Session

European semi-natural mountain grasslands are currently threatened by both land abandonment and management intensification, which calls for more research in theses biodiversity hotspots. In this study we investigated the effects of management practices relaxation on plant and butterfly communities. Thirteen study sites were selected in the southwestern Swiss Alps. Each site included three meadows that have been intensively managed for at least the last 20 years. Adopting a randomised block design, two out of three meadows per study site are now being restored by shifting their mode of exploitation towards low-intensive (1/3 of the fertiliser dose applied beforehand) or extensive management (cessation of fertilisation). Four years after the onset of the experiment, plant species richness increased by 9.3% in extensive meadows. Moreover, butterfly abundance was more than two times higher, and species richness increased by 81% in extensive meadows compared to the control (intensive meadows). The increase in butterfly abundance and richness was mostly driven by a strong decrease in vegetation density and increase in forb cover. Moreover, extensive meadows had higher conservation value, harbouring more threatened butterfly species. No improvement was, yet, detected in low-intensive meadows. Altogether results indicate that the butterfly community can respond rapidly (faster that plant species richness per se) to management changes, following passive restoration.