Natural areas - Zonal natural complexes of the plains within the geographic belts of the Earth.
Within a single geographical shell, there are two types of natural complexes - zoned and azonal. Zonal natural complexes are subordinated to geographic latitude, azonal to other factors (especially those of the relief, composition of rocks, etc.) not directly related to the influx of sunlight and heat.
The largest zonal subdivision of the geographic shell is geographic zones. They differ in temperature conditions, features of atmospheric circulation, soils, vegetation, and fauna. In essence, geographic zones coincide with climatic zones, have the same names and also change from the equator to the poles. Inside the belts emit subordinate natural complexes - natural areas.
On Earth, there are following natural zones: Arctic desert, tundra, boreal forest, mixed forest, deciduous forest, forest, Steppe, monsoon and evergreen subtropical forest sclerophyllous letnesuhoy subtropical forest, monsoon rain forest, arid desert, semi-desert, arid steppe, semi-desert, grass savanna, tree savanna, dry tropical forests, tropical rain forests, alpine tundra and mountain forests.
| Fig. 55. Map of natural areas |
Under conditions of approximately the same number of sediments (less than 150–200 mm per year), in a cold thermal belt (in the tundra), swamps can develop, and in hot weather - deserts. With a large amount of precipitation, tropic forests are already appearing in the hot belt. The values of temperatures or precipitation, taken separately, will not allow to correctly predict the nature of the territory. It is important the ratio of heat and moisture, which determines the conditions fun. This is (along with the latitudinal position) the main thing that distinguishes natural zones from each other. Each natural zone has its own set of natural characteristics and their combinations.
Most clearly the differences between the zones appear in the vegetation cover. For example, in those areas where moisture is excessive, forests usually spread (Fig. 53), and where there is insufficient water (at the same latitude), steppes, semi-deserts and deserts. On those territories where moisture can evaporate as much as atmospheric siege falls, there are forest-steppe, vast areas of savannahs (Fig. 54). Material from the site
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| Fig. 54. Savannah |
Natural zones are mainly latitudinal elongated zonal natural complexes; they differ in the ratio of heat and moisture.
Natural areas of North America. To the latitude of the Great Lakes (the border of the United States and Canada), the natural zones follow each other in latitude, and to the south - in a meridional way. The following natural areas are represented in North America:
1. The zone of the Arctic desert. In this area are Greenland and most of the islands of the Canadian Arctic Archipelago. Here in places freed from snow and ice, on poor stony and marshy soils, mosses and lichens grow on short, cool summers.
2. The tundra zone. It occupies the north coast of North America and the islands adjacent to it. The southern boundary of the tundra in the west lies near the Arctic Circle, and as it moves eastward it enters more southern latitudes, capturing the coast of Hudson Bay and the northern part of the Labrador Peninsula. Here in the conditions of short and cool summer and permafrost peat bogs are widespread. In the northern part of the tundra mosses and lichens grow, and in the southern part there are marsh grasses, wild rosemary shrubs, blueberry and blueberry shrubs, undersized with twisted birch, willow, alder trunks. In the North American tundra foxes, polar wolves, caribou reindeer, white quail, etc. are found. In the summer, many migratory birds arrive here. In the coastal waters of the zone there are many seals, walrus. On the north coast of the mainland there is a polar bear.
3. Taiga zone. To the south, the tundra gradually passes into the forest-tundra, and then into coniferous forests or taiga. The taiga zone extends from west to east in a wide strip. Coniferous trees grow mainly in the taiga - black spruce, balsam fir, pine, American larch; there are also hardwoods - paper birch with smooth white bark, aspen. In the forests are found predatory animals - bears, wolves, lynx, foxes; There are deer, moose and valuable fur-bearing animals - sable, beaver, muskrat. In the rivers there are a lot of salmon fishes, on the islands there are rookery seals.
4. The zone of mixed and deciduous forests begins south of the taiga. In the eastern part of the continent there are alternating wet forests that reach as far as the Gulf of Mexico. In mixed forests dominated by yellow birch, sugar maple, beech, linden, white and red pine. For deciduous forests are characterized by different types of oaks, chestnut, sycamore and tulip tree.
5. The zone of evergreen tropical forests is located in the south of the Mississippi and Atlantic lowlands. The forests consist of oaks, magnolias, beeches and dwarf palm trees. Trees are twisted by lianas.
6. The forest-steppe zone begins west of the forest zone. Grassy vegetation prevails here. Steppes with tall grasses, mostly cereals, reaching a height of 1.5 m, in North America are called the prairies. In the valleys of the rivers and in humid depressed areas, woody vegetation occurs. Closer to the Cordillera, precipitation falls even less and vegetation becomes poorer; low grasses do not cover the whole earth and grow in separate bunches.
