Carbon sequestration of Caragana korshinskii shrubs surface soil in different desertified grassland of desert steppe

To understand the soil organic carbon evolution under the long-term effects of Caragana korshinskii in desert steppe，taking 6 kinds of grassland with different desertification gradient: natural grassland（T1）， sierozem grassland（T2），crusts grassland（T3），fixed sand dune grassland（ T4），semi-fixed sand dune grassland（ T5），mobile sand dune grassland（ T6） as research objects，to analyze the soil carbon sequestration in internal and external of shrubs with large，medium and small crown. The results showed that：（1）In internal and external of C. korshinskii shrubs，the lowest TOC contents was in the mobile sand dune grassland（ P<0.01），the highest was in the natural grassland（ P<0.01）. The highest AOC content was in the crusts grassland with internal of shrubs（ P<0.01），the existence of internal of shrubs played an important role in AOC sequestration.（ 2）The large，medium and small crown of C. korshinskii were compared，the results showed that in the internal of shrubs，on the whole，the highest TOC，AOC and NOC contents were in the medium crown of C. korshinskii（P<0.01），medium crown was a turning point of C. korshinskii soil organic carbon accumulation，it was the most concentrated expression of“ fertile island effect” with internal of shrubs. In the external of shrubs，TOC and NOC of small crown in the crusts grassland and mobile sand dune grassland were higher than those in the large crown significantly（ P<0.01），the variation of AOC was opposite. It suggested that soil carbon sequestration showed a decreasing trend after a increase，the best soil carbon sequestration was in the medium crown of C. korshinskii. C. korshinskii soil carbon sequestration effects were the integrated action of C. korshinskii and crusts grassland.