Snow Avalanches and Vegetation Pattern in Cascade Canyon, Grand Teton National Park

Abstract

Snow avalanches in Cascade Canyon, Grand Teton National Park, have a significant effect on the region's vegetation mosaic, increasing the area's community diversity and creating a fragmented vegetation pattern. The structure and persistence of communities within avalanche tracks is a function of the frequency of avalanche occurrence. In many areas, shrub cover and conifer density increase as avalanche frequency increases. Conifers decrease in size yet increase in age as avalanches occur more often, a consequence of slower growth rates in trees within avalanche tracks. Because the probability of avalanche damage to conifers is related to the size of the tree, slow growth rates result in small trees that can survive many years in avalanche tracks, contributing to the persistence of the avalanche community. The canyon's vegetation patterns appear fairly stable due to the spatial and temporal consistency of avalanche occurrence and the persistence of communities in avalanche tracks. The primary effect avalanches have on this landscape is to increase the fragmentation of the vegetation patterns rather than to drive dynamic changes in the landscape mosaic.