Forest Vegetation Response to White-Tailed Deer Population Reductions in a Large Urban Park

Overabundance of white-tailed deer (Odocoileus virginianus) constitutes a threat to the biological diversity and ecosystem function of forested natural areas. Managers of Eagle Creek Park, a large forested park in Marion County, Indiana, that is surrounded by densely populated residential housing, implemented a deer population reduction program in 2014 to reduce negative impacts to park ecosystems. Starting in 2013, we instituted a monitoring program within two nature preserves imbedded within Eagle Creek Park to track the response of vegetation communities to population reductions. We found positive response in the heights of two published indicator species, Arisaema triphyllum (jack-in-the-pulpit) and Actaea pachypoda (white baneberry). We also observed increased richness and density of native woody species and an overall reduction in the proportion of twigs browsed at both preserves. The reduction efforts coincided with heavy mortality of overstory Fraxinus (ash) trees from emerald ash borer (Agrilus planipennis). Consequently, while we observed recovery of native woody species at both sites, one of the preserves also experienced a large increase in the abundance of nonnative woody plants in response to increased light availability and reduced browse pressure. Overall, our monitoring showed that deer population reductions have allowed the recovery of vegetation communities in the park. However, continued monitoring is needed to track vegetation community response to continued management of the deer population in conjunction with other human pressures on biological communities in the park.