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Recent increases in nutrient concentrations at sites throughout the Water Conservation Areas of southern Florida and expansion of cattail populations into areas previously populated by sawgrass have led to considerable discussion on their affect on vegetational abundance and distribution. Critical questions concern the response of plant communities to the increased nutrient loads and whether vegetational changes observed over the last few decades are greater than those that have occurred naturally throughout the history of the region. To address these questions, pollen assemblages from peat cores have been examined as proxy evidence for vegetational abundance. Research on these sites is part of a larger study on the terrestrial ecosystem history of southern Florida, which focuses on analysis of a series of cores collected throughout the historic Everglades to interpret floral changes over the last few thousand years, with particular emphasis on high-resolution studies of the last 150 years.
This report is part of a series of reports documenting pollen data from cores collected in the historic Everglades. Sites F1 and U3 represent end members of a transect of sites along a nutrient gradient south of the Hillsboro Canal in Water Conservation 2A. Site F1 (26° 16.892'N, 80° 18.407'W) is situated at a high-phosphorous site in which the vegetation consists of a nearly monospecific stand of cattails (Typha ) in approximately 1 meter of water. Site U3 (26° 17.25'N, 80° 24.68'W) is located in an area with pristine nutrient content in the surface water, and its vegetation is a mixture of cattails and sawgrass (Cladium) in about 0.5 meter of water. These sites are part of a transect in the South Florida Water Management District's "Threshold Study Sites", which are undergoing extensive chemical analyses to document changes in nutrient content temporally and spatially (Orem et al., 1997). Examination of pollen assemblages from these cores was initiated to determine the timing of cattail expansion in the region as well as other vegetational changes.
This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
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