Identifying the factors influencing of aboveground carbon density (ACD) in typical forests in south subtropical zone can provide theoretical support for optimizing regional forest carbon-sink management.Five typical forest types in Chongzuo,Guangxi Zhuang Autonomous Region,China,including Pinus massoniana,Cunninghamia lanceolata,Eucalyptus grandis×urophylla,Mytilaria laosensis pure stands,and conifer-broadleaf mixed forest,were investigated.Based on forest management inventory data,ACD was estimated using biomass-volume conversion equations,and the its driving mechanisms were systematically analyzed using structural equation modeling (SEM).The results showed that:1) forest type,age class,and stand density significantly affected ACD,while site quality class had no significant main effect.However,forest type,stand density,and site quality class all exhibited significant interactions with age class.2)ACD of the five forest types ranked from highest to lowest as follows:Mytilaria laosensis pure stand (68.10 t/hm2),Pinus massoniana pure stand (33.20 t/hm2),conifer-broadleaf mixed forest (32.40 t/hm2),Cunninghamia lanceolata pure stand (32.00 t/hm2),Eucalyptus grandis×urophylla pure stand (31.30 t/hm2).3) ACD increased consistently with stand age.Mean ACD values for young,middle-aged,near-mature,mature,and overmature stands were 13.7,31.6,35.8,42.2,and 51.8 t/hm2,respectively.4) SEM revealed that stand density,dominant height,and mean diameter at breast height were the predominant positive drivers of ACD across all forest types,all with positive effects.The effects of site factors on ACD varied among forest types.Compared with the other forest types,the Mytilaria laosensis pure stand and the conifer-broadleaf mixed forest were more sensitive to climatic and soil factors.whereas the pure coniferous stands were significantly affected by topographic factors.Optimizing stand ageclass structure and tree-species composition,maintaining a certain proportion of mature and overmature stands,and increasing the proportions of broadleaved and conifer-broadleaf mixed forests can increase aboveground forest carbon stocks.