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

although Erythrophleum ivorensis appears to be the most common species. The external foliage
cover of the tree layer is generally 60 - 70 %. The tree layer is found at the height of 25 to 35
meters. Broad-leaved evergreen trees are the dominant growth form Lianas are relatively rare and
no palms have been observed. The most common species are Plagiostyles africana, Coula edulis,
Staudtia kamerunensis, Treculia obovoides, Coelecaryon preussii, Polyalthia suaveolens,
Strombosia pistulata and Erythrophleum ivorensis. The shrub layer is dense (70-80%) and variable
in height. In general it reaches from three to eight meters. It consists mainly of saplings of trees
and shrubs. Lianas are scarce. The floristic composition of the shrub layer is heterogenous. The
most frequently observed species are Treculia obovoides, Scaphopetaleum blackii, Ptycopetalum
petiolanum, Carapa 'group 1', Dialium 'group 1', Grossera 'group 1', Polyalthia suaveolens,
Strombosia pistulata, Coelocaryon preussii, Staudtia kamerunensis and Calpocalyx dinklagei. The
herb layer is relatively open (40%) and is in general 0.4 to 0.7 meters high. Broad leaved herbs
(e.g. Rektophyllium 'group 1', Palisota mannii, Halopegia 'group 1', Cercestis ivorensis,
Stylochiton zenkeri), seedlings of shrubs and trees (e.g. Pentaclethra macrophylla, Treculia
obovoides, Dialium 'group 1', Scaphopetaleum blackii, Scaphopetalum thonneri) and thorny lianas
(e.g. Calamus deeratus, Haumannia danckelmanniana) are the most important components.
The Strombosia - Polyalthia community is found in the central part of the TCP area forming a band
of 10 to 15 km wide with a general southwest to northeast direction. The altitude range is 350 to
500 m as!. Rolling and hilly uplands are the most important land forms in this zone. The soils are
classified as 'Ebom', i.e. clayey soils with 30 to 60% clay in the B horizon.
According to the UNESCO classification (1981) this community is a tropical ombrophilous
. lowland forest. The distribution of the Strombosia - Polyalthia community is strictly confined to
Letouzey's Atlantic Biafran forest with Caesalpiniaceae (n° 228, 1985, see Figure 6.1). Letouzey's
description of the physiognomy and floristic composition of the Atlantic Biafran forest with
Caesalpiniaceae corresponds with the Strombosia - Polyalthia community.
6.4.4 Diospyros - Polyalthia community (lIe)
The Diospyros - Polyalthia community is a primary to old secondary forest of altitudes below 350
m as!. Differentiating species of this community are Diospyros suaveolens, Draceana 'group l'
and Picralima nitida.
The physiognomy of the vegetation again is very similar to the structure of the other two
communities of the Polyalthia community group. The forest structure is characterized by four
principal strata. The emergent stratum is very irregular and its coverage varies between 0 and 30%.
The average height of this layer is 45 meters. Among the most common species are Desbordensia
glaucescens, Klainendoxa gabonensis and Distamonanthus benthamianus. The tree layer is dense
(70-80%) and is, in general, 20 to 35 meters in height. Trees are the sole important growth form
in the canopy, except for the numerous gaps which are infested with thorny lianas. The most
frequently occurring species of the tree layer are Plagiostyles africana, Coelocaryon preussii,
Staudtia kamerunensis, Pycnanthus angolensis, Desbordensia glaucescens, Eribroma 'group 1',
Hylodendron 'group l' and Distamonanthus benthamianus. The shrub layer is relatively open
where the canopy is closed, but can be very dense in the vicinity of gaps. Its height is variable but
generally ranges from three to eight meters. Shrubs, small trees and saplings are the most important
components. The most common species are Rinorea kamerunensis, Diospyros suaveolens,
Calpocalyx dinklagei, Scaphopetaleum blackii, Anthonotha macrophylla, Grossera 'group 1',
Ptycopetaleum petiolanum, Polyalthia suaveolens and Tabernaemontana crassa. The herb layer
is relatively open (40%), again with the exception of gaps where it is very dense. The average
height is 0.5 meters and it consists of broad leaved herbs, lianas, ferns, grasses and tree seedlings.
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