Pool Sizes and Turnover of Soil Organic Carbon of Farmland Soil in Karst Area of Guilin

The three-pool and first-order model separates the mineralizable organic carbon into active, slow, and passive carbon pools. This paper used the model and decomposition curves of the soil organic carbon to fit the active pool and its decomposition rate, slow pool and its decomposition rate. The results showed that the size of the active pool from different profiles accounted for 2.09%-3.08% of the total soil organic carbon and the mean residue time was 3.57-17.21 days. And the size of the slow pool accounted for 3.19%-43.55% and the mean residue time was 1.12-4.94 years. Acid hydrolysis (6M HCl) was used to fractionate the passive organic carbon, which accounted for 50.83%-94.44% of the total soil organic carbon.