基于均匀抽样调查的半干旱黄土区土壤侵蚀动态研究

An Analysis on Dynamic Changes of Soil Erosion in Semiarid Loess Area Based on Uniform Sampling

为评估近年来植被恢复对土壤侵蚀强度动态变化的影响,按照1%的均匀抽样比例分别于2009和2011年调查了陕北吴起县39个小流域的土壤侵蚀影响因子,结合2009年SPOT多光谱影像遥感解译的土地利用结果,分析了抽样方法的精度和吴起县土壤侵蚀动态变化及其影响因素。结果表明:(1)1%的抽样比例能够很好地代表吴起县整体土壤侵蚀状况;(2)2009—2011年吴起县微度侵蚀等级面积比例显著增加,中度、强烈、极强烈和剧烈侵蚀等级比例均有不同程度的减少,强烈侵蚀和剧烈侵蚀的面积比例都减少了5%以上,但不同小流域的土壤侵蚀变化差异较大;(3)土壤侵蚀变化的原因主要是2011年降雨侵蚀力低于2009年;与2009年相比,2011年灌木林面积减少,而草地和林地面积增加,但各种类型植被的覆盖度都有增加,因此,植被因子明显减小。其他因子变化不大。

The aim of this study is to assess the effect of vegetation restoration on soil erosion dynamic changes in recent years. Based on the uniform sampling（1 ~//00）, the impact factors of soil erosion were surveyed in a9 watersheds in Wuqi County, Northern Shaanxi Province in 2009 and 2011 respecitively. With the compari- son of land use interpreting result from 2009 SPOT multi-spectral image, the accuracy of the sampling meth- od, soil erosion dynamic changes and the impact factors were analyzed in Wuqi County. The results showed that. （1） The 1 % uniform sampling ratio could well represent current situation of soil erosion in Wuqi Coun- ty. （2） From 2009 to 2011, the area of slight erosion increased significantly, while the proportion of moder- ate, intensive, extreme intensive and severe erosion has reduced in varying degrees. All the areas of intense erosion, extreme intensive and severe erosion decreased by more than 5 %, while the erosion intensity varied significantly within the single watershed. （3） The main reason that causes soil erosion changes was the rain- fall erosivity, which was smaller in 2011 than in 2009. Compare to 2009, although the area of shrub land decreased, the area of grassland and all the other types of vegetation cover increased in 2011. Due to this, the soil conservation biological factor decreased, and the changes of other factors were small.