Change of natural areas. §eleven
Natural complex (landscape), natural zone, latitudinal and altitudinal zones
Natural complex- a territory that has a certain unity of nature, due to the commonality of its origin and history of development, originality geographical location, operating within its boundaries modern processes. In a natural complex, all components are connected to each other. Natural complexes vary in size. The largest natural complex (NC) is the geographical envelope. Continents and oceans, natural areas- also a PC. A small ravine or lake is also a natural complex. The formation of natural complexes occurs over a long period of time.
Geographical zone– the largest territorial unit of latitude-zonal division geographic envelope, characterized by common thermal conditions. Latitudinal location geographical zones determined mainly by changes in the quantity solar radiation from the equator to the poles of the Earth. Humidification can be different within geographic zones, which makes it possible to distinguish within each zone geographical zones and subzones.
Natural areas. At the core geographical zonation lies in climate change, and above all differences in solar heat input. The largest territorial units of zonal division of the geographical envelope are geographical zones.
Natural areas– natural complexes occupying large areas, characterized by the dominance of one zonal type of landscape. They are formed mainly under the influence of climate - the distribution of heat and moisture, their ratio. Each natural zone has its own type of soil, vegetation and animal life.
Appearance A natural area is determined by the type of vegetation cover. But the nature of vegetation depends on climatic conditions - thermal regime, moisture, lighting.
As a rule, natural zones are extended in the form of wide stripes from west to east. There are no clear boundaries between them; the zones gradually transform into one another. The latitudinal location of natural zones is disrupted by the uneven distribution of land and ocean, relief, and distance from the ocean. For example, in temperate latitudes In North America, natural zones are located in the meridional direction, which is due to the influence of the Cordilleras, which prevent the passage of humid winds from Pacific Ocean inland. Eurasia contains almost all the zones of the Northern Hemisphere, but their width is not the same. For example, zone mixed forests gradually narrows from west to east as it moves away from the ocean and the climate becomes more continental. In the mountains, natural areas change with altitude - altitudinal zone . Altitudinal zone caused by climate change with uplift. Kit altitude zones in the mountains depends on the geographical position of the mountains themselves, which determines the nature of the lower zone, and the height of the mountains, which determines the nature of the uppermost altitude zone for these mountains. The higher the mountains and the closer they are to the equator, the more altitude zones they have.
The location of altitudinal belts is also influenced by the direction of the ridges relative to the sides of the horizon and the prevailing winds. Thus, the southern and northern slopes of the mountains may differ in the number of altitude zones. As a rule, there are more of them on the southern slopes than on the northern ones. On slopes exposed to wet winds, the nature of the vegetation will be different from the vegetation on the opposite slope.
The sequence of changes in altitudinal zones in the mountains practically coincides with the sequence of changes in natural zones on the plains. But in the mountains, belts change faster. There are natural complexes that are characteristic only of mountains, for example, subalpine and alpine meadows.
Natural land areas. Evergreen tropical and equatorial forests located in equatorial and tropical zones South America, Africa and the islands of Eurasia. The climate is humid and hot. The air temperature is constantly high. Red-yellow ferrallitic soils are formed, rich in iron and aluminum oxides, but poor in nutrients. Dense evergreen forests - source large quantity plant litter. But organic matter entering the soil does not have time to accumulate. They are absorbed by numerous plants and washed away daily precipitation into the lower soil horizons. For equatorial forests multi-tiered is typical. The vegetation is represented mainly by woody forms, forming multi-tiered communities. Characteristically high species diversity, the presence of epiphytes (ferns, orchids), lianas. The plants have hard, leathery leaves with devices that remove excess moisture (drips). The fauna is represented by a huge variety of forms - consumers of rotting wood and leaf litter, as well as species living in the crowns of trees.
Savannas and woodlands– natural areas with characteristic herbaceous vegetation (mainly cereals) in combination with individual trees or groups of trees and bushes. They are located north and south of the equatorial forest zones southern continents in tropical zones. The climate is characterized by the presence of more or less long dry period And high temperatures air throughout the year. In savannas, red ferrallitic or red-brown soils are formed, which are richer in humus than in equatorial forests. Although in the wet season nutrients are washed out of the soil, and humus accumulates during the dry period. Predominantly herbaceous vegetation with separate groups trees. Umbrella crowns are characteristic, life forms allowing plants to store moisture (bottle-shaped trunks, succulents) and protect themselves from overheating (pubescence and waxy coating on the leaves, arrangement of the leaves with the edge towards sun rays). The animal world is characterized by an abundance of herbivores, mainly ungulates, large predators, animals that process plant litter (termites). With distance from the equator in the Northern and Southern Hemispheres The duration of the dry period in savannas increases, the vegetation becomes more and more sparse.
