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dc.contributor.authorO'Donnell, Jonathan A.
dc.date.accessioned2018-08-07T00:59:19Z
dc.date.available2018-08-07T00:59:19Z
dc.date.issued2010
dc.identifier.urihttp://hdl.handle.net/11122/9063
dc.descriptionThesis (Ph.D.) University of Alaska Fairbanks, 2010
dc.description.abstractHigh-latitude regions store large quantities of organic carbon (C) in permafrost soils and peatlands, accounting for nearly half of the global belowground C pool. Projected climate warming over the next century will likely drive widespread thawing of near-surface permafrost and mobilization of soil C from deep soil horizons. However, the processes controlling soil C accumulation and loss following permafrost thaw are not well understood. To improve our understanding of these processes, I examined the effects of permafrost thaw on soil C dynamics in forested upland and peatland ecosystems of Alaska's boreal region. In upland forests, soil C accumulation and loss was governed by the complex interaction of wildfire and permafrost. Fluctuations in active layer depth across stand age and fire cycles determined the proportion of soil C in frozen or unfrozen soil, and in turn, the vulnerability of soil C to decomposition. Under present-day climate conditions, the presence of near-surface permafrost aids C stabilization through the upward movement of the permafrost table with post-fire ecosystem recovery. However, sensitivity analyses suggest that projected increases in air temperature and fire severity will accelerate permafrost thaw and soil C loss from deep mineral horizons. In the lowlands, permafrost thaw and collapse-scar bog formation resulted in the dramatic redistribution of soil water, modifying soil thermal and C dynamics. Water impoundment in collapse-scar bogs enhanced soil C accumulation in shallow peat horizons, while allowing for high rates of soil C loss from deep inundated peat horizons. Accumulation rates at the surface were not sufficient to balance deep C losses, resulting in a net loss of 26 g C m -2 y-1 from the entire peat column during the 3000 years following thaw. Findings from these studies highlight the vulnerability of soil C in Alaska's boreal region to future climate warming and permafrost thaw. As a result, permafrost thaw and soil C release from boreal soils to the atmosphere should function as a positive feedback to the climate system.
dc.subjectEcology
dc.titleThe Effects Of Permafrost Degradation On Soil Carbon Dynamics In Alaska's Boreal Region
dc.typeThesis
dc.type.degreephd
dc.identifier.departmentBiology and Wildlife Dept.
dc.contributor.chairMcGuire, David
refterms.dateFOA2020-03-05T16:29:57Z


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