chapter 12 natural vegetation

NATURAL VEGETATION

http://www.slideshare.net/TanBK/chapter-11-weather-and-climate-lesson-slides-published

You will learn:

about the relationship between climate and

vegetation

the global distribution of the different types of

forests

the characteristics of the different types of

forests

the benefits of natural vegetation to people

the case study of tropical rainforest in

Singapore

Today’s lesson, You will learn:

what is natural vegetation

what are primary and secondary vegetation

what are the three major types and seven

different sub-types of natural vegetation in

the world

how do climate affect the types of natural

vegetation in the world

What is Natural Vegetation?

Natural vegetation refers to

plants which have grown

naturally and not planted

by people.

Primary and Secondary Vegetation

Primary Vegetation

refers to untouched, unspoiled forest that

exists in its original condition

Secondary Vegetation

Refers to forest that has been disturbed in

some way, naturally or unnaturally

Areas with secondary vegetation have fewer

varieties of plants

Primary and Secondary Vegetation

Types of Natural Vegetation

There are many types of natural vegetation and

they can be grouped into three main major types

Forests

Grasslands

Deserts

Each major type of natural vegetation can be

subdivided into various sub -types

Types of natural vegetation

Forests Deserts

Vegetation

*Tropical rainforests

*Temperate deciduous forests

*Temperate coniferous forests

*Tropical savannahs

*Temperate grasslands

*Hot Desert vegetation

*Cold tundra vegetation

Grasslands

Distribution of Major Climatic types

in the World

Distribution of Natural Vegetation

in the World

As you can see from the map:

Tropical rain forests are found mainly along the

equator between 23.5°N and 23.5°S of the

equator).

Temperate forests can be found mainly farther away

from the equator mainly 23.5oN and 66.5oN, and

between 23.5oS and 66.5oS.

Coniferous forests can be found mainly far from

the equator in the northern hemisphere (between

60°N and 70°N of the equator).

Forests

Tropical rainforest

Temperate deciduous and coniferous

forest

Why different types of natural

vegetation exist in different parts

of the Earth?

Temperature affects vegetation because if it is

too cold (less than 6°C), few plants can grow. On

the other hand, warm temperatures (above 20°C)

allow abundant plant growth



of the Earth?

Precipitation (rainfall) also affect vegetation

because all plants require water to grow.

Most trees require more water to grow than

grass.



of the Earth?

Hence, most forests grow in areas with high

rainfall (above 1000 mm a year).

In areas with moderate precipitation of between

200 mm and 1000 mm, grasslands are more

common.

In areas with less than 200 mm of rain, deserts are

found.

Climate – Vegetation

Relationship

In summary:

Natural vegetation is influenced mainly by climate

A climate-vegetation relationship exists because

rainfall and temperature determine the type of

natural vegetation found in a place

High rainfall - forests

Moderate rainfall - grasslands

Low rainfall - desert vegetation

Climate – Vegetation

Relationship

In summary:

Climate is a major factor that influences the

distribution of natural vegetation.

Other factors like the type of soil and altitude can

also affect its distribution.

Forests

Forests refer to large areas of land that consist

mainly of trees and a variety of other plants

They are usually found:

Distribution Climate

Temperature oC

Rainfall (mm)

Between latitudes of

66.5oS and 66.5

oN

-12 to 30 300 mm to 2000 mm

Tropical Rainforests

You will learn:

where are tropical rainforests found

what are the characteristics of a tropical

rainforest

a) The different layers of a tropical rainforest

b) The different types of plants found in the

different layers

c) At least one of the adaptations of the tropical

rainforest

Location of Tropical Rainforests

Distribution Climate Location

Temperature oC

Rainfall

(mm)

Between

latitudes of

23.5o N and

23.5.oS of the

Equator which

has a tropical

climate

High

Between

20 to 30

High

1000

mm to

2000

mm

• Amazon Basin in

South America,

• Malaysia and

Indonesia in

Southeast Asia,

• the Congo Basin

in Africa

Tropical Rainforests

Characteristics of Tropical Rainforests

1. Trees grow very close to each other, making the

forest very dense.

2. Plants grow in 3 distinct layers.

• Emergent

• Canopy

• Undergrowth

The THREE LAYERS

Undergrowth


EMERGENT LAYER

• Reach heights of 40 to 50 metres

• Grow to receive more sunlight.

• Often have buttress roots to support the

tall and heavy trunks.

CANOPY LAYER

• Reach about 15 to 30 metres

• Crowns of trees interlock to form

continuous leaf cover (canopy)

• Cool and moist interior – blocks out

70% of sunlight

• Lianas are common – woody climbing

plants that hang down.

• Epiphytes are common – plants that

grow on other trees to get more sunlight


EMERGENT LAYER

CANOPY LAYER

} UNDERGROWTH

• Made up of shrubs, grasses,

ferns, mosses and fungi.

• Plant growth is sparse

because of the lack of sunlight


• Some plants, called epiphytes overcome the shortage of sunlight by growing high up on tree branches to get sunlight (examples: ferns, orchids).

• Other plants, known as lianas, grow upwards to get more sunlight by winding around tree trunks.

Adaptation??

Tropical rainforests: Leaves

Tropical forest trees are evergreens as the

leaves remain green throughout the year.

