Variations in vegetation evapotranspiration affect water yield in high-altitude areas

Abstract. Global mountains and plateaus are the main water-producing areas on land. However, under the influence of climate change, the distribution of vegetation and the way water is utilized in these areas have undergone significant changes. As such, understanding the effects of evapotranspiration from high-altitude vegetation on precipitation and runoff is vital in addressing the uncertainties and challenges posed by climate change. Between 2018 and 2022, we conducted research in the northeastern Qinghai-Tibet Plateau, collecting data on precipitation, soil water, and Picea crassifolia xylem water to quantify the impact of vegetation transpiration and recirculated water vapor on precipitation. Our findings indicate that transpiration from vegetation accounts for the largest share of evapotranspiration within the entire forest ecosystem, averaging 57 %. Therefore, vegetation transpiration is the decisive factor in determining the water yield of inland high-altitude areas. The average contribution of local evapotranspiration to precipitation reaches 28 %, making it the main driver behind the increase in precipitation at high altitudes. The warming of global temperatures and human activities are likely to induce shifts in the distribution areas and evapotranspiration regimes of alpine vegetation, potentially altering water resource patterns in the basin. It is necessary to actively adapt to the changes in water resources in the inland river basin.