Zambia is in Southern Africa, east of Angola, between 150 00 S and 300 00 E with an area of 752,614 sq km out of which 740,724 sq km are land and 11,890 sq km water (The World Factbook, 2006). Zambia borders with the Democratic Republic of Congo (DRC) (Kinshasa) in the north, Tanzania in the northeast, Malawi and Mozambique in the east, Zimbabwe, Botswana and Namibia in the south and Angola in the west (Figure 1). The country is divided into nine provinces (Figure 2). Lusaka is the capital and largest city (Figure 1). The protruding south-eastern area of the DRC nearly bisects Zambia into two major geographic areas. The Copperbelt contains some of the world’s largest proven copper deposits.
Zambia has a population of 11,262,000, (2005 estimates) and 11,502,000 according to The World Factbook, 2006 (July est.). Figure 3 shows the population density of Zambia. The greatest density is in the Copperbelt and the central provinces (Fagan, 1968a, 1968b; The World Factbook, 2006). Population estimates take into account the effects of mortality due to AIDS. Zambia has a population growth rate of 2.11% (2006 estimate) (The World Factbook, 2006).
Zambia’s president is both the chief of state and head of government. The legislative branch consists of a national assembly comprised of 150 elected and 8 appointed members and the speaker. Both the president and the elected members of the assembly are chosen by popular vote for five-year terms.
Zambia consists largely of a highland plateau, which rises in the east. Elevations range from 915 – 1,520 m and higher altitudes are attained in the Muchinga Mts, where Zambia's highest point, 2,170 metres, is located; the lowest point of 329 metres is at the Zambezi river. Also in East Zambia are Lake Banguwelu, parts of lakes Mweru and Tanganyika and the Luangwa and Chambeshi rivers. The Zambezi River drains much of the west of the country (where the elevation is about 460 – 910 m) and forms a large part of Zambia's southern boundary. The Victoria Falls and the huge Kariba Dam, both on the border with Zimbabwe, are part of the Zambezi in the south. The Kafue River drains west-central Zambia, including the Copperbelt in the north. Several large swamps, or flats, are noted for their concentration of wildlife. The country has numerous national parks (Figure 4) where the emphasis is on tourism rather than conservation. There are four major valleys: the Zambezi, the Kafue, the Luangwa and the Luapula. Zambia has several large lakes: man-made Kariba in the South, lakes Tanganyika and Mweru in the North and Lake Bangweulu in the interior.
The population is almost entirely members of the Bantu ethnic and linguistic group (Figure 5). English is the official language and approximately 75 African languages and dialects are spoken (Figure 5). Most of the population follows traditional African beliefs; about 20 % are Christian, equally divided between Protestants and Catholics. Christianity is the official national religion. Expatriates, mostly British (about 15,000) or South African, live mainly in Lusaka and in the Copperbelt and there is a small but economically important Asian population. The country is 44% urban. An HIV/AIDS epidemic is ravaging Zambia; nearly 1 million Zambians are HIV positive or have AIDS. An estimated 100,000 died of the epidemic in 2004. Over a half-million Zambian children have been orphaned. Life expectancy at birth is just under 40.
Zambia, as the territory of Northern Rhodesia, was administered by the South Africa Company from 1891 until taken over by the UK in 1923. During the 1920s and 1930s, advances in mining spurred development and immigration. Its name was changed to Zambia on independence in 1964. In the 1980s and 1990s, declining copper prices and a prolonged drought hurt the economy.
Most Zambians are subsistence farmers. However, Zambian agriculture has three broad categories of farmers: small-scale, medium and large-scale. Small-scale farmers are generally subsistence producers of staple foods with occasional marketable surplus. Medium-scale farmers produce maize and a few other cash crops for the market. Large-scale farmers produce various crops for the local and export markets. Table 1, illustrates the three broad categories of farmers in Zambia – small-scale (or subsistence farmers), medium and large scale farmers. Of the estimated 600,000 farmers, 76 % are small scale subsistence farmers. Commercial farmers (medium and large scale) with farm size above 20 ha, focus on cash crops. Only 740 commercial farmers (less than one percent) have holdings in excess of 60 ha. While the trend in the number of households in the small-scale category is on the increase, the numbers of the medium and large-scale farmers have remained more or less the same (Hantuba, 2002).
