Wet evergreen tropical forests. Rainforests

Wet equatorial forests(or tropical rainforests) are a geographical natural area that is located along the equator, moving towards the south.

Variety of flora and fauna.

Complex multi-tiered structure of the forest. There are four main tiers of tropical rainforest, which differ not only in flora, but also in fauna.

The presence of a humid climate with large amounts of precipitation and high air temperatures.

The flora is predominantly represented by evergreen tree-like plants with poorly developed bark, as well as flowers and fruits formed on tree trunks and branches.

The conditions in which tropical rainforests grow are determined by low blood pressure air, heavy tropical downpours and heat. Various tropical crops such as coconut palm, banana tree, cocoa and pineapples are also well cultivated under these conditions. These forests are called the "lungs" of the planet, but this statement is controversial according to scientists who claim that the vegetation tropical forests releases quite a bit of oxygen into the atmosphere.

Climate

Tropical rain forests are characterized by a humid and hot equatorial climate. There are minor temperature fluctuations throughout the year (from 24°C to 28°C), intense and uniform fall atmospheric precipitation(from 2000 to 10,000 mm per year) and high air humidity, caused by a high content of water vapor and reaching 80% and above. The seasons in this natural area alternate between the dry season and the tropical rain season.

In such a climate, vegetation rapidly develops in humid equatorial forests. The trees here are weakly branched, have a dense evergreen crown, and the height of the trunks reaches several tens of meters.

The upper tier is represented mainly by palm trees and ficus trees, and the lower tier by tree ferns, vines and large plants. At the foot of the trees there is always twilight created by lush crowns, which is why due to the lack sun rays Tropical rain forests have virtually no undergrowth.

The soil

Despite the growth of lush vegetation, the soil of tropical rainforests, due to the hot climate, is not very fertile and is very rich in aluminum and iron oxides. Great content of these chemical compounds gives it a red or red-yellow color, and the rapid decomposition of plants under the influence of bacteria prevents the accumulation of the humus (fertile) layer of the earth.

Geographical position

Equatorial rain forests are widespread in tropical regions with an equatorial climate, such as Central and South America (Amazon River basin), equatorial Africa, Southeast Asia (Malaysia, Indonesia, Philippines), northeastern Australia, and the Pacific Islands .

Our environment is sometimes taken for granted. Even something unique, like , is forgotten. It seems like a little knowledge and a push in in the right direction can make people appreciate environment. So why not start with the wonder that is the rainforest?

Despite the fact that tropical forests cover less than two percent of the Earth's total surface area, they are home to about 50% and. They are also found on all continents except Antarctica. This is very amazing! Now let's see what plants are found here. Of the 40,000 species, in this article you will learn about the 10 most amazing plants tropical forest that will excite your mind and help you get to know each other better amazing nature of our planet.

Bananas

Bananas are one of the amazing plants of the rainforest. Even though they look like trees, bananas are not trees but giant herbaceous plants. After a year, they reach a full height of 3 to 6 m. The flowers eventually develop into fruits and then mature and are used as food by humans and animals. Banana stems can weigh almost 45 kg and are almost 93% water.

Spreading: Central America, South America, Africa, Southeast Asia, as well as non-tropical regions such as the United States of America due to modern agricultural technology.

Orchid

Orchids are the largest family of plants in the world. Species vary greatly in weight and size, with some petals reaching 75 cm in length and inflorescences growing up to 3 m in length. They can also come in a variety of colors, with the exception of black. Orchids grow on rocks, in soil, underground and on other plants, relying on certain insects or birds for pollination.

Spreading: extremely well adapted and grow in Central America, South America and along the Andean mountains.

Coffee

What would you do if you didn't have a cup of coffee in the morning? Surely it would be terrible. You can thank the rainforest coffee plant for your coffee. It is capable of growing up to 9 m in height, but is considered a bush or shrub. Coffee fruits resemble grapes and contain two coffee beans inside. It takes six to eight years for the plant to grow, and its lifespan can reach 100 years.

Spreading: In Ethiopia, Sudan, and also Latin America More than two-thirds of the total number of coffee trees on the planet grows.

