Tropical rainforest

Tropical rainforest

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A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator (in the equatorial zone between the Tropic of Cancer
Tropic of Cancer
The Tropic of Cancer, also referred to as the Northern tropic, is the circle of latitude on the Earth that marks the most northerly position at which the Sun may appear directly overhead at its zenith...

 and Tropic of Capricorn
Tropic of Capricorn
The Tropic of Capricorn, or Southern tropic, marks the most southerly latitude on the Earth at which the Sun can be directly overhead. This event occurs at the December solstice, when the southern hemisphere is tilted towards the Sun to its maximum extent.Tropic of Capricorn is one of the five...

). This ecosystem experiences high average temperatures and a significant amount of rainfall. Rainforests can be found in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 and on many of the Pacific, Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

, and Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 islands. Within the World Wildlife Fund's biome classification, tropical rainforests are thought to be a type of tropical wet forest (or tropical moist broadleaf forest) and may also be referred to as lowland equatorial evergreen rainforest.

Overview


Tropical rainforests are characterized in two words: warm and wet. Mean monthly temperatures exceed 18 °C (64.4 °F) during all months of the year. Average annual rainfall is no less than 67 inches (30 m) and can exceed 400 inches (1,016 cm), although it typically lies between 175 cm (68.9 in) and 200 cm (78.7 in).
. This high level of precipitation often results in poor soils due to leaching of soluble nutrients.

Tropical rainforests are unique in the high levels of biodiversity they exhibit. Around 40% to 75% of all biotic species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 are indigenous
Indigenous (ecology)
In biogeography, a species is defined as native to a given region or ecosystem if its presence in that region is the result of only natural processes, with no human intervention. Every natural organism has its own natural range of distribution in which it is regarded as native...

 to the rainforests. Rainforests are home to half of all the living animal and plant species on the planet. Two-thirds of all flowering plants can be found in rainforests. A single hectare of rainforest may contain 42,000 different species of insect, up to 807 trees of 313 species and 1,500 species of higher plants. Tropical rainforests have been called the "jewels of the Earth" and the "world's largest pharmacy
Pharmacy
Pharmacy is the health profession that links the health sciences with the chemical sciences and it is charged with ensuring the safe and effective use of pharmaceutical drugs...

", because over one quarter of natural medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

s have been discovered within them. It is likely that there may be many millions of species of plants, insects and microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s still undiscovered in tropical rainforests.

Tropical rainforests are among the most threatened ecosystems globally due to large-scale fragmentation
Fragmentation
-In biology:* Fragmentation , a form of asexual reproduction* Fragmentation * Habitat fragmentation* Population fragmentation-Music:* Fragmented , the debut album from the Filipino independent band Up Dharma Down-Other:...

 due to human activity. Habitat fragmentation
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...

 caused by geological processes such as volcanism and climate change occurred in the past, and have been identified as important drivers of speciation. However, fast human driven habits destruction is suspected to be one of the major causes of species extinction.
Tropical rain forests have been subjected to heavy logging
Logging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...

 and agricultural clearance
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....

 throughout the 20th century, and the area covered by rainforests around the world is rapidly shrinking.

History


Tropical rainforests have existed on Earth for hundreds of millions of years. Most tropical rainforests today are on fragments of the Mesozoic era
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

 supercontinent of Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...

. The separation of the landmass resulted in a great loss of amphibian diversity while at the same time the drier climate spurred the diversification of reptiles. The division left tropical rainforests located in five major regions of the world: tropical America, Africa, Southeast Asia, Madagascar, and New Guinea, with smaller outliers in Australia. However, the specifics of the origin of rainforests remain uncertain due to an incomplete fossil record.

Types of Tropical Rainforest


Several types of forest comprise the general tropical rainforest biome:
  • Lowland equatorial evergreen rain forests are forests which receive high rainfall (more than 2000 mm, or 80 inches, annually) throughout the year. These forests occur in a belt around the equator, with the largest areas in the Amazon Basin
    Amazon Basin
    The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

     of South America, the Congo Basin
    Congo Basin
    The Congo Basin is the sedimentary basin that is the drainage of the Congo River of west equatorial Africa. The basin begins in the highlands of the East African Rift system with input from the Chambeshi River, the Uele and Ubangi Rivers in the upper reaches and the Lualaba River draining wetlands...

     of Central Africa
    Central Africa
    Central Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda....

    , Indonesia
    Indonesia
    Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

    , and New Guinea
    New Guinea
    New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

    .

  • Moist deciduous and semi-evergreen seasonal forests, receive high overall rainfall with a warm summer wet season and a cooler winter dry season. Some trees in these forests drop some or all of their leaves during the winter dry season. These forests are found in parts of South America, in Central America
    Central America
    Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

     and around the Caribbean
    Caribbean
    The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

    , in coastal West Africa
    West Africa
    West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...

    , parts of the Indian subcontinent
    Indian subcontinent
    The Indian subcontinent, also Indian Subcontinent, Indo-Pak Subcontinent or South Asian Subcontinent is a region of the Asian continent on the Indian tectonic plate from the Hindu Kush or Hindu Koh, Himalayas and including the Kuen Lun and Karakoram ranges, forming a land mass which extends...

