Salix psammophila and Caragana korshinskii are pioneer species used for revegetating farmlands on the Loess Plateau. Understanding the water-use strategies and physiological characteristics of these two species are important for evaluating their adaptability in water-limited ecosystems. We used stable isotopes (D and ¹⁸O), physiological parameters (e.g. midday and predawn leaf water potential and stomatal conductance (ψ_md, ψ_pd and g_s, respectively)) and foliar δ¹³C to analyse water sources, isohydric/anisohydric behaviour, and water-use efficiency (WUE), respectively, of these two shrub species. Our results show that S. psammophila relied on water (mean 60%) from the intermediate soil layer (30-80 cm from the surface) during the dry period (May and June), while C. korshinskii relied on water from the deep soil layer (80-100 cm) (mean 52%). Both species shifted to using water from the shallow layer (0-30 cm) during the wet period (July and August) (mean 61% for S. psammophila and 51% for C. korshinskii). These root water uptake patterns are consistent with C. korshinskii’s physiological performance, which in turn is consistent with a description that C. korshinskii is an anisohydric species as evidenced by a steeper slope of the relationship between ψ_md and ψ_pd (σ, 1.88), and a larger difference between ψ_md and ψ_pd (Δψ, -1.66 ± 0.10 MPa). In contrast, S. psammophila could be described as an isohydric species (0.82 for σ and -0.77 ± 0.02 MPa for Δψ). Surprisingly, despite being anisohydric, C. korshinski showed greater long-term WUE than isohydric S. psammophila, particularly during the dry season. Insofar as water availability is concerned, these results show that the environmental adaptability of C. korshinskii may generally be more ecologically plastic than that of S. psammophila. Our study serves as a reference for evaluating the persistence of shrub species in relation to the management and restoration of ecosystems.

柳柳和柠条是在黄土高原上重新耕种农田的先锋物种。了解这两种物种的用水策略和生理特性对于评估它们在缺水生态系统中的适应性至关重要。我们使用稳定同位素（d和¹⁸ O），生理参数（例如中午和黎明前叶水势和气孔导度（ψ _MD，ψ _PD和g_小号，分别地））和叶面δ ¹³ C至分析水源，isohydric / anisohydric两种灌木的行为和水分利用效率（WUE）。我们的结果表明沙门氏菌在干旱时期（5月和6月）依靠中间土壤层（距地面30-80厘米）的水（平均60％），而C. korshinskii依靠深土壤层（80-100厘米）的水。 （平均52％）。这两个物种转移到在湿期间（七月和八月）（平均值61％，使用水从浅层（0-30厘米）沙柳和51％柠条）。这些根系吸水图案是一致柠条的生理性能，这又是一个描述该一致柠条是anisohydric物种由ψ之间的关系的更陡的斜率所证明_MD和ψ _PD（σ，1.88），和之间的较大差异ψ _MD和ψ _PD（Δψ，-1.66±0.10兆帕）。与此相反，沙柳可以被描述为一个isohydric物种（0.82σ和-0.77±0.02兆帕Δψ）。出人意料的是，尽管C. korshinski具有羟基，但其长期WUE值要比同羟基S. psammophila高，特别是在旱季。就水的可利用性而言，这些结果表明，C。korshinskii的环境适应性通常比沙门氏菌具有更大的生态可塑性。。我们的研究为评估灌木物种与生态系统的管理和恢复之间的持久性提供了参考。