Natural areas of other continents. Natural areas of the southern continents. Literature for preparing for the State Exam and the Unified State Exam

Earth's surface and moisture conditions in different parts On the continents, natural zones do not form continuous strips parallel to the equator. Only in and on some large plains do they extend in the latitudinal direction, replacing each other from north to south. More often they change in the direction from the coasts of the oceans to the interior of the continents, and sometimes they stretch almost along the meridians.

Natural areas are also formed in: from the equator to the poles, the properties of surface waters, the composition of vegetation and fauna change. There is also. However, oceanic natural complexes do not have pronounced external differences.

There is great diversity on Earth. However, against the background of this diversity, large parts stand out - natural areas and. This is due to the different ratio of heat and moisture that the earth's surface receives.

Formation of natural areas

Uneven distribution solar heat over the Earth's surface - the main reason for the heterogeneity of the geographical envelope. In almost every landmass, the oceanic parts are better moistened than the interior, continental areas. Humidification depends not only on the amount of precipitation, but also on the ratio of heat and moisture. The warmer it is, the more moisture that falls with precipitation evaporates. The same amount of precipitation can lead to excessive moisture in one zone and insufficient moisture in another. Thus, the annual precipitation amount of 200 mm in the cold subarctic zone is excessive (swamps are formed), and in hot tropical zones it is sharply insufficient (deserts exist).

Due to differences in the amount of solar heat and moisture, natural zones are formed within geographical zones - large areas with uniform temperature and humidification conditions, surface and groundwater, similar, and the animal world.

Features of the natural zones of the continents

In the same natural areas on different continents flora and fauna have similar features.

At the same time, the characteristics of the distribution of plants and animals, in addition to climate, are influenced by other factors: geological history continents, relief and features of rocks, people. The unification and separation of continents, changes in their topography and climate in the geological past became the reason that in similar natural conditions, but live on different continents different types plants and animals. For African savannas, for example, antelopes, buffalos, zebras, African ostriches, and in South America there are several species of deer, armadillos and the ostrich-like flightless bird rhea. On each continent there are endemic species (endemics), characteristic only of that continent.

Under influence human activity geographic envelope undergoes significant changes. To retain representatives organic world and typical natural complexes in all natural areas of the world, specially protected areas are created - nature reserves, etc. national parks, in contrast, nature conservation is combined with tourism and people's recreation.

The natural complexes of the Earth are very diverse. These are hot and icy deserts, evergreen forests, endless steppes, and bizarre mountains. This diversity is the unique beauty of our planet.

You already know how natural complexes, “continents”, “oceans” were formed. But the nature of each continent, like each ocean, is not the same. Various natural zones are formed on their territory.

Topic: Nature of the Earth

Lesson: Natural Areas of the Earth

1. Today we will find out

Why are natural areas formed?

On the patterns of distribution of natural zones,

Features of natural zones of continents.

2. Formation of natural areas

A natural zone is a natural complex with uniform temperatures, moisture, similar soils, flora and fauna. A natural area is called according to the type of vegetation. For example, taiga, deciduous forests.

The main reason for the heterogeneity of the geographic envelope is the uneven redistribution of solar heat on the Earth's surface.

In almost every climatic zone of land, the oceanic parts are moistened more than the internal, continental ones. And this depends not only on the amount of precipitation, but also on the ratio of heat and moisture. The warmer it is, the more moisture that falls with precipitation evaporates. The same amount of moisture can lead to excess moisture in one zone and insufficient moisture in another.

Rice. 1. Swamp

Thus, the annual precipitation amount of 200 mm in the cold subarctic zone is excessive moisture, which leads to the formation of swamps (see Fig. 1).

And in hot tropical zones it is sharply insufficient: deserts are formed (see Fig. 2).

Rice. 2. Desert

Due to differences in the amount of solar heat and moisture, natural zones are formed within geographic zones.

3. Patterns of placement

In the placement of natural areas on earth's surface a clear pattern is visible, which can be clearly seen on the map of natural zones. They extend in the latitudinal direction, replacing each other from north to south.

Due to the heterogeneity of the relief of the earth's surface and moisture conditions in different parts of the continents, natural zones do not form continuous strips parallel to the equator. More often they change in the direction from the coasts of the oceans to the interior of the continents. In the mountains, natural zones replace each other from the foothills to the peaks. This is where the altitudinal zone appears.

Natural zones are also formed in the World Ocean: from the equator to the poles, the properties of surface waters, the composition of vegetation and fauna change.

Rice. 3. Natural areas of the world

4. Features of the natural zones of the continents

In the same natural zones on different continents, the flora and fauna have similar features.

However, in addition to climate, the distribution of plants and animals is influenced by other factors: the geological history of the continents, relief, and people.

The unification and separation of continents, changes in their topography and climate in the geological past became the reason that different species of animals and plants live in similar natural conditions, but on different continents.

For example, African savannas are characterized by antelopes, buffalos, zebras, and African ostriches, and in South American savannas several species of deer and the ostrich-like flightless bird rhea are common.