    , and across much of Indochina
    Indochina
    The Indochinese peninsula, is a region in Southeast Asia. It lies roughly southwest of China, and east of India. The name has its origins in the French, Indochine, as a combination of the names of "China" and "India", and was adopted when French colonizers in Vietnam began expanding their territory...

    .

  • Montane rain forests, some of which are known as cloud forest
    Cloud forest
    A cloud forest, also called a fog forest, is a generally tropical or subtropical evergreen montane moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level. Cloud forests often exhibit an abundance of mosses covering the ground and...

    s, are found in cooler-climate mountain areas. Depending on latitude, the lower limit of montane rainforests on large mountains is generally between 1500 and 2500 m while the upper limit is usually from 2400 to 3300 m.

  • Flooded forests, seven types of flooded forest are recognized for Tambopata
    Tambopata
    Tambopata can refer to any of the following entities:*Tambopata Province in the department of Madre de Dios in south-eastern Peru*Tambopata River, a tributary to the Madre de Dios River*Tambopata-Candamo reserve, adjacent to the Tambopata River...

     Reserve in Amazonian Peru:
    • Permanently waterlogged swamp forest--Former oxbow lakes still flooded but covered in forest.
    • Seasonally waterlogged swamp forest--Oxbow lakes in the process of filling in.
    • Lower floodplain forest--Lowest floodplain locations with a recognizable forest.
    • Middle floodplain forest--Tall forest, flooded occasionally.
    • Upper floodplain forest--Tall forest, rarely flooded.
    • Old floodplain forest--Subjected to flooding within the last two hundred years.
    • Previous floodplain--Now terra firme, but historically ancient floodplain of Tambopata River.

Forest Structure


Rainforests are divided into different strata, or layers, with vegetation organized into a vertical pattern from the top of the soil to the canopy Each layer is comprised of a unique biotic community containing different plants and animals adapted for life in that particular strata. Only the emergent layer is unique to tropical rainforests, while the others are also found in temperate rainforests.

Forest Floor



The forest floor, the bottom-most layer, receives only 2% of the sunlight. Only plants adapted
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

 to low light can grow in this region. Away from riverbanks, swamps and clearings, where dense undergrowth is found, the forest floor is relatively clear of vegetation because of the low sunlight penetration. This more open quality permits the easy movement of larger animals such as: ungulates like the okapi
Okapi
The okapi , Okapia johnstoni, is a giraffid artiodactyl mammal native to the Ituri Rainforest, located in the northeast of the Democratic Republic of the Congo, in Central Africa...

 (Okapia johnstoni), tapir
Tapir
A Tapir is a large browsing mammal, similar in shape to a pig, with a short, prehensile snout. Tapirs inhabit jungle and forest regions of South America, Central America, and Southeast Asia. There are four species of Tapirs: the Brazilian Tapir, the Malayan Tapir, Baird's Tapir and the Mountain...

 (Tapirus sp.), Sumatran rhinoceros
Sumatran Rhinoceros
The Sumatran Rhinoceros is a member of the family Rhinocerotidae and one of five extant rhinoceroses. It is the only extant species of the genus Dicerorhinus. It is the smallest rhinoceros, although is still a large mammal. This rhino stands high at the shoulder, with a head-and-body length of ...

 (Dicerorhinus sumatrensis), and apes like the western lowland gorilla
Western Lowland Gorilla
The western lowland gorilla is a subspecies of the western gorilla that lives in montane, primary, and secondary forests and lowland swamps in Angola, Cameroon, Central African Republic, Congo, Democratic Republic of the Congo, Equatorial Guinea and Gabon. It is the gorilla usually found in zoos...

 (Gorilla gorilla), as well as many species of reptiles, amphibians, and insects. The understory also contains decay
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...

ing plant and animal matter, which disappears quickly, because the warm, humid conditions promote rapid decay. Many forms of fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 growing here help decay the animal and plant waste.

Understory Layer



The understory layer lies between the canopy and the forest floor. The understory is home to a number of birds, small mammals, insects, reptiles, and predators. Examples include leopard
Leopard
The leopard , Panthera pardus, is a member of the Felidae family and the smallest of the four "big cats" in the genus Panthera, the other three being the tiger, lion, and jaguar. The leopard was once distributed across eastern and southern Asia and Africa, from Siberia to South Africa, but its...

 (Panthera pardus), piranha
Piranha
A piranha or piraña is a member of family Characidae in order Characiformes, an omnivorous freshwater fish that inhabits South American rivers. In Venezuela, they are called caribes...

 (Pygocentrus nattereri), poison dart frogs
Poison dart frog
Poison dart frog is the common name of a group of frogs in the family Dendrobatidae which are native to Central and South America. These species are diurnal and often have brightly-colored bodies...

 (Dendrobates sp.), ring-tailed coati
South American Coati
The South American Coati, or Ring-tailed Coati , is a species of coati from South America. In Brazilian Portuguese it is known as quati. It is native to Argentina, Bolivia, Brazil, Colombia, Ecuador, Guyana, Paraguay, Peru, Surinam, Uruguay and Venezuela. It is the southern replacement of its very...

