Terrestrial gross primary productivity (GPP) plays an important role in terrestrial-atmosphere system carbon cycles and contributes to human welfare, as it is the basis for food, fiber, and wood production (Beer et al., 2010). Although rising atmospheric CO 2 has increased GPP in many regions of the world during the last several decades (Schimel et al., 2015;Tharammal et al., 2019), factors such as drought, heat stress, and nutrient limitations decrease GPP, and their effects are poorly understood at regional scale due to