中文摘要：

以2012-2013年调查的我国西北祁连山中段97个代表性土壤剖面为对象，分析了土壤有机碳（socl含量的剖面垂直分布模式，计算了1 m土体内各层次SOC相对含量及其与环境因素（年均降水、年均温度、海拔、坡度、坡向、NDVI）和土壤因素（颗粒组成、体积质量）之间的关系。结果表明：①SOC含量剖面垂直分布模式可分为均一分布型、表层聚集型、普通递减型、不规则分布型4个类型，SOC含量剖面垂直分布模式与选取的环境因素和土壤颗粒组成之间没有明显的关系；②SOC含量的变异较大，随着深度的增加从中度变异过渡到强度变异；NDVI和年均降水是影响表层土体SOC含量的主要因子，而黏粒和砂粒是影响下层土体SOC含量的主要因子。

英文摘要：

97 soil profiles were surveyed across the Qilian Mountains using a purposively sampling strategy. Verticalvariations in profiles of soil organic carbon （SOC） and their correlation with various environmental variables （mean annualprecipitation and temperature, altitude, slope gradient and aspect, NDVI） and soil attributes （particle size composition and bulkdensity） were analyzed. Results showed that there were 4 kinds of SOC profile distribution modes： homogeneous, surface-accumulated, gradually-decreasing and chaotic modes. Both SOC content and density had moderate to strong spatial variability,and the variation coefficient increased with depth. Analysis of random forest proved that the surface soil layer （0-20 cm） had thebest model performance with R2 reaching 0.68 and 0.52 for SOC content and SOC density respectively, and R2 decreased withincreasing soil depth. Moreover, the environmental factors of NDVI and mean annual precipitation were the main influentialfactors for variations of surface SOC content and density, but the influence of soil attributes on SOC content and density wasintensified with increasing soil depth.