Unlike North America, where changes in vegetation cover depend largely on changes in temperature conditions, in South America, with its high temperatures, the nature of vegetation depends mainly on the degree of moisture. A large amount of solar heat allows plants of the southern continent to vegetate throughout the year almost everywhere. As in Africa, the main factor determining the duration of the growing season is the degree of moisture. The latter in the hot zone decreases not from the oceans into the interior of the continent, but from the equator to the tropics, and only in the subtropics do differences between the oceanic and inland territories sharply appear. In this regard, the main forest areas in South America cover the equatorial regions. Wet equatorial forests (gilei), including short-dry-season gilei (deciduous-evergreen forests), and monsoon forests cover the Amazon and adjacent slopes of the Andes and highlands. The climate of these areas has not undergone significant changes since the end of the Mesozoic. And the flora of equatorial America, in its composition, including cycads, club mosses, etc., is a remnant of one of the oldest floras on Earth. It consists of representatives of the Neotropical flora, the formation of which began from the Cretaceous or from the end of the Jurassic period, i.e., when there were still direct connections with Africa and other parts of the hypothetical Gondwana. Therefore, 12% of dicotyledonous plant genera are common to the Neotropical and Paleotropical regions. The long-term isolation of South America in Tertiary times resulted in high endemism of its flora. Not only many plant genera, but even entire families (pitchers - Marcgraviaceae, bromeliads - Bromeliaceae, etc.) are endemic or have the center of their species distribution in South America. From the Neotropical hygrophilic flora, apparently, the flora of savannas, mountain tropical forests and even partly xerophilic flora of semi-deserts. Species of cacti, agaves and bromeliads, for example, originally arose in humid equatorial forests; ecologically adapting and changing, they penetrated the western desert coast, the semi-deserts of Argentina, and the inter-Andean plateaus. Mainly in the form of epiphytes, they are widespread in the Amazon today. The equatorial forests were thus the most important center for the formation of the vegetation cover of South America, most of which is included in the Neotropical floristic region. The flora of savannas and woodlands is almost as ancient. They are located north and south of humid equatorial and monsoon forests on the plains and plateaus of the eastern continent up to 30° S. latitude, and in the west - between 0-5° south. sh., occupying an area approximately equal to the hyla and monsoon forests.
Savannas and woodlands again give way to moist forest formations on the eastern, windward slopes of the highlands and subtropical evergreen mixed (coniferous-deciduous) forests in the cooler, higher regions of the Brazilian Highlands between 24-30 ° S. w. Moist forests also cover the slopes of the southern Andes, south of 38° S. w. Up to 46° south w. they consist of evergreen deciduous and coniferous species (hemigilea). On the western, windward slopes the forests are denser, on the eastern ones they are sparse and have an admixture of deciduous species. In the extreme south of the Patagonian Andes, on the western slopes they transform into mixed, deciduous-evergreen subantarctic forests, and on the eastern slopes into predominantly deciduous ones. Due to the fact that in Quaternary times the southern Andes were almost completely covered by glaciers, the settlement of this section of the mountains occurred relatively recently. Apparently, the center of distribution of flora in the southern Andes after glaciation was the subtropical Andes of central Chile, where during the glaciation there were a number of refuges that allowed many relics to survive. There are habitats of the relict honey palm (YaJaea specfatitfis), Chilean araucaria (Araucaria itnbricata var, araucana) etc., from the Andes of central Chile the southern beech (Nothofagus), alerce (Fitzroya cupressoides var. patagontca) moved north from 38° S (to 32°), as on other continents. in the west of South America, humid forests are replaced by hard-leaved (Mediterranean) forests and shrubs. Young types of meadow-steppe, semi-desert and desert vegetation predominate in the subtropics in the east of the continent, including on the eastern slopes of the Andes. Shrub semi-deserts are also widespread in Patagonia, which lies even further south. the rain shadow of the Andes; the vegetation cover of Patagonia was also formed only in post-glacial times from the Antarctic flora. Patagonia and southern Chile belong to the Antarctic floristic region. The vegetation cover of the intermountain plateaus and western slopes of the Central Andes is very young. Recent uplifts of this area and Quaternary glaciations have caused significant changes in climate and vegetation cover. In Tertiary times, mesophilic tropical flora existed there, and now mountain-steppe, semi-desert and desert types of vegetation dominate. Due to South America's location at predominantly low latitudes, it is dominated by various types of lateritic soils. Hot forest areas with constant and heavy rainfall are characterized by podzolized lateritic soils, which are difficult to separate from the very thick weathering crust. In areas with seasonal moisture, red, brown-red and red-brown soils are typical.
