Soil carbon mineralization potential and its effect on soil active organic carbon in evergreen broadleaved forest and Chinese fir plantation

With incubation test,this paper studied the mineralization rate and cumulative mineralized amount of soil organic carbon(C),and the correlations of the mineralized organic C with the initial content of soil active organic C in evergreen broadleaved forest and Chinese fir(Cunninghamia lanceolata) plantation in Huitong region of Hunan Province.The results showed that the mineralization rate and cumulative mineralized amount of soil organic C were significantly higher in evergreen broadleaved forest than in Chinese fir plantation.At the 21st day of incubation at 9 ℃ and 28 ℃,the cumulative mineralized amount of soil organic C at the soil depths of 0-10 cm and 10-20 cm in evergreen broadleaved forest was 1.7-2.7 times of that in Chinese fir plantation.The proportion of CO2-C released from the mineralization of soil organic C was higher in evergreen broadleaved forest than in Chinese fir plantation.There were significant correlations between the mineralized amount of soil organic C and the initial content of soil dissolved organic C and microbial biomass C(P0.01).The mineralization of soil C increased soil microbial biomass C while decreased soil dissolved organic C,but the increment or decrement was not too great.When the incubation temperature raised from 9 ℃ to 28 ℃,soil C mineralization rate increased 3.1-4.5 times,and less difference was observed in the responses of the mineralization rate to temperature change between broadleaved forest and Chinese fir plantation.