Publication Date

2009-04-25

Availability

Open access

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Biology (Arts and Sciences)

Date of Defense

2009-02-27

First Committee Member

David Janos - Committee Member

Second Committee Member

Don DeAngelis - Committee Member

Third Committee Member

Leonel Sternberg - Mentor

Fourth Committee Member

Fernando Miralles-Wilhelm - Outside Committee Member

Abstract

Spatial and temporal heterogeneity of water and nutrient pools is closely associated with the existence of different plant communities in hydrologically-controlled ecosystems such as the Everglades. These various communities differ in their flooding and fire tolerances as well as nutrient requirements. Upland plant communities are of particular ecological significance since they have high biodiversity and provide habitat to terrestrial fauna, yet comprise less than 10 % of the total area. Restoration and maintenance of such communities requires an understanding of their water and nutrient requirements. Chapter 2 compares water source utilization in hammocks and pine rocklands on the Miami Rock Ridge using stable isotopes of water. Hammocks do not flood, while adjacent pinelands may flood between 2-3 months. In the wet season, hammocks were found to use phosphorus (P) rich soilwater, a local pool of water and nutrients while pineland plants primarily relied upon groundwater, the regional pool. Access to a rich pool of P in the oligotrophic Everglades was associated with higher community-level foliar P concentration in hammocks. However in the dry season, hammocks utilized groundwater, which suggests sensitivity to extended droughts. Chapter 3 compares the hammock (upland or head) and swamp forests (lowland or tail) on tree islands in the Shark River Slough. Uplands were associated with P-rich soilwater uptake in the wet season, with regional water uptake in the dry season. Accordingly, tree island heads are rich in foliar P and thereby P-hotspots in the Everglades. Foliar nutrient concentrations can thus indicate limiting nutrient availability in the Everglades. Chapter 4 looks at how leaf phenology patterns are tied to water and nutrient pools. Leaf fall in ridge hammocks is associated with high foliar carbon isotope values over the dry season, which is not the case for tree island hammocks. However, in some species, high levels of foliar nitrogen are also associated with high foliar C13 values indicating stomatal limitation of photosynthesis. Growing season for most hammock species is the wet season coinciding with high availability of P, as reflected in high foliar P in this season. Linking water sources to foliar nutrients elucidates roles of water and nutrient pools in leading to different plant communities within an ecosystem.

Keywords

Phenology; Tree Islands; Pinelands; Hammocks; Foliar Nutrients; Stable Isotopes; Ecohydrology; Everglades

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