Geography
Revision
Tropical equatorial climate
- 10 ° north and south of the equator
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Temperature: High temperature, 27°C
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Very small annual temperature range: 2°C
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Rainfall: High rainfall of about 3000 millimetres per year (no distinct wet or dry
seasons)
Tropical monsoon climate:
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10° and 25° North and South
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Temperature: High temperature, 26°C
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Small temperature range: 6°C
- Rainfall: High rainfall of about 3000 millimetres per year (distinct wet and dry seasons)
Cool temperate climate
- 35° and 70°N and S of the Equator
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NEAR THE COAST: Temperature: 15°C - 30°C
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INLAND: Winter temperatures are below the freezing point
o Inland places at higher latitudes also experience brief summers and cool
temperatures as the Sun’s rays are spread over a larger area
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Annual temperature range is large at 20°C
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Precipitation: Low or moderate 300 – 2000 millimetres
Explain how climate impacts people
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Melting ice and rising sea levels
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Glaciers are retreating and the amount of ice cover has decreased in the
polar regions
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This has caused sea levels to rise and low-lying coastal countries are
especially vulnerable to rising sea levels.
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The lives and property of an estimated 100 million people who live on land
within one metre above sea level are threatened by the possibility of flooding.
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Severe storms
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Tropical storms form when the surface of the ocean is heated above 27°C
and the warm air above the ocean rises rapidly and cool air spirals in
(hurricane)
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Flooding and destruction of homes, industries (economic – tourism) and
infrastructure.
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Heat waves and droughts
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When the water bodies have dried up, there will be less water vapour in the
atmosphere  less clouds  little rain
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Causes forest fires  destruction of the environment and deaths
o
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Different kinds of forests
1. Tropical Rainforests
a. 5 layers: Emergent, Canopy, Understorey, Shrub, Undergrowth
i. Emergent: Tall, thick, straight trunks
ii. Canopy: Wide, shallow, umbrella-shaped crowns form a continuous
leaf cover
iii. Narrower, oval-shaped crowns, these trees grow where gaps in the
canopy allow sunlight to pass through.
iv. Shrub layer: tree saplings and woody plants
v. Undergrowth layer: Grasses, ferns, mosses and fungi (SPARSE)
2. Epiphytes
a. Grow on tree branches for support to get more sunlight
b. Rainwater and decaying leaves collect at the joints of branches provide water
and nutrients.
c. Bird’s Nest Fern and orchids
d. Not parasitic
3. Lianas
a. Thick woody vines that wind around tree trunks
b. Not parasitic
4. Parasitic plants
a. For example, strangling fig wraps itself around the trunk of the host tree and
compete with the host tree for space, sunlight and nutrients
Characteristics of a tropical rainforests
- Diversity of plant species
o High year-round temperature and rainfall
o One hectare may contain more than 750 species of trees and 1500 species of
other plants
- Density
o High temp. and rainfall encourage the dense and abundant vegetation
growth
- Leaves
o Evergreen: do not shed their leaves at the same time in the year
o Large and broad to maximize the surface area for photosynthesis.
o Waxy with drip tips to drain off rainwater to prevent bacteria growth as
rainfall promotes the rapid growth of bacteria.
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1.
o When they reach the canopy new leaves will be smaller. The large leaf
surface helps intercept light in the sun-dappled lower strata of the forest.
Flowers and fruits
o Produce fruits throughout the year
o The still air below the canopy layer does not allow pollination to be carried
out by wind  Colourful and sweet-smelling to attract insects for pollination
and animals for seed dispersal.
Bark and branches
o Thin and Smooth barks
o Very little sunlight passes through canopy  Branches only on the top onethird portion of the trunks and spread out like umbrellas
Roots
o Shallow and spread widely because need not reach deep for water and
nutrients
o Buttress roots: thick and spread out to support the great weight
 Originally believed to help support the tree, now it is believed that the
buttresses channel stem flow and its dissolved nutrients to the roots.
o High temp. and rainfall all year round cause humus to form rapidly, supplying
nutrients to the topsoil.
Tropical monsoon forests
a. High temperatures and rainfall (over 1500 millimetres per year) but with
distinct wet and dry seasons.
b. 10-25 Degrees North and South of the Equator
2. Structure of forest
a. Three vertical layers
(The lack of water during dry seasons does not allow trees to grow to great
heights)
b. Canopy layer
i. More spread out
c. Understorey layer
d. Undergrowth
i. Dense during wet season and less dense during the dry season
Characteristic of Tropical Monsoon Forest
- Diversity of plant species
o 200 species of plants can be found in one hectare
o Hardwoods and are commercially valuable(to developed countries like USA,
France, Japan) species like teak, sandalwood and sal.
