It never fails to come as a surprise to newcomers to the region that many of the woodland trees start their growth cycle in August and September, long before the onset of the rains in November. The flush of new foliage, in spectacular shades of red, is a wonderful sight, and the evening fragrance of the Brachystegia flowers three weeks later lends an air of magic after the heat of the day.
Some Vegetation Of Zambia Include:
Mopane Colophospermum mopane is a very distinctive species familiar to anyone who has visited the Luangwa or Zambezi valleys, where it forms extensive pure stands on the valley floor and lower escarpment slopes. Most people associate mopane with the hot dry valleys, but it also occurs quite extensively on the southern plateau. Its distribution in Zambia is strongly correlated with Karroo sandstone, dating from the Triassic period, which occurs in a number of down-faulted troughs in the much older surrounding basement complex. In the drier parts of its distribution range mopane may dominate most soil types, but on the plateau it is confined to particular soil types, which are alkaline and contain high concentrations of sodium salts. The clays in these soils swell on absorbing water, and rapidly become completely impervious. These conditions are unfavourable to the growth of most trees, and the few species that do tolerate them must be adapted to take up water rapidly for the short time it is available. In fact mopane develops a superficial root system which is able to suppress perennial grasses, and it is not uncommon to observe isolated trees in a circle of taller perennial grass, with only sparse annual grasses and herbs under the trees. This suppression of perennial grasses actually promotes surface runoff and soil erosion, and gulleying is a common feature of mopane woodland areas. The soil characteristics of mopane woodland are in complete contrast to those of miombo woodland, which conserves both soil and water. Yet mopane can grow on deep, well-drained soils, and many of the finest specimens are on such soils. In these circumstances it develops a deep taproot like its woodland associates. Yet it is evident from its distribution that it cannot compete with Brachystegia species and the other miombo dominants.
Miombo woodlands are generally considered to be deciduous, but they are neither strictly evergreen nor deciduous. They are best regarded as semi-evergreen. Muputu Brachystegia spiciformis is evergreen in good years and on the more favorable sites, and deciduous in dry conditions. The name “miombo” is the plural for “muombo”, the Bemba name for Brachystegia longifolia, a tree which dominates extensive areas of the Zambesian plateau. Miombo is regarded as woodland, in spite of its closed canopy (with crowns touching), because of its light foliage which allows sufficient light to reach the ground to support a continuous ground cover of grasses and other herbs. Since this herbaceous ground cover dries out and burns most dry seasons, miombo woodland is regarded as a “fire climax”, a vegetation type which is maintained by regular fires. Some woodlands on steep or shallow soils are naturally protected against burning, but retain their woodland structure because of the nature of the soil. Other areas cannot burn because of heavy grazing pressure by cattle. Such areas tend to become heavily invaded by shrubs. Miombo woodland is defined as any woodland which is dominated by species of three related genera in the family Leguminosae: Brachystegia, Julbernardia and Isoberlinia. Unlike most other leguminous plants, these do not develop nitrogen-fixing nodules on their roots.
Two features which these trees have in common are the characteristic mushroom-shaped crown, and that they disperse their seeds by the explosive dehiscence of their pods. The violent twisting of the two valves of the pod flings the seeds to a distance of up to 25 meters. Miombo woodland is also rich in herbs and sub-shrubs. Regular burning is necessary for their maintenance. Unburnt dead grass suppresses new growth. Mowing has the same effect as burning, indicating that it is the heat of sunlight on the ground which stimulates new growth. Grazing, however, can be detrimental to the more sensitive herbs, such as orchids and milkweeds, Asclepiadaceae. Miombo woodland provides poor grazing except during the rainy months, when the grasses are young. Since this is also the growing season of most other herbs, they are most vulnerable to damage by trampling at that time.
