Title

Plant Community Development in Storm-induced Overwash Fans of the Otis Pike Fire Island High Dune Wilderness Area, New York

Date of Award

4-10-2018

Semester of Degree

May

Document Type

Open Access Dissertation

Major Professor

Brian Underwood

Steering Committee Member

Donald Leopold

Steering Committee Member

Shannon Farrell

Steering Committee Member

Stewart Diemont

Steering Committee Member

Stacy McNulty

Abstract

Barrier island systems are driven by disturbance, climate, and geomorphology. Previously, barrier island vegetation communities were primarily described by microclimate variability. The purpose of this dissertation is to better understand effects of white-tailed deer on developing plant communities on barrier islands after a catastrophic disturbance. I used distance-based Moran's eigenvector maps to identify spatial structures in vegetation communities of overwash fans in the third and fourth years after Hurricane Sandy. Spatial structures were present and significant at two or more frequencies in all overwash fans and explained the greatest amount of variation in vegetation community composition. Induced spatial dependence was predominantly controlled by proximity to foredune. I identified five biotic and abiotic influences to community composition in overwash fans and ranked their importance through canonical correspondence analysis. Gradients in productivity and elevation were primarily responsible for community composition and deer effects were not identifiable at the plot level. I identified effects of deer on vegetation cover and richness through a paired exclosure experiment, though only cover effects were statistically significant. Deer effects on cover were starker than those observed on species richness, suggesting assessments of deer effects on depauperate communities should focus on richness and cover. Lastly, I assessed effects of white-tailed deer on the rate of vegetation recovery in overwash fans through imagery classification and assessments of local white-tailed deer density. Though deer affect vegetation cover through trampling, grazing, and browsing in overwash fans, their effects on recovery rates were minimal and not statistically significant. Two overwash fans are expected to recover to pre-Sandy conditions within the decade since a nascent foredune is present and growing. Two overwash fans may never recover due to continued disturbance. The five remaining overwash fans have a slowly-forming nascent foredune, and changes in climate and frequency of storm events make their futures uncertain. Though deer do not pose a threat to the resilience of the barrier island, selective foraging behaviors may change composition and developmental trajectories of recovering vegetation communities over time.

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