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Environment Distribution of Major Soil Types

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Distribution of Major Soil Types

Distribution of Major Soil Types

In the last lecture you dealt with climate and natural vegetation. This lecture looks into soils and fauna. Soil is the medium for plant growth, also offers the surface on which many human activities take place, e.g. industry, agriculture, mining, and transportation. Fauna consists of tamed and wild animals. These are important sources of food and offer means of transportation and tourist attraction.

OBJECTIVES

At the end of the lecture you should be able to..

(i) map the major soils of the continent;

(ii) relate soil to climate, natural vegetable cover and parent material;

(iii ) distinguish the different types of fauna and their habitats.

2.2 Distribution of Major Soil Types
The major soils of Africa are closely related to climatic regions; though other pedogenic factors are also significant. The major soils types are desert soils, latosols brown soils, ferruginous soils, vertisols and sols lessives.

2.2.1 Desert Soil

Most of Sahara and parts of Kalahari areas have thin, shallow and poorly developed soils. They are composed mainly of rock debris and detritus. Sand and reg dominates in the driest parts of the Sahara and Namib deserts. The poor development of the soils is the result of lack of rainfall, vegetation cover and high temperatures in these areas.

Distribution of Major Soil Types

3.2.2 Lotosols

The humid region is covered by tropical soils rich in aluminium and iron oxides, hence called ferrallitic soils or latosols. These deep soils are rich in organic matter and contain red or yellow colouration in their profiles due to leaching. The intense and continous weathering of forest materials and the leaching of silica and the bases have caused the soils to be acidic. Most of the areas containing these soils grow tree crops like cocoa, rubber, palm oil.

Distribution of Major Soil Types

In the East Africa and Ethiopia highlands; as well as central Africa, like young ferrallitic soils developed from basalt and other volcanic rocks. These soils occur in warm humid climate, hence are rich in organic matter. Since these soils also possess abundant base materials they are very fertile. Crops that flourish in such soils include coffee and tea.

3.2.3 Brown/Red-brown Soils

These soils occur in semi arid areas where annual rainfall is less than 500 mm. The movement of the small amount of moisture within the soil profile and the grass vegetation, make possible fairly even distribution of organic matter in the profile. In the Sudan zone the soils are used to grow groundnuts.

Distribution of Major Soil Types

3.2.4 Ferruginous Tropical Soils

These soils correspond to the tropical regime of distictive wet and dry season. The rainfall that occurs is able to move easily iron oxide and clay materials in the soil profile, but silica is least moved. The intense leaching in the wet season looses plant nutrients, hence the soils have average fertility. Moreover, during the dry season the soil hardens and forms lateritic ironstone crust derived from parent material.

3.3.5 Vertisols

These are clay soils formed in depressions or result from rock weathering. Those found in floors of depression are brought by local rains or large rivers that originate at a distance. The soils are black or dark brown in colour, hence called tropical black earth or black cotton soils. The high clay content results in slow internal drainage and develop hard cracks in the dry season. These soils occupy extensive areas in the White Nile. Chad Basin and the Kalahari depression. These soils are also found along river valley where they are used to grow cotton, sugar cane, onions and vegetables.

3.2.6 Sols Lessives

These are soils developed under temperate sub humid conditions characteristic of the Highveld of South Africa. The soils resemble the chernozems of the temperate zone but are leached according to tropical conditions. There is accumulation of clay in the B-horizon and some iron is deposited down the profiles. The distribution of the major soil types in the continent are shown in figure 3.1.

Distribution of Major Soil Types

Figure 3.1: Africa Major Soil Types

3.3 Other Soils
The size, relief and climate of Africa leads to various types of localised soils which cannot fit into defined categories. Calcimorphic soils are found in the Maghreb region. These develop on calcareous materials and when large quantities of calcium bicarbonate exist in the profile. The Mediterranean region of the Cape Province has brown and red soils developed under the hot summers and mild humid winters. Halomorphic and hydromorphic soils are affected by the presence of soluble salts like bicarbonates, chlorides and sulphates. These result from permanent or seasonal waterlogging of the soils.

