Impact of Deep-Rooted Vegetation on Deep Soil Water Recharge in the Gully Region of the Loess Plateau

To investigate the impacts of vegetation change on deep soil water recharge, it is essential to identify the sources of deep soil water and deep drainage. The combination of stable and radioactive water isotopes is an effective method for studying deep vadose zones, though it has been rarely applied in complex gully areas. In this study, we measured delta 2H, delta 18O, and 3H in soil water under long-term natural grassland and C. korshinskii on the same slope. Both natural grassland and C. korshinskii plots received deep soil water from rainfall during the rainy season; however, the replenishment thresholds for soil water at depths of 2-10.4 m differed between the two vegetation types, corresponding to rainfall intensities of >= 20 mm and >= 50 mm, respectively. Following the conversion of natural grassland to C. korshinskii vegetation, the rate of soil water storage deficit increased by 46.4 mm yr-1, and deep drainage shifted from 39.6 mm yr-1 to 0 mm yr-1. Deep-rooted vegetation significantly depletes soil water to meet transpiration demands, thus hindering rainfall recharge. These findings have important implications for water and land resource management, especially in areas undergoing significant vegetation changes.