 (Nasua nasua), boa constrictor
Boa constrictor
The Boa constrictor is a large, heavy-bodied species of snake. It is a member of the family Boidae found in North, Central, and South America, as well as some islands in the Caribbean. A staple of private collections and public displays, its color pattern is highly variable yet distinctive...

 (Boa constrictor), and many species of Coleoptera
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...

.. The vegetation at this layer generally consists of shade-tolerant shrubs, herbs, small trees, and large woody vines which climb into the trees to capture sunlight. Only about 5% of sunlight breaches the canopy to arrive at the understory causing true understory plants to seldom grow to 3 m (10 feet). As an adaptation to these low light levels, understory plants have often evolved much larger leaves. Many seedlings that will grow to the canopy level are in the understory


Canopy Layer



The canopy is the primary layer of the forest forming a roof over the two remaining layers. It contains the majority of the largest trees, typically 30–45 m in height. Tall, broad-leaved evergreen trees are the dominant plants. The densest areas of biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

 are found in the forest canopy, as it often supports a rich flora of epiphytes, including orchids, bromeliads, mosses, and lichens. These epiphytic plants attach to trunks and branches and obtain water and minerals from rain and debris that collects on the supporting plants. The fauna is similar to that found in the emergent layer, but more diverse. It is suggested that the total arthropod species richness of the tropical canopy might be as high as 20 million. Other species habituating this layer include many avian species such as the yellow-casqued wattled hornbill (Ceratogymna elata), collared sunbird
Collared Sunbird
The Collared Sunbird, Hedydipna collaris , is a sunbird. The sunbirds are a group of very small Old World passerine birds which feed largely on nectar, although they will also take insects, especially when feeding young. Collared Sunbird is in fact mainly insectivorous.Sunbird flight is fast and...

 (Anthreptes collaris), African gray parrot (Psitacus erithacus), keel-billed toucan
Keel-billed Toucan
The Keel-billed Toucan , also known as Sulfur-breasted Toucan or Rainbow-billed Toucan, is a colorful Latin American member of the toucan family. It is the national bird of Belize.- Description :...

 (Ramphastos sulfuratus), scarlet macaw
Scarlet Macaw
The Scarlet Macaw is a large, colorful macaw. It is native to humid evergreen forests in the American tropics. Range extends from extreme south-eastern Mexico to Amazonian Peru, Bolivia and Brazil in lowlands up to up to...

 (Ara macao) as well as other animals like the spider monkey
Spider monkey
Spider monkeys of the genus Ateles are New World monkeys in the subfamily Atelinae, family Atelidae. Like other atelines, they are found in tropical forests of Central and South America, from southern Mexico to Brazil...

 (Ateles sp.), African giant swallowtail (Papilio antimachus
Papilio antimachus
Papilio antimachus is a butterfly in the family Papilionidae. With a wingspan between , it is the largest butterfly in Africa and among the largest butterflies in the world. Papilio antimachus live in the tropical rainforests of West and Central Africa...

), three-toed sloth
Three-toed sloth
The three-toed sloths are tree-living mammals from South and Central America. They are the only members of the genus Bradypus and the family Bradypodidae. There are four living species of three-toed sloths...

 (Bradypus tridactylus), kinkajou
Kinkajou
The kinkajou , also known as the honey bear , is a rainforest mammal of the family Procyonidae related to olingos, coatis, raccoons, and the ringtail and cacomistle. It is the only member of the genus Potos. Kinkajous may be mistaken for ferrets or monkeys, but are not closely related...

 (Potos flavus), and tamandua
Tamandua
Tamandua is a genus of anteaters. It has two members: the Southern Tamandua and the Northern Tamandua . They live in forests and grasslands, are semi-arboreal, and possess partially prehensile tails. They mainly eat ants and termites, but they occasionally eat bees, beetles, and insect larvae...

 (Tamandua tetradactyla).

Emergent Layer


The emergent layer contains a small number of very large trees, called emergents, which grow above the general canopy
Canopy (forest)
In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...

, reaching heights of 45–55 m, although on occasion a few species will grow to 70–80 m tall. Some examples of emergents include: Balizia elegans, Dipteryx panamensis, Hieronyma alchorneoides, Hymenolobium mesoamericanum, Lecythis ampla and Terminalia oblonga. These trees need to be able to withstand the hot temperatures and strong winds that occur above the canopy in some areas. Several unique faunal species inhabit this layer such as the crowned eagle
Crowned Eagle
The Crowned Eagle or Crowned Hawk-eagle , is a very large, powerful, crested bird of prey found in sub-Saharan Africa; in Southern Africa it is restricted to suitable habitat in the eastern areas. It is the only extant member of the genus Stephanoaetus...

 (Stephanoaetus coronatus), the king colobus
King Colobus
The king colobus , also known as the western black-and-white colobus, is a species of Old World monkey, found in lowland and mountain rain forests in a region stretching between Gambia and Côte d'Ivoire within Africa. It eats mainly leaves, but also fruits and flowers. Though it is arboreal, it...

