The environmental services provided by multi-functional and multi–use watersheds are affected by the type, intensity, and spatial arrangement of land use as well as underlying environmental landscape properties. The Santa Fe River Watershed in Florida is large in size (3,585 km2) with soils that are predominantly sandy in texture and formed on karst terrain. The underlying geologic units include limestone, capped by Miocene sediments which tend to be rather clayey and phosphatic, and sediments that are sandy at the surface. Land cover is mixed with high- and low-intensity uses ranging from agriculture to upland forest. Topography is level to gently sloping and undulating. Our goal was to gain insight into complex landscape responses originating from anthropogenic stresses superimposed on a landscape formed on diverse parent material and dissected by a scarp with distinct lowland and upland areas. The specific objective of this study was to identify relationships between soil phosphorus (P) and the underlying parent material, geomorphology, soils, land use, and topography. We collected soil samples at 143 sites within the watershed and analyzed them for soil P using a Mehlich 1 extraction. Each site was characterized using a set of environmental variables delineated from geospatial data layers and field observations. Geospatial modeling was conducted within a GIS complemented by statistical analyses to assess relationships among environmental variable sets. The effect of land use on soil P was prominent with high values found in crops, improved pasture, tree groves and urban areas confounded by the effect of geomorphology and land resources. The geospatial distribution of P values within the watershed showed clusters of high and low values that were related to environmental landscape variables. Understanding the response in environmental properties, such as soil P, at the regional scale provides the framework to optimize environmental services performed by multi-use watersheds.
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