Brazilian nut

Rising taller than all other trees in the rainforest, the Brazil nut can reach over 50 m in height. The plant is widely known for its nutrient-rich fruits. The outer layer of the fruit is so hard that only agouti is a large rodent with sharp teeth, may damage it.

Spreading: tropical forests of Brazil, Colombia, Venezuela, Ecuador and Peru.

Beautiful spurge

This beautiful plant is found in tropical forests in the form of a bush or tree. You might think that the red part of the plant is the flowers, but they are actually bracts. The flowers are small yellow clusters in the middle of the leaves. Also, to clear up the rumors, they are not poisonous, although some believe they are.

Spreading: Mexico and Central America.

Cocoa

The cocoa tree is an evergreen plant whose fruits are pods containing 20 to 60 reddish-brown cocoa beans. To obtain 500 g of cocoa, 7 to 14 pods are required. It is very important that the cocoa is harvested correctly.

Spreading: grows below an altitude of 300 m above sea level in regions that receive about 10 cm of rainfall per month. Cocoa originated in the Amazon rainforest and can be found in southern Mexico today.

Hevea brasiliensis

This tree can grow up to 40 m in height. Hevea brasiliensis is characterized by its milky white sap, which is commonly called natural rubber, and is used to produce rubber. The tree is used to produce rubber at the age of six years.

Spreading: Brazil, Venezuela, Ecuador, Colombia, Peru and Bolivia.

Heliconia

This genus of plants includes almost 200 species distributed in tropical America. Depending on the species, these plants can grow up to 4.5 m in height. Flowers can be colored in shades of red, orange, yellow and green. The bracts actually hide the plant's flowers and protect the nectar so only certain birds, such as hummingbirds, can reach them. Butterflies also love to feast on sweet nectar.

Spreading: Central and South America.

Sapodilla

This strong, wind-resistant tree has an extensive root system and bark containing a milky sap called latex. The egg-shaped fruits contain a grainy yellow fruit inside and taste similar to a pear. Counts the best fruit in Central America, and even rainforest mammals love to snack on them. First chewing gum was created from the fruit of the sapodilla by the Aztecs!

Spreading: southern Mexico, Belize and northeastern Guatemala.

Bromeliads

Bromeliads include more than 2,700 species that grow on the ground, on rocks and on other plants. These beautiful plants have bright flowers. One of the most famous representatives of the bromeliad family is the sweet, wonderful fruit, the pineapple! Bromeliads even sometimes provide shelter for frogs, snails and salamanders, where they remain for life.

Spreading: Central and South America. One species is also found in West Africa.

The rainforest is home to many amazing plants, including those that many of us enjoy; Therefore, it is very important to preserve this unique. Imagine living without bananas, coffee, chocolate, pineapples and beautiful orchids. This is absolutely sad!

The equatorial rain forests are home to some of the richest flora in the world, as well as a huge storehouse of valuable wood, many useful and medicinal plants. Due to the difficult terrain, the vegetation of tropical forests has not yet been studied enough. Scientists have found that over 20 thousand flowering plants and about 3 thousand tree species. Forests South America have a richer flora than in Africa and South-East Asia.

General characteristics of the vegetation of equatorial forests

The tropical forest has a complex multi-tiered structure. The trees are distinguished by weakly branching, tall trunks with poorly developed bark, reaching up to 80 m in height and having elongated plank-shaped roots at the base. Most trees are densely entwined with vines.

Plants and shrubs of the middle tier have wide leaves, which help them absorb the light of the sun's rays under the dense crowns of more tall trees. The surface of the leaves is mostly leathery, shiny and dark green in color. The grass cover under the forest canopy is represented by subshrubs, mosses and lichens. Another one characteristic feature tropical vegetation- thin tree bark with fruits and flowers growing on it.

Let's take a closer look at some plants of humid equatorial forests:

The vegetation is represented by a huge variety of extra-tiered plants - epiphytes and lianas. More than 200 species of palms and ficus trees, about 70 species of bamboo plants, 400 species of ferns and 700 species of orchids grow here. The flora of the tropics differs different continents. In the tropics of South America, ficus and palm trees, bananas, hevea brasiliensis, and fragrant cedrela grow widely (cigarette cases are made from its wood). Ferns, vines and shrubs grow in the lower tiers. Of the epiphytes, orchids and bromeliads are widely found. In African tropical forests, the most common trees are the legume family, the coffee tree and the cocoa tree, as well as the oil palm.

