Geography

Key unit competence

By the end of this unit, I should be able to appreciate the distribution of different

types of vegetation in the World.

Vegetation refers to a community of plants which grow in an area and which gives it distinct character. Vegetation in biological terms is known as “flora”, that is, all vegetation types growing on land and in water.

The world vegetation communities are into categories: forests and grasslands. They are distributed according to the vegetation zones and they include tropical, temperate, tundra, desert, mountain and aquatic/marsh or mangrove vegetation.

9.1. Tropical forests and their characteristics

9.1.1. Equatorial forests

 The equatorial rainforests grow within the tropics between 10 °N and 10 °S of the equator. Equatorial rainforests are sometimes called “rainforests”. Equatorial rain forests cover only a small part of the earth’s surface which is about 6%. They are situated in the Amazon basin in South and Central America, Congo basin in Central Africa, Malaysia, Burma, and West African coastal belt (Nigeria, Ghana, Ivory Coast, Liberia and Central Africa Republic).

The conditions necessary for the growth of equatorial rainforests:

– Equatorial rainforests receive rainfall throughout the year about 2000 mm per

year.

– The equatorial rainforests grow in areas with good fertile soils and well-drained

soil.

– The equatorial rainforests require much sunshine to support their dense

growth.

– The equatorial rainforests require about 23-240c temperature.

Equatorial rainforests are characterized by the following:

– They are evergreen, since the forests receive heavy rainfall throughout the

year with no clear distinct seasons.

– They grow buttress roots in order to support their enormous sizes.

– The major tree species in equatorial are characterized by a long gestation

period. 

– Equatorial rainforests receive rainfall throughout the year with no distinctive

seasons.

– The vegetation in equatorial regions is comprised of four vertical layers starting

from the canopy of the tree to the ferns on the ground.

– Equatorial rainforests are dominated with valuable tree species such as

mahogany, ebony, green heart and redwood.

– The forest floor receives only 2% of the sunlight. This has led to the existence

of little undergrowth.

– The trees are very tall (35 m - 40 m) with a very dense and thick canopy. The

result is that the canopy blocks most of the sunlight falling on them depriving

the plants under them of sunlight.

– Most of the trees in Equatorial rainforests become tall in the search of light.

– There are broad-leaved evergreen forests of dense and prolific growth of flora

as well as fauna.

– The major tree species do not grow in pure stands. Trees of pure stands are

scattered all over the forest.

– Beneath the tree canopy exists a well-developed layering of understory

vegetation, which is so dense and this limits light to reach the floor of the

forested area.

The Equatorial rainforests are associated with various economic activities. These include lumbering as a major activity, provision of local materials which are used in craft industry, provision of fuel, research and study, herbal medicine, agriculture support, etc.

9.1.2. Tropical Monsoon forests 

The Tropical Monsoon Forests are found beyond the equatorial region, between 10 0 and 250 North and South of the equator. This type of vegetation is found in areas such as; Burma, Thailand, the Indo-China region, parts of India, East Java, parts of Northern Australia, small parts along the South Western coastal areas of West Africa.

The conditions necessary for the growth of tropical monsoon forests:

– The tropical monsoon forests receive heavy rainfall, which is around 2000 mm

per year. This is received mostly in summer.

– In cooler seasons such as winter, very little rainfall is received. This is because

these regions lie under the offshore trade winds.

– The tropical monsoon forest requires temperatures of about 270

c. This

temperature is moderately enough to support the growth of various plants.

Tropical monsoon forests are characterized by the following:

– The trees possess trunks that they use to store water during the dry seasons.

– The tropical monsoon forests can grow up to 30 metres in height.

– Trees possess long tap roots that penetrate into the ground to access

groundwater. Inorder to sustain plants’ growth, especially during the dry

winter season when there is unreliable rainfall.

– Tropical monsoon forests shade off their leaves during the dry seasons in order

to minimize water loss.

– Trees have broad leaves due to sufficient rainfall (2000 mm) received during

the wet season.

– Tropical Monsoon forests experience temperatures that reach 280c especially

in Summer.

– Tropical monsoon forests contain valuable hard wood tree species such as the

teak and sandalwood.

Tropical monsoon forests are associated with various economic activities such as lumbering on the wider area, agriculture, craft industry, settlement pattern and provide herbal medicine.

9.1.3. Mountain tropical forests 

The tropical mountain forests are mainly located at a high altitude in the mountains. These usually vary largely along the slopes of Himalayas Mountain ranges and East African Mountain peaks of Rwenzori, Mt. Kenya and other good examples include; Cameroon Mountains, and Ethiopia Highlands. The trees grow in plenty between the altitude 1,500 and 3,500 meters. This explains why such areas are dominated by mountain forests. They have evergreen trees like Teak, Bamboo, and other tree species such as Pine, Fir, Oak, Maple, Deodar, Laurel Spruce, Cedar, cedar pod carp and camphor. All these grow abundantly and dominate the natural vegetation in the area.