According to the Ministry of Agriculture and Co-operatives, large-scale farmers comprising about 2 % of the farm population, cultivate more than 20 hectares; they are generally characterized by high mechanization and have a well organized farmer network which facilitates the acquisition of inputs. Medium-scale farmers, comprising about 13% of the farmer population, cultivate between 5 and 20 hectares. Small-scale farmers (85% of farmer population), cultivate less than 5 hectares.
Land is held in trust for the nation by the president and people get it on lease for a period of ninety-nine years through the Ministry of Lands. Few smallholders have land with title deeds; the majority have customary use rights; they access land through the customary tenure system by getting the approval of traditional rulers such as chiefs and headmen. Most land in opened-up areas is occupied but unexploited agricultural land, which generally is far from where minimal infrastructure is developed, still remains unoccupied. This has resulted in great pressure on cleared arable land by the fast growing population. Farmers are now constrained in their traditional practice of shifting cultivation (the fertility management methods are explained below) from the previous average period of 15-20 years to 3-4 years now. This is not long enough to sustain soil fertility. Table 2 shows indices of agriculture production from 1997-2005.
Saasa, (2003) identified five major farming systems in Zambia. These are:
Smallholders are mainly associated with the first four systems whilst large-scale farmers are largely associated with the last.
Shifting cultivation. This has been practiced traditionally where the chitemene (slash and burn) has been used and in some medium rainfall regions where fallowing has been used. Fallowing involves leaving completely cleared and de-stumped fields unused for a period of 15 to 20 years (Kwesinga et al. 2003). The dominant crops are maize, cassava, millet, groundnuts and beans. This system is unsuitable in the long run because of inadequate land to allow long fallows; it has seen some level of decline with the fertilizer subsidy system that the Government introduced. Fertilizer replaced the burning of leaves previously used to improve soil fertility. The switch to fertilizer, especially ammonium nitrate exacerbated the acidity of the soils.
Traditional system. This is practiced in the lowest rainfall zone which is generally unsuitable for crop production and prone to droughts or spurts of rainfall that cause floods and crop destruction. The dominant crops are sorghum and maize but the crop output in this region in most cases is low.
The Eastern Province known as the “maize basket,” is characterized by relatively more productive smallholders and widespread livestock production and has higher population and lower land availability than other areas.
Northern Province has higher rainfall, more humid conditions and problems with acid soils and declining soil fertility. Land is relatively abundant and shifting cultivation (e.g., slash and burn) was widespread until recently and is still the norm in some areas. Unlike other areas of Zambia, cassava (and not maize) is the major staple.
Conditions in Southern Province are similar to Eastern Province (tradition of maize and livestock production), except for lower rainfall. Southern Province is of special interest because there are relatively abundant land and water resources. It is an area where cotton production has expanded in recent years and there has been some growth in the number of emergent and commercial farmers.
Western Province is the driest area of Zambia.
North-western Province, in contrast, has high rainfall and conditions are more similar to Northern Province.
Central and Lusaka Provinces have agro-ecological conditions similar to Eastern and Southern Provinces and are located along the line-of-rail.
Zambia faces problems of food and fodder shortage, degradation of non-renewable resources and decreasing access to firewood. Shortages of food and fodder are partly a result of declining soil fertility caused by such factors as soil erosion and degradation and little or non-use of manure or chemical fertilizer and the ravages of erratic rainfall. The population growth rate of 2.11% per annum puts enormous pressure on land, exacerbating problems of food shortage.
Soil restorative fallows, have become shorter and, therefore, ineffective, or disappeared from the farming systems altogether (Saasa, 2003; Kwesinga et al. 2003). Sometimes low crop production is a direct result of poor husbandry, such as late planting due to late land preparation, or draught animals being too weak to plough at the beginning of the rains because of poor nutrition during the dry season. The rapid population increase has also led to deforestation for fuel, wood, charcoal, building poles and timber or to make room for agriculture. It is estimated that deforestation is proceeding at the rate of about 200,000 ha per year; this, coupled with overgrazing, has contributed to severe soil degradation.
