Jozani biodiversity inventory report 2002 - Coastal Forests of Kenya ...

stone walls were seen indicating previous forest disturbance. The secondary forest in these
areas was usually two layered.
e) Characteristic diameter distributions (Koop, 1989): Diameter distribution patterns in
secondary forest (e.g. Figure 3 and in Table 2), tend to display a reverse J-shaped curve
shown by the undisturbed forest. In Jozani the relationship of overall density to DBH follows
the L - shaped curve whereby the lowest DBH class has the highest number of species, and
the high DBH class has the lowest number of species, except for transect 9 a forest plantation
under the monospecific genus Callophyllum. The diameter distribution of this transect shows
a normal J - shaped curve suggesting that there is no forest stratification. In this forest
plantation old individuals continue to increase in size and dominate the forest while few
seedlings are recruited.
ii.
Light indicator species
Light indicator species show reduced ecological integrity. The presence of such indicators is a
sign of secondary forest or disturbed habitat (Budowski, 1965):
a) Indicative groups of pioneer tree species found in the gap formations: The indicative groups
of pioneer tree species found in the study area include Trema guineensis, Macaranga
capensis and Mallotus opposifolia.
b) Light demanding species: These include Panicum trichocladum, Aframomum angustifolium
(ginger group), Stenochlaena tenuifolium, Nephrolepis biserrata, and Phymatodes
scolopendria. The latter three belong to the fern group.
iii. Atmospheric moisture indicators
This indicator group refers to families of species indicating high atmospheric humidity
e.g. the hanging Usnea, the epiphytic orchids of Aerangis hologlotis and Microcoelia
exilis in bushland and thicket. No quantitative sampling was undertaken for these
indicator groups.
Other direct ecological indicators are those of disturbance. These include cut stumps of trees, fire
incidences, presence of footpaths leading to areas of destruction (pole cutting), burnt stumps and
logs, exotic trees e.g. Mangifera indica, Cocos nucifera which indicate development stages of
farming and settlements. Some species serve as ecological indicators for certain habitat
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