7. The zone of deserts and semi-deserts occupies a significant part of the inland plateaus of the Cordillera, the Mexican Highlands and the California coast. There are thorny bushes, cacti and wormwood on gray and brown soils, and solyanka on saline soils.
8. Zones of savanna and evergreen forests are located in Central America and on the slopes of the Caribbean.
Natural area - a territory with similar conditions of temperature and moisture, which determine in general homogeneous soils, vegetation and wildlife. On the plains, the zones extend in a latitudinal direction, regularly replacing each other from the poles to the equator. Often, significant distortions in the pattern of the zone introduce relief and the ratio of land and sea.
Arctic and Antarctic deserts . These are cold deserts with very low air temperatures in the Arctic and Antarctic. In this zone, snow and ice persists almost all year round. In the warmest month - August - in the Arctic, the air temperature is close to 0 ° С. Ice-free spaces are shackled with permafrost. Very intense frosty weathering. Precipitation is low - 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, air temperature exceeds 0 ° C. Soils are thin, underdeveloped, stony, placers of coarsely broken material are common. Less than half of the Arctic and Antarctic deserts are covered with sparse vegetation. It is devoid of trees and shrubs. Here, common lichens, mosses, various algae, only some flowering plants are common. The animal world is richer than the vegetable. These are polar bears, arctic foxes, polar owls, deer, seals, walruses. Of the birds there are penguins, eiders and many other birds nesting on the rocky shores and in the summer forming "bird markets". Sea animals are hunted in the zone of icy deserts; among birds, the eider is of particular interest, and its nests are lined with fluff. The eiderdown is collected from the abandoned nests for the production of clothing worn by polar sailors and pilots. In the icy desert of Antarctica, there are Antarctic oases. These are ice-free areas of the coastal strip of the continent, ranging in size from a few tens to hundreds of square meters. kilometers The organic world of oases is very poor, there are lakes.
Tundra. This space, which lies within the parts of the arctic and subarctic belts in the northern hemisphere, in the southern hemisphere, tundra is distributed only on some islands. This is a territory dominated by moss-lichen vegetation, as well as low-growing perennial grasses, shrubs and low-growing shrubs. Shrubs and grass roots are hidden in moss and lichen turf.
The climate of the tundra is severe, the average July temperature only in the south of the natural zone does not exceed + 11 ° С, the snow cover lasts 7-9 months. Rainfall 200-400 mm, and in some places up to 750 mm. The main cause of tundraless forests is low air temperatures combined with high relative humidity, strong winds, widespread permafrost. In the tundra there are also unfavorable conditions for the germination of seeds of woody plants on the moss-lichen cover. Plants in the tundra are pressed to the soil surface, forming densely intertwining pillow shoots. In July, the tundra is covered with a carpet of flowering plants. In the tundra, due to excessive moisture and permafrost, there are many swamps. On the warmed banks of rivers and lakes you can find poppies, dandelions, polar forget-me-nots, pink flowers of mytnik. According to the predominant vegetation in the tundra, there are 3 zones: arctic tundra characterized by sparse vegetation due to the severity of the climate (in July + 6 ° C); moss-lichen tundra characterized by richer vegetation (apart from mosses and lichens, there is sedge, bluegrass, willow), and bush 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 grow to human height. In areas of this subzone, the shrub is an important source of fuel. The soil of the tundra zone is predominantly tundra-gley, characterized by gleis (see “Soils”). She is infertile. Frozen ground with a thin active layer is ubiquitous everywhere. The fauna of the tundra is represented by reindeer, lemming, arctic fox, white partridge, and in the summer - by a multitude of migratory birds. Shrub tundra gradually goes into the forest tundra.
Forest tundra . This is the transition zone between the tundra and the zone of forests of the temperate zone. It is common 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. Annual precipitation is 300-400 mm. Rainfall in the forest tundra falls more than evaporates, so the forest tundra is characterized by excessive moisture, it is one of the most marshy natural areas. Snow cover lasts more than six months. The flood on the rivers of the forest-tundra usually occurs in summer, since the rivers of this zone feed on melt-water, and the snow melts in the forest-tundra in summer. The woody vegetation that appears in this zone grows along river valleys, as rivers have a warming effect on the climate of this zone. The islands of forests consist of birch, spruce, larch. Trees are stunted, sometimes bent to the ground. The forest area increases in the forest tundra when moving along it to the south. In the interfluves there are stunted and sparse forests. Thus, the forest-tundra is an alternation of treeless shrub and light forest. Soils of tundra (peat-bog) or forest soils The fauna of the forest-tundra is similar to the fauna of the tundra. Arctic foxes, white partridges, a polar owl and a wide variety of migratory waterfowl also live here. In the forest tundra are the main winter pastures of reindeer and hunting grounds.
