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Earth: Our Home
Full Geography
Chapter 9
Types
of
Natural Vegetation
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You will learn:
to describe the global distribution of
different types of forests
to describe the characteristics of differenttypes of forests
to compare the ways in which differenttypes of forests adapt to the environment
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What is Natural Vegetation?
Natural vegetation refers to plants that
grow naturally in a place with little or nohuman interference.
It plays an important role in a forestecosystem by providing food and shelterfor the animals and native people that live
in the forest.
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Major types of natural vegetation
Tropical rainforestTemperate
deciduous forest
Coniferous forest
Grassland biome
Grasses constitute the main plants in a grassland
biome. It has few varieties of plants.
Tropical grassland Temperate grassland
Desert biome
The vegetation in a desert biome consists of mainly sparse vegetation, such as scrubs and tough grasses in the hot desert,
and mosses and lichens in the cold desert. It has very few varieties of plants.
Hot desert vegetationCold desertvegetation (tundra)
Forest biome
The vegetation in a forest biome consists of mainly trees. It generally has many varieties of plants.
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Distribution of NaturalVegetation
Climate is a major factor in influencing the
distribution of natural vegetation.
There are 3 climatic types..
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Distribution of Natural
Vegetation
Very low temperatures, often below 0C. Very low annual precipitation,below 250 mm
Low to modern temperatures, ranging from 0C to 34C,
depending on the season. Moderate annual precipitation,
300 mm to 1 000 mm
High temperatures throughout the year, 20C to 30C.
High precipitation, above 1 000 mm
Temperate region
Polar region
Tropical region
Tropical region
Temperate region
Polar region
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Distribution of NaturalVegetation
Temperature and precipitation can
influence plant growth.
Plant growth is more abundant in areaswhere temperatures are consistentlyabove 20C than in areas wheretemperatures fall below 6C.
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Distribution of NaturalVegetation
Water is required by plants to make food.
Thus, different types of natural vegetationforests are found in different parts of the world.
- forests --- high precipitation at above1 000 mm per year.
- grasslands --- moderate precipitation
between 200 mm to 1 000 mm per year.
- hot desert vegetation or tundra --- no or
little precipitation at less than 250 mm per
year.
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Distribution of NaturalVegetation
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Tropical forests are a cradle of biodiversity. It hasbeen estimated that half of the plant and animal lifeforms that live on this planet are found in thisenvironment, even though tropical forests coveronly six percent of the earths surface.Source: The Tropical Rainforest by Francesco Petretti, Journey Editions, 1998, Italy.
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Tropical Rainforest
Tropical rainforests- found in places that experience the
tropical equatorial climate
- high temperatures, about 27
C- high amount of rainfall, above 1 500 mm
throughout the year
- examples of tropical rainforests include
the Amazon Basin in South America,
Congo Basin in Africa and parts of
Southeast Asia
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Tropical Rainforest
Structure of the forest
- 5 layers:- Emergent layer, 30 m to 50 m
- Canopy layer, 15 m to 30 m- Understorey layer, 6 m to 15 m
- Shrub layer, grow up to 6 m
- Undergrowth layer, grow up to5 m
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Tropical RainforestEmergent layer 50 m
Tall trees, called emergents, reach a height of 30 m
to 50 m. Their crowns appear above the canopy
layer. These trees have tall, thick and straight trunks.
30 m
Canopy layer
The trees in this layer reach a height of 15 m to 30
m. Their wide, shallow and umbrella-shaped crowns
form a continuous leaf cover, called a canopy, as
they prevent sunlight from penetrating into the lower
layers of the forest. 15 m
Understorey layer
The trees here have narrower, oval-shaped crownsbecause most of the sunlight is blocked by the
canopy. These trees grow where gaps in the canopy
allow sunlight to pass through. Their heights range
from 6 m to 15 m. Young trees of the emergent and
canopy layers are also found in this layer.
6 m
Shrub layer
Tree saplings and woody plants are found in this
layer. They may grow up to 6 m high.
