Ecohydrologic evaluation of wetlands on phosphatic clay settling areas

Clay Settling Areas (CSAs) are prominent features of the post phosphate mining landscape that currently comprise 40,500 hectares in central Florida. Wetland creation on CSAs seems feasible since surface water features naturally form due to the isolated watersheds and low-permeability clays that are characteristic of these systems. Hydrologic evaluations of a series of CSAs using surface water, groundwater, and climatic data were performed to calculate water budgets of potential wetland areas. Water budget calculations resulted in significant residual losses that suggested underestimation of summer evapotranspiration (ET) when using traditional climatic-based models. Analysis of the diurnal surface water fluctuations supported these findings and resulted in ET rates as much as two times typical summer values in the region, demonstrating the highly productive nature of these systems. Surface water and groundwater analysis concluded that groundwater flow may be limited, though the potential for seepage into the surface water features was observed. The hydrologic evaluations were used to create temporal models to aid in active wetland restoration of CSAs by providing hydroperiod and water depth predictions.;To relate hydrology with the biota, transects were established down a hydrologic gradient from upland into the surface water features, where a series of soil moisture probes were installed at different depths along the transects. Root biomass allocation with depth and transpiration of Salix caroliniana were also measured along these transects to observe effects of the hydrologic regime on plant behavior. Soil moisture data demonstrated the large capillary forces of the clayey soils, with saturation levels occurring over a meter above the water table. Root biomass allocation was to depths over one meter and into the water table with little preclusion from the clays. The results from the transpiration studies supported the evidence of high evapotranspiration rates of these systems, and found that this was in large part due to the transpiration of Salix caroliniana. These results revealed attributes of Salix caroliniana that, along with maintained saturation levels through most of the soil profile, explain its success on CSAs and demonstrate the presence of broad transitional zones appropriate for wetland restoration.