Kolari, Pasi; Starr, Mike; Alm, Jukka; Pumpanen, Jukka; Berninger, Frank; Laine, Jukka; Nikinmaa, Eero

    2013-04-01

    The effect of drought on CH4, N2O and CO2 dynamics of boreal forest and mires has been seldom observed in a continuum between xeric and wet habitats. Such a continuum includes a transitional zone between forests and mires which is frequently exposed to large soil moisture differences, but generally overlooked due to a relatively narrow extent. Although, it's known that CH4, N2O and CO2 dynamics are sensitive to soil moisture. We evaluated spatiotemporal effects of drought on CH4, N2O and CO2 dynamics in continuum of nine distinct forest/mire types. Soils changed from well-drained podzols to poorly-drained histosols and ground water raised downslope from the depth of 10 m in upland forests to 0.1 m in mires. Meteorological conditions, forest floor respiration, methane, and nitrous oxide flux data were collected during growing season of exceptionally wet (2004), intermediate (2005), and exceptionally dry (2006) year. The CH4, N2O and CO2 fluxes were studied by chamber methods. The seasonal median forest floor CH4, N2O, and CO2 dark fluxes between forest/mire types and between rainy, intermediate, and dry years varied from -0.07 to 1.68 mgCH4 m2 h-1, from 1.5 to 24.65 μgN2O m2 h-1, and from 0.26 to 0.76 gCO2 m2 h-1. The CH4 oxidation in upland forest and transitional types was similar between wet and dry years, though the CH4 production of mires was reduced in dry year. Probably due to low nitrification potential, larger soil water differences between years 2005 and 2006 did not seem to trigger corresponding changes in small N2O fluxes. The forest floor dark CO2 efflux during drought was in comparison to wetter periods significantly reduced in upland forest and transitional types, but stayed similar or even increased in mires. In the carbon rich soil of forest/mire transitions mainly soil CO2 efflux were sensitive to short term fluctuations between water level drawdown and water saturation, whereas CH4 and N2O fluxes changed minimally.

  16. Boreal forest prospects and politics: Paradoxes of first nations participation in multi-sector conservation

    Directory of Open Access Journals (Sweden)

    Anna J Willow

    2016-01-01

    Full Text Available This article explores the prospects and politics of indigenous participation in multi-sector conservation—an integrative and proactive new approach to sustaining the integrity of vast natural ecosystems—by presenting the case of the Boreal Leadership Council (BLC, an initiative comprised of Environmental Non-Governmental Organisations (ENGOs, First Nations groups, resource-extractive corporations, and financial institutions committed to collectively addressing issues impacting Canada's boreal forest. Drawing on multi-sited participant-observation and interviews with BLC members and affiliates, I show how the BLC challenges wilderness-oriented definitions of conservation by undertaking projects that intertwine resource use, land rights, cultural preservation, and political authority, but concurrently perpetuates dominant perspectives by adhering to discursive practices that limit how environmental information can be persuasively presented. Ultimately, I argue that multi-sector conservation creates both new possibilities for indigenous empowerment and new forms of marginalisation through the reproduction of a (postcolonial geography of exclusion in which indigenous participants knowingly and strategically travel from the centre of their own worlds to peripheral positions within a larger—and inherently inequitable—sociopolitical structure.

  17. 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.

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

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    Gunnar Jungqvist

    Full Text Available 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.

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

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    Annie Claude Bélisle

    2016-07-01

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

  20. Compositional Changes in Foliage Phenolics with Plant Age, a Natural Experiment in Boreal Forests.

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    Wam, Hilde Karine; Stolter, Caroline; Nybakken, Line

    2017-09-01

    The composition of plant secondary metabolites (PSMs) extensively impacts ecosystem functioning. It is vital that we understand temporal patterns in the plants' allocation of resources to PSMs, particularly those influenced by human activity. Existing data are insufficient in the long-term perspective of perennial plants (age or ontogeny). We analysed phenolic concentrations in foliage from birch (Betula pubescens Ehr.) considered to be undamaged and growing on 5, 10 and 15 years old clear-cuts in two boreal forest landscapes in Norway, sampled at the peak of the growing season. In sum, low molecular weight phenolic concentrations decreased with age. Apart from one apigenin glycoside, the low molecular weight phenolics co-varied similarly at all ages, suggesting a lack of temporal compound-specific prioritisation of this group. In contrast, the concentration of MeOH-soluble condensed tannins increased with age. The compositional shift fits well with several hypotheses that may provide proximate explanations for age patterns in PSM allocations, including both resource constraints and external pressures. Regardless of these explanations, our study adds an important perennial perspective (plant age) to temporal PSM patterns already well-known in boreal plant phenology (foliage age).

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

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    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.

  2. Broadleaf deciduous forest counterbalanced the direct effect of climate on Holocene fire regime in hemiboreal/boreal region (NE Europe)

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    Feurdean, Angelica; Veski, Siim; Florescu, Gabriela; Vannière, Boris; Pfeiffer, Mirjam; O'Hara, Robert B.; Stivrins, Normunds; Amon, Leeli; Heinsalu, Atko; Vassiljev, Jüri; Hickler, Thomas

    2017-08-01

    Disturbances by fire are essential for the functioning of boreal/hemiboreal forests, but knowledge of long-term fire regime dynamics is limited. We analysed macrocharcoal morphologies and pollen of a sediment record from Lake Lielais Svētiņu (eastern Latvia), and in conjunction with fire traits analysis present the first record of Holocene variability in fire regime, fuel sources and fire types in boreal forests of the Baltic region. We found a phase of moderate to high fire activity during the cool and moist early (mean fire return interval; mFRI of ∼280 years; 11,700-7500 cal yr BP) and the late (mFRI of ∼190 years; 4500-0 cal yr BP) Holocene and low fire activity (mFRI of ∼630 years) during the Holocene Thermal Optimum (7500-4500 cal yr BP). Charcoal morphotypes and the pollen record show the predominance of frequent surface fires, occasionally transitioning to the crown during Pinus sylvestris-Betula boreal forests and less frequent surface fires during the dominance of temperate deciduous forests. In contrast to the prevailing opinion that fires in boreal forests are mostly low to moderate severity surface fires, we found evidence for common occurrence of stand-replacing crown fires in Picea abies canopy. Our results highlight that charcoal morphotypes analysis allows for distinguishing the fuel types and surface from crown fires, therefore significantly advancing our interpretation of fire regime. Future warmer temperatures and increase in the frequency of dry spells and abundant biomass accumulation can enhance the fire risk on the one hand, but will probably promote the expansion of broadleaf deciduous forests to higher latitudes, on the other hand. By highlighting the capability of broadleaf deciduous forests to act as fire-suppressing landscape elements, our results suggest that fire activity may not increase in the Baltic area under future climate change.

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

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

    2016-01-01

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

  4. The Effect of Pollution on Newly-Formed Particle Composition in Boreal Forest

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    Vaattovaara, Petri

    2010-05-01

    Petri Vaattovaara (1), Tuukka Petäjä (2), Jorma Joutsensaari (1), Pasi Miettinen (1), Boris Zaprudin (1,6), Aki Kortelainen (1), Juha Heijari (3,7), Pasi Yli-Pirilä (3), Pasi Aalto (2), Doug R. Worsnop (4), and Ari Laaksonen(1,5) (1) University of Eastern Finland, Finland (2) University of Helsinki, Finland (3) University of Eastern Finland, Finland (4) Aerodyne Research Inc., USA (5) Finnish Meteorological Institute, Finland (6) Currently at University of Turku, Finland (7) Currently at Maritime Research Centre, Finland Email address of the Corresponding author: Petri.Vaattovaara@uef.fi The geographical extent of the tropical, temperate and boreal forests is about 30% of the Earth's land surface. Those forests are located around the world in different climate zones effecting widely on atmospheric composition via new particle formation. The Boreal forests solely cover one third of the forests extent and are one of the largest vegetation environments, forming a circumpolar band throughout the northern hemisphere continents, with a high potential to affect climate processes [1]. In order to more fully understand the possible climatic effects of the forests, the properties of secondary organic aerosols (SOA) in varying conditions (e.g. a change in meteorological parameters or in the concentrations of biogenic and antropogenic trace gases) need to be better known. In this study, we applied the UFO-TDMA (ultrafine organic tandem differential mobility analyzer [2]) and the UFH-TDMA (ultrafine hygroscopicity tandem differential mobility analyzer [3]) methods parallel to shed light on the evolution of the nucleation and Aitken mode particle compositions (via physic-chemical properties) at a virgin boreal forest site in varying conditions. The measurements were carried out at Hyytiälä forest station in Northern Europe (Finland) during 15 spring nucleation events. We also carried out a statistical analysis using linear correlations in order to explain the variability in

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

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    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

  6. Polarimetric ALOS PALSAR Time Series in Mapping Biomass of Boreal Forests

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    Oleg Antropov

    2017-09-01

    Full Text Available Here, we examined multitemporal behavior of fully polarimetric SAR (PolSAR parameters at L-band in relation to the stem volume of boreal forests. The PolSAR parameters were evaluated in terms of their temporal consistency, inter-dependence and suitability for forest stem volume estimation across several seasonal conditions (frozen, thaw and unfrozen. The satellite SAR data were represented by a time series of PolSAR images acquired during several seasons in the years 2006 to 2009 by the ALOS PALSAR sensor. The study area was in central Finland, and represented a managed area in typical boreal mixed forest land. Utility of different PolSAR parameters, their temporal stability and cross-correlations were studied along with reference stand-level stem volume data from forest inventory. Further, two polarimetric parameters, cross-polarization backscatter and co-polarization coherence, were chosen for further investigation and stem volume retrieval. A relationship between forest stem volume and PolSAR parameters was established using the kNN regression approach. Ways of optimally combining PolSAR images were evaluated as well. For a single scene, best results were observed with polarimetric coherence (RMSE ≈ 38.8 m3/ha for scene acquired in frozen conditions. An RMSE of 40.8 m3/ha (42.9%, R2 = 0.66 was achieved for cross-polarization backscatter in the best case. Cross-polarization backscatter was a better predictor than polarimetric coherence for few summer scenes. Multitemporal aggregation of selected PolSAR scenes improved estimates for both studied PolSAR parameters. Stronger improvement was observed for coherence with RMSE down to 34 m3/ha (35.8%, R2 = 0.77 compared to 38.8–51.6 m3/ha (40.8–54.3% from separate scenes. Finally, the accuracy statistics reached RMSE of 32.2 m3/ha (34%, R2 = 0.79 when multitemporal HHVV coherence was combined with multitemporal HV-backscatter.

  7. 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 millennial time scales in the prolonged absence of fire.

  8. Fluxes of Dissolved Organic Carbon within Soils across a Boreal Forest Ecosystem Latitudinal Transect

    Science.gov (United States)

    Bowering, K.; Edwards, K.; Billings, S. A.; Skinner, A.; Warren, J.; Ziegler, S. E.

    2013-12-01

    The movement of dissolved organic carbon (DOC) can represent a significant flux of C within soils, and may be a critical flux of C from the terrestrial into the aquatic environment. Further, these fluxes can represent an important source of C to deeper mineral horizons where stabilization mechanisms may exist. However the quantity and quality of this C flux is largely unknown, and regulating factors that are influenced by climate and land-use change are poorly understood. This movement of C is of particular interest in the boreal forest, where large soil C stocks are vulnerable to the impacts of climate change. Laboratory experiments have demonstrated that warming, in the absence of moisture limitation, can increase the rate of production of DOC in soils directly through increased decomposition rates; however, this has been difficult to test under field conditions where seasonality, intact soil, and hydrological systems influence DOC production and movement. To assess the impact of climate warming on DOC fluxes occurring through the organic soil layer of the eastern North American boreal forest, we sampled passive lysimeters installed at 3 sites along a latitudinal transect in Newfoundland and Labrador, Canada. Separated by just over 5° latitude, mean annual temperature at these sites were 4°C, 2.1°C, and -0.5°C from lowest to highest latitude. Six lysimeters were sampled from each site and collections were made at least three times annually for two consecutive years (2011-2013). Soils tend to freeze over-winter in the high-latitude site whereas they rarely freeze in the low-latitude site. The low-latitude site also experiences more variable precipitation, with a longer snow-free season and more precipitation falling during single events. Rates of DOC flux increased with decreasing latitude, indicating greater DOC transport through soils in forests experiencing a warmer climate. DOC fluxes calculated over different seasonal time periods ranged from 4.6 to 20

  9. Using hyperspectral imagery to estimate forest floor consumption from wildfire in boreal forests of Alaska, USA

    Science.gov (United States)

    Sarah A. Lewis; Andrew T. Hudak; Roger D. Ottmar; Peter R. Robichaud; Leigh B. Lentile; Sharon M. Hood; James B. Cronan; Penny Morgan

    2011-01-01

    Wildfire is a major forest disturbance in interior Alaska that can both directly and indirectly alter ecological processes. We used a combination of pre- and post-fire forest floor depths and post-fire ground cover assessments measured in the field, and high-resolution airborne hyperspectral imagery, to map forest floor conditions after the 2004 Taylor Complex in...

  10. Mammalian Herbivores in the Boreal Forests: Their Numerical Fluctuations and Use by Man

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    Kjell Danell

    1998-12-01

    Full Text Available Within the boreal zone, there are about 50 native mammalian herbivore species that belong to the orders Artiodactyla, Rodentia, and Lagomorpha. Of these species, 31 occur in the Nearctic and 24 in the Palaearctic. Only six species occur in both regions. Species of the family Cervidae have probably been, and still are, the most important group for man, as they provide both meat and hides. Pelts from squirrels, muskrats, and hares were commercially harvested at the beginning of the century, but have less value today. The semi-domestic reindeer in the Palaearctic produces meat and hides on a commercial basis. It is also used for milking, to a limited extent, as is the semi-domestic moose in Russia. The Siberian musk deer is used for its musk and is raised in captivity in China. All species heavier than 1 kg are utilized by man, those with a body mass in the range 1 kg - 1 hg are sometimes used, and species lighter than 1 hg are rarely used. Here, we review the numerical fluctuations in terms of periodicity and amplitude, based on an extensive data set found in the literature, especially from the former Soviet Union. Current understanding of the underlying factors behind the population fluctuations is briefly reviewed. Management and conservation aspects of the mammalian herbivores in the boreal zone are also discussed. We conclude that there is a challenge to manage the forests for the mammalian herbivores, but there is also a challenge to manage the populations of mammalian herbivores for the forests.

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

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    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

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

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    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.

  13. Patterns of NPP, GPP, respiration, and NEP during boreal forest succession

    Science.gov (United States)

    Goulden, M.L.; Mcmillan, A.M.S.; Winston, G.C.; Rocha, A.V.; Manies, K.L.; Harden, J.W.; Bond-Lamberty, B. P.

    2011-01-01

    We combined year-round eddy covariance with biometry and biomass harvests along a chronosequence of boreal forest stands that were 1, 6, 15, 23, 40, 74, and 154 years old to understand how ecosystem production and carbon stocks change during recovery from stand-replacing crown fire. Live biomass (Clive) was low in the 1 and 6 year old stands, and increased following a logistic pattern to high levels in the 74 and 154year old stands. Carbon stocks in the forest floor (Cforest floor) and coarse woody debris (CCWD) were comparatively high in the 1year old stand, reduced in the 6 through 40year old stands, and highest in the 74 and 154year old stands. Total net primary production (TNPP) was reduced in the 1 and 6year old stands, highest in the 23 through 74year old stands and somewhat reduced in the 154year old stand. The NPP decline at the 154year old stand was related to increased autotrophic respiration rather than decreased gross primary production (GPP). Net ecosystem production (NEP), calculated by integrated eddy covariance, indicated the 1 and 6 year old stands were losing carbon, the 15year old stand was gaining a small amount of carbon, the 23 and 74year old stands were gaining considerable carbon, and the 40 and 154year old stands were gaining modest amounts of carbon. The recovery from fire was rapid; a linear fit through the NEP observations at the 6 and 15year old stands indicated the transition from carbon source to sink occurred within 11-12 years. The NEP decline at the 154year old stand appears related to increased losses from Clive by tree mortality and possibly from Cforest floor by decomposition. Our findings support the idea that NPP, carbon production efficiency (NPP/GPP), NEP, and carbon storage efficiency (NEP/TNPP) all decrease in old boreal stands. ?? 2010 Blackwell Publishing Ltd.

  14. Canopy uptake dominates nighttime carbonyl sulfide fluxes in a boreal forest

    Science.gov (United States)

    Kooijmans, Linda M. J.; Maseyk, Kadmiel; Seibt, Ulli; Sun, Wu; Vesala, Timo; Mammarella, Ivan; Kolari, Pasi; Aalto, Juho; Franchin, Alessandro; Vecchi, Roberta; Valli, Gianluigi; Chen, Huilin

    2017-09-01

    Nighttime vegetative uptake of carbonyl sulfide (COS) can exist due to the incomplete closure of stomata and the light independence of the enzyme carbonic anhydrase, which complicates the use of COS as a tracer for gross primary productivity (GPP). In this study we derived nighttime COS fluxes in a boreal forest (the SMEAR II station in Hyytiälä, Finland; 61°51' N, 24°17' E; 181 m a.s.l.) from June to November 2015 using two different methods: eddy-covariance (EC) measurements (FCOS-EC) and the radon-tracer method (FCOS-Rn). The total nighttime COS fluxes averaged over the whole measurement period were -6.8 ± 2.2 and -7.9 ± 3.8 pmol m-2 s-1 for FCOS-Rn and FCOS-EC, respectively, which is 33-38 % of the average daytime fluxes and 21 % of the total daily COS uptake. The correlation of 222Rn (of which the source is the soil) with COS (average R2 = 0.58) was lower than with CO2 (0.70), suggesting that the main sink of COS is not located at the ground. These observations are supported by soil chamber measurements that show that soil contributes to only 34-40 % of the total nighttime COS uptake. We found a decrease in COS uptake with decreasing nighttime stomatal conductance and increasing vapor-pressure deficit and air temperature, driven by stomatal closure in response to a warm and dry period in August. We also discuss the effect that canopy layer mixing can have on the radon-tracer method and the sensitivity of (FCOS-EC) to atmospheric turbulence. Our results suggest that the nighttime uptake of COS is mainly driven by the tree foliage and is significant in a boreal forest, such that it needs to be taken into account when using COS as a tracer for GPP.

  15. 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.

  16. Effects of Lakes on Wildfire Activity in the Boreal Forests of Saskatchewan, Canada

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    Scott E. Nielsen

    2016-11-01

    Full Text Available Large lakes can act as firebreaks resulting in distinct patterns in the forest mosaic. Although this is well acknowledged, much less is known about how wildfire is affected by different landscape measures of water and their interactions. Here we examine how these factors relate to historic patterns of wildfire over a 35-year period (1980–2014 for the boreal forest of Saskatchewan, Canada. This includes the amount of water in different-sized neighborhoods, the presence of islands, and the direction, distance, and shape of nearest lake of different sizes. All individual factors affected wildfire presence, with lake sizes ≥5000 ha and amount of water within a 1000-ha surrounding area the most supported spatial scales. Overall, wildfires were two-times less likely on islands, more likely further from lakes that were circular in shape, and in areas with less surrounding water. Interactive effects were common, including the effect of direction to lake as a function of distance from lakeshore and amount of surrounding water. Our results point to a strong, but complex, bottom-up control of local wildfire activity based on the configuration of natural firebreaks. In fact, fire rotation periods predicted for one area varied more than 15-fold (<47 to >700 years depending on local patterns in lakes. Old-growth forests within this fire-prone ecosystem are therefore likely to depend on the surrounding configuration of larger lakes.

