The Phenology of Leaf Litter Decomposition in Aquatic and Terrestrial Compartments of Headwater Catchments

AbstractThe decomposition of leaf litter is a major ecological process in terrestrial and aquatic ecosystems worldwide. Leaf litter generally enters ecosystems in annual pulses and is subsequently decomposed across many seasons. Yet investigations into this process are rarely conducted in parallel in aquatic and terrestrial ecosystems and over the full year, limiting our understanding of its phenological context across the blue-green interface. Here, we assessed the decomposition of three litter species by microorganisms and macroinvertebrates in temperate streams and forests across a year using repeated litterbag assays at 6-week intervals. We observed higher decomposition rates in summer in most combinations of ecosystem, litter species, and decomposer type, indicating positive effects of higher temperatures and low standing crops of labile litter. Furthermore, forests showed lower decomposition rates than streams. Last, we found that the relative litter species effects on both microbial and invertebrate decomposition were consistent across environments, suggesting that the fast microbial activity decreased the quality of the remaining tissue mass for invertebrates. Overall, our work places known drivers of the decomposition of leaf litter into a phenological context, providing evidence that changes in the timing or strength of these drivers could drive temporal shifts of this central ecological process.