Asymmetric environmental responses on evapotranspiration in Tibetan Plateau grassland

Evapotranspiration (ET) from the Tibetan Plateau (TP) grasslands plays a critical role in regulating water storage in the Asian Water Tower. However, the patterns, drivers, and responses of ET to climate change remain largely understudied due to limited observational data. This study integrated eddy covariance and long-term remote sensing data to examine the spatial patterns of ET and its drivers across the TP, comparing these patterns with those in other grassland ecosystems of the Northern Hemisphere. In the eastern TP, ET was primarily influenced by vapor pressure deficit and net radiation, whereas in the western TP, the impact of these two factors on the ET was significantly reduced. The regional differences were attributed to the unique energy-limited conditions in the eastern TP, which were driven by the East Asian monsoon and large-scale atmospheric circulation. In contrast, ET in other grassland ecosystems of the Northern Hemisphere, such as the North American Prairie and the Mongolian Plateau, was mainly controlled by water availability (e.g., precipitation and soil water content), similar to the western TP region. Under future climate warming, ET in the eastern TP is expected to increase significantly compared to other grasslands, particularly in the SSP5-8.5 scenario. This study revealed the distinct mechanisms regulating ET in TP grasslands and emphasized the need for further research on how grassland ET responds to global environmental changes.