About 2,000,000 farmers grow maize - continuously without fertilizer, giving average yields of 0.5 to 1.0 ton ha-1. A household of six people needs about 1.1 tonnes of maize per year. Low yields lead to food insecurity and hunger for up to 6 - 9 months per year. Maize productivity can be raised to above 4 t ha-1 through use of fertilizers. However, these inputs are expensive and not easily accessible by small-scale farmers. Timely delivery of inputs is a problem due to poor rural infrastructure. Only about 20% of households can access inorganic fertilizer. Cultivation is traditional, hoe in particular and the sector is rain-fed. Agricultural products are grains such as maize, sorghum, rice, peanuts, sunflowers; livestock such as cattle, goats, pigs, poultry; and tobacco, cotton, sugarcane, cassava and coffee. Table 3 shows production of some major staple foods.
The government views agriculture as the best alternative to mining due to its contribution to the gross domestic product (GDP) – 18.5% in 1995 and 17.2% in 2000 (BOZ, 2003). The sector has been able to contribute a considerable amount of foreign exchange earnings through the horticultural sub-sector. Table 3 shows output of some major staple food crops from 1997 to 2005, respectively, while Figures 6, 7 and 8 shows the main crop zones, areas under major crops and production of major crops respectively in Zambia. Figure 9 shows the value of major crops in Zambia in 2001.
Within the labour force of 3.4 million, 85% of Zambians, work as subsistence farmers; commercial agriculture is confined to a small number of large farms, while 6% are in industry and % in services. Agriculture is the main source of income for the rural population, especially women, who constitute a high proportion of the rural population and agricultural labour force (DFID, 2002). With the unemployment rate of around 50 % (2000 estimates, World Fact book, 2002), agriculture is often the only source of livelihood or income within the informal sector.
The mining and refining of copper constitutes by far the largest industry in the country and is concentrated in the cities of the Copperbelt. Cobalt, zinc, lead, gold, silver, gemstones and coal are also mined. Manufactures include food products, beverages, textiles, construction materials, chemicals and fertilizer. Most of Zambia's energy is supplied by hydroelectric plants, especially that at Kariba Dam. Copper accounts for over 80% of foreign exchange. The principal imports are machinery, transport equipment, consumer goods, petroleum and petroleum products and foodstuffs. (The World Factbook, 2006; Infoplease.com, 2005).
Once a middle-income country, Zambia began to slide into poverty in the 1970s when copper prices declined on world markets. Over 70% of Zambians live in poverty. Per capita annual incomes are currently at about one-half their levels at independence and, at $430, place the country among the world's poorest nations. Almost one-half of the country's 10 million people are concentrated in a few urban zones strung along the major transportation corridors, while rural areas are under-populated. Unemployment and underemployment are serious problems.
The Zambian economy has been based on copper-mining. Output of copper fell to a low of 228,000 metric tons in 1998, after a 30-year decline in output due to lack of investment, low copper prices and uncertainty over privatisation. Following privatisation of the industry, copper production rebounded, reaching 398,000 metric tons in 2004. Improvements in the world copper market have magnified the effect of this volume increase on revenues and foreign exchange earnings.
The Government is pursuing an economic diversification programme which seeks to promote agriculture, tourism, gemstone mining and hydro power. Despite progress in privatisation and budgetary reform, Zambia's economic growth remains below the 5% to 7% needed to reduce poverty significantly. Privatisation of copper mines relieved the government from covering mammoth losses. Copper output increased in 2004 and is expected to increase again in 2005, due to higher copper prices and the opening of new mines.
Cooperation continues with international bodies on programs to reduce poverty, including a new lending arrangement with the IMF in the second quarter, 2004 (World Factbook, 2006). Zambia industrial production growth rate was estimated in 2004 at 6.9 %, GDP (purchasing power parity), $9.409 billion, GDP - real growth rate 4.6%, GDP - per capita, purchasing power parity - $900; GDP - composition by sector; agriculture: 14.9% industry: 28.9%, services: 56.1%; Labour force, 4.63 million and Labour force - by occupation, agriculture 85%, industry 6%, services 9% (World Factbook, 2006).