Ancient ferruginous crusts are widespread. Lateritization processes are still evident in the humid subtropics in the east of the continent, where red soils and reddish-black prairie soils are characteristic. Further to the west, as in North America, they are successively replaced by gray-brown soils and gray soils, and in the far west by brown soils. Soil types in cool temperate latitudes are represented by brown forest soils in the west, chestnut and brown, desert-steppe soils in the east. In the Andes there is a clearly defined altitudinal zonation with mountain types of zonal soils. The contrasts in natural conditions and the peculiarities of the paleogeographical development of South America determined the richness and originality of the animal world. The fauna of the mainland is also characterized by great endemism, which made it possible to clearly distinguish the Neotropical zoogeographical kingdom with a single Neotropical region. Endemic are three families of the order of edentates (armadillos, anteaters and sloths), broad-nosed monkeys, bats (vampires), rodents (guinea pigs, agouti, chinchillas), entire orders of birds (nanda ostriches, tinamous and hoatzins, as well as vultures, toucans , 500 species of hummingbirds, many genera of parrots, etc.) Typical reptiles include endemic caimans, iguana lizards and boa constrictors; fish include the electric eel, double-crested siren and others. Insects are particularly diverse and endemistic (3,400 species out of 5,600). Only in the Pleistocene did the jaguar and puma, skunks, otters, tapirs, peccaries and llamas move to South America from North America and spread widely. South America lacks a number of animals that are widespread on other continents (narrow-nosed monkeys, almost no insectivores, few ungulates). Environmental conditions The desert-steppe spaces and cool forests of the southern Andes are sharply different from the hot savannahs and forests of the more northern parts of the continent. Therefore, the fauna of these territories is also significantly different. The southern regions are united into the Chilean-Patagonian zoogeographical subregion, the northern ones into the Brazilian one.
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Unlike North America, where changes in vegetation cover depend largely on changes in temperature conditions, in South America, with its high temperatures, the nature of vegetation depends mainly on the degree of moisture. A large amount of solar heat allows plants of the southern continent to vegetate throughout the year almost everywhere. As in Africa, the main factor determining the duration of the growing season is the degree of moisture. The latter in the hot zone decreases not from the oceans into the interior of the continent, but from the equator to the tropics, and only in the subtropics do differences between the oceanic and inland territories sharply appear. In this regard, the main forest areas in South America cover the equatorial regions. Wet equatorial forests (gilei), including short-dry-season gilei (deciduous-evergreen forests), and monsoon forests cover the Amazon and adjacent slopes of the Andes and highlands. The climate of these areas has not undergone significant changes since the end of the Mesozoic. And the flora of equatorial America, in its composition, including cycads, club mosses, etc., is a remnant of one of the oldest floras on Earth. It consists of representatives of the Neotropical flora, the formation of which began from the Cretaceous or from the end of the Jurassic period, i.e., when there were still direct connections with Africa and other parts of the hypothetical Gondwana. Therefore, 12% of dicotyledonous plant genera are common to the Neotropical and Paleotropical regions. The long-term isolation of South America in Tertiary times resulted in high endemism of its flora. Not only many plant genera, but even entire families (pitchers - Marcgraviaceae, bromeliads - Bromeliaceae, etc.) are endemic or have the center of their species distribution in South America. From the Neotropical hygrophilic flora, apparently, the flora of savannas, mountain tropical forests, and even the partly xerophilic flora of semi-deserts originated. Species of cacti, agaves and bromeliads, for example, originally arose in humid equatorial forests; ecologically adapting and changing, they penetrated the western desert coast, the semi-deserts of Argentina, and the inter-Andean plateaus. Mainly in the form of epiphytes, they are widespread in the Amazon today. The equatorial forests were thus the most important center for the formation of the vegetation cover of South America, most of which is included in the Neotropical floristic region. The flora of savannas and woodlands is almost as ancient. They are located north and south of humid equatorial and monsoon forests on the plains and plateaus of the eastern continent up to 30° S. latitude, and in the west - between 0-5° south. sh., occupying an area approximately equal to the hyla and monsoon forests.