Deserts and semi-deserts located in tropical, subtropical and temperate climatic zones. The desert climate is characterized by extremely low rainfall throughout the year. The daily amplitudes of air temperature are large. By temperature conditions they vary quite a lot: from hot tropical deserts to deserts of the temperate climate zone. All deserts are characterized by development desert soils, poor organic substances, but rich in mineral salts. Irrigation allows them to be used for agriculture.
Soil salinization is widespread. The vegetation is sparse and has specific adaptations to arid climate: leaves turned into thorns, root system greatly exceeds the above-ground part; many plants are able to grow on saline soils, bringing salt to the surface of the leaves in the form of plaque. There is a great variety of succulents. Vegetation is adapted to either “catch” moisture from the air, or to reduce evaporation, or both. The fauna is represented by forms capable of for a long time do without water (store water in the form of fat deposits), travel long distances, survive the heat by going into holes or hibernating. Many animals lead night look life.
Hard-leaved evergreen forests and shrubs located in subtropical zones under conditions Mediterranean climate with dry, hot summers and damp, mild winters. Brown and red-brown soils are formed.
The vegetation cover is represented by coniferous and evergreen forms with leathery leaves covered with a waxy coating, pubescence, usually with a high content essential oils. This is how plants adapt to dry, hot summers. The fauna has been greatly exterminated; but herbivorous and leaf-eating forms, many reptiles, and birds of prey are characteristic.
Steppes and forest-steppes– natural complexes characteristic of temperate zones. Here, in a cold climate, it is often snowy winter and warm, dry summers, the most fertile soils are formed - chernozems. The vegetation is predominantly herbaceous, in typical steppes, prairies and pampas - cereal, in dry varieties - wormwood. Almost everywhere, natural vegetation has been replaced by agricultural crops. The fauna is represented by herbivorous forms, among which ungulates have been greatly exterminated; mainly rodents and reptiles, which are characterized by a long period of winter dormancy, and birds of prey have been preserved.
Broadleaf and mixed forests grow in temperate zones in climate conditions with sufficient moisture and periods with low, sometimes negative temperatures. The soils are fertile, brown forest (under broad-leaved forests) and gray forest (under mixed forests). Forests, as a rule, are formed by 2-3 species of trees with a shrub layer and a well-developed herbaceous cover. The fauna is diverse, clearly divided into tiers, represented by forest ungulates, predators, rodents, and insectivorous birds.
Taiga distributed in the temperate latitudes of the Northern Hemisphere in a wide band in a climate with short warm summer, long and harsh winter, sufficient quantity precipitation and normal, sometimes excessive moisture. In the taiga zone, under conditions of abundant moisture and relatively cool summer intensive washing of the soil layer occurs, little humus is formed. Under its thin layer, as a result of washing the soil, a whitish layer is formed, which appearance looks like ash. Therefore, such soils are called podzolic. Vegetation is represented various types coniferous forests in combination with small-leaved ones.
The tiered structure is well developed, which is also characteristic of the animal world.
Tundra and forest-tundra common in subpolar and polar climate zones. The climate is harsh, with a short and cold growing season and long and harsh winters. At small quantity precipitation develops excessive moisture. The soils are peat-gley, with a layer underneath permafrost. The vegetation cover is represented mainly by grass-lichen communities, with shrubs and dwarf trees. The fauna is unique: large ungulates and predators are common, nomadic and migratory forms are widely represented, especially migratory birds which spend only the nesting period in the tundra. There are practically no burrowing animals, and few grain-eaters.
Polar deserts common on islands at high latitudes. The climate of these places is extremely harsh, most winter dominates the year and polar night. The vegetation is sparse, represented by communities of mosses and crustose lichens. The fauna is associated with the ocean; there is no permanent population on land.
