Impacts of wildfire on subcanopy energy balance, thermal regime, and permafrost stability in peat plateaus at Scotty Creek, Canada

• Main Author: Auclair, Maude
• Format: Text
• Language: English
• Published: Scholars Commons @ Laurier 2024
• Subjects: Permafrost thaw; wildfire; energy balance; talik; peatlands; Environmental Sciences; Peat; Peat plateau; permafrost; Talik
• Online Access: https://scholars.wlu.ca/etd/2682; https://scholars.wlu.ca/context/etd/article/3841/viewcontent/AuclairThesis_Final.pdf

The stability of permafrost in peatland-dominated regions of northwestern Canada is compromised by ongoing climate warming and increased wildfire activity. This study examines an 8-year record of changes to the surface and subsurface properties of a peat plateau following a low-severity wildfire that occurred in 2014 in a region of thawing, discontinuous permafrost. This is accomplished by comparing the burned portion of a peat plateau to two unburned control sites, one of which is the unburned portion of the same plateau that was affected by the fire. Net radiation was not significantly different one year following the wildfire but became increasingly larger at the Burn site in the following years, supplying a surplus of energy available for ground thaw. This increase in energy inputs coincided with the gradual collapse of the remaining standing dead trees, which is supported by a trend of increasing wind speeds. Soil moisture decreased at the Burn in the first 4 years post-fire before returning and maintaining similar moisture content as the adjacent control site. Ground temperatures were consistently warmer in the summer and colder in the winter compared to the adjacent control site. The cooler winter ground temperatures at the burn were attributed to the snowpack being thinner and denser, and thus less insulative, allowing for more energy to escape the subsurface during the winter seasons. This was not enough to offset the increased inputs of energy endured at the Burn over the summer seasons, as the depth to permafrost increased significantly over the study period and no trend was found for the control sites. The average annual rate of permafrost thaw was 9.6 cm/year at the Burn, compared to 5.6 cm/year at the nearby adjacent control site. The most notable finding was a near-continuous talik (perennially frozen) layer beneath the Burn, a feature known to further accelerate permafrost thaw. The thinner active layer at the Burn required less energy to thaw, leaving more energy available to drive other ...