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Detailed observations of stream, soil, and groundwater chemistry were used to determine the role of fire, permafrost and snowmelt processes on the fluxes of carbon, nitrogen and major solutes from interior Alaskan catchments. We examined an experimentally burned watershed and two reference watersheds that differ in permafrost coverage (high, 53%; medium-burn, 18%; and low, 4%) during the FROSTFIRE prescribed burn in July 1999. The fire elevated stream nitrate concentrations for a short period during the first post-fire storm, but nitrate declined thereafter, suggesting that less severe fires that leave an intact riparian zone may have only a short-term effect on stream chemistry. Nevertheless, we found fundamental...
This paper provides an overview of a project that synthesized available information on climate change for the southwest Yukon. This was done as a first step in a longer-term process of evaluating climate impacts, assessing risks to ecosystem and community values, and developing scenarios for adaptation. The overall intent of the work was to support informed forest management decision-making for the Champagne-Aishihik Traditional Territory (CATT) in the light of climate change. The objectives of this stage of the project were to: compile and improve access to existing baseline information needed to support informed management decisions in the face of climate change; to make this information available using several...
Climate change has the potential to affect the boreal forest of Canada. Forest fires are a crucial component of the boreal ecosystem and climate change may substantially alter the fire regime. Statistical relations between climate and forest fire were obtained by regression for three fire subdistricts (Old Crow, Mayo and Watson Lake) of Yukon Territory. The relations were derived from fire and climate records, available, in general, since 1960. Summer temperature was found to be positively correlated to forest fire occurrence, area burned, the Fire Weather Index and Seasonal Severity Rating. In most cases, summer precipitation and relative humidity were negatively correlated with these variables. Climate change...
Aim To understand: (1) how temperature, precipitation and stand age control the above-ground biomass carbon density (BCDa) of mature forests and its macroecology patterns across latitudes; (2) the age threshold for old-growth forests at a global scale. Location Global forests. Methods We compiled a database (897 sites) of mature forests between 80 and 1200 years old. The site data include latitude, longitude, mean annual temperature, mean annual precipitation, forest type, stand age, BCDa, living biomass (above- and below-ground biomass) carbon density and total (living plus dead) biomass carbon density. Based on the site data, we performed regression analyses to show how BCDa changes with climate and forest stand...
Tracking landscape-scale water status in high-latitude boreal systems is indispensible to understanding the fate of stored and sequestered carbon in a climate change scenario. Spaceborne synthetic aperture radar (SAR) imagery provides critical information for water and moisture status in Alaskan boreal environments at the landscape scale. When combined with results from optical sensor analyses, a complementary picture of vegetation, biomass, and water status emerges. Whereas L-band SAR showed better inherent capacity to map water status, C-band had much more temporal coverage in this study. Analysis through the use of L- and C-band SARs combined with Landsat Enhanced Thematic Mapper Plus (ETM+) enables landscape...
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The Spatial Alaskan Forest Ecosystem Dynamics (SAFED) model was validated across four of the most common vegetation types found in interior Alaska. The vegetation types were an aldef (Alnus spp.) - balsam poplar (Populus balsamifera L.) site (FP2), an old-growth balsam poplar and white spruce (Picea glauca (Moench) Voss) site (FP3), a mixed deciduous (primarily birch (Betula papyrifera Marsh.) and aspen (Populus tremuloides Michx.)) and white spruce site (UP2), and a mature white spruce site (UP3). The FP site types are common on the floodplain along the Tanana River and the UP site types are common in the uplands in interior Alaska. SAFED is based on nitrogen productivity for vegetation growth, litter fall quantity...
Northern peatlands in boreal and subarctic regions store about 500 Gt of carbon (C). Understanding the fate of this large C pool under a warmer climate is important, as temperatures in northern latitudes have increased quicker than the global averages over the past 100 years. Both regional climate (e.g., temperature and precipitation) and local factors (e.g., topography) influence peatland response to climate changes. To better understand peatland response to climate changes, paleoecological techniques were used to study the C accumulation and paleohydrololgy of peatlands in different Alaskan climate regions. In addition, local-scale factors were studied through comparison of two nearby peatlands in different surficial...