Altitudinal areas are located in a variety of climatic zones and are characterized by a corresponding set of altitudinal zones.
Their number depends on latitude (in equatorial and tropical regions it is greater and on altitude mountain range) the higher, the larger the set of belts.
The complex picture of the natural zones of North America is determined by the peculiarities of the geographical location of the continent. Changes in natural conditions occur in two directions - from north to south and from oceanic margins to inland areas mainland. Therefore, in the north of the continent the zones are elongated in the latitudinal direction, and in the central part they have a location close to the meridional one. The natural zones of the temperate zone are the most diverse in North America. This is due primarily to the significant size of this belt (more than ""/3 of the continental area) and to the large climatic differences in its different parts. The natural zone of Arctic deserts is formed within arctic belt. Glaciers are widespread here. Only in summer on the ledges of the indigenous rocks, in depressions and cracks there are plants: mosses, lichens, some types of grasses and shrubs. Under this vegetation, scanty and primitive arctic soils, containing almost no nutritional minerals and organic substances. With harsh natural conditions associated poverty of the animal world. There are some here large mammals. Among them is the musk ox or musk ox, a large and hardy animal with thick, trailing hair and a flattened muzzle. It is preserved in Greenland and the Canadian Arctic Archipelago. Coastal Arctic regions are visited by polar bears, wolves, and arctic foxes. The waters of the adjacent seas are inhabited by seals, walruses, beluga whales, and bowhead whales. Rocky islands are characterized by accumulations of various seabirds- bird markets. Natural tundra zone. The north of the continent in the subarctic zone is occupied by the natural tundra zone. Main feature This zone is the absence of trees. In the north of the tundra, mosses and lichens are common. They form a continuous spongy and moisture-rich carpet. There are grasses (sedge, cotton grass) and polar flowers - forget-me-nots, polar poppies, dandelions. To the south, low-growing shrubs appear: dwarf birch and willow (usually 30 - 70 cm tall), wild rosemary, heather, berry bushes (blueberries, blueberries). Wide use received permafrost. Waterlogged tundra-gley and swamp soils are formed. The fauna in the tundra is richer than in the Arctic deserts. Meet here reindeer(it is not domesticated and is an important hunting object for Eskimos and Indians), polar bear, polar Wolf, arctic fox, arctic hare, lemming (small rodent). The most common birds are the ptarmigan and the polar owl of prey; they arrive in summer waterfowl(geese, ducks, waders). A lot of bird markets(eiders, guillemots, hatchets, etc.) The natural forest-tundra zone stretches to the south of the tundra in a strip up to 500 km wide. Along the river valleys it appears here woody vegetation from coniferous species. Underneath it, gley- podzolic soils. In the animal world, as well as in the plant world, there is a mixture of tundra and forest species. Natural taiga zone. The taiga extends south of the forest-tundra. Vegetation is represented coniferous forests from black and white spruce, balsam fir, American larch, thuja. In drier areas, forests of white (or Weymouth) pine, Banks (or lodgepole) pine, and red pine grow. In the taiga zone, podzolic soils are typical, and in low-lying areas swamp soils are found in large areas. Taiga has a diverse fauna. There are many large ungulates here. These are wapiti deer, American elk with huge palm-shaped antlers, forest deer, and in the mountain taiga - bighorn goat and bighorn sheep. Many predators - marten, wolf, Canadian lynx, ermine, wolverine, fox. There are brown and black American bears, as well as puma (or cougar), gray and red squirrels, and chipmunks.
At the core geographical zonation lies in climate change, and above all differences in solar heat input. The largest territorial units of the zonal division of the geographical envelope are geographical zones.
Natural areas – natural complexes occupying large areas, characterized by the dominance of one zonal type of landscape. They are formed mainly under the influence of climate - the distribution of heat and moisture, their ratio. Each natural zone has its own type of soil, vegetation and animal life.
The appearance of the natural area is determined type of vegetation cover . But the nature of the vegetation depends on climatic conditions - thermal conditions, moisture, lighting.
As a rule, natural zones are extended in the form of wide stripes from west to east. There are no clear boundaries between them; the zones gradually transform into one another. The latitudinal location of natural zones is disrupted by the uneven distribution of land and ocean, relief, and distance from the ocean.
