16-1 Characterizing Wildfire-Induced Alteration to Soil Hydraulic Properties Across a Gradient of Burn Severity in Three Distinct Ecosystems, British Columbia, Canada

Session: Wildland Fire: An Agent of Geomorphic, Ecologic, and Societal Change

Presenting Author:

Jorrin Lenton

Authors:

Lenton, Jorrin Christopher¹, Murphy, Brendan Patrick², Millard, Thomas H.³

Abstract:

The recent increase in wildfire activity and associated hydrogeomorphic hazards has presented the post-wildfire research community with both critical challenges and new opportunities. Escalating risks have increased research efforts and broader recognition of this nascent field, with emerging studies consistently highlighting a persistent need for methodological standardization — particularly in the methods used to determine soil burn severity and soil hydraulic properties (SHPs). This need is amplified as high-severity wildfires expand into less studied biogeoclimatic regions (e.g., the Pacific Northwest). To ensure robust and interpretable soil burn severity assessments over time and across studies, a systematic evaluation of study design, measurement protocols, and analytical frameworks is needed. Here, we present a comparative assessment of some commonly used methods for measuring SHPs and soil water repellency (SWR). We collected co-located datasets across a burn severity gradient, including unburned controls, from three recent wildfires in distinct British Columbia ecosystems: Dry Mixed Conifer, Coastal Temperate Rainforest, and Boreal Forest. Each site was centered on a 30-m dNBR grid-cell, with burn severity ground-truthed using standard USFS protocols (SBS and CBI). We then collected soil cores to analyze physical properties (D50, p_b, SOM, VWC), conducted mini disk infiltrometer measurements at different tensions and on different substrates, and assessed SWR using the WDPT and MED tests to a depth of 10-cm. Our results revealed trends in soil properties with burn severity that were highly dependent on the ecosystem. Consistent with previous work, we found that SHPs and SWR decreased as dNBR increased in the Dry Mixed Conifer wildfire. In the Coastal Temperate Rainforest wildfire, SHPs decreased more rapidly with increasing dNBR, however, droplet tests at the mineral soil surface showed similarly high SWR for all sites. Finally, in the Northern Boreal wildfire, no significant changes in SHPs or SWR on mineral soil were observed with dNBR, which was interpreted to reflect thermal buffering by the sphagnum mosses in the ecosystem. Overall, our findings revealed distinct trends in SHPs, SWR, and physical properties across the three ecosystems. We also identified significant discrepancies among some commonly used methods for assessing post-fire runoff potential, highlighting that ecosystem-specific considerations may be necessary for soil burn severity assessments.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-4336

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