The world of tropical forest flora is extremely diverse. Plants of tropical forests: list, types, names, descriptions and photos. Main Characteristics of the Rainforest

About half of all forests on our planet are tropical forests (hylaea), growing in Africa, Southeast Asia, South and Central America. Tropical rainforests are located between 25° north latitude and 30° south latitude, where heavy rainfall occurs frequently. The rainforest ecosystem covers less than two percent of the Earth's surface, but is home to 50 to 70 percent of all life on our planet.

The largest tropical forests are found in Brazil (South America), Zaire (Africa) and Indonesia (Southeast Asia). Rainforest is also found in Hawaii, the Pacific Islands and the Caribbean.

Rainforest climate

The climate in the tropical forest is very warm and humid. Every year, between 400 and 1000 cm of precipitation falls here. The tropics are characterized by a uniform annual distribution of precipitation. There is practically no change in seasons, and average temperature air is 28 degrees Celsius. All these conditions significantly influenced the formation of the richest ecosystem on our planet.

Soil in the rainforest

The soil of the tropics is poor in minerals and nutrients - there is a lack of potassium, nitrogen and other trace elements. It is usually red and red-yellow in color. Because of frequent precipitation, useful material are absorbed by plant roots or go deep into the soil. That's why the aborigines tropical forests A slash-and-burn agricultural system was used: all vegetation was cut down in small areas, it was subsequently burned, and then the soil was cultivated. Ash acts as a nutrient. When the soil begins to turn infertile, usually after 3-5 years, the inhabitants of tropical settlements moved to new areas for farming. Agriculture. It is a sustainable farming method that ensures continued regeneration of the forest.

Rainforest Plants

The warm, humid climate of the rainforest provides the ideal environment for a huge abundance of amazing plant life. A tropical forest are divided into several tiers, each characterized by its own flora and fauna. The tallest trees in the tropics get greatest number sunlight, as they reach a height of more than 50 meters. This includes, for example, the cotton tree.

The second tier is the dome. It is home to half of the rainforest's wildlife - birds, snakes and monkeys. This includes trees below 50 m in height with wide leaves, hiding sunlight from the lower floors. These are philodendron, strychnos poisonous and rattan palms. Lianas usually stretch along them towards the sun.

The third tier is inhabited by shrubs, ferns and other shade-tolerant species.

The last tier, the bottom, is usually dark and damp, since almost no sunlight penetrates here. It consists of rotted foliage, mushrooms and lichens, as well as young growth of plants of higher tiers.

In each of the regions where tropical forests grow, there are different types trees.

Tropical trees of Central and South America:

• Mahogany (Sweitinia spp.)
• Spanish cedar (Cedrella spp.)
• Rosewood and Cocobolo (Dalbergia retusa)
• Purple tree (Peltogyne purpurea)
• Kingwood
• Cedro Espina (Pochote spinosa)
• Tulipwood
• Gaiakan (Tabebuia chrysantha)
• Tabebuia rosea
• Bocote
• Jatoba (Hymenaea courbaril)
• Guapinol (Prioria copaifera)

Tropical trees of Africa:

• Bubinga
• Ebony
• Zebrano
• Pink tree

Tropical trees of Asia:

• Malaysian maple

They are widespread in the tropical rain forest and feed on captured insects and small animals. Among them, Nepenthes (Pitcher Plants), sundew, butterwort, and bladderwort should be noted. By the way, the plants of the lower level with their bright flowering attract insects for pollination, since in these layers there is practically no wind.

Valuable crops are grown in places where tropical forests are cleared:

• mango;
• bananas;
• papaya;
• coffee;
• cocoa;
• vanilla;
• sesame;
• sugar cane;
• avocado;
• cardamom;
• cinnamon;
• turmeric;
• nutmeg.

These cultures play an important role in cooking and cosmetology. Some tropical plants serve as raw materials for medicines, in particular anti-cancer drugs.

Tropical Plant Adaptations for Survival

Any flora needs moisture. There is never a shortage of water in the rainforest, but there is often too much of it. Rainforest plants must survive in areas where there is constant rainfall and flooding. The leaves of tropical plants help deflect raindrops, and some species are armed with a drip tip designed to quickly drain precipitation.

Plants in the tropics need light to live. The dense vegetation of the upper layers of the forest allows little sunlight to reach the lower layers. Therefore, tropical forest plants must either adapt to life in constant twilight, or quickly grow upward in order to “see” the sun.

It is worth noting that in the tropics trees grow with thin and smooth bark, which is capable of accumulating moisture. Some plant species have leaves wider at the bottom of the crown than at the top. This helps allow more sunlight to reach the soil.

As for the epiphytes themselves, or air plants that grow in the rainforest, they obtain nutrients from plant debris and bird droppings that land on the roots and do not depend on the poor soil of the forest. In tropical forests there are such aerial plants as orchids, bromeliads, ferns, selenicereus grandiflora and others.

