Ecosystem Characteristics (CIE IGCSE Geography)

• The Tropical rainforest (TRF) biome is mainly found in a band between 15^o north and 15^o south of the equator within the equatorial climate zone
• Covering only 6% of the Earth's surface the main areas of tropical rainforest ecosystem are in the following countries;
  • Amazon which is the largest remaining rainforest on Earth usually associated with Brazil but covers parts of seven other countries
  • Central America including parts of Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama
  • Central Africa including Cameroon, the Central African Republic, the Republic of Congo, the Democratic Republic of Congo (DRC), Equatorial Guinea and Gabon
  • Indo-Malaysia, including Malaysia, Indonesia and a number of other countries in South-East Asia

Biodiversity

• TRFs contain the highest biodiversity of plants and animals on Earth
  • Estimates range from over 50% to 80% of the world's plant and animal species
  • One 10km² area can contain up to 1,500 flowering plants, 750 species of trees, 400 species of birds and 150 species of butterflies

Nutrient cycle

• The TRFs have a continual growing season with high rainfall and temperatures all year round
• The nutrient cycle is rapid
  • Trees and plants lose their leaves all year round
  • The high level of moisture and high temperatures leads to rapid decomposition and recycling of nutrients
  • Plants grow quickly which leads to a rapid uptake of nutrients from the soil

Tropical rainforest nutrient cycle

• The result of this rapid nutrient cycle is that the soil in the TRF is not very fertile

Structure of the tropical rainforest 

• The TRF has five distinct layers
  • Ground layer (0m)
  • Shrub layer (3-4m)
  • Under canopy (15m)
  • Canopy (30m)
  • Emergents (45-55m)

Tropical rainforest structure

Adaptations

• The plants and animals within the TRF are very well adapted to the climate conditions

Plants	Animals
Waxy leaves with drip tips - these ensure that rainwater runs off the leaf and does not remain which would encourage mould growth or break the leaf	Sloth - algae grow in the fur of the sloth helping to camouflage it
Buttress roots - these large roots above the ground which help to support the very tall trees because the roots below the surface are shallow	Toucan - has a large bill to reach and cut fruit from the branches of trees
Lianas - vines which use the tall trees as support to reach the sunlight	Primates - have prehensile tails to help them climb trees
Epiphytes - these are plants which grow on trunks and branches of trees getting nutrients from air, rain or debris accumulating around the plant	Geckos - have large, flattened toe pads with sticky scales which allow them to grip the smooth tree trunks
Straight, smooth trunks - to reduce the number of epiphytes using the tree	Stick Insects - their stick and leave shapes help them to be camouflaged

Food web

• As in all ecosystems the TRF has a complex food web which includes
  • Producers
  • Primary consumers
  • Secondary consumers
  • Tertiary consumers

Tropical rainforest food web

• Hot desert biomes are mostly found in a band around the Tropic of Cancer and Tropic of Capricorn
• Approximately 20% of the Earth's surface is covered by hot desert ecosystems including in the following areas;
  • North America - the Mojave and Sonoran Deserts of the USA and Mexico
  • South America - the Sechura Desert in Peru and the Atacama Desert in Chile
  • Africa - the Sahara, Kalahari, Namib and Somali Deserts
  • Middle East - the Arabian Desert 
  • Asia - the Dasht-e Lut in Iran, the Gobi, Turkestan, Thar and Taklamakan Deserts
  • Oceania - the Australian Desert

Biodiversity

• Hot deserts have one of the lowest biodiversity of plants and animals on Earth
• The hot desert biome supports approximately 5000-6000 plant species, many invertebrates and up to 20 species of bird

Nutrient cycle

• The growth of plants is limited due to the extremes of temperature and lack of water
• The nutrient cycle is very slow
• Most nutrients are stored in the soil

Hot desert nutrient cycle

• Due to a lack of organic matter the soils are coarse, sandy and low in nutrients

Adaptations

• To be able to survive the extreme temperatures and lack of rainfall the plants and animals are extremely well adapted

Plants	Animals
Low growing - this helps to avoid water loss due to strong winds	Camels have a range of adaptations including two sets of eyelashes and nostrils which close to keep sand out of their ears and noses. They also store fat in their humps so they can survive for long periods without food or water
Thick stems - used to store water	Fennec Fox - have large ears which help them to lose heat
Shallow roots - these spread out near the surface to catch whatever rain falls	Burrowing - many animals burrow to avoid the intense day time heat
Long roots - some plants have long tap roots instead of shallow roots to reach water deep underground	Insects and reptiles have waterproof skin to reduce water loss
Small leaves or needles - the smaller surface area reduces water loss	Nocturnal - some animals hunt at night to avoid the daytime heat

Food web

• As in all ecosystems hot deserts have a complex food web which includes
  • Producers
  • Primary consumers
  • Secondary consumers
  • Tertiary consumers

Hot desert food web