Abstract:Taking Dongxiang County of Jiangxi Province as a study area, the contents of active, slow, inert soil organic carbon (SOC) and the corresponding proportions of total SOC were analyzed in the soil subgroups on the basis of the three pool theory of SOC and the culture experiments of soil respiration experiments, and then the distribution contours of three SOC fractions of active, slow and inert SOC were obtained with the proportion data aforementioned and another 229 samples collected by grids throughout Dongxiang County. The results showed that the active SOC contents of the four subgroups of Submergenic, Hydragric, Gleyed paddy soil and red soil were 0.54, 0.72, 0.72 and 0.33 g/kg, and the corresponding proportions in total SOC were 2.78%, 2.83%, 2.91% and 2.57%, respectively. The slow SOC contents of four subgroups were 7.57, 9.79, 12.34 and 4.72 g/kg, and the corresponding proportions in total SOC were 41.09%, 45.25%, 46.24% and 37.12%, respectively. The inert SOC contents of four subgroups were 10.36, 11.22, 13.49 and 7.67 g/kg, and the corresponding proportions were 60.31%, 56.13%,51.92% and 50.67%, respectively. From the spatial distribution, the contents of active, slow, inert SOC were all decreased from southeast to northwest in Dongxiang County. The contents of active and slow SOC contents of the three subgroups of paddy soil were all higher than that of red soil subgroup. This indicates that the paddy soil is not only the main soil type to carbon sequestration, but also a potential carbon source in hilly red soil region of southern China. The total SOC of red soil is very low, although with higher inert SOC content proportion, and its carbon sequestration ability need to be further improved.