The conditions necessary for the growth of mountain forests:

– Mountain forests require much and reliable rainfall;

– Mountain forests require adequate temperature for the growth of tress;

– Mountain forests need deep fertile soil for the growth of forests;

Mountain forests have the following characteristics:

– Mountain forests grow broad leaves and they are evergreen;

– Mountain forests grow thick under growth;

– The forests contain giant evergreen trees that grow on the windward slopes of

the mountain;

– The main tree species are characterized by long gestation period;

The mountain forests are associated with various economic activities such as lumbering on the wider area, provision of local materials, hunting of animals and provide herbal medicine.

Application activity 9.1

1. Briefly explain the geographical conditions that determine the location

of equatorial forests.

2. It has been noted that the environment is composed of varieties of

natural resources that support the socio-economic development of any

country. Forests fall under such natural resources. Explain the influence

of different categories of tropical forests on the development of Africa.

9.2 Temperate forests and their characteristic

Learning activity 9.2

Read the passage provided below and give feedback to the questions that

follow:

Temperate forests occur in Eastern North America, North Eastern Asia, Western and

central Europe. Temperate forests are those which grow outside the tropics. They are

divided into three categories namely deciduous forests, Mediterranean forests and

coniferous forests. Temperate forests are located between 300 and 700 North and 30

0 and 70o South of the equator.

1. Identify the types of forest mentioned in the passage above.

2. Compare and contrast the types of forest indicated in the passage above.

The temperate forests are categorized into 3 categories that include: deciduous forests, Mediterranean forests and coniferous forests.

The conditions necessary for the growth of temperate forests:

– Temperate forests need little supply of sunshine for the successful growth.

– Temperate forests require enough fertile soil and availability of water for

growth.

– Temperate forests require amount about to 750 mm of rainfall in dry periods.

The characteristics of temperate forests

– With high levels of precipitation, humidity, and a variety of deciduous trees.

– Temperate trees are trees that lose their leaves in Winter.

– Trees shed their leaves in fall and bud new leaves in spring when warmer

temperatures and longer hours of daylight return.

– Temperate forests have tall evergreen trees dominating the regions.

– They have Redwood trees which are the tallest in the world, about 360 feet

high.

– The most prominent tree type in temperate forests is the Douglas fir, that is

growing 280 feet tall.

– Temperate forest mature species of cedar and spruce trees typically exceed

200 feet in height.

– Temperate forests have epiphytes species such as mosses and ferns that live on the branches and trunks of the trees, especially the broad-leafed maples.

– Temperate forests have many species of large ferns which occupy the shady

forest floors.

– Temperate forests can get from 60 to 200 inches of precipitation annually.

The temperate forests are associated with various economic activities. These include tourism which is supported by the presence of many different species of birds such as broad-winged hawks, cardinals, snowy owls, and pileated wood peckers that attract very many people from different parts of the world. There is also hunting due to different types of animals such as white-tailed deer, raccoons, opossums, porcupines and red foxes.

9.2.1. Mediterranean forests 

The Mediterranean forests are located mainly in South West America, Spain, Italy, France, Australia, Algeria, Morocco, Tunisia, and Central Chile. Mediterranean forests grow also well on the tip of South Africa near Cape Town.

The characteristics of Mediterranean forests are:

– Tree species in the Mediterranean are deciduous.

– The mediterranean vegetation is characterized by open and evergreen

woodlands.

– The mediterranean vegetation has thicket with thin and waxy leaves.

– There is inadequate undergrowth.

– They are composed of broadleaf trees, such as the oak and mixed sclerophyll

forests.

– Mediterranean vegetation has dense foliage composed of broad-leaved

evergreen shrubs, bushes, and small trees usually of less than 2.5 m (about 8

feet).

– Tall trees grow in regions lying between 30° and 40° North and South latitudes.

– Trees even fully grown are often stunted.

– There are woody, evergreen shrubs or small trees that have developed various

strategies of growth and usage of available water during the dry period.

– Mediterranean deciduous tree species have a long gestation period.

– Mediterranean plants have long taproots to reach underground water, called

“Xerophytic Plants”.

– Mediterranean trees adapt themselves to dry summers with the help of their

thick barks and wax coated leaves. These reduce the rate of transpiration.

The Mediterranean forests are associated with various economic activities such as mining of oil, tourism, and very limited population settlement. There is also rearing of sheep and growing of crops such as wheat, oats and cultivation of chestnuts.

