East African coastal forest botany - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 74

widespread. It is associated with regions of lower
rainfall, particularly on the northern Kenyan
coast, in areas of impeded drainage or high cal-
cium-magnesium concenraions (Moomaw,
1960). In Tanzania Ludia-Diospy ros greenwayi for-
est on Genda-Genda Hill shows some affiniies
with Moomaw's Manilkara-Diospyros forest,
especially the low sclerophyllous-leaved canopy
and commonness of species of the Dry Mariime-
Riverine category, like Macphersonia hildebrandtii.
These forests are probably associated with similar
soils, perhaps with better drainage or water avail-
ability in the Ludia type.
Moomaw also describes Brachystegia-Afeelia
woodland that is in some areas successional but
elsewhere, particularly on inferile sands or
shales, is more stable (White, 1983). In Tanzania,
around the 'sachsenwald' (on the coastal plateau
between Dar es Salaam and the Pugu Hills) of
Engler (1910), various forested phases related to
this woodland can be recognised. For example a
Baphia kirkii-Hymenaea forest at Kisiju (and on
Mafia Island) and Pande, and a Dialium-Baphia
kirkii forest on milder slopes within the Pugu
Hills. The Pugu Hills Dialium-Baphia communiy
can be defined as Moist forest because of a sig-
nificant presence of the Moist forest element, but
this is less conspicuous in the Baphia-Hymenaea
forest, which is a type of Dry forest. Many species
in these forests, including Dialium holtzii, Dra-
caena usambarensis, Croton jatrop hoides and Baphia
kirkii have a Mariime-Riverine ecology, although
Hy menaea is a more catholic Dry forest species.
Ellipanthus hemandradenoides and certain other
uncommon species are recorded from coastal
vegetation over white sands even in the north and
perhaps have an equivalent Maritime-Riverine
ecology. However, several such species have been
excluded from the sample either because they are
(at least nowadays) non-forest species or because
too little is known. The Dialium-Baphia and
Baphia-Hymenaea forests include many Southen
species, and for this reason at least are not
matched by any Kenyan forests.
Eighy-two small tree, shrub, herb and liane
species are in the Dry forest element. These
include Asteranthe asterias, the cycad Encephalartos
hilebrandtii and the liane Stychnos maa-

pioneers of small to medium gaps in forest
(and are probably less fire-tolerant),
although this distincion is not always easy
in pracice.

Moomaw distinguishes three types of Dry coastal
forest in Kenya, including the Combretum-Cassi-
pourea forest on coral rag menioned under
Moist forest. The most widespread type, if inter-
preted broadly (to include Scorodophloeus forest,
often found on slopes) is the Cy nometrﾭ
Manilkara Dry evergreen forest, although areas
dominated by Cy nometra webberi and/or Manilkara
sucata themselves are much less extensive.
Cy nometra-Manilkara forest is usually associated
with hills or gentle undulations typical of the
coastal plateau, usually with reddish soils. Parts of
the Arabuko-Sokoke Forest are of this type, as
are parts of Msumbugwe, Pande and Pugu forests
in Tanzania. These forests are normally domin-
ated by the Dry forest element, with a lesser con-
tribuion from the Maritime-Riverine element
than the other Dry forest ypes. Cy nometra-
Manilkara forests around the Pugu Hills and
Pande include several Southern species, possibly
including the locally dominant Cy nometra cf. web-
beri. Type 1 and type 2 trees other than Cy nometra
and Manilkara sulcata are often found in small
patches associated with this forest ype.
Dry orest trees of ypes 1 and 3 are often
found in Moist forests. hereas type 3 rees are
pioneers in Moist forest, type 1 rees are
someimes locally dominant in Moist forest on
steep slopes or rocky soils, or are common as
lower storey rees. In the ormer case, the pockets
of apparently Dry forest often have a flora rich in
members of the Moist forest element.
As is true in Moist forests, Dry forests are often
distinctively 'flavoured' by members of the
Mariime-Riverine element. A specrum of com-
munities has already been menioned, from Moist
Combretum-Sterculia forest to Dry Combretum-
Cassipourea forest on coral rag (to coral rag thicket
and other communiies close to the sea). The
drier extremes of this progression are dominated
by Dry Mariime-Riverine species.
Moomaw's Manilkara-Diospyros evergreen for-
est, called scrub forest by White (1983), is not