Effective ecological restoration requires reliable indicators to assess vegetation sustainability in water-limited environments. This study developed and tested novel root-soil moisture indicators using 24-year-old Caragana korshinskii stands in China's Loess Plateau. We quantified root system architecture to unprecedented depths (2380 cm) and established direct relationships between root distribution patterns and soil moisture dynamics as ecological indicators. Our indicator framework revealed three functional zones: a shallow active zone (0-200 cm) containing 61.5 % of root biomass with moderate water depletion, a critical transition zone (200-520 cm) with 27.0 % of roots showing severe desiccation, and a deep extraction zone (520-2380 cm) with sparse roots causing systematic water mining. These patterns translated to measurable ecological indicators: Caragana stands showed 1019 mm less water storage than reference cropland, indicating unsustainable water consumption of 42.5 mm annually beyond precipitation inputs. A controlled replanting experiment demonstrated that these root-soil moisture relationships serve as predictive indicators-newly established plants rapidly developed similar patterns within four years, validating the indicator framework's reliability. The persistent dry layer from 320 to 2160 cm depth emerged as a critical threshold indicator for vegetation sustainability. These findings provide practical ecological indicators for managers: root distribution patterns can predict long-term water sustainability, while soil moisture thresholds can guide restoration decisions. Our indicator approach offers a robust framework for assessing and managing vegetation sustainability in dryland restoration projects worldwide.