  17. Survival of Adult Songbirds in Boreal Forest Landscapes Fragmented by Clearcuts and Natural Openings

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    Darroch M. Whitaker

    2008-06-01

    Full Text Available There exists little information on demographic responses of boreal songbirds to logging. We conducted a 4-yr (2003-2006 songbird mark-recapture study in western Newfoundland, where land cover is a naturally heterogeneous mosaic of productive spruce-fir forest, stunted taiga, and openings such as bogs, fens, and riparian zones. We compared apparent survival and rate of transience for adults of 14 species between areas having forests fragmented primarily by either natural openings or 3-7 yr-old clearcuts. Data were collected on three landscape pairs, with birds being marked on three 4-6 ha netting sites on each landscape (total = 18 netting sites. Survival rates were estimated using multi-strata mark-recapture models with landscape types specified as model strata. Landscape type was retained in the best model for only two species, Ruby-crowned Kinglet and Yellow-rumped Warbler, in both cases indicating lower apparent survival in landscapes having clearcuts. Though parameter estimates suggested lower survival in clearcut landscapes for several species, meta-analysis across all species detected no general difference between landscape types. Further, we did not detect any relation between landscape differences in survival and a species' habitat affinity, migratory strategy, or the proportion of transients in its population. Although sensitivity to logging was limited, we observed high interspecific variation in rates of breeding season apparent survival (48% [Dark-eyed Junco] to 100% [several species], overwinter apparent survival (0.3% [Ruby-crowned Kinglet] to 86.5% [Gray Jay], and transience (≈0% [several species] to 61% [Ruby-crowned Kinglet in clearcut landscapes]. For Lincoln's and White-throated Sparrows, over-winter apparent survival was >2× higher for males than females, and rate of transience was > 8× higher for White-throated Sparrow males than females. Moderately male-biased sex ratios suggested that both lower mortality and higher

  18. The Uncertainty of Biomass Estimates from Modeled ICESat-2 Returns Across a Boreal Forest Gradient

    Science.gov (United States)

    Montesano, P. M.; Rosette, J.; Sun, G.; North, P.; Nelson, R. F.; Dubayah, R. O.; Ranson, K. J.; Kharuk, V.

    2014-01-01

    The Forest Light (FLIGHT) radiative transfer model was used to examine the uncertainty of vegetation structure measurements from NASA's planned ICESat-2 photon counting light detection and ranging (LiDAR) instrument across a synthetic Larix forest gradient in the taiga-tundra ecotone. The simulations demonstrate how measurements from the planned spaceborne mission, which differ from those of previous LiDAR systems, may perform across a boreal forest to non-forest structure gradient in globally important ecological region of northern Siberia. We used a modified version of FLIGHT to simulate the acquisition parameters of ICESat-2. Modeled returns were analyzed from collections of sequential footprints along LiDAR tracks (link-scales) of lengths ranging from 20 m-90 m. These link-scales traversed synthetic forest stands that were initialized with parameters drawn from field surveys in Siberian Larix forests. LiDAR returns from vegetation were compiled for 100 simulated LiDAR collections for each 10 Mg · ha(exp -1) interval in the 0-100 Mg · ha(exp -1) above-ground biomass density (AGB) forest gradient. Canopy height metrics were computed and AGB was inferred from empirical models. The root mean square error (RMSE) and RMSE uncertainty associated with the distribution of inferred AGB within each AGB interval across the gradient was examined. Simulation results of the bright daylight and low vegetation reflectivity conditions for collecting photon counting LiDAR with no topographic relief show that 1-2 photons are returned for 79%-88% of LiDAR shots. Signal photons account for approximately 67% of all LiDAR returns, while approximately 50% of shots result in 1 signal photon returned. The proportion of these signal photon returns do not differ significantly (p greater than 0.05) for AGB intervals greater than 20 Mg · ha(exp -1). The 50m link-scale approximates the finest horizontal resolution (length) at which photon counting LiDAR collection provides strong model

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

    Science.gov (United States)

    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.

  20. Visualizing the Forest in a Boreal Forest Landscape—The Perspective of Swedish Municipal Comprehensive Planning

    Directory of Open Access Journals (Sweden)

    Camilla Thellbro

    2017-05-01

    Full Text Available At the international policy level, there is a clear link between access to information about forests and the work towards sustainable land use. However, involving forests in planning for sustainable development (SuD at the Swedish local level, by means of municipal comprehensive planning (MCP, is complicated by sector structure and legislation. Currently, there is a gap or hole in the MCP process when it comes to use and access to knowledge about forest conditions and forest land use. This hole limits the possibilities to formulate well-informed municipal visions and goals for sustainable forest land use as well as for overall SuD. Here we introduce an approach for compilation and presentation of geographic information to increase the preconditions for integrating forest information into Swedish MCP. We produce information about forest ownership patterns and forest conditions in terms of age and significant ecological and social values in forests for a case study municipality. We conclude that it is possible to effectively compile geographic and forest-related information to fill the hole in the municipal land use map. Through our approach, MCP could be strengthened as a tool for overall land use planning and hence as a base in SuD planning.

  1. The effect of boreal forest canopy to reflectance of snow covered terrain based on airborne imaging spectrometer observations

    Science.gov (United States)

    Heinilä, Kirsikka; Salminen, Miia; Pulliainen, Jouni; Cohen, Juval; Metsämäki, Sari; Pellikka, Petri

    2014-04-01

    Optical remote sensing methods for mapping of the seasonal snow cover are often obstructed by the masking effect of forest canopy. Therefore, optical algorithms tend to underestimate the amount of snow cover in forested regions. In this paper, we investigate the influence of boreal forest stand characteristics on the observed scene reflectance under full dry snow cover conditions by applying an advantageous experimental setup combining airborne hyperspectral imaging and LIDAR data sets from a test region in Sodankylä, northern Finland. This is particularly useful to the understanding of the composition of the mixed satellite scene reflectance behavior and it is relation to the natural ground targets' spectral signatures.

  2. Regional Instability in the Abundance of Open Stands in the Boreal Forest of Eastern Canada

    Directory of Open Access Journals (Sweden)

    Rija Rapanoela

    2016-05-01

    Full Text Available Fires are a key disturbance of boreal forests. In fact, they are the main source of renewal and evolution for forest stands. The variability of fire through space and time results in a diversified forest mosaic, altering their species composition, structure and productivity. A resilient forest is assumed to be in a state of dynamic equilibrium with the fire regime, so that the composition, age structure and succession stages of forests should be consistent with the fire regime. Dense spruce-moss stands tend, however, to diminish in favour of more open stands similar to spruce-lichen stands when subjected to more frequent and recurring disturbances. This study therefore focused on the effects of spatial and temporal variations in burn rates on the proportion of open stands over a large geographic area (175,000 km2 covered by black spruce (Picea mariana (Mill. Britton, Sterns, Poggenb.. The study area was divided into 10 different zones according to burn rates, as measured using fire-related data collected between 1940 and 2006. To test if the abundance of open stands was unstable over time and not in equilibrium with the current fire regime, forest succession was simulated using a landscape dynamics model that showed that the abundance of open stands should increase progressively over time in zones where the average burn rate is high. The proportion of open stands generated during a specific historical period is correlated with the burn rate observed during the same period. Rising annual burn rates over the past two decades have thereby resulted in an immediate increase in the proportion of open stands. There is therefore a difference between the current proportion of open stands and the one expected if vegetation was in equilibrium with the disturbance regime, reflecting an instability that may significantly impact the way forest resources are managed. It is apparent from this study that forestry planning should consider the risks associated

  3. Climate change adaptation and sustainable forest management in the boreal forest

    Energy Technology Data Exchange (ETDEWEB)

    Ogden, A.E.E.

    2008-07-01

    Recent interest in sustainable forest management planning coincides with increased public awareness of climate change. This thesis examined how strategic forestry plans for the Champagne and Aishihik First Nations Traditional Territory in the Yukon are incorporating climate change. A climate-driven, large-scale spruce bark beetle disturbance in the area has been driving forest management planning. However, climate change considerations have not been directly addressed in the planning process. This study identified 24 adaptation options for implementing in forest development areas to achieve regional goals of forest management across three scenarios of climate change. In addition, the performance of alternative strategies to re-establish forests was assessed. Management policies and practices that adapt to climate change were identified and a typology was proposed for classifying sustainable forest management plans according to how they address and manage climate change risks. The plans incorporate best management practices for sustainable forest management that are consistent with climate adaptation responses. A structured decision making (SDM) approach showed that forestry planning processes have yet to come to terms with the risks that climate change may pose to the ability of forest managers to achieve the stated goals and objectives of sustainable forest management plans.

  4. Biased representation of disturbance rates in the roadside sampling frame in boreal forests: implications for monitoring design

    Directory of Open Access Journals (Sweden)

    Steven L. Van Wilgenburg

    2015-12-01

    Full Text Available The North American Breeding Bird Survey (BBS is the principal source of data to inform researchers about the status of and trend for boreal forest birds. Unfortunately, little BBS coverage is available in the boreal forest, where increasing concern over the status of species breeding there has increased interest in northward expansion of the BBS. However, high disturbance rates in the boreal forest may complicate roadside monitoring. If the roadside sampling frame does not capture variation in disturbance rates because of either road placement or the use of roads for resource extraction, biased trend estimates might result. In this study, we examined roadside bias in the proportional representation of habitat disturbance via spatial data on forest "loss," forest fires, and anthropogenic disturbance. In each of 455 BBS routes, the area disturbed within multiple buffers away from the road was calculated and compared against the area disturbed in degree blocks and BBS strata. We found a nonlinear relationship between bias and distance from the road, suggesting forest loss and forest fires were underrepresented below 75 and 100 m, respectively. In contrast, anthropogenic disturbance was overrepresented at distances below 500 m and underrepresented thereafter. After accounting for distance from road, BBS routes were reasonably representative of the degree blocks they were within, with only a few strata showing biased representation. In general, anthropogenic disturbance is overrepresented in southern strata, and forest fires are underrepresented in almost all strata. Similar biases exist when comparing the entire road network and the subset sampled by BBS routes against the amount of disturbance within BBS strata; however, the magnitude of biases differed. Based on our results, we recommend that spatial stratification and rotating panel designs be used to spread limited BBS and off-road sampling effort in an unbiased fashion and that new BBS routes

  5. Salvage logging following fires can minimize boreal caribou habitat loss while maintaining forest quotas: An example of compensatory cumulative effects.

    Science.gov (United States)

    Beguin, Julien; McIntire, Eliot J B; Raulier, Frédéric

    2015-11-01

    Protected area networks are the dominant conservation approach that is used worldwide for protecting biodiversity. Conservation planning in managed forests, however, presents challenges when endangered species use old-growth forests targeted by the forest industry for timber supply. In many ecosystems, this challenge is further complicated by the occurrence of natural disturbance events that disrupt forest attributes at multiple scales. Using spatially explicit landscape simulation experiments, we gather insights into how these large scale, multifaceted processes (fire risk, timber harvesting and the amount of protected area) influenced both the persistence of the threatened boreal caribou and the level of timber supply in the boreal forest of eastern Canada. Our result showed that failure to account explicitly and a priori for fire risk in the calculation of timber supply led to an overestimation of timber harvest volume, which in turn led to rates of cumulative disturbances that threatened both the long-term persistence of boreal caribou and the sustainability of the timber supply itself. Salvage logging, however, allowed some compensatory cumulative effects. It minimised the reductions of timber supply within a range of ∼10% while reducing the negative impact of cumulative disturbances caused by fire and logging on caribou. With the global increase of the human footprint on forest ecosystems, our approach and results provide useful tools and insights for managers to resolve what often appear as lose-lose situation between the persistence of species at risk and timber harvest in other forest ecosystems. These tools contribute to bridge the gap between conservation and forest management, two disciplines that remain too often disconnected in practice. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. 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

  7. The selection of small forest hollows for pollen analysis in boreal and temperate forest regions

    DEFF Research Database (Denmark)

    Overballe-Petersen, Mette V; Bradshaw, Richard H.W.

    2011-01-01

    Small forest hollows represent a specialised site type for pollen analysis, since they mainly record the vegetation within an approximate radius of 20-100 m from the hollow. We discuss how to choose the most appropriate small forest hollow for pollen analysis. Hollow size, site topography, location...

  8. UAV-BASED PHOTOGRAMMETRIC POINT CLOUDS AND HYPERSPECTRAL IMAGING FOR MAPPING BIODIVERSITY INDICATORS IN BOREAL FORESTS

    Directory of Open Access Journals (Sweden)

    N. Saarinen

    2017-10-01

    Full Text Available Biodiversity is commonly referred to as species diversity but in forest ecosystems variability in structural and functional characteristics can also be treated as measures of biodiversity. Small unmanned aerial vehicles (UAVs provide a means for characterizing forest ecosystem with high spatial resolution, permitting measuring physical characteristics of a forest ecosystem from a viewpoint of biodiversity. The objective of this study is to examine the applicability of photogrammetric point clouds and hyperspectral imaging acquired with a small UAV helicopter in mapping biodiversity indicators, such as structural complexity as well as the amount of deciduous and dead trees at plot level in southern boreal forests. Standard deviation of tree heights within a sample plot, used as a proxy for structural complexity, was the most accurately derived biodiversity indicator resulting in a mean error of 0.5 m, with a standard deviation of 0.9 m. The volume predictions for deciduous and dead trees were underestimated by 32.4 m3/ha and 1.7 m3/ha, respectively, with standard deviation of 50.2 m3/ha for deciduous and 3.2 m3/ha for dead trees. The spectral features describing brightness (i.e. higher reflectance values were prevailing in feature selection but several wavelengths were represented. Thus, it can be concluded that structural complexity can be predicted reliably but at the same time can be expected to be underestimated with photogrammetric point clouds obtained with a small UAV. Additionally, plot-level volume of dead trees can be predicted with small mean error whereas identifying deciduous species was more challenging at plot level.

  9. Uav-Based Photogrammetric Point Clouds and Hyperspectral Imaging for Mapping Biodiversity Indicators in Boreal Forests

    Science.gov (United States)

    Saarinen, N.; Vastaranta, M.; Näsi, R.; Rosnell, T.; Hakala, T.; Honkavaara, E.; Wulder, M. A.; Luoma, V.; Tommaselli, A. M. G.; Imai, N. N.; Ribeiro, E. A. W.; Guimarães, R. B.; Holopainen, M.; Hyyppä, J.

    2017-10-01

    Biodiversity is commonly referred to as species diversity but in forest ecosystems variability in structural and functional characteristics can also be treated as measures of biodiversity. Small unmanned aerial vehicles (UAVs) provide a means for characterizing forest ecosystem with high spatial resolution, permitting measuring physical characteristics of a forest ecosystem from a viewpoint of biodiversity. The objective of this study is to examine the applicability of photogrammetric point clouds and hyperspectral imaging acquired with a small UAV helicopter in mapping biodiversity indicators, such as structural complexity as well as the amount of deciduous and dead trees at plot level in southern boreal forests. Standard deviation of tree heights within a sample plot, used as a proxy for structural complexity, was the most accurately derived biodiversity indicator resulting in a mean error of 0.5 m, with a standard deviation of 0.9 m. The volume predictions for deciduous and dead trees were underestimated by 32.4 m3/ha and 1.7 m3/ha, respectively, with standard deviation of 50.2 m3/ha for deciduous and 3.2 m3/ha for dead trees. The spectral features describing brightness (i.e. higher reflectance values) were prevailing in feature selection but several wavelengths were represented. Thus, it can be concluded that structural complexity can be predicted reliably but at the same time can be expected to be underestimated with photogrammetric point clouds obtained with a small UAV. Additionally, plot-level volume of dead trees can be predicted with small mean error whereas identifying deciduous species was more challenging at plot level.

  10. 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.

  11. Mapping Above- and Below-Ground Carbon Pools in Boreal Forests: The Case for Airborne Lidar.

    Directory of Open Access Journals (Sweden)

    Terje Kristensen

    Full Text Available 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.

  12. Improving the modeling of the seasonal carbon cycle of the boreal forest with chlorophyll fluorescence measurements

    Science.gov (United States)

    Thum, Tea; Aalto, Tuula; Aurela, Mika; Laurila, Tuomas; Zaehle, Sönke

    2014-05-01

    The boreal ecosystems are characterized a very strong seasonal cycle and they are very sensitive to the climatic variables. The vegetation's deep wintertime dormancy requires a long recovery time during spring before the plants reach their full photosynthetic capacity. During this recovery time the plants are highly susceptible the night frosts. The transition period is different during spring and autumn for the evergreen plants. During spring there is plenty of light, but cold air temperatures inhibit the photosynthesis. The plants therefore experience to high stress levels, as they need to protect their photosynthetic apparatus from intense light. In autumn the air temperature and light level decrease more concurrently. To have a realistic presentation of the carbon cycle in boreal forests it is important to have these characteristics properly modeled, so that also the implications of changing seasonality under climate change can be more reliably predicted. In this study, we focus on the CO2 exchange of a Scots pine forest Sodankylä located in Finnish Lapland, 100 km north from the Arctic Circle. Micrometeorological flux measurements provide information about the exchanges of carbon, energy and water between atmosphere and vegetation. To complement these fluxes, we use dark-adapted chlorophyll fluorescence (CF) measurements, which is an optical measurement and tracks the development of the photosynthetic capacity. These two approaches combined together are very useful when we want to improve the modeling of the forest's CO2 exchange. We used two models that describe the photosynthesis with the biochemical model of Farquhar et al. The FMI-CANOPY is a canopy level model that is feasible to use in parameter estimation. We used the CF measurements of Fv/Fm, that is a measure of the maximum photosynthetic capacity, to include a seasonal development in the base rate of the maximum carboxylation rate (Vc(max)) in FMI-CANOPY. The simulation results matched the

  13. Population limitation of the northern red-backed vole in the boreal forests of northern Canada.

    Science.gov (United States)

    Boonstra, Rudy; Krebs, Charles J

    2006-11-01

    1. Across the vast boreal forests of North America, no population cycles in Clethrionomys species occur. In Eurasia, by contrast, some Clethrionomys populations of the same species undergo regular 3-5-year cycles. We examined the effects of nutrients, food, competitors, predators and climate on population limitation in the northern red-backed vole (Clethrionomys rutilus Pallas) in the south-western Yukon to determine why this difference occurs. 2. From 1986 to 1996 we added food, reduced large mammal predators and excluded snowshoe hares (Lepus americanus Erxleben) from large plots and found that none of these manipulations affected red-backed vole abundance. Adding nutrients as nitrogen, phosphorus and potassium (NPK) fertilizer had a slight negative effect, probably acting through a reduction in dwarf shrub productivity caused by competition from grasses. 3. We monitored weasel populations directly through trapping and indirectly through snow tracking. Predation by these vole specialists was irrelevant as a limiting factor most of the time because voles in this area do not reach the densities needed to sustain weasel populations. Other boreal forest mammal and bird predators did not focus on red-backed voles. However, when red-backed vole populations increased in the forest and Microtus voles also increased in the meadows, weasel populations increased and may have temporarily depressed red-backed voles in winter. 4. We monitored one major potential food, white spruce seeds, but seed fall was not related to population changes in red-backed voles, even after mast years. 5. We assessed the impact of weather variables, and the average depth of the snow pack during winter (October-March) was correlated directly with vole demography, having both direct effects in that year and delayed effects in the following year. 6. Our long-term trapping data (1973-96) indicate that Clethrionomys populations fluctuated, with peaks following hare peaks by 2-3 years. 7. We propose

  14. Changes in microbial communities and soil carbon dynamics across a fire chronosequence in an Alaskan boreal forest

    Science.gov (United States)

    Dooley, S. R.; Treseder, K. K.

