Forest biodiversity and production potential of post-mining landscape: opting for afforestation or leaving it to spontaneous development?

Land reclamation of post-mining sites strongly influences not only diversity and biomass of frequently studied ground vegetation, but also diversity of forest ecosystem. In most cases, spoil heaps are afforested after coal mining, but some reclaimed sites are left to spontaneous development, such as our study locality – surroundings of the Sokolov town, Czech Republic. Structure, species diversity and production potential were studied on three heap sites, artificially afforested by pedunculate oak (Quercus robur L.), black alder (Alnus glutinosa [L.] Gaertn) and silver birch (Betula pendula Roth) stands, and compared with three permanent research plots (PRP) left to natural succession processes with prevailing European aspen (Populus tremula L.), goat willow (Salix caprea L.) and also with silver birch. The timber production increased from the willow stand (28 m³ ha⁻¹) to birch ones (97 m³ ha⁻¹, all 45 years old). The mean stand volumes were significantly higher on afforested PRPs (74 m³ ha⁻¹) than on succession PRPs (51 m³ ha⁻¹), just as tree diameters. However, in terms of production quality, occurrence of breaks was significantly higher on afforested PRPs (15%) compared to succession PRPs (7%), while the opposite situation was observed in the stem quality. Horizontal structure of trees was regular on afforested PRPs, while spatial pattern on succession PRPs was aggregated. The highest differences in favor of succession PRPs was found in species richness and total stand diversity. These results imply a need for combined approaches in post-mining landscape management to support economic benefit and especially ecological value.