Effect of Partial Cutting Treatments of Lodgepole Pine Stands on the Abundance and Behavior of Flying Mountain Pine Beetles

1989

S. 566-574

5 Abb., 3 Tab., 21 Lit. Ang.

Unselbständiges Werk

200038998

Passive barrier traps deployed at three heights above ground were used to determine the effect of five intensities of partial cutting of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) and two unthinned check stands on response of flying mountain pine beetles (Dendroctonus ponderosae Hopkins) from 1980 to 1983 on two sites in western Montana. Percentages of mountain pine beetles caught 4 years after thinning were significantly greater in the least severely thinned (27.6 m2 basal area/ha) treatment (27%) and the unthinned check (28%) than in the 25.4 cm diameter limit (8%) and the 23.0 m2 basal area/ha (7%) thinning (P < 0.05). Numbers of mountain pine beetles trapped in the 18.4 m2 basal area/ha thinning did not differ significantly from other treatments. The proportions of mountain pine beetles caught at three trapping heights differed significantly (P < 0.05), totaling 63, 28, and 9% at midbole, midcrown, and 1.8 m above ground, respectively. Fewer trees were killed in relation to the numbers of mountain pine beetles trapped in the most severely thinned stands. However, tree mortality rates could not be attributed to thinning- induced changes in tree vigor. These findings, and the preference of flying mountain pine beetles for the midbole stratum, suggest that stand environment is an important factor regulating the severity of tree killing.