Quantifying global change stressor effects on the rates and fates of terrestrial litter inputs in streams
Terrestrially-derived plant litter supports essential functions in streams, but litter inputs, processing rates, and fates of litter are currently affected by a variety of human-driven stressors. To aid management of river systems, research should focus on identifying stressors that affect detrital pathways and provide quantitative information on their effects. Although effects of stressors can change in space and time, generalizable frameworks can be constructed to characterize the effect size of stressors on detrital resources with consideration of biogeographic and other determining factors. I would like to stimulate discussion about developing such a framework, starting with quantifying the effects of single stressors, their interactive effects on litter processing rates, determining how stressors affect carbon fates, and identifying other factors that can amplify or reduce the effects of stressors on detrital resources. Stressor effects depend on whether processing is dominated by microbial or metazoan assemblages, a key component to include in a framework of stressor effects. I will provide data to be considered for this framework, based on experimental manipulations of nutrients and temperature, including the effects of these stressors in driving litter loss rates using whole stream experiments and litterbags, and quantification of microbial-driven vs metazoan pathways on carbon fates. I will also present an analysis of whether small scale measurements such as litterbags predict whole stream dynamics, which allows for extrapolation of results to larger scales. Development of a generalizable framework of the quantitative effects of stressors is essential for protection of stream ecosystem services that include the critical role of plant litter.