As mentioned, the soil in most tropical forests is very poor and lacks nutrients. To capture nutrients at the top of the soil, most rainforest trees have shallow roots. Others are wide and powerful, as they must support a massive tree.

Rainforest Animals

The animals of the tropical forests amaze the eye with their diversity. It is in this natural area that you can meet the largest number of representatives of the fauna of our planet. Most of them are in the Amazon rainforest. For example, there are 1,800 species of butterflies alone.

In general, the tropical forest is the habitat of most amphibians (lizards, snakes, crocodiles, salamanders), predators (jaguars, tigers, leopards, pumas). All animals of the tropics have bright colors, since spots and stripes are the best camouflage in the dense jungle. The sounds of the rainforest are provided by the polyphony of songbirds. The tropical forests have the world's largest population of parrots, and other interesting birds include the South American harpy, one of the fifty eagle species that is critically endangered. No less colorful birds are peacocks, whose beauty has long been the subject of legends.

Also lives in the tropics more quantity monkeys: arachnids, orangutans, chimpanzees, monkeys, baboons, gibbons, red-bearded jumpers, gorillas. In addition, there are sloths, lemurs, Malayan and sun bears, rhinoceroses, hippos, tarantulas, ants, piranhas and other animals.

Disappearance of tropical forests

Tropical timber has long been synonymous with exploitation and plunder. The giant trees are the target of entrepreneurs who use them for commercial purposes. How are forests exploited? The most obvious use of rainforest trees is in the furniture industry.

According to European Commission, about one fifth of EU timber imports are from illegal sources. Every day, thousands of products from the international wood mafia pass through store shelves. Tropical wood products are often labeled as "luxury wood", "hardwood", "natural wood" and "solid wood". Usually these terms are used to disguise tropical wood from Asia, Africa and Latin America.

The main exporting countries of tropical trees are Cameroon, Brazil, Indonesia and Cambodia. The most popular and expensive breeds The tropical woods that are sold are mahogany, teak and rosewood.

Inexpensive species of tropical wood include meranti, ramin, and gabun.

Consequences of tropical deforestation

In most tropical forest countries, illegal logging is common and a serious problem. Economic losses reach billions of dollars, and environmental and social damage is incalculable.

The consequences of tropical deforestation are deforestation and profound environmental changes. Tropical forests contain the world's largest . As a result of poaching, millions of species of animals and plants lose their habitat and, as a result, disappear.

According to the International Union for Conservation of Nature (IUCN) Red List, more than 41,000 plant and animal species are threatened, including great apes such as gorillas and orangutans. Scientific estimates of species lost vary widely, ranging from 50 to 500 species per day.

In addition, logging equipment used to remove timber destroys sensitive topsoil and damages the roots and bark of other trees.

Mining for iron ore, bauxite, gold, oil and other minerals also destroys large areas of tropical forests, such as in the Amazon.

The Meaning of Rainforests

Tropical rainforests play an important role in the ecosystem of our planet. Deforestation of this particular natural area leads to the formation greenhouse effect and, subsequently, to global warming. The largest tropical forest in the world, the Amazon, plays the most important role in this process. 20 percent of global greenhouse gas emissions are attributed to deforestation. The Amazon rainforest alone stores 120 billion tons of carbon.

Tropical forests also contain enormous amounts of water. Therefore, another consequence of deforestation is a disrupted water cycle. This in turn could lead to regional droughts and changes in global weather patterns - with potentially devastating consequences.

The rainforest is home to unique flora and fauna.

How to protect tropical forests?

To prevent the negative consequences of deforestation, it is necessary to expand forest areas, strengthen control over forests at the state and international levels. It is also important to raise people's awareness of the role forests play on this planet. Environmentalists say it is also worth encouraging reduction, recycling and reuse forest products. Switching to alternative energy sources, such as fossil gas, could in turn reduce the need to exploit forests for heating.

Deforestation, including tropical forests, can be carried out without harming this ecosystem. In Central and South America and Africa, trees are cut down selectively. Only trees that have reached a certain age and trunk thickness are cut down, while young trees remain untouched. This method causes minimal damage to the forest, because it allows it to quickly recover.

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 to a zone of low pressure in the equator region, and evaporated moisture is transported 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 are developing 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 rainforest), 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. It is home to a large number of native, 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” as a large number of natural medicines have been found here. 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), mostly Central America(where they are called "selva"), in equatorial Africa from Cameroon to the Democratic Republic of the 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 water with dissolved nutrients flows along these protrusions 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 better absorb sunlight under the edges of the trees of the forest, 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, fixed on 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. This level is home to eagles, 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%.