Savannas and woodlands again give way to moist forest formations on the eastern, windward slopes of the highlands and subtropical evergreen mixed (coniferous-deciduous) forests in the cooler, higher regions of the Brazilian Highlands between 24-30 ° S. w. Moist forests also cover the slopes of the southern Andes, south of 38° S. w. Up to 46° south w. they consist of evergreen deciduous and coniferous species (hemigilea). On the western, windward slopes the forests are denser, on the eastern ones they are sparse and have an admixture of deciduous species. In the extreme south of the Patagonian Andes, on the western slopes they transform into mixed, deciduous-evergreen subantarctic forests, and on the eastern slopes into predominantly deciduous ones. Due to the fact that in Quaternary times the southern Andes were almost completely covered by glaciers, the settlement of this section of the mountains occurred relatively recently. Apparently, the center of distribution of flora in the southern Andes after glaciation was the subtropical Andes of central Chile, where during the glaciation there were a number of refuges that allowed many relics to survive. There are habitats of the relict honey palm (YaJaea specfatitfis), Chilean araucaria (Araucaria itnbricata var, araucana) etc., from the Andes of central Chile the southern beech (Nothofagus), alerce (Fitzroya cupressoides var. patagontca) moved north from 38° S (to 32°), as on other continents. in the west of South America, humid forests are replaced by hard-leaved (Mediterranean) forests and shrubs. Young types of meadow-steppe, semi-desert and desert vegetation predominate in the subtropics in the east of the continent, including on the eastern slopes of the Andes. Shrub semi-deserts are also widespread in Patagonia, which lies even further south. the rain shadow of the Andes; the vegetation cover of Patagonia was also formed only in post-glacial times from the Antarctic flora. Patagonia and southern Chile belong to the Antarctic floristic region. The vegetation cover of the intermountain plateaus and western slopes of the Central Andes is very young. Recent uplifts of this area and Quaternary glaciations have caused significant changes in climate and vegetation cover. In Tertiary times, mesophilic tropical flora existed there, and now mountain-steppe, semi-desert and desert types of vegetation dominate. Due to South America's location at predominantly low latitudes, it is dominated by various types of lateritic soils. Hot forest areas with constant and heavy rainfall are characterized by podzolized lateritic soils, which are difficult to separate from the very thick weathering crust. In areas with seasonal moisture, red, brown-red and red-brown soils are typical.
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South America is a unique continent. More than 50% of all equatorial and tropical forests growing on Earth are located in this part of the world. Most of the continent's territories are located in tropical and equatorial zones. The climate is humid and warm, the temperature in winter and summer does not differ much and in most parts of the continent is always positive. The natural zones of South America are unevenly distributed due to the large differences in the relief of the eastern and western parts. The fauna and flora are represented by a large number of endemic species. Almost all minerals are mined on this continent.
This topic is studied in detail in the school subject geography (7th grade). “Natural areas of South America” is the name of the lesson topic.
Geographical position
South America is located entirely in the Western Hemisphere, most of its territories lie in tropical and equatorial latitudes.
The mainland includes the Malvinas Islands, which lie in the shelf zone Atlantic Ocean, and the islands of Trinidad and Tobago. The Tierra del Fuego archipelago is separated from the main part of South America by the Strait of Magellan. The length of the strait is about 550 km, it is located in the south.
In the north is Lake Maracaibo, which is connected by a narrow strait to the Gulf of Venezuela, one of the largest in the Caribbean Sea.