    2010-12-01

    Boreal ecosystems contain an estimated 30-40% of global terrestrial carbon, the majority of which is stored in soil organic matter. Wildfires are a frequent disturbance in boreal forests and have the potential to influence soil carbon dynamics. The frequency and intensity of fires in boreal ecosystems is predicted to increase under global change conditions, highlighting the importance of understanding the relationship between fire and soil carbon dynamics. Theoretical and modeling work suggests that heterotrophic respiration may increase following fires due to higher soil temperatures, further augmenting carbon losses after fires. Alternatively, post-fire changes in microbial abundance and soil properties may inhibit decomposition and decrease carbon emissions from soils. We tested the hypothesis that microbial abundance constrains decomposition in post-fire soils using a fire chronosequence in upland boreal forests of Alaska. This chronosequence includes sites that burned in 2010, 2004, 1999, 1987, and 1956. As a control, we also sampled from a mature black spruce stand that has not burned in over 80 years. To test our hypothesis, we characterized changes in soil nutrients, microbial abundance, and microbial respiration along the chronosequence during the summer of 2010. With the exception of the 2010 burn site, soil ammonium and nitrate increased with time since fire and were highest at the control site. In addition, microbial abundance increased 88% from the 2004 burn site to the control site. Changes in microbial respiration across the chronosequence followed a similar pattern, increasing from 61 to 1125 μg C g-1 soil in the 2004 burn site and control site, respectively. Surprisingly, microbial abundance and respiration did not differ significantly between the 2010 burn site and the control site. These data suggest that very recent burn sites may have an influx of labile carbon compounds into soil that sustains microbial activity. Overall, we found little

  15. 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.

  16. Biogeographic variation in evergreen conifer needle longevity and impacts on boreal forest carbon cycle projections.

    Science.gov (United States)

    Reich, Peter B; Rich, Roy L; Lu, Xingjie; Wang, Ying-Ping; Oleksyn, Jacek

    2014-09-23

    Leaf life span is an important plant trait associated with interspecific variation in leaf, organismal, and ecosystem processes. We hypothesized that intraspecific variation in gymnosperm needle traits with latitude reflects both selection and acclimation for traits adaptive to the associated temperature and moisture gradient. This hypothesis was supported, because across 127 sites along a 2,160-km gradient in North America individuals of Picea glauca, Picea mariana, Pinus banksiana, and Abies balsamea had longer needle life span and lower tissue nitrogen concentration with decreasing mean annual temperature. Similar patterns were noted for Pinus sylvestris across a north-south gradient in Europe. These differences highlight needle longevity as an adaptive feature important to ecological success of boreal conifers across broad climatic ranges. Additionally, differences in leaf life span directly affect annual foliage turnover rate, which along with needle physiology partially regulates carbon cycling through effects on gross primary production and net canopy carbon export. However, most, if not all, global land surface models parameterize needle longevity of boreal evergreen forests as if it were a constant. We incorporated temperature-dependent needle longevity and %nitrogen, and biomass allocation, into a land surface model, Community Atmosphere Biosphere Land Exchange, to assess their impacts on carbon cycling processes. Incorporating realistic parameterization of these variables improved predictions of canopy leaf area index and gross primary production compared with observations from flux sites. Finally, increasingly low foliage turnover and biomass fraction toward the cold far north indicate that a surprisingly small fraction of new biomass is allocated to foliage under such conditions.

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

    Science.gov (United States)

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

    2017-04-01

    There is a pressing need to understand how changing climate interacts with land-use change to affect predator-prey interactions in fragmented landscapes. This is particularly true in boreal ecosystems facing fast climate change and intensification in forestry practices. Here, we investigated the relative influence of autumn climate and habitat quality on the food-storing behaviour of a generalist predator, the pygmy owl, using a unique data set of 15 850 prey items recorded in western Finland over 12 years. Our results highlighted strong effects of autumn climate (number of days with rainfall and with temperature prey biomass stored, (ii) the number of bank voles (main prey) stored, and (iii) the scaled mass index of pygmy owls. Increasing proportions of old spruce forests strengthened the functional response of owls to variations in vole abundance and were more prone to switch from main prey to alternative prey (passerine birds) depending on local climate conditions. High-quality habitat may allow pygmy owls to buffer negative effects of inclement weather and cyclic variation in vole abundance. Additionally, our results evidenced sex-specific trends in body condition, as the scaled mass index of smaller males increased while the scaled mass index of larger females decreased over the study period, probably due to sex-specific foraging strategies and energy requirements. Long-term temporal stability in local vole abundance refutes the hypothesis of climate-driven change in vole abundance and suggests that rainier autumns could reduce the vulnerability of small mammals to predation by pygmy owls. As small rodents are key prey species for many predators in northern ecosystems, our findings raise concern about the impact of global change on boreal food webs through changes in main prey vulnerability. © 2016 John Wiley & Sons Ltd.

  18. Fire-induced changes in boreal forest canopy volume and soil organic matter from multi-temporal airborne lidar

    Science.gov (United States)

    Alonzo, M.; Cook, B.; Andersen, H. E.; Babcock, C. R.; Morton, D. C.

    2016-12-01

    Fire in boreal forests initiates a cascade of biogeochemical and biophysical processes. Over typical fire return intervals, net radiative forcing from boreal forest fires depends on the offsetting impacts of greenhouse gas emissions and post-fire changes in land surface albedo. Whether boreal forest fires warm or cool the climate over these multi-decadal intervals depends on the magnitude of fire emissions and the time scales of decomposition, albedo changes, and forest regrowth. Our understanding of vegetation and surface organic matter (SOM) changes from boreal forest fires is shaped by field measurements and moderate resolution remote sensing data. Intensive field plot measurements offer detailed data on overstory, understory, and SOM changes from fire, but sparse plot data can be difficult to extend across the heterogeneous boreal forest landscape. Conversely, satellite measurements of burn severity are spatially extensive but only provide proxy measures of fire effects. In this research, we seek to bridge the scale gap between existing intensive and extensive methods using a combination of airborne lidar data and time series of Landsat data to evaluate pre- and post-fire conditions across Alaska's Kenai Peninsula. Lidar-based estimates of pre-fire stand structure and composition were essential to characterize the loss of canopy volume from fires between 2001 and 2014, quantify transitions from live to dead standing carbon pools, and isolate vegetation recovery following fire over 1 to 13 year time scales. Results from this study demonstrate the utility of lidar for estimating pre-fire structure and species composition at the scale of individual tree crowns. Multi-temporal airborne lidar data also provide essential insights regarding the heterogeneity of canopy and SOM losses at a sub-Landsat pixel scale. Fire effects are forest-structure and species dependent with variable temporal lags in carbon release due to delayed mortality (>5 years post fire) and

  19. Variation of snow cover ablation in the boreal forest: A sensitivity study on the effects of conifer canopy

    Science.gov (United States)

    Davis, R. E.; Hardy, J. P.; Ni, W.; Woodcock, C.; McKenzie, J. C.; Jordan, R.; Li, X.

    1997-12-01

    The duration and meteorological history of winter and thaw periods in the boreal forest affect carbon exchange during the growing season. Characteristics of conifer canopies exert important control on the energy exchange at the forest floor, which in turn controls snow cover processes such as melting. This analysis investigated the role of the conifer tree characteristics, including height and canopy density. Canopy and snow models estimated radiation incoming to the snow surface, the net energy budget of the snow, and melting rates of snow cover under conifer forests with different canopy density and tree height. This analysis assumed that canopy effects dominated snow surface energy exchange under conifers in the boreal forest. We used data layers of forest characteristics from the Boreal Ecosystem-Atmosphere Study (BOREAS) modeling subareas in Saskatchewan and Manitoba to guide the choice of modeled tree height and canopy density. Modeled stand characteristics assumed random location of trees and used a uniform tree height within a stand and regular crown geometry scaled to tree height. Measurements during winter and thaw in 1994 of incoming solar and longwave radiation, humidity, and wind speed above the forest canopy provided input to the models, along with air temperature measured in the canopy. Results showed the importance of canopy density and tree height as the first-order controls on cumulative incoming solar radiation at the forest floor for the range of these variables in the BOREAS test area. The combined canopy and snow models showed a large range of snow ablation within conifers, which showed the trade-offs between canopy density and tree height. Solar fluxes dominated the net transfer of energy to the snow in the north, while sensible heat exchange, net solar, and net longwave radiation played important roles in the south.

  20. Variation in Trembling Aspen and White Spruce Wood Quality Grown in Mixed and Single Species Stands in the Boreal Mixedwood Forest

    Directory of Open Access Journals (Sweden)

    Francis De Araujo

    2015-05-01

    Full Text Available The Canadian boreal forest is largely represented by mixed wood forests of white spruce (Picea glauca (Moench Voss and trembling aspen (Populus tremuloides Michx. In this study, a total of 300 trees originating from three sites composed of trembling aspen and white spruce with varying compositions were investigated for wood quality traits: one site was composed mainly of aspen, one mainly of spruce and a third was a mixed site. Four wood quality traits were examined: wood density, microfibril angle (MFA, fibre characteristics, and cell wall chemistry. Social classes were also determined for each site in an attempt to provide a more in-depth comparison. Wood density showed little variation among sites for both species, with only significant differences occurring between social classes. The aspen site showed statistically lower MFAs than the aspen from the mixed site, however, no differences were observed when comparing spruce. Fibre characteristics were higher in the pure species sites for both species. There were no differences in carbohydrate contents across sites, while lignin content varied. Overall, the use of social classes did not refine the characterization of sites.

  1. NPP Multi-Biome: Grassland, Boreal Forest, and Tropical Forest Sites, 1939-1996, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set contains one data file (.csv format) that provides net primary productivity (NPP) estimates for 34 grasslands, 14 tropical forests, and 5...

  2. 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

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

    Science.gov (United States)

    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. 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. 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

  6. 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

    2012-12-01

    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

  7. Sources of long-lived atmospheric VOCs at the rural boreal forest site, SMEAR II

    Science.gov (United States)

    Patokoski, J.; Ruuskanen, T. M.; Kajos, M. K.; Taipale, R.; Rantala, P.; Aalto, J.; Ryyppö, T.; Nieminen, T.; Hakola, H.; Rinne, J.

    2015-12-01

    In this study a long-term volatile organic compound (VOCs) concentration data set, measured at the SMEAR II (Station for Measuring Ecosystem-Atmosphere Relations) boreal forest site in Hyytiälä, Finland during the years 2006-2011, was analyzed in order to identify source areas and profiles of the observed VOCs. VOC mixing ratios were measured using proton transfer reaction mass spectrometry. Four-day HYSPLIT 4 (Hybrid Single Particle Lagrangian Integrated Trajectory) backward trajectories and the Unmix 6.0 receptor model were used for source area and source composition analysis. Two major forest fire events in Russia took place during the measurement period. The effect of these fires was clearly visible in the trajectory analysis, lending confidence to the method employed with this data set. Elevated volume mixing ratios (VMRs) of non-biogenic VOCs related to forest fires, e.g. acetonitrile and aromatic VOCs, were observed. Ten major source areas for long-lived VOCs (methanol, acetonitrile, acetaldehyde, acetone, benzene, and toluene) observed at the SMEAR II site were identified. The main source areas for all the targeted VOCs were western Russia, northern Poland, Kaliningrad, and the Baltic countries. Industrial areas in northern continental Europe were also found to be source areas for certain VOCs. Both trajectory and receptor analysis showed that air masses from northern Fennoscandia were less polluted with respect to both the VOCs studied and other trace gases (CO, SO2 and NOx), compared to areas of eastern and western continental Europe, western Russia, and southern Fennoscandia.

  8. 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.

  9. Shifts in microbial communities and soil nutrients along a fire chronosequence in Alaskan boreal forest

    Science.gov (United States)

    Treseder, K. K.; Mack, M. C.; Cross, A.

    2002-12-01

    Fires are important pathways of carbon loss from boreal forests, while microbial communities form equally important mechanisms for carbon accumulation between fires. We used a chronosequence in Alaska to examine shifts in microbial abundance and community composition in the several decades following severe fire, and then related these responses to soil characteristics in the same sites. The sites are located in upland forests near Delta Junction, Alaska, and represent stages at 3-, 15-, 45-, and over 100-yr following fire. Plant communities shift from herbaceous species in the youngest site, to deciduous shrubs and trees (e.g. Populus tremuloides and Salix) in the intermediate sites, to black spruce (Picea mariana) forest in the oldest site. Soil organic matter accumulated 2.8-fold over time. Potential mineralization was highest in the intermediate-aged sites, as was nitrification and standing pools of inorganic nitrogen. In contrast, inorganic phosphorus pools were highest immediately following fire, and then decreased nine-fold with age. As measured with BiologTM plates, bacterial diversity and abundance were greatest in the oldest sites. Plant roots in the intermediate-aged sites displayed higher colonization by ecto- and arbuscular mycorrhizal fungi than those in the youngest and oldest sites. Likewise, glomalin, a glycoprotein produced by arbuscular mycorrhizal fungi, was most abundant in the 14-yr old site. Glomalin is believed to contribute to the formation of water-stable aggregates in the soil. However, water stable aggregates were most abundant in the younger sites and did not follow the pattern of glomalin or arbuscular mycorrhizal abundance. Our results indicate that fire may maintain landscape-level diversity of microbial functional groups, and that carbon sequestration in microbial tissues (e.g. glomalin and fungal biomass) may be greatest in areas that have burned several decades earlier. Changes in soil structure may not be directly attributable to

  10. Increasing fire severity, alternate successional trajectories, and the carbon balance of Alaskan boreal forests

    Science.gov (United States)

    Mack, M. C.; Alexander, H. D.; Jean, M.; Melvin, A. M.; Johnstone, J. F.

    2016-12-01

    Climate-sensitive disturbances, such as wildfire, can feed back positively to climate warming via the carbon (C) cycle if C released by disturbance is not replaced over post-fire succession. In boreal forests, burning of carbon in deep organic soils is not only an important determinate of ecosystem element balance over the disturbance cycle, but also sets the conditions that control plant recruitment, species dominance and successional trajectory. Species dominance, in turn, has the potential to exert strong control over the plant-soil-microbial feedbacks that determine C and nutrient coupling, C storage, and ultimately, replacement of combusted C. We examined the consequences of increasing fire severity for C balance and C and nitrogen (N) coupling in Alaskan boreal forests. We estimated combustion losses in 90 black spruce (conifer) stands that burned in 2004. Over the next decade, we followed natural tree seedling establishment in these stands and used seedling species dominance identify conifer versus deciduous successional trajectories. We assembled data from 120 stands that varied in time after fire and successional trajectory, and estimated C and N dynamics across 150 years of post-fire succession for each trajectory. Conifer stands that burned with high severity transitioned to deciduous tree dominance after fire. These stands had smaller ecosystem pools of C and N before fire, lost a larger proportion of these pools during the fire, and began succession with smaller residual pools than stands that returned to conifer dominance after fire. Over secondary succession, deciduous stands accumulated about 10 times more carbon in aboveground biomass than conifer stands. Belowground biomass and soil carbon accumulation, by contrast, was about three times higher in the black spruce stands than in deciduous stands. As a result, net ecosystem C accumulation over the 100 year inter-fire interval was three times higher in deciduous stands than in coniferous stands

  11. Deciduous birch canopy as unexpected contributor to stand level atmospheric reactivity in boreal forests

    Science.gov (United States)

    Bäck, Jaana; Taipale, Ditte; Aalto, Juho

    2017-04-01

    In boreal forests, deciduous trees such as birches may in future climate become more abundant due to their large biomass production capacity, relatively good resource use ability and large acclimation potential to elevated CO2 levels and warmer climate. Increase in birch abundance may lead to unpredicted consequences in atmospheric composition. Currently it is acknowledged that conifers such as Scots pine and Norway spruce are important sources for volatile organic compounds (VOCs), especially monoterpenes, throughout the year, although the strong temperature relationships implies that emissions are highest in summertime. However, the dynamics of the deciduous birch foliage VOC emissions and their relationship with environmental drivers during the development, maturation and senescence of foliage has not been well analyzed. Long-term measurements of birch, which are unfortunately very sparse, can provide very useful information for the development of biosphere-atmosphere models that simulate boreal and subarctic forested areas where birch is often a sub-canopy species, occurs as a mixture among conifers or forms even pure stands in the higher latitudes. We measured the branch level VOC emissions from a mature Silver birch with proton transfer reaction mass spectrometer during 2014 and 2015 at the SMEAR II station (Station for Measuring Ecosystem-Atmosphere Relations), southern Finland. Our results showed that the Silver birch foliage is a huge source for both short-chained volatiles such as methanol, acetaldehyde and acetone, as well as for monoterpenes. The mean emission rates from birch leaves were 5 to 10 times higher than the corresponding emissions from Scots pine shoots. We compared several semi-empirical model approaches for determining the birch foliage monoterpene standardized emission potentials, and utilized the continuous emission measurements from the two growing seasons for development of a novel algorithm which accounts for the leaf development and

  12. Determination of the biogenic secondary organic aerosol fraction in the boreal forest by NMR spectroscopy

    Directory of Open Access Journals (Sweden)

    E. Finessi

    2012-01-01

    Full Text Available The study investigates the sources of fine organic aerosol (OA in the boreal forest, based on measurements including both filter sampling (PM1 and online methods and carried out during a one-month campaign held in Hyytiälä, Finland, in spring 2007. Two aerosol mass spectrometers (Q-AMS, ToF-AMS were employed to measure on-line concentrations of major non-refractory aerosol species, while the water extracts of the filter samples were analyzed by nuclear magnetic resonance (NMR spectroscopy for organic functional group characterization of the polar organic fraction of the aerosol. AMS and NMR spectra were processed separately by non-negative factorization algorithms, in order to apportion the main components underlying the submicrometer organic aerosol composition and depict them in terms of both mass fragmentation patterns and functional group compositions.

    The NMR results supported the AMS speciation of oxidized organic aerosol (OOA into two main fractions, which could be generally labelled as more and less oxidized organics. The more oxidized component was characterized by a mass spectrum dominated by the m/z 44 peak, and in parallel by a NMR spectrum showing aromatic and aliphatic backbones highly substituted with oxygenated functional groups (carbonyls/carboxyls and hydroxyls. Such component, contributing on average 50% of the OA mass throughout the observing period, was associated with pollution outbreaks from the Central Europe. The less oxidized component was enhanced in concomitance with air masses originating from the North-to-West sector, in agreement with previous investigations conducted at this site. NMR factor analysis was able to separate two distinct components under the less oxidized fraction of OA. One of these NMR-factors was associated with the formation of terrestrial biogenic secondary organic aerosol (BSOA, based on the comparison with spectral profiles obtained from laboratory experiments of

  13. 3D simulation of boreal forests: structure and dynamics in complex terrain and in a changing climate

    Science.gov (United States)

    Brazhnik, Ksenia; Shugart, Herman H.