Away from river banks, swamps and open spaces where dense, low-growing vegetation grows, the forest floor is relatively free of plants. At this level, rotting plants and animal remains can be seen, which quickly disappear due to the warm, humid climate that promotes 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.

The flora and fauna of the selva 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 ranging in height from twelve to forty meters.

Mangroves – evergreen deciduous forests, common in the tidal zone of sea coasts in tropical and equatorial latitudes, as well as in areas with temperate climate, where warm currents favor this. They occupy the space between the most low level water during low tide and highest during high tide. These are trees or shrubs growing 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.

Typically, the fine, oxygen-poor sediments beneath mangroves act as reservoirs for a wide variety of heavy metals (trace metals), which are captured from seawater by colloidal particles in the sediment. In those areas of the world where mangroves were destroyed during the development of the territory, the integrity of these sedimentary rocks gives rise to the problem of heavy metal pollution 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 areas of the 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 wildlife, including a range of commercial fish and crustacean species, and in at least some cases the export of carbon stored 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..

Floral composition mangrove forests relatively monotonous. 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 here it is even more humid; up to six cubic meters of water fall per square meter per year. 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. Located south and north of the wetlands equatorial forests. 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 an 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 large consumers of 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 over 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

1. M. B. Gornung. Constantly humid tropics. M.: “Thought”, 1984.
2. Hogarth, P. J. The Biology of Mangroves. Oxford University Press, 1999.
3. Thanikaimoni, G., Mangrove Palynology, 1986
4. Tomlinson, P. B. The Botany of Mangroves, Cambridge University Press. 1986:
5. 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.
6. http://www.glossary.ru/cgi-bin/gl_sch2.cgi?RSwuvo,lxqol!rlxg

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Have you adapted to his bath conditions?

How have the leaves adapted?

Throughout life, the leaves of some tropical plants change shape. Young trees, while they are still covered by the crowns of the trees of the upper tier, have wide, soft leaves. They are adapted to catch the slightest rays of light breaking through the upper canopy. They have a yellowish or reddish tint. This is how they try to escape from being devoured by animals. Red or yellow colors may seem inedible to them.

When the tree grows to the first tier, its leaves decrease in size and seem to become covered with wax. Now there is a lot of light and the leaves have a different task. Water should drain completely from them without attracting small animals.

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The leaves of some plants can regulate the flow of sunlight. To avoid overheating in bright light, they stand parallel to the sun's rays. When the sun is shaded by a cloud, the leaves turn horizontally to capture more solar energy for photosynthesis.

Pollination of flowers

For pollination, flowers must attract insects, birds or bats. They attract with their bright color, smell and delicious nectar. To attract their pollinators, even the plants of the upper tier decorate themselves with beautiful flowers. Moreover, during flowering they even shed some of their leaves so that their flowers stand out more noticeably.

To attract insects, orchids secrete nectar, which makes bees drunk. They are forced to crawl on the flower, pollinating it. Other types of orchids simply slam shut, showering the insect with pollen.

But it’s not enough to pollinate the flowers; you also need to spread the seeds. Seeds are dispersed by animals. To attract them, plants offer them tasty fruits with seeds hidden inside. The animal eats the fruit, and the seed comes out along with excrement, fully capable of germination.

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Sometimes plants reproduce with the help of only one type of animal. So the American walnut reproduces only with the help large rodent agouti. Although agoutis eat all the nuts, they bury some of them in the ground. Our proteins also make such a reserve. Forgotten seeds sprout.

Eating animals in the tropics

Among the abundance of food, there is not enough food for animals. Plants have learned to protect themselves with thorns, poisons, and bitter substances. Over the years of evolution, animals have found their own way of adapting to living in tropical forests. They live in a certain place and lead a life that ensures its survival.

It happens that a predator eats beetles a certain type. He learned to catch beetles quickly, spending a minimum of time and effort on hunting. The predator and his prey got used to each other. If the beetle disappears, the predator that eats them will also die out.

Adaptation of animals to living in the subtropics

In the tropics, food grows and flutters all year round, but it is not enough. All conditions have been created for invertebrates in the forest, and they grow to large sizes. These are centipedes, snails and stick insects. Mammals are small. There are few herbivores in the forest. There isn't enough food for them there. This means there are few predators feeding on them. There are no animals here that have long horns. They are difficult to navigate in the tropics. Mammals move quietly. Thus, they are saved from overheating.

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Agile monkeys live well in the tropics. They quickly move through the forest, looking for places where a lot of fruit has grown. The monkey's tail replaces its fifth limb. The anteater and the quilled porcupine also have a grasping tail. Animals that could not climb well learned to fly well. They plan easily. They have a leathery membrane that connects the front and back legs.