Temperate forests . This natural zone is located in the temperate climate zone and includes subzones taiga, mixed and deciduous forests, monsoon forest temperate belt. Differences in climatic features contribute to the formation of vegetation characteristic of each subzone.
Taiga (Turk.). This coniferous forest zone is located in the north of North America and in the north of Eurasia. The climate of the subzone varies from sea to sharply continental with a relatively warm summer (from 10 ° C to 20 ° C), and the winter temperatures are lower, the more continental climate (from -10 ° C in northern Europe to -50 ° C in the northeast Siberia). In many regions of Siberia permafrost is widespread. Excessive moistening and, as a result, marshy inter-river spaces is characteristic of the subzone. There are two types of taiga: light conifer and by thatbutconiferous. Light coniferous taiga - this is the least demanding to the soil and climatic conditions pine and larch forests, the thin crown of which passes the sun's rays to the ground. Pines, having a branched root system, have acquired the ability to use nutrients from poor soil, which is used to fix the soil. This feature allows these plants to grow in areas with permafrost. The shrub layer of light coniferous taiga consists of alder, dwarf birch, polar birch, polar willow, berry bushes. This type of taiga is common in Eastern Siberia. Dark conifer taiga - These are conifers, consisting of numerous species of spruce, fir, cedar. This taiga, unlike light-coniferous, has no undergrowth, as its trees close tightly, and in these forests it is rather dark. The lower tier consists of shrubs (lingonberries, blueberries, blueberries) and thick fern. This type of taiga is common in the European part of Russia and in Western Siberia.
Soils of the taiga zone are podzolic. They contain little humus, but when applied fertilizers can provide a high yield. In the taiga of the Far East - acidic soil.
The fauna of the taiga zone is rich. There are numerous predators that are valuable game animals: otter, marten, sable, mink, weasel. From large - wolves, bears, lynxes, wolverines. In North America, in the taiga zone, buffaloes and deer wapiti used to occur. Now they live only in reserves. Taiga is also rich in rodents, the most typical of which are beavers, muskrats, squirrels, hares, and chipmunks. A great variety of different world of birds.
Temperate mixed forests . These are forests with various tree species: conifer-broad-leaved, small-leaved-pine. This zone is located in the north of North America (on the border of the USA and Canada), and in Eurasia forms a narrow strip between the taiga and the zone of deciduous forests. The zone of mixed forests is also found in Kamchatka and the Far East. In the southern hemisphere, this forest zone covers small areas in southern South America and New Zealand.
The climate of the zone of mixed forests is marine or transitional to continental (towards the center of the continent), the summers are warm, the winters are moderately cold (in the maritime climate with positive temperatures, and in the more continental climate down to -10 ° C). Moisturizing is sufficient. The annual amplitude of temperature fluctuations, as well as annual 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 due to differences in climate. For example, in the Russian Plain, where precipitation falls all year round due to westerly winds coming from the Atlantic, European spruce, oak, elm, fir, beech - coniferous-deciduous forests are common.
The soils in the zone of mixed forests are gray forest and sod-podzolic, and in the Far East brown forest.
The animal world is similar to the animal world of taiga and zones of deciduous forests. Here live elk, sable, bear.
Mixed forests have long been subject to severe logging and losses. They are best preserved in North America and the Far East, and in Europe they are cut down for agricultural land - field and grazing land.
Broad-leaved forests of temperate climate . They occupy the east of North America, Central Europe, and also form the high-altitude zone in the Carpathians, Crimea and the Caucasus. In addition, some centers of deciduous forests are found in the Far East of Russia, in Chile, in New Zealand and in the center of Japan.
The climate is favorable for the growth of deciduous trees with a wide leaf plate. Here, moderately 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 ° С, and in July + 20-24 ° С.
In the forests grow beech, hornbeam, elm, maple, linden, ash. In the zone of deciduous forests of North America there are species that are absent on other continents. These are American oak species. Trees with a powerful sprawling crown, often entwined with climbing plants: grapes or ivy, prevail here. Magnolias are found to the south. For European deciduous forests, the most typical are oak and beech.
The fauna of this natural area is close to the taiga, but there are animals such as black bears, wolves, minks, raccoons, which are not characteristic of the taiga. Many animals of deciduous forests of Eurasia are protected, as the number of individuals is sharply reduced. These include animals such as bison, Ussuri tiger.
