Abstract: As global climate change intensifies, mangroves, a vital coastal blue carbon ecosystem, have garnered increasing attention. This study aims to develop biomass models for juvenile mangroves and assess the carbon storage of young mangrove ecosystems in Kaozhou Bay. The results offer empirical methods and scientific basis for the rapid and accurate assessment of carbon stocks in artificial young mangroves. The study focuses on five artificial juvenile mangrove species in Kaozhou Bay: Avicennia marina, Rhizophora stylosa, Kandelia obovata, Bruguiera gymnorhiza, and Aegiceras corniculatum. Various factors derived from basal diameter (D) and tree height (H) were used to construct optimal allometric equations between biomass and dendrometric parameters. Additionally, the best biomass models for mangroves were used to evaluate the carbon storage of vegetation and the ecosystem carbon storage of the artificial planted mangroves in Kaozhou Bay. The findings indicate that multivariable models generally outperformed univariable models, with the exception of the belowground biomass model for Aegiceras corniculatum. The optimal biomass models for Avicennia marina, Rhizophora stylosa, Bruguiera gymnorhiza, and Aegiceras corniculatum were power function models, while the optimal models for Kandelia obovata were linear. The carbon density of the artificial young mangrove ecosystems in Kaozhou Bay was found to be 91.26±17.32 Mg C ha-1, with a total carbon stock of approximately 35964.65 Mg C. Soil carbon accounted for 78.3% to 98.5% of the total carbon stock in the artificial young mangrove ecosystems. Among the different mangrove communities, the carbon density of vegetation ranked as follows, from highest to lowest: Aegiceras corniculatum + Kandelia obovata community, Rhizophora stylosa + Avicennia marina community, and Avicennia marina community. These results provide valuable insights for the assessment of carbon storage and ecological restoration in artificial mangroves in Guangdong and even the whole country.

Key words: juvenile mangroves, biomass model, carbon density, artificially planted mangroves, Kaozhou Bay