Decomposition and CO2 evolution from standing litter of the emergent macrophyte Erianthus giganteus

Decomposition of standing litter of the emergent macrophyte Erianthus gigan teus (plumegrass) was quantified in a small freshwater wetland in Alabama, USA. Living green shoots off. giganteus were tagged and periodically retrie ved for determination of leaf and culm mass loss, litter-associated fungal biomass (ergosterol), and nitrogen and phosphorus concentrations. Laborator y studies were also conducted to examine the effects of plant litter moistu re content and temperature on rates of CO2 evolution from plant litter. Cul m and leaf material lost 25 and 32% AFDM, respectively, during plant senesc ence and early litter decay. Fungal biomass, as determined by ergosterol co ncentrations, increased significantly in both leaf and culm litter during d ecomposition, with maximum biomass accounting for 3.7 and 6.7% of the total detrital weight in culm and leaf litter, respectively. Spatial differences in fungal biomass were observed along the culm axis, with upper regions of the culm accumulating significantly greater amounts of fungal mass than ba sal regions (p < 0.01, ANOVA). Rates of CO2 evolution from bath leaf and cu lm litter increased rapidly after wetting (0 to 76 mu g CO2-C g(-1) AFDM h( -1) within 5 min). In addition, rates of CO2 evolution from water saturated culms increased exponentially as the temperature was increased from 10 to 30 degrees C. These results provide evidence that considerable microbial co lonization and mineralization of standing emergent macrophyte litter can oc cur before collapse of senescent shoot material to the water and sediment s urface.