Carbon Stock Assessment in Sonneratia apetala Afforested Mangroves: A Case Study from Cox’s Bazar, Bangladesh

Abstract

Sonneratia apetala is a key species for mangrove afforestation projects in Bangladesh and plays a crucial role in ecosystem restoration and carbon sequestration. The research on how the total carbon stock (TCS) varies across S. apetala plantations in Cox’s Bazar remains limited. Thus, in this study, the biomass and soil carbon stock were quantified across nine S. apetala afforested sites in Cox’s Bazar to assess spatial variation and influencing factors. The total biomass carbon (TBC) was calculated by summing the aboveground (AGBC) and belowground (BGBC) biomass carbon, while the soil organic carbon stock (SOCS) was determined from the 0–40 cm soil depth. Descriptive statistics, ANOVA, Pearson correlation, and multiple linear regression (MLR) were used to analyze spatial differences and identify key predictors of carbon stocks. The results revealed notable variation in tree and soil parameters across the sites. Although tree height and diameter at breast height (DBH) varied among the sites, the variation was not statistically significant (p > 0.05). In contrast, the SOC content and bulk density (BD) significantly differed (p < 0.001), whereas the pH, salinity, and total nitrogen (ToN) content remained statistically similar (p > 0.05). The SOCS ranged from 13.04 ± 6.17 to 17.42 ± 5.18 t ha^-1, whereas the TBC ranged from 28.26 ± 26.34 to 53.82 ± 45.36 t ha^-1. The MLR results revealed that BD was a significant predictor of SOCS (p < 0.05) at most of the sites. Despite variations in TBC and SOCS, TCS did not vary significantly (p > 0.05), with TBC contributing 63.8% to 79.4% of the total stock. Correlation analysis indicated that TCS was influenced mainly by tree height, DBH, and soil nutrients, whereas salinity and pH had minimal effects. These insights may support improved mangrove management in climate change mitigation and adaptation strategies.