Flexible water use patterns are of great importance for the survival of vegetation in dryland regions. Our study aimed to investigate the influences of season and slope aspect on the water use patterns of Caragana korshinskii on typical shady and sunny slopes on the Loess Plateau in China. We collected xylem water, soil water from the 0–200 cm soil layers, and precipitation in May, July, September and November 2018 and measured their hydrogen (δD) and oxygen (δ¹⁸O) isotope compositions. The root distribution of C. korshinskii in the 0–200 cm soil layer on both slopes was also investigated. The 0–20, 20–80, and 80–200 cm soil layers were identified as three potential water sources for C. korshinskii, and their proportional contributions to the plant water supply were calculated using a linear mixed model. The results showed that C. korshinskii on the sunny slope absorbed 89.3% of their water from the 0–20 cm soil layer in May but mainly utilized water from the 0–20 and 20–80 cm soil layers in both July and September, and the total contribution percentages of these layers were 84.5% and 89.2%, respectively. However, C. korshinskii on the shady slope extracted water evenly from all three soil layers in May. Thereafter, the plants absorbed water from the 20–80 and 80–200 cm soil layers in both July and September, and the total contribution percentages of these layers were 96.0% and 91.8%, respectively. In November, C. korshinskii absorbed 84.8% and 78.0% of their water from the 80–200 cm soil layer on the shady and sunny slopes, respectively. The generally shallower soil water use of C. korshinskii on the sunny slope than on the shady slope may be due to the larger fine-root (d < 2 mm) length density in the 0–80 cm soil layer on the sunny slope (1.12 ± 0.28 mm/cm³) than on the shady slope (0.57 ± 0.16 mm/mm³) (P < 0.05). This study indicates that C. korshinskii on both shady and sunny slopes seasonally switched their water sources from different soil water layers during the growing season. However, due to their reliance on soil water at the 0–20 cm depth, which is supplied by unstable rainfall, C. korshinskii on sunny slopes may be more vulnerable to future climatic warming and drying on the Loess Plateau. Our findings provide valuable information related to optimal water management in the afforested shrublands in this region.

灵活的用水方式对于干旱地区植被的生存至关重要。我们的研究旨在调查季节和坡度对黄土高原典型阴暗和阳坡上柠条锦鸡儿用水模式的影响。我们收集了木质部水，从0-200厘米土壤层的土壤水分，并沉淀在五月，七月，九月和十一月2018和测量它们的氢（δD）和氧（δ ¹⁸ O）同位素组合物。还研究了两个斜坡上0-200 cm土层中C. korshinskii的根分布。0-20、20-80和80-200 cm的土壤层被确定为C. korshinskii的三种潜在水源，并使用线性混合模型计算它们对植物供水的比例贡献。结果表明，阳光山坡上的C. korshinskii在5月份从0–20 cm土层吸收了89.3％的水分，但在7月和9月主要利用了0–20和20–80 cm土层的水分，并且这些层的总贡献百分比分别为84.5％和89.2％。然而，柠条上阴坡萃取水均匀地从五月所有三个土层。此后，植物分别在7月和9月从20-80和80-200 cm的土壤层中吸收了水分，这些层的总贡献率分别为96.0％和91.8％。11月，C。korshinskii分别从阴凉的山坡和80-200厘米的土壤层吸收了84.8％和78.0％的水。一般较浅土壤水分利用的柠条向阳斜率比在阴坡可能是由于在0-80厘米的土壤层上的阳坡较大细根（d <2mm）的长度密度（1.12 ±0.28 mm / cm ³）大于阴影的斜率（0.57±0.16 mm / mm ³）（P  <0.05）。这项研究表明，在生长季节，在阴凉和阳光明媚的山坡上，C。korshinskii都季节性地从不同的土壤水层切换水源。但是，由于它们依赖于0–20 cm深度的土壤水，这由不稳定的降雨提供，C。korshinskii黄土高原上阳光充足的山坡上的雨水可能更容易受到未来气候变暖和干旱的影响。我们的发现为该地区绿化灌木丛的最佳水资源管理提供了有价值的信息。