On every continent there are endemics - both plants and animals that are unique to that continent. For example, kangaroos are found only in Australia, and polar bears are found only in the Arctic deserts.

Geofocus

The Sun heats the spherical surface of the Earth unequally: the areas above which it stands high receive the most heat.

Above the poles, the rays of the Sun only glide over the Earth. The climate depends on this: hot at the equator, harsh and cold at the poles. The main features of the distribution of vegetation and fauna are also associated with this.

Moist evergreen forests are located in narrow stripes and spots along the equator. “Green Hell” - this is what many travelers of past centuries who visited here called these places. Tall multi-tiered forests stand as a solid wall, under the thick crowns of which darkness, monstrous humidity, constant heat, there is no change of seasons, rainfalls regularly fall with an almost continuous stream of water. The forests of the equator are also called permanent rain forests. The traveler Alexander Humboldt called them “hyleia” (from the Greek hyle - forest). Most likely, this is what wet forests looked like Carboniferous period with giant ferns and horsetails.

Rain forests South America called “selva” (see Fig. 4).

Rice. 4. Selva

Savannas are a sea of ​​grasses with rare islands of trees with umbrella crowns (see Fig. 5). The vast expanses of these amazing natural communities are located in Africa, although there are savannas in South America, Australia, and India. A distinctive feature of savannas is the alternation of dry and wet seasons, which take about six months, replacing each other. The fact is that for subtropical and tropical latitudes Where savannas are located, a change in two different air masses is characteristic - humid equatorial and dry tropical. Significantly influence the climate of savannas monsoon winds bringing seasonal rains. Because these landscapes are located between very wet natural areas equatorial forests and very dry desert areas, they are constantly influenced by both. But moisture is not present long enough in savannas for multi-tiered forests to grow there, and arid ones “ winter periods"in 2-3 months they do not allow the savannah to turn into a harsh desert.

Rice. 5. Savannah

The natural taiga zone is located in the north of Eurasia and North America (see Fig. 6). On the North American continent it stretches from west to east for more than 5 thousand km, and in Eurasia, starting on the Scandinavian Peninsula, it spread to the coast Pacific Ocean. The Eurasian taiga is the largest continuous forest zone on the ground. It occupies more than 60% of the territory Russian Federation. The taiga contains huge reserves of wood and supplies a large number of oxygen into the atmosphere. In the north, the taiga smoothly turns into forest-tundra, gradually taiga forests are replaced by open forests, and then by separate groups of trees. The taiga forests extend farthest into the forest-tundra along river valleys, which are most protected from strong northern winds. In the south, the taiga also smoothly transitions into coniferous-deciduous and broad-leaved forests. In these areas, humans have interfered with the natural landscapes for many centuries, so now they represent a complex natural-anthropogenic complex.

Rice. 6. Taiga

Under the influence of human activity, the geographical environment is changing. Swamps are drained, deserts are irrigated, forests disappear, and so on. This changes the appearance of natural areas.

Homework

Read § 9. Answer the questions:

· What determines the moisture content of an area? How various conditions Do moisturizers affect natural complexes?

· Are there natural areas in the ocean?

Bibliography

MainI

1. Geography. Land and people. 7th grade: Textbook for general education. uch. / A. P. Kuznetsov, L. E. Savelyeva, V. P. Dronov, “Spheres” series. – M.: Education, 2011.

2. Geography. Land and people. 7th grade: atlas, “Spheres” series.

Additional

1. N. A. Maksimov. Behind the pages of a geography textbook. – M.: Enlightenment.

Literature for preparing for the State Exam and the Unified State Exam

The warmth of the sun, clean air and water are the main criteria for life on Earth. Numerous climatic zones have led to the division of the territory of all continents and waters into certain natural zones. Some of them, even separated by huge distances, are very similar, others are unique.

Natural areas of the world: what are they?

This definition should be understood as very large natural complexes (in other words, parts geographical zone Earths), which have similar, homogeneous climatic conditions. The main characteristic of natural areas is animals and vegetable world, which inhabits this territory. They are formed as a result of the uneven distribution of moisture and heat on the planet.

Table “Natural areas of the world”

This characteristic of the natural zones of the world is only for informational purposes, because you can talk about each of them for a very long time, and all the information will not fit into the framework of one table.

Natural zones of the temperate climate zone

1. Taiga. It surpasses all other natural zones of the world in terms of land area (27% of the territory of all forests on the planet). It is characterized by very low winter temperatures. Deciduous trees they cannot be maintained, so the taiga is dense coniferous forests (mainly pine, spruce, fir, larch). Very large areas of the taiga in Canada and Russia are occupied by permafrost.

2. Mixed forests. Characteristic in to a greater extent for the Northern Hemisphere of the Earth. It is a kind of border between taiga and deciduous forest. They are more resistant to cold and long winters. Tree species: oak, maple, poplar, linden, as well as rowan, alder, birch, pine, spruce. As the table "Natural zones of the world" shows, soils in the zone mixed forests gray, not very fertile, but still suitable for growing plants.