9.2.2. Coniferous forests / Taiga 

Forest The coniferous forests are located across North America, Europe, and Asia. These forests are found within the extent of 50˚ to 60˚N. The coniferous forest is the largest terrestrial vegetation covering about 17% of Earth’s land area. Countries such as Canada, Russia, and Scandinavia are almost entirely covered by these coniferous forests. The vegetation is identified by its climate, which occurs almost exclusively in the high latitudes of the Northern hemisphere.  

Coniferous forests are favoured by the following environmental conditions:

– The coniferous forests require inadequate supply of sunlight.

– The coniferous forests need medium fertile soil with availability of water.

– The coniferous forests grow well with an average temperature of below 430 F

during the winter season.

 The characteristics of coniferous forests are:

– The coniferous forests consist of tall and softwood evergreen trees.

– There are limited species of trees. The existing trees are evergreen and grow

apart.

– The coniferous tree species grow tall, straight and contain few branches.

– The type of trees in these coniferous forests grow in pure stands;

– Trees are conical shaped with needle-like leaves. These include firs, pine and

cedar which are important variety of trees in these forests;

– The tree species often grow to a height of over 30m (100ft) tall;

– Coniferous tree species grow shallow roots and can collect enough water from

top soil;

– They have shallow roots used to absorb the nutrients and water from the top

soil;

– The coniferous vegetation has adapted to harsh conditions associated with

winter season.

– Leaves are small, narrow and often needle-like with the capacity of reducing

transpiration.

The coniferous forests are associated with various economic activities which include lumbering, tourism, apiculture (bee keeping), hunting, herbal medicines, fruit gathering and Research and study.

9. 2.3. Deciduous forests 

Deciduous forests grow well within the latitude of 40° N and 60°N and 30° S and 50oS of the equator.They can be found in the Eastern half of North America, and the middle of Europe. There are many deciduous forests in Asia. Some of the major areas having deciduous forests include Southwest Russia, Japan, and Eastern China. South America has two big areas of deciduous forests in Southern Chile and in the Middle Eastern coast of Paraguay. These are also located in New Zealand and South Eastern Australia also.

The conditions necessary for the growth of deciduous forests:

– Deciduous forests require moderately distributed rainfall.

– Deciduous forests need low sunshine supply.

Characteristics of deciduous forests:

– Trees shed their leaves in the dry season to conserve water.

– Deciduous forests are characterized by the existence of epiphytes which

include mosses.

– Trees like sandalwood, teak, ebony, bamboo, etc. are the common trees found

here.

– Deciduous forests have a short growing gestation.

– Deciduous forests grow in pure stands.

– Deciduous forests require low sunshine supply.

– They contain hard wood tree species such as maple, oak, beech and hazel.

The deciduous forests are associated with various economic activities which include lumbering, tourism activity, hunting, herbal medicines and fruit gathering.

Application activity 9.2

Describe briefly different types of temperate forests.

9.3. Grasslands in the tropical zone and their characteristics

Tropical grasslands are commonly known as savannah vegetation. Tropical grasslands grow well within altitude of 50 N and 15o N and 50 S and 15o S of the equator. Tropical grasslands grow well in Africa, South America specifically in Campos in Brazil”. They can also be found in Guyana, Australia, Eastern Madagascar and India. Tropical grassland is divided into two groups: Savannah and steppe.

9.3.1. Savannah humid vegetation

 Savannah humid forests grow well in regions experiencing the average total rainfall of 1000 mm per year. Mambo woodlands of Central Tanzania is one of the examples of savannah woodlands in East Africa. Other examples of savannah humid forests are found in Madagascar, Indian subcontinent, South East Asia and New Guinea.

 The conditions necessary for the growth of the Savannah humid vegetation:

– The savannah humid can grow well in regions experiencing temperatures

ranging between 250 c to 320 c.

– The savannah humid vegetation grow well in areas which experience rainfall

about 750 mm to 1000 mm per annum.

– The savannah humid needs maximum sunshine and light necessary for the

plants to make chlorophyll.

Its characteristics include the following:

– The tree species are deciduous, and shade leaves during the dry periods.

– The vegetation is mostly composed of shrub and short grass.

– The species of trees such as baobab and acacia are mostly common in the area.

– The grass can grow very tall (about 3 to 4 meters high). The common type of

grass is known as “elephant Grass”.

– Near riverbanks and water holes, deciduous trees can grow, e.g. Acacia,

baobab, etc.

– The Savannah vegetation is characterized by undergrowth dominated by

shrubs and short grasses.

– Most tree species in the savannah woodlands form small umbrella –like tops

such as acacia.