The coastline is not very indented.
Geological structure. Relief
Conventionally, South America can be divided into two parts: mountainous and flat. In the west there is the folded belt of the Andes, in the east there is a platform (ancient South American Precambrian).
The shields are elevated sections of the platform; in relief they correspond to the Guiana and Brazilian highlands. From the east of the Brazilian Highlands, the sierras - blocky mountains - formed.
The Orinoco and Amazonian lowland plains are troughs of the South American platform. The Amazonian lowland occupies the entire part of the territory from the Atlantic Ocean to the Andes mountains, limited to the north by the Guiana Plateau, and to the south by the Brazilian Plateau.
The Andes are among the highest mountain systems on the planet. And this is the longest chain of mountains on Earth, its length is almost 9 thousand km.
The earliest folding in the Andes is the Hercynian, which began to form in the Paleozoic. Mountain movements continue to occur today - this zone is one of the most active. This is evidenced by strong earthquakes and volcanic eruptions.
Minerals
The continent is very rich in various minerals. Oil, gas, hard and brown coal, as well as various metal and non-metallic ores (iron, aluminum, copper, tungsten, diamonds, iodine, magnesite, etc.) are mined here. The distribution of minerals depends on the geological structure. Iron ore deposits belong to ancient shields, this is the northern part of the Guiana Highlands and the central part of the Brazilian Highlands.
Bauxite and manganese ores are concentrated in the weathering crust of the uplands.
In the depressions of the foothills, on the shelf, in the troughs of the platform, the extraction of combustible minerals is carried out: oil, gas, coal.
Emeralds are mined in Colombia.
Molybdenum and copper are mined in Chile. This country ranks second (like Zambia) in the world in the extraction of natural resources.
These are the natural zones of South America, the geography of distribution of minerals.
Climate
The climate of the mainland, like any continent, depends on several factors: the currents washing the continent, macrorelief, and atmospheric circulation. Since the continent is crossed by the equator line, most of it is located in the subequatorial, equatorial, subtropical, and tropical zones, therefore the amount of solar radiation is quite large.
Characteristics of natural zones of South America. Zone of humid equatorial forests. Selva
This zone in South America occupies a large area: the entire Amazonian lowland, the nearby foothills of the Andes and part of the nearby east coast. Equatorial rainforests or as they are called local residents, "selvas", which translates from Portuguese as "forest". Another name proposed by A. Humboldt is “Gilea”. Equatorial forests are multi-tiered, almost all the trees are intertwined with various types of vines, there are many epiphytes, including orchids.
Typical fauna are monkeys, tapirs, sloths, a huge variety of birds and insects.
Zone of savannas and woodlands. Llanos
This zone covers the entire Orinoco Lowland, as well as the Brazilian and Guiana Highlands. This natural area also called llanos or campos. The soils are red-brown and red ferralitic. Most of the territory is occupied by tall grasses: cereals, legumes. There are trees, usually acacias and palms, as well as mimosa, bottle tree, and quebracho - an endemic species growing in the Brazilian Highlands. Translated it means “break the axe”, because The wood of this tree is very hard.
Among the animals, the most common are: baker pigs, deer, anteaters and cougars.
Zone of subtropical steppes. Pampa
This zone covers the entire La Plata lowland. The soil is red-black ferralitic, it is formed as a result of the rotting of pampas grass and tree leaves. The humus horizon of such soil can reach 40 cm, therefore the land is very fertile, which local residents take advantage of.
The most common animals are llama and Pampas deer.
Semi-desert and desert zone. Patagonia
This zone is located in the “rain shadow” of the Andes, because mountains block the path of moist air masses. The soils are poor, brown, gray-brown and gray-brown. Sparse vegetation, mainly cacti and grasses.
Among the animals there are many endemic species: Magellanic dog, skunk, Darwin's ostrich.
Temperate forest zone
This zone is located south of 38° S. Its second name is hemigels. These are evergreen, permanently moist forests. The soils are mainly forest brown soils. The vegetation is very diverse, but the main representatives of the flora are southern beech, Chilean cypresses and araucarias.
