Effect of topography and properties of parent materials on organic carbon content in technosols of a post-mining lignite site

Soil organic carbon (SOC) is one of the basic soil properties for assessing the effects of Dumps reclamation after open-pit mining. In this study, we focused on the effect of parent material properties and internal Dump topography on SOC accumulation in 42-year Technosols. A total of 175 soil samples were taken from 0 to 20 cm depth of minesoils and SOC, pH, CaCO₃, TN (total nitrogen), sand, silt and clay fraction contents were determined. Our research revealed that the combinations of topographic variables of the internal dump and properties inherited from the parent material have a significant impact on prediction and thus on accumulation of SOC in minesoils. Topographic variables characterizing rainwater redistribution are crucial to SOC, where SAGA wetness index (SWI), vertical distance to channel network (VDChN), elevation and soil parameters such as N and sand fraction had the greatest impact on SOC. Also, nonlinear models based on random forest (RF), showed higher SOC prediction accuracy than multiple linear regression (MLR). The study revealed that environmental variables with varying spatial resolution produce different SOC prediction results. Among the tested resolutions (2, 5, 10 m), the best SOC prediction was obtained using variables with 5 m resolution for both MLR and RF.