Distribution characteristics of soil organic carbon in northern slope of alpine meadow steppe in Qilian mountains in Qilian County, Qinghai Province

In order to evaluate the distribution characteristics of soil organic carbon (SOC) in the alpine meadow and steppe of Qilian county, the combined methods of field sampling and laboratory analysis were employed to analyze the variation of SOC in alpine meadow and steppe of Qilian county in altitude between 2 963 and 3 392 m. The results showed that there was very significant difference (P<0.01) between the contents of SOC in different soil depths (0-10, 10-20, 20-30, 30-40 and 40-50 cm) which decreased with increasing soil depth. The density of SOC had same variations with the contents of SOC which also very significantly decreased with increasing soil depth. SOC had significant positive linear relationships (P<0.01) with both herbage production and vegetation coverage. The content of SOC increased with increasing of herbage production and vegetation coverage. There was significant negative linear relationship (P<0.01) between SOC and soil bulk density. Soil moisture decreased with increasing soil depth, therefore, the contents of SOC had significant positive linear relationships (P<0.01) with soil moisture.