On the sandy soils of Mamora, land degradation is in relation with the retreat of the cork oak forest. The runoff is normally inefficient, but it becomes very intense during the wet years after continuous rains, responsible of the saturation of the top horizons in the ploughed areas. The rills transport a great quantity of material. The sandy soil is also affected by wind which transports superficial materials during the dry years. Real signs of desertification appear in this region, at the boundary of subhumid environment.Dans la Mamora aux sols sableux, la dégradation des terres est en relation avec le recul de la forêt de chêne-liège. Le ruissellement, inefficace d'habitude, acquiert une intensité particulière lors des années humides, no...