– The tree species are deciduous and shade –off leaves during the dry season.

– The tree species such as the acacia and baobab are more dominant in savannah

humid forests.

– Shrubs growing in this area have yellow or white flowers and can grow over

six feet tall.

– The non-thorny trees such as baobab, candelabra, and the Jackal berry are

found in savannah grasslands.

The Savannah humid vegetation is associated with various economic activities such as hunting, herbal medicine collection, fruit gathering, rearing of animals and subsistence farming, settlement, mining and gazetting of national park and game reserves.

9.3.2. Steppe/ Savannah dry vegetation 

Savannah dry covers almost half the surface of central Africa and large areas of Australia, South America, and India. The climate is the most important factor in creating a savannah dry vegetation. Savannahs are always found in warm or hot climates where the annual rainfall is from about 508 to 1270 mm per year. These regions receive rainfall for about 6 to 8 months. This is followed by prolonged dry period that usually affects fire out-breaks.

The conditions necessary for growth of Savannah dry/steppe vegetation:

– The soil which is dry and porous, with rapid infiltration of water.

– Dry climatic conditions that support the growth of different grasses due to the

disparities in rainfall and soil conditions.

– Availability of the average annual rainfall of 762-1016 mm.

– The presence soils that are too thin. Trees require the existence of termite

mounds where they grow.

The main characteristics of Savannah dry vegetation are:

– The trees and grass grow through direct competition for water, light and

nutrients.

– The open canopy allows sufficient light to reach the ground to support an

unbroken herbaceous layer consisting primarily of grasses.

– Annual herbaceous plants die completely at the end of the growing season or

when they have flowered and fruited. These grow again from seed when the

wet season sets in.

– The vegetation consists of tall grasses and scattered trees.

– The grasses are usually two meters high or more.

– The trees are mainly found near watercourses. The main types of tree species

are acacia;

– Some trees lose their leaves in the dry season.

– Some plants have thick barks and thorny leaves to reduce water loss.

The Savannah dry /steppe vegetation is associated with various economic activities

including hunting, fruit gathering, rearing of animals, settlement, agriculture and

gazetting of the national park and game reserves.

Application activity 9.3

1. Describe savannah grasslands with reference to South Africa.

2. With reference to the Rwandan context, explain the importance of savannah

grasslands in the economic development.

9.4 Grasslands in temperate zones

Temperate grasslands are known by different names in various regions. “Prairies” in North America; “Pampas” in South America (Argentina), “Downs” in Australia “Velds” in South Africa and “Steppes” in Europe. These are found in the mid- latitudinal zones and in the interior part of the continents. The Temperate grasslands are found in Central Asia from Black Sea to Central Russia, North Central USA and Southern Canada, South-East Australia, Southern Africa and Argentina.

 The conditions necessary for the growth of temperate grasslands:

– Temperate grasslands require minimum light for the plants to make their own

food.

– The temperate grassland requires moderate fertile, fine drained and humid

soil.

– Temperate grasslands need average sunshine in a dry and cool winter time.

– Temperate grasslands require moderate rainfall of about 500 mm - 750 mm for

the best growth of grasslands.

 The characteristics of temperate grasslands are:

– Grasslands found here are short and juicy, which is suitable for cattle feed.

– The region is known for the growth of maize and wheat in large amounts. This

explains why the area is known as “the bread basket” of the world.

– The perennial temperate grasses mostly belong to the family of “Gramineae”.

– The steppes form the largest segment of the temperate grassland biome.

Steppes are divided into: Forest steppes, Meadow steppes and grass steppes.

– America Prairies are divided into three sub regions: tall grass prairie, mixed

grass prairie and short grass prairie.

Brief description of Temperate grassland areas:

– Based on the rainfall, the Pampas in South America (Argentina) are divided

into two types: humid pampas in the Eastern part and Sub-humid pampas in

the Western part of Argentina.

– Velds in South Africa are sub-divided into three types: Themed veld (altitude

varies between 1500-2000m), Sour veld and Alpine veld (2000-2500) of the

Drakensberg mountain.

– Dows grown in Australia are divided into three types:- Temperate tall grasslands

found in the Eastern coast of New South Wales to Victoria and Tasmania. -

Temperate short grasslands found in the North of the Temperate tall grassland

region. - Xerophytic grasslands developed in the interior lands of New South

Wales and Queensland where semi-arid climate prevails.

– Canterbury grasslands are extended especially over the Eastern and the

Central part of New Zealand.

The temperate grasslands are associated with various economic activities which

include: hunting, fruit gathering, rearing of animals, settlement, agriculture and

gazetting of the national park and game reserves.

