Factors Influencing Types and Distribution of Vegetation in East Africa

Topographical Factors

1. Altitude
   • Coniferous trees are found at high altitudes because they are adapted to cool conditions.
   • There is no vegetation on mountain tops because there are very low temperatures which inhibit plant growth.

1. Terrain
   • Gentle slopes which have deep and well drained soils are best suited for plant growth than steep slopes which have thin soils due to severe erosion and less soil water to sustain plant growth due to high runoff.
   • Flat areas have poor drainage hence are swampy and can only support swamp plants.

1. Aspect
   • There are a wide range of plants on the slope facing the sun and in the direction of rain bearing winds as they are warm and wetter.
   • Grass lands are dominant on the leeward side because they are drier.

1. Drainage
   • There is a large variety of plants on well drained soils while water logged soils have swamp plants such as reeds and papyrus.

Climatic Factors

1. Temperature
   • Plants in warm areas are large in number and grow faster e.g. in the tropical lands. Also there are deciduous trees which shed leaves to reduce the rate of transpiration.
   • In areas with low temperatures there is slow growth of plants and coniferous forests are found there.

1. Precipitation
   • There are a large number of plants in areas with high precipitation and these areas are dominated by forests which are broad leaved to increase the rate of transpiration.
   • Areas with moderate rainfall are dominated by grasslands and those with little rainfall have scanty vegetation of scrub and desert types.

1. Sunlight
   • There is large number of plants in areas experiencing long sunshine duration.
   • There is little undergrowth in tropical rain forests because the canopy prevents sunlight from reaching the ground.

1. Wind
   • There is heavy rainfall in areas where warm moist blow to and hence a large number of plants which may be broad leaved to increase the surface area for transpiration.

Edaphic/Soil Factors

• Fertile soils have a larger number of plants while infertile soils have scanty vegetation.
• Soil pollution e.g. oil spillage cause drying up of plants.
• Deep soils have deep rooted plants such as trees while shallow rooted soils have shallow rooted plants such as grasses and shrubs.

Biotic/Biological Factors

1. Living Organisms
   • Bacteria, earth warms and burrowing animals improve soil fertility resulting into more vegetation growth.
   • Insect and birds pollinate plants enhancing their propagation.
   • Bacteria and insects cause plant diseases of plants resulting in death of some e.g. aphids which affected cypress in late 80s.
   • Large herds of wild animals can destroy vegetation through overgrazing and can turn grasslands into deserts.
2. Human Activities
   • Clearing of natural vegetation for settlement, agriculture etc. can lead to desertification.
   • Bush fires such as burning grasslands for the grass to sprout can cause extinction of some plant species.