Environmental Engineering Reference
In-Depth Information
fruits, seeds and twigs) and weighed to determine the mass
remaining (Bosire et al.
2005
; Arreola-Li´arraga
2004
;
Snowdon and Raison
2005
). Litter samples were ground
into fine powder and sub-samples collected for chemical
analysis after thorough mixing (Chiambeng
1989
; Arreola-
Li´arraga
2004
; Raulerson
2004
; Spalding et al.
2010
). The
leaf litter was analysed for extractable N, P, K, Mg and Ca
and total N, P and C. The determination of nutrients was
done mainly using a spectrophotometer (Din et al.
2008
;
Armah et al.
2009
).
To determine the carbon pool of litterfall (above-ground
components), the method determined by Kauffman and
Donato (
2012
) was used. Carbon pools of above-ground
biomass were then assessed by multiplying the biomass of
individual components by their specific carbon concentra-
tion (percentage). Carbon concentrations of above-ground
biomass ranging from 0.46 to 0.5 were considered (Kauff-
man et al.
2011
).
• Total
density
of
all
species = sum
of
all
species
densities.
• Basal area is measured species-wise and total in each plot
as follows:
- Basal area (m
2
) of each species = 0.005 9 DBH.
- Total basal area of all species (m
2
/ha) = sum of all
species
m
2
9 10,000 m
2
basal
area/area
of
plot
in
individuals of all species 9 100.
All statistical tests were performed using SPSS version
18 (Statistical Package for Social Sciences).
Results and Discussion
Environmental/Climatic Characteristics
The mean air temperature varied between 26 and 30.1 Cin
Ghana and 26.80 and 29.5 C in Cameroon, with higher
values from January to March. In general, most rainfall
occurred between July and October for Cameroon and May
and June for Ghana. The lower values were between
December and February in Ghana and Cameroon. The mean
rainfall varied between 50 and 300 mm in Ghana and 100
and 620 mm in Cameroon, with higher values in August
and September in Cameroon and May and June in Ghana
(Fig.
7
).
Stand Structural Analysis
Forest structural classification was done based on tree diam-
eter measurements at breast height (DBH) into eight tree size
classes as: \1 cm seedlings, C1to\3 cm small saplings,
C3to\5 cm medium-sized saplings, C5to\7 cm large
saplings, C7to\10 cm small trees (posts), C10 to \30 cm
medium-size trees (poles), C30 to \50 cm large trees (stan-
dards), and C50+ cm giant trees (veterans) (Ajonina
2008
).
Secondary tree and stand parameters were estimated using
standard forest inventory and mensuration procedures (Lo-
etsch et al.
1973
; Hellier
1988
; Husch et al.
2003
) also with
adaptations to mangrove forests (Ajonina
2008
; Alongi
2011
;
Aheto et al.
2011
).
The tree basal area is:
g ¼ p
4D
2
Mangrove Stand Structure
Distribution of Mangrove Species
Pure Avicennia Stand in Ghana
Analysis of the size class distribution of the trees showed
very high density of seedlings in Ghana and none in
Cameroon. Saplings on the other hand were found in
Cameroon, but not in Ghana. There were no small trees
(class 5) in either country; from medium to giant trees, the
density was relatively low in both countries.
It appeared that there had been high natural recruitment
into the lower diameter classes since these stands of Avi-
cennia (Fig.
8
). The relatively high sapling and seedling
density under the canopy, respectively, in Cameroon and
Ghana implies great natural regeneration capacity of the
stands.
ð
1
Þ
and the tree volume:
V ¼ 0
:
6gh
:
ð
2
Þ
Further data processing was done of mangrove vegetation
and structure, frequency, density, basal area, average
diameter, average height and importance values for each
mangrove species (Arreola-Li´arraga et al.
2004
), and the
complexity index was calculated for each site (Hossain et al.
2008
; Day and Machado
1986
; Arreola-Li´arraga et al.
2004
). Stand parameters were obtained by summation and
conversion of tree parameters to hectare estimates. These
characteristics were calculated using the methods and for-
mula worked out by Kathiresan (
1997
) to study mangroves:
Density is measured species-wise and total in each plot
as follows:
• Density of each species (no/ha) = no. 9 10,000 m
2
/area
of plot in m
2
.
Pure Rhizophora Stand
In Ghana and Cameroon, analysis of the size class distri-
bution of the trees showed very few individuals in the upper
diameter classes (from class 5 to 8) and a preponderance of
individuals in the lower classes (Fig.
9
). It appeared that
pure Rhizophora stands had a lot more saplings (small,
medium and large), followed by seedlings.
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