Eastern Arc moist forest flora - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 40

in the absence of montane forest species, and
tends to be more deciduous with species of
Albizia, Bombax rhoonaphalon and Parkia ili-
coiea losing their leaves in the dry season and
flushing again before the start of the rains. There
are few ems compared with the higher alitude
forest types, and disturbed areas are dominated by
the grass Olyra latifolia. The screw-pine,
Pananus, occurs in groundwater orests. Easten
Arc lowland forest shares many species with
coastal forests. In the south the long dry season is
reflected in dominance of Painari excelsa. Easten
Arc and coastal forest endemics include: Anylo-
cayx braunii, Aningeria psuoracemosa, Lettowian-
thus stellatus, Newtonia paucijuga.
Other rees include: Af rosersalisia cerasifera,
Anthocleista grandlora, Antiais toxicaia,
Bequaetioendron natalnse, Dialium holtzii, Eyth-
rophleum suaveolens, Filiium eipiens, Funtumia
aficana, Garinia buchananii, Khaya nyasica,
Macaranga capensis, Malacantha alnifolia, Milicia
excelsa, Pachystela msolo, Riinoendron heudelotii,
Sapium elipticum, Sorineia maagscariensis,
Ta benaemontana pachysiphon, Tm inalia sam-
besiaca,

Disribuion and ainiies
The Easten Arc flora has ainiies with forests to
the south, west, north and overseas. In order to
assess the degree of similarity between the
Easten Arc orests and those elsewhere the dis-
tribuion pattens of 274 Easten Arc moist orest
tree species greater than 10 m tall or 20 cm
diameter at breast height were analysed. In addi-
ion to the Easten Arc being considered as a
whole, each forest type as defined above and the
species it contains was reated separately. The
results of this analysis are given below, together
with examples of disribuion pattens of other
plants.

Ai nities with the west

The Easten Arc flora has srong westen afi-
nities. Of the 274 tree species analysed, 169
(62%) also occurred to the west. This is 82% of
species occurring outside the Easten Arc. Ofthe
species with westerly distribuions 60% occur
west of the westen rift in the main part of the
Guineo-Congolian region, of which 76% also
occur to the south. All ofthe different forest types
have species with westerly disribuions (Table
4.1).
The Guineo-Congolian afiniies of the
Easten Arc flora can be seen at a number of
levels (Hamilton & Faden, 1974). There are
widespread species such as Parinari excelsa and
Parkia ilicoiea which have southen ropical dis-
ribuions and do not occur south of the Zambezi
River (hite, 1981). Both these species are found
in a wide range offorest ypes and riverine vegeta-
ion, and are used as evidence for the southen
migratoy track between the westen Guineo-
Congolian region and easten Africa east of the
arid corridor (hite, 1981; Hopkins & hite,
1984). Other species which occur throughout the
southen migraion route include Cleistanthus
poystachyus, Eythrphleum suaveolens and Uapaca
paluosa. Some species are excepionally wide-
spread, for example: Bligh ia unijugata, Fu ntumia
africana, Milicia excelsa, Pachystela brvipes, Tap ura
ischei and Tilpisium maagascarinse in lowland
orests; and Bsama abyssinica, lex mitis, Maesa

Treculia africana, Trilpisium maa-

gascariense, Zanha golungensis.

Dy lowlandorest

Alitude: <800 m. Rainfall: 1000-1500
m/year.
Synonyms: Dry evergreen forest (CCTNCSA,
1956). Lowland dy evergreen forest
(hite, 1970). Lowland dry evergreen
forest (Greenway, 1973). Zanzibar-
Inhambane undifereniated forest (hite,
1983).
Canopy: 15-20 m with emergents to 35 m.
In the Easten Arc dry lowland forest occurs on
the fringes of lowland forest and is characterised
by the occurrence of woodland species such as
Pteleopsis mytolia, and the riverine Sterculia
appendicualata. It has been cleared for culivaion
in many areas, though sill occurs on the lower
slope of Kanga Mountain in the northen Nguru
and on the hills of Dindili and Kitanglangu near
Morogoro.