Marsh vegetation patterns and soil phosphorus gradients in the Everglades ecosystem

Doren, Robert; Arementano, Thomas; Whiteaker, Louis; Jones, Ronald

In order to test the hypothesis that phosphorous enrichment is modifying Everglades marsh community composition, we sampled vegetation and soil phosphorus concentrations along four transects in separate areas representative of varying environmental conditions within the Everglades region. Every transect originated at or near a canal flow control structure and extended towards the center of the marsh because the canal flow structures were seen as potential nutrient input sources from "upstream" agricultural areas. Cladium jamaicense, wet prairie communities and Typha spp. dominated sites were sampled along each transect. Species frequency, and soil phosphorus data were collected. We compared soil phosphorus levels and determined correlations for between-species occurrences and between-species frequencies and phosphorus concentrations with distance from nutrient source (water flow structure). We compared within-transect effects and between-transect effects from north to south across the Everglades region. In all cases phosphorus levels and presence of Typha domingensis showed a negative relationship to distance from flow structure, while presence of Cladium and other natural communities showed a positive one. The pattern in marsh community composition and soil phosphorus content seen in the four marsh transects indicates that a strong relationship exists between Typha expansion, decline of Cladium marsh and wet prairie communities and rising phosphorus concentrations, and that these trends are correlated with nutrient input sources associated with agricultural runoff.