 (Colobus polykomos), and the large flying fox
Large Flying Fox
The Large Flying Fox , also known as the Greater Flying Fox, Malaysian Flying Fox, Kalang or Kalong, is a species of megabat in the family Pteropodidae. Like the other members of the genus Pteropus, or the Old World fruit bats, it feeds exclusively on fruits. It is noted for being the largest...

 (Pteropus vampyrus).

However, stratification is not always clear. Rainforests are dynamic and many changes affect the structure of the forest. Emergent or canopy trees collapse, for example, causing gaps to form. Openings in the forest canopy are widely recognized as important for the establishment and growth of rainforest trees. It’s estimated that perhaps 75% of the tree species at La Selva Biological Station, Costa Rica are dependent on canopy opening for seed germination or for growth beyond sapling size, for example.

Climate


Most tropical rainforests are located around or near the equator, thus having what is termed an equatorial climate characterized by three major climatic parameters: temperature, rainfall, and dry season intensity Other parameters that effect tropical rainforests are carbon dioxide concentrations, solar radiation, and nitrogen availability. In general, climatic patterns consist of warm temperatures and high annual rainfall. However, the abundance of rainfall changes throughout the year creating distinct wet and dry seasons. Rainforests are classified by the amount of rainfall received each year, which has allowed ecologists to define differences in these forests that look so similar in structure. According to Holdbridge’s classification of tropical ecosystems, true tropical rainforests have an annual rainfall greater than 800 cm and annual temperature greater than 24 degrees Celsius. However, most lowland tropical rainforests can be classified as tropical moist or wet forests, which differ in regards to rainfall. Tropical rainforest ecology- dynamics, composition, and function- are sensitive to changes in climate especially changes in rainfall. The climate of these forests is controlled by a band of clouds called the Intertropical Convergence Zone
Intertropical Convergence Zone
The Intertropical Convergence Zone , known by sailors as The Doldrums, is the area encircling the earth near the equator where winds originating in the northern and southern hemispheres come together....

 located near the equator and created by the convergence of the trade winds from the northern and southern hemispheres. The position of the band varies seasonally, moving north in the northern summer and south in the northern winter, and ultimately controlling the wet and dry seasons in the tropics.
These regions have experienced strong warming at a mean rate of 0.26 degrees Celsius per decade which coincides with a global rise in temperature resulting from the anthropogenic inputs of greenhouse gases into the atmosphere. Studies have also found that precipitation has declined and tropical Asia has experienced an increase in dry season intensity where as Amazonia has no significant pattern change in precipitation or dry season. Additionally, El Niño-Southern Oscillation
El Niño-Southern Oscillation
El Niño/La Niña-Southern Oscillation, or ENSO, is a quasiperiodic climate pattern that occurs across the tropical Pacific Ocean roughly every five years...

 events drive the interannual climatic variability in temperature and precipitation and result in drought and increased intensity of the dry season. As anthropogenic warming increases the intensity and frequency of ENSO will increase, leaving tropical rainforest regions susceptible to stress and increased mortality of trees.


Soil Types


Soil types are highly variable in the tropics and are the result of a combination of several variables such as climate, vegetation, topographic position, parent material, and soil age Most tropical soils are characterized by significant leaching
Leaching
In general, leaching is the extraction of certain materials from a carrier into a liquid . Specifically, it may refer to:...

 and poor nutrients; however there are some areas that contain fertile soils. Soils throughout the tropical rainforests fall into two classifications which include the ultisols
Ultisols
Ultisols, commonly known as red clay soils, are one of twelve soil orders in the United States Department of Agriculture soil taxonomy. They are defined as mineral soils which contain no calcareous material anywhere within the soil, have less than 10% weatherable minerals in the extreme top layer...

 and oxisols. Ultisols are known as well weathered, acidic red clay soils, deficient in major nutrients such as calcium and potassium. Similarly, oxisols are acidic, old, typically reddish, highly weathered and leached, however are well drained compared to ultisols. The clay content of ultisols is high, making it difficult for water to penetrate and flow through. The reddish color of both soils is the result of heavy heat and moisture forming oxides of iron and aluminum, which are insoluble in water and not taken up readily by plants.

Soil chemical and physical characteristics are strongly related to above ground productivity and forest structure and dynamics. The physical properties of soil control the tree turnover rates where as chemical properties such as available nitrogen and phosphorus control forest growth rates. The soils of the eastern and central Amazon as well as the Southeast Asian Rainforest are old and mineral poor where as the soils of the western Amazon (Ecuador and Peru) and volcanic areas of Costa Rica are young and mineral rich. Primary productivity or wood production is highest in western Amazon and lowest in eastern Amazon which contains heavily weathered soils classified as oxisols. Additionally, Amazonian soils greatly weathered, making them devoid of minerals like phosphorus, potassium, calcium, and magnesium, which come from rock sources. However, not all tropical rainforests occur on nutrient poor soils, but on nutrient rich floodplains and volcanic soils located in the Andean foothills, and volcanic areas of Southeast Asia, Africa, and Central America.

