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Facts about Tropical Rainforests

What are the features that are typical of all tropical rainforests. Tropical

rainforests cover about six to seven percent of the earth's land surface and are

mainly located in the tropics. That is the regions of the earth between

the Tropic of Cancer and the Tropic of Capricorn. The world's largest

rainforests are the Amazon rainforest of South America, the Congo River Basin in

West Africa and the rainforests of Southeast Asia. There are also smaller

rainforests in Central America, Madagascar, the Pacific Islands, Northern

Australia and India. The reason for this pattern is that on the equator sunlight

strikes the earth at a roughly a ninety degree angle. This results in intense

solar energy as there is a consistent length of day. That is twelve hours a day,

365 days a year. Regions close to the equator have warm

temperatures all year round. Tropical rainforests thrive in equatorial

regions since plants love this consistent light that powers

photosynthesis. The high temperatures of the tropical regions generates a water

cycle whereby the accelerated evaporation of water results in high

levels of rainfall. Tropical rainforests receive at least 2,000 millimetres of

rainfall per year. The climate of equatorial regions are

heavily influenced by the Intertropical Convergence zone or ITCZ. The ITCZ

is the region near the equator where the northeast trade winds and the southeast

trade winds converge, forcing air up into the atmosphere.

This is aided by the fact that the intense solar heating of the tropics

heats the ground, forcing warm air to rise through

convection. The air cools as it rises causing water vapor to condense into

clouds, which eventually leads to convectional precipitation. These storms

are often heavy but are over relatively quickly.

The position of the ITCZ changes seasonally. It moves north in the

Northern Hemisphere summer and South in the Northern Hemisphere winter. This is

what is responsible for wet and dry seasons in tropical regions. In the

northern hemisphere the wet season occurs from May to July. In the southern

hemisphere from November to February.

Rainforests have a high level of biodiversity. Although they cover less

than 7 percent of the Earth's surface, about half of the Earth's terrestrial

plants and animals live in rainforests. From the great to the small, tropical

rainforests hosts an enormous diversity of wildlife. To name a few from these

forests in Thailand one can find mammals such as the Asian elephant,

Gibbons and crab-eating macaques. There are

numerous bird species. There are an abundance of reptiles and amphibians.

Insects such as butterflies, dragonflies, ants

and termites all flourish here and the rivers of rainforests teeming with fish.

The main reason for this abundance of life is that since rainforests are

located of the tropics they receive a lot of sunlight. Plants convert the

sunlight to energy through photosynthesis. Thus there's a lot of

energy stored in the rainforest plants. These plants are in turn eaten by

animals. The canopy structure of rainforests provides a habitat for animals and

plants to shelter, hide and abundant food sources. Species in the rainforest often have

an interaction known as a symbiotic relationship. These relationships are

sometimes beneficial or others are harmful. For example, strangler fig trees

often dispersed by birds will germinate in the canopy of a host tree. As it grows

the roots develop and descend along the trunk of the host tree. Once they reach

the ground the roots enter the soil. Gradually the roots envelop the host

tree forming a lattice like structure which surrounds the hosts trunk. The fig

suffocates the host leaving behind a magnificent fig with a hollow core. The

dense vegetation of equatorial rainforests competes for sunlight

resulting in a stratified pattern and the rainforest.

Scientists consider rainforests to have five vertical layers. Emergent trees

consist of widely spaced trees with an umbrella shape. These are the tallest

trees ranging up to 30 to 40 metres whose tops protrude much higher than the

average canopy height. The canopy layer consists of overlapping branches and

leaves formed by tall rainforest trees around 30 metres with long slender

trucks. The tall trees of both the emergent and canopy layers have shallow

spreading root systems designed to collect nutrients, and wide buttress

roots to prevent them from toppling over. Most of the plants and

animals in the rain forest including monkeys frogs lizards and birds live in

the canopy. Parasitic plants such as orchids grow in cracks in the branches

high up at the canopy. The sub canopy is made up of shorter trees around 20

meters high. Trees often support epiphytes and lianas. This layer is also

the home of many birds and animals. The shrub or sapling

layer consists of bushes, small trees and ferns that are adapted to living in

low-light conditions. The sparse undergrowth is caused by the lack a light

penetrating the canopy, with only three percent penetration. Where the rainforests

meets the edge of an estuary, there may be mangroves. The rainforest floor is

often dark, humid and clear of dense vegetation due to the constant shade from

the canopies leaves. Here you will find large tree trunks, hanging vines,

seedlings and saplings and a relatively sparse number of ground

plants. It is here on the forest floor where decomposition takes place.

Decomposition is the process by which decomposes like fungi and microorganisms

break down leaf litter, dead plants and animals and recycle essential materials

and nutrients. Many of the largest rainforest animals such as the Asian

elephant are found on the forest floor.

Tropical rainforests typically have reddish brown soils known as laterites. The red

coloration comes from the oxides of iron and aluminium in the soil. The upper

horizons of the soil are thin and low in minerals due to a process called

leaching. This occurs when the frequent heavy rainfall in tropical regions

causes high volumes of water to wash away iron, silica and other minerals to

the lower horizons of the soil. As a result the top layer is often lighter in

color. Despite the infertile soil the

rainforest survives because of the rapid nutrient cycle that exists in the warm

humid environment. The hot and humid conditions of a tropical rainforest are

ideal for decomposers like insects, fungi and bacteria. They decompose dead plant and

animal matter quickly and convert it back to nutrients. Most of the nutrients

are taken up by the rapidly growing plants and trees immediately rather than

remaining in the soil.