Predicting photosynthesis and transpiration responses to ozone: Decoupling modeled photosynthesis and stomatal conductance

Carbon dioxide and water exchange are typically coupled through the control of stomatal conductance, and the parameterization in many models often predict conductance based on photosynthesis values. Some environmental conditions, like exposure to high ozone (O₃) concentrations, alter photosynthesis independent of stomatal conductance, so models that couple these processes cannot accurately predict both.

The goals of this study were to test direct and indirect photosynthesis and stomatal conductance modifications based on O3 damage to tulip poplar (Liriodendron tulipifera) in a coupled Farquhar/Ball-Berry model. The same modifications were then tested in the Community Land Model (CLM) to determine the impacts on gross primary productivity (GPP) and transpiration at a constant O₃ concentration of 100 parts per billion (ppb).