Gross photosynthetic CO2 uptake is the single largest component of the global carbon cycle and a crucial variable for monitoring and understanding global biogeochemical cycles and fundamental ecosystem services. Nowadays routine measurements of the net biosphere-atmosphere CO2 exchange are conducted at the ecosystem scale in a large variety of ecosystem types across the globe. Gross photosynthetic and ecosystem respiratory fluxes are then typically inferred from the net CO2 exchange and used for benchmarking of terrestrial biosphere models or as backbones for upscaling exercises. Uncertainty in the responses of photosynthesis and respiration to the climate and environmental conditions is a major source of uncertainty in predictions of ecosystem-atmosphere feedbacks under climate change.
During the last decade, technological developments in field spectroscopy, isotope flux measurements and quantum cascade lasers have enabled alternative approaches for constraining ecosystem-scale photosynthesis and respiration.
In this session we aim at reviewing recent progress made with novel approaches of constraining ecosystem gross photosynthesis and respiration and at discussing their weaknesses and future steps required to reduce the uncertainty of present-day estimates. To this end we are seeking contributions that use emerging constrains to improve the ability to quantify respiration and photosynthesis processes at scales from leaf to ecosystem and global. Particularly welcome are studies reporting advancements and new developments in CO2 flux partitioning from eddy covariance data, the use of carbonyl sulfide, sun-induced fluorescence and stable isotopes approaches. Modelling studies which enhance our fundamental understanding of ecosystem-atmosphere CO2 exchange at global scale or make use of these emerging new constraints in data assimilation schemes are also welcome.