干旱区生态环境知识资源中心

The central part of the Ebro basin is threatened by desertification under the scenario of climate change for Mediterranean areas. A survey to examine the pattern of soil erosion and sedimentation was carried out along a climatic and altitudinal transect extending from the centre of the basin to the northern divide in the Pyrenees. Soil redistribution rates were assessed by using fallout (CS)-C-137 measurements on representative areas that are presented as case studies. The central steppe is the most severely affected by erosion, as indicated by highly depleted Cs-137 levels. In the semiarid area, erosion mainly affects the slopes that are sparsely vegetated and the cultivated valley floors. In the Pyrenees, soils on steep slopes are quite stable under dense shrub or forest cover. On the sparsely vegetated slopes of abandoned fields, erosion is severe, particularly on south facing slopes. These case studies emphasize both the spatial contrasts in soil redistribution rates that can be found in Mediterranean areas and the intense erosion and sedimentation dynamics that can threaten the sustainability of soil and water resources.