    2015-10-01

    To understand how the Siberian boreal forests may respond to near-future climate change, we employed a modeling approach and examined thresholds for significant and irreversible changes in forest structure and composition that are likely to be reached by mid-21st century. We applied the new spatially-explicit gap-dynamics model SIBBORK toward the understanding of how transition zones, namely treelines, which are notoriously undersampled and difficult to model, may change in the near future. We found that a 2 °C change in annual average air temperature significantly altered the structure, composition, and productivity of boreal forests stands both in the northern and the southern treeline ecotones. Treeline migration occurs at smaller temperature changes. Based on the current (1990-2014) observed warming trends, a 2 °C increase in annual average temperature compared to historical climate (1961-1990) is likely to be experienced at the northern treeline by 2040 and at the southern treeline by 2050. With regards to the forest biome, the most significant warming to date has been predicted and observed in Siberia. A 2 °C increase in annual average temperature compared to the second half of the 19th century is smaller than the predictions of even the most conservative RCP2.6 climate change scenario (IPCC 2013), and has previously been assumed to not likely result in dramatic changes to ecosystems or biome shifts. We show that at a +2 °C change, biome shifts from forest to steppe are likely to occur across a large area in southern Siberia. These changes in land cover will inevitably result in changes in the biodiversity, carbon storage, and the ecosystem services provided by the boreal forests of southern Siberia.

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

    Science.gov (United States)

    Thom, Dominik; Seidl, Rupert

    2016-08-01

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

  15. Ten-year responses of ground-dwelling spiders to retention harvest in the boreal forest.

    Science.gov (United States)

    Pinzon, Jaime; Spence, John R; Langor, David W; Shorthouse, David P

    2016-12-01

    The Ecosystem Management Emulating Natural Disturbances (EMEND) project tests the hypothesis that varying levels of green tree retention maintain and retain forest biodiversity better than conventional clear-cutting. We studied epigaeic spiders to assess biodiversity changes 2, 5, and 10 yr following a range of partial retention harvests (clear-cut, 10-75% retention) and unharvested controls in four boreal mixedwood cover types. A total of 56 371 adult spiders representing 220 species was collected using pitfall traps. Lasting effects on forest structure were proportional to harvest intensity. These changes strongly influenced spider richness, abundance, and species composition, as well as assemblage recovery. Distinctive assemblages were associated with disturbance level, especially with partial harvests (≤50% retention), and these were dominated by open-habitat species even 10 yr after harvest. Assemblages were more similar to those of controls in the highest (75%) retention treatment, but significant recovery toward the structure of pre-disturbance assemblages was not detected for any prescription in any cover type. Although early responses to retention harvest suggested positive effects on spider assemblages, these are better explained as lag effects after harvest because assemblages were less similar to those of unharvested controls 5 yr post-harvest, and only minor recovery was observed 10 yr following harvest. Retention of forest biodiversity decreased over time, especially in conifer stands and the lower (10-50%) retention treatments. Overall, retention harvests retained biodiversity and promoted landscape heterogeneity somewhat better than clear-cutting; however, there was a clear gradient of response and no retention "threshold" for conservation can be recommended on the basis of our data. Furthermore, results suggest that retention harvest prescriptions should be adjusted for cover type. We show that low retention ameliorated impacts in broadleaved

  16. Impacts of Climate and Insect Defoliators on Trembling Aspen (Populus tremuloides) Mortality and Productivity in Alaskan Boreal Forests

    Science.gov (United States)

    Boyd, M. A.; Goetz, S. J.; Rogers, B. M.; Walker, X. J.; Mack, M. C.

    2016-12-01

    Unprecedented rates of climate change have increased tree mortality and growth decline in forested ecosystems worldwide. The boreal forest has experienced a temperature increase of approximately 1.5 º C since 1970, a trend which is expected to continue. In response to the warming and drying of the boreal forest trembling aspen (Populus tremuloides) has experienced recent large-scale die-back. Although die-back is thought to be primarily a result of direct climate changes, insect infestation is another possible driver of aspen mortality and may interact strongly with recent climate. Throughout interior Alaska widespread and consistent foliar damage by the aspen epidermal leaf miner Phyllocnistis populiella has been observed concurrent with some of the warmest and driest growing seasons on record. Here we use tree ring width measurements, tree ring stable carbon isotope signatures, and forest inventory data to study the influence of leaf miner and climate on aspen mortality and productivity decline in the Alaskan boreal forest. In the summer of 2016 we sampled eight Cooperative Alaska Forest Inventory (CAFI) sites established by the US Forest Service in 1994. Since establishment tree status and infestation were recorded every 5 years. Each sampled site was aspen dominated and mortality ranged from 3.5% to 8% within a 5-year sampling period. We collected a total of 24 aspen tree cores and disks from each site: 12 from dead trees and 12 from live trees. In order to assess the influence of leaf miner on radial growth and tree ring stable carbon isotope ratios, cores were also collected from aspen stands surrounding Fairbanks where the size and severity of leaf miner infestation has been recorded since 2003. We expect that prior to mortality trees will show a decline in growth that is correlated to moisture stress and leaf miner infestation. We also expect to see an enriched carbon isotope signal as a result of infestation that will be decoupled from moisture, the

  17. Isotopic composition of carbon dioxide from a boreal forest fire: Inferring carbon loss from measurements and modeling

    OpenAIRE

    Schuur, Edward A. G; Trumbore, Susan E; Mack, Michelle C; Harden, Jennifer W

    2003-01-01

    [1] Fire is an important pathway for carbon (C) loss from boreal forest ecosystems and has a strong effect on ecosystem C balance. Fires can range widely in severity, defined as the amount of vegetation and forest floor consumed by fire, depending on local fuel and climatic conditions. Here we explore a novel method for estimating fire severity and loss of C from fire using the atmosphere to integrate ecosystem heterogeneity at the watershed scale. We measured the delta(13)C and Delta(14)C is...

  18. 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.

  19. 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.

  20. Bacterial Communities in Boreal Forest Mushrooms Are Shaped Both by Soil Parameters and Host Identity

    Science.gov (United States)

    Pent, Mari; Põldmaa, Kadri; Bahram, Mohammad

    2017-01-01

    Despite recent advances in understanding the microbiome of eukaryotes, little is known about microbial communities in fungi. Here we investigate the structure of bacterial communities in mushrooms, including common edible ones, with respect to biotic and abiotic factors in the boreal forest. Using a combination of culture-based and Illumina high-throughput sequencing, we characterized the bacterial communities in fruitbodies of fungi from eight genera spanning four orders of the class Agaricomycetes (Basidiomycota). Our results revealed that soil pH followed by fungal identity are the main determinants of the structure of bacterial communities in mushrooms. While almost half of fruitbody bacteria were also detected from soil, the abundance of several bacterial taxa differed considerably between the two environments. The effect of host identity was significant at the fungal genus and order level and could to some extent be ascribed to the distinct bacterial community of the chanterelle, representing Cantharellales—the earliest diverged group of mushroom-forming basidiomycetes. These data suggest that besides the substantial contribution of soil as a major taxa source of bacterial communities in mushrooms, the structure of these communities is also affected by the identity of the host. Thus, bacteria inhabiting fungal fruitbodies may be non-randomly selected from environment based on their symbiotic functions and/or habitat requirements. PMID:28539921

  1. Effect of regional climate warming on the phenology of butterflies in boreal forests in Manitoba, Canada.

    Science.gov (United States)

    Westwood, A R; Blair, D

    2010-08-01

    We examined the effect of regional climate warming on the phenology of butterfly species in boreal forest ecosystems in Manitoba, Canada. For the period 1971-2004, the mean monthly temperatures in January, September, and December increased significantly, as did the mean temperatures for several concurrent monthly periods. The mean annual temperature increased ≈ 0.05°C/yr over the study period. The annual number of frost-free days and degree-day accumulations increased as well. We measured the response of 19 common butterfly species to these temperature changes with the date of first appearance, week of peak abundance, and the length of flight period over the 33-yr period of 1972-2004. Although adult butterfly response was variable for spring and summer months, 13 of 19 species showed a significant (P butterfly species significantly affected by the warming trend. The early autumn and winter months warmed significantly, and butterflies seem to be responding to this warming trend with a change in the length of certain life stages. Two species, Junonia coenia and Euphydryas phaeton, increased their northerly ranges by ≈ 150 and 70 km, respectively. Warmer autumns and winters may be providing opportunities for range extensions of more southerly butterfly species held at bay by past climatic conditions.

  2. Climate change and bird reproduction: warmer springs benefit breeding success in boreal forest grouse.

    Science.gov (United States)

    Wegge, Per; Rolstad, Jørund

    2017-11-15

    Global warming is predicted to adversely affect the reproduction of birds, especially in northern latitudes. A recent study in Finland inferred that declining populations of black grouse, Tetrao tetrix, could be attributed to advancement of the time of mating and chicks hatching too early-supporting the mismatch hypothesis. Here, we examine the breeding success of sympatric capercaillie, T. urogallus, and black grouse over a 38-year period in southeast Norway. Breeding season temperatures increased, being most pronounced in April. Although the onset of spring advanced nearly three weeks, the peak of mating advanced only 4-5 days. In contrast to the result of the Finnish study, breeding success increased markedly in both species (capercaillie: 62%, black grouse: 38%). Both brood frequency and brood size increased during the study period, but significantly so only for brood frequency in capercaillie. Whereas the frequency of capercaillie broods was positively affected by rising temperatures, especially during the pre-hatching period, this was not the case in black grouse. Brood size, on the other hand, increased with increasing post-hatching temperatures in both species. Contrary to the prediction that global warming will adversely affect reproduction in boreal forest grouse, our study shows that breeding success was enhanced in warmer springs. © 2017 The Authors.

  3. Different regional climatic drivers of Holocene large wildfires in boreal forests of northeastern America

    Science.gov (United States)

    Remy, Cécile C.; Hély, Christelle; Blarquez, Olivier; Magnan, Gabriel; Bergeron, Yves; Lavoie, Martin; Ali, Adam A.

    2017-03-01

    Global warming could increase climatic instability and large wildfire activity in circumboreal regions, potentially impairing both ecosystem functioning and human health. However, links between large wildfire events and climatic and/or meteorological conditions are still poorly understood, partly because few studies have covered a wide range of past climate-fire interactions. We compared palaeofire and simulated climatic data over the last 7000 years to assess causes of large wildfire events in three coniferous boreal forest regions in north-eastern Canada. These regions span an east-west cline, from a hilly region influenced by the Atlantic Ocean currently dominated by Picea mariana and Abies balsamea to a flatter continental region dominated by Picea mariana and Pinus banksiana. The largest wildfires occurred across the entire study zone between 3000 and 1000 cal. BP. In western and central continental regions these events were triggered by increases in both the fire-season length and summer/spring temperatures, while in the eastern region close to the ocean they were likely responses to hydrological (precipitation/evapotranspiration) variability. The impact of climatic drivers on fire size varied spatially across the study zone, confirming that regional climate dynamics could modulate effects of global climate change on wildfire regimes.

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

    Science.gov (United States)

    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.

  5. Use of Radarsat-2 Polarimetric SAR Images for Fuel Moisture Mapping in Alaska Boreal Forests and South Africa Savannahs

    Science.gov (United States)

    Leblon, B.; Bourgeau-Chavez, L. L.; Kong, M.; Buckley, J. R.; Mathieu, R. M.; Charbonneau, F.; Gross, C. P.; Naidoo, L.

    2014-12-01

    The study reported a comparison between two Radarsat-2 polarimetric SAR (polSAR) images from extreme dry versus wet conditions are compared in an effort to determine the value of using polarimetric SAR data for estimating fuel moisture over South Africa savannahs and Alaska boreal forests. The savannahs study area is located into the Kruger National Park area and has 36 sites of lowveld savannas from bare overgrazed sites to medium-dense savannahs. The boreal forest study area has a chronosequence of black spruce ecosystems (recent burns, shrub-dominated regenerating forests , open canopied forests, moderately dense forest cover). Both study areas have a fairly level topography suitable for radar studies. The polSAR images were acquired using the same beam mode (FQ5 (23-25° incidence angle over the boreal sites, FQ15 (34.47-36.05° incidence angle) over the savannahs sites). Over each study area, soil moisture and vegetation structural data were measured in situ concurrently to the acquisition of the SAR imagery. The polSAR images were filtered for speckle noise using a Lee sigma filter and several polarimetric products were computed, such as those directly derived from the images (single linear and polairzed backscatters, polarimetric discriminators) and from target decompositions (Freeman-Durden, new van Zyl, Cloude-Pottier). Because most of these variables have a different unit, a normalized difference (in %) for each variable was calculated using the median values of the dry and wet dates for easier comparison of variable changes between the dates. Over both study areas, the normalized difference between wet and dry conditions was lower when higher tree canopy occurs. Results show utility of C-HH and C-RR polarized backscatters. Several polarimetric discriminators (dmin, Pr max, Pr min, Smax, Smin) were also significantly affected by the soil wetness. The Freeman Durden and van Zyl decomposition parameters outperformed the Cloude-Pottier decomposition

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

    Directory of Open Access Journals (Sweden)

    J. Williams

    2011-10-01

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

  7. Mixotrophy in Pyroleae (Ericaceae) from Estonian boreal forests does not vary with light or tissue age.

    Science.gov (United States)

    Lallemand, Félix; Puttsepp, Ülle; Lang, Mait; Luud, Aarne; Courty, Pierre-Emmanuel; Palancade, Cécile; Selosse, Marc-André

    2017-09-01

    In temperate forests, some green plants, namely pyroloids (Pyroleae, Ericaceae) and some orchids, independently evolved a mode of nutrition mixing photosynthates and carbon gained from their mycorrhizal fungi (mixotrophy). Fungal carbon is more enriched in 13C than photosynthates, allowing estimation of the proportion of carbon acquired heterotrophically from fungi in plant biomass. Based on 13C enrichment, mixotrophic orchids have previously been shown to increase shoot autotrophy level over the growth season and with environmental light availability. But little is known about the plasticity of use of photosynthetic versus fungal carbon in pyroloids. Plasticity of mixotrophy with leaf age or light level (estimated from canopy openness) was investigated in pyroloids from three Estonian boreal forests. Bulk leaf 13C enrichment of five pyroloid species was compared with that of control autotrophic plants along temporal series (over one growth season) and environmental light gradients (n=405 samples). Mixotrophic 13C enrichment was detected at studied sites for Pyrola chlorantha and Orthilia secunda (except at one site for the latter), but not for Chimaphila umbellata, Pyrola rotundifolia and Moneses uniflora. Enrichment with 13C did not vary over the growth season or between leaves from current and previous years. Finally, although one co-occurring mixotrophic orchid showed 13C depletion with increasing light availability, as expected for mixotrophs, all pyroloids responded identically to autotrophic control plants along light gradients. A phylogenetic trend previously observed is further supported: mixotrophy is rarely supported by 13C enrichment in the Chimaphila + Moneses clade, whereas it is frequent in the Pyrola + Orthilia clade. Moreover, pyroloid mixotrophy does not respond plastically to ageing or to light level. This contrasts with the usual view of a convergent evolution with orchids, and casts doubt on the way pyroloids use the carbon gained from their

  8. Seasonal Effects of Habitat on Sources and Rates of Snowshoe Hare Predation in Alaskan Boreal Forests.

    Directory of Open Access Journals (Sweden)

    Dashiell Feierabend

    greater influence on the sources of predation than the amount of cover in any given location within a habitat. Our observations illustrate the vulnerability of hares to predators in even the densest coniferous habitat available in the boreal forest, and indicate strong seasonal changes in the rates and sources of predation.

  9. Seasonal Effects of Habitat on Sources and Rates of Snowshoe Hare Predation in Alaskan Boreal Forests.

    Science.gov (United States)

    Feierabend, Dashiell; Kielland, Knut

    2015-01-01

    influence on the sources of predation than the amount of cover in any given location within a habitat. Our observations illustrate the vulnerability of hares to predators in even the densest coniferous habitat available in the boreal forest, and indicate strong seasonal changes in the rates and sources of predation.

  10. Occurrence and abundance of fungus-dwelling beetles (Ciidae in boreal forests and clearcuts: habitat associations at two spatial scales

    Directory of Open Access Journals (Sweden)

    Komonen, A.

    2005-12-01

    Full Text Available Insect material (> 30,000 individuals reared from the fruiting bodies of wood-decaying Trametes fungi was compared between old-growth boreal forests and adjacent clearcuts in Finland. Sulcacis affinis and Cis hispidus occurred more frequently and were, on average, more abundant in the clearcuts. Interestingly, Octotemnus glabriculus and Cis boleti had a slightly higher frequency of occurrence in the forests, despite lower resource availability. The former also showed a higher average abundance. On average, the cluster size of Trametes fruiting bodies occurring on woody debris was higher in the clearcuts than in the forests and had a positive effect on species occurrence and abundance in these clusters. The independent effect of the macrohabitat (forest or clearcut underscores the importance of the macrohabitat where specific resources occur, and this may override the positive effects of resource availability.

  11. Biomass Retrieval Using Multibaseline PolInSAR Data of a Boreal Forest at L-Band

    Science.gov (United States)

    Yang, Xinwei; Liao, Mingsheng; Tebaldini, Stefano; Zhang, Lu

    2016-08-01

    Forest height plays an important role in characterizing forest stand parameters, which can be related to above ground biomass (AGB) through allometric relations. In this work, the forest height and biomass parameters estimation performance using PolInSAR technique is evaluated on real airborne L-band SAR data acquired by E-SAR sensor in multibaseline configuration over Krycklan test site. The inversion method will be enhanced by considering the impact of decorrelation sources such as slope variation. The main purposes of our work are to propose improved multibaseline PolInSAR height inversion approach and establish revised model when evaluating AGB over boreal forest by using PolInSAR height results. Finally, the validity of the proposed methods will be analyzed.

  12. A boreal invasion in response to climate change? Range shifts and community effects in the borderland between forest and tundra.

    Science.gov (United States)

    Elmhagen, Bodil; Kindberg, Jonas; Hellström, Peter; Angerbjörn, Anders

    2015-01-01

    It has been hypothesized that climate warming will allow southern species to advance north and invade northern ecosystems. We review the changes in the Swedish mammal and bird community in boreal forest and alpine tundra since the nineteenth century, as well as suggested drivers of change. Observed changes include (1) range expansion and increased abundance in southern birds, ungulates, and carnivores; (2) range contraction and decline in northern birds and carnivores; and (3) abundance decline or periodically disrupted dynamics in cyclic populations of small and medium-sized mammals and birds. The first warm spell, 1930-1960, stands out as a period of substantial faunal change. However, in addition to climate warming, suggested drivers of change include land use and other anthropogenic factors. We hypothesize all these drivers interacted, primarily favoring southern generalists. Future research should aim to distinguish between effects of climate and land-use change in boreal and tundra ecosystems.

  13. Potential for Monitoring Snow Cover in Boreal Forests by Combining MODIS Snow Cover and AMSR-E SWE Maps

    Science.gov (United States)

    Riggs, George A.; Hall, Dorothy K.; Foster, James L.