Nutrient Recycling


The soils of tropical rainforests are characterized by rapid recycling of fallen leaves and other organic matter due to the large biomass of the rainforest. This high rate of decomposition is the result of phosphorus levels in the soils, precipitation, high temperatures and the extensive microorganism communities. In addition to the bacteria and other microorganisms, there are an abundance of other decomposers
Decomposer
Decomposers are organisms that break down dead or decaying organisms, and in doing so carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and...

 such as fungi and termites that aid in the process as well. Nutrient recycling is important because below ground resource availability controls the above ground biomass and community structure of tropical rainforests. These soils are typically phosphorus limited, which inhibits net primary productivity or the uptake of carbon. The soil contains tiny microbial organisms such as bacteria, which breakdown leaf litter and other organic matter into inorganic forms of carbon usable by plants through a process called decomposition. During the decomposition process the microbial community is respiring, taking up oxygen and releasing carbon dioxide. The decomposition rate can be evaluated by measuring the uptake of oxygen. High temperatures and precipitation increase decomposition rate, which allows plant litter to rapidly decay in tropical regions, releasing nutrients that are immediately taken up by plants through surface or ground waters. The seasonal patterns in respiration are controlled by leaf litter fall and precipitation, the driving force moving the decomposable carbon from the litter to the soil. Respiration rates are highest early in the wet season because the recent dry season results in a large percentage of leaf litter and thus a higher percentage of organic matter being leached into the soil.

Buttress Roots


A common feature of many tropical rainforests is the distinct buttress roots of trees. Instead of penetrating to deeper soil layers, buttress roots create a wide spread root network at the surface for more efficient uptake of nutrients in a very nutrient poor and competitive environment. Most of the nutrients within the soil of a tropical rainforest occur near the surface because of the rapid turnover time and decomposition of organisms and leaves. Because of this, the buttress roots occur at the surface so the trees can maximize uptake and actively compete with the rapid uptake of other trees. These roots also aid in water uptake and storage, increase surface area for gas exchange, and collect leaf litter for added nutrition. Additionally, these roots reduce soil erosion and maximize nutrient acquisition during heavy rains by diverting nutrient rich water flowing down the trunk into several smaller flows while also acting as a barrier to ground flow. Also, the large surface areas these roots create provide support and stability to rainforests trees, which commonly grow to significant heights. This added stability allows these trees to withstand the impacts of severe storms, thus reducing the occurrence of fallen trees.

Carbon Flux


Carbon flux can be defined as the exchange of carbon dioxide between the atmosphere and a sink. Net primary productivity, an important ecological concept, can be defined as the amount of carbon retained in plant biomass over time. It is also the difference between gross primary productivity and autotrophic respiration and is used to measure the amount of carbon within a rainforest. The importance of rainforests in the carbon cycle depends on the above and below ground (root systems and soil organic matter) biomass, amount of carbon stored, and the rate at which it is fixed by plants through photosynthesis. Compared to other forest types, tropical rainforests are known to be significant carbon sinks, absorbing 4.8 billion tons of carbon dioxide every year. The rainforests of Amazonia contain between 14 and 40 kilograms of carbon per square meter and the soils contain 27% of the carbon in roots, microorganisms, soil fungi and plants.

Forest Succession


Succession
Ecological succession
Ecological succession, is the phenomenon or process by which a community progressively transforms itself until a stable community is formed. It is a fundamental concept in ecology, and refers to more or less predictable and orderly changes in the composition or structure of an ecological community...

 is an ecological process that changes the biotic community structure over time towards a more stable, diverse community structure after an initial disturbance to the community. The initial disturbance is often a natural phenomenon or human caused event. Natural disturbances include hurricanes, volcanic eruptions, river movements or an event as small as a fallen tree that creates gaps in the forest. In tropical rainforests, these same natural disturbances have been well documented in the fossil record, and are credited with encouraging speciation and endemism.

South & Central America

  • Amazon Rainforest
    Amazon Rainforest
    The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...

  • Atlantic Forest
  • Central American Atlantic Moist Forest

Africa

  • Atlantic Equatorial Coastal Forest
  • Ituri Rainforest
    Ituri Rainforest
    The Ituri Rainforest is a rainforest located in the Ituri region of eastern Democratic Republic of the Congo formerly called Zaire. The forest's name derives from the nearby Ituri River which flows through the rainforest, connecting firstly to the Aruwimi River and finally into the Congo.-...

  • Kilum-Ijim Forest
    Kilum-Ijim Forest
    The Kilum-Ijim Forest is an area of mountain rainforest in Cameroon's North-West Region. It is found on Mount Oku and the nearby Ijim Ridge in the Cameroon mountains, with Lake Oku lying in a crater in its center. It is the largest area of Afromontane forest left in West Africa. The area is an...

  • Madagascar lowland forests
    Madagascar lowland forests
    The Madagascar lowland forests are a tropical moist broadleaf forest ecoregion, found on the eastern coast of the island of Madagascar.-Setting:...


Asia

  • Sulawesi Lowland Rainforest
  • Borneo Lowland Rainforest
  • Palawan Rainforest
  • Harapan Rainforest
    Harapan Rainforest
    Harapan Rainforest is first restoration area of dry lowland rainforest in Sumatra, Indonesia. This area are covers 98,554 hectares of previously logged forest and is being managed for forest restoration with a view to returning the whole of the forest to its original condition.-Site...