Lianas. The most famous representatives of the tropical forest flora. They are distinguished by strong and large woody stems, reaching a length of over 70 m. Among them, the most interesting are the bamboo vine with shoots up to 20 m long, the medicinal vine strophanthus, as well as the poisonous physostigma, growing in West Africa. The legumes of this vine contain physostigmine, which is used for glaucoma.

Ficus stranglers. The seeds germinate, falling into the crevices of the trunks. The roots then form a dense frame around the host tree that keeps the ficus alive, inhibiting its growth and causing its death.

Hevea brasiliensis. Rubber, extracted from the milky sap of the tree, accounts for about 90% of its production in the world.

Ceiba. It reaches a height of up to 70 m. Oil for soap production is obtained from the seeds, and cotton fiber is extracted from the fruits, which is used to stuff upholstered furniture, toys and are used for heat and sound insulation.

Oil palm. “Palm oil” is extracted from its fruits, from which candles, margarine and soap are made, and sweet juice drinking in fresh or used for the production of wines and alcoholic beverages.

Rainforests located in the tropical, equatorial and subequatorial zones between 25° north latitude. and 30° S, as if “surrounding” the surface of the Earth along the equator. Rainforests are broken only by oceans and mountains.

The general circulation of the atmosphere occurs from a zone of high atmospheric pressure in the tropical region in the zone low pressure in the equator region, evaporated moisture is transferred in the same direction. This leads to the existence of a humid equatorial zone and a dry tropical one. Between them is subequatorial belt, in which moisture depends on the direction of the monsoon, which depends on the time of year.

The vegetation of tropical forests is very diverse, depending mainly on the amount of precipitation and its distribution over the seasons. When abundant (more than 2000 mm), and relatively uniform distribution develop tropical humid evergreen forests.

Further from the equator, the rainy period gives way to a dry period, and forests are replaced by leaves falling during drought, and then these forests are replaced by savanna forests. At the same time, in Africa and South America there is a pattern: from west to east, monsoon and equatorial forests are replaced by savanna forests.

Classification of tropical forests

Tropical rainforest, tropical rain forest these are forests with specific biomes located in equatorial (equatorial rain forest), subequatorial and humid tropical areas with a very humid climate (2000-7000 mm of precipitation per year).

Tropical rainforests are characterized by enormous biodiversity. This is the most conducive natural area for life. Lives here a large number of own, including endemic species of animals and plants, as well as migratory animals. Two-thirds of all animal and plant species on the planet live in tropical rainforests. It is estimated that millions of animal and plant species remain undescribed.

These forests are sometimes called " jewels of the earth" And " the largest pharmacy in the world", since a large amount of natural medical supplies. They are also called " lungs of the Earth“However, this statement is controversial because it has no scientific basis, since these forests either do not produce oxygen at all or produce extremely little of it.

But it should be borne in mind that a humid climate promotes effective air filtration due to the condensation of moisture on microparticles of pollution, which has a generally beneficial effect on the atmosphere.

Understory formation in tropical forests is severely limited in many places due to the lack of sunlight in the understory. This allows humans and animals to move through the forest. If for some reason the deciduous canopy is absent or weakened, the lower tier is quickly covered with a dense thicket of vines, shrubs and small trees - this formation is called a jungle.

The largest areas of tropical rainforest are found in the Amazon Basin (“ rain forests Amazon"), in Nicaragua, in the southern part of the Yucatan Peninsula (Guatemala, Belize), in most of Central America (where they are called "selvas"), in equatorial Africa from Cameroon to Democratic Republic Congo, in many areas of Southeast Asia from Myanmar to Indonesia and New Guinea, in the Australian state of Queensland.

For tropical rainforests characteristic:

variety of flora,
presence of 4-5 tree layers, absence of shrubs, large number of vines
predominance evergreen trees with large evergreen leaves, poorly developed bark, buds not protected by bud scales, in monsoon forests– deciduous trees;
the formation of flowers and then fruits directly on trunks and thick branches

Trees in tropical rainforests have several general characteristics, which are not observed in plants of less humid climates.

