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°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 CO(2) assimilation rates to T (leaf)), responses of biochemical limitations and diffusion limitations in gross CO(2) 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.