Thesis Defences
Jorrin Lenton
Department of Earth Sciences
"Characterizing Wildfire-Induced Alteration to Soil Hydraulic Properties across a Gradient of Burn Severity in Three Distinct Ecosystems, British Columbia, Canada".
Chair: Dr. Sergio Sepulveda, Earth Sciences
Supervisor: Dr. Brendan Murphy, School of Environmental Science
Commitee Member: Dr. Jessica Pilarczyk, School of Environmental Science
Committee Member: Dr. Jesse Hahm, Department of Geography
Committee Member: Tom Millard, BC Ministry of Forests
Examiner: Dr. Sophie Wilkinson, School of Resource and Environmental Management
Date: Friday, December 12, 2025
Time: 9:30AM PST
Location: Library Thesis Defence Room 2020 and via Zoom: https://sfu.zoom.us/j/89402618742?pwd=vnWPotrwZvkJg8bRiEN7L2qU4W0I3l.1
Abstract:
The recent increase in wildfire activity and associated hydrogeomorphic hazards presents both critical challenges and new opportunities for the post-wildfire research community. Escalating risks have intensified research efforts, yet methodological standardization remains a persistent need, particularly for assessing soil burn severity and soil hydraulic properties required for post-fire debris flow hazard assessments. This need is increasingly urgent as high-severity wildfires expand into understudied regions such as the Pacific Northwest. Ensuring consistent and interpretable soil burn severity assessments requires a systematic evaluation of study design, measurement protocols, and conceptual frameworks. This thesis presents a comparative assessment of commonly used methods for quantifying soil hydraulic properties, soil water repellency, and soil physical properties across a gradient of burn severity, in three distinct pyro-ecoregions in British Columbia, Canada. Our findings reveal pyro-ecoregion specific differences across all measured variables, reflecting the unique traits of each pyro-ecoregion. The Dry Mixed Coniferous (DMC) and Coastal Temperate Rainforest (CTR) pyro-ecoregions each exhibited exponential declines in infiltration capacity with increasing burn severity, accompanied by varying trends of fire-induced soil water repellency. In contrast, the Northern Boreal Spruce pyro-ecoregion soil hydraulic properties did not decrease with increasing burn severity due to its thick sphagnum moss layer and high soil moisture. Of the three wildfires assessed, only the DMC wildfire produced post-fire debris flows, which were driven by reduced infiltration, loss of vegetative cover, and high-intensity rainfall. Although the CTR wildfire experienced reduced infiltration, the other conditions required to initiate post-fire debris flows were not met. These results highlight the importance of understanding the interactions among soil hydraulic properties, soil water repellency, soil physical properties, vegetation, and rainfall intensity. With climate change driving more severe wildfires and intensifying rainfall, understanding post-fire debris flow initiation from a process-based, pyro-ecoregion specific perspective is crucial, as ecosystem responses and associated hazards are likely to evolve and intensify under future climate scenarios.
For more information or any questions, please contact the Earth Sciences Graduate Program Assistant at: easc_grad_secretary@sfu.ca.