    2009-01-01

    Monitoring of snow cover extent and snow water equivalent (SWE) in boreal forests is important for determining the amount of potential runoff and beginning date of snowmelt. The great expanse of the boreal forest necessitates the use of satellite measurements to monitor snow cover. Snow cover in the boreal forest can be mapped with either the Moderate Resolution Imaging Spectroradiometer (MODIS) or the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) microwave instrument. The extent of snow cover is estimated from the MODIS data and SWE is estimated from the AMSR-E. Environmental limitations affect both sensors in different ways to limit their ability to detect snow in some situations. Forest density, snow wetness, and snow depth are factors that limit the effectiveness of both sensors for snow detection. Cloud cover is a significant hindrance to monitoring snow cover extent Using MODIS but is not a hindrance to the use of the AMSR-E. These limitations could be mitigated by combining MODIS and AMSR-E data to allow for improved interpretation of snow cover extent and SWE on a daily basis and provide temporal continuity of snow mapping across the boreal forest regions in Canada. The purpose of this study is to investigate if temporal monitoring of snow cover using a combination of MODIS and AMSR-E data could yield a better interpretation of changing snow cover conditions. The MODIS snow mapping algorithm is based on snow detection using the Normalized Difference Snow Index (NDSI) and the Normalized Difference Vegetation Index (NDVI) to enhance snow detection in dense vegetation. (Other spectral threshold tests are also used to map snow using MODIS.) Snow cover under a forest canopy may have an effect on the NDVI thus we use the NDVI in snow detection. A MODIS snow fraction product is also generated but not used in this study. In this study the NDSI and NDVI components of the snow mapping algorithm were calculated and analyzed to determine how they changed

  14. Combining satellite lidar, airborne lidar, and ground plots to estimate the amount and distribution of aboveground biomass in the boreal forest of North America 1

    Science.gov (United States)

    Hank A. Margolis; Ross F. Nelson; Paul M. Montesano; André Beaudoin; Guoqing Sun; Hans-Erik Andersen; Michael A. Wulder

    2015-01-01

    We report estimates of the amount, distribution, and uncertainty of aboveground biomass (AGB) of the different ecoregions and forest land cover classes within the North American boreal forest, analyze the factors driving the error estimates, and compare our estimates with other reported values. A three-phase sampling strategy was used (i) to tie ground plot AGB to...

  15. Merging IceSAT GLAS and Terra MODIS Data in Order to Derive Forest Type Specific Tree Heights in the Central Siberian Boreal Forest

    Science.gov (United States)

    Ranson, K. Jon; Sun, Guoqing; Kimes, Daniel; Kovacs, Katalin; Kharuk, Viatscheslav

    2006-01-01

    Mapping of boreal forest's type, biomass, and other structural parameters are critical for understanding of the boreal forest's significance in the carbon cycle, its response to and impact on global climate change. We believe the nature of the forest structure information available from MISR and GLAS can be used to help identify forest type, age class, and estimate above ground biomass levels beyond that now possible with MODIS alone. The ground measurements will be used to develop relationships between remote sensing observables and forest characteristics and provide new information for understanding forest changes with respect to environmental change. Lidar is a laser altimeter that determines the distance from the instrument to the physical surface by measuring the time elapsed between the pulse emission and the reflected return. Other studies have shown that the returned signal may identify multiple returns originating from trees, building and other objects and permits the calculation of their height. Studies using field data have shown that lidar data can provide estimates of structural parameters such as biomass, stand volume and leaf area index and allows remarkable differentiation between primary and secondary forest. NASA's IceSAT Geoscience Laser Altimeter System (GLAS) was launched in January 2003 and collected data during February and September of that year. This study used data acquired over our study sites in central Siberia to examine the GLAS signal as a source of forest height and other structural characteristics. The purpose of our Siberia project is to improve forest cover maps and produce above-ground biomass maps of the boreal forest in Northern Eurasia from MODIS by incorporating structural information inherent in the Terra MISR and ICESAT Geoscience Laser Altimeter System (GLAS) instruments. A number of forest cover classifications exist for the boreal forest. We believe the limiting factor in these products is the lack of structural

  16. Differentiation of tundra/taiga and boreal coniferous forest wolves: genetics, coat colour and association with migratory caribou.

    Science.gov (United States)

    Musiani, Marco; Leonard, Jennifer A; Cluff, H Dean; Gates, C Cormack; Mariani, Stefano; Paquet, Paul C; Vilà, Carles; Wayne, Robert K

    2007-10-01

    The grey wolf has one of the largest historic distributions of any terrestrial mammal and can disperse over great distances across imposing topographic barriers. As a result, geographical distance and physical obstacles to dispersal may not be consequential factors in the evolutionary divergence of wolf populations. However, recent studies suggest ecological features can constrain gene flow. We tested whether wolf-prey associations in uninterrupted tundra and forested regions of Canada explained differences in migratory behaviour, genetics, and coat colour of wolves. Satellite-telemetry data demonstrated that tundra wolves (n = 19) migrate annually with caribou (n = 19) from denning areas in the tundra to wintering areas south of the treeline. In contrast, nearby boreal coniferous forest wolves are territorial and associated year round with resident prey. Spatially explicit analysis of 14 autosomal microsatellite loci (n = 404 individuals) found two genetic clusters corresponding to tundra vs. boreal coniferous forest wolves. A sex bias in gene flow was inferred based on higher levels of mtDNA divergence (F(ST) = 0.282, 0.028 and 0.033; P wolves from tundra populations exhibited light colouration whereas only 38% of boreal coniferous forest wolves did (chi(2) = 64.52, P < 0.0001). The sharp boundary representing this discontinuity was the southern limit of the caribou migration. These findings show that substantial genetic and phenotypic differentiation in highly mobile mammals can be caused by prey-habitat specialization rather than distance or topographic barriers. The presence of a distinct wolf ecotype in the tundra of North America highlights the need to preserve migratory populations.

  17. Spectral Similarity and PRI Variations for a Boreal Forest Stand Using Multi-angular Airborne Imagery

    Directory of Open Access Journals (Sweden)

    Vincent Markiet

    2017-09-01

    Full Text Available The photochemical reflectance index (PRI is a proxy for light use efficiency (LUE, and is used in remote sensing to measure plant stress and photosynthetic downregulation in plant canopies. It is known to depend on local light conditions within a canopy indicating non-photosynthetic quenching of incident radiation. Additionally, when measured from a distance, canopy PRI depends on shadow fraction—the fraction of shaded foliage in the instantaneous field of view of the sensor—due to observation geometry. Our aim is to quantify the extent to which sunlit fraction alone can describe variations in PRI so that it would be possible to correct for its variation and identify other possible factors affecting the PRI–sunlit fraction relationship. We used a high spatial and spectral resolution Aisa Eagle airborne imaging spectrometer above a boreal Scots pine site in Finland (Hyytiälä forest research station, 61°50′N, 24°17′E, with the sensor looking in nadir and tilted (off-nadir directions. The spectral resolution of the data was 4.6 nm, and the spatial resolution was 0.6 m. We compared the PRI for three different scatter angles ( β = 19 ° , 55 ° and 76 °, defined as the angle between sensor and solar directions at the forest stand level, and observed a small (0.006 but statistically significant (p < 0.01 difference in stand PRI. We found that stand mean PRI was not a direct function of sunlit fraction. However, for each scatter angle separately, we found a clear non-linear relationship between PRI and sunlit fraction. The relationship was systematic and had a similar shape for all of the scatter angles. As the PRI–sunlit fraction curves for the different scatter angles were shifted with respect to each other, no universal curve could be found causing the observed independence of canopy PRI from the average sunlit fraction of each view direction. We found the shifts of the curves to be related to a leaf structural effect on canopy

  18. Validation of MODIS and GEOV1 fPAR Products in a Boreal Forest Site in Finland

    Directory of Open Access Journals (Sweden)

    Titta Majasalmi

    2015-01-01

    Full Text Available Remote sensing of the fraction of absorbed Photosynthetically Active Radiation (fPAR has become a timely option to monitor forest productivity. However, only a few studies have had ground reference fPAR datasets containing both forest canopy and understory fPAR from boreal forests for the validation of satellite products. The aim of this paper was to assess the performance of two currently available satellite-based fPAR products: MODIS fPAR (MOD15A2, C5 and GEOV1 fPAR (g2_BIOPAR_FAPAR, as well as an NDVI-fPAR relationship applied to the MODIS surface reflectance product and a Landsat 8 image, in a boreal forest site in Finland. Our study area covered 16 km2 and field data were collected from 307 forest plots. For all plots, we obtained both forest canopy fPAR and understory fPAR. The ground reference total fPAR agreed better with GEOV1 fPAR than with MODIS fPAR, which showed much more temporal variation during the peak-season than GEOV1 fPAR. At the chosen intercomparison date in peak growing season, MODIS NDVI based fPAR estimates were similar to GEOV1 fPAR, and produced on average 0.01 fPAR units smaller fPAR estimates than ground reference total fPAR. MODIS fPAR and Landsat 8 NDVI based fPAR estimates were similar to forest canopy fPAR.

  19. 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 (G s ), water- and light-use efficiency and surface-atmosphere coupling of European boreal coniferous forests was explored using eddy-covariance (EC) energy and CO 2 fluxes. The observed scaling relations were then explained using a biophysical multilayer soil-vegetation-atmosphere transfer model as well as by a bulk G s representation. The LAI variations significantly alter radiation regime, within-canopy microclimate, sink/source distributions of CO 2 , H 2 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 G s experienced a minimum in the LAI range 1-2 m 2 m -2 caused by opposing nonproportional response of stomatally controlled transpiration and 'free' forest floor evaporation to changes in canopy density. The young forests had strongest coupling with the atmosphere while stomatal control of energy partitioning was strongest in relatively sparse (LAI ~2 m 2 m -2 ) pine stands growing on mineral soils. The data analysis and model results suggest that LAI may be an effective scaling parameter for net radiation and its partitioning but only in sparse stands (LAI energy exchange. In denser forests, any LAI dependency varies with physiological traits such as light-saturated water-use efficiency. The results suggest that incorporating species traits and site conditions are necessary when LAI is used in upscaling energy exchanges of boreal coniferous forests. © 2016 John Wiley & Sons Ltd.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-01

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

  1. 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

  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. Nonlinearities, scale-dependence, and individualism of boreal forest trees to climate forcing

    Science.gov (United States)

    Wolken, J. M.; Mann, D. H.; Grant, T. A., III; Lloyd, A. H.; Hollingsworth, T. N.

    2013-12-01

    Our understanding of the climate-growth relationships of trees are complicated by the nonlinearity and variability of these responses through space and time. Furthermore, trees growing at the same site may exhibit opposing growth responses to climate, a phenomenon termed growth divergence. To date the majority of dendrochronological studies in Interior Alaska have involved white spruce growing at treeline, even though black spruce is the most abundant tree species. Although changing climate-growth relationships have been observed in black spruce, there is little known about the multivariate responses of individual trees to temperature and precipitation and whether or not black spruce exhibits growth divergences similar to those documented for white spruce. To evaluate the occurrence of growth divergences in black spruce, we collected cores from trees growing on a steep, north-facing toposequence having a gradient in environmental parameters. Our overall goal was to assess how the climate-growth relationships of black spruce change over space and time. Specifically, we evaluated how topography influences the climate-growth relationships of black spruce and if the growth responses to climate are homogeneous. At the site-level most trees responded negatively to temperature and positively to precipitation, while at the tree-level black spruce exhibited heterogenous growth responses to climate that varied in both space (i.e., between sites) and time (i.e., seasonally and annually). There was a dominant response-type at each site, but there was also considerable variability in the proportion of trees exhibiting each response-type combination. Even in a climatically extreme setting like Alaska's boreal forest, tree responses to climate variability are spatially and temporally complex, as well as highly nonlinear.

  4. Long-Term Satellite Detection of Post-Fire Vegetation Trends in Boreal Forests of China

    Directory of Open Access Journals (Sweden)

    Kunpeng Yi

    2013-12-01

    Full Text Available This paper describes the long-term effects on vegetation following the catastrophic fire in 1987 on the northern Great Xing’an Mountain by analyzing the AVHRR GIMMS 15-day composite normalized difference vegetation index (NDVI dataset. Both temporal and spatial characteristics were analyzed for natural regeneration and tree planting scenarios from 1984 to 2006. Regressing post-fire NDVI values on the pre-fire values helped identify the NDVI for burnt pixels in vegetation stands. Stand differences in fire damage were classified into five levels: Very High (VH, High (H, Moderate (M, Low (L and Slight (S. Furthermore, intra-annual and inter-annual post-fire vegetation recovery trajectories were analyzed by deriving a time series of NDVI and relative regrowth index (RRI values for the entire burned area. Finally, spatial pattern and trend analyses were conducted using the pixel-based post-fire annual stands regrowth index (SRI with a nonparametric Mann-Kendall (MK statistics method. The results show that October was a better period compared to other months for distinguishing the post- and pre-fire vegetation conditions using the NDVI signals in boreal forests of China because colored leaves on grasses and shrubs fall down, while the leaves on healthy trees remain green in October. The MK statistics method is robustly capable of detecting vegetation trends in a relatively long time series. Because tree planting primarily occurred in the severely burned area (approximately equal to the Medium, High and Very High fire damage areas following the Daxing’anling fire in 1987, the severely burned area exhibited a better recovery trend than the lightly burned regions. Reasonable tree planting can substantially quicken the recovery and shorten the restoration time of the target species. More detailed satellite analyses and field data will be required in the future for a more convincing validation of the results.

  5. Tethered balloon measurements of biogenic volatile organic compounds at a Boreal forest site

    Directory of Open Access Journals (Sweden)

    C. Spirig

    2004-01-01

    Full Text Available Measurements of biogenic volatile organic compounds (VOCs were performed at Hyytiälä, a Boreal forest site in Southern Finland as part of the OSOA (origin and formation of secondary organic aerosol project in August 2001. At this site, frequent formation of new particles has been observed and the role of biogenic VOCs in this process is still unclear. Tethered balloons served as platforms to collect VOC samples within the planetary boundary layer at heights up to 1.2 km above ground during daytime. Mean mixed layer concentrations of total monoterpenes varied between 10 and 170 pptv, with a-pinene, limonene and D3-carene as major compounds, isoprene was detected at levels of 2-35 pptv. A mixed layer gradient technique and a budget approach are applied to derive surface fluxes representative for areas of tens to hundreds of square kilometres. Effects of spatial heterogeneity in surface emissions are examined with a footprint analysis. Depending on the source area considered, mean afternoon emissions of the sum of terpenes range between 180 and 300 mg m-2 h-1 for the period of 2-12 August 2001. Surface fluxes close to Hyytiälä were higher than the regional average, and agree well with mean emissions predicted by a biogenic VOC emission model. Total rates of monoterpene oxidation were calculated with a photochemical model. The rates did not correlate with the occurrence of new particle formation, but the ozone pathway was of more importance on days with particle formation. Condensable vapour production from the oxidation of monoterpenes throughout the mixed layer can only account for a fraction of the increase in aerosol mass observed at the surface.

  6. 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

  7. 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

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

    Science.gov (United States)

    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. Dissolved organic carbon in Alaskan boreal forest: Sources, chemical characteristics, and biodegradability

    Science.gov (United States)

    Wickland, K.P.; Neff, J.C.; Aiken, G.R.

    2007-01-01

    The fate of terrestrially-derived dissolved organic carbon (DOC) is important to carbon (C) cycling in both terrestrial and aquatic environments, and recent evidence suggests that climate warming is influencing DOC dynamics in northern ecosystems. To understand what determines the fate of terrestrial DOC, it is essential to quantify the chemical nature and potential biodegradability of this DOC. We examined DOC chemical characteristics and biodegradability collected from soil pore waters and dominant vegetation species in four boreal black spruce forest sites in Alaska spanning a range of hydrologic regimes and permafrost extents (Well Drained, Moderately Well Drained, Poorly Drained, and Thermokarst Wetlands). DOC chemistry was characterized using fractionation, UV-Vis absorbance, and fluorescence measurements. Potential biodegradability was assessed by incubating the samples and measuring CO2 production over 1 month. Soil pore water DOC from all sites was dominated by hydrophobic acids and was highly aromatic, whereas the chemical composition of vegetation leachate DOC varied significantly with species. There was no seasonal variability in soil pore water DOC chemical characteristics or biodegradability; however, DOC collected from the Poorly Drained site was significantly less biodegradable than DOC from the other three sites (6% loss vs. 13-15% loss). The biodegradability of vegetation-derived DOC ranged from 10 to 90% loss, and was strongly correlated with hydrophilic DOC content. Vegetation such as Sphagnum moss and feathermosses yielded DOC that was quickly metabolized and respired. In contrast, the DOC leached from vegetation such as black spruce was moderately recalcitrant. Changes in DOC chemical characteristics that occurred during microbial metabolism of DOC were quantified using fractionation and fluorescence. The chemical characteristics and biodegradability of DOC in soil pore waters were most similar to the moderately recalcitrant vegetation

  10. NACP LiDAR-based Biomass Estimates, Boreal Forest Biome, North America, 2005-2006

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides estimates of aboveground biomass (AGB) for defined land cover types within World Wildlife Fund (WWF) ecoregions across the boreal biome of...

  11. LiDAR-based Biomass Estimates, Boreal Forest Biome, Eurasia, 2005-2006

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides estimates of aboveground biomass (AGB) for defined land cover types within World Wildlife Fund (WWF) ecoregions across the boreal biome of...

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

    Directory of Open Access Journals (Sweden)

    J. Kontkanen

    2016-10-01

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

  13. Thresholds for Boreal Biome Transitions

    NARCIS (Netherlands)

    Scheffer, M.; Hirota, M.; Holmgren, M.; Nes, van E.H.; Chapin, F.S.

    2012-01-01

    Although the boreal region is warming twice as fast as the global average, the way in which the vast boreal forests and tundras may respond is poorly understood. Using satellite data, we reveal marked alternative modes in the frequency distributions of boreal tree cover. At the northern end and at

  14. Effects of nitrogen fertilization on the understorey carbon balance over the growing season in a boreal Pine forest

    Science.gov (United States)

    Metcalfe, D. B.; Eisele, B.; Hasselquist, N. J.

    2013-08-01

    Boreal forests play a key role in the global carbon cycle and are facing rapid shifts in nitrogen availability with poorly understood consequences for ecosystem function and global climate. We quantified the effects of nitrogen availability on carbon fluxes from a relatively understudied component of these forests - understorey vegetation - at three intervals over the summer growing period in a northern Swedish Scots Pine stand. Nitrogen addition altered both photosynthetic carbon uptake and respiratory release, but the magnitude and direction of this effect depended on the time during the growing season and the amount of nitrogen added. Specifically, nitrogen addition stimulated net ecosystem carbon uptake only in the late growing season. We find evidence for species-specific control of understorey carbon sink strength, as photosynthesis per unit ground area was positively correlated only with the abundance of the vascular plant Vaccinium myrtillus and no others. Comparison of photosynthetic carbon uptake with data on plant carbon dioxide release from the study site, indicate that understorey vegetation photosynthate was mainly supplying respiratory demands for much of the year. Only in the late season with nitrogen addition did understorey vegetation appear to experience a large surplus of carbon in excess of respiratory requirements. Further work, simultaneously comparing all major biomass and respiratory carbon fluxes in understorey and tree vegetation, is required to resolve the likely impacts of environmental changes on whole-ecosystem carbon sequestration in boreal forests.

  15. 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.

  16. The positive net radiative greenhouse gas forcing of increasing methane emissions from a thawing boreal forest-wetland landscape.