Union of a tree with ants

In the tropics there are trees that have hollow branches. Ants live in the cavities of branches. They protect their tree from herbivores. Ants provide the tree with enough light. They eat the leaves of vines in nearby trees that block the light for their host tree. Ants eat all leaves that do not resemble the leaves of their native tree. They even remove all organic matter from its crown. The tree stands well-groomed, as if from a gardener. For this, insects have dry housing and safety.

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How did frogs adapt?

High humidity air allows toads and frogs to live away from the river. They live well, living in the upper tiers of the forest. The frogs chose tree hollows for the pond. They coat it with resin from the inside and wait for it to fill with rainwater. The frog then lays eggs there. Dart frogs make holes in moist soil for their offspring.

The male remains to guard the clutch. Then it transfers the tadpoles to the resulting pond formed between the leaves of the bromeliad. Some frogs lay their eggs in a foam nest. They make a nest on branches hanging over the river. The hatched tadpoles immediately fall into the river. Other frogs lay their eggs in damp soil. They come out of there as young individuals.

Animal disguise

Animals in the forest try to become invisible to their predators. Under the forest canopy there is a constant play of light and shadow. Okapis, antelopes, and bongos have such spotted skins. The spotting blurs the contours of their body and makes them difficult to distinguish. It can be very successfully disguised as leaves. If the animal looks like a leaf and does not move, it is difficult to see. That's why many insects and frogs are green or Brown. Plus they don't move much. And stick insects disguise themselves as twigs.

Structure and structure. It is almost impossible to give a general description of the structure of a tropical rainforest: this extremely complex plant community reveals such a variety of types that even the most detailed descriptions. Just a few decades ago, it was believed that a wet forest was always impenetrable thickets of trees, shrubs, ground grasses, lianas and epiphytes, since it was mainly judged by descriptions of mountain rain forests. Only relatively recently has it become known that in some tropical rainforests, due to the dense canopy of tall trees, almost no sunlight reaches the soil, so the undergrowth here is sparse, and one can walk through such forests almost unhindered.

It is customary to especially emphasize the species diversity of tropical rainforests. It is often noted that you can hardly find two specimens of trees of the same species. This is a clear exaggeration, but at the same time, it is not uncommon to find 50-100 species of trees on an area of ​​1 hectare.

But there are also relatively species-poor, “monotonous” moist forests. These include, for example, special forests consisting mainly of trees of the Dipterocarpaceae family, growing in very sediment-rich areas of Indonesia. Their existence indicates that in these areas the stage of optimal development of tropical rainforests has already passed. The extreme abundance of precipitation makes it difficult to aerate the soil, as a result of which plants have been selected that have adapted to living in such places. Similar living conditions can also be found in some damp areas of South America and the Congo Basin.

The dominant component of tropical rainforest is trees of varying appearance and height; they make up about 70% of all species found here higher plants. There are three tiers of trees - upper, middle and lower, which, however, are rarely clearly expressed. The upper tier is represented by individual giant trees; their height, as a rule, reaches 50-60 m, and the crowns develop above the crowns of trees below the tiers. The crowns of such trees do not close; in many cases, these trees are scattered in the form of individual specimens that seem to be overgrown. On the contrary, the crowns of trees of the middle tier, having a height of 20-30 m, usually form a closed canopy. Due to the mutual influence of neighboring trees, their crowns are not as wide as those of the trees of the upper tier. The degree of development of the lower tree layer depends on the illumination. It is made up of trees reaching an average height of approximately 10 meters. A special section of the book will be devoted to lianas and epiphytes found in different layers of the forest (pp. 100-101).

There is often also a layer of shrubs and one or two layers of herbaceous plants; they are composed of representatives of species that can develop in minimal light. Since the ambient air humidity is constantly high, the stomata of these plants remain open throughout the day and the plants are not in danger of wilting. Thus, they are constantly assimilating.

Based on the intensity and nature of growth, tropical rainforest trees can be divided into three groups. The first consists of species whose representatives grow quickly but do not live long; they are the first to develop where in the forest either naturally, or as a result of human activity, lightened areas are formed. These light-loving plants stop growing after about 20 years and give way to other species. Such plants include, for example, the South American balsa tree ( Ochroma lagopus) and numerous myrmecophilous cecropia species ( Cecropia), African species Musanga cecropioides and representatives of the Euphorbiaceae family, growing in tropical Asia, belonging to the genus Macaranga.

The second group covers species whose representatives are early stages development also grows quickly, but their growth in height continues longer, and after its completion they are able to live for a very long time, probably for more than one century. This is the most characteristic trees the upper tier, the crowns of which are usually not shaded. These include many economically important trees, the wood of which is commonly called "mahogany", for example species belonging to the genus Swietenia(tropical America), Khaya And Entandrophragma(tropical Africa).

