Little differences of uncut refuge rotation frequency on arthropod communities in extensively managed meadows

Using modern mowing machines in extensively managed meadows has a dramatic impact on arthropod communities, threatening the biodiversity of one of Europe's richest ecosystems. More wildlife-friendly mowing practices must be adopted in order to mitigate this negative impact. Leaving an uncut grass refuge on 10−20% of the area of a meadow has been evidenced to benefit arthropods. However, adopting the right spatio-temporal rotation frequency of such refuges would be key. We experimentally compared the abundance and diversity of arthropods in refuges that were rotated after each cut, usually twice per year (within-year rotational refuges, WYRR), versus refuges that changed from one year to the other (between-years rotational refuges, BYRR). We focused on a broad spectrum of indicator taxa: Aranea, Coleoptera, Neuroptera, Heteroptera, Vespidae, Apoidea, Syrphidae, Orthoptera, Auchenorryncha, caterpillars and butterflies. Rotating the refuge location twice a year (WYRR) increased overall arthropod abundance by 13% compared to refuges rotated once a year (BYRR), while species diversity did not differ between the two regimes. Yet, the refuge rotation frequency affected the different arthropod groups in varying ways. Aranea and Apoidea abundances were 33% and twice higher, respectively, in WYRR, while Auchenorrhyncha and caterpillar abundances were up to fourfold and threefold higher, respectively, in BYRR. Species richness of flowering plants and forb cover were higher in WYRR than in BYRR. We therefore recommend rotating uncut grass refuges after each cut. However, as findings also revealed some antagonistic effects, we suggest, where possible, alternating between the two regimes at meadow or landscape scales to optimise benefits for the whole arthropod community in the long term.