The Deer Grazing Project

Deer grazing and plant species composition in Midwestern maple and oak forests. Graduate student David Augustine worked on this project during 1995-1997. Studies included isolated forests of sugar maple and red oak surrounded by agricultural fields in southern Minnesota with low and high densities of white-tailed deer. There were three main results from this study.

First, the larger the area of alfalfa fields within 1.5 km of the woodland, the less deer grazing there was on woodland wildflowers, because the deer used alfalfa as a food source and used the woodlands mostly for cover.

Second, Trillium populations were negatively impacted by deer, especially where deer populations were high and there were no nearby alfalfa fields. Protection of individual plants from deer resulted in dramatic increases in plant leaf size and flowering rates.

Third, deer grazing can cause two alternate states with and without lush forest floor plant communities. Experimental studies with deer exclosures in forests with high and low deer densities showed that there is a tipping point for the herbaceous plant community, If deer consume more than plant growth, plants are driven to near extinction, whereas if deer consume less annually than plants grown, a lush covering of forest floor and deer can coexist.

Publications
Augustine, D. J., and P. A. Jordan. 1998. Predictors of white-tailed deer grazing intensity in fragmented deciduous forests. Journal of Wildlife Management 62:1076-1085.

Augustine, D. J., and L. E. Frelich. 1998. Effects of white-tailed deer on populations of an understory forb in fragmented deciduous forests. Conservation Biology 12:995-1004.

Augustine, D. J., and L. E. Frelich. 1998. Evidence for two alternate stable states in an ungulate grazing system. Ecological Applications 8:1260-1269.