中国土壤有机质含量变异性与空间尺度的关系

The Relationship between the Spatial Scale and the Variation of Soil Organic Matter in China

以中国土种志资料为基础,分析了土壤有机质含量变异与空间尺度的关系及土类内和土类间的变异程度,探讨了不同空间尺度单元下,土壤有机质平均含量与土壤性质的相关性。结果表明,以土壤剖面为单元,随着土壤剖面数的增加,土壤有机质含量的变异系数增大;行政区域尺度单元内部土壤有机质变异程度大于单元间土壤有机质含量的变异程度。以土壤分类单元为空间单元,土类内的有机质含量变异程度小于土类间的变异程度。随着统计单元空间尺度的增大,土壤有机质含量与土壤性质之间的相关性减弱。因此,采用网格法或行政区划分空间区域,获得空间区域单元内土壤有机质含量或贮量的精确估算需要较多的剖面,但外推至数据不足的空间区域时,估算的不确定较小;采用土壤分类单元为空间区域单元,结果则相反。

Based on the data from the National Second Soil Survey, this paper analyzed the relationship between the variation of soil organic matter and the spatial scales, the variation within and among soil groups, and discussed the correlation between the soil properties and the average content of soil organic matter at various spatialscales. The results indicated that the variation coefficient of soil organic matter content increased with increasing the number of soil profiles while individual soil profile was taken as a basic statistical unit, and decreased with spatial scale up while average of soil organic matter content in the defined scale was taken as a statistical unit. While soil taxonomy group was taken as the basic spatial unit, the variation coefficient of soil organic matter content within soil group was less than that among soil groups. The correlation between soil properties and soil organic matter content became less significant with spatial scale up. Therefore, when the grid technique or the district was applied to regionalize spatial scale, individual soil profile are needed more to reduce uncertainties of the estimate of soil organic matter in the grid or the district with spatial scale up, but the uncertainties are smaller when using soil organic matter content in well-estimate gird or district to estimate the grid or district without available data by extrapolation. When the soil taxonomy group was taken as the basic spatial scale, the result was reverse.