Abstract: Soil carbon cycle is the focus and hotspot of the studies on global environment change. Relationship between the vertical distribution of soil organic carbon and its affecting factors was explored, especially in arid zone. In this study, the vertical distribution of soil organic carbon under different land cover types in northern piedmont of the Tianshan Mountains was studied based on the data of second national soil survey. The results showed that the mean soil organic carbon density in soil layer of 0-100 cm in depth varied from 3.65 kg·m^-2in land with sparse vegetation to 35.73 kg·m^-2in alpine and subalpine meadow. The vertical distribution of soil organic carbon density was quite different from different land cover types: the proportion of soil carbon density in soil layer of 0-20 cm in arable land accounted for 32.2% of the total soil carbon density in topsoil layer of 1 m in thickness, it was higher than 40% in alpine and subalpine meadow, forest and intrazonal vegetation surface, and lower than 37% in desert vegetation and bare land and land with sparse vegetation, in which it was 25.4% only in bare land and land with sparse vegetation. The average difference of soil carbon density between adjacent soil layers was lower than 8.1% in arable land and lower than 4.0% in bare land and land with sparse vegetation.

Key words: font-family: 宋体, mso-bidi-font-family: 宋体, mso-font-kerning: 1.0pt, mso-ansi-language: EN-US, mso-fareast-language: ZH-CN, land cover')">mso-bidi-language: AR-SA">land cover, soil organic carbon, vertical distribution, northern piedmont of the Tianshan Mountains