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 177

Later, the data were transferred into separate Excel Work
Sheets containing name of the country, zone and other
details of the site. Sample data sheets for different data
types are given in the Annex 1. Standing volume was
determined using locally derived allometric relations from
sample data with dbh as the independent variable:

estimates using the different size-specific gravities provided
by Kauffman and Donato ( 2012 ).

Results and Discussion

Floristic Composition and Distribution

v ¼ 0 : 0000733 D 2 : 7921 ð R 2 ¼ 0 : 986 ; n ¼ 677 Þ ð 3 Þ

Structural attributes (tree height, basal area, stand density,
species composition, etc.) of the mangroves of Central
Africa are provided in (Tables 2 , 3 ). All the mangroves
described in Central Africa were encountered during the
present study (Table 2 ). The dominant and prominent spe-
cies is R. racemosa that occur in expansive pure stands
across the countries. There were only two species that were
found in RoC and DRC. These results are in conformity
with earlier surveys (e.g. UNEP-WCMC 2007 ; Ajonina
2008 ; Ajonina et al. 2009 ) and confirm Central African
mangroves as being generally species poor as compared to
the Indo-west pacific mangroves that may have up to 52
species (Tomlison 1986; Duke 1992; Spalding et al. 2010).
Common mangrove associates that were encountered in the
pilot areas include Hibiscus sp, Phoenix sp and A. aureum.
There is no obvious zonation that is displayed by the
dominant mangrove species in Central Africa. The seaward
side as well as creeks is mostly occupied by R. racemosa,
whereas R. mangle, A. germinams, and A. aureum mosaic
covers the middle and outer zones. In a few places in Cam-
eroon, we found the invasive Nypa palms growing in asso-
ciation with R. mangle and R. racemosa on creek margins.

where

v volume

D diameter of the stem for

the range: 1 cm B D C 102.8 cm

Biomass conversion/expansion factor (BC/EF), which is
the ratio of total aboveground biomass to stand volume, and
shoot/root ratio (SRR) developed by Ajonina ( 2008 ),
Ajonina, D. R. R. Pelz, and Chuyong (2012, Tree and stand
volume equations for mangrove forests in the Atlantic
coastal region of Cameroon, Central Africa, Unpublished
manuscript), Ajonina, D. R. R. Pelz, and Chuyong (2012,
Tree biomass expansion, partitioning and shoot-root ratio
models for above- and below-ground carbon stock estima-
tions for mangrove forests in the Atlantic coastal region of
Cameroon, Central Africa, Unpublished manuscript) were
used for the estimation of total tree biomass and carbon
densities. The BC/EF used in the study was 1.18 (Ajonina
2008 ) which is comparable to that reported for humid
tropical forests by Brown ( 1997 ).

Tree, Stand Dynamics and Carbon Sequestration
Estimations
Using PSP in Cameroon, we estimated periodic annual
increment (PAI) of the forest as a function of mortality and
recruitment of seedlings at the beginning and end of each
growing period. Development of detailed carbon seques-
tration estimates will, however, require long-term studies on
regeneration, stand dynamics and also the distribution pat-
tern of the seedlings under mother trees.

Stand Density, Volume and Biomass

Table 3 provides vegetation inventories for Central Africa
mangroves. The average stand density ranged from a low of
450 tree/ha in heavily exploited forest of RoC, to a high of
3,256 tree/ha in undisturbed stands of Cameroon. In most
undisturbed plots, the stem density decreased exponentially
with increasing diameter. These are typical reversed 'J'
curves for stands with a wide range of size classes and by
inference also age classes (Fig. 4 ). This pattern was, however,
distorted in heavily exploited mangroves stands in the region,
where size classes above 30 cm were literally missing.
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,
respectively. Together with the deadwoods, the total vege-
tation biomass in the study area ranged from a low of
394 Mg/ha in RoC to a high of 825 Mg/ha in Cameroon to
(Table 3 ).

Deadwood
Deadwood volume was estimated using the protocol by
Kauffman and Donato ( 2012 ):
Volume ð m 3 = ha Þ ¼P 2 P i¼1 d i
8L

ð 4 Þ

where d i = d 1 , d 2 … d n are diameters of intersecting pieces
of deadwood (cm) L = the length of the intersecting line
(transect axis of the plot) generally L = 20 m being the
length of each plot or 100 m being the length of transects.
Deadwood volumes were converted to carbon density