    Science.gov (United States)

    Helbig, Manuel; Chasmer, Laura E; Kljun, NatasCha; Quinton, William L; Treat, Claire C; Sonnentag, Oliver

    2017-06-01

    At the southern margin of permafrost in North America, climate change causes widespread permafrost thaw. In boreal lowlands, thawing forested permafrost peat plateaus ('forest') lead to expansion of permafrost-free wetlands ('wetland'). Expanding wetland area with saturated and warmer organic soils is expected to increase landscape methane (CH4 ) emissions. Here, we quantify the thaw-induced increase in CH4 emissions for a boreal forest-wetland landscape in the southern Taiga Plains, Canada, and evaluate its impact on net radiative forcing relative to potential long-term net carbon dioxide (CO2 ) exchange. Using nested wetland and landscape eddy covariance net CH4 flux measurements in combination with flux footprint modeling, we find that landscape CH4 emissions increase with increasing wetland-to-forest ratio. Landscape CH4 emissions are most sensitive to this ratio during peak emission periods, when wetland soils are up to 10 °C warmer than forest soils. The cumulative growing season (May-October) wetland CH4 emission of ~13 g CH4  m-2 is the dominating contribution to the landscape CH4 emission of ~7 g CH4  m-2 . In contrast, forest contributions to landscape CH4 emissions appear to be negligible. The rapid wetland expansion of 0.26 ± 0.05% yr-1 in this region causes an estimated growing season increase of 0.034 ± 0.007 g CH4  m-2  yr-1 in landscape CH4 emissions. A long-term net CO2 uptake of >200 g CO2  m-2  yr-1 is required to offset the positive radiative forcing of increasing CH4 emissions until the end of the 21st century as indicated by an atmospheric CH4 and CO2 concentration model. However, long-term apparent carbon accumulation rates in similar boreal forest-wetland landscapes and eddy covariance landscape net CO2 flux measurements suggest a long-term net CO2 uptake between 49 and 157 g CO2  m-2  yr-1 . Thus, thaw-induced CH4 emission increases likely exert a positive net radiative greenhouse gas forcing through the 21st century.

  17. Influence of fungi on N and C dynamics during organic matter decomposition in boreal forests

    OpenAIRE

    Baskaran, Preetisri

    2017-01-01

    Soils in terrestrial ecosystems store more carbon (C) than plants and the atmosphere combined, and ecosystems’ C dynamics are strongly dependent of nitrogen (N) availability. Moreover, plant production in boreal ecosystems is often limited by low N availability, and N retention in soils is a major constraint on N recirculation to plants. Soil fungi strongly influence C and N interactions in boreal ecosystems. However, a better knowledge of their role in the C and N interactions and balances i...

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

    Science.gov (United States)

    Kimball, John; Kang, Sinkyu

    2003-01-01

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

  19. Greater carbon allocation to mycorrhizal fungi reduces tree nitrogen uptake in a boreal forest.

    Science.gov (United States)

    Hasselquist, Niles J; Metcalfe, Daniel B; Inselsbacher, Erich; Stangl, Zsofia; Oren, Ram; Näsholm, Torgny; Högberg, Peter

    2016-04-01

    The central role that ectomycorrhizal (EM) symbioses play in the structure and function of boreal forests pivots around the common assumption that carbon (C) and nitrogen (N) are exchanged at rates favorable for plant growth. However, this may not always be the case. It has been hypothesized that the benefits mycorrhizal fungi convey to their host plants strongly depends upon the availability of C and N, both of which are rapidly changing as a result of intensified human land use and climate change. Using large-scale shading and N addition treatments, we assessed the independent and interactive effects of changes in C and N supply on the transfer of N in intact EM associations with -15 yr. old Scots pine trees. To assess the dynamics of N transfer in EM symbioses, we added trace amounts of highly enriched 5NO3(-) label to the EM-dominated mor-layer and followed the fate of the 15N label in tree foliage, fungal chitin on EM root tips, and EM sporocarps. Despite no change in leaf biomass, shading resulted in reduced tree C uptake, ca. 40% lower fungal biomass on EM root tips, and greater 15N label in tree foliage compared to unshaded control plots, where more 15N label was found in fungal biomass on EM colonized root tips. Short-term addition of N shifted the incorporation of 15N label from EM fungi to tree foliage, despite no significant changes in below-ground tree C allocation to EM fungi. Contrary to the common assumption that C and N are exchanged at rates favorable for plant growth, our results show for the first time that under N-limited conditions greater C allocation to EM fungi in the field results in reduced, not increased, N transfer to host trees. Moreover, given the ubiquitous nature of mycorrhizal symbioses, our results stress the need to incorporate mycorrhizal dynamics into process-based ecosystem models to better predict forest C and N cycles in light of global climate change.

  20. 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

  1. 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

  2. The origin of soil organic matter controls its composition and bioreactivity across a mesic boreal forest latitudinal gradient.

    Science.gov (United States)

    Kohl, Lukas; Philben, Michael; Edwards, Kate A; Podrebarac, Frances A; Warren, Jamie; Ziegler, Susan E

    2018-02-01

    Warmer climates have been associated with reduced bioreactivity of soil organic matter (SOM) typically attributed to increased diagenesis; the combined biological and physiochemical transformation of SOM. In addition, cross-site studies have indicated that ecosystem regime shifts, associated with long-term climate warming, can affect SOM properties through changes in vegetation and plant litter production thereby altering the composition of soil inputs. The relative importance of these two controls, diagenesis and inputs, on SOM properties as ecosystems experience climate warming, however, remains poorly understood. To address this issue we characterized the elemental, chemical (nuclear magnetic resonance spectroscopy and total hydrolysable amino acids analysis), and isotopic composition of plant litter and SOM across a well-constrained mesic boreal forest latitudinal transect in Atlantic Canada. Results across forest sites within each of three climate regions indicated that (1) climate history and diagenesis affect distinct parameters of SOM chemistry, (2) increases in SOM bioreactivity with latitude were associated with elevated proportions of carbohydrates relative to plant waxes and lignin, and (3) despite the common forest type across regions, differences in SOM chemistry by climate region were associated with chemically distinct litter inputs and not different degrees of diagenesis. The observed climate effects on vascular plant litter chemistry, however, explained only part of the regional differences in SOM chemistry, most notably the higher protein content of SOM from warmer regions. Greater proportions of lignin and aliphatic compounds and smaller proportions of carbohydrates in warmer sites' soils were explained by the higher proportion of vascular plant relative to moss litter in the warmer relative to cooler forests. These results indicate that climate change induced decreases in the proportion of moss inputs not only impacts SOM chemistry but also

  3. LiDAR and WorldView-2 satellite data for Leaf Area Index estimation in the boreal forest

    Science.gov (United States)

    Pope, Graham Wesley

    Leaf Area Index (LAI) is an important input variable for forest ecosystem modeling as it is a factor in predicting productivity and biomass, two key aspects of forest health. Current in situ methods of determining LAI are sometimes destructive and generally very time consuming. Other LAI derivation methods, mainly satellite-based in nature, do not provide sufficient spatial resolution or the precision required by forest managers. This thesis focused on estimating LAI from: i) height and density metrics derived from Light Detection and Ranging (LiDAR); ii) spectral vegetation indices (SVIs), in particular the Normalized Difference Vegetation Index (NDVI); and iii) a combination of these two remote sensing technologies. In situ measurements of LAI were calculated from digital hemispherical photographs (DHPs) and remotely sensed variables were derived from low density LiDAR and high resolution WorldView-2 data. Multiple Linear Regression (MLR) models were created using these variables, allowing forest-wide prediction surfaces to be created. Results from these analyses demonstrated: i) moderate explanatory power (i.e., R2 = 0.54) for LiDAR models incorporating metrics that have proven to be related to canopy structure; ii) no relationship when using SVIs; and iii) no significant improvement of LiDAR models when combining them with SVI variables. The results suggest that LiDAR models in boreal forest environments provide satisfactory estimations of LAI, even with low ranges of LAI for model calibration. On the other hand, it was anticipated that traditional SVI relationships to LAI would be present with WorldView-2 data, a result that is not easily explained. Models derived from low point density LiDAR in a mixedwood boreal environment seem to offer a reliable method of estimating LAI at a high spatial resolution for decision makers in the forestry community.

  4. Direct and indirect climate change effects on carbon dioxide fluxes in a thawing boreal forest-wetland landscape.

    Science.gov (United States)

    Helbig, Manuel; Chasmer, Laura E; Desai, Ankur R; Kljun, Natascha; Quinton, William L; Sonnentag, Oliver

    2017-08-01

    In the sporadic permafrost zone of northwestern Canada, boreal forest carbon dioxide (CO2 ) fluxes will be altered directly by climate change through changing meteorological forcing and indirectly through changes in landscape functioning associated with thaw-induced collapse-scar bog ('wetland') expansion. However, their combined effect on landscape-scale net ecosystem CO2 exchange (NEELAND ), resulting from changing gross primary productivity (GPP) and ecosystem respiration (ER), remains unknown. Here, we quantify indirect land cover change impacts on NEELAND and direct climate change impacts on modeled temperature- and light-limited NEELAND of a boreal forest-wetland landscape. Using nested eddy covariance flux towers, we find both GPP and ER to be larger at the landscape compared to the wetland level. However, annual NEELAND (-20 g C m(-2) ) and wetland NEE (-24 g C m(-2) ) were similar, suggesting negligible wetland expansion effects on NEELAND . In contrast, we find non-negligible direct climate change impacts when modeling NEELAND using projected air temperature and incoming shortwave radiation. At the end of the 21st century, modeled GPP mainly increases in spring and fall due to reduced temperature limitation, but becomes more frequently light-limited in fall. In a warmer climate, ER increases year-round in the absence of moisture stress resulting in net CO2 uptake increases in the shoulder seasons and decreases during the summer. Annually, landscape net CO2 uptake is projected to decline by 25 ± 14 g C m(-2) for a moderate and 103 ± 38 g C m(-2) for a high warming scenario, potentially reversing recently observed positive net CO2 uptake trends across the boreal biome. Thus, even without moisture stress, net CO2 uptake of boreal forest-wetland landscapes may decline, and ultimately, these landscapes may turn into net CO2 sources under continued anthropogenic CO2 emissions. We conclude that NEELAND changes are more likely to be driven by

  5. Canadian forest service. Science and sustainable development directorate: Arnews: Annual report 1992. Information report No. 7

    Energy Technology Data Exchange (ETDEWEB)

    Van Sickle, J.P.; Hall, J.P.

    1993-01-01

    ARNEWS is a program managed by FIDS (Forest Insect and Disease Survey). It has been in place since 1984 to detect early signs of damage to Canadian forests. ARNEWS (Acid Rain National Early Warning System) is a long-term biomonitoring program designed to detect changes in forest vegetation and soils. ARNEWS consists of 103 permanent sample plots located in all 10 provinces. The health of 18 conifer and 9 hardwood species is described. This document presents methods used, the health of Canada's forests, discussion and conclusions.

  6. Application of a catchment characterization hydrologic model for exploring parameter sensitivities in a boreal forest, discontinuous permafrost ecosystem

    Science.gov (United States)

    Morton, D.; Bolton, W. R.; Young, J.; Hinzman, L. D.

    2013-12-01

    Many of the expected climate-driven changes in sub-arctic ecosystems, such as increased temperature and precipitation, decreased permafrost extent, tree-line expansion and vegetation composition, have been identified as potential mechanisms that may lead to shifts in the Arctic Ocean freshwater budget. Understanding the feedback mechanisms of the water cycle are paramount, in that small changes may result in dramatic threshold changes in the hydrology, ecology and surface energy balance. As part of a study on how vegetation water use and permafrost dynamics impact stream flow in the boreal forest discontinuous permafrost zone, we are integrating a vegetation water use model and a simple, first-order, non-linear hydrological model, utilizing a Bayesian analysis approach to fully account for and propagate uncertainty through this modeling system. With an overall goal of improving parameterizations of large-scale hydrological models, we are constructing a simple and portable hydrologic model within a Bayesian framework. Thus, uncertainty associated with the evaporation (E), transpiration (T), precipitation (P), and streamflow (Q) submodels will be propagated into the final hydrology model. An immediate application of the modeling system will be used to explore the hydrological impacts of different vegetation distributions found in the boreal forest. In this work, we describe the basic structure of this flexible, object-oriented model and test its performance against collected basin data from headwater catchments of varying permafrost extent and ecosystem structure (deciduous versus coniferous vegetation). We will also do analyses to assess model sensitivity to each parameter (E, T, P, Q) and to different climate scenarios. This model is a major advancement for hydrological models that will aid in assessing sources of uncertainty in boreal hydrological systems.

  7. The boreal ecosystem research and monitoring sites (BERMS) initiative : scientific accomplishments

    Energy Technology Data Exchange (ETDEWEB)

    McCaughey, J.H. [Queen' s Univ., Kingston, ON (Canada); Barr, A. [National Hydrology Research Centre, Meteorological Service of Canada, Saskatoon, SK (Canada); Black, T.A. [British Columbia Univ., Vancouver, BC (Canada); Goodison, B. [Meteorological Service of Canada, Downsview, ON (Canada); Hogg, E.H.; Amiro, B.; Price, D.T. [Canadian Forest Service, Northern Forestry Centre, Edmonton, AB (Canada); Stewart, R.B. [Canadian Forest Service, Ottawa, ON (Canada); Stolle, N. [Parks and Heritage Canada, Prince Albert National Park, Waskesiu Lake, SK (Canada); Chen, J. [Toronto Univ., ON (Canada); Gower, S.T. [Wisconsin Univ., Madison, WI (United States)

    2002-10-01

    Carbon, water and energy cycling in the Canadian boreal forest ecosystems is currently being studied in the Canadian research initiative called the Boreal Ecosystem Research and Monitoring Sites (BERMS) project. BERMS provides long-term, continuous climatological and flux data from target ecosystems in Canada. The data is used to determine the impact of certain parameters on carbon and energy exchange in a multi-year perspective. The role of inter-annual climate variation and site disturbance on forest-atmosphere interactions such as water and energy is also addressed along with carbon sequestration on a seasonal and annual basis. The BERMS database offers a test bed for developing and testing Land Surface Parameterization (LSP) schemes, particularly the Canadian Land Surface Scheme (CLASS). Three tower fluxes located in south-central Saskatchewan were part of the Boreal Ecosystem-Atmosphere Study (BOREAS) program which monitored climate variables and fluxes for complete annual cycles within pure, mature forest stands of old aspen, old black spruce, and old jack pine. The data is used develop and validate process models of the carbon and water cycles. The objective is to better understand the sequestration of carbon by the boreal forest in relation to vegetation type and climate. 6 figs.

  8. Variation and balance of positive air ion concentrations in a boreal forest

    Directory of Open Access Journals (Sweden)

    U. Hõrrak

    2008-02-01

    Full Text Available Air ions are characterized on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. The air ions were discriminated as small ions (charged molecular aggregates of the diameter of less than 2.5 nm, intermediate ions (charged aerosol particles of the diameter of 2.5–8 nm, and large ions (charged aerosol particles of the diameter of 8–20 nm. Statistical characteristics of the ion concentrations and the parameters of ion balance in the atmosphere are presented separately for the nucleation event days and non-event days. In the steady state, the ionization rate is balanced with the loss of small ions, which is expressed as the product of the small ion concentration and the ion sink rate. The widely known sinks of small ions are the recombination with small ions of opposite polarity and attachment to aerosol particles. The dependence of small ion concentration on the concentration of aerosol particles was investigated applying a model of the bipolar diffusion charging of particles by small ions. When the periods of relative humidity above 95% and wind speed less than 0.6 m s−1 were excluded, then the small ion concentration and the theoretically calculated small ion sink rate were closely negatively correlated (correlation coefficient −87%. However, an extra ion loss term of the same magnitude as the ion loss onto aerosol particles is needed for a quantitative explanation of the observations. This term is presumably due to the small ion deposition on coniferous forest. The hygroscopic growth correction of the measured aerosol particle size distributions was also found to be necessary for the proper estimation of the ion sink rate. In the case of nucleation burst events, the concentration of small positive ions followed the general balance equation, no extra ion loss in addition to the deposition on coniferous forest was detected, and the

  9. Carbon stock and carbon turnover in boreal and temperate forests - Integration of remote sensing data and global vegetation models

    Science.gov (United States)

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

    2016-04-01

    Long-term vegetation dynamics are one of the key uncertainties of the carbon cycle. There are large differences in simulated vegetation carbon stocks and fluxes including productivity, respiration and carbon turnover between global vegetation models. Especially the implementation of climate-related mortality processes, for instance drought, fire, frost or insect effects, is often lacking or insufficient in current models and their importance at global scale is highly uncertain. These shortcomings have been due to the lack of spatially extensive information on vegetation carbon stocks, which cannot be provided by inventory data alone. Instead, we recently have been able to estimate northern boreal and temperate forest carbon stocks based on radar remote sensing data. Our spatially explicit product (0.01° resolution) shows strong agreement to inventory-based estimates at a regional scale and allows for a spatial evaluation of carbon stocks and dynamics simulated by global vegetation models. By combining this state-of-the-art biomass product and NPP datasets originating from remote sensing, we are able to study the relation between carbon turnover rate and a set of climate indices in northern boreal and temperate forests along spatial gradients. We observe an increasing turnover rate with colder winter temperatures and longer winters in boreal forests, suggesting frost damage and the trade-off between frost adaptation and growth being important mortality processes in this ecosystem. In contrast, turnover rate increases with climatic conditions favouring drought and insect outbreaks in temperate forests. Investigated global vegetation models from the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP), including HYBRID4, JeDi, JULES, LPJml, ORCHIDEE, SDGVM, and VISIT, are able to reproduce observation-based spatial climate - turnover rate relationships only to a limited extent. While most of the models compare relatively well in terms of NPP, simulated

  10. Harvesting interacts with climate change to affect future habitat quality of a focal species in eastern Canada's boreal forest.

    Science.gov (United States)

    Tremblay, Junior A; Boulanger, Yan; Cyr, Dominic; Taylor, Anthony R; Price, David T; St-Laurent, Martin-Hugues

    2018-01-01

    Many studies project future bird ranges by relying on correlative species distribution models. Such models do not usually represent important processes explicitly related to climate change and harvesting, which limits their potential for predicting and understanding the future of boreal bird assemblages at the landscape scale. In this study, we attempted to assess the cumulative and specific impacts of both harvesting and climate-induced changes on wildfires and stand-level processes (e.g., reproduction, growth) in the boreal forest of eastern Canada. The projected changes in these landscape- and stand-scale processes (referred to as "drivers of change") were then assessed for their impacts on future habitats and potential productivity of black-backed woodpecker (BBWO; Picoides arcticus), a focal species representative of deadwood and old-growth biodiversity in eastern Canada. Forest attributes were simulated using a forest landscape model, LANDIS-II, and were used to infer future landscape suitability to BBWO under three anthropogenic climate forcing scenarios (RCP 2.6, RCP 4.5 and RCP 8.5), compared to the historical baseline. We found climate change is likely to be detrimental for BBWO, with up to 92% decline in potential productivity under the worst-case climate forcing scenario (RCP 8.5). However, large declines were also projected under baseline climate, underlining the importance of harvest in determining future BBWO productivity. Present-day harvesting practices were the single most important cause of declining areas of old-growth coniferous forest, and hence appeared as the single most important driver of future BBWO productivity, regardless of the climate scenario. Climate-induced increases in fire activity would further promote young, deciduous stands at the expense of old-growth coniferous stands. This suggests that the biodiversity associated with deadwood and old-growth boreal forests may be greatly altered by the cumulative impacts of natural and

  11. Inclusion of Additional Plant Species and Trait Information in Dynamic Vegetation Modeling of Arctic Tundra and Boreal Forest Ecosystem

    Science.gov (United States)

    Euskirchen, E. S.; Patil, V.; Roach, J.; Griffith, B.; McGuire, A. D.

