The Research Of Soil Organic Carbon Storage In Natural Grassland Ecosystem In The Loess Plateau

With global climate change and the development of terrestrial ecosystem carbon cycle research, scholars have paid much attention to carbon storage of grassland ecosystems. Grassland as one types of the most widely distributed vegetation on earth has some impact and response on global climate change. Grassland ecosystem, an important component of terrestrial ecosystems, plays an important role in the process of carbon cycling in terrestrial ecosystems. At present most research about the organic carbon in grassland ecosystems mostly based on census data, remote sensing data or model estimates, while the experimental data is penurious.Distribution of soil organic carbon (SOC) content and organic carbon density(SOCD) and their affecting factors in four different types of natural grasslands (forest steppe, typical grassland, alpine meadow steppe and desert steppe) in the Loess Plateau were analyzed and the soil organic carbon storage of the natural grassland in central Loess Plateau were calculated. Results are as follows:(1) Soil organic carbon content decrease with soil depth on Loess Plateau, it is significantly higher in 0²0 cm than in 20⁴0 cm, 40⁶0 cm, 60⁸0 cm and 80¹00 cm. The changes are different in different type of grassland. The Alpine meadow steppe decreases the fastest while the desert steppe decreases the slowest. The SOCD of typical grassland and alpine meadow steppe decrease with soil depth; with depth, the SOCD of forest steppe increasing at first and then decreasing and increase at last; the SOCD of the desert steppe has the smallest variation with the depth. In the whole layer of 0¹00 cm, the coefficients of variation of soil organic carbon density are different in four types of grassland. The coefficient of variation of SOCD in typical grassland is the largest while that in the Alpine meadow steppe is the minimum.(2) In the 0⁴0 cm soil layer, the distribution of organic carbon content in the four types of grasslands tends to be in the order of Alpine meadow steppe>typical grassland>forest steppe>desert steppe; while in the 40¹00 cm soil layer, in the order of Alpine meadow steppe>forest steppe>typical grassland>desert steppe. In the Alpine meadow steppe, forest steppe and typical steppe of the Loess Plateau, soil organic carbon is concentrated in the surface layer (0⁴0 cm), accounting for 71%, 50% and 46% of the total in the profile (0¹00 cm), while the distribution is more uniform in the desert steppe;(3) In Loess Plateau, the SOC and SOCD is positively related to altitude; but negatively related to annual mean temperature. In the 0⁴0 cm soil layer, SOC is positively related to soil water content; in the 0⁶0 cm soil layer, SOCD is positively related to soil water content.(4) In the horizontal direction, the distribution of organic carbon density is very uneven in the central Loess Plateau. From east to west, the SOCD increasing at first and then decreasing and increase at last. The distribution of organic carbon density in 0¹00cm soil layer in the four types of grassland tends to be in the order of Alpine meadow steppe>typical grassland>forest steppe>desert steppe, and the value are 18.30 kg·m^-2, 4.99 kg·m^-2, 4.69 kg·m^-2 and 1.50 kg·m^-2. The total area of natural grassland in central Loess Plateau is 2.02×107 hm2, and the soil carbon storage is 1.06 Pg C in 1 m depth.