Altitudinal zone
Altitudinal zonation is characteristic of the entire Andes region, but it is most fully represented in the equator region.
Up to an altitude of 1500 m there is “hot land”. Humid equatorial forests grow here.
Up to 2800 m is temperate land. Tree ferns and coca bushes grow here, as well as bamboo and cinchona.
Up to 3800 - a zone of crooked forests or a belt of low-growing high-mountain forests.
Up to 4500 m lies paramos - a zone of high-mountain meadows.
“Natural zones of South America” (7th grade) is a topic in which one can see how individual geocomponents are interconnected and how they influence the formation of each other.
Much of South America is exceptionally rich in flora. This is due to both the modern natural conditions of the continent and the peculiarities of its development. Tropical flora of South America developed from the end of the Mesozoic era. Its development has proceeded continuously until the present time, without being disrupted by glaciation or significant fluctuations in climatic conditions, as was the case on other continents.
On the other hand, the formation of the vegetation cover of the South America starting from the Tertiary period, it occurred in almost complete isolation from other large land areas. The main features of the flora of South America are connected with this: its antiquity, species richness and high degree endemism.
The vegetation cover in South America has changed significantly less under human influence than on other continents of the globe. The population density on the mainland is low, and vast areas in some parts of it are to this day almost completely uninhabited. Such areas have retained their natural soil and vegetation cover unchanged.
The vegetation of the South is a source of huge natural resources - food, feed, technical, medicinal, etc. But they are still very little used.
Flora of South America gave humanity a number of important cultivated plants. The first place among them is occupied by potatoes, the culture of which was known to the Indians long before the arrival of Europeans and is widespread in various regions of South America today. Then from South America come the most common rubber plant, Hevea, chocolate tree, cinchona tree, grown in many tropical areas of the globe.
South America lies within two floristic regions. The main part of the continent is included within the Neotropical region. Its flora contains some elements common to Africa, which indicates the existence of land connections between the continents until the Tertiary period.
The part of the continent south of the parallel 40° S. w. belongs to the Antarctic floristic region. There are similarities between the flora of this part of the continent and the flora of Antarctica, Australia and New Zealand, which also indicates the existence of connections between these continents during geological history.
General picture of soil and vegetation zones in the Neotropical region of South America is somewhat reminiscent of Africa. But the ratio of individual types of vegetation and their species composition on these continents are different. If the main type of vegetation in Africa is savanna, That The vegetation cover of South America is especially characterized by tropical rainforests, which have no equal on Earth either in the richness of species or in the vastness of the territory they occupy.
Tropical rainforests on lateritic podzolized soils spread in South America to huge area. The population of Brazil calls them Selvas. Selvas occupy a significant part of the Amazonian lowland and adjacent areas of the Orinoco lowland, the slopes of the Brazilian and Guiana highlands. They are also characteristic of the Pacific coastline within Colombia and Ecuador. Thus, tropical rainforests cover areas with an equatorial climate, but in addition, they grow on the slopes of the Brazilian and Guiana highlands, facing the Atlantic Ocean at higher latitudes, where there is abundant trade wind rain throughout the year.
In the rich tropical forests of the Amazonian lowland you can find many valuable plants. These forests are characterized by great height and complexity of the forest canopy. In non-flooded areas, the forest has up to 12 tiers, and the height of the tallest trees reaches 80 and even 100 m. More than a third plant species endemic in these forests. Tropical rainforests rise along the mountain slopes to approximately 1000-1500 m, without undergoing significant changes. Higher up they give way to depleted mountain tropical forests.
As climate changes, tropical rainforests are turning into red-soil savannas. In the Brazilian Highlands, between savannas and rainforest, there is a strip of almost pure palm forests. Savannas are distributed over a large part of the Brazilian Highlands, mainly in its interior regions. In addition, they occupy large areas in the Orinoco Lowland and the central regions of the Guiana Highlands.