Zambia is high plateau, deeply entrenched by the Zambezi river (and its tributaries, the Kafue and Luangwa) and the Luapala river. The Zambezi flows to the south, turning east to make the border with Zimbabwe. In the north are three great lakes, the Tanganyika, Mweru and Bangweulu. Lake Kariba stretches along the southern border. The Mafinga Mountains form part of a great escarpment running down the east side of the Luangwa river valley. The country rises to a higher plateau in the east.
The country has three main topographical features:
Zambia’s vegetation is of the savanna woodlands type in high rainfall regions and tropical grassland in low rainfall regions. Over half of the country is covered by trees, varying from the more open conditions in the drier south to tall dense woodlands in the north and north-west. The trees are only bare for a brief period and the leaves appear before the start of the rains. Grass fires spread rapidly in the dry season but new shoots soon push through the blackened earth.
The vegetation is classified into four major categories: closed forests, woodlands or open forests, termitaria and grasslands (Fanshawe 1971, Storrs, 1995). These are further divided into sub-vegetation types (Sekeli and Phiri, 2002) (Table 4) and diversity in the various vegetation types of Zambia (Fanshawe, 1971) is shown in Table 5.
Closed forests cover about 6% of the country. Cryptosepalum evergreen forests are the most extensive and occur in the western part of the country while the Baikiaea forests in the south west are the second most extensive characterised by the commercially valuable Baikiaea plurijuga (State of the Environment in Zambia, 2000: pp 58-59). Open forests or savannah woodlands are the dominant vegetation type covering 66 % of the land. There are four types of these woodlands the most extensive being Miombo woodlands that covers about 42% of the country characterised by the Brachystegia, Julbernardia and Isoberlinia; followed by the Kalahari woodlands, Mopane, Munga and Termitaria (State of the Environment in Zambia, 2000).
The predominant miombo woodland (a sub-category of the savannah) is two-storied with an open and -evergreen canopy 10 - 20 m high. Termitaria or anthill vegetation covers about 3 % and is present in all regions except in areas of pure sand; it is classified according to its association with other vegetation types; hence: Miombo Termitaria, Kalahari Termitaria, Mopane Termitaria, Munga Termitaria, Riparian Termitaria and Grassland Termitaria (State of the Environment in Zambia, 2000).
Grasslands cover 27% of the land and range from pure grassland to grassland with scattered trees. They occur in poorly drained dambos, flood plains or swamps. The dominant grasses are Themeda triandra, Hyparrhenia spp. and Heteropogon contortus. Forest - mostly savannah bushveld - covers 42% of the land area, having declined at 2.4% per annum. The high eastern plateau consists of open grassy plains with small trees and some marshland. Arable land comprises 7% of the total land area. Figure 11 shows the relief of Zambia.
Upland soils are of low inherent fertility; most are moderately leached sandveldts, loams and clays. Their texture and structure and physical properties vary. Soils in most dambo areas are characterized by a dark colour in the top 30 cm of the profile. In more cases the layer is covered by silt loams underlain by silt clay loam with clay developing in deeper layers. Clay appears to have eluviated to lower horizons into water tables. Black colour is chiefly on account of their high organic matter content. Dambo soils have supported crop production on a sustainable basis for decades without having to apply external inorganic fertilizers on account of their organic matter and high nutrient pool. There is currently an increasing trend to dambo cultivation due to their wetness and high fertility status. The variation in fertility of both upland and lowland dambo soils has to be viewed and approached cautiously with different land management practices if production is to be sustainable.
The soil types in Zambia can be broadly categorized into four regions:-
Based on soil type the following agricultural systems are observed according to Chomba (2004):
In the warm wet season there are frequent heavy rains and thunderstorms, followed by spells of bright sunshine. Plants grow profusely and rivers and streams fill up almost overnight. During the cool dry season, night frosts may occur in places sheltered from the wind. The countryside dries up gradually and grass fires, fanned by high winds, are a feature of this time of the year. In depressions, radiation frosts occurs on cloudless nights. Temperatures rise during the hot dry season but new leaves appear on the trees before the start of the rains and new grass brightens the countryside. The main growing period of woody vegetation is between August and November.
