Tropical Rainforests

• Tropical rainforests

  • Situated in the tropics, distributed between the tropic of cancer and the tropic of Capricorn
  • Close to the equator
  • In the Northern part of South America
• Climate of tropical rainforests

  • Temperature is high and constant throughout the year
  • Have a high rainfall
  • Hot air rises, creating low pressure
  • Air cools and condenses, forming clouds and rain
  • Air sinks between the tropics, creating high pressure and dry weather north and south between the tropics
  • Forms a convection current known as the Hadley Cell
• Structure of the rainforest

  • Buttresses
  • Lianas
  • Emergent tree
  • Canopy
  • Understory
  • Shrub layer
• Emergent trees


  • Grow taller than other trees to reach the sunlight
• Buttresses

  • Massive ridges that help support the base of tall trees and transport water
  • Increase surface area to help oxygen/carbon dioxide exchange
• Main canopy

  • Contains vast majority of the rainforest's biodiversity
• Understory

  • Layer of smaller trees beneath the main canopy
• Plant adaptations


  • Drip tips on leaves to allow heavy rain to drip off
  • Epiphytes that live on branches high in the canopy and seek sunlight, obtaining nutrients from water and air
  • Lianas that are woody creepers rooted to the ground and carried by trees into the canopy
  • Thin, smooth bark on trees to allow water to flow down easily
  • Leaves with flexible bases that can turn and face the sun
• Animal adaptations


  • Camouflage to hide from predators
  • Nocturnal to feed at night when it's cooler, saving energy
  • Strong limbs to remain in the canopy and move around habitat quickly and easily
• Tropical rainforest soils are surprisingly infertile
• Tropical rainforest soils

  • Nutrients concentrated at the surface, where dead leaves decompose rapidly
  • Trees have shallow roots to absorb these nutrients
  • Heavy rainfall dissolves and carries away nutrients, a process called leaching
• Importance of tropical rainforests

  • 28% of world's fresh water comes from the Amazon Basin
  • Contains 50% of all plant and animal species, making it the most biodiverse place on Earth
  • Important source of clean water
  • Prevents climate from being too hot and dry
  • Carbon sink that stores carbon
  • 28% of world's Oxygen comes from 2,000 tropical rainforest plants
  • Valuable source of medicinal plants, with 25% of all medicines coming from plants
• Valuable plants from rainforests

  • Wood and timber
  • Fruits and rubber
• Rainforests have medicinal properties that can be collected and sold
• The Rosy Periwinkle from the rainforest is used to treat leukemia
• The main types of weathering are physical, chemical, and biological
• Physical weathering is caused by the action of water freezing and thawing, plant roots growing into rocks, and animals burrowing through soil.
• The Amazon rainforest sits within the Amazon River basin and it covers an enormous area -6.7 million sq km-in South America (it is so huge that the whole of the UK and Ireland would fit in the tropical rainforest 17 times)
• Countries the Amazon spans over

  • Brazil
  • Bolivia
  • Colombia
  • Ecuador
  • French Guiana
  • Guyana
  • Peru
  • Suriname
  • Venezuela
• The Amazon stretches all the way from the Atlantic Ocean at the east to the tree line of the Andes mountains at the west
• Climate of the Amazon

  • Hot
  • Humid
  • Very wet
  • No distinct seasons
• The temperature in the Amazon is normally between 20-28°C because the Amazon is at the equator, where the sun's insolation is most intense as the rays are direct and the sun is overhead for the whole year
• It rains everyday in the Amazon, usually in large amounts of about 2000mm per year
• The Amazon has constant, fairly heavy precipitation because in this area temperatures are higher which causes air and water vapour to evaporate and rise up (creating a low pressure area) and forming large bodies of water in the sky- clouds
• The Amazon rainforest is named the "Amazon" due to the river that runs through the north of it
• The Amazon river is the largest river (by discharge volume of water) made up of a vast network of hundreds of waterways, in the world as it discharges 209,000m³ of water each second and is said to be the second longest river in the world- 6993km long
• The Amazon river's source is the Mantaro River and its mouth is the Atlantic Ocean and it travels through Brazil, Peru and Colombia
• Most of the Amazon Biome is covered in moist, dense tropical rainforest but there are small spaces of savanna, floodplain forest, grassland, swamps, bamboo forests and palm forests
• Layers of the Amazon rainforest

  • Emergent Layer
  • Canopy Layer
  • Understory Layer
  • Forest Floor
• Emergent Layer


  • 45-70m tall
  • Gets the most sunlight and high amounts of rain
  • Very windy
  • Broad-leaved, hardwood evergreens
  • Animals are agile and have a great sense of balance
• Canopy Layer


  • 30-45m above the ground
  • Very dense vegetation as trees overlap
  • Large, thick oval shaped leaves with pointed tips
  • 90% of the rainforest's animals live here
• Understory Layer


  • Receives very little sunlight
  • Cool, dark environment
  • Plants grow up to around 20m and have larger leaves
  • Majority of animals are frogs, snakes and insects
• Forest Floor


  • Almost pitch black as very little sunlight makes it this far
  • Nearly no plants can survive and grow here
  • Leaf litter decomposes quickly
  • Habitat for ferns, fungi, moss and small mammals
• Adaptations of plants in the Amazon rainforest

  • Emergents - tall, broad leaves, buttress roots
  • Flexible, waxy leaves with drip tips
  • Smooth bark
  • Buttress roots
  • Lianas
  • Epiphytes
• The biomass nutrient store is huge because the majority of nutrients in the Amazon rainforest are stored in the biomass
• Nutrients recycle very quickly in the tropical rainforest because the warm, moist conditions are the ideal climate for decomposers to break down the organic matter in the litter quickly
• The soil in the Amazon is known as latosol soil and is very thin and poor, being rich in iron and aluminium
• Due to leaching, the nutrient levels in the Amazon soil are extremely low
• The nutrient cycle in the Amazon is fragile, if just one nutrient flow changes it can negatively impact the whole ecosystem
• The rate of deforestation worldwide is very high at about 300,000km² per year