Haymaking complemented by moderate disturbances can sustain and restore species-rich alpine to subalpine grasslands

The high plant diversity in alpine to subalpine grasslands is threatened by the abandonment of land use. In addition, changing environmental conditions might lead to vegetation shifts even when traditional land use is maintained, as observed in grasslands in Switzerland during the last decades. Maintaining and restoring the diversity of such grasslands might therefore require modified management methods. We conducted a six-year experiment to assess the responses of plant species richness, mean ecological indicator values, and vegetation composition to five management treatments, including scraping as additional management measure: haymaking (in autumn), haymaking complemented by scraping (i.e. manual raking) in autumn, haymaking complemented by scraping in spring, only scraping in spring, and abandonment of land use. We hypothesized that haymaking complemented by scraping in either season would remove additional biomass and increase species richness by creating open patches that can reduce inter-specific competition and promote species establishment. We found positive effects of haymaking complemented by scraping on plant species richness and habitat quality, indicated by the increased mean indicator value for light. Abandonment showed the opposite effects and increased mean indicator values for nutrients. Interestingly, haymaking combined with scraping in autumn promoted the development of the vegetation towards the composition similar to the resident vegetation type. Our findings show that extensive land use is essential to maintain species-rich alpine to subalpine grasslands. Further, they imply that modified land use can compensate for the negative developments such as reduced habitat quality and species richness caused by environmental changes and help restore the vegetation.