Ecophysiological responses of Quercus gilva, endangered species and Q. glauca to long-term exposure to elevated CO2concentration and temperature

The physiological effects of elevated CO₂ concentration and temperature were examined for Quercus gilva and Q. glauca grown under control (ambient CO₂ and temperature) and treatment (elevated CO₂ and temperature) conditions for 39 months. The objective of the study was to measure the long-term responses, in physiological parameters, of two oaks species exposed to elevated CO₂ and temperature. The photosynthetic rate of Q. gilva was found to be decreased, but that of Q. glauca was not significantly affected, after long-term exposure to elevated CO₂ and temperature. Stomatal conductance of Q. glauca was reduced by 21.7%, but that of Q. gilva was not significantly affected, by long-term exposure to CO₂ and temperature. However, the transpiration rate of the two oak species decreased. Water use efficiency of Q. gilva was not significantly affected by elevated CO₂ and temperature, while that of Q. glauca was increased by 56.6%. The leaves of Q. gilva grown under treatment conditions had an increased C:N ratio due to their reduced nitrogen content, while those of Q. glauca were not significantly affected by long-term exposure to elevated CO₂ and temperature. These results suggest that the long-term responses to elevated CO₂ and temperature between Q. gilva and Q. glauca are different, and that Q. gilva, the endangered species, is more sensitive to elevated CO₂ and temperature than Q. glauca.