characteristics of tropical ecosystems
Tropical equatorial rainforests have a distinct climate. They are hot and wet all year round, this is because if their location near the equator which means that the sun is overhead all year round. Rainfall is high, around 200mm per year, it rains everyday because the high temperature creates convectional rainfall.
Convectional Rainfall:
1. The sun warms the ground which conducts this heat to the air above and evaporates surface water.
2. The warm air can hold lots of water vapour.
3. The warm, wet air rises and in doing so it is cooled.
4. The cooler the air, the less water vapour that can be held so water condenses to form clouds and then rain.
The soil moisture budget is high in tropical ecosystems because precipitation is higher than potential evaporation.
Tropical rainforests have a layered structure. Different amounts of sunlight reach the different levels of vegetation and tress have different shaped crown to absorb as much light as they can. The tallest trees are called the emergents. They can reach around 40m, have straight trunks and widely spaced branches only at their crown where most light reaches them. They receive the most direct sunlight of all the layers in the rainforest. The canopy layer is a continuous layer of trees around 30m high. It absorbs about 80% of incident light and shades the rest of the forest. The next later of trees are known as the undercanopy, they are around half the height of the canopy. Below this is the shrub layer which is closest to the ground. Only 5% of direct sunlight reaches this layer so the shrubs have large, broad leaves to absorb as much of the available light as possible.
Rainforest soils are known as latosols. They are very nutrient poor because:
There is a thin layer of nutrients in the top layer of soil, where organic matter is decaying. Trees keep their roots close to the surface in order to capitalise on these nutrients.
Organism Adaptations: Plants
Organism Adaptations: Animals
Human Activity
Deforestation is the biggest threat to tropical rainforests. There are many reasons why forests are being cut down which include: small scale farming, commercial logging, cattle farming and commercial agriculture. Deforestation can have dramatic social, environmental and economic impacts.
Environmental Impacts:
Social Impacts:
Economic Impacts:
Convectional Rainfall:
1. The sun warms the ground which conducts this heat to the air above and evaporates surface water.
2. The warm air can hold lots of water vapour.
3. The warm, wet air rises and in doing so it is cooled.
4. The cooler the air, the less water vapour that can be held so water condenses to form clouds and then rain.
The soil moisture budget is high in tropical ecosystems because precipitation is higher than potential evaporation.
Tropical rainforests have a layered structure. Different amounts of sunlight reach the different levels of vegetation and tress have different shaped crown to absorb as much light as they can. The tallest trees are called the emergents. They can reach around 40m, have straight trunks and widely spaced branches only at their crown where most light reaches them. They receive the most direct sunlight of all the layers in the rainforest. The canopy layer is a continuous layer of trees around 30m high. It absorbs about 80% of incident light and shades the rest of the forest. The next later of trees are known as the undercanopy, they are around half the height of the canopy. Below this is the shrub layer which is closest to the ground. Only 5% of direct sunlight reaches this layer so the shrubs have large, broad leaves to absorb as much of the available light as possible.
Rainforest soils are known as latosols. They are very nutrient poor because:
- although there is a constant supply of new leaf litter and dead organic matter onto the soil surface, it is broken down very quickly because the warm, wet climate is ideal for micro-organisms.
- The growing season continues all year, so as soon as dead organic matter is broken down the nutrients are re-absorbed by plants. This means that few nutrients remain in the soil.
- Nutrients are also leached down the soil column by heavy rainfall.
There is a thin layer of nutrients in the top layer of soil, where organic matter is decaying. Trees keep their roots close to the surface in order to capitalise on these nutrients.
Organism Adaptations: Plants
- Plants are adapted to the heavy rainfall - they have thick, waxy leaves with pointed tips called drip tips, these channel the water so it runs off quickly and prevents fungi and bacteria growing on the leaves.
- Some plants e.g. anthurium have leaves that rotate to follow the sun.
- Tree trunks only have branches and leaves at the top of the canopy where they can absorb sunlight.
- Tall trees have big roots called buttress roots to keep them upright.
- The trees are deciduous - they drop their leaves throughout the year because there is no winter season.
- Lianas root in the soil and climb up trees, while epiphytes like orchids and bromeliads grow on the trees. These adaptations help the plants reach the light.
- Organisms such as bacteria and fungi are adapted to take nutrients form dead organic matter. There's lots of dead organic matter in the rainforest because of high rates of leaf fall. In return, these organisms make nutrients available to the other organisms in the ecosystem. The rainforest nutrient cycle depends on these species recycling nutrients, because the quality of the soil is so poor.
Organism Adaptations: Animals
- Many animals are adapted to living in the canopy because there's plenty of food there. For example, red eyed tree frogs have suction cups on their toes to help them climb trees.
- Jaguars, sloths and vampire bats are nocturnal - they save energy by hunting at night when it is cooler.
- Camouflage is an important way of avoiding predation.
- Some animals are adapted to the low light conditions in the undercanopy. Tapirs and anteaters have excellent senses of hearing and smell.
- Many rainforest animals can swim - this allows them to cope with flooding and cross river channels.
Human Activity
Deforestation is the biggest threat to tropical rainforests. There are many reasons why forests are being cut down which include: small scale farming, commercial logging, cattle farming and commercial agriculture. Deforestation can have dramatic social, environmental and economic impacts.
Environmental Impacts:
- habitat loss, reduced biodiversity
- increased surface run-off and flooding
- degradation of rainforest soil
- removal of nutrients from the ecosystem
- reduced evapotranspiration
- contributes towards global warming.
Social Impacts:
- increased jobs
- traditional livelihoods destroyed
- native tribes forced to move out
- conflict between natives, landowners mining and logging companies
Economic Impacts:
- logging, mining and farming create jobs
- a lot of money is made from timber, mining and farming
- long term depletion of resources on which countries rely on for economic stability.