Site-specific apparent optimum air temperature for vegetation photosynthesis across the globe.

The apparent optimum air temperature for vegetation photosynthesis (T_opt) is a key temperature parameter in terrestrial ecosystem models estimating daily photosynthesis or gross primary production (GPP, g C/m²/day). To date, most models use biome-specific T_opt (T_opt-biome) parameter values. Given vegetation acclimation and adaptation to local climate, site-specific T_opt (T_opt-site) is needed to reduce uncertainties in estimating daily GPP across the scales from site to region and the globe. Previous studies have demonstrated using the Enhanced Vegetation Index (EVI) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) images and daytime air temperature data to estimate the T_opt-site at the eddy covariance tower sites. This study used MODIS-derived EVI and ERA5 climate data to estimate and generate global T_opt-site data products from 2000 to 2019. The T_opt-site of individual pixels within a biome has large variation, which clearly cannot be represented accurately by the widely used T_opt-biome. Therefore, using this global dataset of T_opt-site estimates might significantly affect GPP simulation in current ecosystem models. [ABSTRACT FROM AUTHOR]