Evaluation of gross primary production (GPP) variability over several ecosystems in Switzerland using sun-induced chlorophyll fluorescence derived from APEX data

Plant photosynthesis mediates about 60Gt of the carbon uptake by vegetated ecosystems and is considered to be a critical component of the terrestrial carbon cycle. Photosynthesis is, however, a highly adaptive process and lack of knowledge on its dynamic causes uncertainties in current carbon budgets. New remote sensing approaches allow measuring the chlorophyll fluorescence signal (FS) and hold the potential to directly assess ecosystem photosynthesis and related carbon assimilation rates (i.e., gross primary production (GPP)). This study provides one of the first spatial investigations of GPP at local/regional scale. FS was retrieved from data of the new imaging spectrometer APEX (Airborne Prism EXperiment) and used to model GPP. Spatial variations of GPP were investigated for five major ecosystems in Switzerland. Results of this study are considered as important, e.g., for the development of ESA´s (European Space Agency) FLEX (FLuorescence Explorer) mission, for investigating functional ecosystem responses to environmental properties, or for evaluating common ecosystem monitoring approaches (e.g., eddy flux tower).