Primary roles of soil evaporation and vegetation in driving terrestrial evapotranspiration across global drylands.

Terrestrial evapotranspiration (ET) is a key variable in the global water cycle, notably affected by climate change and vegetation greening. However, its intrinsic driving modes and the ways through which driving factors influence it remain largely unexplored. Here, we quantified the internal and external drivers behind the spatiotemporal variability of ET across global drylands at seasonal and annual temporal scales and component levels based on pixel-by-pixel partial correlation and ridge regression analyses. The results show that vegetation predominantly drives changes in ET, plant canopy transpiration (Ec), evaporation of precipitation intercepted by vegetation (Ei), and soil evaporation (Es) in most regions of the global drylands. This pattern persisted on a seasonal scale. The contribution analysis revealed that vegetation had the strongest influence and the largest contribution to ET variation. Temperature was the climatic factor that contributed the most to the driving process of ET change and was significantly higher than the other climatic factors. Among the components of ET, Es was the predominant constituent part to ET, exerting a strong control on its variability. Its absolute contribution (60.3 %) to this variability was approximately twice that of Ec. Our findings highlight the crucial role of Es and vegetation in driving ET across drylands and the potentially important moderating role of Es amid increasing water resource turbulence due to ongoing vegetation greening.