Soils under deciduous forests are gray forest or brown forest. This zone is heavily developed by man, the forests on large areas are reduced, and the land is plowed. In its true form, the zone of deciduous forests has been preserved only in areas and reserves that are inconvenient for tillage.
Forest-steppe . This natural zone is located within the temperate climate zone and is a transition from a forest to a steppe, with alternating forest and steppe landscapes. It is distributed in the Northern Hemisphere: in Eurasia from the Danube Lowland to the Altai, then in Mongolia and the Far East; in North America, this zone is located in the north of the Great Plains and in the west of the Central Plains.
Forest-steppes are naturally distributed within the continents between the zones of the forests, which here choose the most wetted areas, and the steppe zone.
The forest-steppe climate is moderately continental: winter is snowy, cold (from -5 ° C to -20 ° C), summer is warm (+ 18 ° C to + 25 ° C). In different longitudinal zones, forest-steppe differs in atmospheric precipitation (from 400 mm to 1000 mm). Humidification is slightly below sufficient, evaporation is very large.
In the forests that alternate the steppe, deciduous (oak) and small-leaved tree species (birch) are more common, less often coniferous. The forest-steppe soils are mainly gray forest, which alternate with black soil. The nature of the forest-steppe zone is greatly changed by human activities. In Europe and North America, the plowed zone reaches 80%. Since in this zone there are fertile soils, wheat, maize, sunflower, sugar beet and other crops are grown here. The fauna of the forest-steppe zone accommodates species characteristic of the forest and steppe zones.
The West Siberian forest-steppe is specific with numerous birch groves-groves (singular number - peg). Sometimes they have an admixture of aspen. The area of individual pegs reaches 20-30 ha. Numerous pegs, alternating with areas of the steppes, create a characteristic landscape of South-Western Siberia.
Steppes . This is a landscape with grassy vegetation type, located in the temperate and partially in the subtropical zone. In Eurasia, the steppe zone extends in the latitudinal direction from the Black Sea to Transbaikalia; in North America, the Cordillera distribute the air flow in such a way that the zone of insufficient moisture and along with it the steppe zone is located from north to south along the eastern edge of this mountainous country. In the southern hemisphere, the steppe zone is located within a subtropical climate, in Australia and Argentina. Atmospheric precipitation (from 250 mm to 450 mm per year) falls irregularly here and is insufficient for tree growth. The winter is cold, the average temperature is below 0 ° С, in some places up to -30 °, and it has little snow. Summer is moderately hot - + 20 ° С, + 24 ° С, often drought. The internal waters in the steppe are poorly developed, the river runoff is small, and often the rivers dry up.
The undisturbed vegetation of the steppe is a dense grass cover, but the undisturbed steppe around the world remained only in reserves: all the steppe are plowed up. Depending on the nature of the vegetation in the steppe zone, three subzones are distinguished. They differ from each other in the prevailing vegetation. it meadow steppes (bluegrass, fire, timothy), cereal and south wormwood .
The soils of the steppe zone — chernozem — have a considerable humus horizon, thanks to which they are very fertile. This is one of the reasons for the strong plowing of the zone.
The fauna of the steppes is rich and diverse, but it has greatly changed under the influence of man. In the 19th century, wild horses, tours, bison, and roes disappeared. Deer are driven back 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. Occasionally there are bustards, strepety, larks and others.
The steppes and partly the forest-steppes of temperate and subtropical zones of North America are called the prairies . Currently, they are almost completely plowed. Some of the American prairies are dry steppes and semi-deserts.
The subtropical steppe in the plains of South America, located mainly in Argentina and Uruguay, is called pampa . In the eastern regions, where precipitation comes from the Atlantic Ocean, there is sufficient moisture, and aridity to the west increases. Most of the territory of the pampa is plowed, but in the west there are still dry steppes with thorny shrubs used as pasture for cattle.
Semi-deserts and deserts of the temperate zone . In the south, steppes turn into semi-deserts, and then into deserts. Semi-deserts and deserts form in a dry climate, where there is a long and hot warm period (+ 20-25 ° С, sometimes up to 50 ° С), strong evaporation, which is 5-7 times higher than the sum of annual precipitation (up to 300 mm in year). Weak surface runoff, poor development of inland waters, a lot of drying out channels, vegetation is not close, sandy soils heat up during the day, but quickly cool down on a cool night, which contributes to physical weathering. Here the land of the wind is very drained. The deserts of the temperate zone differ from the deserts of other geographic 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 Juanhe, and in North America - in the foothills and depressions of the Cordillera. In the southern hemisphere, deserts and semi-deserts of the temperate zone exist only in Argentina, where they are found in torn areas in the inner parts and foothills. Of the plants, here are found steppe kovyli, fescue, wormwood and solyanka, camel thorn, agave, aloe vera. Of the animals - saigas, turtles, many reptiles. Soils here are light brown and brown desert, often saline. In conditions of sharp fluctuations in temperature during the day with little moisture on the surface of the desert a dark crust - desert tan. It is sometimes called protective, since it protects rocks from rapid weathering and destruction.
