Cascade effects of climate and vegetation influencing the spatial variation of evapotranspiration in China

Evapotranspiration (ET) is generally affected by climate and vegetation, but the main factor controlling spatial variation of ET largely varied with different regions. Clarifying the characteristics and dominant factor ET in China is essential for understanding the regional ecosystem water balance. This study quantitatively assessed the magnitude and spatial variations of ET in China's terrestrial ecosystems using data measured eddy covariance from 150 observation sites and investigated its underlying direct and indirect influencing tors. The results demonstrated that the ET of China's terrestrial ecosystems varied from 146.95 to 1125.33 with an average value of 551.00 +/- 204.12 mm. The ET showed a general increasing trend from the North South, aligning with the latitudinal patterns of water availability (mean annual precipitation (MAP)), energy conditions (mean annual net radiation (MARn), and mean annual temperature (MAT)). Compared to regions the same latitude, the North China Plain exhibited relatively higher ET because of the extensive cropland sites the area. Furthermore, significant positive linear correlations were found between ET and MAT in the majority ecosystems. However, a negative correlation of ET with MAT was observed in grasslands, which may attributed to inconsistent responses of ET to MAT on the Tibetan Plateau and Inner Mongolia. Fractional vegetation coverage (FVC) exhibited a more significant direct influence on ET than climate factors (MARn, and MAP). Nevertheless, climate factors not only exert a direct influence on ET but also have cascade effects affect FVC, thereby indirectly influencing the ET. When considering these cascade effects, MAP emerged as dominant driver of spatial variations in ET of China's terrestrial ecosystems. This study provides essential formation on variations of ET in China's terrestrial ecosystem and valuable insights for future explorations the adaptive mechanisms underlying spatial variations of ET.