In the south - in Brazil - they are known as campos. Their vegetation consists of tall grasses. Woody vegetation is either completely absent or represented by individual specimens of mimosa, cacti and other xerophytic or succulent trees. Campos of the Brazilian Highlands is a valuable but relatively underutilized grassland.
In the north, in Venezuela and Guiana, savannas are called llanos. There, along with tall and varied grass vegetation, there are isolated palm trees, giving the landscape a unique appearance.
In the Brazilian Highlands, in addition to the typical savanna, there are similar types vegetation, adapted to endure long dry periods. In the northeast of the Brazilian Highlands, a significant area is occupied by the so-called caatinga, which is a sparse forest of drought-resistant trees and shrubs. Many of them lose their leaves during the dry season, others are distinguished by swollen trunks in which moisture accumulates. Caatinga produces red-brown soils.
On the Gran Chaco plain, in particularly arid areas, thorny dry-loving shrubs and sparse forests grow on red-brown soils. They contain a number of endemic woody forms containing large amounts of tannins.
On the Pacific coast, south of the tropical rainforests, you can also find a narrow strip of savanna vegetation, which then quite quickly turns into semi-desert and desert.
Large territories With mountain-tropical desert vegetation and soils are located in the interior highlands of the Andes.
Subtropical vegetation occupies relatively small areas in South America. area. However, the diversity of vegetation types in subtropical latitudes is quite large.
The extreme southeast of the Brazilian Highlands, with rainfall throughout the year, is covered with subtropical araucaria forests with an understory of various shrubs, including Paraguayan tea. Paraguayan tea leaves are consumed by the local population to make a common hot drink that replaces tea. By the name of the round vessel in which this drink is is being manufactured, it is often called "mate" or "yerba mate".
The second type of subtropical 'vegetation of South America - the subtropical steppe or pampa - is characteristic of the eastern, most humid parts of the La Plata lowland south of 30° S. This is herbaceous cereal vegetation, on fertile reddish-black soils formed on volcanic rocks. It consists of South American species of those genera of cereals that are widespread in Europe in the temperate steppes. There are species of feather grass, bearded grass, and fescue. Unlike the temperate steppes, the vegetation in the pampa grows throughout the year. The pampa is connected with the forests of the Brazilian Highlands by a transitional type of vegetation, where grasses are combined with thickets of evergreen shrubs.
To the west and south of the pampa, as precipitation decreases, vegetation of dry subtropical steppes and semi-deserts appears on gray-brown soils, gray soils and saline soils.
Subtropical vegetation and soils of the Pacific coast, according to the peculiarities of climatic conditions, resemble in appearance the vegetation and soils of the European Mediterranean. Thickets of evergreen shrubs on brown soils predominate.
Very unique vegetation moderate latitudes of South America. There are two main types of vegetation cover, which differ sharply from each other, corresponding to differences in the climate of the eastern and western parts of the southern tip of the continent. The extreme southeast (Patagonia) is characterized by vegetation of dry steppes and semi-deserts of the temperate zone. This is actually a continuation of the western semi-deserts parts pumps V conditions of harsher and colder climates. The soils are dominated by chestnut and gray soils; saline soils are widespread. The vegetation cover is dominated by grasses (for example, silvery Argentine bluegrass) and various xerophytic shrubs, such as cacti, mimosas, etc.
The extreme southwest of the continent with its oceanic climate, insignificant Due to annual temperature differences and high annual precipitation, it has a unique vegetation, very ancient and rich in composition. These are moisture-loving evergreen subantarctic forests, multi-tiered and very diverse in composition. In terms of richness of species and height, they are not inferior to tropical forests. They abound in lianas, mosses, and lichens. Along with various tall conifers, evergreen deciduous trees, such as southern beeches (Nothofagus), are common. These moisture-soaked forests are difficult to clear and uproot. They are still preserved over large areas in an intact form and, almost without changing their composition, rise along the mountain slopes to a height of 2000 m. In these forests on In the south, podzolic soils predominate, turning into forest brown soils in more northern regions.
Europe. General horizontal zonality and landscape-climatic zonality are expressed on the continent, although the configuration of the belts and especially the zones within them is not strictly latitudinal (with the exception of the East European Plain).
