Dynamic Change Of Organic Carbon Storage In Reversion Process Of Desertification In Arid Regions

In order to study the organic carbon storage of the reversion process of desertification, at the South Edge of the Tengger Desert, chose the moving dune(MS), enclosure for 5 years(5a), enclosure for 15 years(15a) and enclosure for 25 years(25a) of the restoration successive series, and take the natural vegetation(NV) as the comparison, the variation of vegetation-soil properties, vegetation(including litter)carbon storage, soil organic carbon storage and soil CO₂ flux were determined in the restoration successive series and the comparison plot with the method of substituting time with space. The result indicate that:(1) The desertification restoration process is the vegetation restoration process. in the reversion process of desertification, the succession of vegetation types is from the annual herb community into semi-shrub community, semi-shrub and perennial herb community; The species abundance increases gradually; the dominant species is also from the annual herb evolution into semi-shrub and the perennial herb; the total biomass, the ground biomass and the underground biomass increased first and reduced later of various stages,the sample enclosed for 15 years reach the maximum, however, the ratio of the underground biomass to the ground biomass actually gradually increases of Various stages.(2) The desertification restoration process is the soil formation process. In the reversion process of desertification, the soil moisture content reduced first and increased later of various stages, but lower than that of the native vegetation; The sand content and the soil bulk density reduced gradually, while all were higher than those of the native vegetation; The silt content, the clay content and the soil porosity increases, while all were lower than those of the native vegetation; The soil pH elevates gradually, and Which of the sample enclosed for 25 years closed to that of the natural vegetation; The soil conductivity of the moving dune, the sample enclosed for 5 years and the sample enclosed for 15 years is steady with the depth change, Which of the sample enclosed for 25 years fluctuate obviously, but is lower than the native vegetation; The soil organic matter (carbon) content elevates gradually, and the difference is remarkable (P <0.05).(3) The desertification restoration process is the organic carbon storage elevation process. In the reversion process of desertification, the ground vegetation carbon storage increased first and reduced later of various stages, the sample enclosed for 15 years reach the maximum; the underground vegetation carbon storage, the soil organic carbon storage and the total organic carbon storage increase gradually, but were lower than the sample of native vegetation; the surface layer is higher than the deep layers of the soil organic carbon storage density, and all increase gradually; the samples of enclosed 15 years ago, the difference of the surface layer( 0-5cm)soil organic carbon storage is remarkable, Afterward there is no obvious difference.(4) The soil respiration and carbon emission is essential link in the carbon cycle. In the reversion process of desertification, the soil CO₂ flux peak appears at 10:00 AM in the growing season and non-growing season of the soil CO₂ flux diurnal variation; the soil CO₂ flux were positive number in the growing season, the average of the soil CO₂ flux diurnal variation increase gradually, but which of the sample enclosed for 25 years is higher than the sample of native vegetation; the average of the soil CO₂ flux diurnal variation increased first and reduced later in the growing season, the sample enclosed for 15 years reach the maximum, but lower than the sample of native vegetation; overall, the soil CO₂ flux has the obvious seasonal characteristics of various stages, the growth season is higher than the non-growth season.(5) The organic carbon storage closely related with the vegetation factors and the soil factors. In the reversion process of desertification, it is significant positive correlation between the organic carbon storage and the species abundance, herb cover of vegetation factors; it is significant or extremely significant correlation between the total organic carbon storage, the soil organic carbon storage and the soil bulk specific gravity, the sand content, the silt content, the clay content, the soil porosity; it is significant correlation between the vegetation carbon storage and the sand content, the silt content, the clay content; and it is significant correlation or extremely significant correlation between the total organic carbon storage, the soil organic carbon storage, the vegetation carbon storage and soil electrical conductivity, soil organic matter.