Plant diversity, population structures and carbon stock of mangrove ecosystems of Ramsar Site 1017 in Benin
摘要
Mangroves in Benin are facing rapid degradation as a result of anthropogenic disturbances. Since Benin adopted the Ramsar Convention on Wetlands conservation treaty, several projects have been carried out to promote the sustainable conservation of mangroves at Ramsar Site 1017. However, how these initiatives have sustained the conservation of mangrove ecosystems remains largely unknown. In this study, species composition, tree density, structure, natural regeneration and carbon stock of mangrove ecosystems were investigated to assess the impact of the management policies on mangrove conservation. Using the quadrat sampling method, 54 plots of 100 m2 were established along 10 transects of 200 × 10 m. Overall, 65 plant species were recorded, including ten tree species and seven endangered species. The Shannon diversity index (H′ = 1.57) indicated low tree diversity, while Pielou’s evenness index (Eq = 0.26) showed an uneven distribution of abundance among species. Of the ten tree species, Rhizophora racemosa, Avicennia germinans and Dalbergia ecastaphyllum were the most dominant. The total carbon stock was 175.10 ± 39.12 Mg ha−1, with 138.06 ± 31.28 Mg ha−1 from aboveground tree biomass and 35.75 ± 7.50 Mg ha−1 from belowground tree biomass. The mean tree density and basal area were 3018 trees ha−1 and 29.04 m2 ha−1, respectively. The diameter size class distribution (SCD) showed an inverted J-shape with 98% of tree species in the first three classes (1–30 cm), suggesting a sustainable management of the mangrove ecosystems. Moreover, the saplings and seedlings density was 1308 ± 46 trees ha−1 with a high proportion of saplings. It is evident that conservation efforts and long-term monitoring, as well as awareness raising among local communities, are needed for the management and preservation of mangroves.