Restoration measures foster biodiversity of important primary consumers within calcareous grasslands

Abstract Despite great efforts in European nature conservation, semi-natural habitats such as calcareous grasslands are still suffering considerable declines due to abandonment. Shrub cutting and subsequent grazing or mowing are effective restoration measures to counteract the adverse effects of management cessation. Here, for the first time, we used leafhoppers (Auchenorrhyncha) as bioindicators to assess the conservation value of restored calcareous grasslands. We compared environmental conditions and leafhopper assemblages of 21 restored grasslands and 21 regularly managed sites (control) within the largest area of calcareous grasslands in the northern part of Germany. Furthermore, we applied Generalised Linear Mixed-effects Models (GLMM) to assess the effects of environmental parameters on species richness of leafhoppers within the restored grasslands. After a period of three to eight years, the restoration measures had led to species-rich leafhopper assemblages, including both habitat specialists and threatened species. However, we still found clear differences in leafhopper composition compared to the control. Within the restored grasslands, a pronounced field layer and an increased number of host plants positively affected species richness. In conclusion, the restored grasslands form open fringe-like habitat structures that clearly enhance the conservation value of calcareous grasslands by (i) harbouring numerous exclusive (indicator) species leading to a higher leafhopper diversity at the habitat level and (ii) by providing habitats for several habitat specialists which occurred only rarely on control grasslands. In order to maintain or even increase the biodiversity of calcareous grasslands, we recommend a combination of traditional grazing and small-scale shrub cutting.