Geography 7.3.1 Tropical Rainforest

• All parts of the tropical rainforest (TRF) ecosystem are interdependent

• A change in one part affects others

• Deforestation leads to the loss of habitats and reduction in biodiversity

• Loss of trees also impacts the nutrient cycle

• The interdependence of the rainforest components means that when one element is affected it then impacts all the other components

An example of interdependence

• A decline in one species (especially if it is a keystone species) can lead to a decline in other species 

  • The Zam tree produces seeds which are food for agouti and who disperse the seeds 

  • The agouti is hunted for meat, reducing their populations, which means fewer seeds are dispersed

  • Fewer new Zam trees will germinate and so there is less food for leaf cutter ants, which in turn means less food for the tree frogs and the snakes which prey on the frogs

  • The Zam tree is pollinated by a particular species of butterfly. Without the flowers the numbers of the butterfly species will decline: this also affects the beetles which lay their eggs in the butterfly faeces

  • Plant and animal species may become extinct: this may happen to some before they are even discovered

  • Important medicinal plants may become extinct

  • Indigenous communities may be forced to abandon their traditional lifestyle due to the lack of food to hunt and gather

Adaptations

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

Structure of the tropical rainforest (TRF)

• The TRF has five distinct layers

  • Ground layer (0m)

  • Shrub layer (3-4m)

  • Under canopy (15m)

  • Canopy (30m)

  • Emergents (45-55m)

Typical structure of a tropical rainforest 

Adaptations of Plants and Animals in a TRF

Plants

Plants

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

Buttress roots: these large roots above the ground which help to support the very tall trees because the roots below the surface are shallow

Lianas: vines which use the tall trees as support to reach the sunlight

Epiphytes: these are plants which grow on trunks and branches of trees getting nutrients from air, rain or debris accumulating around the plant

Straight, smooth trunks: help to reduce the number of epiphytes using the tree

Adaptations of Plants and Animals in a TRF

Animals

Animals

Sloth: algae grow in the fur of the sloth helping to camouflage it

Toucan: they have a large bill to reach and cut fruit from the branches of trees. They are also strong allowing them to crack nuts open

Primates: they have prehensile tails to help them climb trees

Geckos: they have large, flattened toe pads with sticky scales which allow them to grip the smooth tree trunks

Stick Insects: Their stick and leave shapes help them to be camouflaged

• Why do TRFs have some of the highest levels of biodiversity of any ecosystem?

• he wet and warm climate means there is year round growth 

• Wide variety of plants provides a range of habitats and food 

• Rapid nutrient cycling increases plant growth

• Lack of human activity in the past has meant that plants and animals are undisturbed 

Nutrient cycle

• 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

• Most of the nutrients are stored in the biomass

• Few nutrients are stored in the soil and the litter

Tropical rainforest nutrient cycle

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