Near‐natural methods promote restoration of species‐rich grassland vegetation—revisiting a road verge trial after 9 years

Abstract

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.

Hay and seed transfer to re-establish rare grassland species and communities: How important are date and soil preparation?

“…We only found a small advantage of deep tillage compared with shallow tillage not justifying the higher negative impact on soil structure and biota. Our study also confirmed that longterm monitoring is required to evaluate restoration success in productive grasslands (Auestad et al, 2016;Baasch et al, 2016). Within usual study periods of three to four years, results may be misleading since self-thinning due to seedling mortality reduced target plant number in the first years but later on secondary spread increased abundance.…”

Advancing restoration ecology: A new approach to predict time to recovery

“…The minimum data requirement for M A models is a time series of at least three temporal recordings. An additional danger of obtaining mis‐specified models from sparse data appears when compositional dissimilarity from the restoration target increase shortly after disturbance (Auestad, Rydgren, & Austad, ; Kirmer, Rydgren, & Tischew, ). In succession, random variation in species composition between years may override a weak temporal trend.…”

Roadside diversity in relation to age and surrounding source habitat: evidence for long time lags in valuable green infrastructure

“…Because of the pervasiveness of roads throughout rural landscapes, road verges have the potential to have a significant impact on landscape‐level biodiversity, both positively and negatively, with national governmental agencies providing guidelines for appropriate road‐verge management (Bromley, McCarthy, & Shellswell, 2019; Venner, 2006; Swedish Transport Administration, 2019). To promote biodiversity of grassland plant species, mowing more than once per year and removing the resulting material has been found to be most effective (Jakobsson, Bernes, Bullock, Verheyen, & Lindborg, 2018), while active restoration such as seed sowing can also be used to increase the number of target species present (Auestad, Rydgren, & Austad, 2016). However, due to the increased costs of these more intensive methods of management, it is not financially or practically feasible to implement them on all road verges in all landscapes.…”