We investigate the ecophysiological processes in plants that determine the fluxes of water, nitrogen and carbon in ecosystems. With our research we seek to understand how plants function in the context of their environment and to reveal how plants shape the provision of ecosystem goods and services in a changing environment. While ecophysiological processes in plants are at the heart of our interest, we link our investigations to research in agriculture, biogeochemistry and earth-system sciences. Key tools for our research are stable carbon, nitrogen, oxygen and hydrogen isotopes that we use in their natural abundance or as tracers to characterize ecophysiological processes and biogeochemical cycles. Within this context, our research currently focusses on four themes: