Spatial variations of rain-use efficiency along a climate gradient on the Tibetan Plateau: A satellite-based analysis

Understanding the spatial relationship between rain-use efficiency (RUE) and climate conditions is crucial for predicting the steady-state responses of an ecosystem to climate variations. We clarified the spatial variations of RUE in different ecosystems along both mean annual precipitation (MAP) and mean annual temperature (MAT) gradients in the Three-river Headwaters Region (THR) of China. RUE displayed a unimodal pattern along a MAP gradient across different ecosystems, with a higher value in forest, shrub, and less-arid alpine meadow than in alpine steppe, alpine talus vegetation, and more-arid alpine meadow. RUE followed an increasing trend along the MAT gradient both in a given ecosystem and across various ecosystems. The varying maximum RUE (RUEmax) with temperature suggested that no common spatial RUEmax existed across different ecosystems in the driest pixels. With the mutual interference between precipitation and temperature excluded, RUE increased both with precipitation at a given temperature level and with temperature at a given precipitation level in cold and dry ecosystems, while RUE probably decreased both with precipitation at a given temperature level and with temperature at a given precipitation level in warm and humid ecosystems. Our study illuminates the response of RUE to climate variations in alpine areas based on the spatial model, aiming to improve our understanding of the interactions between vegetation and climate conditions and the potential trade-offs between the ecosystem’s carbon and water.