Biomass and diversity of soil mite functional groups respond to extensification of land management, potentially affecting soil ecosystem services

Soil mites (Acari) are ubiquitous in soil ecosystems and show a vast taxonomic diversity with a wide range of life history characteristics and feeding strategies. Various taxa contribute directly or indirectly to soil processes, including nutrient cycling, soil formation and pest control. Mites thus support important ecosystem services of soils. Yet, their community composition, and therewith service provisioning, may differ between for instance intensively managed agricultural soils and extensively managed grassland soils. We therefore hypothesized that successional changes in the abundance and diversity of soil mite functional groups (feeding types) will occur following a conversion of arable land to grassland, affecting their contribution to ecosystem services.To test this, we studied the succession of mite communities on two Long Term Observatories (LTOs) in Lusignan (France) and Veluwe (the Netherlands). At Lusignan, sampling involved four combinations of recent and historic land use types. At the Veluwe, samples were taken in a secondary succession chronosequence in grasslands, representing a time frame up to 29 years after the conversion from arable land to grassland. Biodiversity and biomass were higher in grassland than in arable land, especially for the total mite community, the predators and the main taxa aiding in decomposition. After conversion of grassland to arable land, or vice versa, both taxon richness and biomass rapidly developed towards the prevailing conditions. Our results indicated that the taxon richness and biomass of the total mite community in grassland still continued to increase up to 29 years after the conversion from arable land to grassland. Total taxon richness increased with time since conversion, which was mainly due to the immigration of decomposers and predators. The biomass of different feeding guilds increased at variable speeds. The observed changes imply an increase in nutrient cycling and in the suppression of some potential pests. We discuss the relevance of these ecosystem services in extensively managed grasslands and agricultural systems. Furthermore, our results suggest that in agricultural rotational schemes that include one or more years of grassland, mite communities and associated ecosystem services may be partially, but not completely, restored to the conditions of long term grassland.