Snow Depth and Browsing by White-Tailed Deer (Odocoileus virginianus) in a Northern Wisconsin Hardwoods Forest

Abstract

Many factors influence woody seedling regeneration in north temperate forest ecosystems. One important factor is snow depth, which may in turn interact with herbivory by white-tailed deer (Odocoileus virginianus). In this study we measured variation in snow depth at a northern Wisconsin hardwood forest over two winter seasons, 2012-2013 and 2013-2014. Snow measurements were taken approximately bi- weekly at 60 locations in the 25 hectare Wabikon Forest Dynamics Plot (WFDP) near Crandon, WI, USA. White-tailed deer herbivory was assessed at 275 2x1 m subplots within the WFDP during summer 2013. Our objectives were to identify biotic and abiotic variables that affected snow depth and to associate snow depth with seedling herbivory and mortality. Results showed that biotic variables had significantly greater impact on snow depth than abiotic variables such as slope, elevation, and aspect. Seedling herbivory and mortality during these two years were unrelated to local variations in snow depth. Deer were virtually absent from most of the forest plot during winter months. Both field seasons experienced above average snow levels, so this finding might not apply during all years. Nevertheless, our results shed important light on the dynamics of snow accumulation and melting in northern hardwood forests and suggest that snow inhibits deer browsing during winter. The effects of snow cover on deer browsing are especially important in light of predicted climate change, which may lead to reduced snow cover and therefore increased herbivory of seedlings.