Finally, the third group includes representatives of shade-tolerant species that grow slowly and live long. Their wood is usually very heavy and hard, it is difficult to process it, and therefore it is not as widely used as the wood of trees of the second group. However, the third group includes species that produce noble wood, in particular Tieghemella heckelii or Aucoumea klainiana, the wood of which is used as a substitute for mahogany.

Most trees are characterized by straight, columnar trunks, which often rise to a height of more than 30 meters without branching. Only there at the detached giant trees a spreading crown develops, while in the lower tiers, as already mentioned, the trees, due to their close arrangement, form only narrow crowns.

In some types of trees, plank-shaped roots form near the base of the trunks (see figure), sometimes reaching a height of up to 8 m. They give the trees greater stability, since root systems that develop shallowly do not provide a sufficiently strong anchorage for these huge plants. The formation of plank-shaped roots is genetically determined. In representatives of some families, for example, Moraceae (mulberry), Mimosaceae (mimosa), Sterculiaceae, Bombacaceae, Meliaceae, Bignoniaceae, Combretaceae, they are found quite often, while in others, for example Sapindaceae, Apocynaceae, Sapotaceae, they are not present at all.

Trees with plank roots most often grow in damp soils. It is possible that the development of plank-shaped roots is associated with the poor aeration characteristic of such soils, which prevents the secondary growth of wood on internal sides lateral roots (it is formed only on their outer sides). In any case, trees growing on moisture-permeable and well-aerated soils of mountain rainforests do not have plank-shaped roots.

Trees of other species are characterized by stilted roots; they are formed above the base of the trunk as adventitious ones and are especially common in trees of the lower tier, which also grow mainly in damp habitats.

Differences in the microclimate characteristic of different tiers of tropical rainforest are also reflected in the structure of the leaves. While the trees of the upper storeys usually have elliptical or lanceolate in outline, smooth and dense leathery leaves like laurel leaves (see figure on page 112), capable of withstanding alternating dry and wet periods during the day, the leaves of the trees of the lower storey exhibit signs indicating intense transpiration and rapid removal of moisture from their surface. They are usually larger; their plates have special points on which water collects and then falls from them in drops, so there is no water film on the surface of the leaf that would interfere with transpiration.

The change of foliage in trees of tropical rainforests is not influenced by external factors, in particular drought or cold, although even here it is possible to replace the known periodicity, which varies among different species. In addition, some independence of individual shoots or branches is manifested, so not the entire tree is leafless at once, but only part of it.

The climatic features of the tropical rainforest also affect the development of foliage. Since there is no need to protect the growing points from cold or drought, as in areas with a temperate climate, the buds are relatively weakly expressed and are not surrounded by bud scales. As new shoots develop, many tropical rainforest trees experience a “drooping” of leaves, which is caused by an extremely rapid increase in their surface area. Due to the fact that mechanical tissues do not form as quickly, young petioles initially hang down, as if withered, and the foliage seems to droop. The formation of the green pigment - chlorophyll - can also slow down, and young leaves turn out to be whitish or - due to the content of the anthocyanin pigment - reddish (see picture above).

"Dropping" of young leaves of the chocolate tree (Theobroma cacao)

The next feature of some trees in tropical rainforests is cauliflory, that is, the formation of flowers on trunks and leafless areas of branches. Since this phenomenon is observed primarily in trees of the lower tier of the forest, scientists interpret it as an adaptation to pollination with the help of bats, which is often found in these habitats (chiropterophily): when pollinating animals - bats and flying dogs - it is more convenient to grab onto the flowers when approaching a tree .

Birds also play a significant role in the transfer of pollen from flower to flower (this phenomenon is called “ornithophily”). Ornithophilous plants are noticeable due to the bright colors of their flowers (red, orange, yellow), while chiroptophilous plants have flowers that are usually inconspicuous, greenish or brownish.

A clear distinction between the layers of shrubs and grasses, as is, for example, characteristic of the forests of our latitudes, practically does not exist in tropical rainforests. We can only note the upper tier, which, along with tall, large-leaved representatives of the banana, arrowroot, ginger and aroid families, includes shrubs and young tree growth, as well as the lower tier, represented by low-growing, extremely shade-tolerant herbs. In terms of the number of species, herbaceous plants in tropical rainforests are inferior to trees; But there are also lowland humid forests that have not experienced human influence, in which only one species-poor layer of grasses is generally developed.

Noteworthy is the fact, which has not yet been explained, of variegated leaves, as well as the presence of metallic-shiny or matte-velvety areas of the surface of the leaves of plants living in the ground layer of grasses of a humid tropical forest. Obviously, these phenomena are to some extent related to the optimal use of the minimum sunlight that reaches such habitats. Many "variegated" plants of the lower layer of tropical rainforest grasses have become favorite indoor plants. ornamental plants, for example types of genera Zebrina, Tradescantia, Setcreasea, Maranta, Calathea, Coleus, Fittonia, Sanchezia, Begonia, Pilea etc. (picture on page 101). The deep shade is dominated by various ferns, club mosses ( Selaginella) and mosses; the number of their species is especially large here. Thus, most species of club mosses (and there are about 700 of them) are found in tropical rainforests.

