Microclimate: an alternative to tree vigor as a basis for mountain pine beetle infestations

Thinning lodgepole pine stands increased light intensity, wind movement, insolation, and temperature. Temperatures on the south exposure of tree trunks and of soil were significantly higher in thinned than unthinned stands. Light and wind also were higher in the thinned stand. Fewer mountain pine beetles were caught in pheromone-baited traps in a thinned than in an adjacent unthinned stand. Percentage of trees killed by mountain pine beetle was only 2 percent in a thinned stand compared to 16 percent in an adjacent unthinned stand.