Management of grassland: A necessary tool to maintain plant and earthworm diversity

In temperate grassland, earthworms contribute to the major soil processes which determine most of the ecosystem services. The characteristics of plant communities in grassland are key factors in maintaining earthworm communities, however effects of different herbage management on earthworms remain largely unknown. In this context, the aim of the present study was to determine the long-term effects of herbage management on grassland plant and earthworm communities. Plants and earthworms were sampled in a 14-years-old experiment in upland grasslands (Massif central, France). Abandoned grasslands were compared with mowed grasslands and with pastures grazed by cattle (at low or high intensities) or grazed by sheep (at low intensity). Compared to abandoned grassland, herbage management by grazing or by mowing display higher leguminous plant, community-weighted mean Ellenberg light values as well as plant richness while they display lower percentage of plant litter and community-weighted mean Ellenberg nitrogen values. The differences in plant richness were associated with a significant change in plant community structure. Compared to the abandoned grassland, herbage management by grazing or mowing significantly display higher earthworm biomass and total richness. Except for pastures grazed by cattle at high intensity, earthworm abundance was at least twice that in the grassland at low grazing intensity or mowing compared to the abandoned grassland. Earthworm communities were significantly different between grazed and mown treatments notably due to changes within Aporrectodea anecic and endogeic earthworm species. Overall, herbage management by animals or by mechanical export is beneficial for plant and earthworm diversity although no clear differences between management practices for earthworm richness, total biomass or total abundance were observed. Our results highlight that abandonment does not preserve biodiversity (plant, soil macrofauna) while management of grassland by grazing or mowing is a necessary tool for biodiversity conservation and improvement.