Stand-replacing fires reduce susceptibility of lodgepole pine to mountain pine beetle outbreaks in Colorado

Aim As climate change is increasing the frequency, severity and extent of wildfire and bark beetle outbreaks, it is important to understand how these disturbances interact to affect ecological patterns and processes, including susceptibility to subsequent disturbances. Stand-replacing fires and outbreaks of mountain pine beetle (MPB), Dendroctonus ponderosae, are both important disturbances in the lodgepole pine, Pinus contorta, forests of the Rocky Mountains. In the current study we investigated how time since the last stand-replacing fire affects the susceptibility of the stand to MPB outbreaks in these forests. We hypothesized that at a stand-scale, young post-fire stands (100-150years, stand age does not affect susceptibility to outbreaks, or (2) the high intensity of the most recent outbreak reduces the importance of pre-disturbance conditions for susceptibility to disturbance. If the warm and dry conditions that contribute to MPB outbreaks concurrently increase the frequency and/or extent of severe fires, they may thereby mitigate the otherwise increased landscape-scale susceptibility to outbreaks. Potential increases in severe fires driven by warm and dry climatic trends may lead to a negative feedback by making lodgepole pine stands less susceptible to future MPB outbreaks. © 2012 Blackwell Publishing Ltd