natural vegetation geography sec 1

CLIMATEs AND NATURAL VEGETATION TYPES OF THE WORLD

Temperate Deciduous Forest

Temperate Coniferous Forest

Tropic of Cancer

Tropic of Capricorn

Arctic Circle

Antarctic Circle

Temperate Climate

Temperate Climate

Tropical ClimateEquator

Polar Climate

Polar ClimateWorld Climatic Zones

Tropical / Equatorial Climate

High annual rainfall of at least 2000 mm

High average annual temperature of about 27°C - 29°C

Small temperature range of less than 10°C

Plenty of sunshine all year round

Tropical Rainforests of the world

The 5 layers structure of an Equatorial / Tropical Rainforest

Layers

Characteristics

Emergent Layer(Topmost layer)

Trees can reach up to 40 -50 metres tall to reach out for sunlight.They are supported by strong and large buttress roots.

Canopy Layer

Trees are 30-40 metres tall. The crowns of these trees form a continuous canopy that blocks out 70% - 100% of the sunlight from reaching the forest floor. Hence the interior of the forest is cool, moist and shady. Epiphytes (plants such as wild orchids and ferns that grow on other trees but make their own food) and lianas grow on trees to reach for sunlight.

Understorey Layer Trees are 10 -20 metres tallPresence of smaller trees, lianas and epiphytes that grow up to compete for sunlight.

Shrub Layer Consists of shrubs, ferns and small young trees.

Undergrowth Layer or the Forest Floor

The forest floor is damp and dark as the continuous canopy layer blocks out much of the sunlight. Hence, there is little undergrowth. Fungi, decayed leaves, grasses and broken branches are commonly found here.

1) Evergreen (leaves are not shed all at the same time)

Reason : There is plenty of sunshine and rainfall in the tropical regions so trees are able to grow all year round.

2) Dense / Luxuriant /Closed Forest- Common to have 300 species of trees and plants in 1 hectare

Reason : The hot and wet climate is very suitable for many different species of plant and animals to survive in the rainforests.

APPEARANCE of the forest

Adaptations of Tropical Rainforests to the Hot and Wet Tropical climate

Leaves

Green to dark green Smooth and waxyBroad and big

Broad and big

Drip-tips

Large and broad leaves to take in the abundant sunlight for photosynthesis

Green or dark green to enable them to photosynthesise

Smooth and waxy and some with drip-tips to allow excess water to drain off the surface of the leaves

Tree Barks Shape of trees

Umbrella-shaped crowns

Thin tree barks

Due to the hot climate in the tropical regions, trees in the rainforests do not need to have thick barks to protect them from the cold.

The rounded crowns form a continuous cover (canopy) over the forests. This is due to the abundant sunshine and rainfall that encourage tree growth.

Big strong roots to support the tall trees that can reach up to 40 metres as they grow to catch the sunlight.

Shallow rootsButtress roots

There is an abundant supply of surface water due to the heavy rainfall here. Hence there is no need for the roots to grow deep down to search for water.

Temperate Climate

Moderate rainfall - between 300 and 1000 mm annually

Average annual temperature range from -2°C to 18°C

Large temperature range > 10°C

Places experience 4 distinct seasons

Distribution of Temperate Deciduous Forest in the world

Greenland

North America

South America

Africa

Europe

Asia

Australia

Roots and Tree barks

The roots grow deep down to obtain nutrients and water especially when the top layer is frozen. The trees have thick barks to protect them from the cold in winter.

Appearance of the forests

The Deciduous forest is less dense than the Tropical Rainforest

There are only 3 – 4 species of trees in 1 hectare of land.

Reason: Temperate areas do not get as much sunlight and rainfall as the tropical regions.

Adaptations to the cold temperate climate

Spring

Summer

The Four Seasons of

Leaves and buds begin to grow as the temperatures increase

Flowers are in full bloom. There are more leaves on the trees now.

Autumn

Autumn

Winter

Leaves turn orange, red or brown in order to conserve energy.

The deciduous trees shed all their leaves in Autumn to reduce water loss

Trees are bare of leaves as winter can be harsh and dry.

North America

EuropeAsia

Distribution of Temperate Coniferous Forests in the world

Adaptations to the cold temperate climate

Clue: Think about the shape of the coniferous trees

How do the coniferous trees adapt to the temperate climate especially the cold and harsh winter conditions?

Thick tree barks

Wide and shallow roots

Reason : They protect the trees from the cold and harsh winters

Reason : Trees are able to photosynthesise even at low temperatures

Reason : It gives the tree stability and to allow the snow to slide off the branches without breaking them

Reason : They anchor the trees firmly to the ground and to allow the roots to absorb the melting ice

Branches sloping downwards

Reason : They stop the snow from collecting on the branches

Small needle-like leaves

Reason : They help to reduce moisture loss during the winters

Recap: So far we have studied 3 types of forests1) Tropical Rainforests in the Tropical regions2) Temperate Deciduous and Temperate Coniferous Forests in the Temperate

regions

Let’s make some comparisons between these types of forests and discuss how they have adapted to the climatic conditions they are in.

When making comparisons, you would need to write about the similarities and the differences of the 2 types of forests.

