Soil erosion at three experimental sites in the Mediterranean

The results of erosion studies carried out at three representative sites in the European Mediterranean basin are discussed. The objectives of the stud y are to clarify the underlying processes affecting soil erosion and to qua ntify erosion and runoff in the framework of mitigation of land degradation . The study was carried out at three instrumented field stations using simi lar layouts and experimental set-ups and harmonized field procedures. Runof f and sediment yield from bounded plots were measured for different types o f land use for longer periods. The runoff and sediment values were found to be relatively low, and showed average annual values between 2.0 and 8.9 l m(-2) for runoff, and between 2 0.2 and 28.1 g m(-2) for sediment yield. The results show that the individu al plot response on an event basis shows no relationship between runoff and sediment yield for two of the three sites. On an annual average basis a si gnificant relationship is found between the runoff and sediment yield. Sign ificant differences were observed between different types of land use, espe cially between semi-natural vegetation, burned and abandoned field cover ty pes on the one hand, and agricultural fields on the other hand. The runoff and erosion values were lowest for the semi-natural fields. It was found th at in noncultivated fields the bounded plots might suffer from depletion of available sediment. It can be concluded that erosion figures are very low for the sites studied , and that the maintenance of semi-natural vegetation may help in the preve ntion of runoff generation and erosion. It can be concluded that the use of bounded plots may not be as ideal as might be expected from its wide appli cation. In some cases open plots, especially under seminatural land use, ma y produce much better results, especially when measuring over longer period s. Copyright (C) 1999 John Wiley & Sons, Ltd.