3. Broad-leaved forests. They are not adapted to harsh winters, are deciduous. They occupy most of Western Europe, the south of the Far East, northern China and Japan. Suitable for them is a maritime or temperate continental climate with hot summers and sufficient warm winter. As the table “Natural zones of the world” shows, the temperature in them does not fall below -8°C even in the cold season. The soil is fertile, rich in humus. The following types of trees are typical: ash, chestnut, oak, hornbeam, beech, maple, elm. The forests are very rich in mammals (ungulates, rodents, predators), birds, including game birds.

4. Temperate deserts and semi-deserts. Their main distinctive feature- almost complete absence of vegetation and sparse fauna. There are quite a lot of natural areas of this nature; they are located mainly in the tropics. There are temperate deserts in Eurasia, and they are characterized by sharp changes in temperature across the seasons. Animals are represented mainly by reptiles.

Arctic deserts and semi-deserts

They are huge areas of land covered with snow and ice. A map of the world’s natural zones clearly shows that they are located in North America, Antarctica, Greenland and the northern tip of the Eurasian continent. In fact, these are lifeless places, and only along the coast are polar bears, walruses and seals, arctic foxes and lemmings, and penguins (in Antarctica). Where the ground is free of ice, lichens and mosses can be seen.

Equatorial rainforests

Their second name is rain forests. They are located mainly in South America, as well as in Africa, Australia and the Greater Sunda Islands. The main condition for their formation is constant and very high humidity (more than 2000 mm of precipitation per year) and a hot climate (20°C and above). They are very rich in vegetation, the forest consists of several tiers and is an impenetrable, dense jungle, which has become home to more than 2/3 of all types of creatures now living on our planet. These rain forests are superior to all other natural areas in the world. The trees remain evergreen, changing foliage gradually and partially. Surprisingly, the soil rain forests contain little humus.

Natural zones of the equatorial and subtropical climate zone

1. Variably humid forests, they differ from rain forests in that precipitation falls there only during the rainy season, and during the period of drought that follows, the trees are forced to shed their leaves. The flora and fauna are also very diverse and rich in species.

2. Savannas and woodlands. They appear where moisture, as a rule, is no longer enough for growth variable-humid forests. Their development occurs in the interior of the continent, where tropical and equatorial climates predominate. air masses, and the rainy season lasts less than six months. They occupy a significant part of the territory of subequatorial Africa, the interior of South America, partly Hindustan and Australia. More detailed information about the location is reflected in the map of natural areas of the world (photo).

Hardleaf forests

This climate zone is considered the most suitable for human habitation. Hard-leaved and evergreen forests are located along sea and ocean coasts. Precipitation is not so abundant, but the leaves retain moisture due to their dense leathery shell (oaks, eucalyptus), which prevents them from falling. In some trees and plants they are modernized into spines.

Steppes and forest-steppes

They are characterized by an almost complete absence of woody vegetation, due to the poor level of precipitation. But the soils are the most fertile (chernozems), and therefore are actively used by humans for farming. The steppes occupy large areas in North America and Eurasia. The predominant number of inhabitants are reptiles, rodents and birds. Plants have adapted to the lack of moisture and most often manage to complete their life cycle for a short spring period when the steppe is covered with a thick carpet of greenery.

Tundra and forest-tundra

In this zone the breath of the Arctic and Antarctic begins to be felt, the climate becomes more severe, and even coniferous trees cannot withstand it. There is an abundance of moisture, but there is no heat, which leads to swamping of very large areas. There are no trees at all in the tundra; the flora is mainly represented by mosses and lichens. It is considered to be the most unstable and fragile ecosystem. Due to the active development of gas and oil fields, it is on the verge of an environmental disaster.

All natural areas of the world are very interesting, be it the seemingly absolutely lifeless desert, the endless arctic ice or thousand-year-old rain forests with boiling life inside.

Natural area - a territory with similar conditions of temperature and moisture, which determine generally homogeneous soils, vegetation and fauna. On the plains, the zones extend in the latitudinal direction, naturally replacing each other from the poles to the equator. Often, significant distortions in the pattern of the zone are introduced by the relief and the relationship between land and sea.

Arctic and Antarctic deserts . These are cold deserts with very low air temperatures in the Arctic and Antarctica. In this area, snow and ice remain almost all year round. In the warmest month - August - in the Arctic the air temperature is close to 0°C. Ice-free areas are bound by permafrost. Very intense frost weathering. There is little precipitation - from 100 to 400 mm per year in the form of snow. In this zone, the polar night lasts up to 150 days. Summer is short and cold. Only 20 days, rarely 50 days a year, the air temperature exceeds 0°C. The soils are thin, underdeveloped, rocky, and there are widespread scatterings of coarsely broken material. Less than half of the Arctic and Antarctic deserts are covered with sparse vegetation. It is devoid of trees and bushes. Crucible lichens, mosses, various algae, and only some flowering plants are common here. Animal world richer than vegetable. These are polar bears, arctic foxes, polar owls, deer, seals, and walruses. Among the birds, there are penguins, eiders and many other birds that nest on rocky shores and form “bird colonies” in the summer. In the ice desert zone, marine animals are hunted; among birds, eiders are of particular interest, with their nests lined with down. Eider down is collected from abandoned nests to produce clothing worn by polar sailors and pilots. In the icy desert of Antarctica there are Antarctic oases. These are areas of the continental coastal strip free from ice cover, with an area of ​​​​several tens to hundreds of square meters. kilometers. The organic world of oases is very poor; there are lakes.

