The equatorial climate zone is situated around the equator and cover wide areas in South America, Central Africa and South-East Asia.
Typical features of this climate are all year round, high daily and nightly temperatures as well as heavy rains falling almost every day.
The warmth and the humid are the reason for the presence of the great diversity of plant and animal species on the planet.
Temperature of Brunei Darussalam
As the areas with an equatorial climate are located at or near the equator so the sun shines overhead all the year round.
Temperatures in Brunei generally remain uniform. The maximum mean temperature is about 32.1◦ C while the minimum is about 23.8 ◦C.
The diurnal range (the difference between high and low of any given day) is however quite large and it is said that night is the winter of the tropics.
Climatic changes in Brunei are minor and are caused mainly by the monsoon winds. Brunei has two monsoons in a year.
The Northeast monsoon runs between December and March. December receives the maximum rainfall.
The Southwest monsoon lasts between May and September.
There are two ‘inter monsoon’ phases. These are between April and May and November and December. The period from February to April is relatively dry.
Rainfall and Humidity
Rainfall is heavy and falls uniformly in each month of the year . Relative humidity is also excessive.
The total annual rainfall for the equatorial regions is generally more than (2000 mm) and the average relative humidity is around 80 %.
The high temperature combined with excessive humidity, therefore makes the weather very unpleasant and trying.
Brunei Darussalam , the total annual rainfall is more than (2290 mm) and no month has rainfall below (150 mm).
Such a heavy rainfall gives rise to thick forests and large areas in this type of climatic zone are covered with dense forests.
TROPICAL RAINFOREST VEGETATION
The tropical rainforest is found in area with an equatorial climate such as part of central and South America, Africa and South east Asia . The Amazon Basin and the Zaire Basin are two largest areas of tropical rainforest.
The tropical rainforest has 5 layers .
1. Emergent layer– the uppermost layer where the tallest trees rise above the rest. The tree grows between 40 and 48 m to capture direct sunlight.
2 . Canopy layer– Tall trees in this layer are called canopy tree. They grow so close together that their crown interlock to form a continuous canopy. The canopy later shuts out most of the sunlight from the forest.
Non- parasitics plant such as lianas and epiphytes are also found here. Two common examples of epiphytes are the staghorn fern and bird’s nest fern.
Parasitics plant are attached themselves to the roots , trunks or branches of the canopy trees and feed on them. Examples wild orchids.
3. Understorey layer – short trees are found in this layer. Some epiphytes and lianas are also found here.
4. Shrub layer – shrubs , young trees and ferns are found here.
5. Ground layer– ferns, mosses, fungi and other small plants are found here because they do not need much sunlight to grow. The vegetation is sparse, hardly any leaf litter on the forest floor because the fallen leaves decompose very rapid in the equatorial climate.
5 layers structure
Types of trees
The forest is densely, evergreen do not shed all their leaves over same period of time.
Most trees are hardwood. They are very durable and heavy.
Examples are the Seraya, Meranti, Mahogany, Ironwood and Ebony.
Tropical forest have broad leaves with a waxy leathery or hairy texture. The reasons are allows the rain water to run off easily and minimises the loss of moisture through transpiration.
Some leaves are narrow , downward pointing tips. The reasons are to help the tree adapt to the high amount of precipitation and allow rainwater to flow quickly off the leaves.
Shallow root due to water and nutrients are found in the top layer of the soil. The reasons to supply constant amount of water to the soil. To speed up the decomposition rate of the fallen leaves.
Buttress root which grow one to five metres above the ground. Emergent and canopy trees will support the great weight of the tall trees.