不同降雨量下的黄土高原土壤侵蚀特征分析

Soil Erosion Characteristics under Different Precipitation Conditions in Loess Plateau

利用地理信息系统技术对黄土高原土壤侵蚀空间数据和降雨量等级数据进行了空间叠加统计分析。研究表明,在降雨量等级为1时,黄土高原土壤侵蚀主要以水-风混合侵蚀为主,占整个侵蚀的55.76%。在降雨量等级为2和3时,水蚀和风蚀占整个侵蚀的比例较接近。在降雨量等级为4、5和6时,主要以水蚀为主,分别占整个侵蚀的82.54%、98.66%和99.53%。在降雨量等级为7时,土壤侵蚀全部为水蚀,占整个侵蚀的100%。冻融侵蚀出现在降雨量等级为2到6时,占整个侵蚀的比例均不大。在降雨量等级为4时,水蚀、风蚀和水-风混合侵蚀的土壤侵蚀指数均比其它降雨量等级的土壤侵蚀指数大,分别为406.84、665.94和723.78,土壤侵蚀最严重。黄土高原降雨条件的变化对土壤侵蚀状况的变化表现出明显的影响。

The distribution of soil erosion has obvious characters of spatial change, and studying the spatial change law is important for scientific prevention of soil erosion. Loess Plateau, situated at E100°52′～114°33, N33°41′～41°16, is a part of Northwest China. For a long time, severe soil erosion not only has produced a great impact on agriculture in this area, but also silted up the reservoirs and riverbeds in the lower reaches, so it has been becoming the most important cause seriously damaging the ecological system of the Loess Plateau and the near areas. The main factors affecting soil erosion are precipitation, topography and vegetation. The precipitation is classified seven grades and there exists a close relation between the precipitation and soil erosion in Loess Plateau land-scale. The relationship of the precipitation and soil erosion in Loess Plateau is discussed through using the spatial overlay statistics for the soil erosion and precipitation data based on Geographical information system. The results show that the soil erosion exist under different precipitationconditions in Loess Plateau, water-wind erosion accounts for 55.76%of all kinds of erosions in precipitation grade 1. The proportions of water erosion andwind erosion are approximate in precipitation grade 2 and 3. Water erosion dominates from precipitation grade 4 to grade 7, accounting for 82.54%, 98.66%, 99.53%and 100%, respectively. Frozen erosion distributes from precipitationgrade 2 to grade 6. Water erosion, wind erosion and water-wind erosion indices in precipitation grade 4, being 406.84, 665.9 and 723.78, respectively, are bigger than those in the rest precipitation grade. These results can provide scientific evidences for the protection, utilization, recovery and reconstruction of Loess Plateau and demonstrate the effectiveness of studying the relationships ofthe precipitation and the soil erosion by combination of Geographical Information System and landscape ecological method.