The Amazon Basin is located around 5*N and S of the Equator in South America. It is mainly in Brazil but stretches into parts of other countries like Bolivia, Peru, Colombia, Venezuela and Guyana. It is the drainage basin of the River Amazon that rises in the Andes mountains to the west and flows generally eastwards into the Atlantic Ocean
The climate is hot all the year round - above 25*C in every month. There are no seasons but there is a large diurnal variation in weather. The weather is very monotonous.
There is heavy rainfall all year round with over 1500mms being typical. Often August is slightly drier in the Amazon and this is the 'burning' season.
The climate is like that of a hot greenhouse - and plants like this for growth.
The Amazon Rainforest
The importance of the rainforest -The tropical rainforest is the most diverse area of plants and animals in the world. It is the largest type of ecosystem, a biome. Unfortunately it is under considerable threat as although humans need to exploit the natural environment they live in they still have not found a balance and learned to live sustainably. We as humans have the duty of stewardship, to look after the earth but with a rapidly increasing population our own human activity is affecting our existence. We still do not understand that everything on the earth is interdependent and therefore must be treated with respect as our actions have consequences.
Rainforests once covered 14% of the Earth’s land area, now this has been reduced to 6%. The tropical rainforests grow in equatorial climates, normally 5o either side of the equator. This means that the sun is directly overhead providing great heat and convectional rainfall. The air is calm as there is no prevailing wind except during a thunderstorm. (see diagram)
1 sun's heat 2 ground heated 3 air heated
4 hot air rises, cools and vapour condenses to give clouds
5 cumulonimbus rain clouds give thundery downpours in late afternoon
What are the main features of the ecosystem and how has it adapted?
The ecosystem is structured in layers, as there is tremendous competition for light and space.
o The tallest trees (emergents grow up to 40m tall to reach sunlight).
o Below them lies the canopy a denser layer of trees that act as a shelter for the plants beneath.
o The undercanopy consists of small trees
o The undergrowth has a few plants and shrubs but not much grows here as there is not much light. The only areas where the undergrowth is thick is where there are forest clearing or where a river cuts through the landscape
o Lianas (vines) climb the trees to get access to sunlight.
o As you can see every plant has found its ecological niche.
o Each 10 km2 of rainforest contains at least 750 species of tree, over 700 different animal species (not including insects and fish!) and over 1500 species of flowering plant
Adaptations
o The trees have buttress roots (photo) to give them support
o They have drip-tip leaves to shed the heavy rainfall
o Trees have straight, branchless trunks so that they grow taller more quickly
0 They have very thin bark as they do not need protection from frost.
Appearance
o The forest appears to be evergreen as they have a continuous growing season. The tree actually just shed their leaved all year round. Producers (plants) have all their requirements here – warmth, sunlight and a good supply of nutrients.