Abstract: The effect of land use change on terrestrial ecosystem carbon pools is a hot topic in current global climate change research. Most of previous studies have focused on the estimation of soil organic carbon pools at the regional scale, but overlooked the response of soil organic carbon (SOC) components to land use change in subtropical mountainous areas and their underlying mechanisms. We explored the effects of land use types on the contents of SOC components across three typical forests in the Dongjiang Lake Basin, namely subtropical secondary forests, plantation forests and economic forests. Results showed that land use type did not affect total SOC, C∶N ratio and mineralassociated organic carbon (MAOC), but significantly affected particulate organic carbon (POC). In the 10-30 cm layer, POC content of economic forests was 37% and 41% lower than plantation forests and secondary forests, respectively. The lower POC in economic forests were associated with lower aboveground biomass. Our results demonstrated that converting economic forests into secondary forests or plantation forests may reduce the risk of soil organic carbon loss and is beneficial for enhancing the carbon sink function of mountainous soil and the carbon sequestration potential of regional forests in the Dongjiang River Basin. These findings enhance our mechanistic understanding of carbon sequestration in forest soil, and provide data support for optimizing regional land management models and improving the carbon sequestration potential of forest ecosystems.

Key words: plantation forest, secondary forest, land use change, particulate organic carbon, mineral-associated organic carbon