The main use of semi-deserts is pasture cattle breeding (camels, fine-fleeced sheep). Farming of drought-resistant crops is possible only in oases. Oasis (from the Greek name for several inhabited places in the Libyan desert) is a growing place for woody, shrub and herbaceous vegetation in deserts and semi-deserts, in conditions of more abundant surface and ground moistening compared to neighboring areas and areas. The size of the oases are different: from ten to tens of thousands of kilometers. Oases - population concentration centers, areas of intensive farming on irrigated lands (Nile Valley, Fergana Valley in Central Asia).
Deserts and semi-deserts of the subtropical and tropical belts . These are natural areas located in both hemispheres, on all continents along tropical areas of high atmospheric pressure. Most often, the semi-deserts of the subtropical zone are located in the transitional part from deserts to mountain steppes in the form of a high-altitude belt in the inland parts of the Cordillera and the Andes of America, in western Asia, Australia, and especially widely in Africa. The climate of the deserts and semi-deserts of these climatic zones is hot: the average temperature in summer rises to + 35 ° С, and in the coldest months in winter it does not fall below + 10 ° С. Precipitations fall between 50–200 mm, in semi-deserts up to 300 mm. Sometimes precipitation falls in the form of short showers, and in some areas precipitation may not fall out for several years in a row. With a lack of moisture, the weathering crust is very thin.
Groundwater is very deep and may be partially saline. In such conditions, only plants that can tolerate overheating and dehydration can live. They have a deeply branched root system, small leaves or spines that reduce evaporation from the surface of the leaf. In some plants, the leaves are pubescent or covered with a waxy coating that protects them from sunlight. In the semi-deserts of the subtropical zone, cereals are common, cacti appear. In the tropical belt, the number of cacti increases, agaves grow, sand acacias, and various lichens are common on stones. A characteristic plant for the Namib Desert, located in the tropical belt of South Africa, is an amazing plant of velvigiya, which has a short trunk, from the top of which two leathery leaves extend. Age Velvigii can reach 150 years. The soils are gravelly, gray-brown serozems, they are of little fertile, since the humus layer is thin. The fauna of the desert and semi-desert is rich in reptiles, spiders, scorpions. There are camels, antelopes, rodents are quite widespread. Farming in semi-deserts and deserts of the subtropical and tropical zones is also possible only in oases.
Stiffleaf forests . This natural zone is located within the subtropical belt of the Mediterranean type. They mainly grow in the south of Europe, in the north of Africa, in the southwest and southeast of Australia. Separate fragments of these forests are found in California, in Chile (south of the Atacama Desert). The hardwood forests grow in a mild, moderately warm climate with hot (+ 25 ° C) and dry summers and cool and rainy winters. Average precipitation is 400-600 mm per year with rare and short-lived snow cover. The rivers are mostly rain fed, and the flood occurs during the winter months. Under conditions of a rainy winter, grasses grow rapidly.
The fauna is severely exterminated, but herbivorous and leaf-eating forms, many birds of prey and reptiles are characteristic. In the forests of Australia you can find a koala bear that lives in trees and leads a nocturnal sedentary lifestyle.
The territory of hardwood forests is well developed and largely changed by human activities. Large areas of forests are cut down, and their place was taken by oilseed plantations, orchards and pastures. Many tree species have solid wood, which is used as a building material, and oils, paints, and medicines (eucalyptus) are made from leaves. Large yields of olives, citrus, grapes are removed from the plantations of this zone.
Monsoon forests of the subtropical belt . This natural area is located in the eastern parts of the continents (China, southeastern United States, eastern Australia, southern Brazil). It is located in the most humid conditions in comparison with other zones of the subtropical belt. The climate is characterized by the presence of a dry winter and a humid summer. 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. On the territory of monsoon forests, the inland waters are rich enough; fresh groundwater is not deeply deposited.
Here on the red and yellow soils grow high mixed forests, among which are evergreen and deciduous, shed their leaves for the dry season. The species composition of plants may vary depending on soil conditions. Subtropical pine species, magnoliaceae, camphor laurel, camellias grow in the forests. On the flooded coasts of Florida in the United States and the Mississippi lowland forests of cypress cypress are common.
