Contributions of fungi to carbon flow and nutrient cycling from standing dead Typha angustifolia leaf litter in a temperate freshwater marsh

Standing dead plant litter often constitutes a large fraction of the detritus in many freshwater marshes and lake littoral habitats. Despite this evidence, microbial decay processes in standing litter and its contribution to wetland carbon and nutrient cycling have rarely been quantified. We examined the contribution of fungi to carbon flow and nutrient cycling from Typha angustifolia during senescence and standing litter decomposition. Naturally standing Typha leaves were collected in August and then periodically over 1 yr. We quantified losses in leaf carbon (C), fungal biomass, and fungal production rates and constructed a partial budget estimating C flow into fungal decomposers. Additionally, we determined leaf litter N and P concentrations to assess the effect of fungi on detrital nutrient dynamics. Significant losses in leaf C occurred during plant senescence and standing litter decay (similar to 55%). Fungal biomass increased during litter decay, reaching a maximum of 106 +/- 7 mg C g(-1) detrital C. Cumulative fungal production totaled 123 mg C g(-1) initial detrital C, indicating that 22% of the Typha leaf C lost was assimilated into fungal biomass. Fungi also transformed and immobilized nutrients within Typha leaves, with fungal N and P accounting for > 50% of the total detrital N and P during later stages of leaf decay. Significant transformation and decomposition of emergent macrophyte litter occurs during the standing dead phase, and a large portion of the plant C and nutrients are channeled into and through fungal decomposers.