The base of the trunk in many species has wide, woody projections. Previously it was assumed that these protrusions help the tree maintain balance, but now it is believed that along these protrusions there is water with dissolved nutrients flows down to the roots of the tree. The broad leaves of trees, shrubs and grasses of the lower tiers of the forest are characteristic. Wide leaves help plants absorb better sunlight There are forests under the edges of the trees, and they are protected from the wind from above.

Tall young trees that have not yet reached the top tier also have wider foliage, which then decreases with height. The leaves of the upper tier, which form the canopy, are usually smaller and heavily cut to reduce wind pressure. On the lower floors, the leaves are often narrowed at the ends so that this facilitates the rapid drainage of water and prevents the growth of microbes and moss on them, which destroy the leaves.

Tree tops are often very well connected with each other using vine or epiphytic plants, attached to them.

The trees of the tropical rainforest are characterized by unusually thin (1-2 mm) tree bark, sometimes covered with sharp thorns or prickles, the presence of flowers and fruits growing directly on the tree trunks, and a wide variety of juicy fruits that attract birds and mammals.

In tropical rainforests there are a lot of insects, especially butterflies (one of the richest faunas in the world) and beetles, and in rivers there are a lot of fish (about 2000 species, approximately a third of the world's freshwater fauna).

Despite the lush vegetation, the soil in tropical rainforests is thin and has a small humus horizon.

Rapid rotting caused by bacteria prevents the accumulation of a humus layer. The concentration of iron and aluminum oxides due to laterization Soil dehydration (the process of reducing silica in the soil while increasing iron and aluminum oxides) turns the soil bright red and sometimes forms mineral deposits (such as bauxite). But on rocks of volcanic origin, tropical soils can be quite fertile.

Levels (tiers) of tropical rainforest

The rainforest is divided into four main levels, each of which has its own characteristics and has different flora and fauna.

Top level

This layer consists of a small number of very tall trees rising above the forest canopy, reaching a height of 45-55 meters ( rare species reach 60-70 meters). Most often the trees are evergreen, but some shed their leaves during the dry season. Such trees must withstand harsh temperatures and strong winds. Eagles live on this level, the bats, some species of monkeys and butterflies.

Crown level (forest canopy)

The crown level is formed by most tall trees, usually 30-45 meters high. This is the densest layer known in all of Earth's biodiversity, with neighboring trees forming a more or less continuous layer of foliage.

According to some estimates, plants of this tier make up approximately 40 percent of the species of all plants on the planet - perhaps half of the entire flora of the Earth can be found here. The fauna is similar to the upper level, but more diverse. It is believed that a quarter of all insect species live here.

Scientists have long suspected the diversity of life at this level, but only recently have they developed practical research methods. It was not until 1917 that the American naturalist William Beed declared that “another continent of life remains unknown, not on the earth, but 200 feet above its surface, extending over thousands of square miles.”

Real exploration of this layer only began in the 1980s, when scientists developed techniques to reach the forest canopy, such as shooting ropes into the treetops with crossbows. Forest canopy research is still in its early stages. Other research methods include travel on balloons or aircraft. The science of reaching treetops is called dendronautics.

Average level

Between the forest canopy and the forest floor there is another level called the understory. It is home to a number of birds, snakes and lizards. Insect life at this level is also very extensive. The leaves in this tier are much wider than at the crown level.

forest floor

IN Central Africa in the tropical primary forest of Mount Virunga, illumination at ground level is 0.5%; in the forests of southern Nigeria and in the Santarem region (Brazil) 0.5-1%. In the north of the island of Sumatra in the dipterocarp forest, the illumination is about 0.1%.

Far from the banks of rivers, swamps and open spaces where dense, low-growing vegetation grows, forest floor relatively free of plants. At this level you can see rotting plants and animal remains, which quickly disappear thanks to the warm, humid climate, promoting rapid decomposition.

Selva(Spanish: " selva" from lat. " silva"- forest) is equatorial rainforests in South America. Located in countries such as Brazil, Peru, Suriname, Venezuela, Guyana, Paraguay, Colombia, etc.

The selva is formed on vast low-lying areas of land under conditions of constant freshwater moisture, as a result of which the selva soil is extremely poor in minerals washed away by tropical rains. Selva is often swampy.

Vegetable and animal world The jungle is a riot of colors and a variety of species of plants, birds and mammals.