Tundra. This is an area that lies within parts of the Arctic and subarctic zones in the Northern Hemisphere; in the Southern Hemisphere, the tundra is distributed only on some islands. This is an area with a predominance of moss-lichen vegetation, as well as low-growing perennial grasses, shrubs and low bushes. The trunks of shrubs and the roots of grasses are hidden in the moss and lichen turf.

The climate of the tundra is harsh, the average July temperature only in the south of the natural zone does not exceed +11°C, snow cover lasts 7-9 months. Precipitation amounts to 200-400 mm, and in some places up to 750 mm. main reason treeless tundra - low temperatures air in combination with high relative humidity, strong winds, widespread permafrost. The tundra also creates unfavorable conditions for the germination of seeds of woody plants on the moss-lichen cover. Plants in the tundra are pressed to the surface of the soil, forming densely intertwined shoots in the form of a pillow. In July, the tundra is covered with a carpet of flowering plants. Due to excess moisture and permafrost, there are many swamps in the tundra. On the warmed banks of rivers and lakes you can find poppies, dandelions, polar forget-me-nots, and pink myrtle flowers. Based on the predominant vegetation in the tundra, 3 zones are distinguished: arctic tundra , characterized by sparse vegetation due to the severity of the climate (in July +6°C); moss-lichen tundra , characterized by richer vegetation (in addition to mosses and lichens, sedge, bluegrass, and creeping willow are found here), and shrub tundra , located in the south of the tundra zone and characterized by richer vegetation, which consists of thickets of willow and alder bushes, which in some places rise to the height of a person. In areas of this subzone, shrubs are an important source of fuel. The soil of the tundra zone is predominantly tundra-gley, characterized by gleying (see “Soils”). She is infertile. Frozen soils with a thin active layer are widespread. The fauna of the tundra is represented by reindeer, lemmings, arctic foxes, ptarmigan, and in summer - many migratory birds. Shrub tundra gradually turns into forest-tundra.

Forest-tundra . This is a transition zone between the tundra and forest zones temperate zone. It is distributed in the Northern Hemisphere in North America and Eurasia. The climate is less severe than in the tundra: the average July temperature here is +10-14°C. The annual precipitation is 300-400 mm. There is more precipitation in the forest-tundra than evaporates, so the forest-tundra is characterized by excessive moisture; it is one of the most swampy natural zones. Snow cover lasts for more than six months. Floods on the rivers of the forest-tundra usually occur in the summer, since the rivers of this zone are fed by melt water, and the snow melts in the forest-tundra in the summer. Woody vegetation that appears in this zone grows along river valleys, since rivers have a warming effect on the climate of this zone. The forest islands consist of birch, spruce, and larch. The trees are stunted and in some places bent to the ground. The area of ​​forests increases in the forest-tundra as you move along it to the south. In the interfluves there are low-growing and sparse forests. Thus, the forest-tundra consists of an alternation of treeless shrub areas and open forests. Tundra (peat-swamp) or forest soils. The fauna of the forest-tundra is similar to the fauna of the tundra. It is also home to Arctic foxes, ptarmigan, snowy owls and a wide variety of migratory waterfowl. The forest-tundra contains the main winter pastures for reindeer and hunting grounds.

Temperate forests . This natural zone is located in a temperate climate zone and includes subzones taiga, mixed and deciduous forests , monsoon forests temperate zone. Differences in climatic features contribute to the formation of vegetation characteristic of each subzone.

Taiga (Turk.). This zone coniferous forests located in northern North America and northern Eurasia. The climate of the subzone ranges from maritime to sharply continental with relatively warm summers (from 10°C to 20°C), and the lower the winter temperatures, the more continental the climate is (from -10°C in northern Europe to -50°C in northeastern Europe). Siberia). Permafrost is widespread in many areas of Siberia. The subzone is characterized by excessive moisture and, as a consequence, swampy interfluve spaces. There are two types of taiga: light coniferous And thoseconiferous. Light coniferous taiga - These are the least demanding pine and larch forests in terms of soil and climatic conditions, the sparse crown of which allows the sun's rays to reach the ground. Pines, having an extensive root system, have acquired the ability to use nutrients from infertile soils, which is used to stabilize soils. This feature allows these plants to grow in areas with permafrost. The shrub layer of the light-coniferous taiga consists of alder, dwarf birches, polar birches, polar willows, and berry bushes. This type taiga is widespread in Eastern Siberia. Dark coniferous taiga - These are conifers, consisting of numerous species of spruce, fir, and cedar. This taiga, unlike the light-coniferous taiga, has no undergrowth, since its trees are tightly closed, and it is quite gloomy in these forests. The lower tier consists of shrubs (lingonberries, blueberries, blueberries) and dense ferns. This type of taiga is common in the European part of Russia and Western Siberia.

