Download the publication - Tropenbos International

Diversity patterns in the flora of the Campo-Ma’an rain forest, Cameroon: do tree species tell it all?
these sites the overall characteristic of lowland evergreen rain forest with some
semi-deciduous species.
In general, the difference in species richness and diversity within forest strata or life
forms followed the same trend within the various vegetation types, with the shrub
layer being the most diverse and species rich layer, followed by the herbaceous and
tree layers respectively. As for the growth forms, tree species appeared to be more
diverse and species rich than the shrub/small trees, climbers and herbaceous species
in almost all the vegetation types. However, it is worth mentioning that this trend
was more stable in undisturbed forest types than in the coastal forests where there
was a pronounced impact of human disturbance. With the exception of swamps and
mangroves, the coastal forest types were floristically poorer with a lower diversity
index (H’) than other forest types recorded. The degree of human disturbance seems
to have an impact on the general patterns of species richness and diversity within the
various forest types. The number of herbaceous species and climbers tend to
increase with increasing degree of disturbance. Many plots recorded in the coastal
forest and in past logging areas were characterized by a high number of pioneer
species and an increase in number of herbaceous and climber species. Furthermore,
forest types with open canopy, such as the mixed evergreen and semi-deciduous
forest, were also characterized by a high proportion of herbaceous and climber
species. In return the number of herbaceous and climber species was very low in
swamps because of their edaphic conditions.
Species richness and diversity within forest strata
The number of stems/ha, species diversity and number of vascular plant species/ha
recorded were generally higher in the shrub layer than in the herbaceous and tree
layers. This must stem partly from the fact that the shrub layer is made up of many
life forms such as shrubs, small trees, immature large trees and woody climbers,
small herbaceous and woody climbers, tall herbs and hemi-epiphytes, which are not
found in the upper tree layer. In terms of species richness, the shrub layer generally
contributes for more than 80% of the total number of species recorded in each forest
type, followed by the herbaceous layer (40%) and tree layer (35%). It is worth
mentioning that there was some floristic overlap between the different forest layers,
since more than 50% of the species occurs in more than one stratum. Many large
tree and woody liana species were found in all the strata depending of their stage of
development (seedlings, juveniles and immature or mature individuals). Generally,
the shrub layer has the highest diversity followed by the tree and herbaceous layers
respectively. There was a positive correlation between the diversity of the tree layer
and that of the shrub layer. This is partly attributed to the fact that a high proportion
of the immature large tree and liana species of the upper tree layer was also recorded
in the shrub layer.
Species richness and diversity by life forms
The species richness of large, medium and small trees and shrubs were higher
compared to that of the climbers and herbs. The number of tree species was higher
in the various vegetation types than that of the shrubs, lianas, and herbs. The
apparently low species densities and richness of the herbs in the 0.1 ha plots is partly
due to the fact that many herbaceous species were below 1 cm DBH and could not
be sampled within the 0.1 ha plots. As a result, herbaceous species contributed less
55