    2015-12-01

    Dynamic vegetation models (DVMs) have been developed to model the ecophysiological characteristics of plant functional types in terrestrial ecosystems. They have frequently been used to answer questions pertaining to processes such as disturbance, plant succession, and community composition under historical and future climate scenarios. While DVMs have proved useful in these types of applications, it has often been questioned if additional detail, such as including plant dynamics at the species-level and/or including species-specific traits would make these models more accurate and/or broadly applicable. A sub-question associated with this issue is, 'How many species, or what degree of functional diversity, should we incorporate to sustain ecosystem function in modeled ecosystems?' Here, we focus on how the inclusion of additional plant species and trait information may strengthen dynamic vegetation modeling in applications pertaining to: (1) forage for caribou in northern Alaska, (2) above- and belowground carbon storage in the boreal forest and lake margin wetlands of interior Alaska, and (3) arctic tundra and boreal forest leaf phenology. While the inclusion of additional information generally proved valuable in these three applications, this additional detail depends on field data that may not always be available and may also result in increased computational complexity. Therefore, it is important to assess these possible limitations against the perceived need for additional plant species and trait information in the development and application of dynamic vegetation models.

  12. Tree rings provide early warning signals of jack pine mortality across a moisture gradient in the southern boreal forest

    Science.gov (United States)

    Mamet, S. D.; Chun, K. P.; Metsaranta, J. M.; Barr, A. G.; Johnstone, J. F.

    2015-08-01

    Recent declines in productivity and tree survival have been widely observed in boreal forests. We used early warning signals (EWS) in tree ring data to anticipate premature mortality in jack pine (Pinus banksiana)—an extensive and dominant species occurring across the moisture-limited southern boreal forest in North America. We sampled tree rings from 113 living and 84 dead trees in three soil moisture regimes (subxeric, submesic, subhygric) in central Saskatchewan, Canada. We reconstructed annual increments of tree basal area to investigate (1) whether we could detect EWS related to mortality of individual trees, and (2) how water availability and tree growth history may explain the mortality warning signs. EWS were evident as punctuated changes in growth patterns prior to transition to an alternative state of reduced growth before dying. This transition was likely triggered by a combination of severe drought and insect outbreak. Higher moisture availability associated with a soil moisture gradient did not appear to reduce tree sensitivity to stress-induced mortality. Our results suggest tree rings offer considerable potential for detecting critical transitions in tree growth, which are linked to premature mortality.

  13. Modelling the influence of ectomycorrhizal decomposition on plant nutrition and soil carbon sequestration in boreal forest ecosystems.

    Science.gov (United States)

    Baskaran, Preetisri; Hyvönen, Riitta; Berglund, S Linnea; Clemmensen, Karina E; Ågren, Göran I; Lindahl, Björn D; Manzoni, Stefano

    2017-02-01

    Tree growth in boreal forests is limited by nitrogen (N) availability. Most boreal forest trees form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve the uptake of inorganic N and also have the capacity to decompose soil organic matter (SOM) and to mobilize organic N ('ECM decomposition'). To study the effects of 'ECM decomposition' on ecosystem carbon (C) and N balances, we performed a sensitivity analysis on a model of C and N flows between plants, SOM, saprotrophs, ECM fungi, and inorganic N stores. The analysis indicates that C and N balances were sensitive to model parameters regulating ECM biomass and decomposition. Under low N availability, the optimal C allocation to ECM fungi, above which the symbiosis switches from mutualism to parasitism, increases with increasing relative involvement of ECM fungi in SOM decomposition. Under low N conditions, increased ECM organic N mining promotes tree growth but decreases soil C storage, leading to a negative correlation between C stores above- and below-ground. The interplay between plant production and soil C storage is sensitive to the partitioning of decomposition between ECM fungi and saprotrophs. Better understanding of interactions between functional guilds of soil fungi may significantly improve predictions of ecosystem responses to environmental change. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  14. Below-ground organic matter accumulation along a boreal forest fertility gradient relates to guild interaction within fungal communities.

    Science.gov (United States)

    Kyaschenko, Julia; Clemmensen, Karina E; Karltun, Erik; Lindahl, Björn D

    2017-12-01

    Plant-soil interactions link ecosystem fertility and organic matter accumulation below ground. Soil microorganisms play a central role as mediators of these interactions, but mechanistic understanding is still largely lacking. Correlative data from a coniferous forest ecosystem support the hypothesis that interactions between fungal guilds play a central role in regulating organic matter accumulation in relation to fertility. With increasing ecosystem fertility, the proportion of saprotrophic basidiomycetes increased in deeper organic layers, at the expense of ectomycorrhizal fungal species. Saprotrophs correlated positively with the activity of oxidative enzymes, which in turn favoured organic matter turnover and nitrogen recycling to plants. Combined, our findings are consistent with a fungus-mediated feedback loop, which results in a negative correlation between ecosystem fertility and below-ground carbon storage. These findings call for a shift in focus from plant litter traits to fungal traits in explaining organic matter dynamics and ecosystem fertility in boreal forests. © 2017 John Wiley & Sons Ltd/CNRS.

  15. Threshold Responses of Aspen and Spruce Growth to Temperature May Presage a Regime Shift in the Boreal Forest

    Science.gov (United States)

    Lloyd, A. H.; Duffy, P.; Mann, D. H.; Leonawicz, M.; Blumstein, M.; Pendall, E.

    2011-12-01

    Warming in boreal regions may eventually lead to the demise of evergreen coniferous forest and its replacement by either an open parkland of more drought-tolerant deciduous species like aspen, or by treeless steppe vegetation. We examined the possibility of warming-induced regime shifts in the boreal forest by quantifying the response of tree growth to climate on steep, south-facing bluffs in interior Alaska. These sites are the ecotone between forest and subarctic steppe vegetation, and represent the warmest, driest sites occupied by trees in the boreal forests of interior Alaska. We collected tree cores from aspen (Populus tremula) and white spruce (Picea glauca) at south-facing bluffs in interior Alaska (n=9 for white spruce, n=5 for aspen). Crossdated chronologies of detrended, standardized ring-widths were produced for each species at each site, and growth response to climate was quantified using generalized boosting models (spruce) and random forest regression (aspen). These analyses yielded three important insights into the potential for regime shifts in the warmer areas of the boreal forest. First, our results highlighted the surprising similarity in growth response of aspen and spruce. We expected to find that aspen would be more tolerant of warm, dry conditions than white spruce. In contrast, we found that the two species had broadly similar responses to climate, preferring cooler and wetter conditions. This finding suggests that a continued trend towards warmer and drier conditions is more likely to lead rapidly to the replacement of forest vegetation by steppe grassland, rather than the replacement of white spruce by aspen. Second, we identified strongly nonlinear responses to climate in both species; the use of analytical methods capable of detecting and describing nonlinear relationships between growth and climate thus proved to be critical. For both species, steep thresholds in growth response to temperature occurred, particularly in spring. Small

  16. Se Concentrations in Epiphytic Lichens From the Boreal Forest of Forthern Québec

    Science.gov (United States)

    Marin, L.; Lhomme, J.; Carignan, J.

    2004-05-01

    The knowledge of Se concentration in environmental samples is important because this element may be both toxic and nutrient for live organisms. This study aims to characterise the Se concentration in lichen samples in order to document the variability of atmospheric fallout. Lichens are of particular interest because their epiphytic character makes them totally dependant of atmospheric nutrients, so that their chemical composition reflects that of atmospheric matter. Lichens hanging on tree branches were sampled in various location of the boreal forest of northern Québec. We developed a separation and pre-concentration technique for Se analysis of low mineral matrix samples by GFAAS. After mineralisation and addition of a Se-free mineral charge to the sample, total Se is reduced to Se IV and fixed onto a thiol cotton. The latter is dissolved and directly analysed by GFAAS. A limit of determination of 0.02 ppm in the solid sample and a precision (relative standard deviation) varying from 3 to 15% was found through the course of this study. Our results are very similar to the certified values of the reference materials analysed, suggesting a good accuracy of the method for organic materials. Some lichen samples were also analysed by INAA and the agreement between results obtained by both techniques is not always perfect. There is, however, no systematic bias between the methods. Some samples agree within analytical uncertainty (about 5%), whereas others differ by more than 20%. The most probable reason why such discrepancies are observed is because these lichen samples were not crushed and homogenised before analysis. Indeed, some duplicate samples analysed by INAA yielded results that differed by more than 20%, while other agreed within 2%. Considering these facts, the overall agreement between GFAAS and INAA is pretty much satisfactory. The Se concentrations measured in lichens vary from 1.2 to 0.3 ppm and decrease from the coast of Hudson Bay towards inland at

  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. 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

  19. Combined retrievals of boreal forest fire aerosol properties with a polarimeter and lidar

    Science.gov (United States)

    Knobelspiesse, K.; Cairns, B.; Ottaviani, M.; Ferrare, R.; Hair, J.; Hostetler, C.; Obland, M.; Rogers, R.; Redemann, J.; Shinozuka, Y.; Clarke, A.; Freitag, S.; Howell, S.; Kapustin, V.; McNaughton, C.

    2011-07-01

    Absorbing aerosols play an important, but uncertain, role in the global climate. Much of this uncertainty is due to a lack of adequate aerosol measurements. While great strides have been made in observational capability in the previous years and decades, it has become increasingly apparent that this development must continue. Scanning polarimeters have been designed to help resolve this issue by making accurate, multi-spectral, multi-angle polarized observations. This work involves the use of the Research Scanning Polarimeter (RSP). The RSP was designed as the airborne prototype for the Aerosol Polarimetery Sensor (APS), which was due to be launched as part of the (ultimately failed) NASA Glory mission. Field observations with the RSP, however, have established that simultaneous retrievals of aerosol absorption and vertical distribution over bright land surfaces are quite uncertain. We test a merger of RSP and High Spectral Resolution Lidar (HSRL) data with observations of boreal forest fire smoke, collected during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS). During ARCTAS, the RSP and HSRL instruments were mounted on the same aircraft, and validation data were provided by instruments on an aircraft flying a coordinated flight pattern. We found that the lidar data did indeed improve aerosol retrievals using an optimal estimation method, although not primarily because of the contraints imposed on the aerosol vertical distribution. The more useful piece of information from the HSRL was the total column aerosol optical depth, which was used to select the initial value (optimization starting point) of the aerosol number concentration. When ground based sun photometer network climatologies of number concentration were used as an initial value, we found that roughly half of the retrievals had unrealistic sizes and imaginary indices, even though the retrieved spectral optical depths agreed within uncertainties to

  20. Combined Retrievals of Boreal Forest Fire Aerosol Properties with a Polarimeter and Lidar

    Science.gov (United States)

    Knobelspiesse, K.; Cairns, B.; Ottaviani, M.; Ferrare, R.; Haire, J.; Hostetler, C.; Obland, M.; Rogers, R.; Redemann, J.; Shinozuka, Y.; hide

    2011-01-01

    Absorbing aerosols play an important, but uncertain, role in the global climate. Much of this uncertainty is due to a lack of adequate aerosol measurements. While great strides have been made in observational capability in the previous years and decades, it has become increasingly apparent that this development must continue. Scanning polarimeters have been designed to help resolve this issue by making accurate, multi-spectral, multi-angle polarized observations. This work involves the use of the Research Scanning Polarimeter (RSP). The RSP was designed as the airborne prototype for the Aerosol Polarimetery Sensor (APS), which was due to be launched as part of the (ultimately failed) NASA Glory mission. Field observations with the RSP, however, have established that simultaneous retrievals of aerosol absorption and vertical distribution over bright land surfaces are quite uncertain. We test a merger of RSP and High Spectral Resolution Lidar (HSRL) data with observations of boreal forest fire smoke, collected during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS). During ARCTAS, the RSP and HSRL instruments were mounted on the same aircraft, and validation data were provided by instruments on an aircraft flying a coordinated flight pattern. We found that the lidar data did indeed improve aerosol retrievals using an optimal estimation method, although not primarily because of the constraints imposed on the aerosol vertical distribution. The more useful piece of information from the HSRL was the total column aerosol optical depth, which was used to select the initial value (optimization starting point) of the aerosol number concentration. When ground based sun photometer network climatologies of number concentration were used as an initial value, we found that roughly half of the retrievals had unrealistic sizes and imaginary indices, even though the retrieved spectral optical depths agreed within uncertainties to

  1. An analysis of controls on fire activity in boreal Canada: comparing models built with different temporal resolutions

    Science.gov (United States)

    Marc-Andre Parisien; Sean A. Parks; Meg A. Krawchuk; John M. Little; Mike D. Flannigan; Lynn M. Gowman; Max A. Moritz

    2014-01-01

    Fire regimes of the Canadian boreal forest are driven by certain environmental factors that are highly variable from year to year (e.g., temperature, precipitation) and others that are relatively stable (e.g., land cover, topography). Studies examining the relative influence of these environmental drivers on fire activity suggest that models making explicit use of...

  2. 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.

  3. Understanding the Combined Influence of Boreal Landuse and Climate Change on Catchment Functioning through Virtual Forest Alterations

    Science.gov (United States)

    Teutschbein, Claudia; Grabs, Thomas; Karlsen, Reinert H.; Laudon, Hjalmar; Bishop, Kevin

    2017-04-01

    changes in streamflow signatures, which were then used to analyse hydrological consequences of physical catchment perturbations in a climate change context. We created three virtual forest change cases and made an attempt to predict the combined influence of boreal landscape forms and climate change in these cases. Our analysis showed a strong connection between the forest cover extend and the sensitivity of different components of a catchment's hydrological regime to changing climate conditions, which emphasizes the need to redefine forestry goals and practices in advance given climate change-related risks and uncertainties.

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

    Science.gov (United States)

    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

  5. Quantifying fire severity, carbon, and nitrogen emissions in Alaska's boreal forest

    Science.gov (United States)

    Leslie A. Boby; Edward A.G. Schuur; Michelle C. Mack; David Verbyla; Jill F. Johnstone

    2010-01-01

    The boreal region stores a large proportion of the world's terrestrial carbon (C) and is subject to high-intensity, stand-replacing wildfires that release C and nitrogen (N) stored in biomass and soils through combustion. While severity and extent of fires drives overall emissions, methods for accurately estimating fire severity are poorly tested in this unique...

  6. Vulnerability of carbon storage in North American boreal forests to wildfires during the 21st century

    Science.gov (United States)

    M.S. Balshi; A.D. McGuire; P. Duffy; M. Flannigan; D.W. Kicklighter; J. Melillo

    2009-01-01

    We use a gridded data set developed with a multivariate adaptive regression spline approach to determine how area burned varies each year with changing climatic and fuel moisture conditions. We apply the process-based Terrestrial Ecosystem Model to evaluate the role of future fire on the carbon dynamics of boreal North America in the context of changing atmospheric...

  7. The ecology of snowshoe hares in northern boreal forests [Chapter 6

    Science.gov (United States)

    Karen E. Hodges

    2000-01-01

    Snowshoe hares exhibit eight to 11 year population fluctuations across boreal North America, typically with an amplitude of 10 to 25 fold. These fluctuations are synchronous across the continent, with the most recent peak densities occurring in 1990 and 1991. The numeric cycle is driven by changes in survival and reproduction, with annual survival of adults...

  8. Simulations of atmospheric OH, O3 and NO3 reactivities within and above the boreal forest

    DEFF Research Database (Denmark)

    Mogensen, D.; Gierens, R.; Crowley, J. N.

    2015-01-01

    Using the 1-D atmospheric chemistry transport model SOSAA, we have investigated the atmospheric reactivity of a boreal forest ecosystem during the HUMPPA-COPEC-10 campaign (summer 2010, at SMEAR II in southern Finland). For the very first time, we present vertically resolved model simulations of ...

  9. Root-associated ectomycorrhizal fungi shared by various boreal forest seedlings naturally regenerating after a fire in interior Alaska and correlation of different fungi with host growth responses

    Science.gov (United States)

    Elizabeth Bent; Preston Kiekel; Rebecca Brenton; D.Lee. Taylor

    2011-01-01

    The role of common mycorrhizal networks (CMNs) in postfire boreal forest successional trajectories is unknown. We investigated this issue by sampling a 50-m by 40-m area of naturally regenerating black spruce (Picea mariana), trembling aspen, (Populus tremuloides), and paper birch (Betula papyrifera)...

  10. Roads, logging, and the large-mammal community of an eastern Canadian boreal forest

    National Research Council Canada - National Science Library

    Bowman, Jeff; Ray, Justina C; Magoun, Audrey J; Johnson, Devin S; Dawson, F. N

    2010-01-01

    .... We estimated occurrence probability in 575 sample units for woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)), wolverine (Gulo gulo (L., 1758)), gray wolf (Canis lupus L., 1758), moose (Alces alces (L., 1758...

  11. Differences in ecosystem carbon distribution and nutrient cycling linked to forest tree species composition in a mid-successional boreal forest

    Science.gov (United States)

    Melvin, April M.; Mack, Michelle C.; Johnstone, Jill F.; McGuire, A. David; Genet, Helene; Schuur, Edward A.G.

    2015-01-01

    In the boreal forest of Alaska, increased fire severity associated with climate change is expanding deciduous forest cover in areas previously dominated by black spruce (Picea mariana). Needle-leaf conifer and broad-leaf deciduous species are commonly associated with differences in tree growth, carbon (C) and nutrient cycling, and C accumulation in soils. Although this suggests that changes in tree species composition in Alaska could impact C and nutrient pools and fluxes, few studies have measured these linkages. We quantified C, nitrogen, phosphorus, and base cation pools and fluxes in three stands of black spruce and Alaska paper birch (Betula neoalaskana) that established following a single fire event in 1958. Paper birch consistently displayed characteristics of more rapid C and nutrient cycling, including greater aboveground net primary productivity, higher live foliage and litter nutrient concentrations, and larger ammonium and nitrate pools in the soil organic layer (SOL). Ecosystem C stocks (aboveground + SOL + 0–10 cm mineral soil) were similar for the two species; however, in black spruce, 78% of measured C was found in soil pools, primarily in the SOL, whereas aboveground biomass dominated ecosystem C pools in birch forest. Radiocarbon analysis indicated that approximately one-quarter of the black spruce SOL C accumulated prior to the 1958 fire, whereas no pre-fire C was observed in birch soils. Our findings suggest that tree species exert a strong influence over C and nutrient cycling in boreal forest and forest compositional shifts may have long-term implications for ecosystem C and nutrient dynamics.

  12. Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) experiment: design, execution and science overview

    Science.gov (United States)

    Palmer, P. I.; Parrington, M.; Lee, J. D.; Lewis, A. C.; Rickard, A. R.; Bernath, P. F.; Duck, T. J.; Waugh, D. L.; Tarasick, D. W.; Andrews, S.; Aruffo, E.; Bailey, L. J.; Barrett, E.; Bauguitte, S. J.-B.; Curry, K. R.; Di Carlo, P.; Chisholm, L.; Dan, L.; Forster, G.; Franklin, J. E.; Gibson, M. D.; Griffin, D.; Helmig, D.; Hopkins, J. R.; Hopper, J. T.; Jenkin, M. E.; Kindred, D.; Kliever, J.; Le Breton, M.; Matthiesen, S.; Maurice, M.; Moller, S.; Moore, D. P.; Oram, D. E.; O'Shea, S. J.; Owen, R. Christopher; Pagniello, C. M. L. S.; Pawson, S.; Percival, C. J.; Pierce, J. R.; Punjabi, S.; Purvis, R. M.; Remedios, J. J.; Rotermund, K. M.; Sakamoto, K. M.; da Silva, A. M.; Strawbridge, K. B.; Strong, K.; Taylor, J.; Trigwell, R.; Tereszchuk, K. A.; Walker, K. A.; Weaver, D.; Whaley, C.; Young, J. C.

