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The Tropical Rainforest Biome

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Key Feature of Tropical Rainforests Tropical Rainforests have more biodiversity (different kinds of species) than any biome on earth. About 75% of all animals species live in Tropical Rainforests. In one hectare (1 hm 2 ), there might be 807 trees which would represent 313 different tree species. In other words, if you walked over an area of a hectare, you would find only an average of 2.6 trees of the same kind. All the other 804 trees would be different.

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Tropical Rainforest Food Webs Tropical rainforests have extensive food webs which help to maintain stability as long as they are not disturbed.

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Largest Reservoir of Unclassified Species Tropical Rainforests have the largest number of unclassified species of any environment on earth. It is estimated that at least 1 million new species will be found in Tropical Rainforests if they survive and are explored.

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An Endangered Environment Tropical Rainforests are rapidly being exploited and deforested to raise crops and provide pastures for grazing animals. They are the most endangered environments as they are being rapidly destroyed for short term profits. Brazil lost a rainforest area larger than Greece from 2000-2006. By 2030, it is estimated that Brazils rainforest area will be further reduced by 40%.

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Location of Tropical Rainforests Tropical Rainforests are located within 28 of latitude from the equator.

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Climate Favouring Tropical Rainforests Tropical Rainforests form in climates with high average, even temperatures (18 C or more annual average) and high average, even rainfall (1750-2000 mm is typical but they can form with as little as 1680 mm or as much as 10 000 mm)

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Decomposition Rates in Tropical Rainforests Tropical Rainforests have rapid decomposition rates with wastes or dead organisms usually totally disappearing within a few days or weeks as scavengers and decomposers rapidly break down organic matter.

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Tropical Rainforest Soils Tropical Rainforest soils are called latosols. They are typically reddish or yellowish in colour due to the high degree of oxidation of iron compounds in the soil. Tropical rainforest soils are very nutrient poor (rapid decomposition of organic matter prevents humus formation), typically do not develop horizon structure, and can be very deep.

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Highly Competitive Organisms Because there are so many different kinds of organisms in a Tropical rainforests, there is much competition for food.

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Very Specialized Organisms In order to reduce their competition over against other species, Tropical rainforest species tend to be highly specialized to obtain a very particular food item, not of value to other species. Biologists use the term, niche, to refer to what an organism does to stay alive its profession. Tropical rainforest organisms have very specialized niches, very unique ways of feeding, reproducing and staying alive. The orchid mantis mimicks orchid flowers and catches insects lured to it. The koala eats mostly eucalyptus leaves, poisonous to most other organisms.

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Examples of Specialized Rainforest Organisms Pygmy gliders are small, nocturnal opossums which feed on insects, sap, buds, pollen and nectar. They use flaps of skin to glide up to 25 m.

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Examples of Specialized Rainforest Organisms Swan-sized Rhinoceros hornbill birds feed on fruits, insects and rodents. After mating, the female finds a hollow tree and the male seals up the hole with mud and dung. The female incubates the eggs inside the tree while being fed by the male through a small hole or slit which the female also uses to defecate through. The young and mother are fed by the male until they are old enough to make it on their own.

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Examples of Specialized Rainforest Organisms Glow worms are not worms but larvae of a mosquito-like fly. They build silken thread covered with mucous that can trap insects which they feed on. To lure insects, they produce a bluish light using a chemical called luciferin, an enzyme and an energy compound.

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Examples of Specialized Rainforest Organisms Epiphytes or air plants are common in tropical rainforests. These plants grow on other plants and have aerial roots which absorb water and a few nutrients from the air or the plant they are on. They are not parasitic, not harming the plants they grow on. Orchids and Spanish moss are epiphytes.

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Biomass Location in Tropical Rainforests Unlike most environments, a Tropical rainforests biomass (total mass of organic matter in living organisms, their wastes and dead remains) is 99.9 % in the living organisms with virtually none in wastes or dead remains. Contrast this to a temperate rainforest which may have as much as 40% of its biomass is in decomposing materials on the forest floor.

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Forest Structure of a Tropical Rainforest Tropical rainforests are highly stratified into four distinct layers. There is an upper canopy, an understory, an emergent layer above the canopy, a shrub layer and perhaps a herb or ground cover layer.

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The Emergent Layer The emergent layer is made up of very tall trees about 70-80 m tall. To maintain their stability, these tall trees often have cone-like buttress roots which help to prop the trees and keep them upright.

