Acclimation of Foliar Respiration and Photosynthesis in Response to Experimental Warming in a Temperate Steppe in Northern China

Background: Thermal acclimation of foliar respiration and photosynthesis is critical for projection of changes in carbon exchange of terrestrial ecosystems under global warming. Methodology/Principal Findings: A field manipulative experiment was conducted to elevate foliar temperature (T-leaf) by 2.07 degrees C in a temperate steppe in northern China. R-d/T-leaf curves (responses of dark respiration to T-leaf), A(n)/T-leaf curves (responses of light-saturated net CO2 assimilation rates to T-leaf), responses of biochemical limitations and diffusion limitations in gross CO2 assimilation rates (A(g)) to T-leaf, and foliar nitrogen (N) concentration in Stipa krylovii Roshev. were measured in 2010 (a dry year) and 2011 (a wet year). Significant thermal acclimation of R-d to 6-year experimental warming was found. However, A(n) had a limited ability to acclimate to a warmer climate regime. Thermal acclimation of R-d was associated with not only the direct effects of warming, but also the changes in foliar N concentration induced by warming. Conclusions/Significance: Warming decreased the temperature sensitivity (Q(10)) of the response of R-d/A(g) ratio to T-leaf. Our findings may have important implications for improving ecosystem models in simulating carbon cycles and advancing understanding on the interactions between climate change and ecosystem functions.