Australasia & Oceania

  • Daintree Rainforest
    Daintree Rainforest
    The Daintree Rainforest is a tropical rainforest on the north east coast of Queensland, Australia, north of Mossman and Cairns. At around 1200 square kilometres the Daintree is the largest continuous area of tropical rainforest on the Australian continent...

  • Huon Peninsula Montane Rainforest
  • Hawaiian tropical rainforests

Biodiversity and Speciation



Tropical rainforests exhibit a vast diversity in plant and animal species. The root for this remarkable speciation has been a query of scientists and ecologists for years. A number of theories have been developed for why and how the tropics can be so diverse.

Interspecific Competition Hypothesis


The Interspecific Competition Hypothesis
Interspecific competition
Interspecific competition, in ecology, is a form of competition in which individuals of different species compete for the same resource in an ecosystem...

suggests that because of the high density of species with similar niches in the tropics and limited resources available, they must do one of two things: go extinct or find a new niche. Direct competition will often lead to one species dominating another by some advantage, ultimately driving it to extinction. Niche partitioning is the other option for a species. This is the separation and rationing of necessary resources by utilizing different habitats, food sources, cover or general behavioral differences. A species with similar food items but different feeding times is an example of niche partitioning.

Pleistocene Refugia


The Theory of Pleistocene Refugia
Refugium
Refugium may refer to:* Refugium , an appendage to a marine, brackish, or freshwater fish tank that shares the same water supply...

 was developed by Jürgen Haffer
Jürgen Haffer
Jürgen Haffer was a German ornithologist, biogeographer, and geologist. He is most remembered for his theory of Amazonian forest refugia during the Pleistocene that would have contributed to speciation and the diversification of the biota.At the age of 13 he had found a dead bird with a ring and...

 in 1969 with his article Speciation of Amazonian Forest Birds. Haffer proposed the explanation for speciation was the product of rainforest patches being separated by stretches of non forest vegetation during the last glacial period. He called these patches of rainforest areas refuges and within these patches allopatric speciation occurred. With the end of the glacial period and increase in atmospheric humidity, rainforest began to expand and the refuges reconnected.
This theory has been the subject of debate. Scientists are still skeptical if whether or not this theory is legitimate. Genetic evidence suggests speciation had occurred in certain taxa 1-2 million years ago, preceding the Pleistocene. . This argument has been replicated and demonstrated with additional publications.

Habitation


Tropical rainforests are unable to support human life. Food resources within the forest are extremely dispersed due to the high biological diversity and what food does exist is largely restricted to the canopy and requires considerable energy to obtain. Some groups of hunter-gatherers have exploited rainforest on a seasonal basis but dwelt primarily in adjacent savanna and open forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

 environments
Environment (biophysical)
The biophysical environment is the combined modeling of the physical environment and the biological life forms within the environment, and includes all variables, parameters as well as conditions and modes inside the Earth's biosphere. The biophysical environment can be divided into two categories:...

 where food is much more abundant. Other peoples described as rainforest dwellers are hunter-gatherers who subsist in large part by trading high value forest products such as hides, feathers, and honey with agricultural people living outside the forest.

Indigenous Peoples



A variety of indigenous people live within deforested patches of rainforest, or subsist as part time farmer supplemented in large part by trading high value forest products such as hides, feathers, and honey with agricultural people living outside the forest. People have inhabited the rainforests for thousands of years and have remained so elusive that only recently have some tribes been discovered. On January 18, 2007, FUNAI
Fundação Nacional do Índio
Fundação Nacional do Índio or FUNAI is a Brazilian governmental protection agency for Indian interests and their culture.It was originally called the SPI and was founded by the Brazilian Marshal Cândido Rondon in 1910, who also created the agency's motto, "Die if necessary, but never kill." The...

 reported also that it had confirmed the presence of 67 different uncontacted tribes
Uncontacted peoples
Uncontacted people, also referred to as isolated people or lost tribes, are communities who live, or have lived, either by choice or by circumstance, without significant contact with globalized civilisation....

 in Brazil, up from 40 in 2005. With this addition, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 has now overtaken the island of New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

 as the country having the largest number of uncontacted tribes. The province of Irian Jaya or West Papua in the island of New Guinea is home to an estimated 44 uncontacted tribal groups.

The pygmy peoples are hunter-gatherer groups living in equatorial rainforests characterized by their short height (below one and a half meters, or 59 inches, on average). Amongst this group are the Efe, Aka, Twa
Twa
The Twa are any of several hunting peoples of Africa who live interdependently with agricultural Bantu populations, and generally hold a socially subordinate position: They provide the farming population with game in exchange for agricultural products....

, Baka
Baka
Baka may refer to:in fictional characters* Bākā, a character from Juken Sentai Gekiranger* Baka Rangers, a group of Negima! Magister Negi Magi characters...

, and Mbuti
Mbuti
Mbuti or Bambuti are one of several indigenous pygmy groups in the Congo region of Africa. Their languages belong to the Central Sudanic and also to Bantu languages.-Overview:...

 people of Central Africa. However, the term pygmy is considered pejorative so many tribes prefer not to be labeled as such.

