Ten-Year Impact of Spruce Budworm on Spruce-Fir Forests of Maine.

摘要

Annual measurements from 1975 to 1985 on 278 Maine spruce-fir plots infested by the spruce budworm were analyzed by forest type, density, host-species composition, diameter, and percent fir or spruce composition classes to determine impact on growth and mortality. In 1985, balsam fir, one-fourth of the initial 1975 basal area per acre, had 50 percent mortality in mixedwood and 75 percent in softwood types. Spruce mortality was 3 times higher in the softwood than in the mixedwood type. Balsam fir mortality increased with increasing basal-area density with the heaviest losses occurring 2 years earlier in the highest density stands. Heaviest losses in the mixedwood stands usually occurred about 4 years after those in the softwood stands.