Phosphorus enrichment affects litter decomposition, immobilization, and soil microbial phosphorus in wetland mesocosms

Like many wetland ecosystems, areas of the northern Everglades of Florida, USA, have been influenced by P eutrophication, Our objective was to determi ne if P enrichment of water influences the litter decomposition rate and nu trient immobilization by litter and, further, to determine the quantitative relationship of these responses across a range of P concentrations in surf ace water, in addition, we determined whether P additions rapidly elevated microbial biomass P in the soil. In order to isolate the effects of P enric hment, we placed bags containing cattail (Typha domengensis Crantz) and saw grass (Cladium jamaicense Pers.) litter into two sets of experimental chann els into which controlled inputs of five different phosphate concentrations were added continuously, After 1 yr of incubation, litter was analyzed for C, P, N, Cu, Ca, and K content. Loss of C at the end of 1 yr increased lin early with increasing average PO4 content in the channels with a similar sl ope for both species of litter, Immobilization caused an absolute increase in P content of the litter up to approximately ninefold across the range of water P concentrations, while immobilization of N, Ca, and K did not vary with water P concentrations. During decomposition, litter exhibited a net u ptake of Cu (a nutrient potentially limiting plant growth on peat soils). T he microbial biomass P was up to nine times higher in the surface soil of t he most enriched channel compared with the control, but this elevation in c oncentration was restricted to the upper 12 cm of soil.