Date Awarded
2023
Document Type
Thesis
Degree Name
Master of Science (M.Sc.)
Department
Biology
Advisor
Martha Case
Committee Member
Harmony Dalgleish
Committee Member
Matthias Leu
Abstract
Odocoileus virginianus (white-tailed deer) density has greatly increased in many areas of eastern North America over the last century, due primarily to habitat fragmentation and the elimination of natural predators. Consequently, deer over- browsing has become an important conservation concern because it can lead to changes in plant community composition, loss of biodiversity, and altered regeneration dynamics. Forests may be particularly slow to recover from the release of deer pressure after chronic long-term browsing due to legacy effects such as impoverished seed and bud banks, low seedling recruitment, and the spread of nonpalatable species, leading to forest homogenization. Additionally, abiotic conditions may affect the speed of recovery and differ from the conditions present when the forest developed. This research examines the return of vegetation after chronic deer browse within a second-growth, Eastern Coastal Plain Forest, located in Williamsburg, Virginia. It utilizes sixteen deer exclosure plots with paired controls, erected in 2014, to address the following questions: (1) How does the exclusion of deer affect the return of vascular plant richness, abundance, and diversity? (2) What are the contributions of light, moisture, and soil nutrients to the changes in vascular plant diversity and abundance? (3) Are there apparent differences among individual plant species in their response to deer exclosure, and would any of these species be good indicators of recovering vegetation? All plants within the 10 meter x 10 meter plots were counted, identified, and classified by size for each sampling year. Abiotic factors measured in 2022 comprised percent open canopy, soil organic matter, carbon, nitrogen, phosphorus, and water content. The soil variables were then transformed into principal components axes for further analyses. Generalized linear mixed models tested the associations of treatment and abiotic factors with the change in richness and abundance. Both deer exclosures and abiotic factors significantly contributed to an increase in plant richness (P = 0.014 and 0.017, respectively) with homogeneity among plots significantly decreasing in exclosed plots compared to control plots (P < 0.005; Levene’s test). Overall plant abundance also significantly increased in exclosures (P = 0.003) but was not associated with abiotic factors (P = 0.077). Although these results are largely consistent with theoretical expectations, the data are strongly led by the seedling dynamics of common forest species, particularly Acer rubrum (red maple). New recruits persist longer in exclosed plots than in controls, but then experience high levels of mortality by their third year’s growth. Only two species showed evidence of establishment beyond their third year in exclosures. These were Euonymous americanus (strawberry bush) and Parthenocissus quinquefolia (Virginia creeper), two very common and widespread species that could be used as indicators of browse pressure. These results are consistent with the hypothesis of deer legacy effects on a forest that create a reduced response to vegetation recovery after the removal of browse pressure. In addition, this study suggests further complications of recovery due to the influence of abiotic factors.
DOI
https://dx.doi.org/10.21220/s2-x6np-rh35
Rights
© The Author
Recommended Citation
Smith, Olivia, "Slow Apparent Recovery Of An Eastern Coastal Plain Forest After Intense Deer Browsing" (2023). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1709301434.
https://dx.doi.org/10.21220/s2-x6np-rh35
