三峡库区土壤有机质区域分布及影响因素

利用多目标地球化学调查方法，通过野外实地调查、大面积系统采集土壤表层、深层样品、测试分析和数理统计，探讨了三峡库区不同土壤类型深层和表层土壤中有机质含量分布特征。以紫色土为例探讨了不同分布高程、坡度和不同植被条件下对有机质含量的影响。结果表明：三峡库区土壤有机质含量总体上较低，均为矿质土壤。成土母质类型对土壤有机质含量影响明显，相同自然条件成土作用下，海相石灰岩母岩区的土壤有机质高于陆相砂、泥岩母岩区的土壤。在土地利用方式上，水耕模式有利于增加土壤有机质。地形高程、坡度对紫色土有机质分布影响明显，随着海拔高度的降低，紫色土有机质含量明显降低；随着地形坡度降低，土壤有机质明显升高。植被覆盖类型上，草丛区、阔叶林区有机质具有高于混交林区、灌丛区、针叶林区的趋势。紫色土有机质与P，S等元素呈极显著正相关，但与造岩矿物元素及母质来源的元素相关性差。

Distribution Characteristic of Soil Organic Carbon in Three Gorges Reservoir District

Base on testing results of top-soils and deep-soils,distribution characteristics of organic carbon(abbrev org.C) in soils were discussed by types of soils,elevations,degrees of slope,and vegetation covering.It can be concluded that soils in the Three Gorge Reservoir District belong to mineral soils,because of lower soil org.C.Under the same natural condition of pedogenesis,Parent rocks play an important role in distribution of org.C in soils.In the limestone area the soils are abundant in org.C.on the other hand,in the sandstone and mudstone districts the contents of org.C in the soils are lower.In terms of the degree of slope,the contents of org.C in the purple soils increase with the decline of the degree of slope.When the elevation decreases,the contents of org.C in the purple soils decline,too.When the parents rocks,climate and topography are similar,the contents of org.C in purple soils are determined partially by the type of vegetational cover.Soils in the tussock and broadleaf hurst areas contain more org.C relatively,than soils in the mixing forest,shrubbery and conifer forest areas.