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EFFECTS OF ELEVATED CO2 AND TEMPERATURE ON THE RESPONSE OF PONDEROSA PINE TO OZONE: A SIMULATION ANALYSIS
Citation:
Tingey, D T., J A. Laurence, J C. Greene, W E. Hogsett, S. Brown, AND E H. Lee. EFFECTS OF ELEVATED CO2 AND TEMPERATURE ON THE RESPONSE OF PONDEROSA PINE TO OZONE: A SIMULATION ANALYSIS. Presented at 16th North American Forest Biology Workshop & the Western Forest Genetics Association 2000 Conference, Merida, Yucatan, Mexico, July 17-20, 2000.
Description:
Forests regulate numerous biogeochemical cycles, storing and cycling carbon, water, and nutrients, however, there is concern how climate change, elevated CO2 and tropospheric O3 will affect these processes. We investigated the potential impact of increased O3 in combination with projected climate and atmospheric CO2 concentrations on growth of Pinus ponderosa, at 7 sites in California, Oregon, and Washington, USA, using TREGRO, a process-based whole-tree growth model. The model provides a tool to study interactions among various factors and processes that give rise to synergistic responses. Simulated plant growth increased proportional to CO2 concentration, however, the magnitude of the growth increase varied among sites as other factors influenced response. Increasing air temperature (+1.3 C) increased growth at most sites. Elevated CO2 increased the temperature optimum for growth at 4 sites and decreased it at 2 sites. The annual biomass increment decreased with increasing O3 exposure. The differences in O3 sensitivity among sites is primarily controlled by differences in precipitation. Simulations indicate that increasing levels of tropospheric O3, changing climate and rising atmospheric CO2 can alter the C sequestrating potential of forests. Although increasing CO2 reduces O3 sensitivity, it does not eliminate the impact of O3; elevated CO2 would enhance C storage in forests more if O3 exposures were reduced, especially in more polluted sites. Although the greatest benefit in C storage will come from reducing O3 exposures in the most polluted sites, we must also consider those sites that have high inherent O3 sensitivity because of their mesic conditions. Limiting the increase of O3 levels in those areas will also increase C storage in forests. In contrast, C storage in other areas, that have a lower inherent O3, sensitivity would likely not be as impacted by increasing O3 exposures as the plants are climatically less sensitive to O3.