The present loss of species-rich grasslands makes it vital to restore these valuable habitat types, including novel habitat variants such as road verges. Due to the lack of knowledge on long-term outcomes of restoration initiatives, well-designed studies comparing different restoration methods are needed. In this study, we examined fine-scale vegetation recovery patterns over 9 years in a field experiment with several near-natural restoration methods (adding local seed mixtures, transferring hay from local grasslands using hard or light raking, and natural regeneration) in a road verge. We compared this to standard revegetation (hydroseeding species-poor commercial seed mixtures). We found major temporal changes in vegetation restored by local seed or hay transfer, before it gradually became more similar to the donor grasslands and seed mixtures, which served as references for the experiment. Natural (spontaneous) regeneration with seed dispersal from surroundings gave similar results, whereas areas revegetated using standard methods became more dissimilar to the reference sites during the study period. The main variation in species composition reflected the contrast between local donor grasslands and seed mixtures and the species-poor early successional grasslands. We conclude that near-natural methods (hay transfer and seeding) successfully restored species-rich grassland, including road verges. This study underlines the importance of comparing several treatments over a sufficiently long period to assess their success in restoring species-rich grassland.
Questions: How do various grassland restoration methods (hay transfer from local or distant donors, seed sowing or natural regeneration) perform in restoration of species-rich, semi-natural grasslands? Are any of the donors particularly well suited as reference vegetation? Do bare soil treatments give better results than treatments where the soil is covered? What are the probabilities of steering vegetation development towards donor vegetation under the various restoration treatments?Location: Sunnfjord open-air museum in rural, Western Norway.Methods: In a replicated field trial we tested four restoration methods: transferring fresh hay from a local or a distant donor (hay transfer), seeding with a regional species mix, and allowing natural regeneration. We evaluated outcomes by comparing species richness, transfer rates and vegetation dynamics in donor and trial vegetation over four successive years.Results: Our study revealed considerable changes in species composition under all restoration treatments, which decreased over time, indicating decelerating succession rates. Many non-trial grassland species became established, especially after seeding and natural regeneration (bare soil treatments). All trajectories became synchronized from the second year, and by trial end, the restoration treatments converged with respect to species richness and species composition.
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