Leaves

Roots

Shape of the tree

Similarities between the Tropical Rainforests and the Coniferous Forests

Leaves

Characteristics Tropical Rainforests Coniferous Forests

Evergreen Both these 2 types of forest have leaves that are evergreen. This means that there are leaves on the trees all year round. They do not lose their leaves all at the same time.


Waxy Leaves Trees in these 2 types of forests have waxy leaves.

This will help the coniferous trees to reduce water loss through the leaves.

As for the rainforests, the waxy surface will help the excess water to roll down the leaves.

Similarities between the Tropical Rainforests and the Coniferous Forests

Roots


Wide and shallow roots

Trees in these 2 types of forests have wide and shallow roots due to the presence of water on or near to the surface. For Tropical Rainforests, the abundant rainfall all year round makes the surface very damp and roots do not need to grow deep to search for water. For Temperate Coniferous Forests, the melting ice in Spring and Summer provides surface water for the roots. The ground is frozen in Winter and the roots will break if they force their way deep into the frozen ground.

Differences between the Tropical Rainforests and the Coniferous Forests

Tropical Rainforests Coniferous Forests

Broad and bigThe large surface are helps to capture the abundant sunlight for photosynthesis.

Small and needle-likeThe smaller surface area helps to minimise (reduce) moisture loss during winter.

Leaves

RootsTropical Rainforests Coniferous Forests

Buttress RootsMost trees have buttress roots to support the tall trunk that can grow up to 40- 50 metres tall.

No buttress rootsConiferous trees have straight trunks that are usually about 25-30 metres tall. They do not need buttress roots to support them.



Thin barksDue to the hot and wet climate, trees in the Tropical Rainforests have thin barks.

Thick barksDue to the cold temperatures especially in winter, trees in the Coniferous Forests have thick barks to protect them from the bitter cold winters.

Tree Barks

Shape of treesTropical Rainforests Coniferous Forests

Umbrella-shapedTrees in the Tropical Rainforests are umbrella-shaped with rounded crowns. The branches are also spread out.

Conical ShapeConiferous Trees are conical in shape to allow the excess snow to slide down easily. This is to prevent the branches from breaking.



Multiple speciesTropical rainforests can support a very large diversity of plants and animals due to the hot and wet climate that is favourable for growth.

One hectare of land can usually support 300 – 400 different species of plants and animals

Few speciesThe cold temperate conditions with harsh winters do not support many tree species.

Coniferous forests tend to have very few species, often 1- 2 different species per hectare of land.

Variety of species

What on Earth is happening?

What is Deforestation?

Is it really necessary?

Deforestation is the large scale removal of trees

YES!!!!

Reasons Explanation Example

Medicinal value Many plant species have medicinal value that can be used for making vaccines.

Quinine, a vaccine to cure malaria is obtained from the cinchona plant

Reasons for deforestation


Land for growing crops

Rainforests are cleared to provide land for growing crops

Forests in the Amazon Basin are cleared to grow food crops such as soybeans


Land for constructing roads

Rainforests are cleared to provide land for constructing roads making places especially the interior of rainforests more accessible.

The Trans-Amazonian Highway has allowed man to access the interior of the forests and to develop it for human settlements



Land for cattle rearing

Rainforests are cleared to provide land for rearing cattle, This is to meet the demand for beef.

Many countries buy cattle from Brazil as they do not have sufficient land to rear their own cattle.


Minerals Rainforests are rich in minerals such as gold and copper.

People need these resources for manufacturing goods and for making jewellery.



Timber Rainforests provide very strong and hard wood that are good for building houses.

Teak and rattan grown in Indonesia are used to make furniture.


Recreational purposes

Forests, especially nature reserves are popular places for people to relax and enjoy nature.

The Bukit Timah Nature Reserve and MacRitchie Reservoir are popular places for weekend workouts and family outings.


Problems Explanation Example

Loss of habitats of plant and animal species

Rainforests are rich in animal and plant life. When they are removed, animals and plants may become extinct.

Many animals in the Indonesian forests suffer and die from hunger and exposure when their food source and habitats are destroyed.

Problems of deforestation


Loss of soil fertility

When soil is eroded away, the organisms like worms and insects will also be removed leaving the soil infertile.


Soil erosion Without trees, there are no roots to hold the soil together. The loose soil can be easily removed by wind or rainwater and deposited into rivers.

Floodings in areas surrounding the Ganges River become more severe in recent years due to large scale deforestation.

Problems of deforestation


Livelihood of tribal groups will be affected

They have no homes to live in when the forests are cleared. They will not be able to adapt easily to other living conditions.

Tribal groups e.g. the Ameridians who depended on the forests for survival are forced out of their ancestral homes.

Problems of deforestationProblems Explanation Example

Loss of water vapour and oxygen

Global warming

Trees provide water and oxygen when they transpire. Without trees, there will be less water vapour in the atmosphere. There will also be less trees to absorb the carbon dioxide.This can result in global warming as well.

Air pollution will become more severe as there are fewer trees to absorb the excess carbon dioxide. Also rainfall amounts have decreased in many places where large scale deforestation has taken place.

So, is deforestation really necessary then?

It is necessary as it helps to meet the needs of people. However, it is very important not to overdo it. New trees should be planted to replace those that have been cut so that the forests can be sustained for use by future generations.

natural vegetation geography sec 1

Education

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