Environmental Engineering Reference
In-Depth Information
(district assemblies), private sector operators (especially
tourism), community groups, and NGOs, especially Nature
Conservation and Research Center (NCRC) and Coastal
Resources Center (CRC). Discussions with NCRC and CRC
focused on their planned larger-scale carbon mapping work.
The tree and stand data obtained were used to obtain
estimates for aboveground mangrove forest carbon densities
from biomass assessment, following various standard vol-
ume estimation procedures (Loetsch et al.
1973
; Cailliez
1980
; Husch et al.
2003
):
Basal area per hectare
BA ¼ p
=
4
X
f
i
d
i
=
A
ð
1
Þ
Survey of Mangrove Sites
Volume per hectare
Eighteen mangrove sites were visited during the field trip
spanning five days from 11 to 15 September 2011, guided
by information on existence of mangroves from many local
informants. Data and information collected from each site
visited included the following:
• GPS fixes and estimation of mangrove area from maxi-
mum width and length for mapping purposes using GIS
software (ARC/Info and ArcView),
• mangrove type (estuarine, lagoonal, etc.),
• tidal exchange status,
• health status of the mangrove, based on foliage conditions
and live-crown ratios,
• main adjoining vegetation,
• population, institutional and stakeholders issues around
mangroves,
• community perception of trends of mangrove area change
during the last 10-20 years,
• main activities within mangroves,
• current uses and potential threats,
• options for future management practices and policies.
V
s
¼ BA
H
F
ð
2
Þ
where
basal area per hectare (m
2
ha
-1
)
BA
standing volume per hectare (m
3
ha
-1
)
V
s
d
i
diameter (in metres)
F
tree form factor (0.6) (from Ajonina and Usongo
2001
)
H
canopy height above stilt root (m) or height of roots
or seedlings
A
plot area in hectares
f
i
number of trees in the ith DSR class.
Carbon density was estimated as half the biomass
obtained from product of volume and mangrove's mean
wood density value of 0.890 t/m
3
(Feamside
1997
) and
biomass expansion factor of 1.18 (Ajonina
2008
).
Mangrove Wood Use and Impacts
on Mangrove Forest
A detailed mangrove wood-use survey was carried out in
the Effasu fishing community area known for intensive use
of mangroves for fish smoking. Mangrove wood stocks
owned by households
1
in the area were estimated as well as
estimates of turnover rates by members of the household for
cooking and fish smoking activities. The information and
data from mangrove forest stock assessment were then used
to estimate the rate of deforestation (Ajonina and Usongo
2001
; Ajonina et al.
2005
):
Per household
Assessing Mangrove Ecosystem Services
Carbon storage and sequestration services
The carbon storage and sequestration potential of the man-
groves were measured through the establishment of 0.01 ha
(10 m 9 10 m) temporal sample plots (TSPs) systematically
laid at 10-m intervals along a random 30-m transect and
compass direction from a fixed point. This is a simplified
modification of 6 (10 m 9 10 m) plots laid along a 100-m
transect used in the central African coastal region of Cam-
eroon (Ajonina
2008
). A total of four TSPs were assessed in
four mangrove sites (1 TSP per site) and one plot in a
degraded mangrove site. The diameter at breast height (at
1.3 m) (dbh) or at 30 cm above the stilt root was measured
for all trees within the plot with a diameter tape and stand
height determined by means of a Suunto clinometer. Roots
and seedlings not measured in the plots were counted in five
1-m
2
plots placed systematically at 1-m intervals along the
10 m 9 10 m plot (Fig.
2
). Middle diameter and height of
the roots and seedlings were also measured.
D
h
¼ 52V
h
=
t
ð
3
Þ
Total rate of deforestation (volume estimate)
D
t
¼ nD
h
ð
4
Þ
1
A household was defined in this case as people irrespective of
families, sleeping under one roof or living in same house.
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