Rainforests are made up of four layers of trees. These are known as the rainforest floor, the understory, the upper canopy and the emergent layer. Each rainforest layer is very distinct and the differing levels of light and humidity in each one makes them each suitable for different types of plant and animal life.
The rainforest floor is almost entirely shaded as only around 1 per cent of the light that hits the upper layers of the rainforest penetrates to the forest floor. Generally, light only reaches the rainforest floor where a canopy tree has fallen, creating an opening. Due to the lack of light, very little plant life grows on the rainforest floor, making it possible for a person to walk through most parts or the rainforest easily. Although the ground is covered by decomposing vegetation, due to the amount of organic litter that falls from the upper layers, the top soil is thin and poor in nutrients. The litter is quickly broken down by earthworms, termites and fungi and further decomposed by the heat and humidity. This compost is then absorbed by the shallow roots of the rainforest trees. Insects and larger animals such as jaguars and tigers, depending on location, inhabit this layer.
The understory, or lower canopy, is the rainforest layer that lies between the rainforest floor and the canopy. This layer is made up of 60-foot trees, the trunks of canopy trees, plants and shrubs and contains a large amount of insects. As the understory is a shady layer, its plants have large, broad leaves in order to capture as much sunlight as possible. There is very little air movement in the understory, resulting in a constantly high level of humidity.
The upper canopy contains trees between 60 and 150 feet tall. As light is readily available at the top of this layer, a large biodiversity of plant life inhabits the upper canopy. Most of the animals in the rainforest also live in this layer and many of them rarely go down to the rainforest floor as there is such an abundance of food available in the upper canopy. The upper canopy acts like a reverse umbrella, trapping moisture and humidity underneath leaves and blocking out sunlight. Drip spouts on leaves at this level allow rain to run off, keeping them dry and preventing the growth of mould and mildew.
Trees in the emergent layer of the rainforest reach up to 240 feet in height. These trees often have small pointed leaves as they are exposed to drying winds. They also have smooth, straight trunks, few branches and shallow roots which spread out up to 30 feet in order to support their size. In monsoon rainforests, some trees in this layer lose their leaves in the brief dry season. Trees in the emergent layer receive more sunlight and moisture than those in the shady, humid conditions of the lower layers. A variety of insects, birds and bats inhabit the emergent layer.
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