Biodiversity conservation; Restoration ecology; Soil arthropods; Insects; Habitat heterogeneity; Geodiversity

Heterogeneity of environmental conditions is the crucial factor supporting biodiversity in various habitats, in-cluding post-mining sites. The effects of micro-topographic heterogeneity on biodiversity and conservationpotential of arthropod communities in post-industrial habitats had not been studied before now. At one of thelargest European brown coal spoil heaps, we sampled eight groups of terrestrial arthropods with different lifestrategies (moths, spiders, ground beetles, ants, orthopteroids, centipedes, millipedes, and woodlice), in suc-cessionally young plots (5–18 y), with a heterogeneous wavy surface after heaping, and compared the com-munities with plotsflattened by dozing. A combination of the standardized quantitative sampling, using twodifferent methods, and a paired design of the plot selection enabled a robust analysis. Altogether, we recorded 380 species of the focal arthropods, 15 of them nationally threatened. We revealed the importance of the micro-topographic heterogeneity for the formation of the biodiversity of arthropods in their secondary refuges. Thecommunities with higher biodiversity and conservation value were detected in the plots with heterogeneoussurfaces; exceptions were ground beetles and millipedes. The surfaceflattening, often thefirst step of technicalreclamation projects, thus suppress biodiversity of most terrestrial arthropods during the restoration of post-mining sites. Since the communities of both surface types differed, the proportional presence on both surfacescould be more efficient in supporting the local biodiversity. We suggest reducing the surface dozing for the caseswith other concerns only, to achieve a proportional representation of both surface types. Such a combination of different restoration approaches would, thus, efficiently support high biodiversity of groups with various needs.