The goal of this project is to investigate processes that control the exchange of oxygen isotopes (18O and 16O) in CO2 and H2O between terrestrial vegetation and the atmosphere. Soybean and corn will be used as model systems for C3 and C4 plants. Tunable diode laser absorption spectroscopy will be combined with the micrometeorological methods to provide simultaneous, near-continuous measurement of isotopomer mixing ratios and isotopic fluxes of CO2 and water vapor, and 18O discrimination factors at the ecosystem scale.
The ability to determine the ecosystem-scale 18O discrimination is essential to a number of fundamental science questions relevant to atmospheric carbon budget and ecosystem processes. The broader impacts of the proposed activity include the acquisition of unique datasets for validation of atmospheric carbon budget models. The innovative research methods will enhance the capacity of the global carbon and energy flux observational network and foster collaboration between university scientists and engineers in a private industry. The new knowledge gained during the project will be transferred to the greater scientific community through a special conference session and training of undergraduate and graduate students. Finally, the overall strategy on the coupled exchanges of CO2 and water through the 18O isotopes should open a new dimension for investigating the carbon and water cycles in a truly integrated manner.
