Research On Carbon Sink Characteristics Of The Main Six Vegetation Ecosystems In The Southern Ningxia Of Loess Hilly Region

The southern Ningxia Province in the loess hilly region is key area of ecosystemrestoration and “Grain for Green Program” in China. To meet the requirement of rehabilitationbenefit assessment, this research taking southern Ningxia as case area, six main vegetationecosystems were studied inclouding vegetation, soil and carbon density, by analyzing thedistribution characteristics of carbon density in each of the components, combined withstatistics estimated carbon sequestration. The mian results are showed as follows:(1) Different vegetation types of different organs of carbon density and its distributionisdifferent, Prunus davidiana each organ carbon density distribution as follows: trunk>branch> root> leaf; Larix gmelinii each organ carbon density distribution as follows: trunk>root> branch> leaf; Three types of shrub plantations each organ carbon density distributionrule is: root> branch> leaf, each organ alfalfa artificial grassland carbon density distributionrule is: root> leaf.(2) The organic carbon content in soil layer between0-100cm reduced with the depth.Average order from large to small is: Prunus davidiana（7.96±0.25gC/kg)> Larix gmelini（6.69±0.31gC/kg)>Prunus davidiana （6.41±0.69gC/kg)> agricultural(6.12±0.60gC/kg)>Hippophae rhamnoides,(6.11±1.06gC/kg)>Medicago sativ（5.54±0.62gC/kg）> Caraganakorshinski(4.64±0.13gC/kg).(3) The total carbon densities in the ecosystem dominated by plantations of Prunussibirica and Larix gmelini were85.10and106.12t C·hm-2.The distribution patterns of carbonsequestration were basically consistent in the order of soil> arbor> herb layer. The carbondensity of soil layers of Prunus sibirica and Larix gmelini plantations were accounted for86.38%and76.30%of the entire stored carbon within each of the respective ecosystem, whilearbor layer accounted for12.35%and20.46%, herb layer accounted for1.28%and2.28%. The total carbon density in the plantations of Hippophae rhamnoides, Caraganakorshinskii, and Prunus davidiana were63.29,52.82, and77.78t C·hm-2, respectively. Thedistribution pattern of carbon sequestration was basically consistent in the order of soil>shrubs> herb layer. The carbon density of soil layer of Hippophae rhamnoides, Caraganakorshinskii and Prunus davidiana plantations accounted for88.56%、87.79%and87.44%ofthe entire stored carbon within each of the respective ecosystem, while shrub layer accountedfor10.18%、11.25%and12.16%, herb layer accounted for1.26%、0.97%and0.40%.The ecosystem carbon density of ten years old artificial Medicago sativa grassland was61.39t C·hm-2. As the main part of the ecosystem carbon density, Soil layer carbon density(56.42t C·hm-2) accounted for91.90%of the ecosystem carbon density, followed by Medicagosativa（4.17t C·hm-2）, accounted for6.79%, other weeds only accounted for1.30%.(4) The total carbon storage of the “Green for Green Project” in Longde is1.30382million tC, including vegetation carbon storage of0.20265million tC, soil carbon storage of1.10115million tC. The economic value of carbon sink of the “Green for Green Project” inLongde is117.64185million yuan.Compared to that of the sloping cropland, carbon densities of P. sibirica (10a) and L.gmelini (11a) forest ecosystems increased by42.90%and78.46%, the P. Davidiana (8a)forest ecosystems increased by30.61%, and although the soil carbon stock of the Hippophaerhamnoides (8a) has decreased slightly, the carbon storage of the Hippophae rhamnoides (8a)increased by6.28%as a whole due to the accumulation of biomass carbon, the Caraganakorshinskii (8a) forest ecosystems decreased by11.30%, the ecosystem carbon density of10a artificial Medicago sativa grassland increased by3.09%.