A comparison of different soil transfer strategies for restoring a Mediterranean steppe after a pipeline leak (La Crau plain, South-Eastern France)

Abstract

Among the techniques used for the restoration of terrestrial ecosystems, soil transfer has already produced encouraging results for re-establishing species-rich grassland plant communities. On August 7 2009, a serious oil pipeline leak occurred in the La Crau steppe in south-eastern France. In 2010, more than 5ha of steppe vegetation were then destroyed by the excavation, and removal of polluted soil. Restoration of the site was achieved by transferring 72000t of identical soil from a nearby quarry. Soil was applied in four treatments, each with a different degree of profile complexity. After three years (2011, 2012 and 2013), our results show that the replacement of the soil to include horizon similar to the reference steppe allows recovery of the vegetation in terms of composition, similarity and species richness of the steppe vegetation during this period. The ecological engineering guidelines aimed at limiting the transit time of the soil and the reconstitution of its vertical layer organisation resulted in the improved recovery of the vegetation without colonisation by non-target species. This system may further benefit from reintroduction of traditional sheep grazing to promote sustainability following the restoration of the steppe vegetation.