Fluorescence Efficiency‐Derived Physiological Optimal Temperature Improving the Estimation of Photosynthesis

Abstract Terrestrial gross primary production (GPP) quantifies the rate of CO 2 fixation in ecosystems through photosynthesis. The optimal temperature ( T opt ) is one of fundamental determinants in the vegetation photosynthesis model (VPM) model that constrains the temperature response of light use efficiency (LUE) under changing environmental conditions. However, the VPM model uses the biome‐specific T opt without considering the spatial variation in T opt . Therefore, this study estimated the global optimal temperature ( T opt ) from the fluorescence efficiency (Φ F , a proxy of LUE) and adjusted the VPM model by using the spatially resolved T opt . Our results reported that Φ F ‐derived T opt is well consistent with LUE‐derived T opt . In addition, the improvement in R 2 reached up to 0.05 for sites with a difference between the biome‐specific T opt and Φ F ‐derived T opt larger than 5°C. Our results highlight the potential of the adjusted VPM model for studying the global carbon cycle and their responses to the future warming.