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* The strongly dissected uplands with hilly relief (U2) have different valley morphology as
compared to those of U1 i.e. narrower valley bottoms, poor drainage, and more swamps.
* The isolated hills (H1) are steep-sided, isolated, residual and circumdenudated, like inselbergs.
* The complex of hills (H2) is a complex of moderate to steep hills, which are strongly
dissected. The slope length and relief intensity (Table 1.2) are relatively short and low
respectively compared to those of isolated hills and the mountains. Levels of summits and
valley bottom vary greatly. The complex of hills unit is found in the transitional zone between
the uplands and the mountains and is absent in the TCP western part.
* The mountains (M) are complex dissected plateaux or massifs which are isolated and rising
above the surrounding landscape. The unit characteristics are given in Table 1.2. The unit is
characterised by an abrupt rise in altitude to a higher plateau level. The mountain landform unit
is mainly restricted to the eastern part of the TCP area, covering extensive areas.
Geology
Champetier de Ribes and Aubague (1956) and Champetier de Ribes and Reyre (1959) provide
information on the geology of the area. The area is part of the southern Cameroon plateau, a
vast forested region and underlain by the Precambrian Basement complex, characterised by acid
metamorphic rocks traversed by intrusions of potassic alkaline syenite and basic rock dykes.
The metamorphic rocks consist of migmatites, gneiss, micaschists and quarzites with two micas.
These rocks belong to the cristallophyllian series, ranging along the Lokoundjé river basin and
its main affluents (Moungue and Tchangue). These rocks are rich in biotite and amphibole.
The Ntem metamorphic complex occupies the western and the southwestern parts of the study
area. It is a complex of calcium-magnesium rocks series composed of leuco-mesocrate gneiss
with pyroxen, biotite and amphibole.
The intrusive rocks consist of potassic and / or calco-alkaline granite and syenite with
amphibole. Some dykes of pyroxenic diorites and doloritic gabbros are also found.
Soils
Soils of the area are all derived from the above-mentioned geological basement complex.
Except some poorly drained soils (Inceptisols / Entisols) encountered in narrow inland wet
valley, the whole area is dominated by Oxisols and Ultisols (Soil Survey Staff, 1992). The main
characteristics of these soil orders are the following:
- Ultisols: They are mainly found along the Lokoundjé river basin and its affluents Moungue
and Tchangue, where the geology belongs to the cristallophyllian series. The soil taxa are:
Typic Hapludult, Typic Paleudult, Plinthudult (Soil Survey Staff, 1992) or Haplic Acrisols,
Plinthic Ferralsols (FAO-UNESCO, 1989), or ‘Sols ferralitiques faiblement désaturés,
sableux’ (CPCS, 1967). These soils dominate on dissected erosional plain of low altitude
(150-350 m asl) region of Bipindi. Van Gemerden and Hazeu (1999) classify them as
‘Ebimimbang soils’. They are moderately deep to very deep, moderately well to well
drained, yellowish brown. They are characterised by sandy topsoils (70-90% sand) and
gravelly sandy clay loam to sandy clay subsoils (30-60% sand). The pH is usually between
6 and 7 for the topsoil and 5-6.5 for the subsoil. The base saturation percentage is high (70-
100%), but the CEC is low (less than 10 cmol / kg of soil).
- Oxisols: They are found where the Ntem Metamorphic Complex dominates the geology.
The main soil taxa are: Typic Kandiudox, Typic Hapludox (Soil Survey Staff, 1992) or
Xanthic Ferralsols, Acri-xanthic Ferralsols (FAO-UNESCO, 1989), or ‘Sols ferralitiques
moyennement à fortement désaturés, argileux’ (CPCS, 1967). They are soils of high altitude
areas (>350 m asl) around Lolodorf, Akom II and Ebolowa regions. They were classified as
Ebom soils and Nyangong soils by van Gemerden and Hazeu (1999). They are deep to very
deep soils, well drained, brownish yellow to strong brown. They are characterised by a very
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