The climate is mainly affected by the movement of the inter-tropical convergence zone. The annual rainfall pattern over the whole country is similar between November and March and the amount of rain varies considerably. Consequently, Bingham, (1995) reported that Zambia can be divided into the following ecological zones based on the amount of annual rainfall:
Plateau with higher rainfall,
Figures 13 and 14 present rainfall patterns in Zambia according to ecological zones. The annual rainfall decreases from an average of 1,200 mm in the north to an average of 600 mm in the south. Rainfall is 508 - 1,270 mm per annum.
Zambia’s climate is favourable for agriculture with abundant arable land receiving 650 mm in the southern part of the country and 1,800 mm in the north (MAFF, 2001). A wide range of crops can be grown; maize, millets, sorghum, tobacco, cotton, rice, wheat and groundnuts. All kinds of vegetables can be grown, together with citrus fruit, bananas, pineapples, mangoes, avocados and grapes. Litchis are a high potential export crop. Tea and coffee grow successful. Sugar cane is grown by villagers and commercially. Figure 15 shows the crop production and rainfall pattern. In the north, rainfall is 1,250 mm or more a year decreasing southwards to Lusaka where it is about 750 mm. South of Lusaka climate is dictated more by the east and southeast trade winds which have lost much of their humidity so far inland. Rainfall in this area is between 500 and 750 mm. In some years the influence of the tropical zone is felt further to the south, resulting in excessive rain in the Southern Province and partial drought in the north.
Except for very rare showers in August, rain is confined to the wet season, which sometimes starts as early as October and finishes as early as March. At the height of the rainy season, it rains on seven or eight days out of ten.
Average temperatures are moderated by the height of the plateaux. Maxima vary from 15 0C to 27 0C in the cool season with morning and evening temperatures as low as 6 0C to 10 0C and occasional frost on calm nights in valleys and hollows which are sheltered from the wind. In the cool season, the prevailing winds, dry south easterlies, come from the southern hemisphere belt of high pressure. Invasions of cold air from the south-east bring cloudy to overcast conditions. During the hot season maximum temperatures may range from 27 0C to 35 0C. However, the mean annual temperature ranges between 18 and 20 oC. The highest annual average temperature is 32 oC and the lowest temperature averages 4 oC. Table 6 presents annual rainfall and representative maximum and minimum temperature during the hottest and coldest months of the year respectively in some cities and towns in Zambia. Annual temperature variation is greatest at Livingstone, the most southerly town and least at Mbala, the town nearest the equator.
The following ecological zones are found in Zambia (also see Figure 14 for agro-ecological regions):
At altitudes ranging from about 1,000m to 1,500m the climate is mild, with maximum temperatures rarely exceeding 350C. The rainfall decreases from north to south. The 1,000 mm isohyet corresponds approximately to the boundary separating the four Northern provinces from the five southern ones. In the higher rainfall areas the traditional staple crop is cassava and there is no tradition of keeping cattle. In medium rainfall areas, the traditional crop is maize and there is a long tradition of keeping cattle.
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. Miombo woodlands are neither strictly evergreen nor deciduous; they are best described as semi-evergreen. Muputu Brachystegia spiciformis is evergreen in good years and on the more favourable sites and deciduous in dry conditions.
Miombo, the plural of "muombo", the Bemba name for Brachystegia longifolia, which dominates extensive areas of the plateau, is regarded as woodland, in spite of its closed canopy (with crowns touching), because its light foliage allows sufficient light to reach the ground to support a continuous ground cover of grasses and other herbs. Since this ground cover burns in most dry seasons, miombo woodland is regarded as a fire climax.
Some woodlands on steep or shallow soils are naturally protected against fire but retain their woodland structure because of the nature of the soil. Others cannot burn because of heavy grazing and tend to become heavily invaded by shrubs. Miombo woodland is defined as any woodland which is dominated by species of: Brachystegia, Julbernardia and Isoberlinia. Unlike most legumes, these do not develop nitrogen-fixing nodules on their roots. Two features which these trees have in common are a characteristic mushroom-shaped crown and that they disperse their seeds by explosive dehiscence of their pods which flings seeds to a distance of up to 25 metres.
Miombo woodland is rich in herbs and subshrubs. Regular burning is necessary for their maintenance; 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. This is also the growing season of most other herbs when they are most vulnerable to damage by trampling.
