Get premium membership and access revision papers with marking schemes, video lessons and live classes.

Processing. Please wait.

In this lesson we are going to discuss Introduction to Vegetation and Factors Influencing Types
and Distribution of Vegetation

Answer Text:
Vegetation
- Plant cover on the earth’s
surface.
Types of Vegetation
1. Natural Vegetation
-Which grows by natural
means of seed dispersal
without interference and
modification by man.
2. Semi- Natural/Derived
Vegetation
-Natural vegetation which is
in the process of recovering
from interference by man.
3. Planted/Cultivated
Vegetation
-Vegetation planted by people
e.g. forests of exotic trees,
trees in Agroforestry and
plants used as hedges e.g.
cypress.
Factors Influencing Types
and Distribution of
Vegetation
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.
2. 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.
3. 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.
4. 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.
2. 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.
3. 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.
4. Wind
• There is heavy rainfall in
areas where warm moist air
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.
• Overstocking can lead to
overgrazing turning grasslands
into deserts.
• Rehabilitation of deforested
areas can stop the spread of
deserts.