A complex relationship between cropping systems and soil macrofauna: Influence of practice intensity, taxa and traits

Larger soil organisms have often been reported as the most sensitive to disturbances caused by cropping practices. However, soil macrofauna comprises groups with a wide diversity of morphological and ecological features, which may respond differently to applied practices. In order to further assess the effect of cropping systems on soil macrofauna, macrofauna organisms were extracted from soil blocks over 21 fields (each comprising three plots) located in the Paris basin, in autumns 2020 and 2021. Fields belonged to conventional, conservation or organic systems, either long-established (≥ 7 years) or in transition (≤ 3 years). Tillage, pesticide treatment and organic matter input intensity were assessed in each field using composite indexes of practice intensity. Macrofauna density and diversity, earthworm ecological categories, species richness and functional traits were investigated. Our results showed that the density and diversity of macrofauna demonstrated few differences regarding different cropping systems, with highly variable effects across groups and years. Specific macroarthropod groups responded differently to tillage, pesticide treatment and organic input intensity, but not over the two years of the study. Regarding earthworms, high tillage intensity had a negative effect on the density and biomass of epi-anecic juveniles and on species with a small body size. Higher organic matter inputs had a negative effect on the density and biomass of endogeic earthworms, and could be related to several earthworm functional traits (body length, mass/length ratio, carbon preferences). Effects of pesticide treatments were less clear, although they could have impacted some earthworm species. More generally, taxonomic and functional trait approaches of earthworm community led to similar conclusions. Overall, our results support the need to account for (i) the actual intensity of practices in cropping systems and (ii) the different taxonomic, trophic and ecological groups of macrofauna, in order to assess the effects of cropping systems on soil biodiversity.