Influence of fluctuation of groundwater depth on the water use characteristics of Tamarix ramosissima at the tail of the Kriya River

The Daliyaboyi Oasis at the tail of the Keriya River in the Tarim Basin, China. Groundwater is an important water source for riparian forest in arid region. However, studies on the response of riparian forest to fluctuation of groundwater depths are still limited. This study used stable isotope method combined with the MixSIAR model to examine the inter-annual influence of the fluctuations of groundwater depth on water use of T. ramosissima at the Daliyaboyi Oasis. The results showed that the fluctuations of groundwater depth decreased from 5.20 m in 2018–1.68 m in 2023 at the sampling period. Meanwhile, the surface soil water content (0–100 cm) showed a significant increasing trend. Accordingly, T. ramosissima switched its main water sources from deep soil water to shallow water. According to the results of MixSIAR model, in 2018–2020, T. ramosissima mainly used deep soil water, with the uptake proportions of 39.12 ± 0.01 %, 44.23 ± 0.02 %, and 43.21 ± 0.02 %, respectively. In 2022–2023, T. ramosissima mainly used shallow soil water, with the uptake proportions of 40.16 ± 0.01 %, and 36.44 ± 0.03 %, respectively. Unexpectedly, the uptake proportion of T. ramosissima to groundwater was relatively constant, with the value ranged from 28.27–37.54 %, did not change obviously with the decreasing of groundwater depth. This study provides insights into the resistance of water use of the desert riparian forest to the fluctuation of groundwater depths. • Hydrogen and oxygen stable isotopes were used to assess the water use characteristics of T. ramosissima. • The fluctuations of groundwater depth decreased from 5.20 m in 2018–1.68 m in 2023 at the sampling period. • T. ramosissima switched its main water sources from deep soil water in 2018–2020 to shallow water water in 2022–2023. • The uptake proportion of T. ramosissima to groundwater was relatively constant .