黄土沟壑丘陵区退耕对土壤侵蚀影响的模拟研究

Simulation on Effects of Land Use Change on Soil Erosion on Loess Plateau

随着在黄土沟壑丘陵区退耕政策的实施,退耕必将对该地区的水土流失特征产生重大影响。对退耕的水土保持效益进行模拟研究,可为退耕政策的合理实施提供理论依据。选定位于黄土沟壑丘陵区的安塞研究区,在RS和GIS支持下,采用USLE,模拟研究了不同退耕方案对土壤侵蚀的影响。在2001年土地利用的遥感解译图和GIS计算分析基础上设计了8种不同的退耕方案,模拟结果显示,各种退耕方案对土壤侵蚀的减少主要发生在强度及强度以上侵蚀区,退耕后研究区已没有发生剧烈侵蚀的区域,强度和极强度侵蚀明显减少;土壤侵蚀量的减少主要发生在≥25°退耕和≥15°退耕,≥25°退耕还草和还林分别使土壤侵蚀总量减少了19.9%和23.2%,≥15°退耕还草和还林分别使土壤侵蚀总量减少了36.6%和42.6%。≥8°退耕方案和全部退耕方案与≥15°退耕方案相比,水保效益并没有显著差别。

In the gully and hilly areas of Loess Plateau, with the cropland being returned to woodland or grassland, it is sure that the characteristics of soil erosion will be influenced greatly. To provide theoretic basis for the above-mentioned policy, it is necessary to simulate the effects of the cropland returning on soil and water loss. In this paper, part of Ansai county was selected as the test area, which is located in the gully and hilly areas of the Loess Plateau. By use of the USLE combined with RS and GIS, the effects of cropland returning on soil erosion were simulated. Based on the land use pattern in 2001, 8 cropland returning scenarios were designed. The results indicate that the soil losses from areas where intensive erosion or more intensive erosion occurs decreased most markedly. For all the cropland returning scenarios, there are no areas where severe erosion occurs and the soil losses from areas where intensive erosion and very intensive erosion occur decreased markedly. Of all the cropland returning scenarios, 25° or more steep cropland returning and 15° or more steep cropland returning are the scenarios under which the total soil losses decrease most markedly. Under the scenarios of 25° or more steep cropland being returned to grassland and to woodland, the total soil losses decrease 19.9% and 23.2% respectively; under the scenarios of 15° or more steep cropland being returned to woodland and to grassland, the total soil losses decrease 36.6% and 42.6% respectively. Compared to the scenarios of 15° or more steep cropland returning, there is no marked difference in terms of the effects on soil erosion under the scenariosof 15° or more steep cropland returning and all cropland returning.