Spatiotemporal changes of soil profile salinization in Xinjiang and their response to glacial runoff variations

Currently, the understanding of root-zone soil salinization—which critically influences vegetation growth—and its response to ongoing glacier retreat remains limited, hindering objective assessments of vegetation health and hydrological effects in arid regions. To address these issues, this study simulated profile soil salinization (0–100 cm) across the Mountain-Oasis-Desert System (MODS) in Xinjiang using a Random Forest (RF) model. Glacier runoff from 1960 to 2022 was simulated for multiple Xinjiang basins using the Open Global Glacier Model (OGGM), and the Geodetector model was employed to elucidate the response mechanisms linking soil salinization to glacial runoff and other environmental variables. Results show that soil salinization in Xinjiang exhibits a general increasing trend, characterized by surface accumulation (0–10 cm > 40–60 cm > 10–20 cm > 60–100 cm > 20–40 cm), although patterns differ between oasis and desert regions. Over the past 60 years, glacier meltwater runoff has increased in most river basins. In some basins (e.g., JSR, URB, ETNR), glacier runoff peaked before 2014, with the maximum value not exceeding 0.3 Gt. The largest annual glacier meltwater runoff occurred in the YarRB (4.48 Gt), followed by the WeiRB (3.66 Gt), the Ili River Basin (2.67 Gt), and the AksR (2.62 Gt). With increasing soil depth, dominant controls shift from climatic variables to soil physicochemical properties and topography, while the interactive effect between glacial runoff and other environmental variables becomes increasingly pronounced. Notably, glacial runoff exerts its strongest influence on the 60–100 cm layer, and this impact continues to intensify across basins, with an annual mean factor detection q-value reaching 0.63. This study is the first regional-scale quantitative investigation in Xinjiang to reveal the relationship between glacial runoff and deep soil salinization. These findings provide valuable insights for water resource management, salinization control, and ecological environmental protection.