The formation of the soil cover of Europe was significantly influenced by the Quaternary glaciation, marine transgressions and Alpine orogenesis. Therefore, relatively young soils formed on glacial and post-glacial deposits predominate here.
Water-accumulative plains and lowlands of Northern and Eastern Europe are characterized by the predominance of acidic siallitic soils under boreal and subboreal forests. The erosive plains of Central Europe with subboreal forests developed on acidic siallitic poorly differentiated soils are distinguished by a comparative uniformity of soil cover.
The Mediterranean region is occupied predominantly by neutral siallitic soils on dense carbonate rocks. Characteristic feature mountainous regions of the alpine zone of Europe is the presence of a vertical-zonal macrostructure of the soil cover.
South-Eastern Europe- These are semi-arid and arid landscapes from steppes to deserts with a corresponding zonal structure of the soil cover. This is a zone of modern continental salt accumulation.
Asia. The geographic configuration of zones (Arctic, polar, boreal, subboreal, subtropical, tropical) and especially zones with a fairly clear landscape-geographical zonation is not strictly latitudinal. Classically, zoning manifests itself in the West Siberian and Turan lowlands. Other parts of the continent are characterized by a complex mosaic of soils.
Within the plains and mountain systems of Western, Middle and Central Asia, a vast desert and semi-desert belt was formed due to the peculiarities of the climate and morphostructure of the continent. The wide distribution of mountain systems, highlands and high plateaus on the continent led to the formation of poorly developed and poorly differentiated soils in these vast territories. The isolation of significant intracontinental drainless basins led to the manifestation of ancient and modern salt accumulation in them.
The areas of permafrost in the north and northeast of the continent are characterized by the presence of cryogenic soils.
Volcanic soils are common within the Pacific volcanic belt. In eastern Asia, from the boreal to the tropical zone, due to the absence of high mountain systems and the presence of a monsoon climate, forest vegetation predominates, gradually changing from north to south as heat increases; Accordingly, the soils change from podburs to ferrallitic ones.
The intense uplifts of the highlands that have continued to this day cause the continuous denudation of mountain systems and the formation of young alluvial lowlands with fertile soils on the outskirts of the continent due to redeposited material.
The diversity of soil cover ages and differences in the evolutionary stages of soil development are quite clearly evident in Asia; polycyclic soils are widespread due to repeated changes in the physical and geographical environment.
Africa. The specificity of the soil cover of the African continent is a clear latitudinal zonation, only partially disrupted due to the phenomena of block tectonics of the continent. The zonation is especially clear west of 30° east longitude. The participation of deserts in the soil cover of the continent is significant; they are symmetrically located on the northern and southern outskirts and occupy about 20% of the area.
About 30% of Africa is deprived of soil cover: the surface of sandy and rocky deserts, rock outcrops, laterite crusts and shells exposed by erosion. The latter are widespread in the equatorial belt (15° N - 10° S).
The processes of modern ferruginization of soils in the zone of primary and secondary savannas are significantly developed on the continent. In areas not subject to tectonic processes at least since Tertiary time, significant areas are occupied by ancient soils and weathering crusts that reach great thickness, especially on basic and ultrabasic rocks.
In zones of recent and modern volcanism, young soils of the Andosol type are common. In the Sahara and other desert areas of the continent, paleohydrogenic salt accumulations are developed.
Africa is characterized by latitudinal development of weathering processes throughout the entire territory west of 30° east longitude and the almost complete predominance of fersiallite weathering (with the exception of North Africa) east of this meridian.
North America. The modern complex nature of the soil cover of North America is due to the interaction of a number of factors: a) the significant extent of the continent from north to south; b) the presence of a mountain barrier along the western coast; c) Quaternary glaciation and the wide distribution of various glacial, moraine, fluvio-glacial and loess deposits.
