Mountain Pine Beetle-Induced Changes to Selected Lodgepole Pine Fuel Complexes within the Intermountain Region

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Forest Science

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The mountain pine beetle (Dendroctonus ponderosae) is a forest insect that infests lodgepole pine (Pinus contorta var. latifolia) forests in the Intermountain West. The often widespread mortality caused by the mountain pine beetle has been suggested to result in significant changes to stand structure, composition, and total fuel loading; however, little quantitative information that documents these changes is available. We examined mountain pine beetle-induced changes to ground, surface, and aerial fuels in lodgepole pine stands during current epidemics and 20 years after an epidemic. Results indicated that there were statistically significant increases in the amounts of fine surface fuels in recently infested stands, i.e., those stands 5 years past peak mortality. In the previously infested stands, there were large increases in the amounts of dead woody fuels in all but the smallest size classes, with a 7.8-fold increase in down woody fuels 7.62 cm in diameter. Live shrubs and the amount of subalpine fir (Abies lasiocarpa) regeneration were also significantly greater in the postepidemic stands. The net result of epidemic mountain pine beetle activity was a substantial change in species composition and a highly altered fuels complex in which large dead woody fuels and live surface fuels dominate.