Abstract: 【Objective】 Moisture regime plays a crucial role in the mineralization of soil organic carbon (SOC). In this paper, the differences in SOC mineralization under aerobic and submerged conditions of paddy soils were studied. 【Method】 With incubation under aerobic and submerged conditions in laboratory, the dynamics of SOC mineralization in typical paddy soils of Changshu, Jiangsu Province, was investigated. 【Result】 The daily mineralization of SOC under different moisture regimes was significantly different in the whole incubation period. The daily mineralization of soil organic carbon decreased quickly at the beginning of the incubation under aerobic condition, but increased rapidly under submerged condition, and both kept constant after 10 days’ incubation. The differences in SOC mineralization were found to be mainly at the beginning period of the incubation and decreased along with the incubation time. Thus the difference was not significantly different at the later incubation time. The respiration intensity, daily and cumulative mineralization of SOC under aerobic condition were 2.26-19.11, 0.96-2.41, and 0.96-2.41 times those under submerged condition, respectively. Statistic analyses showed that the higher the contents of microbial biomass carbon and nitrogen, the more significant difference in respiration intensity between aerobic and submerged conditions, but the higher the contents of microbial biomass nitrogen and dissolved organic carbon, the more significant difference in daily mineralization of SOC between the two conditions. 【Conclusion】 The decrease in soil microbe activity under submerged condition was the main reason leading to the decrease in respiration intensity, but the decrease in SOC mineralization was also correlated with the changes in dissolved organic carbon over the whole incubation period.

Key words: paddy soil')">paddy soil, soil organic carbon mineralization, aerobic condition, submerged condition, difference