DIVERSITY AND DISTURBANCE IN A COLORADO SUBALPINE FOREST

Diversity of understory plant species in a disturbed subalpine forest in the Colorado Rockies was examined to explore the hypothesis that intermediate levels of disturbance generate and maintain high levels of diversity. In 1974, hurricane-force winds created a blowdown with three types of canopy conditions—severely disturbed, moderately disturbed, and lightly disturbed. Data on tree-stand structure were taken in order to characterize the gradient of canopy disturbance. Species diversity of understory plants was estimated using both alpha diversity and beta diversity. The stand canopy with intermediate damage had higher numbers of both understory species and individuals, as well as higher beta diversity compared with other sites. This suggests that intermediate levels of disturbance severity may offer more microhabitats, at least temporarily, for a wider range of species. [Key words: Colorado Rocky Mountains, diversity, intermediate disturbance, subalpine forest.]