Tropical Rainforest .

Distribution

Tropical rainforests are found in places that experience a tropical equatorial climate . This climate is a sub-type of the tropical climate , and is experienced in places very near the Equator , specifically between 10 degree North and South of the Equator . These places experience high temperatures about 27°C and rainfall above 1500 millimetres throughout the year .
Tropical rainforests are mainly located in the Amazon Basin in South America , the Congo Basin in Africa and parts of Southeast Asia such as Malaysia and Indonesia .

Structure of the forest 

The tropical rainforest can be divided into 5 distinct layers according to height :

Emergent layer - Tall trees , called emergents reach a height of 30 m to 50 m . Their   crowns  appear above the canopy layer . These tress have tall , thick and straight trunks .

Canopy layer - Trees on this layer reach a height of 15 m to 30 m . Their wide , shallow and umbrella-shaped crowns form a continuous leaf cover , to prevent sunlight to penetrate into the lower layers of the forest .

Understorey layer - Trees here have narrower , oval-shaped crowns . Their height range from 6 m to 15 m . Young trees from the emergent and canopy layers are also found in this layer .

Shrub layer - Tree saplings and woody plants are found here . They may grow up to 6 m high .

Undergrowth layer - Made up of grasses , ferns , mosses and fungi . Plant growth is sparse as very little sunlight reaches this layer . Plants here reach a maximum height of 5 m .

Leaves

Tropical rainforests are evergreen as the leaves remain green all year round due to the constant high rainfall throughout the year . 
The leaves of the trees are 
- large and broad to maximise the surface area for photosynthesis . 
- leaf surfaces are waxy , with drip tips to allow rainwater to drain off easily , this preventing harmful bacteria from growing on them . This protects the plants from disease as the high temperatures and rainfall promote rapid growth of bacteria .

Flowers

The plants in a tropical rainforest flower and produce                                                                     

fruits throughout the year because temperatures and rainfall are generally high all year round . However , the
still air below the canopy layer does not allow pollination to be carried out by wind . Therefore , the flowers and fruits are :
     - colourful and sweet-smelling to attract insects for pollination and animals for seed   dispersal . 

Barks

In the tropical rainforests , the trees have developed relatively thin and smoot barks because there is no need for protection against cold or dry conditions .

Roots

The high temperatures and rainfall all year round cause the leaf litter to decompose and form humus rapidly , supplying nutrients to the topsoil , which is uppermost layer of the soil . Hence , the roots of trees in the tropical rainforest are shallow and spread widely as they do not need to reach deep into the soil for water and nutrients .

As the leaf litter decomposes to form humus , the life of a tree begins with the growth of its sapling on the forest floor .

Questions & Answers .

1. Why do you think the branches are found only on one third of the trunks ?

     They are adapted to the lack of sunlight because of the little sunlight when passes        through the canopy layer .

2. What do you notice about the undergrowth ? Suggest reasons why .

     It is sparse because little sunlight passes through the interlocking canopy , and there is not much plant growth there .

3. DO YOU THINK TEMASEK FOREST IS A PRIMARY OR SECONDARY FOREST ? WHY ? You are to cite evidence based on your observations .

     It is a secondary forest . The canopy layer is not distinct with only some form of interlocking branches . More sunlight is able to pass through the canopy .