Changes Of Soil Carbon Pool In Typical Areas Of Changjiang Drainage Basin And Carbon Sequestration Potential

Soil carbon pool is an important part of global surficial carbon pool, which will influence global climate change as a carbon source or sink for greenhouse gases. Taking areas covered by the Regional Multi-purpose Geochemical Survey(MPRGS) in the Changjiang drainage basin as an example, the soil carbon density and soil carbon storage and their changes has been calculated by combining MPRGS data and the Second National Soil Survey data, analyzed the factors that caused the carbon sinks and sources were analyzed and quantified soil organic carbon sequestration potential in cropland.The paper analyzed the soil carbon pool structure of study area show that the soil carbon pool is mainly organic carbon, the soil depth of 0~20cm, 0~100cm and 0~180cm corresponding to the soil organic carbon storage(SOCS20, SOCS100 and SOCS180) are respectively 1510.22 Tg C, 4975.20 Tg C and 7902.54 Tg C.The paper analyzed the spatial distribution of soil organic carbon density in the study area by spatial interpolation method. The results show that the Longmen, the surrounding region of Guiyang, southern region of Hunan and the surrounding region of Taihu had higher soil organic carbon density(SOCD), while southeast region of Sichuan, the surrounding region of Chongqing and the eastern coastal region of Jiangsu had lower SOCD. In the study area, dark-brown earths, cinnamon soils, mountain meadow soils and yellow earths had higher SOCD, while tidal flats, coastal solonchaks, purplish soils and cumulated irrigated soils had lower SOCD. In different land use types, grassland had highest SOCD, followed by woodland, while tidal flats had lowest SOCD.The paper contrasted soil data of the 21 st century and 1980 s show that except tidal flats and marsh, SOCD of other land use types tended to increase. From the point of view of the total, the woodland and paddy had higher carbon sequestration, its 148.84 Tg C and 114.10 Tg C respectively, second is grassland, its 22.96 Tg C. According to the paper statistics, the amount of soil carbon in the study area increase is about 312.38 Tg C. SOCD of the most area in the study area were significantly increased, especially in the Longmen Mountain region of western Chengdu, southern region of Ya’an and the surrounding region of Guiyang. While the area of Chongqing-Yijiang along the Changjiang, Neijiang-Chengdu-Leshan region of the Chengdu plain, the surrounding area of Zhenjiang-Gaochun showed a trend of decrease.The paper analyzed the effect of soil physicochemical properties, land use change, climate change and soil erosion to soil organic carbon in the study area. In various influence factors, the main factors leading to soil carbon increasing in the study area is the growth of woodland grassland and the increasing of agricultural cultivation. Climate change is an important reason which lead to soil carbon sources in the study area. While the land use changes had little effect on soil carbon pool. Soil erosion factors had no effect to paddy in the study area, but it had obvious effect to farmland. In addition, other factors lead to soil carbon pool increased 181.07 Tg C, but the specific reasons need further analysis.The paper used the model formula to calculate soil carbon sequestration potential(SOCDP) of cultivated field in the study area. The results show that SOCDP of Guizhou and the northern region of Hunan was low, in the case of constant environmental conditions, the region may become the soil carbon source and release carbon in the future. While SOCDP of Hubei and Anhui was generally high, soil carbon sequestration potential of the region is higher. With different soil types, yellow earths, bog soils and purplish soils will become carbon source in the future and other soil types will be soil carbon sink. From the point of view of the total amount of carbon sequestration(SOCSP), SOCSP of yellow-brown earths and paddy soils was higher, while yellow earths, bog soils and purplish soils will lose more soil carbon in the future, we should take protective tillage or change the land use types to mitigate the soil carbon source.