Final Activity Report Summary - ISIS (Isolating and investigating the components of biosphere - atmosphere gas exchange with process-based models and measurements of stable isotopes)
Research during my Marie Curie International fellowship has focused on the coupled biogeochemical cycles of carbon and water in terrestrial ecosystems. I have combined measurements and modelling of a range of tracers that each yield unique constraints on terrestrial gas exchange. As main analytical tool, I developed a process-based multi-tracer model of ecosystem gas exchange (CO2, O2, water, and their carbon and oxygen isotope signatures).
The model explicitly includes multi-layer foliage gas exchange, depth-resolved soil diffusion and an interactive canopy air space. The latter is crucial for describing the feedbacks between the isotopic signatures of canopy air and those of leaf and soil gas exchange. I applied the model to demonstrate the importance of non-steady state leaf water enrichment and nocturnal stomatal conductance on the oxygen isotope signatures of CO2 and water at the ecosystem scale.
Furthermore, analysing observed oxygen isotope signatures of soil CO2 fluxes, I proposed previously unknown effects of carbonic anhydrase activity in a forest soil. These effects can lead to potentially large shifts in the oxygen isotopic signatures of CO2 and water fluxes, particularly from tropical and boreal ecosystems. This has substantial implications for estimating ecosystem to global carbon and water fluxes from atmospheric trace gas measurements.
I also showed how regional water sources affected ecosystem water pools and fluxes during the 'flood of the century' across Europe in 2002. In addition, I developed a new method to link long-term changes in ecosystem water use efficiency to the carbon isotope composition of plant material, illustrating the sensitivity of their coupling to changing climatic conditions.
The model explicitly includes multi-layer foliage gas exchange, depth-resolved soil diffusion and an interactive canopy air space. The latter is crucial for describing the feedbacks between the isotopic signatures of canopy air and those of leaf and soil gas exchange. I applied the model to demonstrate the importance of non-steady state leaf water enrichment and nocturnal stomatal conductance on the oxygen isotope signatures of CO2 and water at the ecosystem scale.
Furthermore, analysing observed oxygen isotope signatures of soil CO2 fluxes, I proposed previously unknown effects of carbonic anhydrase activity in a forest soil. These effects can lead to potentially large shifts in the oxygen isotopic signatures of CO2 and water fluxes, particularly from tropical and boreal ecosystems. This has substantial implications for estimating ecosystem to global carbon and water fluxes from atmospheric trace gas measurements.
I also showed how regional water sources affected ecosystem water pools and fluxes during the 'flood of the century' across Europe in 2002. In addition, I developed a new method to link long-term changes in ecosystem water use efficiency to the carbon isotope composition of plant material, illustrating the sensitivity of their coupling to changing climatic conditions.