The zone of monsoon forests of the subtropical belt has been mastered by man for a very long time. Field and grazing lands are located at the site of the reduced forests; here rice, tea, citrus fruits, wheat, corn and industrial crops are grown.
Forests of the tropical and subequatorial belts . They are located along the east of Central America, on the islands of the Caribbean, on the island of Madagascar, in southeast Asia, and in northeast Australia. There are two distinct seasons: dry and wet. Existence of forests in the dry and hot tropical belt is possible only due to precipitation, which brings monsoons in the summer from the oceans. In the subequatorial belt, precipitation comes in summer, when equatorial air masses prevail here. Depending on the degree of moisture among the forests of the tropical and subequatorial belts, there are constantly wet and seasonally wet (or variable-wet) 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, laurel. Often in seasonally wet forests there are areas where teak and sal grow. Very few in the forests of this group of palm trees. In their species diversity of flora and fauna, constantly-moist forests are close to equatorial. There are many palm trees, evergreen oaks, tree ferns. Many lianas and epiphytes from orchids and ferns. The soils located under forests are mainly lateritic. During the dry period (in winter), most deciduous trees do not shed their entire foliage, but some species remain completely bare.
Savannah . This natural zone is located mainly within the subequatorial climate, although it also exists within the tropical and subtropical zones. In the climate of this zone, the change of the wet and dry season of the year is clearly expressed at consistently high temperatures (from + 15 ° С to + 32 ° С). As the distance from the equator increases, the period of the wet season from 8–9 months decreases to 2–3, and the precipitation decreases from 2,000 to 250 mm per year.
For savannah characterized by the predominance of grass cover, among which dominate the high (up to 5 m) grass. Among them, shrubs and solitary trees rarely grow. The grass cover near the boundaries with the equatorial belt is very thick and high, and near the boundaries with semi-deserts it is sparse. A similar pattern is also observed in trees: their frequency increases towards the equator. Among the savanna trees you can find a variety of palm trees, umbrella acacias, tree cacti, eucalyptus, baobabs, storing water.
The 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 located red ferralit soils. Closer to the border of savannas and semi-deserts red-brown soils are located, and even closer to the border, where rains fall for 2-3 months, unproductive soils with a thin layer of humus are formed.
The animal world of savannas is very rich and diverse, as the high grass cover provides animals with food. Elephants, giraffes, hippos, zebras live here, which in turn attract lions, hyenas and other predators. The world of birds in this area is also rich. Nectarian girls live here, ostriches are the largest birds on Earth, the secretary bird that hunts small animals and reptiles. Many in the savannah and termites.
Savannah are widespread in Africa, where they occupy 40% of the mainland, in South America, Australia and India.
The high-grass savannas in South America, on the left bank of the Orinoco River, with thick, mainly grassy grass cover, with individual specimens or groups of trees, are called lianos (from the Spanish. Number of "plain"). The savannas of the Brazilian Plateau, where the region of intensive animal husbandry is located, are called campos .
Today savannas play a very large role in the economic life of a person. Significant areas of this zone are plowed up, grain crops, cotton, peanuts, jute, and sugarcane are grown here. In more arid places developed animal husbandry. Breeds of many trees are used in the household, as their wood does not rot in the water. Human activities often lead to savanna desertification.
Wet Equatorial Forests . This natural zone is located in an equatorial climate and partly subequatorial. These forests are common in the Amazon, Congo, Malacca Peninsula and Sunda Islands, as well as on other, smaller islands.
The climate here is hot and humid. Year-round temperature is + 24-28 ° C. Seasons are not expressed here. Wet equatorial forests are located within the region of low pressure, where as a result of intensive heating upward air flows 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, more precipitation falls (up to 10,000 mm). Precipitations are evenly distributed throughout the year. Such climatic conditions contribute to the development of lush evergreen vegetation, although, strictly speaking, trees change leaves: some are dropped every six months, others after a completely arbitrary period, and the third leaves are replaced in parts. Flowering periods also vary, and even more randomly. The most frequent 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 simultaneously, so that they can pollinate each other. The plants of this zone are little branched.