The soils of the taiga zone are podzolic. They contain little humus, but when fertilized they can provide a high yield. In the taiga of the Far East there are acidic soils.

The fauna of the taiga zone is rich. There are numerous predators here that are valuable game animals: otter, marten, sable, mink, weasel. Large ones include wolves, bears, lynxes, and wolverines. In North America, bison and wapiti deer used to be found in the taiga zone. Now they live only in nature reserves. The taiga is also rich in rodents, the most typical of which are beavers, muskrats, squirrels, hares, and chipmunks. The world of birds is very diverse.

Temperate mixed forests . These are forests with various breeds trees: coniferous-broad-leaved, small-leaved and pine. This zone is located in the north of North America (on the border of the USA and Canada), and in Eurasia it forms a narrow strip between the taiga and the zone of broad-leaved forests. The mixed forest zone is also found in Kamchatka and Far East. In the Southern Hemisphere, this forest zone occupies small areas in southern South America and New Zealand.

The climate of the mixed forest zone is maritime or transitional to continental (towards the center of the continent), summers are warm, winters are moderately cold (in maritime climates with positive temperatures, and in more continental climate up to -10°С). There is sufficient moisture here. The annual amplitude of temperature fluctuations, as well as the annual amount of precipitation, vary from oceanic regions to the center of the continent.

The diversity of vegetation in the mixed forest zone of the European part of Russia and the Far East is explained by differences in climate. For example, on the Russian Plain, where precipitation falls all year round thanks to westerly winds coming from the Atlantic, European spruce, oak, elm, fir, beech - coniferous-deciduous forests.

The soils in the mixed forest zone are gray forest and soddy-podzolic, while in the Far East they are brown forest.

The fauna is similar to the fauna of the taiga and the deciduous forest zone. Elk, sable, and bear live here.

Mixed forests have long been subject to severe deforestation and loss. They are best preserved in North America and the Far East, and in Europe they are cut down for agricultural land - field and pasture lands.

Temperate broadleaf forests . They occupy the east of North America, Central Europe, and also form an altitudinal zone in the Carpathians, Crimea and the Caucasus. In addition, isolated pockets of broad-leaved forests are found in the Russian Far East, Chile, New Zealand and central Japan.

The climate is favorable for the growth of deciduous trees with a wide leaf blade. Here, moderate continental air masses bring precipitation from the oceans (from 400 to 600 mm) mainly in the warm season. The average temperature in January is -8°-0°C, and in July +20-24°C.

Beech, hornbeam, elm, maple, linden, and ash grow in the forests. In the deciduous forest zone of North America, species are found that are not found on other continents. These are American oak species. The predominant species here are trees with a powerful spreading crown, often entwined with climbing plants: grapes or ivy. To the south there are magnolias. For European broad-leaved forests, oak and beech are the most typical.

The fauna of this natural zone is close to the taiga, but there are animals such as black bears, wolves, minks, raccoons, which are not typical for the taiga. Many animals of the broad-leaved forests of Eurasia are under protection, as the number of individuals is sharply declining. These include animals such as bison and Ussuri tiger.

The soils under broad-leaved forests are gray forest or brown forest. This zone has been heavily developed by humans, forests have been cleared over large areas, and the lands have been plowed. In its true form, the zone of broad-leaved forests has been preserved only in areas inconvenient for arable farming and in nature reserves.

Forest-steppe . This natural zone is located within the temperate climate zone and represents a transition from forest to steppe, with alternating forest and steppe landscapes. It is widespread in the Northern Hemisphere: in Eurasia from the Danube Lowland to Altai, further in Mongolia and the Far East; in North America, this zone is located in the northern Great Plains and western Central Plains.

Forest-steppes are naturally distributed within continents between forest zones, which here choose the most humidified areas, and the steppe zone.

The climate of the forest-steppes is moderate continental: winters are snowy and cold (from -5°C to -20°C), summers are warm (+18°C to +25°C). In different longitudinal zones, forest-steppe varies in precipitation (from 400 mm to 1000 mm). Humidification is slightly below sufficient, evaporation is very high.

In the forests that alternate steppes, broad-leaved (oak) and small-leaved tree species (birch) are more common, and conifers are less common. The soils of the forest-steppe are mainly gray forest soils, which alternate with chernozems. Nature forest-steppe zone very much changed by human economic activity. In Europe and North America, the plowed area reaches 80%. Since in this zone fertile soils, then wheat, corn, sunflowers, sugar beets and other crops are grown here. The fauna of the forest-steppe zone includes species characteristic of the forest and steppe zones.

