|Restoration of Open Mining Areas|
In Central Europe large-scale disturbances on landscape level are mostly caused by mining of mineral ressources (e.g. lignite, coal, limestone). In some regions surface-mining exceeded the mass turnover of the last ice age. The enormous land requirements and the damage caused by the lowering of the groundwater table led to the destruction or impairment of extensive natural floodplains, woodlands, grasslands as well as elements of the cultural landscape (e.g. semi-dry grasslands). Alone in eastern Germany 1000 km² are affected by surface-mining of lignite.
The research activity of the last 10-20 years proved that not-recultivated mining sites showed a high ecological potential. Within the range of not-recultivated areas nutrient-deficiency, a high heterogeneity in term of substrate, topography and hydrology as well as a high geomorphological dynamic resulted in many niches for establishment of rare and endangered animal and plant species (see table 1).
Table 1: Number of animal and plant species in former lignite mining areas of Saxony-Anhalt (eastern Germany) (Stand: 2002).
In not-recultivated surface-mined land of eastern Germany wilderness areas developed spontaneously within 10-30 years. In the centre of industrial and post-industrial agglomeration areas these wilderness regions with their own and unique aesthetical charm turned to high-profile areas for recreation and tourism.
Succession research documents the unexpected high self-regeneration capacity of many mining areas that resulted in free service of nature concerning the re-vegetation of surface-mined land. These results about spontaneous colonisation of former mining areas enable prognoses about course and duration of spontaneous vegetation development on raw soil and lay the foundation for near-natural methods of assisted site recovery. Especially nearby settlements or on sites endangered by erosion a fast vegetation development is required. Near-natural methods of re-vegetation offered alternatives to traditional recultivation methods. State of the art in restoration of open grasslands is the seeding of standard seed mixtures. The composition of these seed mixtures (mostly not site-specific species, seeds of foreign provenances, dominance of a few grasses) mostly required an elaborate preparation and amelioration of the sites with extreme site conditions (nutrient-poor raw soils, sites with low pH values, dry sites). On the other hand, even on raw soil with extreme site conditions the use of site-specific species of local origin and the establishment of early successional stages led to a sustainable vegetation development and a successful protection from erosion without alteration of the site conditions. Usually, no management and no expensive follow-up work (additional seeding and melioration) is necessary. Near-natural methods of restoration (e.g. seed-rich plant clipping material, overburden with vegetation, mulch seeding of site-specific species with seeds from local provenances) ensure a fast and effective erosion control as well as a sustainable development of valuable vegetation units for nature protection and recreation. In the course of time and in combination with spontaneous succession, valuable biotope mosaics will develop that enable the spatial coexistence of early and late successional stages and guarantee long-term habitats for many animal and plant species.