Water use strategies and water conservation in Picea schrenkiana forests in the Kashi River Basin, China

The Kashi River Basin is located in northwestern Xinjiang, China. Using stable isotope techniques and incorporating the MixSIAR model, we studied the main water sources of Picea schrenkiana during the growing season. We estimated the evaporation loss of soil and river water using the Craig-Gordon and Rayleigh Fractionation models, respectively, to compare their evaporation loss and explore the reasons for these differences. The results showed that (1) in spring 2024, Picea schrenkiana mainly utilized 0–60 cm of soil water; the utilization rate of each layer was 20.5 %, 21.0 %, and 20.6 %, respectively; in summer 2024, 0–40 cm of soil water was utilized, with the utilization rate of each layer reaching 25.1 % and 21.1 %, respectively; and in autumn 2024, 0–20 cm of soil water was utilized and the rate rose to 29.6 %. (2) The evaporation loss of soil water was lower than that of river water during the same period. In the summer of 2024, the evaporation loss of river water was 60 %, while the evaporation loss of soil water from 0–20 cm was the largest, only 36.6 %, reflecting the function of Picea schrenkiana forests to contain water. This study provides a reference for vegetation protection and management in the region as well as its ecological benefits. • The main water absorption depth of Picea schrenkiana in different seasons is 0–60 cm. • Picea schrenkiana flexibly switches water sources to cope with seasonal changes in water. • Evaporation losses from soil water are less than evaporation losses from river water. • Small evaporation loss of soil water due to water conservation role of Picea schrenkiana.