Structure of the rainforest
The arrangement of
plants within a tropical rainforest is such that there are different layers and
different microclimates. The diagram shows the layering of plants from the
tallest emergent trees, down to the lowest ground flora. A sharp contrast exists
between the two extremes. For example, the top of the forest has full light
conditions and the temperature and humidity vary from 10-40oC and 60-90%
relative humidity, respectively.
The Emergent layer
The Emergent layer consists of the tallest and usually oldest trees which are about 40m (120 ft) high and spread out over the tops of other trees. These trees take the brunt of climatic changes e.g. they receive the highest sunlight, hottest temperatures, wind and rain.
Air plants such as bromeliads grow from the trees. These specialised plants have no roots but capture moisture from the rain and nutrients from decaying leaves.
The Canopy layer
Beneath the Emergent layer there are smaller trees 7 5-90 ft high. These trees form a living umbrella sheltering the fauna and flora below from extremes of heat, wind and rain.
As there is little wind below the canopy most of the trees rely on insect, birds and bats to pollinate the flowers. Few plants rely on wind to disperse their seeds. This layer is the home to thousands of animal species such as primates and birds. These feed off the plentiful supply of berries and nuts. The abundance of life is added to by creeping plants and plants which grow on other plants such as orchids and bromeliads.
The Understorey is the layer between the Canopy and the forest floor. It is made up of shrubs and smaller trees growing to 12 ft in height. The amount of sunlight to the Understorey layer is limited, as is the rainfall. This layer is also teeming with life as the Understorey provides a very sheltered environment for its inhabitants.
The forest floor
At the forest floor humidity remains high (95% R H) and the temperature is fairly stable (20-300C). Only 2 5% of available sunlight reaches the ground. Most of the rainwater reaches the ground by flowing down the main trunks. There are many seeds lying dormant patiently waiting, sometimes for years, for a tree to fall. In this gap the seedlings will receive sufficient light, heat and water to grow regenerating the forest.