Extensive semi-arid areas over mica schist in SE Spain have soils with a sandy loam texture, a poorly developed structure, a relatively high infiltrability and a quite high saturated hydraulic conductivity. Under non-tillage land use, a stony pavements armours the soil surface and is responsible for high infiltration, low runoff and almost negligible erosion. However, when this stony pavement is absent, and no plant cover is present, i.e. in tilled soils, this soil is very vulnerable to surface crusting and erosion. With the aim to ascertain the formation stages of this stony pavement as well as to know its hydrologic and geomorphologic behaviour, an experimental study has been carried out in a runoff plot under simulated rainfall. A laser micro-relief meter has been used to characterise the spatial distribution erosion-sedimentation patterns during the experiments, and soil micromorphology to characterise stony pavements and underlying sieving crusts. In the first stage of a rainfall event after the land has been tilled, runoff and erosion are very reduced because the newly created structure absorbs most of the water and the energy of raindrops progressively destroys clods, seals the surface, detaches and transports downslope most of the fine earth. In the subsequent stage, some minutes after the rainfall started, a physical surface crust develops, and runoff and erosion progressively increase. As rainfall continues, in a third stage, the progressive removal of fine particles from the surface leaves a residue of rock fragments and runoff and erosion decrease due to both an increase in infiltration and the armouring effect of the stony pavement.

Peer reviewed