Also noteworthy are the saprophytic (that is, using decaying organic matter) fungi of the families Clathraceae and Phallaceae living on the soil of tropical rainforests. They have peculiar fruiting bodies - “mushroom-flowers” ​​(see picture on page 102).

Lianas. If you float through a tropical rainforest along a river, you will be struck by the abundance of vines (plants that climb trees with woody stems) - they, like a thick curtain, cover the trees growing along the banks. Lianas are one of the most amazing components of tropical vegetation: over 90% of all their species are found only in the tropics. Most grow in moist forests, although they require good light to thrive. That is why they do not occur with the same frequency everywhere. First of all, they can be seen along forest edges, in naturally formed bright areas of the forest and - at least sometimes - in the layers of woody plants permeable to sunlight (see picture on page 106). They are especially abundant on plantations established in tropical rainforests and in secondary forests that appear in cleared areas. In lowland humid forests that have not experienced human influence, where dense, well-developed tree crowns are tightly closed, vines are relatively rare.

According to the method of attachment to plants that serve as their support, vines can be divided into different groups. For example, supporting vines can be held on other plants with the help of supporting (clinging) shoots or leaves, thorns, thorns, or special outgrowths such as hooks. Typical examples of such plants are rattan palms of the genus Calamus, 340 species of which are distributed in the tropics of Asia and America (see figure on page 103).

Root-fixed vines are held on a support with the help of many small adventitious roots or cover it with longer and thicker roots. These are many shade-tolerant vines from the aroid family, for example species of the genera Philodendron, Monstera, Raphidophora, Syngonium, Pothos, Scindapsus, as well as vanilla ( Vanilla) - a genus from the orchid family.

Climbing vines cover the support with internodes that grow greatly in length. Usually, as a result of subsequent thickening and lignification, such shoots are firmly fixed. The climbing group includes most tropical vines, for example, representatives of the mimosa family, rich in species and widespread throughout the tropics, and the related family Caesalpiniaceae, in particular climbing entada ( Entada scandens); the latter's beans reach 2 m in length (see picture on page 104). The so-called monkey's ladder, or Bauhinia sarsaparilla ( Bauhinia smilacina), forming thick woody shoots, as well as vines with fancy flowers (Kirkazon spp., Aristolochia; family Kirkazonaceae) (see picture on page 103).

Finally, vines attached with tendrils form woody tendrils - with them they cling to plants that serve as support for them. These include representatives of the genus widespread throughout the tropics Cissus from the Vinogradov family, various types of legumes, in particular (see picture), as well as types of passionflower ( Passiflora; passionflower family).

Epiphytes. Extremely interesting are the adaptations to living conditions in tropical rainforests of the so-called epiphytes - plants living on trees. The number of their species is very large. They abundantly cover the trunks and branches of trees, thanks to which they are quite well lit. Developing high on trees, they lose the ability to obtain moisture from the soil, so water supply becomes a vital factor for them. It is not surprising that there are especially many types of epiphytes where precipitation is heavy and the air is humid, but for their optimal development, it is not the absolute amount of moisture that falls that is decisive, but the number of rainy and foggy days. The unequal microclimate of the upper and lower tree layers is also the reason that the communities of epiphytic plants living there differ greatly in species composition. Light-loving epiphytes dominate in the outer parts of the crowns, while shade-tolerant ones dominate inside, in constantly wet habitats. Light-loving epiphytes are well adapted to the alternation of dry and wet periods of time that occurs during the day. As the following examples show, they use different options to do this (figure on page 105).

In orchids, represented by a huge number of species (and most of the 20,000-25,000 species of orchids are epiphytes), thickened sections of shoots (the so-called bulbs), leaf blades or roots serve as organs that store water and nutrients. This lifestyle is also facilitated by the formation of aerial roots, which are covered on the outside with layers of cells that quickly absorb water (velamen).

Tropical rainforest plants growing in the subsoil layer

The bromeliad or pineapple family (Bromeliaceae), the representatives of which are distributed, with one exception, in North and South America, consists almost exclusively of epiphytes, whose funnel-like rosettes of leaves serve as drainage reservoirs; from them, water and nutrients dissolved in it can be absorbed by the scales located at the base of the leaves. Roots serve only as organs that attach plants.

Even cacti (for example, species of genera Epiphyllum, Rhipsalis, Hylocereus And Deamia) grow as epiphytes in montane tropical rainforests. With the exception of a few species of the genus Rhipsalis, also found in Africa, Madagascar and Sri Lanka, all of them grow only in America.