Miombo woodland produces a great range of valuable forest products. The chief source of indigenous hardwood timber is mukwa, Pterocarpus angolensis. Government restrictions on exports have resulted in a serious undervaluation of mukwa which has led to wasteful use. Another very valuable product of miombo are edible caterpillars, ifinkobala, of emperor moths Saturniidae, which are harvested in great quantities and sold dried in urban markets. An important commercial tree is mutondo, Julbernardia paniculata which may well be the commonest tree of Zambia; it is the most important source of honey. Unlike the other miombo dominants it flowers after the rains, 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 practiced by the Lunda people of Mwinilunga and Kabompo districts for centuries.
Steep slopes and rocky outcrops are protected from fire by the sparseness of the grass cover. Good drainage on slopes ensures that the soil remains friable and free from compaction. These areas are consequently rich in many of the more fire-sensitive plants. Smooth-barked trees and thicket clumps are characteristic features of the vegetation. Hills of limestone and other basic rocks may develop deciduous thickets, with pockets of rich herbaceous vegetation. Characteristic of these hill slopes are the smooth-barked species of Brachystegia B. bussei, B. glaucescens and B. microphylla and the white-barked Sterculia quinqueloba. Miombo species can only thrive where there is sufficient soil. Elsewhere deciduous genera predominate.
The best 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 lack of flammable ground cover. Two of the most characteristic species are mufinsa, Syzygium guineense ssp afromontanum, which is frequently dominant and mofu, Entandrophragma delevoyi, which occurs as an occasional emergent and is one of the tallest indigenous trees. Some of the best of these forests, which are seriously threatened by clearing for cultivation, are in the southern parts of Copperbelt Province.
Owing to the flatness of the terrain, drainage on the plateaux is provided by flat-bottomed valleys called dambos. The water level in dambos rises and falls with the seasons which has a number of consequences: since trees cannot withstand flooding for any length of time the absence of trees marks the highest level to which the water rises. Dambos are features of intense biological activity. Elephant prefer to dig for water at dambo margins rather than taking surface water from the channels because the water entering the dambo contains minerals, which are adsorbed by clay or taken up by living organisms in their passage through the soil.
Dambos which are permanently wet, but have sufficient slope to avoid being flooded, develop into acid peat bogs. These provide habitat for raffia palms, Raphia farinifera, orchids and many other interesting plants. Denitrifying bacteria deplete the soils of nitrogen compounds, thus providing habitats for insectivorous plants, such as Drosera and Utricularia.
Water draining from these peat bogs is often black owing to high concentrations of tannins. Tannins inhibit the digestion of protein by animals. Tannin-producing plants are prevalent in areas of nutrient deficiency, where competition for available nutrients is particularly intense. The grasses and sedges of poorly drained acid dambos are extremely unpalatable to herbivores. However when the soils of these areas are disturbed by heavy trampling, which breaks down their structure, palatable grasses may invade. These areas attract grazing animals, thus extending the replacement of sedges by palatable grasses.
Much of the upper and middle course of the Kafue River, upriver of Kafue National Park, is flanked by wide dambos, consisting of sedge grassland, whereas in the park the vegetation along the river is mainly short grasses which are kept in a palatable state by grazing and by drainage provided by paths to and from the river made by hippo. Where these animals have been eliminated by hunting drainage is poor, the soils acid and the vegetation unpalatable.
There are large tracts of miombo on the plateaux which lack termite mounds. The most extensive areas are the Kalahari Sands where the soils simply have not enough clay to support stable mounds. In many rocky areas and on steep slopes, where soil depth is limited, mounds are generally absent. Mounds are most consistently found at dambo margins, where optimal conditions of drainage and an abundance of suitable clay exist. Termite mounds have long lifespans, measured in centuries. Old trees associated with mounds suggest this and archaeological evidence confirms it.
Some species are highly adapted to termite mounds, such as Euphorbia ingens, other trees, notably the Proteas, are never found on or even near them. Termite mounds accumulate mineral salts. They are frequently rich in lime even when the surrounding soils are deficient. This accounts for the preponderance of lime tolerating plants on mounds. In some areas mounds are rich in salt and these attract animals which eat the soil. Even well fed cattle on commercial ranches cannot resist salty termite mounds, eating away the soil to form a grotto and eventually demolishing the whole mound.