Choose one major soil type and explain how it is related to natural vegetation of the corresponding area.

3.4 Fauna
Human activities have affected the fauna which is found in the different parts of Africa. For example the clearing of forestland for crop cultivation, mining and construction of industries have reduced the grazinglands for wild animals and confined them in small areas. Hunting has reduced considerably the number of elephants, rhinos and buffalos. Some birds have been forced to migrate to distance area after their habitats have been destroyed by fire, aridity, etc. Thus the fauna found today in Africa is the result of combined effects of natural and human activities. According to Stevens (1975) there are five broad habitats: the forest, savanna, dessert, marine and inland water. In these habitants are found many types of animals which range from small insects to big mammals such as elephants, hipopotamus, buffalos whales, etc.

Distribution of Major Soil Types

3.4.1 Forest Fauna

In this habitat the fauna is related to the vegetation arrangement. High up the trees are found nuts and fruits which are food of flying and leaping animals, such as birds and monkeys. The ground vegetation feeds compact animals like the elephant, gorilla, and rhino. Also in the habit are found burrowing animals like rats which feed on ants, termites, and worms; there are also some species of snakes.

3.4.2 Savanna Fauna

There are many types of fauna found in this habitat as a result of its range of environment. There are herds of herbivores, carrivores and omnivores animals, birds and insects. Some of the herbivores are elephants buffalos, zebras and antelopes. The carnivores include lions and the leopards. These animals have adopted to the environment by having special features, like fast movements and sharp eye sights for protection and hunting, respectively. The common omnivores are the monkeys and the wild pig. The habitat possesses varieties of birds, like the hawk, eagle, ostrich and vultures. There are also many insects like bees, flies, grasshoppers; and snakes like the cobra and the rattle snake.

Distribution of Major Soil Types

3.4.3 Desert Fauna

The fauna found in the dessert is adapted to the conditions of high temperature and water shortage that prevail in the area. Rodents and camels are good examples of such animals. The rodents burrow in daytime to avoid the high temperatures and can obtain water from its diets. Camels adapt to the temperatures by allowing its body temperature to rise in daytime; and feed on succulent vegetation. Others types of fauna common in the desert include bees, termites and sand fox.

3.4.4 Marine Fauna

The oceans and seas around Africa show distinct environments, hence different fauna. The differences are due to water depth and temperatures; and availability of food. The Atlantic Ocean is most cool as a result of the Canary and Benguela currents. The Gulf of Guinea is generally warm. The coasts bathed by the cool currents are rich fishing grounds for sardine and hake species. Along the wide warm continental shelf of Guinea coast are found fish populations of warm oceans.

Distribution of Major Soil Types

3.4.5 Inland – Water Fauna

The environment of inland water in Africa, like lakes, rivers and swamps, offers different habitas, thus a variety of fauna species are found. The fish have adapted to the water movements, nutrients content, availability of dissolved oxygen and other conditions. In tropical Africa a basic uniformity of the fish fauna is its derivation from a mid-Tertiary period fauna. The inland basins of the Nile, Chad, Niger and Senegal have species which resemble each other, such as, the Nile perch and Tilapia galilaea. The lungfish is common in most swamps in the continent.

Also in these inland waters inhabit various mammals, reptiles and birds. The common big animals include the hippotamus and buffalo, while reptiles include crocodiles and snakes. There is also a big population of birds like flamingos and storks.

SUMMARY

There are six major soil types in the continent. These are desert soil, latosols, brown or red brown soils, ferruginous soils, vertisols and sols lessives. These soils have developed according to climate, vegetation cover and parent material that exist in the respective areas. There are also several other soil types which have developed under the influence of local factors, like mini climate and relief.

There are five fauna habitants, namely the forest, savanna, desert, marine and inland-water. In these habitants are found many types of fauna which are adapted to their respective environment. In these habitats live carnivores, herbivores and omnivores animals. They range from big ones, like elephants and lions to small types, such as birds, fish and insects. Some animals are found in more than one habitat, for example, the elephants live in the forest and savannah while birds, snakes are found in almost all habitats.

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