Ecological restoration by soil transfer: impacts on restored soil profiles and topsoil functions

International audienceA last resort means to restoring a severely degraded ecosystem can involve soil transfer, especially when destruction of an undegraded system has been previously independently planned. We measured the impact of different soil transfer treatments that varied in vertical and orderly reconstitution of the main soil horizons on the microbial activity and organic matter composition during restoration of a Haplic Cambisol in a steppe ecosystem. There were differences between the topsoil of the reference ecosystem and the soil transfer treatments in terms of physicochemical parameters and microbial activity, but this was not the case when topsoil was not replaced at the soil surface. Three years following restoration, the transferred topsoil treatment, where the three main soil layers were transferred, contained lower particulate organic matter content than the steppe reference soil, despite similarity in potential carbon mineralization. Soil profile descriptions revealed strong differences in overall organization between the transferred soil and the undisturbed steppe soil, particularly with respect to lower biological activity and a lack of connectivity between pedological horizons via the plant root systems and the earthworm activity in the transferred soil. This suggests that soil transfer conducted to retain soil horizons provides good results when the topsoil is transferred, but it may result in altered biological activity, profile morphology, and organic matter content compared with the reference system