Miombo woodland is a significant biome covering about 10 % of the African land masses (ca 2.5-4 million km2 depending on definition, White 1983; Millington et al. 1994). It is the prevalent vegetation throughout the Zambezian region where soil is freely drained but rooting environment is restricted (see Campbell 1996; Fig. 4.1). Floristically and physiognomically it is very different from other woodland types, and is nearly always dominated by Brachystegia species, either alone or with Julbernadia species or Isoberlinia species (Geldenhuys and Golding 2008). Most miombo woodlands are semi-deciduous, but some are completely deciduous while others are almost evergreen (White 1983; Geldenhuys and Golding 2008). Most miombo dominant species are light demanding and showing some degree of fire resistance, but cannot survive repeated fires (Syampungani 2008). A distinction is made between Wetter Miombo (rainfall > 1,000 mm, canopy height > 15 m, floristically rich) and Drier Miombo (rainfall < 1,000 mm, canopy height < 15 m, floristically poor) (Geldenhuys and Golding 2008). Wet miombo woodland occurs over much of eastern Angola, northern Zambia, south-western Tanzania and central Malawi in areas receiving more than 1,000 mm rainfall per year (Frost 1996). The canopy height is usually 15 m, reflecting generally deeper and moister soils which create favorable conditions for growth (White 1983; Frost 1996). Brachystegia floribunda, B. glaberrima, B. taxifolia, B. wangermeeana and Marquesia macroura are widespread in this vegetation type (White 1983). It is also associated with widespread vegetation namely; dry evergreen forest and thicket, swamp forest, evergreen riparian forest and wet dambos (Fanshawe 1971).

Most miombo species are semi-heliophilous, show some degree of fire- resistance, but however, the dominants cannot survive repeated fierce fires (Lawton 1978). The principal canopy associates are Afzelia quanzensis, Anisophyllea pomifera, Erythrophleum africanum, Faurea saligna, Marquesia macroura, Parinari curatellifolia, Pericopsis angolensis and Pterocarpus angolensis (Chidumayo 1997). Several species of Uapaca and Monotes occur scattered in miombo as shrubs less than 10 m tall (White 1983). They are frequently dominant on shallow soils and in secondary miombo, and are abundant in the scrub woodland that represents the ecotone between miombo and the edaphic grassland of waterlogged depressions (White 1983).

The dry miombo woodland occurs in southern Malawi, Mozambique and Zimbabwe (White 1983; Frost 1996). Brachystegia spiciformis, Brachystegia boehmii, and Julbernardia globiflora are often the only dominants present (White 1983). The dry miombo has three subtypes namely: (i) Brachystegia boehmii-

Democratic Republic of Congo

Angola

Zambia

Botswana

South Africa

Fig. 4.1 Miomboecoregion (Source: Timberlake and Chidumayo (2011))

Brachystegia spiciformis-Brachystegia utilis (ii) Brachystegia manga-Julbernadia woodland and (iii) Brachystegia spiciformis-Julbernadia woodland (Chidumayo 1997). B. boehmii-B. spiciformis-B. utilis is associated with Diplorhynchus condylocarpon, Lannea spp. Ochna spp., and Pseudolachnostylis maprouneifolia as understorey species while the B. manga-Julbernardia woodland has Diospyros spp., D. condylocarpon and Ochna spp., as the common understorey species.