Nutrient enrichment overwhelms diversity effects in leaf decomposition by stream fungi

Mass losses of oak leaves were studied in microcosms, where numbers of aquatic hyphomycete species (1-5) and nutrient concentrations (2 levels each of N, P, and Ca) were varied. Species numbers, species identities, N, P and N x P interactions all had significant effects on leaf mass loss, but the magnitude of the effect was greater for N and P than for species numbers. Mass loss in multicultures was greater than predicted from average contributions of the component species in single cultures. This may have been due to sampling effects or niche complementarity.