The West Siberian forest-steppe with numerous birch groves-kolok (singular number - kolok) is specific. Sometimes they have an admixture of aspen. The area of ​​individual pegs reaches 20-30 hectares. Numerous forests, alternating with areas of steppes, create the characteristic landscape of Southwestern Siberia.

Steppes . This is a landscape with a herbaceous vegetation type, located in the temperate and partly subtropical zone. In Eurasia, the steppe zone extends in a latitudinal direction from the Black Sea to Transbaikalia; in North America, the Cordillera distributes air flows in such a way that the zone of insufficient moisture and with it the steppe zone are located from north to south along the eastern edge of this mountainous country. In the Southern Hemisphere, the steppe zone is located within the subtropical climate of Australia and Argentina. Precipitation(from 250 mm to 450 mm per year) fall here irregularly and are insufficient for the growth of trees. Winter is cold, average temperature below 0°C, in some places down to -30°, with little snow. Summer is moderately hot - +20°С, +24°С, drought is common. Inland waters in the steppe are poorly developed, river flow is small, and rivers often dry up.

The undisturbed vegetation of the steppe is a thick grass cover, but undisturbed steppes throughout the world remain only in nature reserves: all steppes are plowed. Depending on the nature of vegetation in the steppe zone, three subzones are distinguished. They differ from each other in the predominant vegetation. This meadow steppes (bluegrass, bonfire, timothy), cereals and southern wormwood-cereals .

The soils of the steppe zone - chernozems - have a significant humus horizon, due to which they are very fertile. This is one of the reasons for the highly plowed area.

The fauna of the steppes is rich and diverse, but it has changed greatly under the influence of humans. Back in the 19th century, wild horses, aurochs, bison, and roe deer disappeared. Deer are pushed into forests, saigas - into virgin steppes and semi-deserts. Now the main representatives of the animal world of the steppes are rodents. These are gophers, jerboas, hamsters, voles. Bustards, little bustards, larks and others are occasionally seen.

Steppes and partly forest-steppes of temperate and sub tropical zones North America are called prairies . Currently they are almost completely plowed. Part of the American prairies is dry steppes and semi-deserts.

The subtropical steppe on the plains of South America, located mainly in Argentina and Uruguay, is called pump . In the eastern regions, where precipitation falls from the Atlantic Ocean, there is sufficient moisture, but to the west the aridity increases. Most of the pampa territory is plowed, but in the west there are still dry steppes with thorny bushes, used as pastures for livestock.

Semi-deserts and temperate deserts . In the south, the steppes turn into semi-deserts, and then into deserts. Semi-deserts and deserts are formed in dry climates, where there is a long and hot warm period (+20-25°C, sometimes up to 50°C), strong evaporation, which is 5-7 times the amount of annual precipitation (up to 300 mm in year). Poor surface runoff, poor development inland waters, there are many drying riverbeds, the vegetation is not closed, sandy soils heat up during the day, but quickly cool down during the cool night, which contributes to physical weathering. The winds dry out the land very strongly here. Temperate deserts differ from deserts of other geographical zones in colder winters (-7°C-15°C). Deserts and semi-deserts of the temperate zone are widespread in Eurasia from the Caspian lowland to the northern bend of the Yellow River, and in North America - in the foothills and basins of the Cordillera. In the Southern Hemisphere, temperate deserts and semi-deserts are found only in Argentina, where they occur in broken areas in the interior and foothills. Among the plants found here are steppe feather grass, fescue, wormwood and solyanka, camel thorn, agave, and aloe. Animals include saigas, turtles, and many reptiles. The soils here are light chestnut and brown desert, often saline. Under conditions of sharp temperature fluctuations during the day with little moisture, a dark crust forms on the surface of deserts - a desert tan. It is sometimes called protective, as it protects rocks from rapid weathering and destruction.

The main use of semi-deserts is grazing livestock (camels, fine-wool sheep). Farming of drought-resistant crops is possible only in oases. Oasis (from the Greek name for several populated places in the Libyan Desert) is a place where tree, shrub and herbaceous vegetation grows in deserts and semi-deserts, in conditions of more abundant surface and ground moisture compared to neighboring areas and areas. The sizes of oases vary: from ten to tens of thousands of kilometers. Oases are centers of population concentration, areas of intensive agriculture on irrigated lands (Nile Valley, Fergana Valley in Central Asia).

Deserts and semi-deserts of the subtropical and tropical zones . These are natural areas located in both hemispheres, on all continents along tropical zones increased atmospheric pressure. Most often, semi-deserts of the subtropical zone are located in the transitional part from deserts to mountain steppes in the form of an altitudinal zone in the inland parts of the Cordillera and Andes of America, in western Asia, Australia and especially widely in Africa. The climate of these deserts and semi-deserts climatic zones hot: the average temperature in summer rises to +35°C, and in the coldest months of winter it does not fall below +10°C. Precipitation is 50-200 mm, in semi-deserts up to 300 mm. Sometimes precipitation occurs in short bursts of rain, and in some areas there may be no precipitation for several years in a row. With a lack of moisture, the weathering crust is very thin.

