Characteristics of a Biome

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Characteristics of a Biome
Introduction:
1. The biome that I have studied is the Amazon Rainforest
biome.
2. The characteristics that I will examine are climate, soils and
flora.

Climate:
1. Climate is the main characteristic of a biome as it determines
what type of soil is formed, what types of plants grow there
and which animals inhabit the region.
2. The Tropical Rainforest biome is found between 23º north
and south of the equator and has a tropical climate that is hot
and humid all year.
3. At these latitudes, the sun’s rays are directly overhead and hit
the earth at a high angle causing intense solar heating of the
surface.
4. The diurnal range is subsequently greater than the seasonal
variation of temperature, with the range being between 34º C
and 20º C.
5. The region experiences an average temperature of about 27º
along with high humidity levels, averaging between 77% and
88%.
6. Convection forces the hot air to rise and this air condenses to
form clouds, generally in early afternoon, and by midafternoon convectional thunderstorms form and precipitation
begins.
7. Tropical rainforests with a cloud cover, such as the Amazon
Basin, are known as selvas.
8. Annual precipitation exceeds 6,000 mm with approximately
200 days per year experiencing these heavy afternoon
showers.

9. The region’s high rate of evaporation causes heavy
convectional rainfall as 50% of the precipitation in the
rainforest comes from its own evaporation.
10. Although there are no seasons in the rain forest biome,
areas with very high temperatures and precipitation do
experience a slight drying and cooling period in June and
December.

Soil:
1. Tropical red soils, or latosols, make up the zonal soil that has
developed beneath tropical rainforests.
2. The soil is a red/orange colour as a result of the laterisation
process, a form of intense chemical weathering and leaching
that occurs in hot climates.
3. The heavy rainfall washes the nutrients in the humus into the
soil where it is taken up by shallow roots of the rapidly
growing plants before it is washed too deeply into the soil,
giving the rainforest a very short nutrient cycle.
4. The soil has a thin O-horizon due to intense bacterial which
rapidly decomposes dead organic matter.
5. A study of the Amazon forest showed 99% of the nutrients in
the soil are held in the root mats of the forest floor.
6. The high levels of iron oxide and aluminium oxide in the Ahorizon, along with the laterisation, means the soil has a
yellow/orange colour.
7. In many places latosols are so rich in aluminium that they are
termed bauxite, and have to be mined and processed to get
the aluminium out of them.
8. High temperatures can also bake the A-horizon, turning it into
a hard brick-like soil called laterite, which cannot be
cultivated.
9. The B-horizon can be up to 40 metres deep and is uniform in
texture due to intense leaching in the high temperatures.

Flora:
1. The high temperatures, high rainfall and 12 hours of daily
sunshine means Tropical Rainforest biomes are ideal for the
growth of vegetation.

2. It is estimated that a typical patch of rainforest measuring just
6 km² contains as many as 1,500 species of flowering plants
and 750 species of tree.

3. The forest floor occupies the lowest 2 metres or so of the
rainforest and, as only 1% of the sunlight reaches the ground,
vegetation has adapted in order to survive.

4. Trees have developed a shallow root system because all the
nutrients are close to the surface.

5. Buttress roots form an aboveground root system to increase
the surface area from which trees can draw their nutrients.

6. The understorey reaches 2 to 20 metres above the forest floor
and has vegetation made up of mainly vines and epiphytes
which have large leaves to trap as much light as possible.

7. Lianas have their roots on the ground but climb high into the
canopy layer to reach available sunlight by wrapping around
trees for support.

8. The highest layer of forest vegetation is the emergent layer
which contains the tallest trees in the forest, e.g. mahogany
which is up to 70 metres high.

9. The tallest trees have small leathery leaves and waxy bark to
cope with wind and sunshine.

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