Title

Eco-hydrology and physiological water relations of vegetation along coastal dune ecotones on subtropical islands

Date of Award

2005

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biology

First Committee Member

Leonel da Silviera Lobo Sternberg, Committee Chair

Abstract

As evidence mounts that sea levels are rising, it becomes increasingly important to understand the role of ocean water in the terrestrial hydrology of coastal ecosystems. In coastal dunes, ocean water may enter soils via salt spray through the surface or by ocean water intrusion into deeper vadose layers. However, it is unclear if ocean water enters terrestrial soil of dunes and if it affects dune vegetation. The purpose of this study is to investigate the influence of ocean water on soil and vegetation of coastal dunes. Three coastal dune systems, a barrier island off the coast of southern Florida, and two islands in the Bahamian bank/platform system were investigated. Using delta 18O as a water tracer, I showed the variance of delta18O values of vegetation stem water that is closest to the ocean indicates a mixed water harvesting strategy in which plants utilize ocean, ground water and rain. In contrast, the inland vegetation relies mostly on rain.Salinity, moisture content and stable isotope date show that the vadose (surface to the water table) soil hydrology of coastal dunes is spatially and temporally dynamic. Evidence supports that ocean water enters the soil profile from above by salt spray deposition and from below by ocean water intrusion, processes that are most strongly evident in the driest months. Fluctuating periods of high soil salinity and ocean water deposition characterize dune areas closest to the ocean. Ocean water deposition across the dune drives plant function of species that are zonally distributed. Fore dune species uptake ocean water and show elevated water-use efficiency during the dry season. The few trans-dune species that are able to grow across dunes offer a special opportunity to investigate the eco-physiology of the same species at two extremes of the dune ecotone. The comparative physiology of trans-dune species Ipomoea pes-caprae (vine) and Coccoloba uvifera (shrub) in fore dune (5--12m inland) and back dune (45--55m inland) areas show that these species have different mechanisms to cope with osmotically stressful environments.

Keywords

Biology, Botany; Biology, Ecology; Biology, Plant Physiology

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3168684