Groundwater lies very deep and can be partially saline. Only plants that can tolerate overheating and dehydration can live in such conditions. They have a deeply branched root system and small leaves or spines that reduce evaporation from the leaf surface. Some plants have leaves that are pubescent or covered with a waxy coating, which protects them from sunlight. In the semi-deserts of the subtropical zone, cereals are common and cacti appear. In the tropical zone, the number of cacti increases, agaves and sand acacias grow, and various lichens are common on the stones. A characteristic plant for the Namib Desert, located in the tropical zone of South Africa, is amazing plant Velwigia, which has a short trunk, from the top of which two leathery leaves extend. Welwigia can be up to 150 years old. The soils are gray soils, gravelly, gray-brown, they are not very fertile, since the layer of humus is thin. The fauna of deserts and semi-deserts is rich in reptiles, spiders, and scorpions. There are camels, antelopes, and rodents are quite widespread. Agriculture in semi-deserts and deserts of the subtropical and tropical zones is also possible only in oases.

Hardleaf forests . This natural zone is located within the subtropical zone of the Mediterranean type. They mainly grow in southern Europe, northern Africa, southwest and southeast Australia. Some fragments of these forests are found in California, Chile (south of the Atacama Desert). Hard-leaved forests grow in a mild, moderately warm climate with hot (+25°C) and dry summers and cool and rainy winters. The average precipitation is 400-600 mm per year with rare and short-lived snow cover. The rivers are mainly fed by rain, and floods occur in the winter months. In conditions rainy winter grasses grow rapidly.

The fauna has been severely exterminated, but herbivorous and leaf-eating forms, many birds of prey and reptiles are characteristic. In the forests of Australia you can find the koala bear, which lives in trees and leads a nocturnal, sedentary lifestyle.

The territory of hard-leaved forests is well developed and has been significantly changed by human economic activity. Large areas of forest here have been cut down, and their place has been taken by oilseed plantations, orchards and pastures. Many tree species have hard wood, which is used as a building material, and oils, paints, and medicines are made from the leaves (eucalyptus). Large harvests of olives, citrus fruits, and grapes are harvested from the plantations of this zone.

Subtropical monsoon forests . This natural zone is located in the eastern parts of the continents (China, southeastern USA, eastern Australia, southern Brazil). It is located in conditions that are the most humid compared to other zones of the subtropical zone. The climate is characterized by dry winters and wet summers. Annual precipitation is greater than evaporation. The maximum amount of precipitation falls in summer due to the influence of monsoons, bringing moisture from the ocean. In the territory of monsoon forests, inland waters are quite rich, and fresh groundwater lies shallow.

Here, tall-stemmed trees grow on red soils and yellow soils. mixed forests, among which there are evergreen and deciduous, shedding their foliage during the dry season. Species composition plants may vary depending on soil conditions. The forests contain subtropical species of pines, magnolias, camphor laurel, and camellias. Swamp cypress forests are common on the flooded coasts of Florida in the United States and in the Mississippian lowlands.

The monsoon forest zone of the subtropical zone has been developed by man for a very long time. In place of cleared forests, there are field and pasture lands; rice, tea, citrus fruits, wheat, corn and industrial crops are grown here.

Forests of tropical and subequatorial zones . They are located along eastern Central America, the Caribbean islands, Madagascar, southeast Asia, and northeast Australia. There are clearly two seasons here: dry and wet. The existence of forests in the dry and hot tropical zone is possible only thanks to the precipitation that the monsoons bring from the oceans in summer. In the subequatorial belt, precipitation occurs in the summer, when equatorial air masses dominate here. Depending on the degree of moisture, forests of the tropical and subequatorial zones are distinguished permanently wet and seasonally wet(or variable-humid) forests. Seasonally wet forests are characterized by a relatively poor species composition of tree species, especially in Australia, where these forests consist of eucalyptus, ficus, and laurels. Often in seasonally wet forests there are areas where teak and sal grow. There are very few palm trees in the forests of this group. According to its species diversity of flora and fauna permanently moist forests close to equatorial. There are many palm trees, evergreen oaks, and tree ferns. There are many lianas and epiphytes of orchids and ferns. The soils located under forests are mainly lateritic. During the dry season (winter), most deciduous trees do not shed all their leaves, but some species remain completely bare.

Savannah . This natural zone is located mainly within the subequatorial climate, although it is also found within the tropical and subtropical zones. In the climate of this zone, the change in wet and dry seasons of the year is clearly expressed at consistently high temperatures (from + 15 ° C to + 32 ° C). As you move away from the equator, the period of the wet season decreases from 8-9 months to 2-3, and precipitation decreases from 2000 to 250 mm per year.

Savannas are characterized by a predominance of herbaceous cover, among which tall (up to 5 m) grasses dominate. Shrubs and single trees rarely grow among them. The grass cover near the borders with the equatorial belt is very thick and high, and near the borders with semi-deserts it is sparse. A similar pattern can be seen in trees: their frequency increases towards the equator. Among the savannah trees you can find a variety of palm trees, umbrella acacias, tree-like cacti, eucalyptus trees, and baobab trees that store water.

