World Biomes

Tropical Rain forest

Distribution of biome

• The tropical rainforest is found between 10 ° N and 10 ° S latitude at elevations below 1,000 m. There are three major, disjunct formations:

• Neotropical (Amazonia into Central America) • African (Zaire Basin with an outlier in West

Africa; also eastern Madagascar) • Indo- Malaysian (west coast of India, Assam,

southeast Asia, New Guinea and Queensland, Australia.

Distribution

Climate

• The tropical rainforest is a forest of tall trees in a region of year-round warmth. An average of 1250 to 6600 mm of rain falls yearly.

• The temperature in a rainforest rarely gets higher than 34 °C or drops below 20 °C; average humidity is between 77 and 88%. There is usually a brief season of less rain. In monsoonal areas, there is a real dry season. Almost all rainforests lie near the equator.

Soil• The soil is infertile, deeply

weathered and severely leached. Rapid bacterial decay prevents the accumulation of humus. The concentration of iron and aluminium oxides gives the soil a bright red colour and sometimes produces minable deposits (e.g., bauxite). On younger substrates, especially of volcanic origin, tropical soils may be quite fertile.

Plants I

• A tropical rainforest has more kinds of trees than any other area in the world. Scientists have counted about 100 to 300 species in one 1-hectare area in South America. Seventy percent of the plants in the rainforest are trees.

Plants II• All tropical rainforests resemble one another

in some ways. Many of the trees have straight trunks that don't branch out for 100 feet or more. There is no sense in growing branches below the canopy where there is little light. The majority of the trees have smooth, thin bark because there is no need to protect them from water loss and freezing temperatures. It also makes it difficult for epiphytes and plant parasites to get a hold on the trunks. The bark of different species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by their flowers.

Kapok tree

Brazil nut

Rubber tree

Ruffled Fan palm

Orchids

Bromeliad

Fern tree

Carnivorous plants

Pitcher plant or Monkey Cup

Venus Fly Trap

Plants III (growth forms)

• Epiphytes: the so-called air plants grow on branches high in the trees, using the limbs merely for support and extracting moisture from the air and trapping the constant leaf-fall and wind-blown dust.

Plants IV (growth forms)

• Lianas: woody vines grow rapidly up the tree trunks when there is a temporary gap in the canopy and flower and fruit in the tree tops.

Plants V (growth forms)• Climbers: green-

stemmed plants that remain in the understory. Many climbers, including the ancestors of the domesticated yams (Africa) and sweet potatoes (South America), store nutrients in roots and tubers.

Plants VI (growth forms)

• Stranglers: these plants begin life as epiphytes in the canopy and send their roots downward to the forest floor.

Fungi• Fungi can live on the forest floor because they

do not need sunlight for growth.

Plants VIII

• Rainforests now cover less than 6% of Earth's land surface. Scientists estimate that more than half of all the world's plant and animal species live in tropical rainforests. Tropical rainforests produce 40% of Earth's oxygen.

• About 1/4 of all the medicines we use come from rainforest plants. More than 1,400 varieties of tropical plants are thought to be potential cures for cancer.

Animals• Animal life is highly diverse. Common

characteristics found among mammals and birds (and reptiles and amphibians, too) include adaptations to an arboreal life (for example, the long tails of New World monkeys), bright colours and sharp patterns, loud vocalizations, and diets heavy on fruits.

Insects

Tree frogs

Constrictor Python

Chameleon

Amphibians and reptiles

Harpy Eagle

Macaw

Birds

Paradise bird

Mammals

Sloth Tapir

Howler Monkey

People I

People II• Farming: huge tracts of rainforest are cleared for

large-scale commercial plantations or livestock ranching. Ironically, rainforest soil is useless to humans. Rainforest soils are notoriously poor and cannot support human agriculture for more than a few years. Crops may grow well at first, mostly subsisting on the minerals released when the forest is burnt. But these minerals wash away quickly without the protection of the thick forest canopy and the soil soon becomes useless.

• Humans destroy by collecting and killing wild animals and plants.

People III• Rainforest is also cleared to make way for

homes for people, and infrastructure like dams, roads, electrical and communications installations.

• Rainforests are dug up as we mine for oil, gold and other minerals. Small scale gold prospectors use mercury which is toxic to extract gold.

People IV• Logging of trees for building materials,

firewood, paper products. Rainforests contain 50% of global standing timber. Unlike the faster-growing temperate timber trees, rainforest trees take decades to reach economic size so it is not easy to harvest them in a sustainable manner. Logging roads usually allow other commercial exploitation to follow.

People V

• Humans kill by breaking up a rainforest into smaller clumps. It destabilises the forest interior: temperature and humidity are no longer constant. Such fluctuations kill plants and animals adapted only for stable conditions. If the fragment is too small, it can't withstand natural seasonal changes. It also prevents natural movement of plants and animals from one part of the forest to another.