The Influence of Tree Species on Soil Development and Soil Classification in Reclaimed Post-Mining Areas

Soil formation in post-mining areas is strongly influenced not only by parent material but also by the vegetation introduced during reclamation. Tree species affect pedogenic processes through litter input, root activity and associated microbial communities. This study investigates soil development in reclaimed post-mining landscapes, focusing on the combined influence of tree species and substrate properties. Two forest sites in Poland were analysed: Szczakowa (former open-pit sand mine) and Bełchatów (lignite mine spoil heap), 30–40 years after reclamation and afforestation with four dominant species: silver birch, European larch, Scots pine and red oak. Differences in soil development were observed among tree species. Stands with deciduous trees (birch and oak) were generally associated with clearer horizon differentiation, higher soil organic carbon and nitrogen content, and more pronounced iron redistribution compared with coniferous stands. The mean thickness of the combined organic-rich surface horizons was 12.4 cm at Szczakowa and 10.8 cm at Bełchatów. Coniferous species were more often linked with soil acidification and early stages of podzolisation-like processes, particularly in sandy substrates, whereas soils under deciduous species showed features related to brunification and organic matter incorporation. The study also included a comparison of soil classification systems, indicating that the World Reference Base for Soil Resources (WRB) offers a flexible framework for describing young and anthropogenically transformed soils compared with traditional national classifications. From a sustainability perspective, the results highlight that strategic species selection during reclamation, specifically promoting birch on sandy substrates and oak on heterogeneous technogenic substrates, enhances soil organic carbon accumulation, nutrient retention and iron cycling, thus contributing to the long-term restoration of ecosystem services on degraded post-mining landscapes.