Decomposition rates of soil organic carbon under four kinds of vegetations in granite area of Xinzhai Village in Guilin,China

【Objective】 The characteristics of decomposition rates of soil organic carbon under different vegetations in granite area were studied to provide scientific references for soil carbon sequestration effect.【Method】 Through indoor soil culture,the 0-20,20-40 and 40-60 cm soil layer of 4 types of vegetations(woodland,dry land,orchards and shrubs) were chosen in Xinzhai Village of Guilin.Cultured for 100 days at 25℃ under the conditions of 70% water content in field,the content of CO2-C released from the soil organic carbon was determined.【Result】 The decomposition rates of soil organic carbon under 4 types of vegetations generally descended with the increase of soil layer depth,more specifically,the decomposition rates was initially faster,slower later,and finally leveled.The sequence of accumulative content of CO 2-C released in soil layer was 0-20 cm20-40 cm40-60 cm.Regarding the proportion of CO 2-C released by soil organic carbon decomposition to their total organic carbon,the highest ratio was the dry land,up to 3.34%-4.84%,followed by the woodland(1.82%-2.88%) and the orchard(1.91%-2.16%).The lowest was the shrub(1.77%-1.98%).The soil organic carbon of 4 types of vegetation was significantly positively correlated to total nitrogen,organic matter content,and soil urease activity.Concerning the average turnaround time of activated carbon,the longest one was the shrub,and for the average turnaround time of slow carbon,the slowest one was the dry land.【Conclusion】 Since the soil organic carbon pools of the orchard,shrub and woodland relatively contain more components difficult to decompose,and soil organic carbon under the three kinds of vegetations is relatively stable with effect of carbon sinks.