Temporal dynamics of allochthonous coarse particulate organic matter in a subtropical Atlantic rainforest Brazilian stream

Abstract

Allochthonous organic matter is a major energy source for headwater stream ecosystems. Therefore, examinations of how energy flows throughout these streams requires knowledge of mechanisms driving leaf input, retention and export. In this study we quantified the major input pathways and retention dynamics of coarse particulate organic matter (CPOM) in an Atlantic Rainforest stream in southern Brazil. We hypothesised that much of the temporal variability in the CPOM budget would be driven by precipitation, and thus we focus especially on the importance of vertical v. lateral input pathways, precipitation-driven inputs v. stocks, and composition of CPOM throughout 1 year. Most leaf litter entered the stream by the lateral input pathway (70.5gm–2month–1±108s.d.) compared with the vertical (32.4gm–2 month–1 ±17.5s.d.), and lateral input was correlated with precipitation and bank slope. In addition, torrential rainfall caused a net decrease in CPOM by reduction in the benthic stocks. Finally, six species represented 52.9% of total leaf input, where the most important (~25% of total input) was Schizolobium parahyba. Overall, this research confirms our prediction that the CPOM budget of this Atlantic Rainforest stream is driven in large part by precipitation.