For example, in the temperate latitudes of North America, natural zones are located in the meridional direction, which is associated with the influence of the Cordilleras, which prevent the passage of moist winds from the Pacific Ocean into the interior of the continent. Eurasia contains almost all the zones of the Northern Hemisphere, but their width is not the same. For example, the zone of mixed forests gradually narrows from west to east as it moves away from the ocean and the climate becomes more continental. In the mountains, natural areas change with altitude - high-risezonality . Altitudinal zonation is due to climate change with upward movement. The set of altitudinal zones in the mountains depends on the geographical position of the mountains themselves, which determines the nature of the lower zone, and the height of the mountains, which determines the nature of the uppermost altitudinal zone for these mountains. The higher the mountains and the closer they are to the equator, the more altitude zones they have.
The location of altitudinal belts is also influenced by the direction of the ridges relative to the sides of the horizon and the prevailing winds. Thus, the southern and northern slopes of the mountains may differ in the number of altitude zones. As a rule, there are more of them on the southern slopes than on the northern ones. On slopes exposed to wet winds, the nature of the vegetation will be different from the vegetation on the opposite slope.
The sequence of changes in altitudinal zones in the mountains practically coincides with the sequence of changes in natural zones on the plains. But in the mountains, belts change faster. There are natural complexes that are characteristic only of mountains, for example, subalpine and alpine meadows.
Natural land areas
Evergreen tropical and equatorial forests
Evergreen tropical and equatorial forests are located in the equatorial and tropical zones of South America, Africa and the islands of Eurasia. The climate is humid and hot. The air temperature is constantly high. Red-yellow ferrallitic soils are formed, rich in iron and aluminum oxides, but poor in nutrients. Dense evergreen forests are a source of large amounts of plant litter. But organic matter entering the soil does not have time to accumulate. They are absorbed by numerous plants and washed out by daily precipitation into the lower soil horizons. Equatorial forests are characterized by many layers.
The vegetation is represented mainly by woody forms, forming multi-tiered communities. Characterized by high species diversity, the presence of epiphytes (ferns, orchids), and lianas. The plants have hard, leathery leaves with devices that remove excess moisture (drips). The fauna is represented by a huge variety of forms - consumers of rotting wood and leaf litter, as well as species living in the crowns of trees.
Savannas and woodlands
Natural areas with characteristic herbaceous vegetation (mainly cereals) in combination with individual trees or groups of trees and bushes. They are located north and south of the equatorial forest zones of the southern continents in the tropical zones. The climate is characterized by more or less long dry periods and high air temperatures throughout the year. In savannas, red ferrallitic or red-brown soils are formed, which are richer in humus than in equatorial forests. Although nutrients are washed out of the soil during the wet season, humus accumulates during the dry season.
The vegetation is dominated by herbaceous vegetation with isolated groups of trees. Umbrella crowns are characteristic, life forms that allow plants to store moisture (bottle-shaped trunks, succulents) and protect themselves from overheating (pubescence and waxy coating on the leaves, the arrangement of the leaves with their edges facing the sun's rays). The animal world is characterized by an abundance of herbivores, mainly ungulates, large predators, and animals that process plant litter (termites). With distance from the equator in the Northern and Southern Hemispheres, the duration of the dry period in savannas increases, and the vegetation becomes more and more sparse.
Deserts and semi-deserts
Deserts and semi-deserts are located in tropical, subtropical and temperate climate zones. The desert climate is characterized by extremely low rainfall throughout the year.
The daily amplitudes of air temperature are large. They vary quite a lot in temperature: from hot tropical deserts to temperate deserts. All deserts are characterized by the development of desert soils, poor in organic matter, but rich in mineral salts. Irrigation allows them to be used for agriculture.
Soil salinization is widespread. The vegetation is sparse and has specific adaptations to the arid climate: the leaves are turned into thorns, the root system greatly exceeds the above-ground part, many plants are able to grow on saline soils, bringing salt to the surface of the leaves in the form of plaque. There is a great variety of succulents. Vegetation is adapted to either “catch” moisture from the air, or to reduce evaporation, or both. The fauna is represented by forms that can do without water for a long time (store water in the form of fat deposits), travel long distances, and survive the heat by going into holes or hibernating.
Many animals are nocturnal.
