The negative impacts of overabundant white-tailed deer (Odocoileus virginianus) and invasive species in deciduous forests have been well documented. However, their combined impacts are less understood. We tested the impacts of 11 years of exclusion of deer and removal of the invasive shrub Amur honeysuckle (Lonicera maackii) on forest floor plant composition in deciduous forests in Ohio. We used five paired deer exclosure and access plots that were established in 2010 in the Miami University Natural Areas. One half of each plot had honeysuckle removed and the other half had honeysuckle present. In each half-plot we recorded percent cover of each species in 18 subplots. These plots were sampled in two survey periods: spring and summer. Species were classified as either native or nonnative and by growth forms. Richness of native species in summer was significantly affected by honeysuckle treatment and the deer * honeysuckle interaction. Native species richness was lower where honeysuckle was present; this effect was greatest in the deer exclosure plots. Cover of native species in both seasons was significantly impacted by both the deer treatment and the deer * honeysuckle interaction. Native cover was highest where both honeysuckle and deer were absent. Tree cover and vine cover were significantly affected by the deer treatment and interaction during both seasons. For these growth forms, cover was highest where both stressors were absent. Graminoid cover in both seasons was significantly greater where deer had access and in summer was also greater where honeysuckle was removed. Annual cover in summer was significantly greater in deer access plots. These findings indicate that overabundant deer have more impacts on forest floor vegetation than do invasive shrubs. However, the exclusion of deer combined with removal of this invasive shrub resulted in the greatest values of native cover, tree cover, and vine cover.
Author: Hanna Leonard
Advisor: David Gorchov, Biology
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