- Density
o Crowns do not interlock to form a continuous canopy
- Leaves
o Deciduous: shed leaves during dry season to minimise loss of water through
transpiration during the rainy season.
o Waxy with drip tips
- Flowers and fruits
o Many flower and bear fruit during the wet season when they are leafless.
- Bark and Branches
o Thick and coarse bark prevent the trunk from heat and dryness during dry
season or forest fires
o Branches located near the middle.
o Sunlight is able to reach the lower parts of the forest
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Bark and Branches
o Thick and coarse bark prevent the trunk from heat and dryness during dry
season or forest fires
o Branches located near the middle.
o Sunlight is able to read bottom of the forest.
Mangrove forests
1. Sheltered coastal regions and places where constantly rivers constantly deposit clay
and silt.
a. 2 metres to 40 metres as the muddy soil cannot provide firm support
2. Structure of forest
a. Three distinct horizontal layers
b. Coastal Zone – Avicennia and Sonneratia (Breathing roots of aerial roots)
c. Middle zone – Rhizophora (Prop roots or stilt roots)
d. Inland Zone – Bruguiera trees, least tolerant (Knee-like roots)
3. According to the Environmental Justice Foundation, about 38 percent of global mangrove
deforestation is linked to shrimp farm development.
Characteristics of Mangrove Forests
- Diversity of plant species
o Adapted to grow in salt water  Halophytes
o Sea hibiscus and Nipah palm
- Density
o Dense and luxuriant due to high temperatures and rainfall
o Continuous canopy, sparse undergrowth
- Leaves
o Evergreen: No seasonal changes
o Broad and have drip tips
o Due to high temperature, they are thick and leathery to reduce water loss
through transpiration
o Salt secretors: E.g. Avicennia  Secrete excess salt on leaves which are
removed by rain or wind
o Ultrafiltrators: E.g. Bruguiera, Rhizophora, Sonneratia absorb salt and remove
the excess salt by storing it in old leaves which fall off.
- Flowers and fruits
o Colourful to attract insects to pollinate
o Fruits of Avicennia are buoyant so waves and currents can carry them away
o Fruits of Rhizophora germinate and grow while still attached to the parent
tree and drop directly into the ground to take root (sharp tips to anchor into
muddy soil)
- Roots
o Waterlogged soil  Lacks oxygen
o At low tide, the aerial roots are exposed
o Some roots have salt filters
Coniferous forests
o No distinct layers, uniform
o Little undergrowth, little sunlight and soil nutrient level
 Leaf litter made up of tough needles which do not break down easily
o Few species
o Grow in pure stands: single species grow in an area of coniferous forest
o Evergreens: needle-like leaves reduce water loss and also store water for use
in winter
o Female cones produce seeds while the male cones produce pollen.
o Thick barks
 Sugar content increase in winter to allow greater absorption of water
through osmosis
 Resin prevents freezing of moisture in tree cells
o Flexible branches to prevent accumulation of snow
o Conical shape help withstand strong winds rather than topple over
o Soils are thin or subsoil is frozen much of the year
o Cold boulder clay soil discourages deep root penetration
o Female cones produce seeds, male cones produce pollen.
o Shallow, spreading roots to absorb water from melted snow.
Uses of Forests
1. Maintaining water supply
a. They enable water to be collected and stored within a water catchment.
b. Quality of water in forested areas
i. Vegetation transpires  Water vapour  Encourages cloud
formation  Rain replenishes the water in rivers and reservoirs.
ii. Leaves and branches intercept and increase the impact of water
falling  More water will seep into the ground  stored as
groundwater which flows into nearby rivers and reservoirs
iii. Filter water
- Less water flowing over ground surface  less soil particles
washed into rivers and reservoirs
- Soil also traps impurities in rainwater and filters it (trapping
them between pore spaces)
2. Replenishing oxygen and removing carbon dioxide
3. Maintaining nutrients in the soil
a. Decomposing vegetation  releases nutrients back into soil
b. Roots hold soil particles together to prevent nutrients from being removed by
soil erosion
4. Preventing floods
5. Natural treatment of waste water
a. Roots of mangrove help trap waste materials
b. The soil in mangrove forests contains bacteria that can break down the
biodegradable wastes and convert them into nutrients for the mangroves
6. Mangroves form a buffer or protection zone between coastal settlements and the
sea, protecting them against storms and strong waves.
7. Habitat for flora and fauna
8. A source of useful materials
a. Forests are a renewable resource.
b. Sustainable development: Forests should be used at a rate in which they
meet the needs of the present generation, without affecting the ability of
future generations to meet their own needs.
9. Fuelwood and Charcoal
10. Food
11. Medicines
12. Chemicals
13. Habitat for people
a. Native tribal people
14. Recreation
15. Research and Education
a. Conducting scientific research to develop new medicines and new varieties of
crops
b. Studying the interactions between forest animals and plants with the
environment