Savannah soils depend on the length of the rainy season. Closer to the equatorial forests, where the rainy season lasts up to 9 months, are red ferralite soils. Closer to the border of savannas and semi-deserts there are red-brown soils, and even closer to the border, where rain falls for 2-3 months, unproductive soils with a thin layer of humus are formed.

The fauna of savannas is very rich and diverse, as the high grass cover provides food for the animals. Elephants, giraffes, hippos, and zebras live here, which in turn attract lions, hyenas and other predators. The bird world of this zone is also rich. Sunbirds live here, ostriches - the largest birds on Earth, a secretary bird that hunts small animals and reptiles. There are a lot of termites in the savannah.

Savannas are widespread in Africa, where they occupy 40% of the continent's territory, in South America, Australia and India.

Tall grass savannas in South America, on the left bank of the Orinoco River, with a dense, mainly cereal grass cover, with individual specimens or groups of trees, are called llanos (from the Spanish plural of “plains”). The savannas of the Brazilian plateau, where the area of ​​intensive livestock farming is located, are called campos .

Today, savannas play a very important role in human economic life. Significant areas of this zone are plowed, grains, cotton, peanuts, jute, and sugar cane are grown here. In drier areas, livestock farming is developed. Many tree species are used on the farm, since their wood does not rot in water. Human activities often lead to desertification of savannas.

Equatorial rainforests . This natural zone is located in an equatorial and partly subequatorial climate. These forests are found in the Amazon, Congo, Malay Peninsula and Sunda Islands, as well as other smaller islands.

The climate here is hot and humid. Temperature all year round is +24-28°C. The seasons are not expressed here. Humid equatorial forests are located within an area of ​​low pressure, where, as a result of intense heating, upward air currents are formed and a lot of precipitation falls (up to 1500 mm per year) throughout the year.

On the coasts, where the wind from the ocean influences, precipitation falls even more (up to 10,000 mm). Precipitation falls evenly throughout the year. Such climatic conditions contribute to the development of lush evergreen vegetation, although, strictly speaking, trees change leaves: some shed them every six months, others after a completely arbitrary period, and others replace their leaves in parts. Flowering periods also vary, and are even more erratic. The most common cycles are ten and fourteen months. Other plants may bloom once every ten years. But at the same time, plants of the same species bloom at the same time so that they have time to pollinate each other. Plants in this zone have little branching.

The trees of humid equatorial forests have disc-shaped roots, large leathery leaves, the shiny surface of which saves them from excessive evaporation and the scorching rays of the sun, from the impacts of rain jets during heavy downpours. Many leaves end in a graceful spine. It's a tiny drain. In plants of the lower tier, the leaves, on the contrary, are thin and delicate. The upper tier of equatorial forests is formed by ficus and palm trees. In South America, ceiba grows in the upper tier, reaching a height of 80 m. Bananas and tree ferns grow in the lower tiers. Large plants are entwined with vines. There are many orchids on the trees of equatorial forests, epiphytes are also found, and sometimes flowers form directly on the trunks. For example, cocoa tree flowers. In the forest of the equatorial belt it is so hot and humid that favorable conditions are created for the development of moss and algae that cling to the crown and hang from the branches. They are epiphytes. Tree flowers in the crown cannot be pollinated by the wind because the air there is practically still. Therefore, they are pollinated by insects and small birds, which are lured by a brightly colored corolla or a sweet smell. The fruits of the plants are also brightly colored. This allows them to solve the problem of transporting seeds. The ripe fruits of many trees are eaten by birds and animals; the seeds are not digested and, together with the droppings, end up far from the parent plant.

There are many native plants in equatorial forests. These are primarily vines. They begin their life on the ground in the form of a small bush, and then, tightly wrapping themselves around the stem of a giant tree, they climb up. The roots are in the soil, so the plant’s nutrition does not come from the giant tree, but sometimes the use of these trees for support by vines can lead to oppression and death. Some ficus trees are also “robbers”. Their seeds germinate on the bark of a tree, the roots tightly grip the trunk and branches of this host tree, which begins to die. Its trunk is rotting, but the roots of the ficus have become thick and dense and are already able to support themselves.

Equatorial forests are home to many valuable plants, such as the oil palm, from the fruits of which palm oil is obtained. The wood from many trees is used to make furniture and is exported in large quantities. This group includes ebony, the wood of which is black or dark green. Many plants of equatorial forests produce valuable fruits, seeds, juice, and bark, which are used in technology and medicine.

The equatorial forests of South America are called selva . Selva is located in the periodically flooded area of ​​the Amazon River basin. Sometimes, when describing moist equatorial forests, the name is used hylea , sometimes these forests are called jungle , although, strictly speaking, jungles are the forest thickets of South and Southeast Asia located within the subequatorial and tropical climate.