OOS 26-5 - Analyzing and predicting fire refugia throughout British Columbia, Canada

Increases in fire activity due to climate change and past forest management practices could potentially expedite large-scale vegetation transitions and be detrimental to conservation efforts aimed at maintaining old growth forests. Fire refugia are areas within fires that escape burning due to features and conditions which make them more resistant to this form of disturbance, thereby promoting forest resilience. This fire resistance helps to stave off such vegetation transitions, while also protecting critical old growth forest structures from burning. In this study, we investigated the role of hydrological, ecological, and topographic heterogeneity, as well as climate patterns, on the presence of fire refugia in forested ecosystems throughout the province of British Columbia, Canada, over a 33-year (1986-2019) period. Using the Relativized Burn Ratio, a remote-sensing measure of continuous fire severity, we located fire refugia by identifying values below thresholds corresponding with field-based measures of fire severity. We used boosted regression trees to model the probability of fire refugia in forested stands as a function of both biotic (e.g., vegetation) and abiotic (e.g., topography, climate) controls in each of the fire regime units throughout the province. Models were used to create predictive maps of fire refugia probability, which were then overlaid with mapped old growth forest to determine the extent to which predicted fire refugia and old growth stands correspond. Correspondence between fire refugia and old growth varied greatly across fire regime units and generally showed a strong effect of topography in locations where refugia and old growth stands overlapped. These maps can be used to help determine fire-resilient locations suitable for conservation efforts and refugia-informed fuel management practices.