黄土丘陵区不同地貌单元土壤有机碳空间变异的尺度效应

运用地统计学和GIS相结合的方法，研究了黄土丘陵区县域不同地貌单元土壤有机碳空间变异的尺度效应，尺度划分为县域、县域上三种不同的地貌单元以及与地貌单元相对应的乡镇尺度，结果表明：①各个尺度下有机碳含量均偏低，完整地貌单元尺度与乡镇尺度有机碳均值与变异系数大小顺序不同；②高山区随着尺度的变化，自然因素对变异的影响程度没有显著变化，但低山丘陵区与丘陵沟壑区自然因素的影响程度减小，插值图表现出较小的研究面积有机碳含量信息更丰富；③县域尺度上海拔与土壤类型是导致变异的主控因素，在丘陵沟壑区，所研究的自然因素（海拔、土壤类型、土壤侵蚀程度、田面坡度、坡向）对其影响都不显著；在低山丘陵区，地貌单元上主控因子是海拔与土壤类型，而乡镇尺度上转化为田面坡度；在高山区，地貌单元上主控因子是土壤类型，但乡镇尺度上其主要影响因素变为土壤侵蚀程度。

Scaling Effect on Spatial Variability of Soil Organic Carbon in Different Geomorphic Units on the Loess Hilly Region

The scaling effect on spatial variability of the soil organic carbon (SOC) of cropland in different geomorphic units were studied in Zhuanglang County on the Loess Hilly Region by using a geostatistics method combined with Geographic Inform System (GIS)，the scales included county scale, complete geomorphic unit and town scale. The results showed that: 1) Soil organic carbon content was low in different scales on the study area. The order of mean and the variation coefficient of organic carbon content in complete geomorphic unit and town scale was different. 2) As the research scale changed, the impact of natural factors on the variance of SOC did not significantly change in high mountain region, whereas it changed obviously in hilly and gully region where the influence of random factors increased with the decrease of the study area. The rates of nugget to sill were 0.08 and 0.41 respectively in complete geomorphic unit and town scale of hilly region, whereas in the high mountain region they were 0.16 and 0.10 respectively. For example, the smaller the area, the interpolation information about organic carbon content was more abundant. 3) The elevation and soil type were the main influencing factors of SOC spatial variation on the county scale. In gully region, all the factors were not significant between the complete geomorphic units and the town scale. In the hilly region, the main factors were the altitude and the soil type on the complete geomorphic unit scale, but on town scale it was the slope gradient of field surface. In the high mountain region, the main controlling factor was soil type on the geomorphic unit scale, but the town scale was the soil erosion degree.