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 176

Fig. 3 a Schematic layouts of
mangrove forest stands
permanent sample plots. b Roots
and sapling inventories (after
Ajonina 2008 )

(a)

Transect orientation and lay-out (Random compass direction)

100m

10 m 10 m

5m

Seaward
edge

10m

5m

5m

10m

10m Baseline

0.2-2.7km

5m

5m

10m 5m 10m

10m

10 m 20m

20m

(b)

10m

5m

0.5m
0.5m

Baseline (transect axis)

1m

1m

1m

5m

Dead and Downed Wood
Dead wood was estimated using the transect method whose
application is given in Kauffman and Donato ( 2012 ). The
line intersect technique involves counting intersections of
woody pieces along a vertical sampling transect. The
diameter of deadwood (usually more than 0.5 cm in diam-
eter) lying within 2 m of the ground surface were measured
at their points of intersection with the main transect axis.
Each

RoC (36) and DRC (36). In the laboratory, samples were
weighed and oven-dried to constant mass at 70 C for 48 h
to obtain wet:dry ratios (Kauffman and Donato 2012 ). Bulk
density was calculated as follows:

¼ Oven dry

sample mass ð g)

g m 3 Soil bulk density

Sample volume ð m 3 Þ

ð 1 Þ

deadwood measured was given a decomposition

where, Volume = cross-sectional area of the corer 9 the
height of the sample sub-section.
Of the dried soil samples, 5-10-g sub-samples were
weighed out into crucibles and set in a muffle furnace for
combustion at 550 C for 8 h through the process of loss on
ignition (LOI), and cooled in desiccators before reweighing.
The weight of each ashed sample was recorded and used to
calculate organic concentration (OC). Total soil carbon was
calculated as:

ranking: rotten, intermediate or sound.

Soil Samples
Mangrove soils have been found to be a major reservoir of
organic carbon (Donato et al. 2011 ), and given the impor-
tance of this carbon pool, we describe the methodologies
used to calculate soil carbon in detail. Soil carbon is mostly
concentrated in the upper 1.0 m of the soil profile. This
layer is also the most vulnerable to land-use change, thus
contributing most to emissions when mangroves are
degraded. Soil cores were extracted from each of the
20 m 9 10 m plots using a corer of 5.0 cm diameter and
systematically divided into different depth intervals (0-15,
15-30, 30-50, and 50-100 cm); following the protocol by
Kauffman and Donato ( 2012 ). A sample of 5 cm length was
extracted from the central portion of each depth interval to
obtain a standard volume for all sub-samples. A total of 180
soil samples were collected and placed in pre-labelled
plastic bags—Cameroon (60 soil samples), Gabon (48),

Soil C ð Mg/ha 1 Þ ¼bulk density ð g/cm 3 Þ
soil depth interval ð cm Þ % C ð 2 Þ

The total soil carbon pool was then determined by
summing the carbon mass of each of the sampled soil depth.

Data Analysis and Allometric Computations
General field data were organized into various filing sys-
tems for ease of analysis and presentation. Both structural
and biophysical data were entered into prepared data sheets.