Abstract: Dissolved Organic Carbon(DOC)in soil,as a vital active component of the soil carbon pool,plays a significant role in the carbon cycle of ecosystems,and its concentration is closely related to the overlying vegetation.This study investigates the effects of different afforestation tree species(Cunninghamia lanceolata,Phoebe bournei and Castanopsis kawakamii)on the content and vertical distribution characteristics of soil DOC in the mid-subtropical region,measurements were taken for soil physicochemical properties,litterfall and fine root biomass.The results showed that:① although there were no significant differences in soil DOC content among the three plantations,significant spatial heterogeneity was observed in the vertical distribution.Specifically,the Phoebe bournei and Castanopsis kawakamii plantations exhibited a surface accumulation pattern,with significantly higher DOC content in the topsoil(0—10 cm)than in the subsoil(10—60 cm,P<0.05);②soil DOC was significantly positively correlated with total nitrogen(P<0.05),revealing a strong coupling between carbon and nitrogen cycles in this forest ecosystem.However,it showed no significant correlation with soil bulk density,pH,mineral nitrogen,fine root biomass,or litterfall,indicating that the formation and transformation of DOC are regulated by the complex interactions of multiple environmental factors.Broad-leaved tree species(Phoebe bournei and Castanopsis kawakamii)are more conducive to promoting the accumulation of active carbon in the topsoil,which has positive implications for enhancing the soil carbon sink potential of plantations.