Sawgrass (Cladium jamaicense) responses as early indicators of low-level phosphorus enrichment in the Florida Everglades

Abstract

Anthropogenic phosphorus (P) inputs to the Florida Everglades have produced dramatic changes in the wetland vegetation of this otherwise oligotrophic system. While the proliferation of undesirable plant species in response to enrichment has been well documented, nutrient-related changes in the physiological and morphological attributes of existing vegetation, prior to any shifts in species composition or changes in the spatial extent of certain taxa, have yet to be adequately characterized. In this experiment, three sawgrass-dominated areas were enriched with P for 3 years at rates of 0.4 g P/m 2 /year (HP), 0.1 g P/m 2 /year (LP), or 0 g P/m 2 /year (controls) to assess potential impacts of P-enriched discharges from stormwater treatment areas into the Everglades. Elevated concentrations of TP in rhizomes and leaves and reduced ratios of leaf N:P were detected in HP plants within *1 year at most sites. Live leaf densities, plant heights, and plant densities of the HP groups were generally higher than LP and control groups after 2 years, a pattern that was evident even after major fire events. Total aboveground biomass was significantly elevated in both HP and LP treatments at two of the three sites after 3 years. No change in species composition was detected during the study. Planned hydrologic restoration measures will increase P loads into parts of the Everglades that have not previously experienced anthropogenic P enrichment. Monitoring native vegetation such as sawgrass can be a sensitive and relatively robust means of detecting unintended P enrichment in these areas prior to shifts in vegetation community composition or changes in area cover of key species.

Water source utilization and foliar nutrient status differs between upland and flooded plant communities in wetland tree islands

“…This difference in N:P ratios arises also because of differences in species composition, although both hammock types predominantly have Neotropical hardwoods. Other plant communities and species in the Everglades can have ratios higher than that in tree island hammocks, such as approximately 42 for pine rocklands (Saha et al 2009) and 27-84 for sawgrass (Miao and Sklar 1998;Richardson et al 1999;Smith et al 2009) in the northern Everglades, thus supporting the idea of tree islands as localized phosphorus hotspots in the otherwise extremely oligotrophic Everglades landscape.…”

Efficient Wetland Surface Water Detection and Monitoring via Landsat: Comparison with in situ Data from the Everglades Depth Estimation Network

“…Exotics and cattail exhibited still lower agreement accuracies and higher variability than most canopied wetland environments. Tending to occur along canals and levees, such locations in the normally oligotrophic Everglades often exhibit relatively enhanced vegetation growth, higher density and increased cover due to the leaching of nutrients (mainly phosphorus) from the canals [68][69][70][71][72][73][74]. Therefore, this community persists in areas of altered water quality over deeper, dynamically inundated ground.…”

Stable isotope compositions of aquatic flora as indicators of wetland eutrophication

“…In contrast, the high d 15 N at the impacted sites was due to P enrichment which leads to high N demand and low 15 N fractionation. Many studies have demonstrated that P is the limiting nutrient in the Everglades (e.g., Newman et al, 1996Smith et al, 2009. Recent studies using stable isotopes found a positive relationship between TP and d 15 N of periphyton, sawgrass and cattail in WCA-1 and WCA-2A, which was attributed to P-driven plant growth and reduced isotope fractionation (Inglett and Reddy 2006;Chang et al, 2009).…”