Dynamics of Vegetation Development on Post-Mining Areas: Soil Thickness and Bioactivation

Reclamation of disturbed lands restores the post-mining ecosystem and land use. It is an essential stage of any mining operation. The appropriate reclamation strategy improves the speed and effectiveness of soil reclamation. For instance, the soil thickness and the bioactivation method determine the effectiveness of plant reclamation on depleted open-pit coal mines. This three-year field experiment (2023–2025) focused on an open-pit coal mine wasteland in the Kemerovo Region, Russia. It involved three types of experimental plots that simulated different reclamation approaches: humus-producing technosol, lithogenic technosol, and initial embryozem. Each plot was planted with trees, shrubs, and grass. The survival of woody plants was assessed visually, with mortality and survival criteria recorded. The grass cover status was assessed by Normalized Difference Vegetation Index (NDVI), obtained from aerial photography and processed in Agisoft Metashape Professional. The biopreparation included a consortium of Bacillus subtilis strains selected for high antioxidant and phytohormonal activity, which demonstrated the greatest stimulating effect on grass seed germination. The effectiveness of the biopreparation depended significantly on the substrate conditions. The humus-rich technosol failed to improve the biopreparation: the survival rate of Scots pine (Pinus sylvestris L., 1753) was 66.7%, which was below the control (85.3%). The lithogenic technosol had a species-specific effect: the survival rate of pyramidal poplar (Populus nigra L., 1753) reached 100.0% while that of blue honeysuckle (Lonicera dioica L., 1753) dropped to 63.6% by 2025 versus 84.1% in the control. The embryozem demonstrated the lowest results: the survival rate for black chokeberry (Aronia melanocarpa (Michx.) Elliott, 1821) was 52.9% versus the initial 70.6%. The projective grass cover reached 100.0% by 2024 on all three plots but was much lower during the first year. The biopreparation failed to become a universal solution, and its effectiveness depended on the type of soil substrate and plant species. It proved rather effective for lithogenic technosols of intermediate fertility. However, its use seems impractical under optimal conditions and even inhibiting under extreme conditions.