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The open-cast lignite mine “Hambach” (NW-Germany) and the accompanying land reclamation replace a large ancient forest. Reclamation of an 1000 ha large overburden dump started 25 years ago and is still in progress. Reclamation methods comprise combinations of different topsoil dumping techniques and reclamation measures such as seeding or afforestation. In accordance with the spatial heterogeneity hypothesis, we hypothesize that beetle assemblages from sites where the topsoil was left structured are more diverse than those from sites with levelled topsoil, and that richly structured mid-successional sites harbour more heterogeneous assemblages than afforested sites. We tested the influence of environmental variables on assemblage characteristics of pitfall-trapped beetles from 17 sites on the overburden dump. The results are based on 35,588 individuals from 339 species. Species assemblages differed significantly between almost all sites. Habitat age did not affect assemblage characteristics, while species richness was significantly influenced by surface structure. Sites that were not levelled and that additionally included pits that slope down for several meters exhibited the highest species richness. Abundance of beetles increased in parallel to the canopy cover, whereas assemblage heterogeneity (MVDISP) decreased. Successional and grassland sites usually exhibited higher diversity (Fisher's α) than afforested sites, but diversity was not significantly predicted by a single environmental factor. Instead, diversity increased along with increasing MVDISP-values. Afforestations speed up the successional process and some euryecious forest species are already well established, but stenecious forest specialists have not yet been found.

Reclaimed lignite open-cast mine areas in the Rhineland are covered by a mixture of loess and sand deposits containing organic material that originates from the upper quartary soil which has been taken from the front of the mining path. Consequently, the soil fauna that has established itself on the reclaimed open-cast mine areas may result from the primary succession and also from species that are carried to the dumping mines and are able to survive the dumping process. The reclaimed landscape consists of a regular structural pattern of crests and troughs. The troughs provide appropriate habitats for establishing a rich and diverse fauna with higher densities of almost all animal groups investigated, with enhanced microbial activity and higher values of available macronutrients. In terms of plant growth, the physical and chemical conditions found in the troughs exceeded the conditions found on the crests. From laboratory studies we made the following conclusions: (1) environmental conditions in the troughs were improved not only by erosion, but additionally by the soil fauna that directly enhanced microbial activity and indirectly increased the availability of macronutrients; (2) soil animals improved soil quality by increasing the pH-values, increasing the ammonium–nitrogen content and decreasing the content of aluminium ions; and (3) a multiple-species system is able to improve soil quality more effectively than a single-species system.