Delayed mowing promotes planthoppers, leafhoppers and spiders in extensively managed meadows

1. Biodiversity-rich grasslands have been severely impacted by agricultural intensification. Although agri-environment schemes (AES) have been launched partly to combat grassland biodiversity erosion, they could neither halt nor revert it, and this calls for alternative solutions. 2. We carried out controlled experiments on the effects of three mowing regimes on the arthropod biodiversity of extensively managed meadows, testing whether alternative mowing regimes can improve AES effectiveness: (i) mowing according to the Swiss AES prescriptions, i.e. first cut not before 15 June (control meadows); (ii) first cut not before 15 July (delayed mowing); (iii) refuge left uncut on 10-20% of the meadow area, otherwise first cut not before 15 June. Leaf-and planthoppers (Auchenorrhyncha) and spiders (Araneae) were sampled before and after mowing during 3 years, which enabled testing for immediate (within season) and carry-over (1 year to the next) effects. 3. Regarding immediate effects, Auchenorrhyncha and Araneae increased in abundance under the delayed mowing regime, with densities 3.5 and 1.8 times higher, respectively, than in control meadows. Furthermore, a positive carryover effect was detected for Araneae density under the delayed mowing regime. The refuge mowing regime had no effect on abundance. Finally, no statistically significant changes were detected for species richness and diversity (Shannon index) after 2 years of manipulations. 4. We conclude that delaying the first cut in extensively managed meadows promotes these two taxa. It could be easily implemented by slight adjustments of the extant grassland AES.