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 329

5-7 months, most areas having a mean annual rainfall between 500 and
1400 mm. Mean temperature ranges from 18 to 29°C, with frequent frosts in the
more southerly areas of the range (Ngulube et al ., 1995).
The tree may occur in extensive pure stands in deciduous woodlands,
upland wooded grasslands and along streams, often on skeletal soils at altitudes
of 500-2000 m (Ngulube et al ., 1995). It has been used as an indicator of poor
soils as it usually occurs in soils with low exchangeable cations and low in
organic matter and macronutrients such as nitrogen, phosphorus and
potassium. U. kirkiana grows on ferruginous or ferralitic soils that are generally
sandy or gravely with good drainage. The species is absent in poorly drained,
heavy, clayey soils (Ngulube et al ., 1995).
According to White's framework, U. kirkiana is a species typical of the
Zambezian regional centre of endemism and the adjacent transitional centres,
the most notable being the Guineo-Congolian and Zambezian regions
(Ngulube et al ., 1995). It is abundant and widespread in mixed communities of
Brachystegia-Julbernardia woodland vegetation. It is usually a dominant or
codominant species and is gregarious, forming dense groves. In high-rainfall
areas (>1200 mm) it forms pure stands with either closed or open canopies,
becoming semideciduous forest with very sparse ground flora (Rattray, 1961;
Shorter, 1989; Ngulube et al. , 1995).
Bush fires, a typical feature of the miombo woodlands, will affect the young
coppice shoots and seedlings, especially when the fire occurs late in the dry
season. Fully grown U. kirkiana has been said to be moderately fire-resistant
(Kikula, 1986; Ngulube et al ., 1995). Its fire tolerance has also played a role in
the succession of miombo woodlands. U. kirkiana was one of the species found
occupying an intermediate successional stage between fire-tolerant woodland
and fire-sensitive dry evergreen forest (Ngulube et al ., 1995).
The main associates of U. kirkiana are Julbernardia and Brachystegia spp.,
Parinari curatellifolia , Pericopsis angolensis , Pterocarpus angolensis and other
Uapaca species (Ngulube, 2000). Other plants include Annona , Burkea ,
Combretum , Ochna , Ximenia , Vangueria , Lannea discolor , Diplorhynchus ,
Dalbergia nitidula , Bridelia and Pseudolachnostylis maprouneifolia (Ngulube et
al ., 1995; Ngulube, 2000).
Studies that have given quantitative information on the relative abundance of
U. kirkiana in plant populations are few, and the information given is mostly on
the dominant height, basal area or the number of stems per unit area. Ngulube et
al . (1995) gives a range of 54-75% representation of Uapaca in natural stands.
Low values of 10-27% as well as high values of up to 90% in pure stands have
been reported (Chidumayo, 1987). Under the slash-and-burn system in Zambia,
natural regeneration after 6 years revealed a contribution of 42% to the basal area
by U. kirkiana while in well-established mature stands in the miombo the
contribution is less than 5% (Stromgaard, 1985; Hogberg and Piearce, 1986;
Ngulube et al ., 1995). In mature miombo stands in Malawi, the number of U.
kirkiana stems per hectare ranged between 27 and 95 (Ngulube et al ., 1995).
However, the gross population structure of individuals

10 cm diameter at breast
height (d.b.h.) was shown to be variable, the stocking rate ranging from 97 to
1073 stems per hectare (Ngulube, 2000).