Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 11/7/2008
Publication Date: 12/23/2008
Citation: Manzoni, S., Fay, P.A., Katul, G., Polley, H.W., Porporato, A. 2008. Modeling plant-atmosphere carbon and water fluxes along a CO2 gradient. In: Proceedings of the EOS Trans. American Geophysical Union. December 15-19, 2008, San Francisco, CA. Paper No. B43A-0417.
Technical Abstract: At short time scales (hourly to daily), plant photosynthesis and transpiration respond nonlinearly to atmospheric CO2 concentration and vapor pressure deficit, depending on plant water status and thus soil moisture. Modeling vegetation and soil responses to different values of CO2 at multiple time scales is critical to predict ecosystem functioning under expected future enriched CO2 conditions, as well as to understand vegetation dynamics under subambient CO2 concentrations such as occurred during pre-industrial and past inter-glacial periods. Here we present a general model describing the effects of CO2 concentrations on carbon assimilation and transpiration rates at the half-hourly time scale. The proposed model embeds sub-units describing water and carbon mass balances for each component of the soil-plant-atmosphere continuum, as well as a simplified plant-atmosphere gas exchange scheme. The model is applied to study carbon and water fluxes in plots containing grassland vegetation on soils from three contrasting soil series exposed to a CO2 concentration gradient (250 to 500 µL/L) in the Lysimeter CO2 Gradient experiment (LYCOG). The model allows to compute short-term fluxes of carbon and water in that system under the current experimental conditions, as well as to simulate the effects of varying precipitation patterns and solar radiation on plant productivity.