Nutrient and hydrology effects on soil respiration in a northern everglades marsh

Microbial respiration in peat and overlying plant litter, as influenced by water level and phosphorus; enrichment, was evaluated for an Everglades (Florida, USA) marsh ecosystem by measuring CO2 and CH4 release from soil-water microcosms. intact cores of peat, overlying plant litter, and surface water were collected at. seven locations in cattail (Typha domingensis Pers.) and sawgrass (Cladium jamaicense Crantz) stands along a phosphorus (P) enrichment gradient in Water Conservation Area 2A (WCA-2A). Each soil-water. microcosm was outfitted with a controlled Air circulation system whereby outflow gas-from the headspace could be analyzed for CO2 and CH4 to determine flux of C from the soil-Water column to the atmosphere. Gaseous C flux was determined for flooded conditions (10-cm water depth) and for water levels. of 0, 5, 10, and 15 cm. below the peat surface. Overall, decreasing water level resulted in significantly increased C flux, although rates were significantly higher under flooded conditions than under nonflooded, saturated-soil conditions, presumably due to O-2 availability associated with algal photosyntions, within the litter layer in the water column. Carbon flux decrease significantly for sites increasingly distant from the primary hydrologic and nutrient inflows to WCA-2A. The microcosm study demonstrated that the C turnover rate was significantly increased by accelerated nutrient loading to the marsh, and was further enhanced by decreasing Water level under drained conditions. Our -results also demonstrated that photosynthesis within the water column is a poteniially important regulator of C mineralization rate.in the litter layer