Large lightning-caused fires in the forested areas of Canada and Alaska account for most of the area burnt and are one of the main determiners of the age mosaic of the landscape. Generally such fires occur when positive mid-troposphere pressure anomalies persist for more than ten days during the fire season. Mid-troposphere anomalies are part of teleconnection patterns which are created by internal atmospheric and coupled sea/air dynamics. Large lightning fire occurrence and area burnt data were used to define eight major centres of large fire variability (Fire Regions) in the forested areas of Canada and Alaska between 1959 and 1999. Preferred positions of persistent positive mid-troposphere anomalies correlated...
Climate is a long-term driver of ecological change, but the rapidity with which climate is projected to change over the next century may push the limitations of ecological adaptability, to the detriment of biodiversity. Given their typically small populations, limiting biological traits and exposure to external stressors, species currently classified as "at risk" may be among the most vulnerable to climate change and least capable of adapting naturally. A screening level assessment of the impacts of climate change on endangered species in Canada was conducted by integrating knowledge of the current status and characteristics of each endangered species with projections of climate change and climate change impacts....
Fire is an important control on the carbon (C) balance of the boreal forest region. Here, we present findings from two complementary studies that examine how fire modifies soil organic matter properties, and how these modifications influence rates of decomposition and C exchange in black spruce (Picea mariana) ecosystems of interior Alaska. First, we used laboratory incubations to explore soil temperature, moisture, and vegetation effects on CO2 and DOC production rates in burned and unburned soils from three study regions in interior Alaska. Second, at one of the study regions used in the incubation experiments, we conducted intensive field measurements of net ecosystem exchange (NEE) and ecosystem respiration...
A 1000-yr record of forest fire activity has been developed using three annually dated ice cores from Eclipse Icefield, Yukon, Canada. Forest fire signals were identified as NH4+ residuals above a robust spline and corroborated by an empirical orthhogonal function (EOF) analysis that identified a chemical association in the NH4+ , C2 O42- and K+ records similar to that observed in forest fire plumes. These statistical techniques yielded similar records of forest fire activity, although the EOF analysis provides more conservative identification of forest fire signals. Comparison of forest fire signals in the Eclipse ice cores with the record of annual area burned in Alaska and the Yukon demonstrates that 80% of high...
The Kluane forest is unusual in that it is less productive than other boreal forests because it lies in a rain-shadow zone in the Yukon Territory. Densities of the boreal red-backed vole Clethrionomys rutilus are known to be food-limited in the Kluane region, and its food sources, mostly plants, could be rainfall-limited. Above-average rainfall in the Kluane region could reduce the summer water deficit, which would in turn enhance primary production and reduce food limitation in voles, ultimately leading to a population outbreak. We experimentally tested these two predictions by irrigating three sites in the boreal forest from 1995 to 1999, and concurrently comparing numbers of voles and availability of their potential...
Permafrost soils are large reservoirs of potentially labile carbon (C). Understanding the dynamics of C release from these soils requires us to account for the impact of wildfires, which are increasing in frequency as the climate changes. Boreal wildfires contribute to global emission of greenhouse gases (GHG[mdash]CO2, CH4 and N2O) and indirectly result in the thawing of near-surface permafrost. In this study, we aimed to define the impact of fire on soil microbial communities and metabolic potential for GHG fluxes in samples collected up to 1[thinsp]m depth from an upland black spruce forest near Nome Creek, Alaska. We measured geochemistry, GHG fluxes, potential soil enzyme activities and microbial community...
map background search result map search result map Mountain Pine Beetle in British Columbia 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 Rapid Cycling of Organic Nitrogen in Taiga Forest Ecosystems Human Impacts on the Fire Regime of Interior Alaska: Interactions among Fuels, Ignition Sources, and Fire Suppression Export of carbon, nitrogen and major solutes from a boreal forest watershed: The influence of fire and permafrost Human Impact on Fire Regime in Interior Alaska Boreal forest ecosystem dynamics. II. Application of the model to four vegetation types in interior Alaska Rapid Cycling of Organic Nitrogen in Taiga Forest Ecosystems Export of carbon, nitrogen and major solutes from a boreal forest watershed: The influence of fire and permafrost 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 Human Impacts on the Fire Regime of Interior Alaska: Interactions among Fuels, Ignition Sources, and Fire Suppression Boreal forest ecosystem dynamics. II. Application of the model to four vegetation types in interior Alaska Human Impact on Fire Regime in Interior Alaska Mountain Pine Beetle in British Columbia