Mountain Pine Beetle Outbreaks in the Rocky Mountains: Effects on Fuels and Fire in Lodgepole Pine Forest (Abstract)

Changes in fuels were studied in northwestern Wyoming by sampling a sequence of ten stands that had been heavily damaged by beetles from 1 to 20 years earlier. Leaf litter increased only slightly (3-6%) for six years, and large woody fuels (which contribute much less to flammability) increased steadily and substantially (up to 16 x) for at least 20 years. Other fuel categories did not change significantly. While flammability may be increased during the first year or two after a beetle infestation because dead leaves are still on the trees, the risk of destructive fire during years 2-20 may be lower, primarily because 1) the continuity of canopy fuels is reduced and 2) the proportionate increase in forest floor fine fuels is small. Accelerated growth in understory trees may increase fuel continuity and fire risk after 20 years. Other factors such as drought, the proportion of the trees killed and the probability of lightning strikes are important variables.