On the base of first order dynamic model

combining with a laboratory soil incubation experiment

the dynamics of soil organic carbon(SOC) decompositions

three carbon pool sizes and average turnover time are analyzed

including swamp soil

meadow soil

othic yellow brown soil and brown rendzina.The results show that these four soil types total soil organic carbon are 8.48~24.53 g/kg in the surface soil and 4.02~16.77 g/kg in the subsoil.The size of active SOC pool from surface and subsoil respectively accounts to 0.99%~5.01% and 1.31%~1.91% of total soil organic carbon

and the average turnover time is 8.8~14.3 days.Slow SOC pool

15.88%~59.04% and 20.43%~48.36%

1.3~29.1 years.Passive SOC pool

39.97%~79.11%

50.31%~77.66%.All the three pool sizes of those four soil types are more in the surface soil than subsoil.Cumulative emission of CO2 during incubation for 91 days is 165.99~2 429.57 mg/kg in the surface soil and 108.04~743.02 mg/kg in the sub soil.Decomposition rate order of these four soil types is swamp soil

meadow soil

brown rendzina and othic yellow brown soil

which direct interrelated with active SOC carbon percentage content.Curve fitting of SOC cumulative release amount during incubation showed that cubic equation can describe change trend

and the correlation has reached high significant level(P<0.01).