Some notable indigenous peoples of the Americas
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...

, or Amerindians, include the Huaorani
Huaorani
The Huaorani, Waorani or Waodani, also known as the Waos, are native Amerindians from the Amazonian Region of Ecuador who have marked differences from other ethnic groups from Ecuador. The alternate name Auca is a pejorative exonym used by the neighboring Quechua Indians, and commonly adopted by...

, Ya̧nomamö, and Kayapo people of the Amazon
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

. The traditional agricultural system practiced by tribes in the Amazon is based on swidden cultivation (also known as slash-and-burn or shifting cultivation) and is considered a relatively benign disturbance. In fact, when looking at the level of individual swidden plots a number of traditional farming practices are considered beneficial. For example, the use of shade trees and fallowing all help preserve soil organic matter, which is a critical factor in the maintenance of soil fertility in the deeply weathered and leached soils common in the Amazon.

There is a diversity of forest people in Asia, including the Lumad
Lumad
The Lumad is a term being used to denote a group of indigenous peoples of the southern Philippines. It is a Cebuano term meaning "native" or "indigenous"...

 peoples of the Philippines and the Penan
Penan
The Penan are a nomadic aboriginal people living in Sarawak and Brunei. They are one of the last such peoples remaining. The Penan are noted for their practice of 'molong' which means never taking more than necessary...

 and Dayak people of Borneo. The Dayaks are a particularly interesting group as they are noted for their traditional headhunting culture. Fresh human heads were required to perform certain rituals such as the Iban “kenyalang” and the Kenyah “mamat”. Pygmies who live in Southeast Asia are, amongst others, referred to as “Negrito
Negrito
The Negrito are a class of several ethnic groups who inhabit isolated parts of Southeast Asia.Their current populations include 12 Andamanese peoples of the Andaman Islands, six Semang peoples of Malaysia, the Mani of Thailand, and the Aeta, Agta, Ati, and 30 other peoples of the Philippines....

”.

Cultivated Foods and Spices


Yam
Yam (vegetable)
Yam is the common name for some species in the genus Dioscorea . These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America and Oceania...

, Coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...

, chocolate
Chocolate
Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. Cacao has been cultivated for at least three millennia in Mexico, Central and South America. Its earliest documented use is around 1100 BC...

, banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

, mango
Mango
The mango is a fleshy stone fruit belonging to the genus Mangifera, consisting of numerous tropical fruiting trees in the flowering plant family Anacardiaceae. The mango is native to India from where it spread all over the world. It is also the most cultivated fruit of the tropical world. While...

, papaya
Papaya
The papaya , papaw, or pawpaw is the fruit of the plant Carica papaya, the sole species in the genus Carica of the plant family Caricaceae...

, macadamia
Macadamia
Macadamia is a genus of nine species of flowering plants in the family Proteaceae, with a disjunct distribution native to eastern Australia , New Caledonia and Sulawesi in Indonesia ....

, avocado
Avocado
The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel...

, and sugarcane
Sugarcane
Sugarcane refers to any of six to 37 species of tall perennial grasses of the genus Saccharum . Native to the warm temperate to tropical regions of South Asia, they have stout, jointed, fibrous stalks that are rich in sugar, and measure two to six metres tall...

 all originally came from tropical rainforest and are still mostly grown on plantations in regions that were formerly primary forest. In the mid-1980s and 90s, 40 million tons of bananas were consumed worldwide each year, along with 13 million tons of mango. Central American coffee exports were worth US$3 billion in 1970. Much of the genetic variation
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....

 used in evading the damage caused by new pests is still derived from resistant wild stock. Tropical forests have supplied 250 cultivated kinds of fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

, compared to only 20 for temperate forests. Forests in New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

 alone contain 251 tree species with edible fruits, of which only 43 had been established as cultivated crops by 1985.

Ecosystem Services



In addition to extractive human uses rain forests also have non-extractive uses that are frequently summarized as ecosystem services. Rain forests play an important role in maintaining biological diversity, sequestering & storing carbon, global climate regulation, disease control, and pollination.

Tourism


Despite the negative effects of tourism in the tropical rainforests, there are also several important positive effects.
  • In recent years Ecotourism
    Ecotourism
    Ecotourism is a form of tourism visiting fragile, pristine, and usually protected areas, intended as a low impact and often small scale alternative to standard commercial tourism...

     in the tropics has taken off. While Rainforests are becoming rarer and rarer people are flocking to nations that still have this diverse habitat. Locals are benefiting from the additional income brought in by visitors, as well areas deemed interesting for visitors are often conserved. Ecotourism can be an incentive for conservation, especially when it triggers positive economic change. Ecotourism can include a variety of activities including animal viewing, scenic jungle tours and even viewing cultural sights and native villages. If these practices are performed appropriately this can be beneficial for both locals and the present flora and fauna.

