The Living World: Tropical Rainforests Flashcards
Why does convectional rainfall happen in rainforests?
Some rainforests lie on the equator. This means that the sun’s rays are more concentrated in these regions and this produces convectional rain.
What is leaching and how does it apply to soils in TRFs?
The soils in TRFs are not very fertile because so many of the nutrients are dissolved and washed out of the soil by the heavy rainfall. This is called leaching and it leaves the upper soil layers lighter in colour because of the lack of nutrients.
Where are most nutrients found in the soil in TRFs?
Most nutrients are found in thin fertile surface layers of the soil where dead leaves decompose rapidly in the hot humid conditions.
Why are tropical soils some of the deepest soils in the world?
Because the rocks beneath the rainforest have been weathered by the hot, wet conditions for millions of years, forming a deep soil - up to 30m deep in some places!
Why does TRF soil have a thick layer of litter?
Because of the constant growing season so leaves are always falling to the forest floor.
Why do the relatively infertile soils only support lush vegetation?
Because the nutrients are stored in the upper soil layers are quickly recycled and taken up by the growing plants.
Why are the lower layers of the soil usually red in colour?
Because they are rick in iron from the weathered rock beneath the soil.
Why do roots not extend very deeply through the soil?
Because the nutrients are all held in the upper soil layers.
How are the leaves in the canopy and emergent layer of a TRF adapted?
They have a large surface area to catch as much sunlight as possible.
Why is the canopy like an umbrella?
To maximise absorption of sunlight and allow photosynthesis so plants can grow continuously all year round.
Why is there little undergrowth in a TRF?
Because less than 5% of the sun’s rays reach this layer.
Why are the roots shallow in a TRF?
Because the water and nutrients needed by the plants are all close to the surface in the upper layers of the soil.
Why do dead trees rot quickly in a TRF?
Because of the large amounts of heat and water available to speed up decomposition. This adds nutrients to the surface which are quickly used by other plants to grow.
What are lianas and what do they use to reach sunlight?
They are vines which use other trees to reach the canopy and sunlight because there is not much light at ground level and they wouldn’t survive otherwise.
What is biodiversity?
The variety of organisms living in a particular area p both plants and animals.
Why do TRFs have so many different species (biodiversity)?
- Perfect growing conditions all year mean lots of different plants can survive.
- Different plant layers create different environmental conditions (niches).
- It is always hot and wet, so species don’t need to cope with changing conditions.
- TRFs are ancient, plants and animals have been evolving there for thousands of years.
- Large numbers of plant species support similarly large numbers of animal species.
What is deforestation?
The permenant removal of trees to make room for something besides forest.
Describe the projected global TRF loss.
An area with predicted high TRF cover is Australia with a loss of 3.4 million square hectors. An area with projected low loss of TRF cover is North South America with 34-48 million square hectors. However, Australia is predicted to have its whole rainforest wiped out by 2030.
What is cattle ranching, why is it a growing industry and how does it cause deforestation in the Amazon rainforest?
- Cattle ranching - 70%
Cattle ranching is a growing industry because Brazil is the world’s largest exporter of beef. it also has the largest commercial cattle herd of around 180-190 million. The governemtn of Brazil offers loans of billions of dollars to support the expansion of its beef industry.
Where is the Amazon rainforest?
In South America and it is north of the continent. Two countries that the Amazon rainforest is in are Colombia and Ecuador.
What % of deforestation comes from logging?
2%.
Why is population growth causing deofrestation in the Amazon?
- Human activities.
- Population growth - increases in food demand.
- Humans reuqire more land.
- We have to produce more crops because of demand for food.
How has population gorwth grown in the city of Brazil?
I has grown massively, 23% between 2000 and 2010. This is a threat because more of the rainforest surrounding the city is being cut down to accommodate more people moving in.
How is road building a cause of deforestation in Brazil?
Roads are needed in the rainforest so that equipment and transport can be brought in and products can be brought back out. However, huge numbers of trees need to be cut down to make space for them.
