The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region
Dissertation (Ph.D.) University of Alaska Fairbanks, 2010 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 th...
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ftunivalaska:oai:scholarworks.alaska.edu:11122/8500 2023-05-15T17:55:22+02:00 The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region O'Donnell, Jonathan A. 2010-12 http://hdl.handle.net/11122/8500 en_US eng http://hdl.handle.net/11122/8500 Biology and Wildlife Department Permafrost Carbon content Alaska Frozen ground Soils Taigas Ecology Black spruce Fire ecology Taiga ecology Permafrost forest ecology Dissertation phd 2010 ftunivalaska 2023-02-23T21:37:04Z Dissertation (Ph.D.) University of Alaska Fairbanks, 2010 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 ... Doctoral or Postdoctoral Thesis permafrost taiga Alaska University of Alaska: ScholarWorks@UA Fairbanks |
institution |
Open Polar |
collection |
University of Alaska: ScholarWorks@UA |
op_collection_id |
ftunivalaska |
language |
English |
topic |
Permafrost Carbon content Alaska Frozen ground Soils Taigas Ecology Black spruce Fire ecology Taiga ecology Permafrost forest ecology |
spellingShingle |
Permafrost Carbon content Alaska Frozen ground Soils Taigas Ecology Black spruce Fire ecology Taiga ecology Permafrost forest ecology O'Donnell, Jonathan A. The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region |
topic_facet |
Permafrost Carbon content Alaska Frozen ground Soils Taigas Ecology Black spruce Fire ecology Taiga ecology Permafrost forest ecology |
description |
Dissertation (Ph.D.) University of Alaska Fairbanks, 2010 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 ... |
format |
Doctoral or Postdoctoral Thesis |
author |
O'Donnell, Jonathan A. |
author_facet |
O'Donnell, Jonathan A. |
author_sort |
O'Donnell, Jonathan A. |
title |
The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region |
title_short |
The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region |
title_full |
The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region |
title_fullStr |
The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region |
title_full_unstemmed |
The effects of permafrost degradation on soil carbon dynamics in Alaska's boreal region |
title_sort |
effects of permafrost degradation on soil carbon dynamics in alaska's boreal region |
publishDate |
2010 |
url |
http://hdl.handle.net/11122/8500 |
geographic |
Fairbanks |
geographic_facet |
Fairbanks |
genre |
permafrost taiga Alaska |
genre_facet |
permafrost taiga Alaska |
op_relation |
http://hdl.handle.net/11122/8500 Biology and Wildlife Department |
_version_ |
1766163292108095488 |