The Living World: Tropical Rainforests Flashcards
Characteristics of biomes: TROPICAL RAINFOREST
- Found near the equator
- Hot and humid (equatorial) with heavy rainfall
- Covers 6% of the earth’s land surface
- Contains around half of all the world’s species
- A quarter of all medicines come from rainforest plants
Layers of the tropical forest: SHRUB LAYER
- Near forest floor and extremely dense
- Dark and gloomy with little vegetation between the trees
- Can flood during heavy rainfalls
Layers of the tropical forest: UNDER CANOPY
- Limited sunlight
- Saplings wait here for larger plants and trees to die and leave a gap in the canopy which they can grow into
- Lianas can climb up trees to get sunlight
Layers of the tropical forest: CANOPY
- Where upper parts of most trees are found
- Typically 20-40 metres tall
- Home to about 50% of rainforest (insects, birds, some mammals)
Layers of the tropical forest: EMERGENTS
- Tops of tallest trees in rainforest
- Much higher, so able to get more light then average trees in canopy
- Layer can grow in excess of 50 metres
Environmental characteristics of tropical rainforests
-CLIMATE
- Thrive in warm and wet conditions
- Equatorial zone characterised by high rainfall and temp throughout the year*
- (Climate generally stays same with only some dryer and wetter months)
Environmental characteristics of tropical rainforests
-PLANTS AND ANIMALS
- Provides habitats for over half all plant and animal species on the planet
- Birds live in the canopy feeding on nectar from flowers
- Mammals (monkeys, sloths) are well adapted to living in trees
- Animals (deer, rodents) live on forest floor
Environmental characteristics of tropical rainforests
-SOILS
-Mostly infertile
-Most nutrients found at surface, where dead leaves decompose rapidly in the hot and humid conditions
-Many trees and plants have shallow roots to absorb these nutrients
-Fungi growing on roots transfer nutrients straight from air (nutrient cycling)
-Heavy rainfall can quickly dissolve and carry away nutrients (leaching)
-This leaves behind an infertile, red, iron-rich soil (latsol)
-
Environmental characteristics of tropical rainforests
-PLANT AND ANIMAL ADAPTATIONS
- Majority of plant and animal species found in canopy, where there is the most light
- Biotic factors have a close relationship with abiotic factors: small changes to either factors (e.g. deforestation, water pollution) can have serious knock-on effects on the entire ecosystem
ADAPTATION: Lianas
Woody creepers rooted to the ground but carried by trees into the canopy where there is more sunlight
ADAPTATION: Buttress roots
Massive ridges to help support bases of tall trees and help transport water
May also help O2/CO2 exchange by increasing surface area
ADAPTATION: Leaves with flexible bases
Flexibility in base helps leaves turn to face the sun
ADAPTATION: Thin smooth bark
Allows water to flow down tree easily and stops other plants from growing on tree surfaces
ADAPTATION: Epiphytes
Plants which live on trunks and branches of other plants, allowing them to make the most of the sunlight in the canopy
ADAPTATION: Emergent
Fast-growing trees (e.g. Capoc) out-compete other trees to reach sunlight
ADAPTATION: Drip-tip
Allows heavy rain to drip off leaf. This prevents algae growing which could block sunlight and stop photosynthesis
Nutrient cycle:
1) Trees shed leaves all year round
2) Decaying vegetation decomposes rapidly releasing nutrients
3) Nutrients enter the soil surface but don’t get the chance to sink in
4) Shallow roots quickly take up the nutrients
5) The nutrients help the tree grow rapidly
* repeat*
Deforestation
The cutting down of trees on a very large scale, often to make profit
Deforestation in the Amazon for resource exploitation
-LOGGING
- Timber companies are interested in selectively logging mahogany and teak because they can be sold to other countries to make furniture
- Smaller trees are used for fuel or made into pulp or charcoal
Deforestation in the Amazon for resource exploitation
-MINERAL EXTRACTION
- Most of the mining is for gold
- In 1999 there was 10,000 hectares of land being used for gold mining
- Today, the area is over 50,000 hectares
Deforestation in the Amazon for resource exploitation
-ENERGY DEVELOPMENT
- Hydro-electric power is an ideal energy source due to the unlimited supply of water and ideal river conditions for HEP dams
- Trees have to be removed because reservoirs need to be stored for water
- HEP dams have short lifespans in the rainforest because they become blocked with soil washed down deforested slopes by heavy rain
Deforestation in the Amazon for resource exploitation
ILLEGAL TRADE IN WILDLIFE
It is endangering species (e.g. Jaguar) and upsetting the natural balance of the rainforest ecosystem, therefore degrading it
Deforestation in the Amazon for use of the land
-COMMERCIAL FARMING: CATTLE
- Livestock rearing in Brazil is said to account for 80% of all rainforest destruction
- The land cannot be used for long since the quality of the pasture quickly declines
- The cattle farmers then have to move on and destroy more rainforest to create new cattle pastures repeat
Deforestation in the Amazon for use of the land
-COMMERCIAL FARMING: CROPS
- The amount of rainforest cleared for the soybean crop doubled between 1990 and 2010
- This is due to being and important ingredient in many food products and the main food source for cattle
- Soil will not sustain crops for long, so after a few years the farmers have to cut down more rainforest for new plantations repeat