VEGETATION OF AFRICA

Factors Affecting Vegetation

The factors affecting the vegetation of Africa include:

1. Climatic factors.
2. Geomorphic factors.
3. Edaphic factors.
4. Biotic factors.

 

1. Climatic Factors

• High temperature with low rainfall leads to sparse vegetation.
• The higher the rainfall, the denser the vegetation.
• High temperature and high rainfall lead to luxuriant vegetation.
• Where temperature is low, no plant grows.
• Sunshine provides energy for photosynthesis needed for luxuriant growth.

 

2. Geomorphic or Topographic Factors

• The steeper the slope, the lesser the vegetation.
• Rainfall on steep slopes leads to run-off, leading to low vegetation.
• Eroded top soil in sloppy area does not support vegetation growth.
• Given the same climate and soil, flat lands have denser vegetation.
• In higher latitudes, aspect plays an important role on available energy and vegetation distribution.

 

3. Edaphic or Soil Factors

• The type of soil in an area affects the rate of percolation of water.
• Sandy soils are loose and porous, leading to sparse vegetation.
• Clayey soils do not allow percolation but support little vegetation more than sandy soil.
• Loamy soil supports luxuriant vegetative growth.
• The type of soil determines what plant would grow there.

 

4. Biotic or Human Factors

• The activities of man either support or reduce vegetation.
• Bush burning reduces vegetation.
• Cultivation and animal grazing reduce vegetation.
• Deforestation also reduces vegetation.
• Excavation and mining reduce vegetation.
• Afforestation and irrigation support vegetation.

 

Types of Vegetation in Africa

The vegetation types in Africa include:

1. Tropical Rainforest: This is found in Zaire Basin of central Africa and the coasts of West Africa. It is associated with equatorial climate.

Climatic Conditions Affecting the Vegetation

• Favourable temperature of 26˚C with an annual range of 2˚C – 3˚C.
• Rainfall throughout the year with two peaks (double maxima).
• Annual rainfall of over 2000mm.
• Abundant sunshine and fertile soils.

Vegetation Characteristics

• Forest is evergreen with broad leaves.
• There are various layers of trees – lower, middle and upper storeys or canopies.
• Trees are of great varieties i.e. trees are heterogeneous.
• Trees are not in pure stand i.e. they are scattered.
• Presence of abundant hardwoods.
• Presence of creepers, climbers, epiphytes and parasitic plants.
• The forest has little undergrowth.

Plant communities

The rainforest provides tropical hardwood which includes Iroko, Obeche, Mahogany, Ebony, African Walnut, Opepe, Limba, etc. These woods provide timber for building and other constructions.

Economic Importance

• Provision of hardwood which is the source of timber used for buildings, furniture and other constructions.
• Lumbering is one of the major occupations of the people due to the presence of numerous timbers.
• Cultivation of food and cash crops like yam, cassava, cocoa, oil palm, rubber, etc.
• Hunting of wild animals.
• Rainforests are also tourist centres.
• Provision of foreign exchange through the export of timber and other products.

 

2. Tropical Savanna (grassland): This is found in West Africa, East Africa and southern Africa. It is associated with the tropical continental (Sudan) type of climate.

Climatic Factors Affecting Distribution

Vegetation Characteristics

• The dominant vegetation cover is grass; hence, the name given to the grassland is Savanna or Parkland.
• Presence of tall grasses that is fibrous when old.
• The trees are deciduous i.e. they shed their leaves during the dry season to reduce transpiration.

Plant Communities

• The major plants are grasses called savanna (in Africa and Australia), campos (in Brazil) and lanos (in Orinoco in South America).
• Popular trees include acacia, baobab and shea-butter.

Economic Importance

• Livestock farming due to presence of abundant grasses and low Tsetse fly infestation.
• Arable crop production like rice, maize, millet, sorghum, etc.
• People are involved in hunting for wild animals.
• Savanna is a centre of tourism.
• Nomadic herding is also carried out by the local people.
• The savanna is also used for game reserves or wild life.

 

3. The Mediterranean Vegetation: This is found in the North West of Africa (Algeria, Morocco, and Tunisia) and in South Africa (Cape Town).

Vegetation Characteristics

• The trees are evergreen.
• Plants are adapted to long period of drought prevalent in the region: Tough, small, leathery, hairy leaves to guard against excessive transpiration. Some plants like Oak have tough, thick bark which helps to reduce the rate of transpiration. Some have long roots for drawing moisture from deep down the soil.
• The trees have slow growth throughout the year but quicker growth during the winter rains.

Plant Communities

• The dominant plant species are the evergreen wood plants such as oak, wild olive, cypress and redwood.
• Presence of evergreen coniferous tree (soft wood) such as pines, firs and cedars.
• Presence of Mediterranean bushes and shrubs such as acacia, laurel, rosemary and marquis.

Economic Importance

• Orchard farming where wide varieties of citrus fruits like grape, lemon, orange, etc. are grown. These are used in wine making.
• Viticulture, which is the cultivation of grape fruits, is common.
• Production of oak cork used in corking bottled wine.
• Trees also provide wood for construction purposes.

 

4. Desert Vegetation: This is found in the Sahara, Namib and Kalahari deserts.

Climatic Characteristics

• High temperature between 30˚C and 60˚C.
• Aridity or rainlessness is common.
• Annual range of temperature varies from 9˚C to 20˚C.
• Annual rainfall is about 250mm.
• High rate of evaporation.
• Deserts are associated with cold currents.
• The relative humidity is very low.

Vegetation Characteristics

• Vegetation in deserts is sparse or scanty.
• Common vegetation includes grass, shrub and herbs.
• Most plants are xerophytes (drought resistant plants) like thorny bushes, the bulbous cacti, wiring grasses, date palm and acacia.
• Some plants are halophytes (salt tolerant plants).

Adaptations of Plants to Desert Climate

• Possession of long roots to search for water in the soil.
• Presence of few and wiring leaves or no leaves at all to prevent transpiration.
• Presence of wax on leaves to prevent transpiration.
• Some possess thick succulent stems e.g. cacti, to store excess water.
• Some shed their leaves during drought.

Human Activities

• Food gathering e.g. fruits.
• Nomadic hunting for wild animals.
• Nomadic pastoral farming e.g. rearing of cattle.
• Crop production like cotton, rice, sugar cane, millet, etc. with the aid of irrigation.

 

5. Temperate Grassland (High Veld): This is found in South Africa.

Vegetation Characteristics

• The dominant vegetation cover is grass; hence, the name given to grass land is Savanna or Parkland.
• Presence of tall grasses that becomes fibrous when old.
• Presence of short scattered trees.
• The trees are deciduous i.e. they shed their leaves during the dry season to reduce transpiration.

Plant Communities

• The major plants are grasses called savanna (in Africa and Australia), campos (in Brazil) and lanos (in Orinoco in South America).
• Popular trees include acacia, baobab and shea-butter.

Economic Importance

• Livestock farming due to presence of abundant grasses and low Tsetse fly infestation.
• Arable crop production in rice, maize, millet, sorghum, etc.
• People are involved in hunting f wild animals.
• Savanna is a centre of tourism.
• Nomadic herding is also carried out by the local people.
• The savanna is also used for game reserves or wildlife.

 

6. Montane Vegetation: This is found in Ethiopia, Mts. of East Africa and Mount Cameroun. Thick forest is found on the windward and light vegetation on the leeward side of the highland.