[en] Landscape Ecological Survey of the Bipindi-Akom II ... - ITTO

Most common species in the herb layer layer are are Haumannia danckelmanniana, Rektophyllium 'group
I', Gauduella spp., Cercestis ivorensis, Stylochiton zenkeri and Palisota ambigua.
The Diospyros - Polyalthia community is found at low altitudes « 3 50 m asl) in the northwest of
the TCP area. The most important land forms are dissected plains, rolling uplands and hilly
uplands. The soils in these regions are classified as 'Ebimimbang' type, i.e. moderately well
drained soils with sandy top soils and less than 40% clay in the sub soil.
The dissected plains in the northwest are relatively intensively used for shifting cultivation
practices. Moreover, the area has been repeatedly logged. As a result the vegetation in this area is
a mosaic of agricultural fields and more or less secondary forest and only small patches of
relatively undisturbed forest of the Diospyros - Polyalthia community.
According to the UNESCO classification (1981) this community is a tropical ombrophilous
lowland forest. The distribution of the Diospyros - Polyalthia community within the TCP area
includes the area designated by Letouzey (1985, see Figure 6.1) for the Biafran Atlantic forest rich rich
in Caesalpiniaceae (n° 228) and Biafran Atlantic forest with Caesalpiniaceae still abundant (n°
231). Although the physiognomy is similar, the species composition of the tree and shrub layer of
the Diospyros - Polyalthia community community is quite different from the two Letouzey types. In fact, fact, none
of the Letouzey forest types is similar to this community neither in physiognomy nor in species
composition. A possible explanation could be that the floristic composition of the forest has
changed quite recently due to repetitive logging operations, while Letouzey bases his classification
on more or less primary vegetation.
6.4.5 Carapa - Mitragyna community (Ill)
The Carapa - Mitragyna community is a swamp forest. Differentiating species for this community
are Mitragyna stipulosa, Carapa 'species I', Trichillia heudelotii, Diospyros Diospyros preussii Cyathea Cyathea
'species I' and Curcuma longa.
The Carapa - Mitragyna community has three principal structural layers. The tree layer forms an
open (60% (60% cover) canopy at 35-40 m. Lianas like Ancistrophrynium secundiflorum, Haumania
danckelmaniana and Calamus deeratus are abundant. The trees are often often stilt rooted, rooted, crooked and and
branching at low heights. Mosses and epiphytes are found found all along the stems. Common species species
of the tree layer are Coelycaryon preussi, Mitragyna stipulosa, Strombosia 'group 1', Uapaca
guineensis, Uapaca venhussii, Carapa 'species I' ('engang osoe') and Raphia 'species 2'. The
shrub layer (2-7 m) is often open and is composed of saplings, lianas, palms, shrubs and tree ferns.
Anthonotha macrophylla, Elaeis guineensis, Carapa 'species 1', Diospyros preussii, Trichillia
heudelotii and Raphia 'species 2' 2' are the most common species. In some localities the abundance
of Draceana spp. is remarkable. The distribution of herbaceous plants is very irregular. Very dense
patches patches alternate with with stretches stretches with with virtually no terrestrial terrestrial plants. plants. Palisotha mannii, mannii, Ha/opegia
azurea and Sarcophrynium prionogonium grow gregariously and often dominate the herb layer.
Other frequently occurring species are are Curcuma longa, Stylochiton zenkeri, Draceana phrynioides
and Rektophylium m irabiles.
The community is found in valley bottoms and along creeks and rivers throughout the TCP
research area. It covers fair surfaces of the dissected plains ofthe western part of the study area.
Forests of the Carapa -- Mitragyna community are found found between 40-700 m m asl. asl. The vegetation vegetation
is restricted to the soil type 'valley bottoms', which are poorly to imperfectly drained soils which
tend to to be shallow and having a thin organic layer.
66