|Craft, C.B., J. Vymazal, and C.J. Richardson. 1995. Response of Everglades plant communities to nitrogen and phosphorus additions. Wetlands 15:258-271.|
Abstract: Nitrogen (N) and phosphorus (P) were applied to sawgrass (Cladium jamaicense), mixed sawgrass-cattail (Typha domingensis) and slough (shallow water communities dominated by Utricularia spp., Eleocharis spp., and Panicum spp.) communities in the Everglades for two years to test for N or P limitations and to investigate the plant community response. Nitrogen (as NH4+) and P (as PO43) were applied singly and in combination at rates of 0.6, 1.2, and 4.8 g P· m2· yr1 and 5.6 and 22.4 g N· m2· yr1. Plant response was quantified by measuring aboveground standing crop biomass and tissue N and P concentrations each year. Everglades plant communities are P limited. Phosphorus additions at the highest rate (4.8 g· m2· yr1) resulted in increased P uptake and biomass production by emergent vegetation. Tissue P concentrations of sawgrass and cattail were significantly higher in response to the high P (329-684 m g· g1) and high N+P (371-594 m g· g1) treatments (control = 94-256 m g· g1) in both years after the initiation of nutrient additions. Aboveground biomass also increased in response to the highest rate of P at the sawgrass (2618-3284 g/m2; control = 1158 g/m2) and mixed (1387-1407 g/m2; control = 502 g/m2) communities, but only after two years. At the slough site, the high P and high N+P treatments resulted in a significant decline of the Utricularia-periphyton mat after only one year of nutrient additions (16-74 g/m2; control = 364 g/m2). During the second year, the macroalga, Chara, expanded in these plots and replaced the floating mat as the major non-emergent component of the plant community. In all three communities, P additions at the highest rate resulted in a significant increase in bicarbonate-extractable and total soil P (0-5 cm depth). There was no effect of N additions on biomass production, nutrient uptake, or N enrichment of the peat during the two-year study. We observed no significant change in macrophyte species diversity or expansion of cattail in plots receiving nutrient additions during the two-year study. However, the decline of the Utricularia-periphyton mat (and the subsequent increase in Chara) in slough plots receiving 4.8 g P· m2· yr1 may serve as an early indicator of P enrichment in the Everglades.
Key Words: Chara, Cladium jamaicense, eutrophication, Florida Everglades, nitrogen, nutrient limitation, periphyton, phosphorous, slough communities, Typha domingensis.
Reproduced by permission
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