Understanding how vegetation regulates water uptake under drought has received increasing attention; however, post-rainfall changes in plant water uptake processes remain inadequately understood, particularly in extreme arid desert environments. We investigated three sand-fixing species: Artemisia ordosica (A. ordosica) , Salix psammophila (S. psammophila) , and Caragana korshinskii (C. korshinskii ), following two rainfall events (6 mm/day and 11 mm/day). Soil water content (SWC) dynamics and corrected δD/δ 18 O coupled with the MixSIAR model were employed to explore soil infiltration and plant water uptake strategies on days 1, 3, and 5 post-rainfall (R1, R3, R5). Soil water infiltrated to 60–120 cm and > 200 cm depths after the 6 mm and 11 mm rainfall, respectively, via piston flow. All species primarily utilized water from 0–120 cm soil layers on R1 (65 ± 31% to 86 ± 24%). By R5, A. ordosica and S. psammophila increased water absorption from 0–60 cm and 120–200 cm layers, while C. korshinskii maintained a stable uptake strategy. These interspecific differences are attributed to varying SWC, dimorphic root systems, and drought response strategies. A. ordosica and C. korshinskii exhibit water-conservative strategies, whereas S. psammophila employs an opportunistic strategy, rapidly shifting water sources to sustain high consumption, enhancing its rainfall sensitivity. This study provides critical insights into desert plant adaptation mechanisms for future extreme drought and provides ecological restoration strategies in arid regions.
Zhang et al. (Sat,) studied this question.