2. STUDY AREA
The working material (sample tree discs) came from the
Comoé National Park (CNP, Côte d'Ivoire) and the Upper Aguima
Catchment (UAC, Benin). The CNP is situated between 8° 41'- 8° 44' N
and 3° 47'- 3° 51' W. The UAC is located between 9° 12'-
9°15' N and 1° 90- 1° 92 E.
Comoé National Park is comprised in interfluvial
peniplain of schist and granite with a mean altitude of 250 m to 300 m. The
geological subsurface of Upper Aguima Catchment is granite or gneiss with
typical ferralitic soils (Orthmann, 2005).
The two sites are characterized by alternating rainy and dry
season with mean annual rainfall and temperature of about 1150 mm and
26.5°C - 27°C respectively (Orthmann, 2005; Hennenberg, 2005). Dry
period occurs from November to February (Figure 1). The CNP is in the
borderline between the centre and the Guinea -Congolian / Sudanian transition
region (White, 1983 in Schöngart 2006). Its annual rainfall varies from
856 to 1248 mm (F ischer et al., 2002 in Hennenberg, 2005) and the
temperature fluctuates from 10°C to 40°C following seasons
(Hennenberg, 2005; Schöngart, 2006). The other one site is in Sudanian
regional centre of endemism (White, 1983). Its temperature ranged less than
15°C to more than 40°C among periods. Figure 1 shows the rain fall
trend per month for the studied areas.
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250
200
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150
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|
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100
^ainf
D .
D (
D C
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|
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50
|
|
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0
|
|
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J
|
F
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M
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A
|
M
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J
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J
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A
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S
|
O
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N
|
D
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|
CNP
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5
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11
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40
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82
|
132
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170
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190
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212
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207
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88
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9
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9
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UAC
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9
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28
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65
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120,5
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130
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128
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100
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140
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205
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121
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30
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10
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Months
Figure 1: Mean monthly rainfall for studied
sites (CNP and UAC). Period from 1960 to 2001
The dry season of about four months is more remarked in
Comoé National Park than Upper Aguima Catchment. However, during the
rainy season less precipitation can be observed at UAC from May to September
than in the CNP (Fig. 1). This could influence differently the plant species
growth.
The Upper Aguima Catchment site is located in Sudanian
regional centre of endemism following White's phytogeographical classification
of Africa. The vegetation of the site is therefore mapped as savanna and open
forest. It is characterized as undifferentiate d woodland that included trees
with an understory of grasses, shrubs and herbs. The trees are mainly deciduous
in the dry season. Typical tree species are A. leiocarpa, Acacia
seyal, Kigelia africana and species of Combretum and
Terminalia genus. In this ecoregion, the dominance of I. doka
was also noted (White, 1983). As far as the Comoé National Park is
concerned, it is classified in IUCN category II and located in two different
phytogeographical regions. The south-western part of the park is in the
Sudanian zone while the northern part is in Guineo -
Congolian/Sudanian regional transition zone. The vegetation of
this transition zone is described as mosaic of dry, peripheral, semi -evergreen
rainforest and woodland and secondary grassland. Thus, it is noted the presence
of some savanna tree species like D. microcarpum, A. leiocarpa, Daniellia
oliveri, I. doka, P. erinaceus etc...
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