Where is the tropical rainforest biome mainly located?
Latitudes 10N and 10S of the equator. Amazon basin - South America. Democratic Republic of Congo. Guinea coast of Africa. Parts of southeast Asia, Indonesia and northern Australia.
What is the temperature generally like within an equatorial tropical rainforest biome?
Little seasonal variation.
High throughout the year.
Mean monthly values - 25C.
Don’t exceed 28C.
When do dual peak temperatures occur?
Annually.
Sun directly overhead twice a year.
Tropic of Cancer moves to the Tropic of Capricorn between the summer and winter solstices.
Daily (diurnal) temp. range higher than average.
What are/is temperatures/precipitation like in a tropical rainforest biome further away from the equator?
Day - sunny spells - 30C.
Night - clear sky - below 20C (no insulation to keep the heat in).
2,000mm rainfall - high.
Why does rain fall all year round at the equator?
ITCZ dominating atmospheric conditions.
Low-pressure belt
What is precipitation like further away from the equator?
Short dry season - annual ICTZ movement.
Travels between the Tropics of Cancer and Capricorn.
May-July: dry season in the southern hemisphere.
ICTZ directly over the Tropic of Cancer.
Pulls with it wet low-pressure weather into the northern hemisphere.
Opposite occurs in November-January.
What is the daily pattern of rainfall like within a tropical rainforest biome?
Morning - clear skies. Rapid evapotranspiration. Low-pressure conditions - rapidly uplifted air. Air cools - water vapor condenses into clouds. Early afternoon - cloud build up. Comulonimbus kind - dense grey colour. Late afternoon - heavy rain/thunder. Repeated cycle.
What is humidity like within a tropical rainforest biome?
High.
Continuous evapotranspiration adds water vapor to the air.
What is time like within a tropical rainforest biome?
Days and night are the same length at the equator.
Dawn arrives at 6am.
Night falls quickly at 6pm.
Little twilight.
12 hours of daily sunlight - photosynthesis takes place all year round.
What is wind like within a tropical rainforest biome?
Forest floor - little breeze.
Equator - distinct lack of breeze - trade winds converge.
What is a zonal soil and what zonal soil type is associated with a tropical rainforest biome?
Found in undisturbed areas.
Underlying soil - developed naturally over long time period.
Mature soil.
Characteristics reflect climate and vegetation.
Latosol TFR soil type.
What are the characteristics of a latosol?
40m deep.
Ferrrallisation.
Red colour - iron and aluminium minerals.
Moisture surplus - water downward movement.
Silica minerals leached out of A.
Iron/aluminium minerals - soluble - left behind - redder further down.
Poor nutrient intake.
What is ferrallitisation?
Bedrock broken down by chemical weathering into clay minerals and sesquioxides.
Climate helps.
Why are the nutrient levels of a latosol poor?
Plant nutrient uptake equal to decomposed litter.
All-round growing season ensures organic matter is absorbed by growing vegetation straight away.
What are the A/E (top) layers of a latosol?
Light pink.
Thick debris is rapidly broken down.
What is the Bs (middle/top) layer of a latosol?
Dark red.
Many soil organisms active.
Iron and aluminium oxides.
What are the B/C (bottom) layers of a latosol?
B - Lighter red. Dissolved salts leached. C - Yellowish. Silica redeposited. Weathered bedrock. Parent material.
What are undisturbed bits of the TRF called/characteristics?
Most diverse/productive world biome - most fragile.
Untouched remote parts - state of dynamic equilibrium.
Dominant tree species - hardwood trees.
This balance can easily be disturbed by human activity.
What are the vegetation characteristics of a TRF? FIRST THREE
- NPP - 2,000gm-2 yr-1.
- Evergreen appearance - despite most being deciduous, leaves lost at different times.
Some always in full leaf. - 300 tree species every square km e.g. teak, rosewood, rubber and Brazil nut.
What are the vegetation characteristics of a TRF? SECOND THREE
- Layered appearance. Emergents (tallest) - 45m.
Absorbs most sunlight/intercepts most. - Tree dies - fall brings down others - small clearing. New trees grow quickly - light advantage.
Fallen trees decompose rapidly - detritivores, hot/humid conditions. - Fungi grows on trees/forest floor - decomposing litter.
How has TRF vegetation been adapted? 1/2
Tree characteristics
- Rapid tree growth towards the light.
Slender trunks, few branches.
Leaves at top - photosynthesise.
Thin bark - don’t need winter protection.
Tallest trees - flexible trunks - allow movement.
50m - strong winds - allows sway without breaking. - Abundant supply of water - minerals only in top soil layer.
Shallow, spread out roots.
Buttress roots - 3m above ground - stabilises tallest trees.
How has TRF vegetation been adapted? 2/2
Leaf/plant type
- Leaves - drip-tips - excess water easily shed.
Thick, waxy leaves - strong sunlight - reduces water loss. - Dark forest floor - some tree plants - epiphytes.
E.g. Lianas.
What is deforestation?
+ FAMOUS EXAMPLE.
Deliberate clearance of woodland by cutting, burning or the application of a defoliant.
1960s by the US troops in Vietnam.
Where is deforestation occurring the most?
Developing countries/NICS e.g. Amazon basin.
Claims 50% world’s TRFs already been cleared.
Continued - Brazil/Dem. Republic of Congo - only ones left with significant TFRs.
What has the destruction of climatic climax vegetation in a TRF resulted in?
Secondary succession and plagioclimax.
Replaced vegetation - smaller/less diverse.
Biomass reduction.
What are the causes of deforestation? 2
- Demand for hardwood e.g. teak, for buildings/furniture. Timber export earnings - pays debts/finances major development projects.
- Land - cattle ranching, mining.
Dammed rivers/large areas flooded - water for hydroelectric stations.
E.g. Brazil - vast sources of aluminium/iron ores.
Carajas mining project in Amazonia.
Why does deforestation occur regarding population pressure?
1960s/70s - Southeast Asia and South America. Increased rapidly as BR exceeded DR.
Population pressure - demand for land.
E.g. Indonesian transmigration - movement from overcrowded Java to less populated Sumatra - land cleared.
What are the environmental impacts of deforestation? 3
- Habitats shrink, plants endangered, threatened food chains, extinction e.g. tigers.
- Vegetation protects latosol soils rainfall - more leaching, soil erosion/flooding.
- Disturbed microclimate - daily rapid evotranspiration then afternoon precipitation can’t occur - less cloud cover - greater temperature change.
Forest clearance burning - local air pollution - contributes to climate change.
What are the social impacts of deforestation?
Destroyed indigenous culture.
Forced to move land.
What is the economic impact of deforestation?
Economic income benefits from mining, farming and exports of hardwood.
