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The water cycle in the soil‐plant‐atmosphere continuum is an important element of hydrological and ecological studies, and differences in the composition characteristics of hydrogen and oxygen stable isotopes in different water bodies can indicate water cycling processes. In this study, hydrogen and oxygen isotopes of precipitation, soil water and plant water samples had been collected in the subalpine scrubland of the Qilian Mountains from May to October 2019. The Craig‐Gordon model, the isotopic steady‐state (ISS) assumption, the Keeling Plot model and the two‐source mixing model were used to analyse the stable isotope compositions of different water bodies, the stable isotope characteristics of water vapour of soil evaporation and plant transpiration and the variation of evapotranspiration in the SPAC of the subalpine scrubland. The results showed that plant transpiration (FT) contributed 87.28% and 86.95% to evapotranspiration and soil evaporation (FE) contributed 12.72% and 13.05% to evapotranspiration in the growing season on semi‐sunny and semi‐shaded aspects, respectively, indicating that evapotranspiration in the subalpine scrubland mainly came from the transpiration of scrubland plants. In the early of the growing season (May–June), due to the rapid expansion of plant leaves, the contribution of transpiration to evapotranspiration was at a high level, which intensified transpiration and led to a gradual increase of the transpiration contribution. In the middle of the growing season (July–August), owing to better conditions of rain and heat that made plants grow vigorously, plant transpiration made the highest contribution to evapotranspiration more than 90%, which caused to an overwhelming contribution of plant transpiration to evapotranspiration. In the later of growing season (September to October), the contribution of plant transpiration to evapotranspiration decreased significantly while that of soil evaporation increased, which was because plant photosynthesis and respiration gradually declined for losing their leaves of scrub plants and the relative atmospheric humidity was lower. [ABSTRACT FROM AUTHOR]

Stable isotopes of precipitation play an important role in understanding hydrological and climatic processes of arid inland river basins. In order to better understand the difference of regional water cycle and precipitation patterns, precipitation samples were collected in Shiyang River Basin from June 2018 to May 2020, and spatial and temporal variation characteristics of stable isotopes in precipitation and their relationships with meteorological factors were discussed. The results showed that stable isotopes in precipitation showed seasonal variation characteristics, that δ2H and δ18O values were higher in summer and autumn and lower in winter and spring, and d-excess values were higher in spring and autumn and lower in winter and summer. Slopes and intercepts of the local meteoric water lines gradually increased with elevation increasing. δ18O significantly showed a positive correlation with temperature but a negative correlation with precipitation in summer. Contrary to below 15 hPa, δ18O significantly showed a negative correlation with water vapor pressure above 15 hPa. Due to the influence of meteorological factors, there are significant differences in stable isotopes of precipitation in arid inland river basins, which were more influenced by local moisture recycling in upstream area but by below-cloud secondary evaporation in mid-downstream area. [ABSTRACT FROM AUTHOR]