Abstract: Dynamics of soil organic carbon mineralization affected by long-term fertilizations and temperature in relation to different soil carbon fractions were investigated in paddy soils. Soil samples were collected from the plough layer of 3 longterm national experimental sites in Xinhua, Ningxiang and Taojiang counties of Hunan Province. Mineralization of soil organic C Symbol`@@was estimated by 33-day aerobic incubation at different temperatures of 10, 20 and 30 ℃. The results showed that the rates of CO₂ production were higher during the earlier phase (0-13 d) in all treatments, and then decreased according to a logarithm function. Higher incubation temperature strengthened C mineralization in the different treatments. The quantities of cumulative CO₂ production in NPK with manure or straw treatments were greater than in inorganic fertilizers treatments. The Q₁₀ values in the different soil treatments ranged from 1.01-1.53. There were significantly positive correlations between the Q₁₀ values and soil total organic carbon (TOC), easy oxidation organic carbon (EOOC), humic acid carbon (C_HA), fulvic acid carbon (C_FA). The cumulative amount of mineralized C was significantly positively correlated with microbial biomass carbon (MBC) at 10 and 20 ℃, but not significantly at 30 ℃. Significant correlations were found between the cumulative
amount of mineralized C and different soil carbon fractions and C_HA/C_FA. The correlations of different soil carbon fractions with the ratio of cumulative mineralized C to TOC were negatively correlated at 10 ℃, but not significantly at 20 and 30 ℃. These results suggested that the application of NPK with manure or straw would be helpful to increase the sequestration of C in paddy soils and reduce its contribution of CO₂ release in the atmosphere.