Organic carbon storage and distribution characteristics of different stand types soil in southeastern Guangxi

【Objective】To explore the composition characteristics and distribution rules of soil organic carbon stocks of typical stand types in southeastern Guangxi, and provide theoretical basis for understanding the role of forestry carbon sequestration in coping with climate change, and promoting carbon cycle in terrestrial ecosystem and the development of forestry carbon sequestration. 【Method】Cunnighamia lanceolata, Castanopsis hystrix and Eucalyptus grandis×urophylla plantations were studied in Bobai Forest Farm. The bulk density, organic carbon density, organic carbon content and organic carbon storage of soil of different stand types and the contribution rate of soil organic carbon in different soil layers were measured by field sampling and laboratory analysis, and the characteristics of soil organic carbon storage and vertical distribution of main stand types in southeastern Guangxi were discussed. 【Result】There were obvious differences in soil organic carbon density among the three typical stands in southeastern Guangxi. The average soil organic carbon density of C. hystrix plantation was the highest（4.50 kg/m²）, and that of E. grandis×urophylla plantation was the lowest,which was significantly lower than other types（P＜0.05, the same below）; soil organic carbon density in each stand decreased gradually with soil depth. The soil organic carbon content of E. grandis×urophylla plantation was significantly lower than C. hystrix and C. lanceolata, and the soil organic carbon content of the three stands gradually decreased with the depth of the soil layer. The soil organic carbon density of the three stand types was ranked as C. hystrix plantation＞C.lanceolata plantation＞E. grandis×urophylla plantation.The soil organic carbon storages of C. hystrix plantation and C. lanceolata plantation were 135.13 and 133.41 t/ha, which significantly greater than that of E. grandis×urophylla plantation.The contribution rate of soil organic carbon storage in different soil layers of the three stand types gradually decreased with the depth of the soil layer. 【Conclusion】Among the three stands, the soil organic carbon content and storage of C.hystrix plantation and C. lanceolata plantation are higher than that of E. grandis×urophylla plantation. In the process of plantation transformation, selecting long-term C. hystrix and C. lanceolata is more conducive to the accumulation and fixation of soil organic carbon storage, which has better soil carbon sink benefits.