Ecosystem respiration is a fundamental flux in the global carbon cycle, yet its full interpretation remains constrained by the incomplete consideration of the counterflow of atmospheric oxygen (O₂) into soils—the so-called "forgotten half" of the respiratory process. The respiration quotient (RQ = CO₂ produced / O₂ consumed) offers a unique, integrative signal that reflects not only microbial metabolic activity but also the interplay of biotic processes, abiotic gas transport, and redox dynamics across scales—from microbial communities to entire ecosystems. RQ values deviate in many cases from the simple expectations of RQ ~1.0, indicating the influence of diverse processes such as fermentation, nitrification, mineral weathering, and incomplete mixing.
Despite its potential, RQ remains underutilized in many fields of research from the microscale to large-scale ecological and atmospheric studies due to the technical challenges of high-precision O₂ measurements— which is necessary especially given the high atmospheric background (20.95%). To overcome this, we want to bring together people and ideas of different fields who try to tackle this challenge and answer questions related to the CO₂ - O₂ exchange of the living but also non-living environment.
We invite atmospheric scientists, microbial ecologists, and biogeochemists to join this emerging frontier: where the subtle interplay of CO₂ and O₂ fluxes reveals the hidden logic of ecosystem respiration—from the microscale of microbial metabolism to the macroscale of global carbon budgets. This session lays the foundation for a new generation of integrated, process-based monitoring networks that connect the biosphere’s breath to the atmosphere’s pulse.