Application activity 9.4

 Assess the contribution of Temperate grasslands to the economy of the countries where they are found.

9.5. Desert Vegetation

Desert vegetation grows in the Western margins of the continents between 15° – 30° North and South of Equator. The iggest deserts are: Sahara and Kalahari in Africa, Thar in India, Arabia desert covering the countries of Saudi Arabia, Iraq, Iran, Syria and Israel, Atacama Desert (Peru and Chile), Southern California in USA, Sonora in Mexico and Victoria in Australia. Desert Vegetation is divided into two types, namely hot desert and cold desert vegetation or Tundra.

9.5.1. Hot desert vegetation 

Hot deserts are located between the latitudinal belts of 15°-30° North and South of the equator. These deserts can be found in North America, South Asia, South and Central America, Africa and Australia. Hot desert vegetation experiences hot climatic conditions throughout the year. The rainfall is unreliable. This is caused by the dry winds that blow over the area, leading to arid conditions. Such conditions leave behind very poor vegetation in the desert region.

The conditions necessary for growth of hot desert vegetation:

– The presence of poor quality and infertile soils.

– Availability of about 250mm or less as total rainfall per year.

– The prevailing of high temperatures ranging between 290c and 310c to

support the growth of plants associated with arid areas such s deserts.

Hot desert vegetation is characterized by the following:

– Plants in Hot deserts have small leaves, with sunken or restricted openings,

pale and reflective leaves.

– There are a few plants with succulent stems, long roots and leaves.

– The desert trees shed off their leaves occasionally primarily to minimize on the

water loss from the excessive temperature.

– Desert vegetation types especially the tree species grow long taproots to have

access to water that is found deep in the underground water table.

– The main vegetation growing here is mainly thorny acacia, bushes, euphorbia

and turfed coarse grasses.

– Some desert vegetation types grow no leaves in order to avoid excessive water loss through evapotranspiration.

9.5.2. Cold desert vegetation 

The cold vegetation is located in high flat areas called plateaus. It is also common in mountainous areas in temperate regions of the world. Temperate regions lie between the Polar Regions and the tropics. Like other types of deserts, cold deserts get very little rain or snow and are mainly in the Northern part of Canada, North Russia, North Sweden and Finland islands in Arctic Ocean.

The conditions necessary for growth of cold desert vegetation:

– Cold desert vegetation needs low sunshine for its successful growth.

– It requires a combination of freezing temperatures, poor soil quality, lack of

moisture and sunlight.

– This vegetation requires soils associated with relatively high soil salinity.

– The cold desert vegetation needs very little rain fall (of about 250 mm) during

the summer season and snowfall during the winter.

– It requires areas characterized by frost conditions.

The major characteristics of cold desert vegetation include the following:

– Plants are widely scattered.

– The main plants are deciduous, mostly having spiny leaves.

– The cold desert vegetation grows in areas with large amount of snowfall in

winter (and sometimes in summer).

– The cold desert vegetation experiences short and wet moderately warm

summers.

– It experiences the mean average winter temperature that ranges from - 2 to

4º c.

– This vegetation receives a mean annual precipitation that ranges from 90 mm to 260 mm. – The cold desert vegetation does well in areas with good drainage that facilitates the leaching of most of the salts.

The cold desert vegetation is associated with various economic activities that include tourism, mining and agriculture on small scale and establishment of the national park and game reserves.

Application activity 9.5

 Referring to Sahara Desert, describe the impact of the desert vegetation and climatic conditions on the population settlement in any country around it.

The tundra vegetation is found in coldest regions of the world. The term tundra is derived from a Finnish word “tunturi” which means “treeless plain”. It is among vegetation types that strive in the harshest conditions. This vegetation is found in the arctic region on top of mountains where climate is cold, windy and with limited rainfall. The tundra vegetation is found in regions that cover the areas of Alaska, parts of Russia, Northern Scandinavian countries and in some parts of Canada.

The following are the conditions necessary for the growth of tundra

vegetation: 

– The Tundra vegetation requires winters that are cold, long and dark.

– It does well in regions that experience about 6 to 10 months with monthly

temperatures below 32° F or 0° c.

– This vegetation needs limited precipitation and the existence of strong and

dry winds. 

– It requires snowfall conditions that support the survival of plants and animal

life. It sometimes acts as a protection layer on the surface of the ground.  

 The characteristics of the tundra vegetation are as follows:

– There is a limited variety of trees.

– The vegetation arrangement is simple. 

– The season of growth and reproduction is short. 

– The drainage system is nearly limited. 

– The nutrients and energy here is in form of dead and organic material.

