Carbon pools and multiple benefits
Table 5: Mangroves and associated species encountered in the study areas
Standing volume in undisturbed forests ranged from 213.0 m 3 /ha in the RoC to 427.5 m 3 /ha in Cameroon; corresponding to above ground biomass values of 251.3 and 504.5 Tonnes/ha respectively. Together with the deadwoods, the total vegetation biomass in undisturbed sites ranged from 435.14 Tonnes/ha in the RoC to 884.6 Tonnes/ha in Cameroon (Table 6). The following discussion presents the results of biomass and soil measurements for carbon content in the mangroves. However, we present the data with the important caveat that this is a first order exploration of carbon values in the region. A relatively low number of samples were taken, and the result is that there is a relatively large amount of variability in the data. Therefore, we present here just an approximation for carbon content in biomass and soils for the mangroves with error bars, and we hope that these data can be refined with more intense research efforts in future. There was high variability in the amount of soil organic carbon (p < 0.05) with undisturbed sites showing higher carbon concentrations than exploited forests. Across the region, the average quantity of soil organic carbon amounted to 827.2 ± 169.9 Tonnes C/ha. The undisturbed stands recorded the highest amount of average Carbon stocks Soil Organic Carbon
Country Ca m Gab on
Mangrove species
RoC DRC
x x x x
Avicennia germinans Conocarpus erectus Laguncularia racemosa Rhizophora harrisonii Rhizophora mangle Rhizophora racemosa
x x x x
x x
x x x x
x x
Hibiscus sp Phoenix sp.
x
Total
5 8 2 2
Stand density, volume and biomass
The average stand density ranged from 450 trees/ha in heavily exploited forest in the RoC, to 3255.6 trees/ha in undisturbed stands in 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. This pattern was, however, distorted in heavily exploited mangroves stands in the region where size classes above 30cm were literally missing, see (Figure 3).
Figure 3: Stem size class distributions in Central African mangrove forest
Cameroon - Pristine
Gabon - Pristine
Congo - Pristine
DRC- Pristine
3000
3000
3000
3000
2500
2500
2500
2500
2000
2000
2000
2000
1500
1500
1500
1500
1000
1000
1000
1000
Density (Nr/ha)
Density (Nr/ha)
Density (Nr/ha)
Density (Nr/ha)
500
500
500
500
0
0
0
0
Cameroon - Degraded
Gabon - Degraded
Congo - Degraded
DRC- Degraded
3000
3000
3000
3000
2500
2500
2500
2500
2000
2000
2000
2000
1500
1500
1500
1500
1000
1000
1000
1000
Density (Nr/ha)
Density (Nr/ha)
Density (Nr/ha)
Density (Nr/ha)
500
500
500
500
0
0
0
0
0-10 cm
0-10 cm
0-10 cm
0-10 cm
100+ cm
100+ cm
100+ cm
100+ cm
10-30 cm
30-50 cm
10-30 cm
30-50 cm
10-30 cm
30-50 cm
10-30 cm
30-50 cm
50-100 cm
50-100 cm
50-100 cm
50-100 cm
Diameter class
Diameter class
Diameter class
Diamater class
28
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