Synergistic interactions of bark beetles and wildfire: Post-fire outbreak potential of the Douglas-fir beetle (Dendroctonus pseudotsugae) in dry interior forests of western North America

Douglas-fir beetle (Dendroctonus pseudotsugae) is one of the most significant agents of mortality in mature Douglas-fir forests. Landscape-scale outbreaks are common following widespread disturbance such as wildfire, drought and/or disease. These events increase the availability of defensively compromised host trees and thereby facilitate beetle population increases. As climate change continues to exacerbate stress in conifer forests, there is concern that Douglas-fir beetle outbreaks will increase in size and severity. Following recent record-breaking wildfire seasons in the dry interior forests of northwestern North America, we initiated a study to elucidate the relationship between Douglas-fir beetle and wildfire on multiple spatial scales. We found the outbreak potential of Douglas-fir beetle to be constrained by burn severity and the presence of other subcortical insects of the Buprestid and Cerambycid families. These relationships varied across three large burn complexes in the mature, dry Douglas-fir forests of British Columbia, Canada. Results will be discussed within the context of future forest management strategies for changing disturbance regimes in a warming environment.