Does vineyard abandonment negatively affect the taxonomic and functional diversity of ground-dwelling beetles?

Abstract In recent decades, severe declines in biodiversity have been observed globally, with agricultural intensification being one of the key drivers. However, the abandonment of traditional land-use practices may also negatively affect diversity. Setting aside steep-slope vineyards, driven by heavy workloads and diminishing profitability, may pose a major challenge to biodiversity conservation and related ecosystem services in Germany. Here, we compare ground-dwelling beetle taxonomic and functional diversity across four management categories: (1) conventionally managed vineyards, (2) set-aside vineyards that are now managed as grazed grasslands, (3) set-aside vineyards that are now managed as mown grasslands, and (4) vineyard fallows. Using pitfall traps, we examined 10 sites per management category along the Upper Middle Rhine Valley in southwestern Germany. We show that conventionally managed vineyards and grazed grasslands exhibited the highest species richness, taxonomic and functional diversity, while fallows showed strongly reduced values. The same applies to the ‘conservation value’ of beetle assemblages, being highest on conventionally managed vineyards and grazed grasslands but lowest on fallows. Especially open landscape and xerothermic beetle species were negatively affected by abandonment. Beetle diversity was additionally affected by landscape composition, with (semi)-natural habitats having positive effects. Thus, our findings suggest that conventionally managed vineyards can provide valuable habitats for taxonomically and functionally diverse ground beetle communities, and that grazing represents an appropriate alternative for set-aside sites. Implications for insect conservation Our results show that some sort of management is important to halt secondary succession in xerothermic landscapes to preserve landscape heterogeneity and promote ground-dwelling beetle diversity. To this end, grazing seems to be especially suitable.