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

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Decomposition is a critical process in global carbon cycling. During decomposition, leaf and fine root litter may undergo a later, relatively slow phase; past long-term experiments indicate this phase occurs, but whether it is a general phenomenon has not been examined. Data from Long-term Intersite Decomposition Experiment Team, representing 27 sites and nine litter types (for a total of 234 cases) was used to test the frequency of this later, slow phase of decomposition. Litter mass remaining after up to 10 years of decomposition was fit to models that included (dual exponential and asymptotic) or excluded (single exponential) a slow phase. The resultant regression equations were evaluated for goodness of fit...
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Modeling the biology of forest ecosystems has been devoted to a combination of theoretical and empirical approaches representing the function of a forest ecosystem generally within an undefined spatial context. Moving to a large spatial context will require the use of theoretical representations of critical ecosystem functions that can be represented on an individual cell basis. A Spatial Alaskan Forest Ecosystem Dynamics (SAFED) model was developed that is based on the nitrogen productivity concept for forest growth, litter fall quality, and microbial efficiency for forest floor decomposition. Climate and ecosystem disturbances were handled as restricted stochastic [random] processes. The restriction was based...
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Herbivores transform landscapes and affect succession via selective foraging that alters vegetation composition. In the boreal forest, mammalian herbivores, mainly moose, facilitate a shift toward the dominance of heavily defended species over time, such as white spruce. The effects of moose herbivory are intensified by the browsing of snowshoe hares. However, unlike moose, snowshoe hares also browse seedlings of white spruce. We quantified herbivory by snowshoe hares on white spruce along the Tanana River, interior Alaska, and assessed the effects on white spruce demography via two different herbivore exclosure experiments. We hypothesized that both experiments would show reduced plant density and height growth...
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1.?Ecosystem properties may be determined by the number of different species or groups of species in a community, the identity of those groups, and their relative abundance. The mass ratio theory predicts that the effect of species or groups of species on ecosystem properties will be dependent on their proportional abundance in a community. 2.?Single plant functional groups (graminoids, legumes, non-leguminous forbs) were removed from a natural grassland in northern Canada to examine the role of group identity in determining both ecosystem properties and biomass compensation by remaining species. Removals were conducted across two different environmental treatments (fertilization and fungicide) to examine the context...
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High-latitude ecosystems are exposed to more pronounced warming effects than other parts of the globe. We develop a technique to monitor ecological changes in a way that distinguishes climate influences from disturbances. In this study, we account for climatic influences on Alaskan boreal forest performance with a data-driven model. We defined ecosystem performance anomalies (EPA) using the residuals of the model and made annual maps of EPA. Most areas (88%) did not have anomalous ecosystem performance for at least 6 of 8 years between 1996 and 2004. Areas with underperforming EPA (10%) often indicate areas associated with recent fires and areas of possible insect infestation or drying soil related to permafrost...
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One expected response to climate warming in the Arctic is an increase in the abundance and extent of shrubs in tundra areas. Repeat photography shows that there has been an increase in shrub cover over the past 50 years in northern Alaska. Using 202 pairs of old and new oblique aerial photographs, we have found that across this region spanning 620 km east to west and 350 km north to south, alder, willow, and dwarf birch have been increasing, with the change most easily detected on hill slopes and valley bottoms. Plot and remote sensing studies from the same region using the normalized difference vegetation index are consistent with the photographic results and indicate that the smaller shrubs between valleys are...
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...
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Our research on the herbaceous understory vegetation in the Kluane region, Yukon, has focused on the structure and function of natural forest understory and grassland communities. The research has involved two long-term projects. The first investigated fertilizer addition and mammalian herbivore exclosure in understory vegetation over a 20-year period and showed that nutrient availability, and not herbivory, controlled herbaceous biomass. Fertilization increased the amount and nutrient content of vegetation, but 13 species were lost, whereas natural levels of mammalian herbivory rarely affected this vegetation or its diversity. The second study investigated how removing plant functional groups from a grassland influences...