The tundra vegetation is associated with various economic activities that include tourism which is associated with the following tourist attractions: Birds like ravens, falcons, snowy owls and snow geese and animals such as foxes, wolves and some smaller mammals like the lemmings and snowshoe rabbits. These areas also support hunting, oil exploitation and research and study.

Application activity 9.6 

For either Russia or Canada, describe the necessary geographical conditions for the growth of the tundra vegetation in that country.

9.7. Mountain vegetation

Learning activity 9.7

Using your previous knowledge and geographical sources, answer the

following questions:

3. Describe the mountain vegetation in the tropical zone.

4. Describe the characteristics of mountainous vegetation with reference

to East Africa.

Mountain vegetation is categorized into two types; namely, tropical mountain vegetation and temperate mountain vegetation.

9.7.1. Tropical Mountain vegetation

 the mountain vegetation has a variety of vegetation ranging from the tropical to the temperate types. On a typical Mountain slope, various vegetation types show clear demarcation zones. The savannah vegetation grows from the foothills, followed by the layer of tropical rainforests, bamboo forests, mountain heath and moorland.The rest is bare rock. This type of vegetation is traced in areas such as: Mt. Kenya, Mt. Aberdares, Mt. Kilimanjaro, Mt. Meru, Mt. Elgon, Mt. Cameroon, Mt. Ruwenzori, Mt. Virunga, Mt. Simien and Mt. Bale.

The conditions necessary for the growth of the mountain vegetation

– This type of vegetation requires the steep gradient.

– It needs well distributed rainfall characterised by humid conditions.

– It grows well in areas which generally are associated with strong seasonal

differences.

– It requires temperature ranges of about 20° C at 900 m and 4°c in the summit

region.

– It requires the annual precipitation of around 900 mm on the foothills, around

2000 mm at 1500 m and well above 3000 mm between 2000 and 2300 m on a

windward side.

– It requires fertile soils that are well-developed with moderately acidic soil pH

values, such as Andosol.

Characteristics of the mountain vegetation

– The vegetation on the mountain slope grows in clearly demarcated zones

from the foothills to the summit.

– The mountain vegetation is dominated by tussock grasses and stands of giant

rosette.

– The mountain heath and moorlands grow between the bamboo forests and

the snow-line or bare rocks.

– The tree species, mainly of the lower canopy are the wild olive.

– Soils in the mountains are mostly young and fertile which favours the growth

of trees.

– Above snow-line, plant life is always impossible. This is attributed to low

temperature and the presence of eroded bare rocks that makes it hard for

plant growth.

– In mountainous areas, the decrease in temperature with increasing altitude

leads to the corresponding change in natural vegetation.

– The wet temperate forests are suitable between 1000 and 2000 mm.

– Temperate forests containing coniferous trees like pine, deodar, silver fir,

spruce and cedar are found between 1500 and 3000 mm.

The mountain vegetation is associated with various economic activities. These include gazetting of the national park and game reserves, tourism etc.

9.7.2 Temperate mountain vegetation

 The temperate mountain vegetation grows well in High Mountains of temperate regions. This grows best between 350 N and 600 N of the equator. The temperate mountain vegetation is in the Alps, in Western Europe, in Norway, Sweden and Finland. Other traces of the temperate mountain vegetation can be found in California on the Rocky Mountain slopes, in British Columbia and Andes in South America.

Characteristics of the Temperate mountain vegetation

– Temperate mountain vegetation contains both deciduous and coniferous

plant species such as poplar, birch, oak and elm.

– The vegetation arranges itself on the slope in clear demarcated zones.

– Some trees species grow a thick bark in order to store enough water to be

used in the winter season.

– Tree species shed-off their leaves in winter when the temperature drops below

6° c.

– Tree species especially the coniferous forests adapt themselves to the climatic

conditions by growing tiny needle-like leaves.

– Tree species become shorter and more dispersed towards the zones containing

meadow. 

Application activity 9.7

1. Explain the use of the mountainous vegetation with reference to North

Rwanda.

2. Critically examine the role of the temperate vegetation to the economy of

Switzerland

(1) Mangrove vegetation 

This is the type of vegetation that grows in marshy and swampy areas along the coast of East Africa. It is found in areas such as the coastal regions of Kenya and Tanzania, Deltas of the Ganga, Mahanadi, and Ganga Brahmaputra delta in India. The Mangrove vegetation is evergreen and grows along the coastal margins between 5o N and 5oS of the equator.

The conditions necessary for the growth of mangrove forests:

– They need average temperatures of the coldest month higher than 20°C.

The seasonal temperature range should not exceed 5°C. They can tolerate

temperatures of 5°C, but the development will be affected because they are

not resistant to freezing.

– They need a large tidal range. This causes limited erosion and deposition of

sediments.

