Encroachment of woody plants has a positive effect on hydrological functions (e.g., infiltration), but few studies have examined the effects of shrub patches on infiltration under different grazing scenarios. We examined differences in characteristics of plants and soils and saturated hydraulic conductivity between shrubs and their associated interspaces in two grazing regimes at three sites in a semi-arid grassland encroached by Caragana microphylla, a leguminous N-fixing shrub. The results showed that the shrub patches had greater plant height, cover, and biomass compared to interspaces, and the shrubs positively affected the characteristics of soils such as porosity and water holding capacity, whereas grazing had a strong opposite effect. The effect of the relative interaction intensity (RII) of shrubs on the saturated hydraulic conductivity of the soil was greater under grazed (0.60) than ungrazed conditions (-0.01), and the negative effect of grazing was mainly achieved in interspaces. Generally, structural equation modeling revealed positive indirect effects of shrubs on saturated hydraulic conductivity via a greater root mass, with 3.5 times of that in interspaces and a lower bulk density (90% of that in interspaces) under conditions of overgrazing. Our findings highlight the critical role that shrubs play in maintaining infiltration under overgrazing conditions and suggest that they might partially offset the damaging effects of overgrazing on infiltration. Thus, shrub encroachment might be an adaptive mechanism of grassland ecosystems to encounter intensive human induced disturbance such as overgrazing.

木本植物的侵占对水文功能（如入渗）有积极影响，但很少有研究检查灌木斑块在不同放牧情景下对入渗的影响。我们在被小叶锦鸡儿侵占的半干旱草原的三个地点的两种放牧制度中检查了植物和土壤特征的差异以及灌木及其相关间隙之间的饱和导水率，一种豆科固氮灌木。结果表明，与间隙相比，灌木斑块具有更大的植物高度、覆盖度和生物量，灌木对土壤的孔隙度和持水能力等特征产生积极影响，而放牧则具有强烈的相反作用。灌木相对相互作用强度（RII）对土壤饱和导水率的影响在放牧条件下（0.60）大于未放牧条件（-0.01），放牧的负面影响主要体现在间隙。一般来说，结构方程模型揭示了灌木通过更大的根质量对饱和导水率产生了积极的间接影响，在过度放牧条件下，其间隙是其 3.5 倍和较低的容重（间隙的 90%）。我们的研究结果强调了灌木在过度放牧条件下维持渗透的关键作用，并表明它们可能部分抵消过度放牧对渗透的破坏性影响。因此，灌木侵占可能是草地生态系统遇到强烈的人为干扰（如过度放牧）的一种适应机制。