Lodgepole Pine Vigor, Regeneration, and Infestation by Mountain Pine Beetle Following Partial Cutting on the Shoshone National Forest, Wyoming

摘要

Lodgepole pine (Pinus contorta var. latifolia Engelm.) stands were thinned in the Shoshone National Forest of northwestern Wyoming in 1979 and 1980 using different forms of partial cutting to determine if losses to mountain pine beetles (Dendroctonus ponderosae Hopkins) could be reduced by such treatment. Average losses of trees 5 inches diameter at breast height and larger during the 5 years following thinning ranged from less than 1% in the spaced thinnings to 7.4% in the 12-inch diameter limit cut, compared to 26.5% in check stands. Regeneration 5 years after thinning ranged between 1,160 and 3,560 seedlings per acre, with pine being favored in the more open stands. Residual trees increased radial growth significantly during the first 5 years following thinning. However, many trees should have remained susceptible to mountain pine beetle infestation because of large diameter and low growth efficiency. Changes in microclimate of thinned stands are suspected of affecting beetle behavior and hence of reducing numbers of infested trees.