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To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate ~600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing season temperature...
In the boreal biome, fire is the major disturbance agent affecting ecosystem change, and fire dynamics will likely change in response to climatic warming. We modified a spatially explicit model of Alaskan subarctic treeline dynamics (ALFRESCO) to simulate boreal vegetation dynamics in interior Alaska. The model is used to investigate the role of black spruce ecosystems in the fire regime of interior Alaska boreal forest. Model simulations revealed that vegetation shifts caused substantial changes to the fire regime. The number of fires and the total area burned increased as black spruce forest became an increasingly dominant component of the landscape. The most significant impact of adding black spruce to the model...
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The response of terrestrial ecosystems to climate warming has important implications to potential feedbacks to climate. The interactions between topography, climate, and disturbance could alter recruitment patterns to reduce or offset current predicted positive feedbacks to warming at high latitudes. In northern Alaska the Brooks Range poses a complex environmental and ecological barrier to species migration. We use a spatially explicit model (ALFRESCO) to simulate the transient response of subarctic vegetation to climatic warming in the Kobuk/Noatak River Valley (200 x 400 km) in northwest Alaska. The model simulations showed that a significantly warmer (+6 degrees C) summer climate would cause expansion of forest...
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Abstract: In this article we extend the theory of community prediction by presenting seven hypotheses for predicting community structure in a directionally changing world. The first three address well-studied community responses to environmental and ecological change: ecological communities are most likely to exhibit threshold changes in structure when perturbations cause large changes in limiting soil or sediment resources, dominant or keystone species, or attributes of disturbance regime that influence community recruitment. Four additional hypotheses address social-ecological interactions and apply to both ecological communities and social-ecological systems. Human responsiveness to short-term and local costs...
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To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate approximately 600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing...
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We used a combination of surveys of natural vegetation and seed-sowing and seedling transplant experiments to determine the relative importance of competition and microenvironmental modification as mechanisms by which understory vegetation influences the establishment of tree seedlings in an Alaskan postfire boreal forest. Seedlings of white spruce (Picea glauca) and paper birch (Betula papyrifera) became established more frequently than expected in patches that were dominated by horsetail (Equisetum arvense), and less frequently than expected in patches of bluestem (Calamagrostis canadensis) and other vegetation. Similarly, birch and spruce, whether sown directly or transplanted as seedlings into horsetail-dominated...
map background search result map search result map Land cover disturbances and feedbacks to the climate system in Canada and Alaska Modeling the influence of topographic barriers on treeline advance at the forest-tundra ecotone in northwestern Alaska Changes in vegetation in northern Alaska under scenarios of climate change, 2003-2100: implications for climate feedbacks Human Influences on Wildfire in Alaska from 1988 through 2005: An Analysis of the Spatial Patterns of Human Impacts Plant Toxicity, Adaptive Herbivory, and Plant Community Dynamics Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse; interactions between fire and thermokarst Differential effects of competition or microenvironment on boreal tree seedling establishment after fire Scale-dependent environmental controls over species composition in Alaskan black spruce communities Substrate limitations to microbial activity in taiga forest floors Plant Community Composition as a Predictor of Regional Soil Carbon Storage in Alaskan Boreal Black Spruce Ecosystems Sustainability of Arctic Communities: An Interdisciplinary Collaboration of Researchers and Local Knowledge Holders Modeling the Impact of Black Spruce on the Fire Regime of Alaskan Boreal Forest Linking western and traditional ways of knowing as a basis for management of humpback whitefish in Interior Alaska Alaska's Changing Boreal Forest Herbivory-Mediated Responses of Selected Boreal Forests to Climatic Change Plant Toxicity, Adaptive Herbivory, and Plant Community Dynamics Substrate limitations to microbial activity in taiga forest floors Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse; interactions between fire and thermokarst Differential effects of competition or microenvironment on boreal tree seedling establishment after fire Sustainability of Arctic Communities: An Interdisciplinary Collaboration of Researchers and Local Knowledge Holders Modeling the Impact of Black Spruce on the Fire Regime of Alaskan Boreal Forest Scale-dependent environmental controls over species composition in Alaskan black spruce communities Modeling the influence of topographic barriers on treeline advance at the forest-tundra ecotone in northwestern Alaska Linking western and traditional ways of knowing as a basis for management of humpback whitefish in Interior Alaska Human Influences on Wildfire in Alaska from 1988 through 2005: An Analysis of the Spatial Patterns of Human Impacts Alaska's Changing Boreal Forest Herbivory-Mediated Responses of Selected Boreal Forests to Climatic Change Changes in vegetation in northern Alaska under scenarios of climate change, 2003-2100: implications for climate feedbacks Plant Community Composition as a Predictor of Regional Soil Carbon Storage in Alaskan Boreal Black Spruce Ecosystems Land cover disturbances and feedbacks to the climate system in Canada and Alaska