Connecting the litterfall temporal dynamics and processing of coarse particulate organic matter in a tropical stream

Abstract

We collected leaf litter monthly and analysed how the temporal dynamics of litterfall affect the breakdown rates, microbial and fungal biomass and aquatic invertebrate community in a tropical stream in southern Brazil. The results showed that total annual litterfall varied over time and was negatively associated with rainfall. Litter fell mostly in the spring months, but other peaks occurred throughout the year. In all, 122 tree species were identified; however, only seven represented >70% of the total of leaf litter vertical input. Leaf decomposition was higher in February and April (wet, warm months) than during the wet season. Fungal biomass was high in decomposing leaves (460±28μgg–1 of ash-free dry mass, AFDM), with a maximum of 655μgg–1 AFDM in July. Microbial biomass in decomposing leaves was lower (326±27 nmol g–1 AFDM), with a maximum of 504 nmol g–1 AFDM in October. Monthly variability in the fungal and microbial biomass and aquatic invertebrate colonisation were associated with litter quality. The results suggested that litterfall is the result of regional environmental factors and characteristics of the riparian vegetation and that modifications in the quality, quantity and timing of the delivery of litter input to the stream affect activity in the decomposer community, which then affects monthly litter-breakdown rates.