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The Canopy Layer The Canopy layer (from height of 3 m (10 ft) to 30 r 45 m tall) of a tropical rainforests contains most of the organisms living in a rainforest. Many of the epiphytes with aerial roots living on trees but not harming them are found in this layer.

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The Understory Layer This layer of the tropical rainforest includes small trees and bushes from 1m-3m tall. This layer is in shade (gets 5% of sunlight) so many plants in this layer have large flat leaves to absorb as much sunlight as possible. Predators in this layer include boa constrictors and cats like the jaguar, panther, mountain lion and tiger.

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The Rainforest Floor This layer often has few plants since the light is so dim (about 2% of sunlight at the top of the rainforest) at the floor level of a tropical rainforest. Organisms may be spotted for camoflage. Large leaves are a plant adaptation to capture the little sunlight falling on this area.

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Pharmaceutical Value of Rainforests More than a quarter of all natural medicines come from Tropical rainforests. Scientists are concerned that the present rainforest destruction will rob future generations of many medicines that remain to be discovered in the plants and animals of tropical rainforests.

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Pharmaceuticals from Rainforests Two-thirds of all cancer fighting medicines have come plants in tropical rainforests. One-half of all known plant species are found in tropical rainforests. 1 mi 2 in a tropical rainforest would have 1,500 flowering plant species and 750 tree species. 120 prescription drugs are compounds that have come from tropical rainforest plants.

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Pharmaceuticals from Rainforests A unique periwinkle species from Madagascar rainforests has a compound that has increased leukemia survival from 20% to 80%. Unfortunately this periwinkle species has gone extinct due to deforestation. Compounds from rainforest plants today are used to treat malaria, heart disease, bronchitis, hypertension, rheumatism, diabetes, arthritis, glaucoma, dysentery and tuberculosis.

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Just the Tip of the Iceberg What pharmaceuticals scientists have discovered in tropical rainforest plants is just the tip of the iceberg of useful medicinal compounds that may be discovered if tropical rainforests survive their present destruction by human developers.

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Tropical Rainforest Animals Tropical Rainforest parrots have tough beaks for cracking and eating seeds and fruits.

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Tropical Rainforest Animals Slow moving sloths feed mostly on leaves and buds of the cecropia tree. They spend most of their lives in the rainforest canopy.

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Tropical Rainforest Animals The jaguar is a predator of the forest floor and understory layer. The patterened coat of the jaguar helps to camouflage it in the shady layers it roams.

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Tropical Rainforest Animals Tapirs are pig-sized herbivores. They have long prehensile snouts that they use to grasp bushes out of reach.

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Tropical Rainforest Animals The okapi is a congo rainforest animal that is related to giraffes and has a coat with markings similar to a zebra. It has a long tongue used to strip buds and leaves from understory bushes and trees.

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Tropical Rainforest Animals African rainforest gorillas are herbivores and live together in groups called troops. Tourist being groomed

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Tropical Rainforest Animals Anacondas are the worlds largest snakes which can reach lengths of over 22 ft and whose mouths and bodies expand to eat prey much larger than themselves.

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Tropical Rainforest Plants Mohagany trees are cut for their lumber used for paneling or furniture.

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Tropical Rainforest Plants Teak trees are valued for their lumber which is weather resistant and has been used for outdoor furniture as well as indoor furniture.

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Tropical Rainforest Plants Brazil nut trees are South American rainforest trees that are in the emergent layer. They produce pods with shelled seeds from which the nuts are taken.

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Tropical Rainforest Plants Banana plants are the largest flowering herbaceous plants. They are not woody trees. The fruit of a banana plant is technically a berry. In the rainforest they would be in the understory layer.

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Tropical Rainforest Plants Orchids are epiphytes found in tropical rain forests. Their unusual and colourful shapes sometimes mimic their pollinators.

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Tropical Rainforest Plants Rafflesia is a parasitic plant whose only visible part is large flowers over 1 m across. They look and smell like decaying flesh so they attract flies as pollinators. The stench of the flower has been said to be almost strong enough to make a person pass out.

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Tropical Rainforest Plants The amazon rainforest has giant lily pads that can support the weight of a small person. Victoria water lilies can be up to 3 m across with stalks going 8 m deep to the river bed.

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