Montane grassland is much more extensive than montane forest. It is extremely rich in herbs, which are at their best after the rains, March - May. After fire these areas appear desolate, but without fire the grassland would turn to scrub and lose its herb flora. Sub-montane areas, above 1,400 m, are much more extensive. Their flora is less distinctive than the that 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 orchid in five different habitats have been recorded (Williamson, 1955, 1975).
The Kalahari Sands
The main differences between the Kalahari sands and the rest of the Zambian plateau are attributable to the very deep, free-draining soil with virtually no clay or silt. Such soils provide an excellent growing medium for deep-rooting woody plants. Since it is deficient in clay the soil can only hold nutrients where there is organic matter. Exposure of the soil to the sun destroys much of the organic matter and such areas tend to remain bare.
Kalahari sand vegetation types
Mavunda. This is a dry-evergreen forest type, consisting of a very dense evergreen shrub matrix, mostly about 4 m in height, with a fairly light overwood in which Cryptosepalum exfoliatum subspecies pseudotaxus (mukwe) is the dominant tree. The two main blocks of mavunda, occurring respectively to the north and south of the Kabompo river, constitute the largest area of tropical evergreen forest in Africa (and probably in the world) outside the equatorial zone. Small outliers of mavunda occur as far south as Sesheke District.
Mukusi forest. This is deciduous and occurs in an area of much lower rainfall than the mavunda forests. Again it consists of a dense thicket with a lighter overwood, but the species are entirely different. The over wood species is mukusi, with one or two others coming into forests of slightly inferior quality is deciduous and occurs in an area of much lower rainfall than the mavunda forests. Again it is a dense thicket with a lighter over wood, but the species are entirely different.
Kalahari woodland, Dambos and Pans
The Bulozi floodplain
Soils derived from Karroo sandstones generally have a higher mineral content than those from the basement complex of the plateaux and the contrast in the vegetation is sharp. The Luapula valley is not part of the rift valley system and belongs to the basement complex. Its natural vegetation is not miombo and although it resembles the vegetation of other valleys in structure, the species are quite different.
Valley vegetation consists of complex mosaics and is affected by the drainage pattern and soils and also by large herbivores which concentrate in these nutrient-rich areas. Deciduous thickets commonly occupy well drained sites. The banks of rivers and lagoons have fringing forest. Slopes between the thickets and the riverine forest are frequently covered with mopane woodland. Grassy plains occur on cracking clays. Lagoons, frequently formed as ox-bow lakes, have a rich variety of aquatic vegetation. At the lower end of the mopane slopes, there are often large termite mounds covered with forest species. These mounds are often partly or completely encircled by pans which hold water for several months into the dry season. Pans begin as wallows and are extended as more mud is carried out on animals using them.
Mopane and mopane woodlands
These conditions are unfavourable to the growth of most trees and the few species that tolerate them must be adapted to take up water rapidly in the short time it is available. Mopane develops a superficial root system which is able to suppress perennial grasses and it is not uncommon to find isolated trees in a circle of taller perennial grass, with only sparse annual grasses and herbs under the trees. This suppression of perennial grasses promotes runoff and soil erosion; gullying is a common feature of mopane woodland.
The soil characteristics of mopane woodland are in complete contrast to those of miombo, 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 where it develops a deep taproot like its woodland associates. Besides miombo and mopane there are other woodland types of minor occurrence. They are generally more open in structure than miombo and lack the characteristic miombo dominants. They occur in situations which are either too dry for miombo, become too wet during the rains, or suffer from fires too severe for the miombo species to tolerate.
Trees such as the baobab Adansonia digitata, Cordyla africana and several other fruiting trees become established in thickets, but once they mature and their ripe fruits fall to the ground, elephants and other heavy herbivores open up the thicket and transform it into a parkland, which is seen in many of the best game viewing areas in the Luangwa and Lower Zambezi parks. Since there is no way that these trees can replace themselves their habitats are not sustainable. Other fruiting trees which can regenerate without the protection of thickets include Acacia tortilis, which forms its own spiny thickets and the fanpalms, Borassus aethopium and Hyphaene petersiana, which have very coarse foliage that resists browsing.
Besides the above, Siacinji-Musiwa, (1999) also classified Zambia into
another 4 broad agro-ecological region zones: