Space-time dynamics and potential drivers of soil moisture and soil nutrients variation in a coal mining area of semi-arid, China

Abstract

The spatial–temporal variability of soil moisture plays a pivotal role in the reconstruction and management of ecosystems in mining areas. However, the actual driving mechanisms behind long-term, continuous mining disturbances remain unclear due to a lack of continuous data. To address this gap, a network of instrumented sites, known as Disturbed Critical Zone Observatories (DCZO), has been established for ecological monitoring in mining areas. In this study, we used Sentinel-1A images of the Dafosi Mine from 2014 to 2022 and one year of continuous DCZO monitoring data. We employed Theil-Sen median trend analysis, empirical orthogonal function (EOF), and structural equation modeling (SEM) to quantitatively explore the factors influencing the variability of soil moisture and soil nutrients under continuous mining disturbances. The results showed: (1) Inter-annual variations in soil moisture differed among coal seams mined in various years, with the steepest decline observed in seams mined in 2021–2022 > 2018–2020 > 2015–2017 > 2013–2014. (2) Mining areas exhibited a significant reduction in Available Nitrogen (AN), Available Phosphorus (AP), and Available Potassium (AK), with decreases of 25.12 %, 25.38 %, and 22.59 %, respectively, compared to non-mining areas. (3) The first two EOFs explained 80.42 % of the observed spatiotemporal soil moisture pattern, 77.69 % of AN, 70.21 % of AP, and 88.32 % of AK, accounting for the total variability in soil moisture and soil nutrients. (4) The contribution rates of mining to soil moisture and nutrient variation were 27.31 % and 13.91 %, with subsidence having the most pronounced negative impact. Additionally, our study revealed that while soil moisture can partially recover through natural processes, soil nutrients require artificial reclamation during mining. This study offers valuable insights for sustainable mining management.