5 m
Undergrowth layer
The undergrowth or forest floor is made up of
grasses, ferns, mosses and fungi. Plant growth is
sparse because very little sunlight reaches this layer.
Plants in this layer reach a maximum height of 5 m.
0 m
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Tropical Rainforest Characteristics of the 5 layers
Emergent layer
- trees have tall, thick and straight trunksCanopy layer- tree crowns inter-lock
- presence of epiphytes and lianas, and parasitic plantsUnderstorey layer- trees with narrower crowns- presence of parasitic plants
Shrub layer- tree saplings and woody plants foundUndergrowth layer- sparse due to lack of sunlight that reaches the forest
floor
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Tropical Rainforest Characteristics
- a wide diversity of plant species
- 750 species of trees and 1 500 species of other plants
in 1 hectare
- the high temperature and rainfall throughout the year
enables it to support a large variety of plants
Density
- extremely dense
- density is due to high temperature and rainfall that
encourage abundant vegetation growth
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Tropical Rainforest
Characteristicsand AdaptationsLeaves
- are evergreens
- due to high rainfall throughout theyear, trees do not shed leaves at the
same time
- are waxy with drip tips
- to allow rainwater to drain off easily
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Tropical Rainforest
Characteristics and Adaptations
Flowers and fruits
- are colourful and sweet-smelling- to attract insects for pollination and
animals for seed dispersal
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Quick Quiz
Can you identify theflower?
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Quick Quiz
It is a type of Rafflesia, a spectacular plant
found in the tropical rainforest.
There are 15 to 19 species of Rafflesia.
Rafflesia is known to produce the largestindividual flower on the Earth.
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Tropical rainforest
Characteristics and AdaptationsBark and branches- thin and smooth branches- does not need protection against cold or dry conditions
- branches are found at the uppermost one-third of thetrunks to get as much sunlight as possible
Roots
- shallow and spreading- nutrients are found at topsoil due to high decomposition- buttress roots (of some tall trees)- support weight of trees
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Tropical Monsoon Forest
Tropical monsoon forest- found in the tropics
- high temperatures, about 26C
- high amount of rainfall, above 1 500 mm
throughout the year, but with distinct wet
and dry seasons
- located in South Asia, Southeast
Asia,southern China and northern
Australia
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Tropical Monsoon Forest
Distribution
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Tropical Monsoon Forest
Structure of the forest
3 layers: - Canopy layer, 25 m to 30 m
- Understorey layer, about 15 m- Undergrowth layer
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Tropical Monsoon Forest30 m
Canopy layer
Trees can grow to 25 to 30 m
in height. They are more
spread out than those in a
tropical rainforests, plants such
as creepers, vines, epiphytes
and parasitic plants are found
within this layer.
15 m
Understorey layer
The trees in the understorey
are about 15 m in height.
6 m
Undergrowth
Bamboo thickets and grasses
grow densely here during the
wet season. They are
dense during the dry season.
0 m
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Tropical Monsoon Forest
Characteristics of the 3 layers
Canopy layer
- more spread out than those in tropical rainforest
- presence of epiphytes and lianas, and parasitic plantsUnderstorey layer
- consists of shorter trees about 15 m in height
Undergrowth
- bamboo thickets and grasses grow densely hereduring the wet season but are less dense during dryseason
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Tropical Monsoon Forest
CharacteristicsDiversity of plant species- about 200 species in 1 hectare
- less species compared to tropical rainforestdue to inconsistent rainfall
Density
- plant growth is abundant but less dense thantropical rainforest
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Tropical Monsoon Forest
Characteristics & Adaptations
Leaves
- are deciduous
- shed leaves during the dry season to minimise
loss of water through transpiration
- waxy with drip tips to allow rainwater to drain
off easily
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Tropical Monsoon Forest
Characteristics & Adaptations
Bark and branches
- thick and coarse
- protects the trunk from heat and drynessduring the dry season
- withstand extreme heat from natural forest
fires
- branches found around middle of trunks as
trees grow less dense than tropical rainforest
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Tropical Monsoon Forest
Characteristics & Adaptations
Roots
- deep tap roots- to tap water sources deep under the
ground as rainfall is irregular throughout
the year
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Tropical forests in a glance
What are the similarities between the
tropical rainforest and the tropicalmonsoon forest?
