Impact of small-scale conservation management methods on spider assemblages in xeric grassland

International audienceSeminatural grasslands are among the most valuable habitats for arthropod conservation in Central Europe. The abandonment of traditional farming has caused these areas to become overgrown and homogeneous, thereby resulting in loss of arthropod biodiversity. This traditional farming therefore needs to be complemented by active conservation management methods. An important question is whether small-scale conservation management may support arthropod diversity and habitat specialists inhabiting abandoned seminatural grasslands. We investigated the effects of mowing, prescribed burning, mechanical turf disturbance, and absence of active management on species richness, functional diversity and composition, conservation value, abundance of Red List species, and assemblage composition of spiders. The management methods were applied on small-scale (4 × 5 m) patches in protected xeric grassland. Spiders were sampled using pitfall traps and sweeping during 2017 and 2018. A total of 11,634 specimens from 154 species were recorded, including many rare and threatened species. The temporal responses of spider assemblages to active conservation management depended on the particular group of spiders. Changes in assemblage composition and resulting shifts in the community weighted mean values were distinct in the second year of the experiment. Management had no significant effect on the species richness of ground-dwelling spiders. Mechanical turf disturbance shifted the assemblage composition of ground-dwelling spiders towards habitat generalist species. Vegetation-dwelling spiders had the highest species richness in unmanaged patches. Their functional diversity was lower in disturbed patches. Burnt patches supported species of conservation concern for both spider groups. Prescribed burning had positive results for most of the studied indicators. Nevertheless, mechanical turf disturbance had a rather negative effect on the spider assemblages. Our results indicate that even small, patch-like interventions with minimal costs can considerably support the valuable spider assemblages of xeric grassland in the intensified landscape of Central Europe