Some ferns, for example, bird's nest fern, or asplenium nest ( Aspleniumnidus), and staghorn fern, or Platycerium staghorn fern ( Platycerium), due to the fact that the leaves of the first form a funnel-shaped rosette, and the second has special leaves adjacent to the trunk of the support tree, like patch pockets (picture on page 105), they are even capable of creating a soil-like, constantly moist substrate into which their roots grow.

Epiphytes that develop in shaded habitats are represented primarily by so-called hygromorphic ferns and mosses, which have adapted to existence in a humid atmosphere. The most characteristic components of such communities of epiphytic plants, especially pronounced in mountain moist forests, are hymenophyllous, or thin-leaved, ferns (Hymenophyllaceae), for example, representatives of the genera Hymenophyllum And Trichomanes. As for lichens, due to their slow growth they do not play such a big role. Of the flowering plants in these communities there are species of the genera Peperomia And Begonia.

Even leaves, and especially the leaves of trees in the lower tiers of a tropical rainforest, where air humidity is constantly high, can be inhabited by various lower plants. This phenomenon is called epiphylly. Mostly lichens, liver mosses and algae settle on the leaves, forming characteristic communities.

Hemiepiphytes are a kind of intermediate stage between epiphytes and lianas. They either grow first as epiphytes on tree branches, and as aerial roots form and reach the soil, they become plants that independently strengthen in the soil, or in the early stages they develop as vines, but then lose contact with the soil and thus turn into epiphytes. The first group includes the so-called strangler trees; their aerial roots, like a network, cover the trunk of the support tree and, growing, prevent its thickening so much that the tree eventually dies. And the collection of aerial roots then becomes like a system of “trunks” of an independent tree, which in the early stages of development was an epiphyte. The most typical examples of strangler trees in Asia are species of the genus Ficus(mulberry family), and in America - representatives of the genus Clusia(St. John's wort family). The second group includes species of the aroid family.

Evergreen lowland tropical rainforests. Although the floristic composition of tropical rainforests in different regions of the globe is very different, and the three main areas of such forests show only slight similarities in this respect, nevertheless, in the nature of their vegetation cover, similar modifications of the main type can be detected everywhere.

The prototype of a tropical rainforest is considered to be an evergreen moist tropical forest of non-flooding lowlands that are not damp for a long time. This is, so to speak, a normal type of forest, the structure and features of which we have already talked about. Forest communities of river floodplains and flooded lowlands, as well as swamps, usually differ from it in a less rich species composition and the presence of plants that have adapted to exist in such habitats.

Floodplain tropical rainforests found in close proximity to rivers in regularly flooded areas. They develop in habitats formed by the annual deposition of nutrient-rich river sediment - tiny particles carried by the river suspended in the water and then settled. The so-called “white-water” rivers bring this muddy water mainly from the treeless areas of their basins *. The optimal content of nutrients in the soil and the relative supply of running water with oxygen determine the high productivity of plant communities developing in such habitats. Floodplain tropical forests are difficult for human development, so they have largely retained their pristine nature to this day.

* (Rivers that the authors of this book call “white-water” are usually called white (rios blancos) in Brazil, and “black-water” rivers are called black (rios negros). White rivers carry muddy water, rich in suspended particles, but the color of the water in them can be not only white, but also gray, yellow, etc. In general, the rivers of the Amazon basin are characterized by an amazing variety of water colors. Black rivers are usually deep; The waters in them are transparent - they appear dark only because there are no suspended particles in them that reflect light. Humic substances dissolved in water only enhance this effect and, apparently, affect the color shade.)

Rainforest vines

Moving from the very bank of the river across the floodplain to its edge, one can identify a characteristic sequence of plant communities caused by a gradual decrease in the soil surface level from high riverbed banks to the edge of the floodplain. On rarely flooded river-bed banks, a river-bed forest rich in lianas grows, further from the river it turns into a real flooded forest. At the edge of the floodplain farthest from the shore there are lakes surrounded by reed or grass swamps.

Swampy rain forest. Swampy tropical rain forests grow in habitats where the soil is almost constantly covered by standing or slowly flowing water. They can be found mainly near the so-called “black water” rivers, the sources of which are in forested areas. Therefore, their waters do not carry suspended particles and have a color from olive to black-brown due to the content of humic substances in them. The most famous "blackwater" river is the Rio Negro, one of the most important tributaries of the Amazon; it collects water from a vast territory with podzolic soils.

Unlike floodplain tropical rainforest, swamp forest typically covers the entire river valley. There is no deposition of pumps here, but, on the contrary, only uniform leaching, so the surface of the valley of such a river is flat.

