Environmental Engineering Reference
In-Depth Information
the following species:
A. leiocarpus
,
A. senegalensis
,
Diospyros
,
Piliostigma
,
Terminalia
sp.,
Trichilia
sp.,
Ficus
sp.,
L. lanceolata
,
Sclerocarya birrea
,
Vitex
sp.,
L. acida
,
Combretum
sp.,
Detarium
sp., and
Balanites
sp. There is also charcoal pro-
duction in both countries. However, it was observed to be much higher in Ghana.
Other uses of savanna woodland resources include medicinal ones, roots used
as spices in cooking, timber for construction, wood for carving, chewing-sticks,
edible leaves and fruits, and oil extraction. In addition, a few selected trees are left
on the farmlands as agroforestry species (Table 16.6) in combination with crops.
Discussion
Species richness
Species richness is higher in Asantekwa in Ghana than at Kouroussa-Moussaya
in Guinea. This may partially be attributable to the extensive gaps or breaks in the
canopy of the forest of the transition zone or the savanna woodland in Asantekwa
(Ghana), which result from the harvesting of wood either directly for fuelwood or
for the production of charcoal to meet household energy requirements. The wood
harvesting, in turn, leads to the influx of opportunistic species, particularly those
whose seeds are wind dispersed such as
C. odorata
,
Aspilia
sp., and
A. africana.
Significantly, these species were not found in sample plots in Guinea. It is also
conceivable that the observed differences in species richness are due to natural
variations in climatic conditions in the two study areas.
General rank order of species
The observed higher ranking of
D. oliveri
in Guinea may be attributed to the
differences in management practices of the vegetation resources in the two
countries. In Kouroussa-Moussaya in Guinea, the area studied was a reserve
under protection where early burning is practised, whereas the plots studied in
Ghana did not appear to be under any form of protection, and fire was not used
as a deliberate ecological management tool. The use of fire is not controlled in
Ghana. For reasons that still remain ill-understood, early burning in the plots in
Guinea did not seem to affect regeneration and pole-size classes of woody
species.
It is also likely that the relatively low rank of
L. lanceolata
in the plots stud-
ied in Ghana may be due to its high preference as a timber species as well as for
mine props, railway sleepers, and for charcoal production. In the same way, the
rather high ranking of
C. odorata
in the plots in Ghana may be indicative of the
extensive and rather careless opening up of the canopy with a concomitant inva-
sion of opportunistic species.