    2013-02-01

    We describe the design and execution of the BORTAS (Quantifying the impact of BOReal forest fires on Tropospheric oxidants using Aircraft and Satellites) experiment, which has the overarching objective of understanding the chemical aging of airmasses that contain the emission products from seasonal boreal wildfires and how these airmasses subsequently impact downwind atmospheric composition. The central focus of the experiment was a two-week deployment of the UK BAe-146-301 Atmospheric Research Aircraft (ARA) over eastern Canada. The planned July 2010 deployment of the ARA was postponed by 12 months because of activities related to the dispersal of material emitted by the Eyjafjallajökull volcano. However, most other planned model and measurement activities, including ground-based measurements at the Dalhousie University Ground Station (DGS), enhanced ozonesonde launches, and measurements at the Pico Atmospheric Observatory in the Azores, went ahead and constituted phase A of the experiment. Phase B of BORTAS in July 2011 included the same measurements, but included the ARA, special satellite observations and a more comprehensive measurement suite at the DGS. The high-frequency aircraft data provided a comprehensive snapshot of the pyrogenic plumes from wildfires. The coordinated ground-based and sonde data provided detailed but spatially-limited information that put the aircraft data into context of the longer burning season. We coordinated aircraft vertical profiles and overpasses of the NASA Tropospheric Emission Spectrometer and the Canadian Atmospheric Chemistry Experiment. These space-borne data, while less precise than other data, helped to relate the two-week measurement campaign to larger geographical and longer temporal scales. We interpret these data using a range of chemistry models: from a near-explicit gas-phase chemical mechanism, which tests out understanding of the underlying chemical mechanism, to regional and global 3-D models of atmospheric

  13. Reindeer grazing in subarctic boreal forest - influences on the soil carbon dynamics

    Science.gov (United States)

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

    2015-04-01

    Reindeer (Rangifer tarandus L.) are the most important large mammalian herbivores in the northern ecosystems , which have many effects on plant diversity, soil nutrient cycling and soil organic matter decomposition. Changes caused by reindeer in vegetation have indirect effects on physical features of the soil e.g. soil microclimate, root biomass and also on soil C dynamics. Earlier, the role of reindeer grazing in ground vegetation dynamics and in soil carbon (C) dynamics has been mostly investigated in open tundra heaths. The objectives of this study were to examine if and how the reindeer grazing (and the possible temperature changes in soil caused by heavy grazing) is affecting the soil C dynamics (CO2 efflux from the soil, C storage in soil, microbial biomass in the soil). In a field experiment in Finnish Lapland, in Värriö Strict Nature Reserve (67° 46' N, 29° 35' E) we have assessed the changes occurring in above- and belowground biomasses, and soil C dynamics (CO2 efflux, soil C content, soil microbial biomass C) among areas grazed and ungrazed by reindeer. Our study areas are located in the northern boreal subarctic coniferous forest at the zone of the last intact forest landscapes in Fennoscandia, where large areas of relatively undisturbed subarctic Scots pine (Pinus sylvestris L.) forests can still be found. The sample plots located in the Värriö Strict Nature Reserve (10 sample plots in total established in year 2013) are situated along the borderline between Finland and Russia, where the ungrazed area was excluded from the reindeer grazing already in 1918, to prevent the Finnish reindeer from going to the Russian side and there are not many reindeer on Russian side of the area. To characterize the stands we have established circular sample plots on areas with a radius of 11.28 m, where different tree characteristics were measured (diameter at 1.3 m, height, height of a tree, crown height, crown diameter, stand age, etc.). On every sample plot

  14. Modeling effects of climate change on spruce-fir forest ecosystems: Changes in the montane ecotone between boreal and temperate forests in the Green Mountains, U.S.A, from forest edge detection in Landsat TM imagery,1989 to 2011

    Science.gov (United States)

    Foster, J. R.; D'Amato, A. W.

    2014-12-01

    Climate change is projected to affect the integrity of forested ecosystems worldwide. One forest type expected to be severely impacted is the eastern spruce-fir forest, because it is already at the extreme elevational and latitudinal limits of its range within the northern United States. Large-scale bioclimactic models predict declining habitat suitability for spruce and fir species, while causing drought and thermal stress on remnant trees. As rising temperatures reduce or eliminate habitat throughout much of the current spruce-fir range, growth and regeneration of hardwood forests or more southerly conifers will be favored. The ecotone between northern hardwood forests and montane boreal forests was recently reported to have shifted approximately 100 m upslope over the last 20-40 years in the Green Mountains of Vermont, U.S.A. The research behind this finding relied on long-term forest plot data and change analysis of narrow transects (6 m width) on aerial photos and SPOT imagery. In the White Mountains of New Hampshire, U.S.A., research using vegetation indices from Landsat data reported a conflicting finding; that coniferous vegetation was increasing downslope of the existing ecotone. We carefully matched and topographically corrected Landsat images from 1989 through 2011 to comprehensively map the boreal-temperate forest ecotone throughout the Green Mountains in Vermont, U.S.A. We used edge detection and linear mixed models to evaluate whether the ecotone changed in elevation over 20 years, and whether rates of change varied with Latitude or aspect. We found that the elevation of the boreal-temperate forest ecotone, and changes in its location over 20 years, were more variable than reported in recent studies. While the ecotone moved to higher elevations in some locations at reported rates, these rates were at the tales of the distribution of elevational change. Other locations showed downward movement of the ecotone, while for the majority of sites, no change

  15. Why might forest companies certify? Results from a Canadian survey

    NARCIS (Netherlands)

    Takahashi, T.; Kooten, van G.C.; Vertinsky, I.

    2003-01-01

    During the late 1980s/early 1990s, voluntary forest certification emerged as a new market-based incentive mechanism and had an important influence on the way the world's forests are managed. To understand the mechanism of its diffusion, we employed a survey instrument and probit regression analysis

  16. Carbon Cycling, Climate Regulation, and Disturbances in Canadian Forests: Scientific Principles for Management

    Directory of Open Access Journals (Sweden)

    Jean-Sébastien Landry

    2015-01-01

    Full Text Available Canadian forests are often perceived as pristine and among the last remaining wilderness, but the majority of them are officially managed and undergo direct land use, mostly for wood harvest. This land use has modified their functions and properties, often inadvertently (e.g., age structure but sometimes purposefully (e.g., fire suppression. Based on a review of the literature pertaining to carbon cycling, climate regulation, and disturbances from logging, fire, and insect outbreaks, we propose five scientific principles relevant for Canadian managed forests. Among these, a principle we wish to highlight is the need to properly account for the management-related fossil fuel emissions, because they will affect the global carbon cycle and climate for millennia unless massive atmospheric carbon dioxide removal becomes a reality. We also use these five principles to address questions of current interest to research scientists, forest managers, and policy makers. Our review focusses on total ecosystem carbon storage and various mechanisms through which forests affect climate, in particular albedo and aerosols forcings—including how disturbances influence all these elements—but also touches on other ecosystem goods and services. Our review underscores the importance of conducting >100-year time horizon studies of carbon cycling, climate regulation, and disturbances in Canadian managed forests.

  17. Composition and temporal behavior of ambient ions in the boreal forest

    Directory of Open Access Journals (Sweden)

    M. Ehn

    2010-09-01

    Full Text Available A recently developed atmospheric pressure interface mass spectrometer (APi-TOF measured the negative and positive ambient ion composition at a boreal forest site. As observed in previous studies, the negative ions were dominated by strong organic and inorganic acids (e.g. malonic, nitric and sulfuric acid, whereas the positive ions consisted of strong bases (e.g. alkyl pyridines and quinolines. Several new ions and clusters of ions were identified based on their exact masses, made possible by the high resolution, mass accuracy and sensitivity of the APi-TOF. Time series correlograms aided in peak identification and assigning the atomic compositions to molecules. Quantum chemical calculations of proton affinities and cluster stabilities were also used to confirm the plausibility of the assignments. Acids in the gas phase are predominantly formed by oxidation in the gas phase, and thus the concentrations are expected to vary strongly between day and night. This was also the case in this study, where the negative ions showed strong diurnal behavior, whereas the daily changes in the positive ions were considerably smaller. A special focus in this work was the changes in the ion distributions occurring during new particle formation events. We found that sulfuric acid, together with its clusters, dominated the negative ion spectrum during these events. The monomer (HSO4 was the largest peak, together with the dimer (H2SO4 · HSO4 and trimer ((H2SO42 · HSO4. SO5 also tracked HSO4 at around 20% of the HSO4 concentration at all times. During the strongest events, the tetramer and a cluster with the tetramer and ammonia were also detected. Quantum chemical calculations predict that sulfuric acid clusters containing ammonia are much more stable when

  18. Development and analysis of a 12-year daily 1-km forest fire dataset across North America from NOAA/AVHRR

    Science.gov (United States)

    Ruiliang Pu; Zhanqing Li; Peng Gong; Ivan Csiszar; Robert Fraser; Wei-Min Hao; Shobha Kondragunta; Fuzhong Weng

    2007-01-01

    Fires in boreal and temperate forests play a significant role in the global carbon cycle. While forest fires in North America (NA) have been surveyed extensively by U.S. and Canadian forest services, most fire records are limited to seasonal statistics without information on temporal evolution and spatial expansion. Such dynamic information is crucial for modeling fire...

  19. Extensive forest leaf area survey aiming at detection of vegetation change in subarctic-boreal zone

    OpenAIRE

    Kusakabe,Tomoko; Tsuzuki,Hayato; Hughes,Gary; Sweda,Tatsuo

    2000-01-01

    The warming resulting from increasing anthropogenic carbon dioxide and other greenhouse gasses is expected to be most prominent in the subarctic-boreal region of the Northern Hemisphere. With the objective of setting up a baseline to monitor possible vegetation change in this region, a continuous vegetation profile extending 600km from Edmonton, Alberta to Cluff Lake, Saskatchewan, Canada was measured using an airborne infrared laser altimeter mounted on a helicopter. Then the distribution of...

  20. Influence of airborne chemical substances on the behaviour of radionuclides in boreal forest ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Steinnes, E. [Norwegian Univ. of Science and Technology, Dept. of Chemistry, Trondheim (Norway)

    2002-04-01

    Atmospheric deposition of chemical substances may influence the behaviour of radionuclides in soil and their uptake in plants. This is a fact that has so far received limited attention in radioecological studies. This paper presents briefly two cases where differences in atmospheric deposition of heavy metals from a strong pollution source and marine aerosols, respectively, influence the turnover of radionuclides in natural boreal ecosystems. (au)

  1. 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.

  2. Sensitivity of boreal forest regional water flux and net primary production simulations to sub-grid-scale land cover complexity

    Science.gov (United States)

    Kimball, J. S.; Running, S. W.; Saatchi, S. S.

    1999-11-01

    We use a general ecosystem process model (BIOME-BGC) coupled with remote sensing information to evaluate the sensitivity of boreal forest regional evapotranspiration (ET) and net primary production (NPP) to land cover spatial scale. Simulations were conducted over a 3 year period (1994-1996) at spatial scales ranging from 30 to 50 km within the BOREAS southern modeling subarea. Simulated fluxes were spatially complex, ranging from 0.1 to 3.9 Mg C ha-1 yr-1 and from 18 to 29 cm yr-1. Biomass and leaf area index heterogeneity predominantly controlled this complexity, while biophysical differences between deciduous and coniferous vegetation were of secondary importance. Spatial aggregation of land cover characteristics resulted in mean monthly NPP estimation bias from 25 to 48% (0.11-0.20 g C m-2 d-1) and annual estimation errors from 2 to 14% (0.04-0.31 Mg C ha-1 yr-1). Error was reduced at longer time intervals because coarse scale overestimation errors during spring were partially offset by underestimation of fine scale results during summer and winter. ET was relatively insensitive to land cover spatial scale with an average bias of less than 5% (0.04 kg m-2 d-1). Factors responsible for differences in scaling behavior between ET and NPP included compensating errors for ET calculations and boreal forest spatial and temporal NPP complexity. Careful consideration of landscape spatial and temporal heterogeneity is necessary to identify and mitigate potential error sources when using plot scale information to understand regional scale patterns. Remote sensing data integrated within an ecological process model framework provides an efficient mechanism to evaluate scaling behavior, interpret patterns in coarse resolution data, and identify appropriate scales of operation for various processes.

  3. Identification of novel Archaea in bacterioplankton of a boreal forest lake by phylogenetic analysis and fluorescent in situ hybridization(1).

    Science.gov (United States)

    Jurgens; Glöckner; Amann; Saano; Montonen; Likolammi; Münster

    2000-10-01

    We report here on novel groups of Archaea in the bacterioplankton of a small boreal forest lake studied by the culture-independent analysis of the 16S rRNA genes amplified directly from lake water in combination with fluorescent in situ hybridization (FISH). Polymerase chain reaction products were cloned and 28 of the 160 Archaea clones with around 900-bp-long 16S rRNA gene inserts, were sequenced. Phylogenetic analysis, including 642 Archaea sequences, confirmed that none of the freshwater clones were closely affiliated with known cultured Archaea. Twelve Archaea sequences from lake Valkea Kotinen (VAL) belonged to Group I of uncultivated Crenarchaeota and affiliated with environmental sequences from freshwater sediments, rice roots and soil as well as with sequences from an anaerobic digestor. Eight of the Crenarchaeota VAL clones formed a tight cluster. Sixteen sequences belonged to Euryarchaeota. Four of these formed a cluster together with environmental sequences from freshwater sediments and peat bogs within the order Methanomicrobiales. Five were affiliated with sequences from marine sediments situated close to marine Group II and three formed a novel cluster VAL III distantly related to the order Thermoplasmales. The remaining four clones formed a distinct clade within a phylogenetic radiation characterized by members of the orders Methanosarcinales and Methanomicrobiales on the same branch as rice cluster I, detected recently on rice roots and in anoxic bulk soil of flooded rice microcosms. FISH with specifically designed rRNA-targeted oligonucleotide probes revealed the presence of Methanomicrobiales in the studied lake. These observations indicate a new ecological niche for many novel 'non-extreme' environmental Archaea in the pelagic water of a boreal forest lake.

  4. Controls on variations in MODIS fire radiative power in Alaskan boreal forests: implications for fire severity conditions

    Science.gov (United States)

    Barrett, Kirsten; Kasischke, Eric S.

    2013-01-01

    Fire activity in the Alaskan boreal forest, though episodic at annual and intra-annual time scales, has experienced an increase over the last several decades. Increases in burned area and fire severity are not only releasing more carbon to the atmosphere, but likely shifting vegetation composition in the region towards greater deciduous dominance and a reduction in coniferous stands. While some recent studies have addressed qualitative differences between large and small fire years in the Alaskan boreal forest, the ecological effects of a greater proportion of burning occurring during large fire years and during late season fires have not yet been examined. Some characteristics of wildfires that can be detected remotely are related to fire severity and can provide new information on spatial and temporal patterns of burning. This analysis focused on boreal wildfire intensity (fire radiative power, or FRP) contained in the Moderate Resolution Imaging Spectroradiometer (MODIS) daily active fire product from 2003 to 2010. We found that differences in FRP resulted from seasonality and intra-annual variability in fire activity levels, vegetation composition, latitudinal variation, and fire spread behavior. Our studies determined two general categories of active fire detections: new detections associated with the spread of the fire front and residual pixels in areas that had already experienced front burning. Residual pixels had a lower average FRP than front pixels, but represented a high percentage of all pixels during periods of high fire activity (large fire years, late season burning, and seasonal periods of high fire activity). As a result, the FRP from periods of high fire activity was less intense than those from periods of low fire activity. Differences related to latitude were greater than expected, with higher latitudes burning later in the season and at a higher intensity than lower latitudes. Differences in vegetation type indicate that coniferous vegetation

  5. Limnological characteristics of 56 lakes in the Central Canadian Arctic Treeline Region

    Directory of Open Access Journals (Sweden)

    John P. SMOL

    2003-02-01

    Full Text Available Measured environmental variables from 56 lakes across the Central Canadian Treeline Region exhibited clear limnological differences among subpolar ecozones, reflecting strong latitudinal changes in biome characteristics (e.g. vegetation, permafrost, climate. Principal Components Analysis (PCA clearly separated forested sites from tundra sites based on distinct differences in limnological characteristics. Increases in major ions and related variables (e.g. dissolved inorganic carbon, DIC were higher in boreal forest sites in comparison to arctic tundra sites. The higher values recorded in the boreal forest lakes may be indirectly related to differences in climatic factors in these zones, such as the degree of permafrost development, higher precipitation and runoff, duration of ice-cover on the lakes, and thicker and better soil development. Similar to trends observed in DIC, substantially higher values for dissolved organic carbon (DOC were measured in boreal forest lakes than in arctic tundra lakes. This was likely due to higher amounts of catchment-derived DOC entering the lakes from coniferous leaf litter sources. Relative to arctic tundra lakes, boreal forest lakes had higher nutrient concentrations, particularly total nitrogen (TN, likely due to warmer conditions, a longer growing season, and higher precipitation, which would enhance nutrient cycling and primary productivity. Results suggest that modern aquatic environments at opposite sides of the central Canadian arctic treeline (i.e. boreal forest and arctic tundra exhibit distinct differences in water chemistry and physical conditions. These limnological trends may provide important information on possible future changes with additional warming.

  6. Evaluation of climate-related carbon turnover processes in global vegetation models for boreal and temperate forests.

    Science.gov (United States)

    Thurner, Martin; Beer, Christian; Ciais, Philippe; Friend, Andrew D; Ito, Akihiko; Kleidon, Axel; Lomas, Mark R; Quegan, Shaun; Rademacher, Tim T; Schaphoff, Sibyll; Tum, Markus; Wiltshire, Andy; Carvalhais, Nuno

    2017-08-01

    Turnover concepts in state-of-the-art global vegetation models (GVMs) account for various processes, but are often highly simplified and may not include an adequate representation of the dominant processes that shape vegetation carbon turnover rates in real forest ecosystems at a large spatial scale. Here, we evaluate vegetation carbon turnover processes in GVMs participating in the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP, including HYBRID4, JeDi, JULES, LPJml, ORCHIDEE, SDGVM, and VISIT) using estimates of vegetation carbon turnover rate (k) derived from a combination of remote sensing based products of biomass and net primary production (NPP). We find that current model limitations lead to considerable biases in the simulated biomass and in k (severe underestimations by all models except JeDi and VISIT compared to observation-based average k), likely contributing to underestimation of positive feedbacks of the northern forest carbon balance to climate change caused by changes in forest mortality. A need for improved turnover concepts related to frost damage, drought, and insect outbreaks to better reproduce observation-based spatial patterns in k is identified. As direct frost damage effects on mortality are usually not accounted for in these GVMs, simulated relationships between k and winter length in boreal forests are not consistent between different regions and strongly biased compared to the observation-based relationships. Some models show a response of k to drought in temperate forests as a result of impacts of water availability on NPP, growth efficiency or carbon balance dependent mortality as well as soil or litter moisture effects on leaf turnover or fire. However, further direct drought effects such as carbon starvation (only in HYBRID4) or hydraulic failure are usually not taken into account by the investigated GVMs. While they are considered dominant large-scale mortality agents, mortality mechanisms related to insects and

  7. Energy, water and carbon exchange in a boreal forest landscape - NOPEX experiences

    DEFF Research Database (Denmark)

    Halldin, S.; Gryning, Sven-Erik; Gottschalk, L.

    1999-01-01

    of the European boreal zone. This paper summarises results from NOPEX in its first phase, dealing with spring- and summertime conditions. Two concentrated field eff