Renaturation of post-mining landscapes; a binational project
Open-cast mining is one of the most serious forms of human intervention in nature and the landscape. Around one percent of the world’s land mass is affected by this anthropogenic disturbance and its lasting impact on soil structure, water balance, flora, and fauna.
Over the past few decades, research has focused on the natural recolonization of post-mining landscapes in eastern Germany and the Czech Republic. The results of numerous research projects show that spontaneous succession on the heterogeneous and often nutrient-poor substrates created by open-cast mining leads to the development of structurally and species-rich habitats with many rare animal and plant species.
However, spontaneous succession takes time. Depending on site conditions, plant recolonization can take several decades. Especially at sites (embankments) threatened by wind or water erosion or in the vicinity of towns, it is therefore often necessary to accelerate vegetation development.
By “learning from nature,” new ecological renaturation strategies can be developed that incorporate the natural potential of the areas. The combination of spontaneous processes and near-natural greening leads to the sustainable development of valuable habitats in post-mining landscapes.
Based on this premise, a joint project between Anhalt University of Applied Sciences in Bernburg and Jihočeská University in České Budějovice was launched in early 2009.
Project priorities
The aim of this project is to formulate generally applicable colonization and succession mechanisms for European post-mining landscapes and to derive general strategies for accelerating vegetation development in a natural way. To this end, existing permanent observation areas for spontaneous and controlled succession in the Central German and Czech lignite mining areas will be continued, and new demonstration trials for near-natural greening will be set up. Based on joint scientific analyses, guidelines for the successful ecological renaturation of mining areas will be developed that can be applied to post-mining landscapes in Central Europe.
Project region
Germany (Roßbach, Profen); Czechia
Further project details
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The former Roßbach open-cast mine is located in the Geiseltal mining district in Saxony-Anhalt. In September 2000, three variants were implemented in a block design with three replicates on a total area of 1.14 ha on a vegetation-free embankment of deposited loess (pH 7.5):
(1) Sowing of 15 herbs and 6 grasses: 2 g/m², site-appropriate seed mixture with autochthonous species (drill sowing with raised coulter). In addition, a seed-poor mulch layer (2nd cut Saaledämme) was applied (approx. 5 cm thick) to protect against erosion.
(2) Mown material transfer: For this purpose, a species-rich area (97 species, 71 of which are target species characteristic of semi-dry grasslands and mesophilic grasslands) was mown in the “Göttersitz” nature reserve, about 20 km away. The seed-rich material was immediately transported to the test areas and freshly applied (approx. 1 kg/m², 5 cm thick).
(3) Control with spontaneous succession.Results
The introduction of suitable seeds through mown grass transfer and sowing significantly accelerated vegetation development. In the second year, more than 40% of the surface area was already covered by vegetation in these variants. Erosion processes were very effectively prevented by the mown grass or mulch cover. From 2004 onwards, vegetation cover remained consistently high. Both seeding and mown grass transfer led to the rapid establishment of species-rich, site-appropriate stands. The target species developed most successfully after mown grass transfer. Overall, both methods can be recommended for accelerating vegetation development on sites at risk of erosion.
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Mining embankments are often greened with inexpensive, species-poor standard seed mixtures. These usually contain only a few cultivated varieties of grasses (mainly Festuca spec.). At the Profen opencast mine (Zeitz-Hohenmölsener district, Saxony-Anhalt), various seed mixtures were tested in a block trial, both with and without mulch cover.
In December 2004, the following four variants were implemented on a nutrient-poor, vegetation-free embankment: (1) species-poor seeding (two Festuca cultivars, Lolium perenne), (2) species-poor seeding with mulch cover (approx. 5 cm), (3) species-rich seeding (40 herbs and 11 grasses, regional origins), (4) species-rich seeding with mulch cover (approx. 5 cm).
Results The sowing of species-rich, regional mixtures led to the development of diverse vegetation suited to the location. Gradually, some target species from the species-rich variants were also able to migrate into the adjacent, species-poor areas. However, by 2010, there were still significant differences between the variants in terms of the number and coverage of target species. Species-rich, regional sowing thus contributes to increasing local diversity. An additional layer of mulch supported the establishment of the species and prevented erosion processes. By the end of the study, the number of target species in the variants with mulch was slightly higher than in the variants without mulch.
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In 2009, a workshop on the renaturation of sandy dry grasslands, which have become rare in the region as a result of changes in land use, was held in České Budějovice. The aim was to accelerate the establishment of typical sandy dry grasslands in suitable mining areas in a near-natural way. Approximately 1,000 liters of raked material (seeds, plant parts, cryptogams) were obtained from two donor areas by raking an area of approximately 250 m². The recipient area was a sand island within a still partially active sand pit near Suchdol nad Lužnicí (Českomoravskýštěrk, Heidelberg Cement Group). The transfer experiment was set up in a block design with four replicates and three variants (control, two different donor areas). The transfer ratio from donor to recipient area was 1:1.
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Data collection will continue on the Czech and German test sites even after the project has ended in order to document the long-term success of the renaturation methods used. The results of the project are summarized in the handbook Near-natural restoration vs. technical reclamation of mining sites.