Biological soil crusts (biocrusts) are widespread in drylands and critically regulate surface hydrology, yet their influence on vascular plant water use strategies remains poorly understood. In semiarid drylands, biocrusts frequently coexist with shrubs, forming complex shrub-biocrust interactions that influence ecohydrological processes. Here, we investigated how moss-dominated biocrusts beneath the canopy of Artemisia ordosica modulate shrub water uptake strategy and water use efficiency (iWUE) on the Chinese Loess Plateau. Across a growing season (May-October), we conducted continuous soil moisture monitoring, monthly sampling of soil and xylem water isotopes (delta H-2, delta O-18), leaf delta C-13 analysis, and root trait measurements across paired shrub patches with and without well-developed biocrusts. The results showed that biocrusts altered soil moisture profiles by increasing soil water storage by 5.3 %-18.4 % in the upper layer (0-20 cm) and reducing it by 3.3 %-11.1 % in the lower layer (20-60 cm). This altered hydric scenario led to increased shallow water uptake by shrubs, with 49.5 % to 67.5 % of xylem water in shrub-biocrust patches derived from the upper soil layer, compared to 41.3 % to 62.3 % in shrub patches. Moreover, the length density and surface area density of very fine roots (diameter < 0.5 mm) in the 0-5 cm soil layer increased by 59.0 % and 150.0 %, respectively. In the lower soil layer, no significant differences in root traits were observed. We also found that, shrub leaves in shrub-biocrust patches exhibited moderately higher iWUE (increased by 2.7 %-9.0 %). Together, our results demonstrate that biocrusts concentrate water near the soil surface, promoting shallow water uptake by shrubs, which may limit shrub access to more stable water sources in the lower layer, particularly during prolonged drought. Our study underscores the importance of integrating shrub-biocrust relationships into dryland restoration and water management strategies under increasingly fluctuating climatic conditions.