[Soil organic carbon pool and its spatial distribution pattern in the Circum Bohai Region]

The research and management of soil carbon pool and the effect of land-use on it are the key project of study on global change. In this paper, the data of 1,374 soil profiles in the Circum Bohai Region were used to estimate the soil organic carbon (SOC) pool of this region. The results showed that in this region, the total soil organic carbon pool in 1 m depth was 2.1 Pg C, and the biggest SOC pool was brown soil, occupying 55.6% of the total SOC. The second one was moisture soil, accounted for 26.9%. The SOC pools of aeolian sandy soil and dark brown soil were very small, only about 0.1% of the total. However, the soil organic carbon density (OCD) of boggy soil was the biggest (22.90 kg C.m-2), the second was dark brown soil (16.04 kg C.m2), and the lowest were aeolian sandy soil (2.88 kg C.m-2) and solonchak (6.0 kg C.m-2), implying that desertification and salinalization could reduce soil organic carbon. Moreover, the results also suggested that the topsoil held 673.30 Tg C. It meant that there was about one-third of the total SOC could be easy to be disturbed. According to the OCD at its level distribution gradient, it could be divided into four regions, i.e., coastal region, plain region, northwestern region, and hilly region. The order of OCD from high to low was hilly region, northwestern region, plain region, and coastal region. This regulation reflected not only the role of climate and landform, but also the effect of human activity intensification on SOC. Therefore, it was very important to protect and manage the land in this region well for the SOC maintenance and the sustainable land use.