Assessment of Mangrove Carbon Stocks in Cameroon, Gabon, the Republic of Congo (RoC) and the Democratic Republic of Congo (DRC) Including their Potential for Reducing Emissions from Deforestation and Forest Degradation (REDD+) - The Land/Ocean Interactions in the Coastal Zone of West and Central Africa - page 171

Assessment of Mangrove Carbon Stocks
in Cameroon, Gabon, the Republic of Congo
(RoC) and the Democratic Republic of Congo
(DRC) Including their Potential for Reducing
Emissions from Deforestation and Forest
Degradation (REDD+)

Gordon N. Ajonina, James Kairo, Gabriel Grimsditch, Thomas Sembres,
George Chuyong, and Eugene Diyouke

Abstract
We present results of the field assessment using a total of fifteen 0.1 ha mangrove permanent
sample plots (PSPs) in four selected countries in Central Africa, including: Cameroon,
Gabon, Republic of Congo and Democratic of Republic, which together account for 90 % of
mangroves in Central Africa. Above- and belowground carbon stocks were computed using
data from the PSPs in all four countries. Long-term monitoring data in Cameroon were used
to estimate carbon sequestration rates. Four major carbon pools were considered:
aboveground carbon, belowground root carbon, deadwood and the soil organic carbon. All
the eight mangrove species described in Central Africa were encountered in the study. The
dominant species in Central Africa is Rhizophora racemosa, and it occupies more than 70 %
of the forest formation. The average stand density ranged from a low of 450 tree/ha in
degraded forest of RoC to a high of 3,256 tree/ha in undisturbed stands of Cameroon.
Standing volume ranged from a low of 213 m 3 /ha in RoC to a high of 428 m 3 /ha in
Cameroon; corresponding to aboveground biomass values of 251 and 505 Mg/ha, respec-
tively. Together with the deadwoods, the total vegetation biomass in the study area ranged
from a low of 394 Mg/ha in RoC to a high of 825 Mg/ha in Cameroon. Mean diameter
increment for primary and secondary stems was 0.15 cm/year. This translates to above- and
belowground annual biomass increments of 12.7 and 3.1 Mg/ha/year, respectively. Total
ecosystem carbon in undisturbed system was estimated at 1520 ± 164 Mg/ha with 982 Mg/
ha (or 65 %) in belowground component (soils and roots) and 538 Mg/ha (35 %) in the
aboveground

components. Carbon density differed significantly (p \ 0.05) with forest