The largest village in terms of area is located in the Amazon basin in Brazil).

In the Atlantic jungle, precipitation reaches two thousand millimeters per year, and humidity fluctuates at 75-90 percent.

The village is divided into three levels. The soil is covered with leaves, branches, trunks of fallen trees, lichens, fungus and moss. The soil itself is reddish in color. The first level of the forest consists of low plants, ferns and grass. The second level is represented by shrubs, reeds and young trees. On the third level there are trees from twelve to forty meters high.

Mangroves – evergreen deciduous forests, common in the tidal zone sea coasts in tropical and equatorial latitudes, as well as in areas with temperate climate, where it is favorable warm currents. They occupy the band between the lowest water level at low tide and the highest at high tide. These are trees or shrubs that grow in mangroves, or mangrove swamps.

Mangrove plants live in sedimentary coastal environments where fine sediments, often high in organic matter, accumulate in areas protected from wave energy.

Mangroves have an exceptional ability to exist and develop in a saline environment on soils deprived of oxygen.

Once established, mangrove plant roots create habitat for oysters and help slow water flow, thereby increasing sedimentation in areas where it is already occurring.

As a rule, fine, oxygen-poor sediments under mangroves act as reservoirs for a wide variety of heavy metals (trace metals), which are captured from sea water colloidal particles in sediments. In those areas of the world where mangroves were destroyed during the development of the territory, the violation of the integrity of these sedimentary rocks gives rise to the problem of heavy metal contamination of sea water and local flora and fauna.

It is often argued that mangroves provide significant coastal value, acting as a buffer against erosion, storms and tsunamis. Although there is a definite reduction in wave height and wave energy as seawater passes through mangroves, it must be recognized that mangroves typically grow in those areas coastline, where low wave energy is the norm. Therefore, their ability to withstand the powerful onslaught of storms and tsunamis is limited. Their long-term impact on erosion rates is also likely to be limited.

Many river channels meandering through mangrove areas actively erode the mangroves on the outside of all river bends, just as new mangroves appear on the inside of the same bends where sedimentation occurs.

Mangroves provide habitat for wild animals, including a number of commercial species fish and crustaceans, and in at least some cases the export of stored carbon by mangroves is important in the coastal food web.

In Vietnam, Thailand, the Philippines and India, mangroves are grown in coastal areas for inshore fisheries.

Despite ongoing mangrove breeding programs, More than half of the world's mangroves have already been lost..

The floristic composition of mangrove forests is relatively uniform. Mangrove forests of the eastern formation (the shores of the Malacca Peninsula, etc.) are considered the most complex, tall and multi-species.

Misty forest (moss forest, nephelogia) – tropical moist montane evergreen forest. Located in the tropics on the slopes of mountains in a zone of fog condensation.

The foggy forest is located in the tropics on the slopes of mountains in a zone of fog condensation, usually starting at altitudes of 500-600 m and reaching heights of up to 3500 meters above sea level. It is much cooler here than in the jungles located in low-lying areas; at night the temperature can drop to almost 0 degrees. But it’s even more humid here, one year a year square meter Up to six cubic meters of water falls. And if it doesn’t rain, then the moss-covered trees stand shrouded in fog caused by intense evaporation.

Foggy forest formed by trees with abundant lianas, with a dense cover of epiphytic mosses.

Tree ferns, magnolias, camellias are characteristic; the forest may also include non-tropical vegetation: evergreen oaks, podocarpus, which distinguishes this type of forest from lowland gils

Variable tropical rainforests– forests common in tropical and equatorial zones, in climates with a short dry season. They are located south and north of the equatorial rainforests. Variably humid forests are found in Africa (CAR, DR Congo, Cameroon, northern Angola, extreme south of Sudan), South America, India, Sri Lanka, and Indochina.

Variable rainforests are partly deciduous, dense tropical forests. They differ from humid tropical forests in lower species diversity and in the reduced number of epiphytes and lianas.

Dry tropical evergreen forest. Located in areas with arid climate, while remaining dense and evergreen, they become stunted and xeromorphic.

HUMAN IMPACT ON TROPICAL FORESTS

Contrary to popular belief, tropical rainforests are not major consumers carbon dioxide and, like other established forests, are carbon neutral.

