Theses and Dissertations Collection

Managers and scientists alike are increasingly concerned with the impact of large disturbances on forests, especially under changing climate conditions. In this project, I aimed to understand the impacts of repeated disturbances, both wildfires and bark beetles, in mixed conifer forests. Mixed conifer forests are extensive throughout the western US, yet little is known about the impact of repeated disturbances on forest resilience. I addressed questions regarding vegetation responses following individual disturbances (either bark beetle or wildfires) and repeated disturbances (bark beetle and fire and repeated wildfires), as well as the impact of previous disturbances on the effects of subsequent wildfires. I used a combination of field work, remote sensing, and statistical analysis to answer questions at the stand and landscape scale. The interaction of bark beetles and wildfires did not result in different overall seedling density, surface fuel loading and stand structure than areas only impacted by wildfire. Bark beetle outbreaks without subsequent fires also resulted in the highest seedling establishment. I found repeatedly burned areas to have reduced fuel loading and tree regeneration than once burned areas, indicating increased resilience. Also, past wildfires reduced burn severity of subsequent large wildfires, but many other factors such as day of burning weather and topography also influenced burn severity. My work informs our understanding of forest trajectories and forest resilience following repeated disturbances. This work furthers our understanding of changes in forest landscapes following single and repeated disturbances and advances our ability to manage forests for increased resilience in the face of future disturbances.