– They need a fine-grained substrate. However, there could be some exceptions.

This is the case in Papua New Guinea and Kenya, where the mangroves grow

on corals.

– The shores must be free from strong wave action and tidal current.

– The mangrove vegetation requires swampy and marshy areas with deep soils

which must be salty in nature.

– The mangrove vegetation requires a high temperature necessary for

chlorophyll making.

Characteristics of mangrove forests:

– Mangrove vegetation have broad branches and leaves and they are evergreen.

– They are associated with saline soils with poor drainage.

– The dominating plants are trees.

– The mangrove vegetation grows butters roots.

– This type of vegetation has a long gestation period.

– They exist in areas with poor drainage and sufficient water supply. Such areas

are waterlogged.

– They grow in areas that are hypoxic (oxygen deficient) waterlogged soil strata,

with limited tidal pressures, strong winds and sea waves.

– Mangrove forest species survive under temperatures above 66° F (19° C). They

do not tolerate temperatures below 18° F (10° C). However, temperatures

below freezing should not occur for a long time.

(2) Aquatic plants:

 The aquatic plants or vegetation is referred to as hydrophytes or macrophytes. These plants require special adaptation for living submerged in water, or at the water’s surface. Aquatic plants can only grow in water or in soil that is saturated with water.

The following are the Characteristics of aquatic plants:

– They have reduced and shallow roots. The primary function of these roots is to

anchor the plant to the ground.

– Plants that normally are submersed, typically form their flowers raised above

the water surface.

– Some of the aquatic plants float on the surface of water with no attachment

to the mud or bottom. These have inflated portions of leaves, stems, or special

hairs that enable the plant to remain floating.

– Plants rooted in the mud have immersed leaves with photosynthetic stems.

They also have relatively small leaves similar to those of typical leaves of

terrestrial plants living nearby.

– They have real roots that link with underground roots. Such have numerous

pores over their surfaces that allow gaseous exchange.

– The aquatic plants have structures that anchor as seaweeds to the substratum,

such as the bottom layer or submerged bedrock.

Marsh vegetation: 

A marsh is a wetland that is dominated by herbaceous rather than woody plant species. Marshes can often be found at the edges of lakes and streams. In such places they form a transition between the aquatic and terrestrial ecosystems. The marsh vegetation is dominated by grasses, rushes or reeds. Familiar examples of marsh vegetation include cattails, sedges, papyrus and sawgrass.

The following are the characteristics of a marsh:

– The mash vegetation grows in poorly drained water.

– The mash vegetation is a common characteristic of wetlands areas.

– The mash vegetation grows in both fresh and salty waters.

– The mash vegetation is found along the rivers and lakes.

Swamp Vegetation 

The swamp vegetation occurs along large rivers where they are critically dependent upon natural water level fluctuations. When a swamp vegetation is dominated by forest, it is called a wetland. Some swamps have hammocks or dry-land protrusions, covered by aquatic vegetation or the vegetation that tolerates periodic inundation.

Characteristics of the swamp vegetation are:

– They are characterized by poorly drained soils and different plant life

dominated by trees.

– The latter characteristic distinguishes a swamp from a marsh, in which plant

life consists largely of grasses.

– They grow in waterlogged areas where there is sufficient supply of water which

allows or stimulates the decay of organisms and prevents the accumulation of

organic materials.

– They are often found in lowlands associated with rivers that supply the water

to some lakes.

– The number of plant species in swamps is small. While the one found in

areas associated with well-watered conditions and no waterlogged land,is

sifignicantly great.

All swamp vegetation such as mangrove, mash, wetlands and aquatic forests, are associated with various economic activities. These include tourism, the hunting of large invertebrate sand waterfowl,the fishing of crayfish and mudfish. They are also used for research and study purposes. These support art and craft making.

Application activity 9.8

 Clarify conditions that prove that the East African coast is dominated by mangrove vegetation.

9.9 The factors which influence natural vegetation

Learning activity 9.9 

Make a field trip in your home area and observe types of vegetation. Use the results of your observation to explain the factors influencing their distribution.

There are various factors that influence the growth and distribution of natural vegetation. There is no single factor that plays a key role alone, but rather a combination of two or more factors. These factors include:

– Rainfall: the growth of vegetation depends on the amount of the rainfall. For example, Equatorial rainforests have evergreen and dense vegetation. On the other hand, places with low rainfall have scattered vegetation. This explains why there is little vegetation in deserts.

– Temperature: Forests found in cool areas have fewer tree species. Those in hot

areas have more species. The cold mountain tops have heath and moorland.

