Distance and wind direction dependent patterns of soil multifunctionality around an open-pit coal mine in an arid...

Open-pit coal mining can substantially alter vegetation and soil processes in fragile arid ecosystems, yet its effects on soil multifunctionality (SMF) and spatial variation remain insufficiently understood. In this study, we investigated an open-pit coal mine located on the eastern edge of the Junggar Basin, Xinjiang, China. Soil carbon storage, nutrient supply, and nutrient cycling indicators were measured along directional and distance gradients around the mine pit to assess the spatial heterogeneity of SMF and identify the major biotic and abiotic factors associated with its variation. The results showed that mining disturbance led to significant directional differences in SMF and its component functions around the mining area, with nonlinear patterns along the distance gradient. As distance from the mine pit increased, nutrient supply showed a unimodal pattern in several directions, whereas nutrient cycling exhibited an opposite response; potential thresholds of these functional changes were mostly observed within approximately 0.6-1.5 km from the mine pit. From the perspective of different wind directions, SMF showed a unimodal pattern along the distance gradient in the downwind direction, but gradually increased in the upwind direction. Further analyses indicated that downwind SMF was more closely associated with soil heavy metal contamination, whereas upwind SMF was mainly related to background ecosystem conditions, such as soil properties and plant community characteristics. These findings highlight the need to consider both distance gradients and prevailing wind direction when assessing the ecological impacts of open-pit coal mining, and provide a reference for soil function evaluation and ecological restoration in arid mining regions.