The below-ground C stock was calculated by the sum of the sediment and the root C pools. Mangrove root mass was estimated by the
common allometric equations for the species A. alba, A. officinalis,
B. parviflora, and S. caseolaris (Komiyama et al., 2005), and the specific
equation for R. apiculata (Ong et al., 2004) (Table 1). The root C pool
was estimated by multiplying the root mass with C content. The sediment C pool was estimated up to 4 m in depth.Because the total organic C (TOC) content showed a lower coefficient of variation between 150
and 250 cm in depth, the TOC content over that depth range was averaged and applied to deeper sediment layers. The sediment C pool was
calculated following Eq. (1).