Expédit Evariste Ago

Floristic and dendrometric analysis of woodlands in the Sudano-Guinean zone: a case study of Belléfoungou forest reserve in Benin

Abstract A floristic and dendrometric analysis was carried out using 15 square plots of 1 ha each in the Belléfoungou forest reserve, located in the Sudano-Guinean zone of Benin. Species and diameter at breast height of trees were recorded. Multidimensional scaling and importance value index of species were used to identify vegetation types in the reserve: (1) Isoberlinia tomentosa-dominated vegetation type, (2) Isoberlinia doka and Burkea africana-dominated vegetation type and (3) Vitellaria paradoxa and Isoberlinia doka-dominated vegetation type. Significant differences were noted between the three vegetation types with respect to the basal area of trees. This varied from 8.55 m2/ha (vegetation type 3) to 13.36 m2/ha (vegetation type 2). The overall woody species richness was 57 species. The stem diameter structures of all three vegetation types showed an inverse “J” shape, suggesting that the study reserve has stable natural vegetation with relatively more young stems than large stems. Setting and implementation of a sustainable management plan, and supervision reinforcement were suggested to enable conservation of the Belléfoungou forest reserve.

Carbon Budget as a Tool for Assessing Mangrove Forests Degradation in the Western, Coastal Wetlands Complex (Ramsar Site 1017) of Southern Benin, West Africa

Carbon budgets were established for pockets of mangrove forests within the western coastal wetland complex of southern Benin (Ramsar site 1017) using standard methods. We assessed carbon stocks in four (0.1 ha) transects in sites with different levels of degradation of mangrove vegetation from non-forested, very degraded, degraded, to non-degraded mangroves in Kpetou, Djegbadji, Adounko (1), and Adounko (2) sites, respectively. Species encountered were typical of the west-central African region: Avicennia germinans, Rhizophora racemosa, Acrosticum aureum (fern), and Paspalum vaginatum. The maximum diameter was 24.8 and 20.3 cm for Avicennia and Rhizophora, respectively, in non-degraded mangrove sites, at a maximum height of 21 m. Standing volumes varied from 6.55 m3/ha in degraded mangroves to 50.42 m3/ha in the non-degraded mangrove sites. The total annual carbon stock, to a soil depth of one meter, varied from 179.39 t/ha in the non-forested site, to 288.77 t/ha in degraded mangroves and 184.01 t/ha for non-degraded mangroves. Aboveground biomass carbon in non-degraded sites was on average 35.07 t/ha, more than five times that in degraded mangrove sites. The distribution of total ecosystem carbon stocks for the aboveground component for the mangrove sites ranged from 0.82 % for non-forested sites, 2.94 % for degraded to 16.01 % for non-degraded mangrove forests. The belowground carbon stocks component ranged from 179.39 to 288.77 t/ha, being the highest in degraded mangrove sites due to leached organic matter following degradation. Potential annual net CO2e emissions from up to 30 cm soil depth (compared to non-wooded mangrove vegetation) is estimated to increase from 10.28 to 99.64 t CO2e (22 % of non-wooded mangroves) following mangrove degradation and 43 t CO2e (10 %) avoided CO2e emissions from undisturbed mangrove forests.