Microbial colonisation and litter decomposition in a Cerrado stream are limited by low dissolved nutrient concentrations

Litter decomposition in the streams of the Brazilian Cerrado (Savannah) is generally slow. In this study, we tested the hypothesis that leaf litter decomposition is limited by low dissolved nutrient availability. We measured the decomposition of the litter of the riparian species Protium heptaphyllum in a local stream under nutrient enrichment promoted by nutrient-diffusing substrates (nutrient-enriched treatment; N and P), and under control conditions (no added nutrients). Leaves were enclosed in fine (0.5 mm) mesh bags and immersed in the stream. Replicate samples were retrieved periodically over 56 days. At the end of the experiment, leaf mass loss, associated microbial biomass (ATP and ergosterol) and fungal sporulation rates were significantly higher in nutrient-enriched bags than in control bags. These results suggest that litter decomposition in certain Cerrado streams is partially limited by the low availability of dissolved nutrients.