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

• Main Author: Gibson, C M
• Other Authors: Flannigan, Mike (Renewable Resources), Olefeldt, David (Renewable Resources), Thompson, Dan (Canadian Forest Service), Dyck, Miles (Renewable Resources)
• Format: Thesis
• Language: English
• Published: University of Alberta. Department of Renewable Resources. 2017
• Subjects: envir; geo; Arctic; Canada; Northwest Territories; Peat; permafrost; Thermokarst
• Online Access: http://hdl.handle.net/10402/era.44201

Specialization: Forest Biology and Management Degree: Master of Science Abstract: 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 ...