Plants alter vertical hydrological connectivity to influence moisture recycling through varying water use strategies in China's Loess Region

While vegetation changes have significant impacts on regional water cycles, the mechanism by which vegetation influences moisture recycling remains unclear. This study examines the differences in moisture recycling and the underlying mechanisms across vegetation types from the perspective of vertical hydrological connectivity (soil water – root water uptake – ET – moisture recycling). Three types of vegetation (grass, shrub and forest) in China's Loess Plateau were chosen as examples, and the water stable isotope tracing technique was employed. Results indicate that moisture recycling rates ( f ) increase from 33% to 38% along the sequence of grass → Caragana korshinskii → Malus domestica → Robinia pseudoacacia , with the contribution of transpiration ( f T ) increasing from 18% to 26%, while the contribution of evaporation ( f E ) decreases significantly from 16% to 12%. These differences arose because plant water use strategies altered vertical hydrological connectivity: deeper root water uptake reduced soil water storage and deep drainage, shifted evapotranspiration from evaporation toward transpiration, and consequently increased the transpiration-derived contribution to precipitation. Vegetation types along the transition from grass to forest exhibited annual water deficits of 43.0 to 77.5 mm yr −1 , and the consumed soil water contributed to 59% of the increase in evapotranspiration (444.4 to 575.7 mm yr −1 ). Among them, the increase in transpiration dominated the rise in precipitation, with a conversion rate of approximately 17%. These findings provide important understanding of the hydrological processes within the soil-plant-atmosphere continuum and offer scientific backing for ecological restoration approaches.