Post-Fire Mortality and Fire Resistance of Old-growth Forests in the Kootenay Lake Timber Supply Area, British Columbia

In an era of climate change, how different tree species in old forests are disturbed by wildfires, and what fire resistance they have are important questions. Old-growth forests are significant because they maintain local biodiversity and ecosystem sustainability, and also contribute to the local economy through timber harvesting. In this research, by analyzing Landsat-8 images of 20 fires from 2016 to 2020, the disturbance data of the forest before and after the fire can be generated. Data from B.C. government and Landsat-8 images are used to analyze fire resistance and recovery of old-growth forests in the Kootenay Lake Timber Supply Area (TSA) by calculating NBR (Normalized burn ratio) and NDVI (Normalized Difference Vegetation Index). Five common tree species (western larch, Douglas fir, western hemlock, Engelmann spruce, subalpine fir) near Kootenay Lake TSA were selected for fire resistance comparison at different burn severities (high, medium, low). The result verified that different tree species have different fire resistance and mortality when facing different burn severities. Western larch and Douglas fir have high fire resistance. Western hemlock has relatively low fire resistance. Engelmann spruce and Subalpine fir have very low fire resistance. This result is highly similar to the report provided by USDA. However, due to the shortage and limitations of data, the NDVI trend after fires cannot well represent the recovery of vegetation. Overall, based on the analysis of Landsat-8 satellite images before and after the fire, this paper verifies the difference in the fire resistance of five tree species in the old-growth forests for different burn severities.