Trees of humid equatorial forests have discoid roots, large leathery leaves, the brilliant surface of which saves them from excessive evaporation and the scorching rays of the sun, from the blows of rain streams during heavy rainfall. Many leaves end in an elegant thorn. This is a tiny drain. In plants of the lower tier, the leaves, on the contrary, are thin and tender. The upper tier of the equatorial forests form ficuses, palm trees. In South America, ceiba grows in the upper tier, reaching a height of 80 m. Bananas, 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 found, sometimes flowers are formed 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, which stick to the crown and hang down from the branches. They are epiphytes. Flowers of trees in the crown can not be pollinated by the wind, because the air there is almost stationary. Consequently, they are pollinated by insects and small birds, which are lured by a brightly colored halo or a sweet smell. The fruits of 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, animals, the seeds are not digested and, together with the droppings, are far from the parent plant.
In equatorial forests there are a lot of primers. These are primarily creepers. They begin their life on earth in the form of a small bush, and then, tightly wrapping themselves around the stem of a giant tree, climb up. The roots are in the soil, so the plant's food is not due to the giant tree, but sometimes using lianas of these trees for support can lead to their oppression and death. "Rogues" are some ficuses. Their seeds germinate on the bark of a tree, the roots tightly clasp the trunk and branches of this host tree, which begins to die. Its trunk is rotting, but the roots of ficus have become thick and dense and are already able to keep themselves.
Equatorial forests - the birthplace of many valuable plants, such as oil palm, from the fruits of which receive palm oil. Many trees are used to make furniture and are exported in large quantities. This group includes ebony, the wood of which has a black or dark green color. Many plants of equatorial forests produce valuable fruits, seeds, sap, bark, which are used in engineering and medicine.
Equatorial forests of South America are called selva . Selva is located in a periodically flooded area of the Amazon River Basin. Sometimes, describing humid equatorial forests, they use the name gilea sometimes these forests are called jungle , although, strictly speaking, jungles are called forest thickets of South and Southeast Asia, located within the sub-equatorial and tropical climate.
Plan
1. Arctic deserts
2. Tundra
3. Forest zone
a) taiga
b) mixed forests
c) deciduous forests
4. Steppes
5. Desert
6. Subtropics
Arctic deserts
The Arctic is a zone of islands lying near the North Pole. There is a long, cold winter, a short cold summer, and therefore vegetation is scarce - mosses and lichens.
In the Arctic, the sun does not set for several months - the polar day continues. A few months round the clock light, but not warm. The temperature is only a few degrees above 0. In winter, the polar night comes. Dark dark and very cold. The darkness is lit: the moon, the stars and the Northern Lights.
This is a very cold zone. But this does not mean that there are no animals and plants on it.
The Arctic is the realm of the polar bear. Lack of land does not bother him, the main habitat - the ice of the Arctic Ocean. The polar bear feeds on fish, hunts for the seal, seals, baby walruses.
Numerous pinnipeds live in the Arctic - seals, seals, walruses, and elephant seals. The elongated streamlined shape of the body helps them to move in water with great speed.
On the coastal cliffs find shelter and nest in the summer, numerous birds arranging "bird markets" on the rocks - geese, gulls, eider, terns, sandpipers. In the cracks of the rocks, where a small amount of soil accumulates, in thawed areas of glacial deposits - moraines, mosses, lichens, some algae and even cereals and flowering plants settle near the snowfields. Among them, bluegrass, cotton grass, polar poppy, sedge, dwarf willow, birch. During the cold polar summer, they manage to bloom and even give fruit.
Unfortunately, due to the development of the Arctic by man, complex environmental problems have arisen here: pollution of the northern seas; destruction of commercial fish species; hunting for polar bears and seals. Now hunting for rare animals of the Arctic is prohibited. Some bird markets were taken under protection. Fishing is limited. Created reserves, such as the reserve "Wrangel Island"
Tundra
Harsh tundra climate - winter lasts longer than the school year at school. Fierce winds are blowing all year round, and a snowstorm rages in winter. Even in summer, the earth practically does not thaw (only by 10–25 cm), and the permafrost remains below.Birches creep near the surface, hiding from wind and cold in mosses and lichens.
White grouse, white owl, gyrfalcon, reindeer, wolves live in the tundra; geese and cranes arrive in the summer.
The main occupation of the tundra population is reindeer herding. The mining of oil and gas is still underway.
There are environmental problems in the tundra:
soil disturbance from tractor tracks, all-terrain vehicles — plants die.
the area is polluted by oil during its production.
illegal hunting - poaching.
reindeer pastures are trampled, because deer do not always move to other places.
Forest zone
Taiga - coniferous forest, it occupies most of the zone.
Mixed forest- along with conifers, birch, aspen, and alder grow in it. Winter in this forest is softer. Leafy trees have medium-sized leaves that they shed for the winter.
Broadleaf forest- replaces oak, linden, maple, ash, elm. These are heat-loving plants, so they have large leaves, shed their leaves for the winter, multiply by seeds.
