Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Geography & Environmental Studies

Program Name/Specialization

Environmental Science

Faculty/School

Faculty of Science

First Advisor

William L Quinton

Advisor Role

Supervisor

Second Advisor

Fereidoun Rezanezhad

Advisor Role

Co-supervisor

Abstract

Under current climate change, summer season in the boreal regions of Canada is becoming increasingly warmer and drier. This shift is driving increases in the frequency and intensity of naturally occurring wildfires and allowing access to areas not normally susceptible to fire such as wetlands. In peatland areas, these increasingly large fires can create complex burn scars, which contain a wide variety of different burn severities across different landcover types. This variety calls for a greater understanding of how varying fire intensity affects the hydro physical, chemical, and thermal characteristics of boreal peat. This study aims to deepen that understanding by examining the variety of burn severity types generated in the 2022 wildfire that burned across the plateau-wetland mosaic of the Scotty Creek basin, 50 km south of Fort Simpson, Northwest Territories. This was achieved through the selection, monitoring, sampling and testing of unburned, low burn severity and high burn severity plateau plots along with unburned and low burn severity collapse scar wetland locations during the 2023, 2024 and 2025 field seasons. Near surface volumetric soil moisture on plateaus was found to increase by 3% in low burn severity areas and 15% in high burn severity areas for the 2024 thaw season, while low burn severity collapse scar wetlands saw decreases of 12% when compared to unburned areas. On plateaus this pattern was primarily attributed to the reduction in hydraulic mobility brought about by a reduction in the active porosity of the peat, as illustrated by increased solute breakthrough intervals in burned peat samples. In collapse scar wetlands, near surface soil moisture reductions were accorded to the preferential burning of well drained areas of the wetland rather than the direct effects of the burn. Concentrations of dissolved organic carbon (DOC) and total nitrogen (TN) produced under leaching conditions were not affected by burn severity for either of the two landcover types. Due to their close linkage with moisture, spatial patterns in thermal conductivity and volumetric heat capacity generally mirrored those of soil 2 moisture, with near surface thermal conductivity at low and high severity plateau sites being 0.09 W m-1 K-1 and 0.11 W m-1 K-1 greater than unburned plots respectively. These changes led to increases in mid-season plateau thaw depths as burn severity increased, with low severity plots thawing 9.5 cm and high severity plots 16.1 cm deeper than unburned areas by the end of June 2024. Discontinuous taliks were more prevalent at the unburned and low severity plots than high severity plots, however these were suspected to predate the fire. End of season thaw depths for non-talik points were near equal at approximately 68 cm for the three burn types, with high severity plots overall presenting a much more uniform thaw depth than the other two categories. As burn severity increases, increases in peat plateau soil moisture and thermal conductivity are expected to combine with canopy loss and albedo reduction to increase enthalpy in the suprapermafrost layer of plateaus, accelerating permafrost thaw and landscape change within the Scotty Creek basin.

Convocation Year

2026

Convocation Season

Fall

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