Diversité des communautés de microarthropodes dans des sols agricoles (Sud-Ouest de la France) : influence des facteurs environnementaux et bioaccumulation de métaux traces

Abstract

International audienceCultivated soils are under the influence of mechanical tillage and diffuse metal pollution of anthropogenic origin from atmospheric deposits and agricultural inputs. Communities of microarthropods (springtails and oribatid, gamasid and actinedid mites), living in surface horizons, play an essential role in the soil functioning. This work aims to assess the influence of some agricultural practices, physico-chemical characteristics and metal contamination on the structure and specific richness of microarthropod communities. The main types of agricultural soils, representative of current agricultural activities in the Midi-Pyrénées region, and the associated microarthropods were sampled. Physico-chemical parameters and total concentrations of trace metals (Cr, Ni, Cu, Zn, Cd and Pb) in soils and microarthropods were determined, as well as the fraction of labile metals using sequential extractions and EDTA chemical extraction. The results indicate that land cover influences the diversity and abundance of microarthropods. Indeed, cereal crop soils have a lower abundance and diversity of microarthropods than grassland, vineyard or orchard soils. Moreover, a positive and significant correlation was demonstrated between the total organic carbon and total nitrogen contents of the soil and the abundance of microarthropods. On the contrary, mites and springtails are not impacted by the trace metal concentrations measured in agricultural soils. The ability to bioaccumulate metals in microarthropods is mainly related to trophic levels, with gamasid and actinedid mites (predators) accumulating more than springtails and oribatid mites (detritivores). Finally, the accumulation of metals, partly regulated by their availability in the soil, is also dependent on their affinity and toxicity for microarthopods, in particular for groups of detritivores. Consequently, the communities of microarthropods, and in particular the springtail populations, are of interest, due to their bioaccumulation capacity, for evaluating the levels of trace metals in agricultu-ral soils and can serve as a bioindicator of the impact of disturbances in the soil related to soil tillage and agricultural practices