Due to the lack of nutrients in the habitat, swampy rainforests are not as lush as floodplain ones, and due to the lack of air in the soil, plants with aerial and stilted roots are often found here. For the same reason, the decomposition of organic matter occurs slowly, which contributes to the formation of thick peat-like layers, most often consisting of more or less decomposed wood.

Semi-evergreen lowland moist forests. Some areas of tropical rainforest are characterized by short dry periods, causing the leaves of the trees in the upper layer of the forest to change. At the same time, the lower tree layers remain evergreen. This transitional stage to dry forests leafed out during the rainy season (see p. 120) is called “semi-evergreen, or semi-deciduous, moist lowland forests.” During dry periods, moisture in the soil can move from bottom to top here, so such forests receive enough nutrients and are very productive.

Epiphytes of tropical rainforest

Asplenium nesting Asplenium nidus above and Cattleya citrina below

Mountain tropical rain forests. The forests described above, the existence of which is determined by the presence of water, can be contrasted with such variants of tropical rainforest, the formation of which is associated with a decrease in temperature; they are mainly found in wet habitats located in different altitudinal zones mountain areas tropical regions. In the foothill zone, at an altitude of approximately 400-1000 m above sea level, the tropical rainforest is almost indistinguishable from the lowland forest. There are only two tiers of trees, and the trees on the upper tier are not so tall.

But the tropical rain forest of the mountain belt, or, as they say, mountain rain forest, growing at an altitude of 1000-2500 m, reveals more significant differences. It also has two tree layers, but they are often difficult to identify, and their upper limit often does not exceed 20 m. In addition, here fewer species trees than in the humid forests of the lowlands, and some characteristics trees of such forests, in particular stilted roots, as well as cauliflory. Tree leaves are usually smaller and do not have points to remove water droplets.

Shrub and grass layers are often dominated by ferns and bamboo species. Epiphytes are very abundant, while large vines are rare.

For more high altitudes constantly humid tropics (2500-4000 m) mountain rainforests are replaced by subalpine mountain forests developing at cloud level (see vol. 2).

Tropical forests are forests that grow in tropical and subtropical regions. Tropical forests cover about six percent of the Earth's land surface. There are two main types of tropical forests: tropical rainforests (such as those in the Amazon or Congo Basin) and tropical dry forests (such as those in southern Mexico, the plains of Bolivia, and the western regions of Madagascar).

Tropical forests typically have four distinct layers that define the structure of the forest. The tiers include the forest floor, understory, canopy (forest canopy), and overstory. The forest floor, the darkest place in the rainforest, receives little sunlight. The undergrowth is the layer of forest between the ground and up to a height of about 20 meters. It includes shrubs, grasses, small trees and trunks of large trees. Forest canopy - represents a canopy of tree crowns at a height of 20 to 40 meters. This tier consists of interlacing crowns of tall trees on which many tropical forest animals live. Most food resources in the rainforest are found in the upper canopy. The upper layer of the tropical forest includes the crowns of the tallest trees. This tier is located at an altitude of about 40-70 meters.

Main Characteristics of the Rainforest

The following are the main characteristics of tropical forests:

• tropical forests are located in the tropical and subtropical regions of the planet;
• rich in species diversity of flora and fauna;
• there is a large amount of precipitation here;
• tropical forests are under threat from logging for timber, agriculture and livestock grazing;
• The structure of a tropical forest consists of four layers (forest floor, understory, canopy, overstory).

Classification of tropical forests

• Tropical rainforests, or tropical rainforests, are forested habitats that receive high rainfall throughout the year (usually more than 200 cm per year). Wet forests located close to the equator and receive enough sunlight to maintain the average annual air temperature at a fairly high level (between 20° and 35° C). Tropical rainforests are among the most species-rich habitats on Earth. They grow in three main areas around the world: Central and South America, West and Central Africa and Southeast Asia. Of all the tropical rainforest regions, South America is the largest in the world: it covers about 6 million square kilometers.
• Tropical dry forests are forests that receive less rainfall than tropical rain forests. Dry forests generally have a dry season and a rainy season. Although rainfall is sufficient to support adequate vegetation growth, trees must be able to withstand long periods of drought. Many species of trees that grow in tropical dry forests are deciduous and shed their leaves during the dry season. This allows trees to reduce their water needs during the dry season.

Rainforest Animals

Examples of several animals that inhabit tropical forests:

• (Panthera onca) is a large representative of the cat family that lives in the tropical forests of Central and South America. The jaguar is the only panther species living in the new world.
• The capybara, or capybara (Hydrochoerus hydrochaeris) is a semi-aquatic mammal that inhabits the forests and savannas of South America. Capybaras are the largest representative of the order of rodents living today.
• Howler monkeys (Aloautta) are a genus of monkeys that includes fifteen species inhabiting tropical forests throughout Central and South America.

You can find out more information about the animals of the Amazon rain forest in the article "".