Effects of moso bamboo expansion into subtropical <italic>Machilus thunbergii</italic> forest and <italic>Cryptomeria japonica</italic> forest on soil labile organic carbon

<bold>Objective</bold> It has become an important ecological issue that the wide-spread expansion of moso bamboo has caused functional degradation and landscape changes in adjacent forest ecosystems.However，it is not yet clear how moso bamboo expansion affects forest soil labile organic carbon（LOC）and its components ［soil dissolved organic carbon （DOC）and soil microbial biomass carbon （MBC）］. <bold>Method</bold> In this study，typical sample transects where <italic>Phyllostachys edulis</italic> expands into <italic>Machilus thunbergii</italic> forests and <italic>Cryptomeria japonica</italic> forests were selected as the research objects in the subtropical region.Through field sampling and laboratory analysis，the study investigated the effects of moso bamboo expansion on the adjacent forest LOC，and its relative proportion to the soil organic carbon （SOC）. <bold>Result</bold> The expansion of moso bamboo into <italic>Machilus thunbergii</italic> forests has no significant effects on the MBC and SOC，but it significantly reduces the LOC，which was mainly attributed to the reduction of the DOC.In addition，the expansion of moso bamboo into <italic>Machilus thunbergii</italic> forests reduces the proportion of DOC and LOC in the SOC pool，thereby reducing the turnover rate of the LOC pool，which is beneficial for the long-term sequestration of SOC.The expansion of moso bamboo into <italic>Cryptomeria japonica</italic> forests increases MBC，but it reduces SOC，and it has no significant effect on DOC and LOC.Moreover，moso bamboo expanded to <italic>Cryptomeria japonica</italic> forests obviously increases the proportion of MBC and LOC in the SOC，thereby increasing the biological activity of organic carbon and the turnover rate of the LOC pool，which has the potential to accelerate the loss of SOC. <bold>Conclusion</bold> The results show that the effects of moso bamboo expansion on LOC is related with forest types，and it can be a potential factor that mediate the formation and stable of SOC.The research findings provide support for deepening the basic theoretical knowledge of the relationship between moso bamboo expansion and the carbon cycle.