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The structure of a forest

Evergreen forests, such as the Amazon Rainforest and the tropical rain forests have a peculiar structure, in terms of the layers in which the trees are organized. This organization is shaped mainly by abiotic factors such as humidity, sunlight, wind etc. There are four basic layers namely the Emergent, Canopy, Understory and Forest floor.

The Emergent layer

The Emergent layer is made up of the tallest trees, spaced out, usually with straight branch-free trunks (large trees are about 16ft in diameter), with a crown on the tops. They are about 100ft – 200ft tall with supporting buttress roots spreading up to about 20-30ft. The trees have small pointed leaves, which are adapted to withstand wind action over tree tops. Trees here are in constant sunlight. Birds such as the hummingbird and parrots are common. Animals here tend to be lightweight, and include the Sloth and the Spider Monkey. The Brazil Nut tree and Kapok Tree are common trees in this emergent layer.


The Canopy

The Canopy is the layer that stops sunlight and rainwater from getting to the layers below it. The trees grow up to about 130ft and have broader leaves and drip spouts. This leaf feature makes rainwater drip down quickly rather than staying on the leaves. There are millions of insects and animals in this layer as they have enough food to keep them there. Common animals include squirrels, monkeys, reptiles, bats, and a variety of birds. Visibility is low from the thickness of leaves and network of branches. As a result, animal sounds are loudest in this layer because they communicate with sounds.

Diagram of a forest


The Understory

The Understory has fewer trees, but lots of shrubs and small trees growing up to about 12ft high. The area is made up of buttress roots from taller trees, climbing plants, ferns and branches extending downwards. There is very little sunlight here with lots of fungi, moss, algae, mold and mildew on the leaves and trunks. This layer is home to many insects, frogs, snakes, beetles, butterflies and termites. The wet, humid and dark nature of this layer makes it an ideal home for mosquitoes and bugs.


The Forest Floor

The forest floor is the ground level of the structure. It has shallow soils of poor quality, with micro-organisms and life-forms feeding on decaying matter on the floor. The moist, dark conditions aid decomposition of organic matter and nutrients are quickly absorbed by the trees and other plants on them. There is very little light here. Animals that are found here are herbivores and carnivores, many of which have climbing abilities. Animals are also larger in size and heavier than animals in the other layers. They include scorpions, armadillos, wild cats, mongoose, lizards, snakes and a variety of insects.

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