Tropical Rainforests

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Tropical Rainforests

Climate: The tropical rainforest ecosystem is located in a band 5 either side of the equator. This means that it is hot throughout the year, with temperatures ranging between 25 and 30°C.There also is a massive level of precipitation, usually between 2000 and 3000mm each year. Most afternoons experience a heavy downpour, which helps to keep the rainforest moist.

Rainforest canopy

Soils: Rainforest soils are called latsols. They have a very thick litter layer, which decomposes rapidly in the hot, moist conditions to create thick humus, full of nutrients. This produces a soil, which acts as if it is very fertile. However that is not actually the case and if the vegetation is removed the soil quickly becomes very infertile. Rapid leaching occurs to remove minerals and nutrients from the humus layer.

Vegetation and animals: Tropical rainforests boasts a huge variety of vegetation and animal life. This can be divided into five simple layers, from the canopy to the forest floor, where you will see distinctive types of vegetation:

  • The top layer is called the emergent layer. This is where a few of the largest trees have managed to grow higher than the main canopy to try to capture as much light and rainwater as possible. Examples include mahogany trees. Birds and insects would be expected to be seen in this layer.
  • The canopy layer is the layer at approximately 30 metres created by the many tall trees of the rainforest. The canopy virtually blocks out all the light for the vegetation below and is the home for birds and monkeys.
  • The under canopy is the layer between 10 and 20 metres where there area few trees, but mainly lianas and other vines which hang down from the taller trees that they are using to climb up to the light.
  • The shrub layer is the fourth rainforest layer. These plants are between 5 and 10 metres in height and consist of small trees and other plants waiting patiently for a tree fall to create a gap in the canopy to allow them the light to grow.
  • The forest floor is the final layer, where there are ferns and other plants as well as the massive tree roots. Animals such as tapirs, frogs and even alligators inhabit this layer.

The main driving force in the rainforest vegetation is the fight for light. Hence when a tree falls, creating a gap in the canopy, there are a numbervery fast growing species that will have been almost lying dormant that will rapidly grow to try to capture all the available light.

Most of the tall trees have wide shallow roots, as the majority of the water and nutrients are found in the very top layer of the soil. To prevent them from toppling over most of the tall trees have grown large buttress roots, which act as stabilisers. Rainforest trees have straight trunks, with their leaves and branches concentrated right at the top to enable them to make bestuse of all the available light.

Logging: Rainforest trees are mainly hardwoods. These can be very lucrative on the international market and as many of the countries of the world with tropical rainforests in them are LEDC's, it is a market that they often exploit. Unfortunately, to get to certain types of tree, logging companies destroy all the other vegetation around them.

Ranching: Large-scale forest clearance has taken place to make way for huge cattle ranches, as these are also a lucrative industry for the country. The cattle quickly erode the fragile, and now unprotected, soil. The farmers are not interested in the wood for sale, they often just burn it.

Damming: To provide power for industries such as the mines and papermills, large dam schemes have been introduced. An example of this is the Tucurui Dam in the Northern Brazilian rainforest. The reservoir it created flooded an area of 2875 square kilometres and displaced 40,000 people. It destroyed hundreds of species of animals and thousands of species of plants, some of which may never have actually been known about.

Subsistence Farming: The initial growth into the rainforests was along roads that were cut through the dense vegetation. These encouraged people looking for a better way of life to enter the forest and clear areas beside the roads for farming. They presumed that because the rainforest was so rich with life, the soil would be very fertile. Unfortunately that is not the case, and within a few years the farmers were forced to move on because the soil had become so bad. Not being able to afford to go back to the cities on the Eastern coasts, most of these farmers end up copping down another area of forest and starting again. Unfortunately the results are equally predictable.

Mining: the Northern Amazon rainforest is rich in minerals, such as bauxite, iron ore and even some gold. This has meant that vast areas of rainforest have been cleared to allow mining to occur. Settlements have grown up, such as Carajas and Manaus purely based on the mining industry.


Sustainable Development: The rainforests do have a huge number of very useful resources that can be used without damaging the ecosystem. The native Amazon Indians used a method of farming called "slash and burn" where they deforested an area and used it for farming for a few years. They then left it and went on to another site. Plants and trees quickly invaded the deforested area, so that soon there was very little evidence that they had ever been there. They also used the rainforest for hunting and fishing.