What are the differences?
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Tropical forests in a glance
Similarities
- both forests are dense
- leaves are waxy with drip-tips
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Tropical forests in a glance
Differencesdiversity
density
leaves
bark &
branches
roots
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Answers
Tropical rainforest Differences in
terms of
Tropical
monsoonforest
more diversity less
denser density less denseevergreen leaves deciduous
Smooth, thin bark
Branches at top one-third
bark &
branches
Thick bark
Branches aroundmiddle of tree
shallow roots deep tap roots
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Mangrove forests Found mainly in areas experiencing
tropical climate, along sheltered coastal
regions and places where rivers constantlydeposit clay and silt.
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Mangrove Forests
Structure- grows to a height of 2 m to 40 m
- horizontal zones of mangrove species
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Mangrove Forests
Coastal area
Avicennia and Sonneratiatrees are
common in this zone, which is the
nearest to the coast. They have adapted
to growing in salt water, as the coastal
zone is flooded with seawater during
high tide. The trees have breathing
roots or aerial roots.
Middle zone
Rhizophoratrees are common in this
zone. They have prop roots or stilt roots.
Inland zone
Bruguiera trees grow further inland, as
they are the least tolerant of salt water.
They have knee-like roots.
Low tide
High tide
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Mangrove Forests
Characteristics and Adaptations- four main species which are known ashalophytes- Avicennia, Sonneratia, Rhizophora, Bruguiera
- dense and luxuriant
Leaves- evergreen- salt secretors- ultrafiltrators
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Mangrove Forests Characteristics and Adaptations
Flowers
- generally colourful to attract insects to pollinate
Fruits
- buoyant so that waves and currents can carry themaway
- elongated with sharp tips to anchor in soft muddy soil
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Mangrove Forests
Characteristics and Adaptations
Roots
- aerial roots that are exposed- allow them to take in oxygen
- prop roots
- anchor the trees firmly in the muddy soil
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Coniferous Forests
Coniferous forest
- found in places that experience a cool
continental climate
- experiences seasons- temperatures range from -40C to 21C
- low amount of precipitation, usually in the form
of snow, 300 mm to 635 mm in a year- located in Alaska, northern Canada, northern
USA, northern Scandinavia and Russia
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Distribution
Coniferous Forests
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Coniferous Forest
Structure
- no distinct layers
- generally uniform in height, about 20 mto 30 m
- trees grow close together
- little undergrowth
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Coniferous forests
Characteristics and AdaptationsDiversity
- few species as not many trees can adapt to
the climate- the trees grow in pure stands
Density
- forest are not dense as the climate does notsupport dense vegetation growth
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Coniferous Forest
CharacteristicsLeaves- evergreen- retain leaves so that photosynthesis can takeplace whenever temperature rises above 6C
- needle-like with small surface area to reducewater loss due to transpiration
- store water for use in winter
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Coniferous Forest
Characteristics and Adaptations
Flowers and Fruits
- trees bear female and male cones
- female cones produce seeds
- male cones produce pollen
- cones can be dispersed by wind or
animals after pollination
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Coniferous forest
Characteristics and AdaptationsBark and branches- thick bark- to protect from long, cold winters- flexible branches that slope downwards- to enable snow to slide off easilyRoots
- shallow, spreading roots- enable trees to absorb water easily from soilsurface when snow melts
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Importance of Forests
Support diversity of plants and animals.
Natural habitats for animals.
Provide us with resources.
Home to some natives.
Part of our natural heritage.
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Learning Outcomes
Global distribution of tropical rainforests,tropical monsoon forests, mangroves andconiferous forests.Characteristics and adaptations of tropicalrainforests, tropical monsoon forests,mangroves and coniferous forests.Skills
-Compare and contrast the characteristicsof different forests.