3.4. Total Carbon Stocks
The total carbon stock of the Sofala Bay mangrove forest is 218.34 Mg·ha−1
(Table 4), around 85%
of which is stored below-ground (73.28% in the soil and 11.55% in the roots). Our results are
supported by the findings of Kauffman et al. [51], who also found similar fractions of carbon stock in
mangrove soils of some Federated States of Micronesia. In other studies, soil carbon accounted for
72%–99% [8,14] and 40%–98% [8] of the total mangrove ecosystem carbon. These values show the
role of mangrove soil as an important carbon pool. However, our findings show that the total
carbon storage in the mangrove forest is lower compared to those reported by other authors e.g.,
Mudiyarso et al. [14], who recorded an average of 986 Mg·ha−1
of total carbon in Indonesia whereas
Bosire et al. [30] recorded an average of 534 Mg·ha−1 of total carbon in Zambezi Delta, in central
Mozambique. These differences may be associated to differences of tree species composition and
forest structure, density of trees, forest conservation status, soil depth, carbon concentration, and soil
water content in each region. For instance, the structure of mangrove trees of the Zambezi Delta,
dominated by Sonneratia alba (Sm.) with trees growing up to 45 cm DBH and 27 m height [29,30] is
clearly different from our study site dominated by relatively small trees of Avicennia marina with a
dominant height of 4 m. Fatoyinbo et al. [29] also suggest that mangrove productivity, as expressed by
tree biomass, would vary with the quality of the upstream sediment, therefore, taller mangrove trees
are found in nutrient rich sediments of the Zambezi Delta and Limpopo estuary.