Anti-erosion rehabilitation: Effects of revegetation method and site traits on introduced and native plant cover and richness.

In mountainous areas, bare slopes represent often dangerous forms of land degradation that need to be rehabilitated. However, revegetation is usually performed with non-native plants, negatively impacting the natural landscape value. Comprehensive studies, especially on poorly investigated long-term revegetation effects, are therefore essential for the improvement of rehabilitation practices. In this study, four landslides or disused quarries surrounded by well-preserved (semi-) natural vegetation that were revegetated between 1988 and 2002 with non-native only herbaceous or both herbaceous and woody plants were studied 1-9 and 16-31 years after rehabilitation. A total of 111 sampling areas were surveyed for introduced and volunteer species and other important ground cover soil and topography traits. Climatic traits and species' ecological indicators were retrieved from the available databases. The time patterns and ecological spectra of the plant covers were analysed and correlated to the site traits. In the first decade, introduced plants were initially abundant but decreased rapidly. In the long-term, the more stress-tolerant among them still had a considerable cover, especially in fine-textured soils. Native species were established slowly but, due to their higher stress tolerance, dominated in the long-term, especially at more stressful sites. In areas with predominantly herbaceous cover, soil factors, such as gravel content, were more related to the plant cover. In areas with predominantly woody plant cover, the high plant cover was dependent on microclimatic factors, especially aspect. At sites like those studied here, woody species should be always used, but in the form of native plants, as they tend to persist. If herbaceous species are unavailable in native forms, their introduction should be avoided in areas not exposed to erosion, whereas poorly stress-tolerant non-native plants should be used in steep areas as they create a fast but short-lasting cover compensated in the long term by the establishment of native species.