Abstract: This study aims to develop biomass prediction models for various organs, aboveground, belowground, and total plant biomass of the mangrove species Laguncularia racemosa (L. racemosa), thereby providing foundational data for carbon sink surveys based on L. racemosa biomass and the monitoring of introduced species in Hainan Island. It also offers methodological references for the rapid and accurate estimation of carbon storage in L. racemosa. The research focuses on L. racemosa forests and 1-meter-deep soils within the Black-faced Spoonbill Provincial Nature Reserve in Dongfang City, Hainan Province. Linear and power function biomass models were constructed using breast height diameter (D), tree height (H), and their composite variables (D², DH, D²H), and carbon density and carbon storage were compared across different intertidal zones. The results indicate that power function models generally provide better predictions than the linear models, and composite variables exhibit better fitting accuracy than single variables. Among these, the power function model using D² as the independent variable provides the best fit, with determination coefficients (R²) for organ biomass, aboveground biomass, belowground biomass, and total plant biomass generally exceeding 0.89. Based on the optimal biomass models, the total carbon storage ofL. racemosa in the study area is estimated to be 22,267.48MgC. The vegetation carbon density is 105.83MgC·hm⁻², with the highest organic carbon content observed in branches and flowers/fruits (approximately 44.98%), and the lowest in roots (38.21%). The soil carbon density (248.92MgC·hm⁻²) is significantly higher than the vegetation carbon density, accounting for 70.17% of the total carbon density. Carbon density in different intertidal zones ofL. racemosa forests is as follows: supratidal zone (455.13MgC·hm⁻²) > intertidal zone (399.98MgC·hm⁻²) > subtidal zone (209.15MgC·hm⁻²). Carbon storage is mainly concentrated in the soil layer, with significant variation due to site conditions and there are clear differences in carbon storage across different intertidal zones.

Key words: Laguncularia racemosa, biomass, linear model, power model, organic carbon, carbon storage