Abstract: Coastal wetland restoration is an important measure to improve the blue carbon function in the coastal zone. Zhejiang Province has continuously carried out a series of large-scale mangrove introduction and afforestation projects, while the carbon sink capacity and influence factors of high-latitude artificial mangroves need to be studied. In this study, the soil organic carbon (SOC) content, organic carbon stock and their vertical distribution characteristics of theKandelia candel forests with different ages were investigated. The SOC content and stock in the mangroves were also be compared with the Spartina alterniflora salt marsh and bare mudflat. The results showed that the SOC content and stock were the highest in the adult mangroves, and the SOC content and stock of mangroves and salt marshes were significantly higher than those in the mudflat. The SOC content in salt marshes is higher than that in the young mangroves, while the SOC stock in the young mangroves are higher than that of salt mars, because of higher soil bulk density (BD) in the salt marshes than that in the young mangroves. The SOC content and stock in the different habitats show the distribution characteristics of first increasing and then decreasing with the soil depth, reaching the highest values at the soil depth of 20‒50 cm. Site location and habitat type had a significant relationship with SOC content and stock, with significant interaction between site location × habitat type. Dissolved oxygen (DO) in pore water, soil total nitrogen (TN), soil pH and pore water salinity were significantly associated with the SOC content. The results of this study can provide scientific basis and data support for assessing the carbon sequestration potential of artificial mangrove forests after northward migration, as well as wetland protection and restoration strategy.

Key words: Coastal wetland, Mangrove, Exotic plants, Soil organic carbon, Carbon stock