Miombo woodland produces a great range of valuable forest products. The chief source of indigenous hardwood timber is mukwa, Pterocarpus angolensis, which is logged by pitsawyers in almost every district in the country. Government restrictions on exports have resulted in a serious undervaluation of mukwa which has led to wasteful usage. Another very valuable product of miombo are edible caterpillars, ifinkobala, of emperor moths Saturniidae, which are harvested in great quantities in certain areas, and sold dried in the urban markets. The foodplant of the most important commercial species is mutondo, Julbernardia paniculata. This species, which may well be the most common tree of Zambia, is also the most important source of nectar for honey. Unlike the other miombo dominants it flowers after the rains, thus providing a second honey flow. Because there is little else in flower at that time the honey is less contaminated than Brachystegia honey. Traditional bark-hive beekeeping has been practised by the Lunda people of Mwinilunga and Kabompo districts for centuries.
Dry Ever Green Forests
The best quality miombo woodland may grade into dense evergreen forest, especially at dambo margins, or where there are laterite pavements. Like other forest types they are protected from fire by having no flammable ground cover of grasses and herbs. Two of the most characteristic species are mufinsa, Syzygium guineense subspecies afromontanum, which is frequently dominant, and mofu Entandrophragma delevoyi, which occurs as an occasional emergent, and is one of the tallest of Zambia’s indigenous trees. Some of the best of these forest, which are seriously threatened by clearing for cultivation, are to be found in the southern parts of Copperbelt Province. The best quality miombo woodland may grade into dense evergreen forest, especially at dambo margins, or where there are laterite pavements. Like other forest types they are protected from fire by having no flammable ground cover of grasses and herbs. Two of the most characteristic species are mufinsa, Syzygium guineense subspecies afromontanum, which is frequently dominant, and mofu Entandrophragma delevoyi, which occurs as an occasional emergent, and is one of the tallest of Zambia’s indigenous trees. Some of the best of these forest, which are seriously threatened by clearing for cultivation, are to be found in the southern parts of Copperbelt Province.
Dambos (flat-bottomed valleys) in the higher rainfall area frequently have patches of swamp forest (mishitu in Bemba). These, as the name implies, have wet floors. Some are very rich in species while others consist of just one, musombo Syzygium cordatum. Some of the largest and richest occur in the Mpongwe area of Copperbelt Province. Since the soils cannot be used for cultivation people do not make much use of these forest, and rarely enter them.
Zambia has very little montane vegetation. Four mountains exceed an altitude of 2000 metres: the Nyika Plateau, which is mostly in Malawi, the Mafinga Mountains, also on the Malawi border, Mukutu, an isolated block in Isoka District to the west of the Nyika Plateau, and another isolated peak, Sunzu, south-east of Mbala. Montane vegetation consists mostly of four types, sub-montane forest, miombo woodland, macchia-type scrub and grassland. The Zambian Nyika has two fine sub-montane forests, Chowo and Manyenjere, and Mukutu also has another. Similar sub-montane forest occurs throughout northern Zambia, notably at the sources of the Zambezi, Lunsemfwa and several other large rivers, and also along the upper escarpments of the Luangwa and Luapula rivers. High altitude miombo woodland is usually stunted, the trees seldom growing more than about 6 metres high, and often as little as 2 metres. They are thickly encrusted with lichens and epiphytic orchids. The macchia-type scrub includes many shrubs in the families Proteaceae: Protea and Faurea and Ericaceae: Erica and Agauria and Compositae (especially Helichrysum spp., the “everlastings”). Montane grassland is much more extensive than forest. It is extremely rich in flowering herbs, which are seen as their best in the months after the rains, March – May. After the fires these areas appear desolate, but without the fires the grassland would turn to scrub, and would lose its herb flora. Sub-montane areas, at elevations above 1400m, are much more extensive. The flora is less distinctive than the vegetation of the high mountains, but is nevertheless varied and rich. In the vicinity of the Kundalila Falls in Serenje District. More than 360 species of orchids in five different habitats have been recorded (Williamson).