Early Post-Fire Biomass Accumulation Following the Kenow Wildland Fire, Waterton Lakes National Park, Canada

Abstract:

Warming climates have caused increased frequency and severity of montane wildland fires, resulting in a departure from historical ecosystem succession. As global climate continues to change, the future of forest resiliency remains uncertain as forests regenerate in conditions dissimilar to those of the burnt forest. Post-fire montane forests are at risk of contracting tree lines in valley bottoms, transitioning to grasslands, and changes in species composition.

The Kenow wildland fire (2017) was a high severity fire that burned a total of 35,000 ha, including 38% of Waterton Lakes National Park, Canada. In 2018, 31 field plots were established in a riparian region of the Cameron Valley, these sites were visited bi-weekly throughout September 2018 and the summer of 2019. In the summer of 2020, an additional 29 plots were established in an upland, sloped region to the south of the riparian site. Vegetation within the plots was photographed, measured, and inventoried for species. Field data was used for validation of multi-spectral lidar data collected in the fall of 2017 and summers of 2018 to 2020. Lidar data was used to assess the physical structure of regenerating vegetation and spectral indices such as pseudo-normalized difference vegetation index (pseudo-NDVI) and normalized burn ratios (NBR). Data was used to determine the rate of vegetation regeneration and amount of carbon being stored in the Cameron Valley. Initial results indicate that multi-spectral lidar can effectively quantify initial post-fire regeneration as lidar derived pseudo-NDVI indices correlate (R²=0.70) with green colour composite (GCC) images taken in the field to determine vegetation cover. The Cameron Valley has experienced rapid herbaceous vegetation regeneration over the first three years post-fire. Field data indicates that the annual increase in vegetation cover within a riparian study site is approximately 12.35% annually from 2018 to 2020, with higher rates of accumulation in regions of increased moisture availability. Rapid herbaceous regeneration and the presence of lodgepole pine seedlings in upland areas indicates that this montane ecosystem is showing signs of resiliency to wildland fires despite changing climate conditions.