This is unlike deciduous trees, which shed

their leaves in the autumn or in the dry

seasons.

The leaves are also broad to absorb as much as

much sunlight as possible.

They are also waxy and have drip tips to allow

water to drain off.

Tropical rainforests: Leaves

The bark of trees in the tropical rainforest is

thin because they are not required to protect

the trees from dry or cold conditions.

Branches are also located in the top one-

third portion of the trunks and they are

shaped like umbrellas to capture as much

sunlight as possible.

Tropical rainforests: Roots

Roots of tropical forest trees are shallow because they do not need to reach deep into the soil for water.

This also allows the roots to tap the abundant nutrients found in the layer of leaf litter of on the ground.

Some of the tallest trees have buttress roots to support their great weight and prevent them from falling over.

Tree roots near the surface, Malaysia

The Shrinking Rainforests

The world loses about 100 000 sq km of rainforests each year

Forests are cleared for growing crops and building houses and roads, and logged every day

We must do our part to save the remaining rainforests

The Shrinking Rainforests

Impacts of deforestation:

Flooding

Landslide due to soil erosion

Loss of biodiversity of plants and animals

Decrease in oxygen and increase in carbon dioxide

Temperate Coniferous Forests

CLIMATE AND DISTRIBUTION

Distribution Climate Location

Temperature oC

Rainfall

(mm)

Only

between

latitudes of

23.5o N and

66.5.o N of

the Equator

-12 to 10 300mm to

750mm

• Japan

• China

• Europe

• North

America


CHARACTERISITICS

1.Cone Shaped tree (think Christmas Tree!)

• Allows snow to slide off the

tree branches easily.

• Prevents increase weight of

the snow on the branches

which can cause them to

break.


CHARACTERISITICS

2. Trees are evergreen

• They adapt to extreme conditions instead of

shedding their leaves.

3. Forests have only one variety of tree in each

area. Example: Pine, Fir, Spruce

4. Only have one layer of vegetation

5. Very little undergrowth except for moss,

lichen and leaf litter on the forest floor.

Features and Adaptation - Trees

• Coniferous trees are cone-shaped and have

sloping and supple (easily bendable)

branches to allow snow to slide down without

snapping branches

Features and Adaptation - Leaves

• The leaves are

small, needle-

shaped, waxy &

leathery to:

• Minimise water

loss

• Prevent the

accumulation of

snow

Features and Adaptation – Barks

• Barks are

rough, tough &

contains resin

(thick, sticky

liquid) to protect

against cold and

to conserve

moisture

Features and Adaptation – Roots

Features and Adaptation – Roots

• Coniferous trees have shallow spreading roots which enable them to absorb water from the surface during the short warm months.

• Roots do not go deep as the ground there may be permanently frozen, even during the summer.

Quiz Time:

• State one difference and one similarity in the characteristics of the natural vegetation found in a Tropical Rainforest and a Temperate Coniferous forest.

• Explain how these characteristics help the plants to adapt to the living conditions in which they are found.

BENEFITS OF FORESTS

You will learn:

what are some of the benefits of the

natural vegetation to the Earth and

humans.

BENEFITS OF FORESTS

Oxygen in the atmosphere:

• Plants play an important role in

maintaining the amount of oxygen in the air

Formation of rain:

• Plants add to the amount of water vapour in

the air through transpiration and hence

rainfall is usually high in places populated

by many plants

BENEFITS OF FORESTS

Natural resource:

• The hardwood trees in

rainforests provide wood

required to make things like

furniture and houses

Medicinal value:

• Many plants that grow in

tropical rainforests have

medicinal properties

BENEFITS OF FORESTS

Recreation:

A place where nature lovers can relax

BENEFITS OF FORESTS

Natural habitats:

• Loss of natural vegetation will result in

the loss of food and habitat for animals

Prevents erosion of soil

• Plants can prevent soil erosion

Case Study:

Bukit Timah Nature Reserve

In Singapore, only a few small areas of

rainforests are left.

The government has set aside areas covered

by rainforests as Nature Reserves are part of

conservation efforts.

• Bukit Timah Nature Reserve is 164

hectares in size.

• Believed to be only 0.2% of the rainforest

originally in Singapore.

• Last 1% of primary rainforest in Singapore.

Case Study:


CHARACTERISTICS OF BUKIT TIMAH NATURE RESERVE

1. Tall trees (+30m) due to hot and wet climate

2. Trees have buttress roots to support themselves

3. Trees are evergreen and grow closely together.

4. Crowns interlock to form canopy that

prevents sunlight from reaching the forest floor.

5. Dark and damp forest floor.

6. Wide variety of trees and other plants.

• Different hardwood trees: seraya, meranti and nemusi

• Species of climbing palms: rattan

Case Study:


VALUE OF TROPICAL RAINFORESTS

1.Medicinal Properties

2.Water Catchment areas

• When rain falls, the rainwater is trapped by

the leaves and falls to the ground. The

water will drain slowly into the ground and

eventually into nearby reservoirs.

Case Study:


VALUE OF TROPICAL RAINFORESTS

3. Recreational Activities

• Such as trekking and jogging

4. National Heritage

• Part of our history and our national

heritage.

• Singapore is on of the only two cities to

have a sizeable amount of rainforest in a

built up area.

chapter 12 natural vegetation

Education