– Relief and altitude: It has been noticed that with a rise in the altitude, the

plants in the region show a stunted growth. Trees such as pine, silver fir, birch,

and juniper fall in this category of vegetation. These contribute to variations in

the vegetative zonation along the slope.

– Slopes: Areas on the opposite sides of mountains have different vegetation.

Steep slopes have more runoff. Gentle slopes allow water to sink into the soil.

Plants use this water.

– Soil types: This factor provides basis for different types of vegetation. The

sandy soils in the desert support cactus and thorny bushes. Wet, marshy or

delta soils support mangroves and other deltaic vegetation.

– Human activities: These include the settlement, mining, farming and livestock

keeping. For example, vegetation is cleared to create space for building houses.

Trees are cut for firewood and timber. New or artificial vegetation is planted.

– Drainage also determines the vegetation of a place. There are plants that grow

best in areas of good drainage while others grow well in swampy conditions;

for example the papyrus which only grows in swampy areas.

Application activity 9.9

 Describe the influence of human activities on the vegetation distribution in Rwanda.

9.10. Importance of the natural vegetation

Learning activity 9.10

 Make a field trip in your home area, observe the nature of the vegetation and explain its significance to man.

The following are the significance / importance of vegetation to man:

– Plants that form thevegetation are the main source of food for humans.

Thisfoodisin theform of vegetables, fruits, grains, cereals, leaves, seeds and it

consistsof carbohydrates, oils, proteins, vitamins and minerals.

– It provides construction materials; for example: trees are used for the

construction of houses, bridges and poles.

– The vegetation helps regulate the flow of numerous biogeochemical cycles

in the atmosphere, most critically those of water, carbon, and nitrogen. It also

contributes in the local and global energy balances.

– The natural vegetation plays an important role in our ecosystem. Whereby,

plants are known as the primary producers since they can manufacture their

own food through the process of photosynthesis using sunlight.

– The natural vegetation provides man with a variety of products which include

flowers, stems, roots, oil and many others. These are used to meet man’s needs

such as themaking of perfumes, cosmetics and aesthetic purposes.

– The natural vegetation provides food for some domestic and wild animals.

Human beings also get food from some plants.

– The natural vegetation has contributed hugely to the world´s economy,

particularly in the use of fossil fuels as an energy source. It provides thebiomass

and some vegetation residuals are used to produce biogas.

– The natural vegetation provides timber for furniture. Items as beds, chairs and

tables are made from timber. Timber is also used in construction activities.

– The natural vegetation plays a key role in soil formation. Their roots facilitate

weathering.

– Dead vegetation becomes humus, which makes the soil fertile.

– The natural vegetation is also a natural resource thatprovides anumber of

uses to man;i.e. the products like ropes, rubber, gum, papers, and wood

used in themanufacturing of books, rope, tyres, and seatscome from the

natural vegetation. Some plants have medicinal contents. Herbs are used in

thetreatment of various diseases that threaten human lives as well as those of

domestic animals.

– The natural vegetation is thesource of materials such as cotton,used in textiles

and fabric materials to makefor humans.

– The natural vegetation such as forests and grasslands attract tourists. These

pay (money) when they visit to see the animals and a variety of flora. The

money is used to develop the social facilities like schools, hospitals etc.

– The natural vegetation helps clean or purify air through harvesting carbon

dioxide from the atmosphere. Again, trees produce oxygen that human beings

and animals use for theirsurvival.

– Places with forests receive more rainfall. This is through the process of

transpiration.

– Areas with forests act as asource of rivers. These are called water catchment

areas.

– Many people get jobs. They are employed as researchers, forest guards and

forest officers.

– The natural vegetation makes the landscape beautiful.

– Tree and plant roots hold the soil together. Therefore, forests protect the

ground (soils) against soil erosion, mass wasting and the general impact of

heavy rainfall. 

The natural vegetation has also the followingnegative influences on man:

– The natural vegetation associated with some pests such as tsetse flies and

ticks which put the lives of people and animals at great risks, since they cause

diseases.

– Some plants are thorny-leaved and they are harmful to human beings and

animals.

– The natural vegetation is a homeplace for dangerous animals which may

attack or harm human beings.

– Some plants are poisonous and may kill human beings and animals when

eaten.

Application activity 9.10

Examine the value of the natural vegetation for thesustainable development of

acountry.

End unit assessment

1. Discuss the distribution of the natural vegetation in the world.

2. Describe the relationship between vegetation and land use.

3. Draw a map of the world and on it, show the following vegetation types:

– Savannah humid

– Mediterranean vegetation

– Desert vegetation

– Mountain vegetation

 4. How do the following factors influence the distribution of vegetation in Africa?

– Variation in temperature.

– Variation in relief