Hard-leaved evergreen forests and shrubs
Natural zones are located in subtropical zones in a Mediterranean climate with dry, hot summers and wet, mild winters. Brown and red-brown soils are formed.
The plant cover is represented by coniferous and evergreen forms with leathery leaves covered with a waxy coating, pubescence, usually with a high content of essential oils. This is how plants adapt to dry, hot summers. The fauna has been greatly exterminated; but herbivorous and leaf-eating forms, many reptiles, and birds of prey are characteristic.
Steppes and forest-steppes
Natural complexes characteristic of temperate zones. Here, in a climate with cold, often snowy winters and warm, dry summers, the most fertile soils are formed - chernozems. The vegetation is predominantly herbaceous, in typical steppes, prairies and pampas - cereal, in dry varieties - wormwood. Almost everywhere, natural vegetation has been replaced by agricultural crops. The fauna is represented by herbivorous forms, among which ungulates have been greatly exterminated; mainly rodents and reptiles, which are characterized by a long period of winter dormancy, and birds of prey have been preserved.
Broadleaf and mixed forests
Broad-leaved and mixed forests grow in temperate zones in climate conditions with sufficient moisture and periods of low, sometimes negative temperatures. The soils are fertile, brown forest (under broad-leaved forests) and gray forest (under mixed forests). Forests, as a rule, are formed by 2-3 species of trees with a shrub layer and a well-developed herbaceous cover. The fauna is diverse, clearly divided into tiers, represented by forest ungulates, predators, rodents, and insectivorous birds.
Taiga
Taiga is widespread in the temperate latitudes of the Northern Hemisphere in a wide band in a climate with short warm summers, long and harsh winters, sufficient precipitation and normal, sometimes excessive moisture.
In the taiga zone, under conditions of abundant moisture and relatively cool summers, intensive washing of the soil layer occurs, and little humus is formed. Under its thin layer, as a result of washing the soil, a whitish layer is formed, which in appearance is similar to ash. Therefore, such soils are called podzolic. The vegetation is represented by various types of coniferous forests in combination with small-leaved trees.
The tiered structure is well developed, which is also characteristic of the animal world.
Tundra and forest-tundra
Distributed in subpolar and polar climate zones. The climate is harsh, with a short and cold growing season and long and harsh winters. With little precipitation, excess moisture develops. The soils are peat-gley, with a layer of permafrost underneath. The vegetation cover is represented mainly by grass-lichen communities, with shrubs and dwarf trees. The fauna is unique: large ungulates and predators are common, nomadic and migratory forms are widely represented, especially migratory birds that spend only the nesting period in the tundra. There are practically no burrowing animals, and few grain-eaters.
The natural zones of North America, like those of other continents, are subject to the law of geographic zonation. However, their placement on the continent has its own characteristics. As we move deeper into the continent, natural zones acquire a meridional extension. The reasons for this are the features of the relief, as well as the ratio of heat and moisture on the mainland, which change noticeably not only from north to south, but also from west to east.
The Arctic desert zone occupies almost all of Greenland and the Canadian Arctic Archipelago. Vegetation and animal world are extremely poor here, which is explained by the harsh climatic conditions. In ice-free rocky areas, only patches of mosses and lichens can be seen. The life of most animals is connected with the ocean. On land there are small rodents - lemmings, which are the main food for predators such as the wolf and the arctic fox.
The tundra zone is located in the far north of the mainland (translated from Finnish, “tundra” means “treeless”). There is a little more heat here than in the Arctic deserts, but still not enough. Excessive moisture led to swampy areas. Mosses and lichens grow on tundra-bog soils, forming an almost continuous cover. There are sedges and dwarf willows, birches, and alders. The height of these plants often does not exceed 5 cm. Such vegetation is food for caribou (reindeer) and musk ox.
The musk ox resembles both a bull and a ram at the same time. Its body length is about 2.5 m, height is almost 1.5 m, and weight is more than 300 kg. The curved horns reach a length of 70 cm. The body of the animal is covered with thick and long hair black-brown color. Musk oxen are protected. They are listed in the Red Book.
Many birds nest on the coasts in summer, and seals and walruses live in the waters.
As you move south, the tundra is replaced by forest-tundra - transition zone, in which areas of tundra and forest alternate. In addition to the tundra grass cover, it is characterized by thickets of willow and alder shrubs; trees such as spruce and larch appear along the river valleys. Due to the cooling effect of the Arctic Ocean southern border tundra and forest-tundra falls south of the 60th parallel, and the boundary of permafrost - the 56th parallel.
