HR: 0800h
AN: H51H-0868    [Abstracts]
TI: Water Source Utilization of Hammock and Pine Rockland Plant Communities in the Everglades, USA.
AU: * Saha, A K
EM: asaha@bio.miami.edu
AF: Department of Biology, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33124, United States
AU: Sternberg, L
EM: leo@bio.miami.edu
AF: Department of Biology, University of Miami, 1301 Memorial Drive, Coral Gables, FL 33124, United States
AU: Miralles-Wilhelm, F
EM: miralles@fiu.edu
AF: Department of Civil and Environmental Engineering, Florida International University, 10555 W.Flagler St, Suite EC-2330, Miami, FL 33174, United States
AB: South Florida has a mosaic of plant communities resulting from topographical differences, spatially varying hydroperiods and fire. The only plant communities not flooded in the wet season are hardwood hammocks and often pine rocklands. Natural fires burn off litter accumulated in pine rocklands, with the exception of organic matter in sinkholes in the limestone bedrock. This relative lack of soil is thought to constrain pineland plants in the Everglades to depend upon groundwater that is typically low in nutrients. In contrast, adjoining hardwood hammocks have accumulated an organic soil layer that traps rainwater and nutrients. Plants in hammocks may be able to utilize this water and thereby access nutrients present in the litter. Hammocks are thus viewed as localized areas of high nutrients and instances of vegetation feedback upon the oligotrophic everglades landscape enabling establishment and survival of flood-intolerant tropical hardwood species. This study examines water source use and couples it to foliar nutrient concentrations of plants found in hammocks and pinelands. We examined the δ²H and δ¹⁸O of stem waters in plants in Everglades National Park and compared those with the δ²H and δ¹⁸O of potential water sources. In the wet season hammock plants accessed both groundwater and water in the surface organic soil layer while in the dry season they relied more on groundwater. A similar seasonal shift was observed in pineland plants; however groundwater constituted a much higher proportion of total water uptake throughout the year under observation. Concomitant with differential water utilization by hammock and pineland plant communities, we observed hammock plants having a significantly higher annual mean foliar N and P concentration than pineland plants. Most hammock species are intolerant of flooded soils and are thus constrained by the high water table in the wet season, yet access the lowered groundwater table in the dry season due to drying up of surface soilwater. This dependence on a relatively narrow seasonal range of water table depth has important implications for South Florida water resource management that can affect these ecologically important upland communities in the Everglades. Being the only emergent areas in the wet season, hammocks provide habitat for a wide range of flora and fauna.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0476 Plant ecology (1851)
DE: 0497 Wetlands (1890)
DE: 1852 Plant uptake
SC: Hydrology [H]
MN: 2007 Fall Meeting