Establishing Exclosures to Measure the Long-term Effects of Elevated White-tailed Deer Populations on Regionally Sensitive Plant Communities—Interim Report

Maragi, Frank

Apostle Islands National Lakeshore (APIS) has been identified as an area with regionally significant forest communities dominated by Canada yew (Taxus canadensis) that are being threatened by a burgeoning white-tailed deer (Odocoileus virginianus) population. Sand Island is very unique in that it is one of the few islands that, until recently, did not maintain a population of deer. Forested ecosystems with no history of deer have become increasing scarce elsewhere throughout North America. The lack of a deer population on these islands has resulted in a very rare vegetation community that has an abundance of Canada yew (Taxus canadensis), a species that is nearly extirpated from mainland Wisconsin. When deer populations become established in areas with this rare community type, the structural and functional integrity of Canada yew are at risk. Exclosure studies have long been used as an affective tool to qualitatively and quantitatively demonstrate the dramatic changes that large mammalian herbivores can impose on plant communities. By excluding herbivores such as white-tailed deer from selective areas and measuring the response in plant community structure and function over time, resource managers can more affectively evaluate the relative impact on the resource. The current project was initiated to establish baseline data resource managers can use to assess thresholds in deer populations.