Ecology and Biology of Uapaca kirkiana, Strychnos cocculoides and Sclerocarya birrea in Southern Africa - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 328

unpleasant smell when decaying (AFT Database). Each fruit contains an
exceedingly hard seed, which is covered by fibrous matter. It is usually trilocular
but sometimes bilocular. Each seed locule contains a single light nut filling the
entire cavity, which is sealed by a round, hard disc that protects the embryo
until germination.
A fruit load averaging 500 kg/ha and as many as 18,935 fruits per tree have
been reported for superior phenotypes in Botswana (S. Mateke, unpublished
data). A high vitamin C content in the Nigerian population (403 mg/100 g) has
been reported, twice as high as that in the Botswana population. Thiong'o et al .
(2001) reported a vitamin C content of 90-300 mg/100 g in Kenyan
populations. Hall et al . (2002) contend that the exceptionally high yields
reported elsewhere in the literature may be from larger and older individuals.
18.2.2 Uapaca kirkiana Muell. Arg.
Uapaca kirkiana is a member of the family Euphorbiaceae, subfamily
Phyllanthoideae, in the tribe Antidesmeae, and is the sole representative of
the subtribe Uapacinae (Ngulube, 1996). The genus is distinctive within the
Euphorbiaceae on account of its wood, vegetative and floral characters. The
genus Uapaca has 61 species (Radcliffe-Smith, 1988; Mabberley, 1997). U.
kirkiana is easily distinguished from other Uapaca species by its
characteristically broad, leathery leaves and rounded crown. There has been
no recent revision on a continental scale and the number of distinct species is
probably less than has been thought previously. The greatest diversity is in the
Congo basin and further south in the miombo region. U. kirkiana is native to
the miombo ecological zone of southern Africa, including Madagascar.
Despite the popularity of U. kirkiana among the local population in the
region, there is little information on its biology, management and utilization. A
few supporting biological studies have produced information on variation in
fruits (Mwamba, 1989, 1995), germination and ecological requirements
(Msanga and Maghembe, 1989; Maghembe, 1995) and vegetative propagation
(Jaenicke et al ., 2001). The only extensive work on the ecology of U. kirkiana
has been done by Ngulube and colleagues (Ngulube et al ., 1995; Ngulube,
1996). The salient findings of these studies are briefly summarized below.
Ecology
Uapaca kirkiana occurs naturally south of the equator in Angola, the Democratic
Republic of Congo (DRC), Burundi, Tanzania, Malawi, Mozambique, Zambia
and Zimbabwe (Ngulube et al. , 1995; Akinnifesi et al ., Chapter 8, this volume).
Ngulube et al . (1995) also give the latitudinal and longitudinal limits of its
distribution. Occurrence at low elevations has been reported on the shores of
Lake Malawi, while its presence at high elevations has been reported in the
highlands of Benguela in Angola, Mbeya in Tanzania and Mbala in Zambia. The
whole range of U. kirkiana broadly experiences a main dry season of