Publication Date


Document Type


Committee Members

Don Cipollini (Committee Member), Thomas Rooney (Advisor), James Runkle (Committee Member)

Degree Name

Master of Science (MS)


The effects of excessive white-tailed deer (Odocoileus virginianus) browsing on forest understory plant communities are well-documented. However, these studies are usually short-term, and fail to focus on phylogenetic diversity and additional variables that may explain species composition. This study examined ecological and phylogenetic diversity, vegetation structure, and light (% insolation) in short (7 year) and long-term (22 year) exclosures (and paired controls) to identify if competitive exclusion occurs in long-term exclosures. A deer browsing susceptibility index (DBS) was also developed to identify species reliant on exclosures for persistence. Statistical analysis using 2-way ANOVAs showed increased percent cover, vegetation height, and phylogenetic diversity in old exclosures compared to controls, but there were no significant differences in ecological diversity. Ecological and phylogenetic diversity was greatest in old exclosures compared to young, but young exclosures were more ecologically diverse than paired controls. There were no differences in light or biomass for any exclosure age or treatment. Based on these results, competitive exclusion is not occurring in these 22 year exclosures. A comparison of mean pairwise phylogenetic distance to a randomized null model shows phylogenetic clustering in old controls, indicating browsing is a habitat filter selecting for species least susceptible to browsing (i.e. graminoids and club mosses). As expected, browse susceptible species consisted mainly of broadleaf herbs. Highly susceptible species may rely on exclosures for persistence, and although competitive exclusion does not occur, exclosures are not a practical way to promote ecological and phylogenetic diversity in forest understories.

Page Count


Department or Program

Department of Biological Sciences

Year Degree Awarded


Included in

Biology Commons