Human fault is causing environmental problems. If before the forest was cut down as needed, now everything that is possible is cut down. Excessive hunting led to the complete or almost complete extinction of some species of animals.
Steppes
The steppes stretch in a narrow continuous strip in the south of Russia from the western borders to the Altai. Further to the east, steppe areas have a focal distribution.The average January temperature in the sun is -2 ° С, and in the east -20 ° С and lower. Summer in the steppe is sunny and hot. The average July temperature is 22-23 ° C. In the west, zones often thaw, therefore the snow cover there is thin and very unstable. The predominant soil of the steppes is black soil.
Natural plant communities are represented mainly by perennial, drought-resistant and frost-resistant grasses with a strong root system. First of all, these are cereals: kovyli, fescue, grazing grass, serpent, tonkonog, bluegrass. In addition to cereals, numerous representatives of forbs: astragalus, sage, carnation - and bulbous perennials, such as tulips.
In the European steppes, the basis is made up of narrow-leaved cereals: feather grass, fescue, bluegrass, fescue, tonkonog, etc.
In the more arid southern regions, in addition to cereals, wormwood, infant, and silverweed are common. In the spring a lot of tulips. In the Asian part of the country tansy and cereals predominate.
Hoofed animals are adapted for long movements in the vast expanses of the steppes. Due to the low thickness of the snow cover, vegetable food is also available in winter. An important role in nutrition is played by the bulbs, tubers, rhizomes. For many animals, plants are also the main source of moisture. Typical representatives of ungulates in the steppes are tours, antelopes, tarpany. However, the majority of these species as a result of economic activity of people were exterminated or pushed back to the south. In some areas, saigas widespread in the past have survived.
Of the rodents, the most common is the gopher, vole, jerboa, etc. The ferret, badger, weasel, and fox also live in the steppe.
Of the birds typical for the steppes are the bustard, the little bastard, the gray partridge, the steppe eagle, the buzzard, the kestrel. However, these birds are now rare.
Reptiles are significantly larger than in the forest zone. Among them, we distinguish the steppe viper, snake, common snake, sand lizard, moth.
The richness of the steppes - fertile soil. This natural area is almost completely mastered by man and the natural steppe landscapes are preserved only in reserves. In connection with insufficient precipitation and frequent droughts in the steppe zone, irrigation systems were built.
Steppes - a zone of developed animal husbandry. Cattle, horses, and poultry are raised here. Various industries are developed: metallurgy, mechanical engineering, food, chemical, textile.
Desert
In Russia, the desert occupies a small area - along the shores of the Red Sea. Huge deserts are spread in other states: Kazakhstan, Turkmenistan, Uzbekistan. In the desert is very hot.Typical soils of semi-desert and desert zones are chestnut.
Most of the animals in the desert are not large, because they have nowhere to hide from predators. The most common are reptiles - lizards, snakes, turtles.
Birds - bustard, little bastard, larks.
Among the largest mammals, we note camel, saiga; meet korsak, wolf.
Camel - he has a lot of adaptations to live in the desert. Long, thick eyelashes protect your eyes from sand. Both toes on each leg are connected by a callosal pad. Thanks to her, he does not fall into the sand.
The traditional occupation of the population is cattle breeding: sheep, camels, cattle are bred. As a result of overgrazing of cattle, the area of loose sands spread out increases. One of the measures to combat the onset of the desert is phytomelioration — a set of measures to cultivate and maintain natural vegetation.
People built canals to irrigate the land. It's good. But excessive irrigation led to the fact that there was a lot of salt in the soils. Poaching is also a problem.
The culprit of the problems - man. Now people have a difficult task - to correct their mistakes.
Subtropics
This zone, which occupies the Black Sea coast of the Caucasus, is characterized by the smallest length and area in Russia.Fertile red-earth and yellow-earth soils are widespread.
Subtropical vegetation is rich and diverse. The flora is represented by evergreen hard-leaved trees and shrubs, among which we call boxwood, laurel, laurel cherry. Distributed forests of oak, beech, hornbeam, maple. Thickets of trees are intertwined with liana, ivy, wild grapes. There are bamboo, palm trees, cypress, eucalyptus.
Of the representatives of the animal world we note chamois, deer, wild boar, bear, wood and stone marten, Caucasian black grouse.
The abundance of heat and moisture allows you to grow here such subtropical crops as tea, tangerines, lemons. Significant areas are occupied by vineyards and tobacco plantations.
Favorable climatic conditions, proximity to the sea and the mountains make this area a large recreational area of our country. There are numerous camp sites, holiday homes, motels.
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