Climatic change effects on the physiology and growth of Pinusponderosa: expectations from simulation modeling

The TREGRO model was used to simulate the growth response of mature Pinusponderosa Dougl. ex Laws. to the interacting effects of changes in CO2 (+200 μL/L), temperature (+4 °C), and O3 (0.5×, 1×, and 2×ambient). Relative to simulated growth under the base-line climate in Corvallis, Oregon, elevated CO2 and temperature individually increased total-tree biomass gain by 29% and 13%, respectively, but when combined increased biomass gain by 49%. Ozone at all exposures reduced total-tree biomass gain by 1%, 19%, and 39%, respectively, as compared with simulated base-line conditions. Elevated CO2 increased photosynthesis and reduced stomatal conductance and partially offset growth reductions due to 2× O3. Elevated temperature, however, increased both photosynthesis and stomatal conductance and was less effective at mitigating growth reductions due to 2× O3. Growth at 2× O3 in elevated CO2 and temperature conditions had little effect on total-tree growth, but decreased fine-root growth by 61%. The simulated chan...