| Three Gorges Reservoir is the large Water Control Project in our country。It is vital importance for us to development,protection and management of Gorges Reservoir。Three Gorges Dam reservoir will formed the fall of 30 meters and the area of 300 km2 of the water-level-fluctuating zone in 2009, which is mainly located in the 145m-175m of the reservoir sea level. Each year in may and June, the water level of water-level-fluctuating zone remained at a low water level 145 meters, the water level gradually increased to 175 meters on October and maintained to 12 months, January to April of the following year dropped to 156～160m, by the end of May water level fell to 145 m. The water-level-fluctuating zone will show the cyclical and anti-seasonal features every year. The soil of the water-level-fluctuating zone will be soaked by the cyclical change of water level and the occurrence of alternating wet and dry, which may change the soil structure, resulting in soil erosion, so that the soil erosion increased in water-level-fluctuating zone.Soil degradation and soil erosion produce serious threat on the survival and development of human society, triggering a series of ecological and environmental problems. The typical water-level-fluctuating zone in small river basin as the research object, the paper analyzes the soil corrosion resistance characteristic of water-level-fluctuating zone; and further study soil aggregate structure stability characteristics and the evolution of soil aggregates characteristic; discussed the relationship of soil aggregates and organic carbon. The results are as follows:(1) The 15 indexes were used to analyze soil anti-erodibility by means of PCA and obtained the 4 categories of water-stable aggregate type, inorganic colloid type, aggregate type, and organic and index of soil water-stable type. PCA comprehensive exponent of anti-erodibility index can be calculated by offer rate of the four principal component factor. Through contribution rate of the principal component as the weight coefficient the can be composed. Soil erosion resistance index calculation equation of Three Gorges Reservoir (Y= 0.526Y1+0.277 Y2+0.107 Y3+0.091 Y4) Through correlation analysis showed that the soil organic matter content is very lower and not the main soil cement material, the main cement material is inorganic clay＜0.001 mm in The water level-fluctuating zone of the Three Gorges reservoir area.＞0.25mm water stable aggregate content,＜0.001mm clay content is good evaluation indexes of reflecting corrosion resistance.(2) The fractal dimension of size distribution of soil aggregate structure is smaller, water stable aggregates content is in large higher, water stable aggregates is in the lower damage rate, the soil structure stability is the better. The mean value of fractal dimension of surface soil aggregate is 2.85. The fractal dimension of Soil particle size distribution is affected by the content of fine particulate matter, fine particulate matter is more, the fractal dimension is greater; fine particulate matter less, the fractal dimension smaller. The mean value of fractal dimension of surface soil particle is 2.62. Fractal dimension of soil particle was negative correlation with fractal dimension of water stable aggregates.(3) Soil organic matter of the Fluctuating zone is mainly enriched in soil aggregates 0.25～0.5mm and 0.5～1mm. The ASI of soil aggregate 0.5～1mm and 1～2mm showed significant positive correlation with the content of soil organic matter, the correlation coefficient is extremely high. The content of organic matter of soil aggregates likely have a direct impact with the ASI of soil aggregates 0.5～1mm and 1～2mm. Through analysised, we discovered that soil organic matter, water stable index, fractal dimension of soil aggregate and aggregate stability index soil were positively correlation in each other,and with fractal dimension of soil water stable aggregates and＞0.25mm soil aggregate failure rate was a negative correlation in the surface.(4) Through trend map which is constituted by the A layer soil organic matter and＞0.25mm water stable aggregates content, and water stability index in the surface soil, organic matter content and＞0.25mm water-stable aggregate content, and water stability refers to changing trends in consistency in Fluctuating zone of the reservoir. The A layer of soil organic matter has a positive correlation with＞0.25mm water stable aggregates and water stable index. The soil organic matter content is the higher,the＞0.25mm water stable aggregates and the water stability index is higher. However, through trend changing map which is constituted by the B layer soils organic matter and＞0.25mm water stable aggregates, and water stability index in the Fluctuating zone, there is no consistent trend. The B layer of soil organic matter has not obviously correlation with＞0.25mm water stable aggregates and water stable index. Changes of soil organic matter content does not have all the impact of soil structure. The impact of elevation change is not very obvious.(5) By measuring organic matter content of the different size aggregates,it is showed that the maximum of organic matter content was distributed mainly in 0.25～0.5mm soil aggregate in the different size aggregates, the maximum value of the grain size aggregate is accounted for nearly 50 percent. The preservation probability of 0.25～0.5mm soil aggregate which was calculated by Path analysis has influence on decision coefficient of SOC, the decision coefficient is 0.2344. The content of organic matter has impact on preservation probability of soil aggregate. This indicates that the conclusions which was calculated by the Path analysis have a certain consistency with the actual measured results. Actual measured data and theoretical data of organic matter are different, the preservation probability of 1～2mm soil aggregate was smaller determination coefficient than the 0.25～0.5mm soil aggregate to SOC in theretical analysis. In actual measured results, content of organic matter of soil aggregate 0.5～1 mm is higher, the maximum value in content of soil aggregate(0.5～1mm)organic matter appear 9 times in various size.
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