Aim of the Deliverable was to produce a Manuscript on impacts of climate change on ecosystem functioning under Task 5.6.Impact of freshwater biodiversity change on ecosystem function (European, local scale).
The first manuscript summarizes results from a long-tern study of the relationship between phytoplankton biodiversity and ecosystem functioning. We present models of ecosystem functions- algal biomass and nitrogen and phosphorous resource use efficiency, linking seasonal variability in ecosystem functioning to that in various physical, chemical, and diversity related drivers. Our study indicates, that throughout the seasons, phytoplankton biomass and nitrogen resource use efficiency are mainly linked to the diversity of phytoplankton communities. In contrast, resource supply determines the phosphorous use efficiency, except for spring with species evenness as the central driving factor. Overall, an increase in species evenness- regardless whether taxonomic or functional, is accompanied with a decrease in ecosystem functioning. Further, the shape of the ecosystem response to a particular driver and the temporal patterns in drivers’ relative importance are shown to manifest larger variability across seasons, than across ecosystem functions.
The second manuscript summarizes results from standardized and comprehensive field experiments conducted in streams across geographical regions. The presented data set reveals a remarkable convergence not only of litter decomposition rate but also of fungal decomposer and detritivore dynamics across climatic zones when data are normalized for temperature. This is an important advance towards a unified quantitative model of decomposer dynamics, litter decomposition as a central biogeochemical process, and organic matter turnover in stream networks in general. Such syntheses are essential given the recently discovered, unexpectedly large significance of streams in the global carbon cycle, in which particulate organic matter dynamics are not explicitly considered.