Great Plains Studies, Center for
Date of this Version
Spring 2002
Abstract
White-tailed deer (Odocoileus virginianus) populations have in the past, and continue today, to increase in the Great Plains and North America. However, their impact on native plant species and endangered ecosystems such as the tallgrass prairie is poorly documented. To better understand the consequences of increasing deer numbers for native shrubs in grasslands, we assessed the extent of their summer browsing activity on six shrub species (wild plum, rough-leaved dogwood, smooth sumac, fragrant sumac, and coralberry) along transects that spanned riparian margins to upland tallgrass prairie. The proportion of terminal shoots browsed was quantified along established white-tail deer trails and in parallel transects off trails in watersheds that varied in fire history at the Konza Prairie Biological Station (Kansas). Proximity to deer trails was a strong determinant of deer browsing activity. Along trails, 20% of the twigs surveyed (N = 60,032) were browsed, whereas off trails less than I % of twigs (N = 14,785) were browsed. Coralberry and rough-leaved dogwood comprised 80% of the shrub cover along trails, whereas wild plum, prickly ash, smooth sumac, and fragrant sumac had less cover, in that order. However, browsing was greatest on wild plum and rough-leaved dogwood (between 40% and 50% of available twigs), and the proportion of twigs browsed out of the total twigs used was highest for rough-leaved dogwood. Based on preference ratios (use/ abundance), white-tail deer are likely to have the greatest impact on the less common wild plum and smooth sumac as well as rough-leaved dogwood. Interestingly, white-tail deer avoided the most common shrub, coralberry, at this time of year. Our results suggest that even in summer, when deer tend also to forage on herbaceous species in grasslands, deer browsing may have significant local impacts on woody species of tallgrass prairies in the Great Plains. Concurrent increases in woody plant cover and abundance in grasslands throughout the Great Plains suggest that deer browsing is not yet intense enough to prevent shrub expansion into tallgrass prairie.