Effects of different surface water flow frequencies on water use characteristics of Tamarix ramosissima in the hinterland of the Taklamakan Desert

Tamarix ramosissima is a dominant species in desert ecosystems and an ecological barrier species in arid areas, playing a crucial role in stabilizing dunes and preventing desertification. In this study, river water, groundwater, soil water, and T. ramosissima individual samples were collected from three sites in July and October 2023 at the Daliyaboyi Oasis located at the tail of the Kriya River in the hinterland of the Taklamakan Desert. The three sites are referred to as the center (SE), west (SW), and north (SN) sites within the Daliyaboyi Oasis, and each experienced different flood frequencies. The SE site experienced flooding in July and October, the SW site experienced flooding only in July, and the SN site experienced no flooding in July or October. The spatial and temporal variation in hydrogen and oxygen stable isotopes and line-conditional excess (lc-excess) in water and plant samples were analyzed, and the potential changes in water use of T. ramosissima were analyzed by the hydrogen and oxygen stable isotope and MixSIAR model. The findings indicated that the slope of SWL at the SE, SW, and SN sites was higher in July (6.77, 6.42, and 3.05, respectively) than in October (7.37, 3.30, and 2.14, respectively). The lc-excess value of the SE site did not exhibit seasonal changes; only the lc-excess values of soil water in SW and SN sites showed seasonal changes. MixSIAR results indicated frequent flood events at the SE site, with relatively constant proportions of water source utilization by T. ramosissima in July and October. In addition, shallow soil water (0–60 cm) and deeper soil water (60–80 cm) were the main water sources of T. ramosissima at SE. The SN site was slightly influenced by surface water, resulting in statistically non-significant changes in the water source utilization by T. ramosissima. Indeed, deep soil water (60–200 cm) and groundwater were the sources of water for T. ramosissima at this site. In contrast with October, the SW site experienced flood events in July, resulting in the utilization of water by T. ramosissima from the shallow soil (0–60 cm) and deep soil (60–280 cm) in July and October, respectively. Different surface water flow patterns led to different water use characteristics of T. ramosissima, which further demonstrated that T. ramosissima has high resilience and ecological plasticity. This work provides a useful reference for the implementation of effective ecological water transport measures in the Daliyaboyi Oasis and similar arid habitats.