Date of Award

Fall 2019

Document Type

Open Access Dissertation

Department

Biological Sciences

First Advisor

David S. Wethey

Abstract

Plant communities in the Southeastern United States Coastal Plain constitute a rich assemblage of species from neighboring floristic provinces and include over 1,000 species endemic to the region. Conservation of these unique landscapes requires a better understanding of potential impacts from human activity and a changing climate. As a model species, the endemic tree Loblolly Bay (Gordonia lasianthus) is representative of Carolina Bays, pocosins, and isolated wetland habitats that accentuate Longleaf Pine ecosystems which dominate the focus area. Seed-dispersal events in Loblolly Bay are limited to periods of relatively low humidity primarily during the months of October to December, and require horizontal winds to release and carry seeds. Using measured seed- fall velocities, field observations, herbarium specimens, and weather data, dispersal models indicate that prevailing wind speed and direction under these conditions serves to restrict the species dispersal potential to points southeast of parent trees, and that calculated population migration rates reach a maximum of 30 meters per decade when trees are 10 years old. Examination of meteorological conditions during extreme weather events such as hurricanes revealed no noticeable exception to these findings. By comparison, Species Distribution Models using a multimodel ensemble of 22 climate forecasts determined that calculated climate velocities and predicted presence velocities drastically outpace dispersal potential at rates over 50 times greater (2 km/decade) and move perpendicular (northeast) to modeled dispersal patterns. Under forecast climate scenarios, calculated residence times on protected lands within the observed range indicate the potential for multiple local extirpation events by the mid-21st century. While climate refugia are unlikely to support static populations, predicted outcomes may be mitigated through proactive measures to augment protected areas or through the assembly of habitat corridors.

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Biology Commons

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