  • An increase in tourism has increased economic support, allowing more revenue to go into the protection of the habitat. Tourism can contribute directly to the conservation of sensitive areas and habitat. Revenue from park-entrance fees and similar sources can be utilised specifically to pay for the protection and management of environmentally sensitive areas. Revenue from taxation and tourism provides an additional incentive for governments to contribute revenue to the protection of the forest.
  • Tourism also has the potential to increase public appreciation of the environment and to spread awareness of environmental problems when it brings people into closer contact with the environment. Such increased awareness can induce more environmentally conscious behavior. Tourism has had a positive effect on wildlife preservation and protection efforts, notably in Africa but also in South America, Asia, Australia, and the South Pacific.

Mining & Drilling


Deposits of precious metals (gold, diamonds, coltan) and fossil fuels (oil and natural gas) occur underneath rainforests globally. These resources are important to developing nations and their extraction is often given priority to encourage economic growth. Mining and Drilling can require large amounts of land development, directly causing deforestation. In Ghana, a West African nation, deforestation from decades of mining activity left about 12% of the country's original rainforest intact.

Conversion to Agricultural Land


With the invention of agriculture
History of agriculture
Agriculture was developed at least 10,000 years ago, and it has undergone significant developments since the time of the earliest cultivation. The Fertile Crescent of Western Asia, Egypt, and India were sites of the earliest planned sowing and harvesting of plants that had previously been gathered...

, humans were able to clear sections of rainforest to produce crops, converting it to open farmland. Such people, however, obtain their food primarily from farm plots cleared from the forest and hunt and forage within the forest to supplement this.The issue arising is between the independent farmer providing for his family and the needs and wants of the globe as a whole. This issue has seen little improvement because no plan has been established for all parties to be aided.

Agriculture on formerly forested land is not without difficulties. Rainforest soils are often thin and leached of many minerals, and the heavy rainfall can quickly leach nutrients from area cleared for cultivation. People such as the Yanomamo of the Amazon
Amazon Rainforest
The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...

, utilize slash-and-burn agriculture to overcome these limitations and enable them to push deep into what were previously rainforest environments. However, these are not rainforest dwellers, rather they are dwellers in cleared farmland that make forays into the rainforest. Up to 90% of the typical Yanamomo diet comes from farmed plants.

Some action has been taken by suggesting fallow periods of the land allowing secondary forest to grow and replenish the soil. . Beneficial practices like soil restoration and conservation can benefit the small farmer and allow better production on smaller parcles of land.

Climate Change



The tropics have a large part in reducing atmospheric carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

. The tropics (most notably the Amazon rainforest
Amazon Rainforest
The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...

) are called carbon sinks. As the main carbon reducer is destroyed atmospheric temperature rises. Climate change has a seen a drastic shift with the destruction of the rainforest. A simulation was performed in which all rainforest in Africa were removed. The simulation showed an increase in atmospheric temperature by 2.5 to 5 Kelvin.

Protection


Efforts to protect and conserve tropical rainforest habitats are diverse and widespread. Tropical rainforest conservation
Tropical rainforest conservation
-Conservation:Right now, people are conserving the Tropical Rain Forests by ecotourism and rehabilitation. Ecotourism is giving people tours of the forest and showing them what we are losing by cutting them down...

 ranges from strict preservation of habitat to finding sustainable management techniques for people living in tropical rainforests. International policy has also introduced a market incentive program called Reducing Emissions from Deforestation and Forest Degradation (REDD) for companies and governments to outset their carbon emissions through financial investments into rainforest conservation.

Academic Resources

  • Agricultural and Forest Meteorology
  • Annals of Botany
  • Austral Ecology
    Austral Ecology
    Austral Ecology: A Journal of Ecology in the Southern Hemisphere is a peer-reviewed journal that publishes original research related to the ecology of land, marine and freshwater systems in the Southern Hemisphere...

  • Biodiversity and Conservation, ISSN: 0960-3115 eISSN: 1572-9710
  • Biological Conservation
  • Diversity and Distributions
  • Ecological Indicators
  • Ecological Management & Restoration
  • Ecoscience
  • Journal of Tropical Ecology
  • Palaeogeography, Palaeoclimatology, Palaeoecology
  • Studies on Neotropical Fauna and Environment

Further Reading

  • List of tropical and subtropical moist broadleaf forests ecoregions
  • Palaeogeography
    Palaeogeography
    Palaeogeography is the study of what the geography was in times past. It is most often used about the physical landscape, although nothing excludes its use in reference to the human or cultural environment...

  • Rainforest
    Rainforest
    Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...

  • Temperate rain forest
    Temperate rain forest
    Temperate rainforests are coniferous or broadleaf forests that occur in the temperate zone and receive high rainfall.-Definition:For temperate rain forests of North America, Alaback's definition is widely recognized:-Global distribution:...

  • Tropical and subtropical moist broadleaf forests
    Tropical and subtropical moist broadleaf forests
    Tropical and subtropical moist broadleaf forests , also known as tropical moist forests, are a tropical and subtropical forest biome....

  • Tropical rainforest climate
    Tropical rainforest climate
    A tropical rainforest climate, also known as an equatorial climate, is a tropical climate usually found along the equator...

  • Tropical Africa
    Tropical Africa
    Although tropical Africa is most familiar in the West as depicted by its rain forests, this region of Africa is far more diverse. While the tropics are thought of as regions with warm to hot moist climates caused by latitude and the tropical rain belt, the geology of areas, particularly mountain...


External links