Topic 3a: Tropical Rainforests (PAPER ONE) Flashcards
Explain the nutrient cycle (biotic characteristic)
NUTRIENT CYCLE (Gersmehl’s Model):
BIOMASS is the biggest store which includes all living things.
When leaves fall, they drop into the LITTER store. It also receives precipitation and loses surface runoff.
These leaves decompose quickly and the nutrients are released into the SOIL store. The soil also receives nutrients by rock weathering and loses nutrients by leaching.
The plants take in the nutrients by their roots (BIOMASS store)
Explain Stratification.
Rainforest has different layers..
1: Dark forest floor
2: Understorey (less light means shorter trees around 20m, high humidity)
3: Tree Canopy
4: Emergent Layer
Why do the trees in rainforests have shallow roots?
The only fertile part of the tropical rainforest soils is a thin nutrient layer at the surface
What is a Biotic Characteristic of Rainforests?
Human activity: People hunt animals for food, spread seeds of rainforest plants through the fruits nuts and seeds they eat and affect ecosystem through their use of fire
What model explains the interdependence between biotic and abiotic factors?
Gersmehl’s Model (nutrient cycle)
What are the Abiotic characteristics of Rainforests?
- Warm temperature and moist conditions = good conditions for chemical weathering of bedrock which releases minerals into the soil
- LEACHING: constant rainfall means a lot of water travels down the soil. The water takes minerals and salts with it, making TRF soils low in nutrients
Why are TRF soils low in nutrients?
Leaching
Why do Rainforests have a high Biodiversity?
- Old = lots of evolutionary variation in species.
- They have optimum conditions for plant growth. This then supports a high animal biodiversity.
How have Plants adapted to TRF conditions?
- Canopy layer is extremely humid. Almost all plants there have drip tip leaves which means water runs off them quickly so moss doesn’t grow over the leaf surface, cutting off its light
- Trees have buttress structures at their base due to their shallow roots, so they keep their tall trunks anchored upright
How have Animals adapted to TRF conditions?
- Many species use camouflage to avoid being eaten e.g chameleons, stick insects
- Madagascar lemurs have strong legs and gripping hands/feet to leap from tree to tree to get food quickly
- Madagascan serpent eagle lives in canopy has adapted wings for fast manoeuvring to grab prey
What goods are provided by the TRF ecosystem?
Goods:
- Over 7000 drugs e.g. rosy periwinkle from Madagascar is the basis for a drug to treat childhood leukaemia
- Hardwood timber (ebony/rosewood) used for construction and wood for fuel
- Oxygen (photosynthesis)
- Food source + soils used to grow crops
What services are provided by the TRF ecosystem?
Services:
- Attracts tourists and their money, providing recreation
- Forest canopy protects soil being eroded by heavy rainfall + vegetation causes surface runoff to prevent flash flooding downstream
- Home to indigenous people
How does climate change present a threat to the TRF’s Structure?
Dry season would start to last for several months causing……
- Most trees drop their leaves in dry season to avoid water loss by transpiration
- No Canopy in dry season
- Lack of vegetation in dry season means animals adapted to live on stored food or go into hibernation
How does climate change present a threat to the TRF’s Function?
Hotter, drier conditions mean…
- Drier forests emit more CO2 than it soaks up due to forest fires
- Less vegetation cover mean when it rains surface runoff will increase due to a reduction in infiltration. So, more sediment will be carried into drainage systems and pollute water quality/harm some freshwater fish
How does climate change present a threat to the TRF’s Biodiversity?
- Temperatures are very similar all year rounds, so some species can’t cope with fluctuations due to climate change
- Plants species and animals may not survive forest fires
What are the Economic causes of Deforestation?
- Some poorer people do illegal logging as it pays well
- High demand for rosewood in Madagascar
- Madagascan government has some corruption as they often allow illegal logging in return for money
What are the Social causes of Deforestation?
- Increased population puts pressure on land available for agriculture. There is more pressure to feed larger families so farmers try to get more from their plots but it exhausts soil fertility so more plots have to be cleared.
