Abstract: 【Objective】Soil water plays a crucial role in the accumulation and mineralization of soil organic carbon (SOC). 【Method】 In laboratory, 14C-labelled rice straw was added into upland soil and incubated under 30%, 45%, 60%, 75%, 90% and 105% water holding capacity (WHC) at 25℃, 100% air humidity for 100 days. 【Result】The accumulative mineralized amount of added organic materials (AOM) and native SOC both increased as moisture content increased from 30% to 105% WHC, and their relationships were positively linear correlation (n=6, R2 =0.9174, P<0.001 and n =6, R2 = 0.9649, P<0.001, respectively). During 100 d incubation period, equivalent of 20-33 percent of AOM and 1.0-3.1 percent of native SOC were mineralized. The accumulative mineralized amount of AOM and native SOC were highest under 105% WHC conditions and the amounts were 146 ?g·g-1 and 0.76 mg·g-1, respectively, which were 1.68, 1.35, 1.40, 1.24, 1.16 times and 3.01, 2.04, 1.72, 1.40, 1.33 times to that in soils under 30%, 45%, 60%, 75%, 90% WHC conditions, respectively. 【Conclusion】 This is suggested that in laboratory incubation, the impact of soil moisture content on the mineralization of native SOC was more sensitive to the mineralization of AOM. Results also revealed that the increases in soil moisture content from 30% to 105% WHC will accelerate the mineralization of AOM and upland native SOC.

Key words: Soil moisture content, 14C-labelled rice straw, Soil organic carbon, Mineralization