Filters: Tags: Monitoring 1-Changes in Plant and Animal Distribution: Ecosystems (X)345 results (16ms)
Longitudinal variation of radial growth at Alaska's northern treeline; recent changes and possible scenarios for the 21st century
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,...
Latitudinal gradient of spruce forest understory and tundra phenology in Alaska as observed from satellite and ground-based data
The latitudinal gradient of the start of the growing season (SOS) and the end of the growing season (EOS) were quantified in Alaska (61°N to 71°N) using satellite-based and ground-based datasets. The Alaskan evergreen needleleaf forests are sparse and the understory vegetation has a substantial impact on the satellite signal. We evaluated SOS and EOS of understory and tundra vegetation using time-lapse camera images. From the comparison of three SOS algorithms for determining SOS from two satellite datasets (SPOT-VEGETATION and Terra-MODIS), we found that the satellite-based SOS timing was consistent with the leaf emergence of the forest understory and tundra vegetation. The ensemble average of SOS over all satellite...
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...
Methane Emissions from Natural Wetlands in the United States: Satellite-Derived Estimation Based on Ecosystem Carbon Cycling
Categories: Publication; Types: Citation; Tags: Monitoring 1-Changes in Plant and Animal Distribution: Ecosystems
Suitability of a young deciduous-dominated forest for American marten and the effects of forest removal
Comment on 'Wetland drying and succession across the Kenai Peninsula Lowlands, south-central Alaska'
Soil nitrogen transformations and retention during a deciduous to coniferous successional transition
Alder (Alnus crispa) effects on soils in ecosystems of the Agashashok River valley, northwest Alaska
Neotyphodium are fungal endosymbionts of grasses that reproduce asexually by infecting the host's seed. This relationship has traditionally been considered mutualistic, with the fungus improving host fitness by alleviating important stresses. To determine the importance of biotic and abiotic stresses in mediating the endophyte-grass interaction, I investigated the relationship between grazing pressure by collared pikas and Neotyphodium sp. infection frequency in the grass Festuca altaica in an alpine meadow. I conducted a factorial design experiment combining endophyte infection, grazing history, fungicide and fertilizer. Leaf demography and herbivory damage were monitored every two weeks. In areas with chronic...
Boreal forest ecosystem dynamics. II. Application of the model to four vegetation types in interior Alaska
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...
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...
Exploring ecological changes in Cook Inlet beluga whale habitat though traditional and local ecological knowledge of contributing factors for population decline
Denali National Park and Preserve Landcover Mapping Project Volume 2: Landcover classes and plant associations