Tropical Rainforests

• The water cycle:

  1. Water evaporates from water bodies and land when heated and turns into water vapour

  • water from plants through transpiration

  2. Water vapour moved by winds

  3. Water vapour condenses to form clouds —> rain

  4. Water flows back into river or sea or is taken up by plants
• the sun is usually overhead so its always hot, which increases evaporation rates. This means theres lots of water vapour, so rainfall is high. vegetation is dense so water is intercepted and stored by plants
• nutrient cycle

  1. Evergreen trees drop material all year round
  2. Fast decomposition (due to warm/moist climate) releases nutrients into the soil
  3. Rainwater soaks nutrients into the soil
  4. Nutrient-rich water is rapidly taken up by plant roots
  5. Animals eat plants and nutrients, die and decompose
• the climate is the same all year round, as it is very hot as its on the equator

  • it’s always 20-28˚C
  • high rainfall of 2000mm a year
  • rains everyday in afternoon
• The soil is very deep but there is only a thin fertile layer on the top

  • called the humus layer
• Soil profile

  1. Hot/wet climate means chemical weathering is very rapid
  2. Dropping of leaves all year around, forming a thick leaf layer
  3. Quickly broken down, forming humus layer
  4. Humus is thin as plants quickly absorb all the nutrients
  5. Nutrients are leached down due to heavy rain
  6. Soil is nutrient poor
  7. Roots remain close to surface
• interdependence:

  Warm and wet climate means plants grow quickly — dense leaf cover protects forest floor from wind and rainfall. The roots hold the soil together, preventing it from being eroded
• interdependence:

  Lack of wind near forest floor means plants have to rely on bees + butterflies for pollination
• interdependence:

  Agouti (a rodent) are one of only animals that can crack open Brazil Nuts to eat the inside. Sometimes the agouti bury the nots which can sprout into new seedlings. This is a symbiotic relationship — if agouti became extinct, Brazil Nut trees would decline
• • Deforestation reduces amount of co2 being absorbed from atmosphere, which adds to the greenhouse effect and changes climate
• Goods from the rainforest

  • Medicine
  • Coffee
  • Chocolate
  • Hardwood — contributes to country’s economy
  • If cleared, it can provide space for farming, creating employment and generating income
• services from the rainforest

  • home to the highest diversity of animal and plant species on the planet
  • absorb around 0.7 billion tonnes of co2 every year, reducing co2
  • rainfall intercepted by plants roots prevents flooding in local area
• 4 human activities in the rainforest:

  • logging
  • agriculture
  • mineral extraction/mining
  • tourism
• Logging

  • the soil is eroded as there aren’t trees to hold the soil together
  • Loose soil can contaminate local rivers
  • Logging interrupts the water cycle, and it becomes dry and at risk of wildfires
  • Less protection from flooding
• agriculture

  • Land often cleared suing slash and burn techniques. Burning plants produced co2 —> greenhouse effect
  • Fertilisers leach into nearly streams, threatening the wildlife
• Mineral Extraction/Mining

  • Heavy machinery —> noise and dust pollution
  • Deforestation
  • Toxic chemicals used for metals are washed into streams and kill the wildlife
• Tourism

  • Scare wildlife, causes nesting birds to abandon their young
  • Damage vegetation by walking on it, leave litter