Response of mountain pine beetle (Dendroctonus ponderosae) populations to fire-injured lodgepole (Pinus contorta) and ponderosa (P. ponderosa) pines: Implications to disturbance interactions and bark beetle outbreaks

Mountain pine beetle (Dendroctonus ponderosae, MPB) and wildfire are important disturbance agents in western forests. We are investigating how fire injury affects D. ponderosae colonization, reproduction, and attacks on uninjured trees, and comparing these relationships between lodgepole and ponderosa pines. We established plots, monitored attacks, and caged infested trees within burned areas in northern Utah. Beetles colonized ponderosa pines of moderate or high fire-injury and reproductive rates increased with degree of injury. Populations initially increase, then declined. Beetles initially colonized lodgepole pines of moderate fire-injury, then shifted to low and uninjured trees in subsequent years. Population levels remained consistently high. These results suggest an initial pool of fire-injured trees can allow populations to build locally and infest healthy trees, but relationships vary between host species.