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Characterizing the amount and configuration of forests can provide insights into habitat quality, biodiversity, and land use. The establishment of protected areas can be a mechanism for maintaining large, contiguous areas of forests, and the loss and fragmentation of forest habitat is a potential threat to Canada's national park system. Using the Earth Observation for Sustainable Development of Forests (EOSD) land cover product (EOSD LC 2000), we characterize the circa 2000 forest patterns in 26 of Canada's national parks and compare these to forest patterns in the ecological units surrounding these parks, referred to as the greater park ecosystem (GPE). Five landscape pattern metrics were analyzed: number of forest...
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We investigated total suspended particles (TSP) collected from central Alaska, USA for molecular compositions of secondary organic aerosol (SOA) derived from the oxidation of biogenic volatile organic compounds (BVOCs). Isoprene-, α-/β-pinene- and β-caryophyllene-SOA tracers were determined using gas chromatography-mass spectrometry. The concentration ranges of isoprene, α-/β-pinene and β-caryophyllene oxidation products were 0.02–18.6 ng m−3 (ave. 4.14 ng m−3), 0.42–8.24 ng m−3 (2.01 ng m−3) and 0.10–9 ng m−3 (1.53 ng m−3), respectively. Isoprene-SOA tracers showed higher concentrations in summer (ave. 8.77 ng m−3), whereas α-/β-pinene- and β-caryophyllene-SOA tracers exhibited highest levels in spring (3.55 ng...
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The extensive boreal biome is little studies relative to its global importance. Its high soil moisture and low temperatures result in large below-ground reservoirs of carbon (C) and nitrogen (N). Presently, such high-latitude ecosystems are undergoing the largest temperature increases in global warming. Change in soil temperature or moisture in the large pools of soil organic matter could fundamentally change ecosystem C and N budgets. Since 1990, we have conducted treeline studies in a small (800 ha) watershed in Noatak National Preserve, northwestern Alaska. Our objectives were to (1) gain an understanding of treeline dynamics, structure, and function; and (2) examine the effects of global climate change, particularly...
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The northern treeline is generally limited by available warmth. However, in recent years, more and more studies have identified drought stress as an additional limiting factor for tree growth in northern boreal forests and at treelines. Three growth responses to warming have been identified: increase in growth, decrease in growth, and nonsignificant correlation of tree growth with climate. Here we investigate the effect of drought stress on radial growth of white spruce at northern treelines along a longitudinal gradient spanning the entire Brooks Range in Alaska. We systematically sampled 687 white spruce at seven treeline sites. Where possible, we sampled three site types at a given site: high-density forest,...
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Increased light reaching streams as a result of riparian vegetation management is often thought to be responsible for enhanced algal productivity. However, concomitant changes in nutrients and other physical processes confound that interpretation. We manipulated light in two separate experiments to test the role of light as a controlling factor for periphyton productivity and biomass, and to observe invertebrate responses in small streams in central British Columbia, Canada. We did this by adding artificial light to reaches of three forested streams, and in a second experiment we used shadecloth to cover reaches of two streams flowing through clearcuts. Periphyton growth, productivity and composition, and macroinvertebrate...
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Pattern and extent of treeline change using sequential vertical aerial photography in the northern section of the Kluane Ranges of southwest Yukon are examined. One of the most common predictions is that continued global temperature increases will cause the tree-line to advance in elevation and latitude. Comparison of aerial photographs of southwest Yukon indicates significant changes in the spruce forest-shrub tundra transition. Many areas exhibit increased growth of individual spruce without an increase in stand density or an advance in spruce distribution. Increase in the elevational distribution of spruce is observed in comparatively fewer areas, typically in combination with other two types of change.
This study describes the community, population, and growth dynamics of Alnus tenuifolia (thinleaf alder) and implications for nutrient cycling on the Tanana River floodplains. Through symbiotic N-fixation inputs, alder contributed to soil N accumulation with time. N-fixation itself was likely limited by soil P. Soil N was positively related to alder stem density in early successional stands. Community structure varied along a temporal gradient of changing environmental characteristics, but variations in successional patterns were found. Landscape scale alder recruitment varied temporally and was apparently linked to interactions between geofluvial processes, seed production and dispersal, and herbivory. A widespread...
map background search result map search result map Method for Attenuation of White Phosphorus Contamination in Wetlands RELATIONSHIPS AMONG FIRES, FUNGI, AND SOIL DYNAMICS IN ALASKAN BOREAL FORESTS Experimental increases and reductions of light to streams: effects on periphyton and macroinvertebrate assemblages in a coniferous forest landscape Competitive interactions across a soil fertility gradient in a multispecies forest Alder (Alnus crispa) effects on soils in ecosystems of the Agashashok River valley, northwest Alaska Density dependence in an experimental boreal forest understory community Comment on 'Wetland drying and succession across the Kenai Peninsula Lowlands, south-central Alaska' Spruce beetles and forest ecosystems of south-central Alaska Longitudinal variation of radial growth at Alaska's northern treeline; recent changes and possible scenarios for the 21st century Soil nitrogen transformations and retention during a deciduous to coniferous successional transition Evidence of Recent Treeline Dynamics in Southwest Yukon from Aerial Photographs Treeline biogeochemistry and dynamics, Noatak National Preserve, northwestern Alaska Method for Attenuation of White Phosphorus Contamination in Wetlands Experimental increases and reductions of light to streams: effects on periphyton and macroinvertebrate assemblages in a coniferous forest landscape Soil nitrogen transformations and retention during a deciduous to coniferous successional transition RELATIONSHIPS AMONG FIRES, FUNGI, AND SOIL DYNAMICS IN ALASKAN BOREAL FORESTS Density dependence in an experimental boreal forest understory community Alder (Alnus crispa) effects on soils in ecosystems of the Agashashok River valley, northwest Alaska Treeline biogeochemistry and dynamics, Noatak National Preserve, northwestern Alaska Comment on 'Wetland drying and succession across the Kenai Peninsula Lowlands, south-central Alaska' Evidence of Recent Treeline Dynamics in Southwest Yukon from Aerial Photographs Spruce beetles and forest ecosystems of south-central Alaska Longitudinal variation of radial growth at Alaska's northern treeline; recent changes and possible scenarios for the 21st century Competitive interactions across a soil fertility gradient in a multispecies forest