| Summary: | Thesis (M.S.) University of Alaska Fairbanks, 2011 Northern peatlands have been a long-term sink for atmospheric CO₂, and have had a net cooling effect on global climate for the last 8,000 to 11,000 years. Across Alaska, peatlands face increased effects of climate change through hydrologic disturbance, both drying and flooding, and these conditions alter the ability of peatlands to accumulate carbon. Here, I examined the influence of changing hydrology in a moderate rich fen and a bog located in the discontinuous permafrost zone of interior Alaska. In both sites, I quantified how changing hydrology affected vegetation composition and ecosystem carbon uptake. At the fen, drying via a lowered water table treatment caused larger changes in vegetation composition and primary productivity than flooding via a raised water table treatment. In the bog, an area of recent permafrost thaw (collapse scar) had increased rates of understory net primary production and gross primary production, relative to an adjacent but older collapse scar and the surrounding permafrost plateau. Together, results from these studies highlight possible community responses to projected change in water availability, whether through drying or flooding, and demonstrate initial mechanisms for community responses altering ecosystem processes. Introduction -- Shifts in plant community structure and productivity in two Alaskan boreal peatlands in response to hydrologic disturbance -- Environmental limitations and plant community contributions to gross primary productivity in Alaskan boreal peatlands responding to climate change -- Conclusion.
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