Characteristics of Soil Organic Carbon Fractions in Alpine Meadow with Different Degradation

In source area of the Yellow River,Yangtze River and Lancangjiang River in Qinghai province,China,a typical area of alpine meadow in Qingzhen town,Gande county was sampled in this study.Five types of sampling plots was classified according to different degraded degree(undegradation,light degradation,moderate degradation,heavy degradation,extreme degradation).Topsoil(0-30cm)samples were collected by interval sampling of 10 cm depth.Soil organic carbon and fractions contents were measured.The results showed that contents of soil organic carbon and carbon fractions were dramatically decreased with degradation aggravation and deep soil layer.Compared with the primary vegetation,under the conditions of slight,moderate,serious and extreme degradation,soil organic carbon content of topsoil(0-30cm)declined by 21.7%,38.8%,67.4% and 79.6%,respectively;light fraction of soil organic carbon declined by 22.8%、43.9%、68.8%and 81.2%,respectively,and heavy fraction of soil organic carbon declined by 21.4%,38.3%,67.0% and 79.0%,respectively.The percentage of soil light fraction organic carbon to organic carbon content ranged from22.02%to 27.04%,and the percentage of soil heavy fraction organic carbon to organic carbon content ranged from 72.96%to 77.98%,which meant that soil organic carbon content mainly distributed inheavy fraction.In general,topsoil soil organic carbon and organic carbon fractions contents changed dramatically in ecosystem degradation.Alpine meadow soil organic carbon content was decreased rapidly as degradation aggravation.Therefore,alpine meadow conservation is significant for the sustainable development of animal husbandry and the protection of terrestrial soil carbon stock in the areas of the Yellow River,Yangtze River and Lancangjiang River.