Recent studies show that most rain forests are, on the contrary, intensively produce carbon dioxide, and swamps produce methane.

However, these forests play a significant role in the circulation of carbon dioxide because they are established reservoirs, and cutting down such forests leads to an increase in carbon dioxide in the Earth's atmosphere. Tropical rainforests also play a role in cooling the air that passes through them. That's why tropical rainforests - one of the most important ecosystems on the planet, the destruction of forests leads to soil erosion, a reduction in species of flora and fauna, and shifts in the ecological balance large areas and on the planet as a whole.

Tropical rainforests They are often used for plantations of cinchona and coffee trees, coconut palms, and rubber trees. In South America, tropical rainforests are also seriously threatened by unsustainable mining.

A.A. Kazdym

List of used literature

M. B. Gornung. Constantly humid tropics. M.: “Thought”, 1984.
Hogarth, P. J. The Biology of Mangroves. Oxford University Press, 1999.
Thanikaimoni, G., Mangrove Palynology, 1986
Tomlinson, P. B. The Botany of Mangroves, Cambridge University Press. 1986:
Jayatissa, L. P., Dahdouh-Guebas, F. & Koedam, N. A review of the floral composition and distribution of mangroves in Sri Lanka. Botanical Journal of the Linnean Society, 138, 2002, 29-43.
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IN equatorial belt, encircling the entire Earth On both sides of the equator, evergreen, permanently moist tropical forests dominate for thousands of kilometers. These forests are better known to us under the capacious and sonorous name - jungle. From the Hindi language, the word “jungle” is translated as “dense thickets” or simply “forest”.

Jungles occupy vast areas Equatorial Africa, Central and South America, the southwestern coast of India, the Indochina peninsula, the islands of Indonesia, the Greater Sunda and Philippine Islands, part of the island of New Guinea.

The equatorial belt receives more solar energy and heat than other belts of the Earth. Annual precipitation here ranges from 1,500 to 12,000 mm. It rains in the afternoon, and most often it is heavy showers - a continuous wall of water. The air is saturated with water vapor, and therefore relative humidity its very high - 80-90%, which at constant high temperatures(annual average +24...+28 °C with fluctuations between the warmest and coldest months of 2-3 °C) creates excess moisture. The air is humid and warm, so it is difficult to breathe, as in the steam room of a bathhouse. There is no cooling evaporation, not even a light breeze, and the heat of the day does not subside even at night.

Dense vegetation interferes with normal air circulation, and this contributes to the formation of hot and thick ground fogs, like cotton wool. There is constant damp twilight here, as the dense crowns of trees prevent sunlight from penetrating the soil and drying it out.

As a result of strong putrefactive processes in fallen leaves, the percentage of carbon dioxide in the ground layers increases sharply. Therefore, in the tropical forest there is not enough oxygen, and a person who ends up there constantly complains of suffocation.

Ancient evergreen forests are lush, dense, diverse and rich species composition. The evergreen vegetation of a permanently humid tropical forest consists of several tiers. The first tier consists of giant trees 30-50 m high with smooth, knot-free trunks and a wide crown. In the second tier, the trees have a height of 20-30 m, and the third consists of various palm trees with a height of 10 to 20 m. The fourth tier is an undergrowth of bamboo, bushes, ferns and mosses. All this is wrapped around an incredible number of intertwined vines, forming a continuous green, almost impenetrable network.

Tropical rainforests are divided into primary and secondary. The primary tropical forest is quite traversable, even despite the wide variety of woody vegetation and vines. But secondary forests, located along river banks and in places of frequent fires, form impenetrable thickets of a chaotic pile of bamboo, grasses, various shrubs and trees, intertwined with numerous vines. In the secondary forest, multi-layering is practically not expressed. Here, at a great distance from each other, huge trees grow that tower above the lower general level vegetation. Such forests are widespread throughout the humid tropics.

The fauna of the constantly humid evergreen tropical forests is very diverse. From large mammals there are a lot of elephants, hippos and crocodiles here. There are a lot of birds and various insects. But still in each specific tropical zone On different continents, both flora and fauna sometimes differ significantly from each other. Therefore, it is advisable to consider these territories each separately, taking into account their potential danger for a person in an extreme situation.