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Long Term Effects of Wildfire on Permafrost Stability and Carbon Cycling in Northern Peatlands

  • Author / Creator
    Gibson, C M
  • Changing fire dynamics and increasing global temperatures are causing changes to the fire regime and permafrost stability in the Arctic. Models have separately predicted the widespread thawing of permafrost and increasing magnitude and intensity of wildfires over the next century. However, while it is evident that wildfire and permafrost are both dominant controls on carbon dynamics in the boreal, less is known about the potential effects of wildfire to cause increased permafrost thaw and to affect soil carbon stocks. To assess the role of wildfire in future permafrost stability and carbon storage in permafrost peatlands of northwestern Canada, I addressed the following questions; 1) to what extent does fire accelerate permafrost thaw in discontinuous permafrost regions and 2) what is the magnitude of carbon released from depth as a result of fire-induced permafrost thaw on peat plateaus. This research was conducted at a variety of sites located within the Northwest Territories that burned 2,3,9,14,15,21,33,40 and 48 years ago, and six, nearby unburned sites. Field data was complemented with the use of remotely sensed data to determine the extent of fire-induced permafrost thaw. Soil respiration was measured on a subset of these sites. The results of these studies, summarized in this thesis, find that wildfire destabilizes the post-fire soil thermal regime of peat plateaus manifested by deeper active layers and widespread formation of taliks, persisting for up to 30 with the most pronounced effect being 10-20 following fire. This also appears to result in ~3 times the rate of recent thermokarst formation, making wildfire responsible for ~25% of permafrost thaw in the past 30 years. As a result of fire induced deepening of the active layer and increased soil temperatures, soil respiration at depth was stimulated, representing a nearly four times greater respiration of old compared to unburned sites. Surprisingly though, I find that this is not enough to offset the importance of surface labile carbon pools, to soil respiration, that are burned off during the fire event, despite the mobilization and release of deep, old, previously stored carbon. This thesis concludes by highlighting the importance of wildfire as a driver of permafrost stability and old carbon storage capabilities and emphasizes the importance of it in global permafrost and carbon cycling models.

  • Subjects / Keywords
  • Graduation date
    2017-11
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R3BG2HQ7J
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Master's
  • Department
    • Department of Renewable Resources
  • Specialization
    • Forest Biology and Management
  • Supervisor / co-supervisor and their department(s)
    • Flannigan, Mike (Renewable Resources)
    • Olefeldt, David (Renewable Resources)
  • Examining committee members and their departments
    • Dyck, Miles (Renewable Resources)
    • Thompson, Dan (Canadian Forest Service)