Ecosystem-dependent driving factors of evapotranspiration in northern China

Evapotranspiration (ET) plays a crucial role for the water and energy balance, and carbon cycle, its accurate quantification is vital for ecohydrological research. The spatial and temporal heterogeneity of ET and its driving factors under four types of terrestrial ecosystems including forest, grassland, farmland and desert in northern China are studied using eddy flux data. It is found that the seasonal variation of ET in the four terrestrial ecosystems is obvious. All of them reach the highest value in summer while in winter is the lowest. In terms of inter-annual variation, deserts have the lowest ET, whereas little difference is observed in forest, grassland and farmland terrestrial ecosystems. Besides, the driving factors for ET are investigated using structural equation model. A distinctive pattern of differentiation for the dominant factors of ET is manifested in different ecosystems. In forest terrestrial ecosystems, ET is primarily driven by GPP, reflecting vegetation cover regulates water loss. In grassland ecosystems, ET is dominated by Rn, highlighting the central role of energy allocation. In farmland, ET is mainly controlled by Ta. In desert, VPD is the most dominant factor on ET, as atmospheric dryness significantly reduces ET by inhibiting Gs. The study reveals the dependency of ET changes on terrestrial ecosystem types, establishing the quantitative spectra of ET driving factors across multiple ecosystems in northern China, which provides important insights for research on water cycle dynamics and water resource management across different ecosystems. • ET dominant drivers: forest (GPP), grassland (Rn), farmland (Ta), desert (VPD). • SEM reveals direct and indirect pathways, clarifying ET heterogeneity across ecosystems. • First multi-ecosystem ET driver comparison in northern China, aiding water management.