Using Atmospheric oxygen to unravel biosphere CO2 exchange

The main reason for contemporary climate change is the increased concentration of carbon dioxide (CO2) in the atmosphere. To understand these rising concentrations, a thorough understanding of the global carbon cycle is needed. The land biosphere, is a global net carbon sink, taking up carbon from the atmosphere. It partly mitigates the increasing carbon emissions, and is an important part of the global carbon cycle, although it is still unknown how this its role as carbon sink will change in the future. The processes in the biosphere that take up or emit CO2 respectively emit or take up atmospheric oxygen (O2). This inverse coupling between CO2 and O2 is expressed as the exchange ratio (ER). Given that the ER is process-specific, it is possible to analyse the photosynthesis and respiration processes in the biosphere separately by measuring the flux of O2 and CO2. This research explores the applications of O2 measurements in the biosphere by examining the ER of specific processes, and combinations of processes in the biosphere. Lab experiments will reveal the variability of the ER on leaf- and plant scale under different environmental conditions, which will be used to interpret the variability of the ER above an ecosystem. This allows us to develop a clearer and more process-based understanding of the carbon cycle in the biosphere on leaf-, plant- and ecosystem scale.