COS 111-1 - Changes in an understory vegetation community in response to active management of white-tailed deer (Odocoileus virginianus) density

Background/Question/Methods

When white-tailed deer are overabundant they alter vegetation communities. The Allegheny Plateau in Pennsylvania had overabundant deer populations (above 6 deer/km²) for 80 years. In response to repeated regeneration failures, the local community of land managers and hunters established a cooperative in 2000 to reduce deer density and monitor plant community response to the lowered herd. The Kinzua Quality Deer Cooperative (KQDC) used additional doe tags to reduce the deer population starting in 2001. Here we evaluate how the understory vegetation community changed with active deer management throughout the KQDC. We expected browse-related damage to decrease and plant density, reproductive structures, and overall richness to increase. Long-term research plots were established in 2001 throughout the KQDC and sampled in 2001, 2003, 2007, 2011, 2016, and 2021. During the periodic surveys species richness, percent cover, browse damage of woody species, and proportion of reproductive structures were quantified.

Results/Conclusions

Herd management efforts led to a drop in the deer density index throughout the KQDC to below 6 deer/km² in 2005, a decrease that lasted until 2018. From 2019 through 2022 deer densities rose to above 12 deer/km², similar to what they were at the inception of the KQDC. Most measures of the vegetation community recovered between 2003 and 2016. These included increases in species richness and the proportion of reproductive structures, as well as a decrease in browse damage. However, by the 2021 vegetation survey, we observed in erosion of these metrics of recovery, likely as a response to the rising deer densities. The fifteen years of reduced density allowed the understory vegetation community to begin recovering. Our results suggest that sustained herd reductions at the decadal scale does afford recovery in the understory vegetation community. However, these gains will lapse quickly if browse pressure rebounds. Thus, consistent and long-term deer management is needed for the understory communities to recover from degradation.