The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region
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 | Dissertation (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 | Dissertation | en_US |
dc.type.degree | phd | en_US |
dc.identifier.department | Biology and Wildlife Department | en_US |
refterms.dateFOA | 2020-03-05T15:31:08Z |
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Biological Sciences
Includes WIldlife Biology and other Biological Sciences. For Marine Biology see the Marine Sciences collection. -
Theses supervised by AKCFWRU