To the south, the forest-tundra turns into the taiga zone, or coniferous forests. Winters here are long and harsh, and summers are warm but short. Due to low evaporation, there is excess moisture: the amount of precipitation exceeds evaporation.
Coniferous forests grow on podzolic and frozen-taiga soils, which have little humus. Permafrost does not allow tree roots to spread deep, so they grow in breadth and are located near the surface of the earth. Black and white spruce, balsam fir, several species of pine and larch grow in the American taiga. The taiga on the Pacific coast has special character. Here the strip of coniferous forests descends to the latitude of Crimea. In conditions of unusually warm and humid climate grow relict forests of such coniferous trees, like thuja and douglasia.
The giant thuja reaches a height of 60–80 m. The diameter of the trunk of this tree is more than 4 m, and the age of individual specimens exceeds 800 years. Douglasia grows on average to 50–80 m, and some of its specimens reach a height of 125 m. This tree lives for about 1000 years. The wood of thuja and douglasia does not rot.
In the taiga of North America there are Brown bear and grizzly bear, wolves, lynxes, foxes, elk, hares. Raccoons and muskrats live near bodies of water.
The muskrat, or musk rat, is a small aquatic rodent. Its thick, silky fur is beautiful and durable. From North America, the muskrat was spread throughout the world, and it became valuable object fur trade.
The transition zone from taiga to deciduous forests is the zone of mixed forests. She takes eastern part mainland. The zone differs from the taiga in a large amount of heat and moisture. Along with conifers, there are numerous representatives of deciduous species: oak, beech, linden, aspen, birch, and hazel.
There are many types of maple in Canadian forests: sugar, red, silver. Thanks to the colorful leaves, maples give forests a special charm. Not by chance Maple Leaf is a symbol of Canada and has taken pride of place on national flag of this country.
Mixed forests grow on gray-brown and soddy-podzolic soils. They are more fertile than the soils of the tundra and taiga. This caused deforestation and the use of vacated lands for arable land. Square forest areas now does not exceed one third of the former spaces.
Broadleaf forests grow primarily in the Appalachian Mountains. It is typical for them to be extremely big variety tree species. There are several dozen species of oak trees alone. In addition to them, beech, chestnut, linden, maples, wild apple trees, pears, etc. grow here on brown forest soils. In the extreme south, a relict tulip tree appears, which reaches a height of 60 m. In spring, it is covered with flowers similar to tulips.
The fauna of this zone is characterized by deer, baribal bear, porcupine, opossum - the only kind marsupials on the mainland. But the fauna of the zone is very depleted of humans.
The forest-steppe zone stretches across the Great Plains of North America in a meridional strip. Its more humid eastern part, where about 1000 mm of precipitation falls per year, is called prairie. The prairies were once distinguished by unusually lush and varied grass cover. Its height and thickness allowed the rider to hide. Millions of herds of bison grazed here, flocks of birds were countless, and rodents were numerous.
Flatness of the territory, mild climate and black soils have resulted in the prairies being almost completely cultivated. Now there are fields of wheat and corn, and bison can only be seen in nature reserves.
The steppe zone occupies large areas in the center of the continent, on the Great Plains. The amount of heat here is great, but the humidity is not enough. Under such conditions, relatively sparse short-grass vegetation forms on chestnut soils.
The fauna of steppes and forest-steppes is relatively sparse. There are a lot of rodents - hamsters, gophers, voles and others. They are being hunted by a coyote. Dangerous reptiles - the common viper, rattlesnake. Many steppe birds.
The semi-desert and desert zone covers the interior plateaus of the Cordillera. It does not form a continuous strip and has a mosaic appearance. The main plant here is the black wormwood subshrub. It grows on gray-brown soils and forms wormwood deserts alternating with saline deserts.
Conclusions:
Natural areas in the Arctic and subarctic zones extend in the latitudinal direction.
The most widespread natural zones on the mainland are the temperate zone.
Natural zones of steppes, prairies, mixed and broad-leaved forests are elongated in the meridional direction.
