Résumé
Liming was used as a mitigation strategy to counteract the acidification of forest soils due to decades of acidic atmospheric deposits. An experiment was carried out to evaluate the effects of liming on an endemic earthworm species (Aporrectodea velox) and on the associated soil physical and chemical properties in a forest located in the Vosges Mountains (North-Eastern France). Two limed beech forest plots (one plot limed for 3 years and the other for 20 years before the study) were compared to a control plot receiving no liming treatment. We evaluated the medium (3 years) and long-term (20 years) effects of liming on the earthworm community (density, biomass) and activities (cast production and burrow system), as well as on the endemic species population in relation to the soil's physico-chemical properties. Liming induced a marked change in humus type: moder in the control plot, mull-moder in the medium-term limed plot and mull in the long-term limed plot. A significant increase in pH (from 4.1 to 4.7) and an increase in base cation concentrations (Al3+, Fe3+, Mn2+) were recorded in the organic horizons in the limed plots. Moreover, a decrease in acid cations, carbon, and nitrogen concentrations was also observed in both limed soils. Epigeic earthworms (Dendrodrilus rubidus and Lumbricus rubellus) dominated the earthworm community in the control plot, both in terms of density and biomass, while the large anecic endemic species A. velox dominated the community in the two limed plots. Greater amounts of surface casts, soil aggregation, and macropore density were found in the limed plots, thus showing an improvement in earthworm activity due to liming. By improving the litter, humus, and soil properties, liming constitutes an efficient and sustainable strategy to mitigate soil acidification and base cation depletion, even over a long-term time scale. This improvement appeared to promote the settlement of the endemic A. velox population and, in turn, increase the soil bioturbation due to its high casting and burrowing activities.