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Extrapolating energy fluxes between the ground surface and the atmospheric boundary layer from point-based measurements to spatially explicit landscape estimation is critical to understand and quantify the energy balance components and exchanges in the hydrosphere, atmosphere, and biosphere. This information is difficult to quantify and are often lacking. Using a Landsat image (acquired on 5 August 2004), the flux measurements from three eddy covariance flux towers (a 1987 burn, a 1999 burn, and an unburned control site) and a customized satellite-based surface energy balance model of Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC), we estimated net radiation, sensible heat flux...
Bull trout home to tributary streams in headwater areas for spawning. Site use can be influenced by habitat quality, including physical features such as stream flow, intergravel flow, hyporheic exchange, stream and intergravel-water chemistry, temperature and cover. These variables can influence survival and growth during incubation, however, the effect on bull trout spawning and incubation success is not known. I used three studies to examine the importance of spawning habitat for bull trout spawning in northern B.C. My results show that temperature is likely a key determinant of site use at potential spawning sites as well as incubation success in northern environments. Bull trout growth and yolk utilization were...
map background search result map search result map Herbaceous community structure and function in the Kluane region Integrating modelling and remote sensing to identify ecosystem performance anomalies in the boreal forest, Yukon River Basin, Alaska Ecosystem properties determined by plant functional group identity Carbon Stores and Biogeochemical Properties of Soils under Black Spruce Forest, Alaska Spatially explicit surface energy budget and partitioning with remote sensing and flux measurements in a boreal region of Interior Alaska The evidence for shrub expansion in Northern Alaska and the Pan-Arctic Abundance of microbial genes associated with nitrogen cycling as indices of biogeochemical process rates across a vegetation gradient in Alaska Distribution, persistence, and hydrologic characteristics of salmon spawning habitats in clearwater side channels of the Matanuska River, Southcentral Alaska The Distribution of Shrubs used by Indigenous Peoples within the Forest-Tundra Ecotone in Canada The role of soil drainage class in carbon dioxide exchange and decomposition in boreal black spruce (Picea mariana) forest stands Vertebrate community structure in the Boreal forest: Modelling the effects of trophic interaction Climate Variation and Disturbance Regime Affect Stand Composition and Structure of the Boreal Forests in Southwest Yukon of Canada Boreal forest ecosystem dynamics. I. A new spatial model Decadal and long-term boreal soil carbon and nitrogen sequestration rates across a variety of ecosystems Stage-dependent effects of browsing by snowshoe hares on successional dynamics in a boreal forest ecosystem The Distribution of Shrubs used by Indigenous Peoples within the Forest-Tundra Ecotone in Canada Decadal and long-term boreal soil carbon and nitrogen sequestration rates across a variety of ecosystems Distribution, persistence, and hydrologic characteristics of salmon spawning habitats in clearwater side channels of the Matanuska River, Southcentral Alaska Herbaceous community structure and function in the Kluane region The role of soil drainage class in carbon dioxide exchange and decomposition in boreal black spruce (Picea mariana) forest stands Spatially explicit surface energy budget and partitioning with remote sensing and flux measurements in a boreal region of Interior Alaska Climate Variation and Disturbance Regime Affect Stand Composition and Structure of the Boreal Forests in Southwest Yukon of Canada Ecosystem properties determined by plant functional group identity Stage-dependent effects of browsing by snowshoe hares on successional dynamics in a boreal forest ecosystem Boreal forest ecosystem dynamics. I. A new spatial model Carbon Stores and Biogeochemical Properties of Soils under Black Spruce Forest, Alaska Abundance of microbial genes associated with nitrogen cycling as indices of biogeochemical process rates across a vegetation gradient in Alaska Vertebrate community structure in the Boreal forest: Modelling the effects of trophic interaction The evidence for shrub expansion in Northern Alaska and the Pan-Arctic Integrating modelling and remote sensing to identify ecosystem performance anomalies in the boreal forest, Yukon River Basin, Alaska