Read in the section
North of 47° N. w. vegetation zones extend from east to west and from northeast to southwest, south of 47° N. w. - mainly in the meridional direction. In the northern parts, sparse vegetation is widespread, consisting mainly of crustose lichens, mosses and a few species of higher vascular plants that do not form a closed cover. Southern part archipelago and wide strip occupies the Arctic coast of the mainland. Characteristic animals tundra zone: reindeer (caribou), polar bear, arctic fox, lemming, mountain hare, snowy owl, ptarmigan. The musk ox is found only in the north of the Canadian Arctic Archipelago, in Greenland. In the northern part of this zone, moss-lichen formations predominate, in the south - shrub formations.
U upper limit forests (800-2000 m) give way to mountain taiga fir-spruce forests, and higher up - mountain tundra. Mixed forests are located in the Great Lakes and... The broadleaf forest subzone is located in the middle and southern Appalachians and the eastern Central. The antiquity of the flora of the area has determined the large species diversity of forests formed by dozens of species of oak, chestnuts, beeches, hickories, relict tulip trees and many others. On the slopes of the Appalachians, approximately above 700-1000 m, mixed and coniferous forests appear on podzolic, mixed and broad-leaved fauna forests, including a number of original species (for example, Virginia deer, skunk, gray fox, red lynx, gray squirrel, star-nosed mole, among birds - fork-tailed harrier, wild turkey), suffered greatly. Hamsters, shrews, and woodchucks are more common. In the subtropics, forests are represented by two zones: evergreen mixed forests in the east and evergreen coniferous forests in the west. The former are common in the eastern foothills of the southern half of the Appalachians and in the Coastal Lowlands. On the surface of the sea terraces and plateaus, the tree stand is formed by evergreen oaks, elms, magnolias and numerous types of pine intertwined with vines, forests of oaks, magnolias, yews, and cypress. The inland regions of North America are occupied by, and. Steppes are common in the Great Plains, Columbia Plateau, and California Valley.
In the east of the Great Plains in the United States, feather grass and wheatgrass steppes are found; in the remaining parts, dry low-grass steppes of gram grass, bison grass, wheatgrass, seline grass, etc. predominate. Animals of the steppes and forest-steppes are severely exterminated: bison (preserved only in nature reserves), pronghorn antelope , mazam deer (preserved in the mountains), coyote, prairie fox; much more numerous are rodents (gophers, prairie dogs), steppe ferrets, badger, sac rat and birds (ground owl, meadow grouse, etc.). On the desert-steppe plateaus there are numerous reptiles, including poisonous ones - the rattlesnake and the poisonous lizard; Phrynosoma lizard, steppe boa and some others.
In the southern Great Plains, dry steppe gives way to subtropical mesquite. The territories of the Central and Great Plains are intensively used in. Deserts and semi-deserts occupy Big Pool, the eastern part of the Colorado Plateau and the territories adjacent to the Gulf of Mexico in the northwest. Semi-deserts with psammophilous grass-wormwood on brown soils are located at the eastern foot Rocky Mountains USA. In the rest of the territory, small areas of semi-deserts and deserts alternate depending on conditions and moisture.
North of 37° N. w. vegetation cover They form subshrubs - wormwood, quinoa, lard tree and solyanka; to the south - shrubs (creosote bush, ocatilla) and succulents (cacti, yucca, etc.). Central America and West have tropical vegetation. In the wettest areas (mainly at the foot of the windward slopes of the mountains) there are moist evergreen forests complex composition from giant trees with an abundance of lianas and epiphytes, bamboos, which are replaced with height by variablely moist deciduous ones (beeches, lindens, oaks, etc.) tropical forests and mountain subtropical evergreen forests and bushes. Representatives of tropical fauna - alligator, snapping turtles, ibises, flamingos, pelicans, hummingbirds (one species reaches Alaska), Carolina parrot. On the leeward slopes there are tropical savannas, including dry, thorny, low-growing forests, mainly from representatives of the legume family. Along the coasts there are mangrove forests.
Vegetation and soil cover North America has been heavily modified by humans, especially in the United States. The natural vegetation of the prairies was almost completely destroyed, the forest area was significantly reduced, broadleaf forests preserved only on the mountain slopes and have a very depleted composition. Due to deforestation and fires, the area occupied by temperate and subtropical zones and coniferous forests of the Cordilleran West.