Thermal Acclimation of Foliar Carbon Metabolism in Pinus taiwanensis Along an Elevational Gradient

Climate change could negatively alter plant ecosystems if rising temperatures exceed optimal conditions for obtaining carbon. The acclimation of plants to higher temperatures could mitigate this effect, but the potential of subtropical forests to acclimate still requires elucidation. We used space-for-time substitution to determine the photosynthetic and respiratory-temperature response curves, optimal temperature of photosynthesis (<i>T</i> _opt), photosynthetic rate at <i>T</i> _opt, temperature sensitivity (<i>Q</i> ₁₀), and the rate of respiration at a standard temperature of 25°C (<i>R</i> ₂₅) for <i>Pinus taiwanensis</i> at five elevations (1200, 1400, 1600, 1800, and 2000 m) in two seasons (summer and winter) in the Wuyi Mountains in China. The response of photosynthesis in <i>P. taiwanensis</i> leaves to temperature at the five elevations followed parabolic curves, and the response of respiration to temperature increased with temperature. <i>T</i> _opt was higher in summer than winter at each elevation and decreased significantly with increasing elevation. <i>Q</i> ₁₀ decreased significantly with increasing elevation in summer but not winter. These results showed a strong thermal acclimation of foliar photosynthesis and respiration to current temperatures across elevations and seasons, and that <i>R</i> ₂₅ increased significantly with elevation and were higher in winter than summer at each elevation indicating that the global warming can decrease <i>R</i> _25. These results strongly suggest that this thermal acclimation will likely occur in the coming decades under climate change, so the increase in respiration rates of <i>P. taiwanensis</i> in response to climatic warming may be smaller than predicted and thus may not increase atmospheric CO₂ concentrations.