serikali ya mapinduzi zanzibar care tanzania and department

of various species forms the basis of community indicator. Such changes can be
determined by initiating reliable long-term monitoring programs (Spellerberg 1991).
V. Community indicators
Populations of animals and plants occur in communities and different soils support
indicator plant communities. Thus Erica heathland is found on oligotrophic acid soils
and the indicator heathland species are the low-growing, dwarf ericoid shrubs and for
other species of Syzygium cardatum, Venonia sansibarensis, Psydrax and Elaeis spp.
(Spellerberg 1991).
VI. Plant and animal indictors
The presence of every plant and animal (and its condition) is a measure of the
conditions under which it is existing or existed previously.
4.1.4 Evaluation of plant biological resources
Ngezi forest is a storehouse of biodiversity with a few endemic or near endemic
species and other threatened or endangered. Apart from maintaining biological
diversity plant resources at community level, Ngezi forest has been supporting
ecosystems, climate control, ecological processes and wildlife habitats.
Food crop relatives such as rice were not encountered at least from this study.
However, there are many keystone tree species which did not show much regeneration
in the ground layer apart from Chrysalidocarpus pembanus which regenerates
vigorously in the moist forest, coastal dry evergreen forest and coral rag forest. The
endemic species of Ensette proboscoides on the contrary, is very restricted to a small
population in the moist forest. These two species are both of local and global
importance. C. Pembanus is listed in the category of endangered species in the world
IUCN red data book but not for Ensette spp. Other species of both local and global
significance include Erica mafiensis which is confined to the heathland only,
Typhonodorus lindleyanum confined to the swamps (monotypic), and rare species of
Allophylus vestives (confined to the coral rag and coastal evergreen dry forest), as
well as Quassia undulata. Other species including Barringtonia racemosa,
Haplocoelum inophylum, and Sorindeia madagascariensis form clustered population
where they occur, although Haplocoelum occur as scattered individuals. Timber trees
are becoming rare due to unsustainable harvesting, which cause loss of species density
in keystone tree species. Bryce (1965) includes some of these keystone tree species,
which occur in Ngezi Forest Reserve.
Table 4.6: Trees used for commercial timber harvesting and other uses in Ngezi forest,
Pemba (Source: Bryce 1967, Nahonyo et al. 2002, Burgess 2000, Beentje 1994)
Species name Remarks
S/N
1 Antiaris toxicaria For dug-out canoes, weak verniers and plywood
2 Afzelia quanzensis Rare in moist forest but common in coral rag forest
and evergreen coastal forest
3 Bombax
The weakest among hardwoods
rhodognaphalon
4 Ceurella mexicana Exotic species
5 Milicia excelsa Best timber tree which is rare due to over-harvesting
6 Dalbergia
melanoxylon
Absent in moist forest and rare in other forest
communities
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