Skip to main content
Advanced Search

Filters: Tags: Monitoring 1-Changes in Plant and Animal Distribution: Ecosystems (X)

591 results (14ms)   

View Results as: JSON ATOM CSV
thumbnail
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...
thumbnail
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...
thumbnail
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...
Alluvial floodplains are unique geomorphic features of lotic systems that are characterized by a shifting morphology in three spatial dimensions. This spatial and temporal heterogeneity is thought to explain why these aquatic-terrestrial ecotones are the most species-rich habitats on the terrestrial portions of earth. Many factors and processes influencing these high levels of species richness remain unstudied, however. Regional factors, such as regional species pools, and local factors, such as groundwater-surface water exchange have received little consideration as factors controlling local species richness on floodplains. Additionally, the conservation of these habitats and the biodiversity they support remains...
At northern high latitudes, biosphere responses to and interactions with climate warming are expected to be significant during the 21st century. Most predictions of climate?biosphere interactions rely on experiments and observations in contemporary landscapes, e.g., modern distributions of vegetation types and their structural features are used to delimit potential biosphere?atmosphere feedbacks. Paleorecords look beyond the present to examine vegetation configurations under climatic regimes that approximate future scenarios. To enhance the knowledge of arctic and subarctic ecosystems under varying climatic conditions, we analyzed pollen and macrofossil data from Beringia (northeast Siberia, Alaska, and northwest...
The spatial patterns of trees and shrubs within the forest-tundra ecotones in the Mealy Mountains, Newfoundland and Labrador, and in the Ruby Ranges, Yukon Territory were characterized using spatial pattern analysis. The processes influencing the recruitment of juvenile trees into the adult population and how they may facilitate or hinder infilling and advance at Canada's treeline were inferred. In Labrador, trees were generally aggregated; recruitment into the adult population could be regulated by facilitation. Conversely, in the Yukon, trees were generally regularly distributed, possibly influenced by competition. At both sites, trees were generally independent of shrub cover. The spatial arrangement of trees...
This chapter outlines the broader scope of dendroclimatic research that has been published to date for far northern areas. It provides a glimpse into the broader context for the TRL-LDEO research. Tree-ring research in Alaska and adjacent northwestern Canada by Juday (2011) and colleagues using ringwidth, MXD, and isotopic records has focused on the relatively closed canopy interior boreal forests, including those in the Bonanza Creek watershed near Fairbanks. Their analyses have clearly demonstrated that the unprecedented, rapid warming in Alaska over recent decades, along with coincident temperature-induced drought stress and intensified insect activity, have resulted in large-scale tree mortality and growth declines...
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...
map background search result map search result map Fungal endophyte infection in an alpine meadow: Testing the mutualism theory Indirect and Long-Term Effects of Fire on the Boreal Forest Carbon Budget 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 Boreal forest ecosystem dynamics. II. Application of the model to four vegetation types in interior Alaska Latitudinal gradient of spruce forest understory and tundra phenology in Alaska as observed from satellite and ground-based data Fungal endophyte infection in an alpine meadow: Testing the mutualism theory Denali National Park and Preserve Landcover Mapping Project Volume 2: Landcover classes and plant associations Exploring ecological changes in Cook Inlet beluga whale habitat though traditional and local ecological knowledge of contributing factors for population decline Indirect and Long-Term Effects of Fire on the Boreal Forest Carbon Budget Boreal forest ecosystem dynamics. II. Application of the model to four vegetation types in interior Alaska Latitudinal gradient of spruce forest understory and tundra phenology in Alaska as observed from satellite and ground-based data