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The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region

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dc.contributor.author O'Donnell, Jonathan A.
dc.date.accessioned 2018-06-04T20:55:14Z
dc.date.available 2018-06-04T20:55:14Z
dc.date.issued 2010-12
dc.identifier.uri http://hdl.handle.net/11122/8500
dc.description Thesis (Ph.D.) University of Alaska Fairbanks, 2010 en_US
dc.description.abstract High-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. en_US
dc.language.iso en_US en_US
dc.subject Permafrost en_US
dc.subject Carbon content en_US
dc.subject Alaska en_US
dc.subject Frozen ground en_US
dc.subject Soils en_US
dc.subject Taigas en_US
dc.subject Ecology en_US
dc.subject Black spruce en_US
dc.subject Fire ecology en_US
dc.subject Taiga ecology en_US
dc.subject Permafrost forest ecology en_US
dc.title The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region en_US
dc.type Thesis en_US
dc.type.degree phd en_US
dc.identifier.department Biology and Wildlife Department en_US


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