Grazing, mowing, or abandonment? The importance of management heterogeneity for arthropod diversity in Western Carpathian grasslands

Species-rich semi-natural grasslands across Europe are threatened by land-use intensification and abandonment, and their conservation depends on appropriate management. Arthropod responses to management are complex and taxon-specific, yet multi-taxon evidence from grassland biodiversity hotspots remains scarce. We investigated the effects of four traditional management regimes (sheep grazing, sheep grazing combined with burning, mowing, and temporary abandonment) on the abundance, species richness, and community composition of arthropods in semi-dry grasslands of the Western Carpathians, a region of exceptionally high biodiversity. Using a long-term manipulative field experiment replicated in two regions in Czechia, we analysed fine-scale responses of six dominant arthropod taxa, including predators and herbivores: arachnids (Arachnida), true hoppers (Auchenorrhyncha), true bugs (Heteroptera), orthopteroid insects (Orthoptera, Blattodea and Dermaptera), leaf beetles (Coleoptera: Chrysomelidae) and weevils (Coleoptera: Curculionoidea). Grassland abandonment over 8–12 years increased the abundance and species richness of predators (arachnids and predatory true bugs) and the abundance, but not species richness of some herbivores (true hoppers and weevils), while negatively affecting both abundance and species richness of other herbivores, notably leaf beetles. All taxa exhibited significant shifts in species composition following abandonment. Abandoned plots supported some species of conservation importance, but many characteristic and flagship species of species-rich submontane grasslands were associated with regularly managed plots. After approximately ten years of continuous management, rotational sheep grazing and annual mowing had similar effects on arthropod abundance and species richness, except for true hoppers, which were more abundant and species-rich in grazed plots. However, arthropod community composition differed between grazed and mown plots for all analysed taxa, indicating that grazing and mowing are not ecologically interchangeable. Prescribed burning provided no additional benefit to grazing and negatively affected species of conservation concern. Our results indicate that conserving arthropod diversity in species-rich grasslands requires a heterogeneous mosaic of low-intensity management regimes, reflecting historical land use in the Western Carpathians rather than uniform management practices.