Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 9/30/2009
Publication Date: 12/31/2009
Citation: Manzoni, S., Fay, P.A., Polley, H.W., Palmroth, S., Katul, G., Porporato, A. 2009. Optimal leaf water use drives ecosystem water and carbon fluxes in a changing environment. In: Proceedings of the EOS Trans. American Geophysical Union, San Francisco, California. Paper No. 90(52):H11l-02. Interpretive Summary:
Technical Abstract: Canopy water and carbon exchange rates are controlled by leaf-level adjustment of stomatal aperture and photosynthetic capacity. Both leaf-level stomatal conductance and the leaf photosynthetic machinery respond nonlinearly to soil water availability, atmospheric CO2 concentration, and other environmental variables. Here we propose and test a canopy-scale coupled soil-vegetation-atmosphere model based on leaf-level optimality principles and its two-way interaction with its immediate microclimate. We assume that stomatal conductance is optimized so as to maximize the leaf-level net carbon gain, interpreted as photosynthesis minus the costs associated with water losses through leaf transpiration. This optimality principle is shown to describe a wealth of available leaf-level gas exchange data under different soil water availabilities and atmospheric conditions. The leaf-level optimality model is scaled up to the canopy-level by accounting for light and wind speed profiles within the canopy, as well as including a new model of soil-to-leaf water flow. The coupled model is applied to study the responses of a grassland ecosystem to different rainfall patterns and atmospheric CO2 concentrations.