Vegetation succession on reclaimed coal wastes in Spain: the influence of soil and environmental factors

Question How is vegetation succession on coal mine wastes under a Mediterranean climate affected by the restoration method used (topsoil addition or not)? How are plant successional processes influenced by local landscape and soil factors? Location Reclaimed coal mines in the north of Palencia province, northern Spain (42 degrees 47'-42 degrees 50' N, 4 degrees 32'-4 degrees 53' W). Methods In Jun-Jul 2008, vascular plant species cover was monitored in 31 coal mines. The mines, which had been restored using two restoration methods (topsoil addition or not), comprised a chronosequence of different ages from 1 to 40 yr since restoration started. Soil and environmental factors at each mine were monitored and related to species cover using a combination of ordination methods and Huisman-Olff-Fresco modeling. Results Plant succession was affected by restoration method . Where topsoil was added, succession was influenced by age since restoration and soil pH. Where no topsoil was added, soil factors seem to arrest succession. Vegetation composition on topsoiled sites showed a gradient with age, from the youngest, with early colonizing species, to oldest, with an increase in woody species. Vegetation on non-topsoiled sites comprised mainly early-successional species. Response to age and pH of 37 species found on topsoiled mines is described. Conclusions Restoration of coal mines under this Mediterranean climate can be relatively fast if topsoil is added, with a native shrub community developing after 15 yr. However, if topsoil is not used, it takes more than 40 yr. For topsoiled mines, the species found in the different successional stages were identified, and their tolerance to soil pH was derived. This information will assist future restoration projects in the area.