Characteristic of Organic Carbon Density and Organic Carbon Storage in the Natural Grassland of Center Loess Plateau

Soil organic carbon(SOC),organic carbon density and organic carbon storage in four different natural grassland types(forest steppe,typical grassland,alpine meadow steppe and desert steppe) in the Loess Plateau were analyzed.Results indicate that the content of soil organic carbon decreases with soil depth and a diversity in different grassland types.The variation of soil organic carbon content with soil depth in alpine meadow grassland has the biggest amplitude,while the variation has the smallest one in desert grassland.Organic carbon density of four different grassland types are ranked as Alpine meadow grassland typical steppe forest steppe desert steppe.In the whole soil layer of 0～100 cm,the coefficients of variation of soil organic carbon density are different in four grassland types.The coefficient of variation of typical grassland is the largest while the Alpine meadow grassland is the minimum.In the horizontal direction,organic carbon density is unevenly distributed in the natural grassland of central Loess Plateau.The total area of natural grassland in the region is 2.02 × 107 hm2,and the soil carbon storage is 1.06 Pg C in 1 m depth.