Latitudinal thermal zonation is most clearly manifested in the soil cover on the plains of the eastern and central parts of the continent. In the west it is broken by the Cordillera, which stretches across all thermal zones; they largely determine the distribution of precipitation on the interior plains and highlands. The combination of latitudinal thermal zones and longitudinal moisture zones on the plains creates unique hydrothermal conditions and associated weathering and soil formation processes.
Within the same moisture zone in North America, regular changes in vegetation and soils are observed from north to south in accordance with changes in thermal conditions, and within the same thermal zone there are often even more dramatic changes in soils and vegetation in directions from the coastal to inland areas. A similar pattern manifests itself in the subtropical and temperate zones and is leveled out in the subarctic and arctic, in which the direction of thermal zones and moisture zones coincides.
Just like in Europe, there were several glaciations in North America. Glaciers covered an area up to 40° N. latitude, and moraine deposits reached 38° N. sh., i.e. penetrated into the subtropical zone. Glaciation played a significant role in the formation of a variety of soil-forming rocks, landforms and soils in the regions it covered. In the northern part of the continent (up to 55° N), permafrost soils are widespread and cryogenic soils predominate in the soil cover.
South America. The general nature of the soil cover of South America is determined by: the significant extent of the continent from north to south; the presence of a mountain barrier along the western coast; the predominance of eastern moisture transfer from the Atlantic Ocean in the equatorial, tropical and subtropical zones; the presence along the Pacific coast of the cold Peruvian Current, and along the coast of Patagonia the cold Falkland Current; the development in the tropical and equatorial zones of ancient planation surfaces with a thick ferrallitic, often laterized, weathering crust; the spread of alluvial plains in the subtropical part of the continent; the presence of active volcanoes and associated volcanogenic sediments in the northern and southern Andes.
The meridional extension of moisture zones in the subtropical zone determines the same direction of landscape and soil zones: in the north, in the eastern, most humidified part, there are subtropical moist forests on red soils and tall grass prairies on chernozem-like soils. In the more inland areas of the dry pampa there are brunizems, and in the Andean part there are dry and desert steppes on gray-brown soils in combination with solonetzes and solonchaks.
On the Pacific coast and the western slopes of the Andes due to minimum quantity precipitation is dominated by desert landscapes and soils with pronounced salt accumulation phenomena.
In the equatorial belt of South America, on the low-lying coasts and highlands under the humid equatorial tropical forests of the Amazon basin, yellow and red ferrallitic soils are common. To the north and south of the equator there are tropical regions with a pronounced dry period; Under seasonally wet tropical forests and savannas, ferrallitic and fersiallite soils predominate here.
Australia. Most of the continent's territory is located in the region of tropical maximum pressure, which largely determines the dominance of landscapes of tropical deserts and semi-deserts with soils of varying degrees of leaching, carbonate content and salinity.
Northernmost part of Australia- landscapes of tropical variable-humid forests, forested savannas and woodlands on ferrallite differentiated and undifferentiated soils, sometimes lateritized. The extreme southwestern and southeastern parts of the continent and the island of Tasmania are in the subtropical zone with landscapes of dry forests and shrubs on brown, red-brown and gray-brown soils.
Features and configuration of soil zones in Australia are caused by the presence of the East Australian Cordillera mountain barrier in the east of the continent. This is a barrier to the penetration of the humid southeastern trade wind into the interior of the continent. The bulk of precipitation therefore falls on the eastern slopes of the mountains, while the western slopes and foothill plains are in a drier climate. Soil zones in the eastern part of Australia have a meridional direction. The eastern slopes of the mountains are occupied by tropical forests on acidic podzolized brown forest soils, red soils and yellow soils. The western slopes of the mountains and high plateaus are occupied by subtropical woodlands and savannas. Deep into the continent behind the chain of mountains extends a belt of dry grass savannas in the north and xerophilic woodlands and shrubs in the south, with a predominance of saline, carbonate and solonetzic soils.
Since Paleozoic times, much of the continent has not been covered by sea, processes of long-term continental denudation, weathering and soil formation developed on it. Over large areas of Australia, the peneplain surface with ancient lateritized kaolinite weathering crusts, which are not characteristic of modern physiographic conditions, is well preserved.
Characteristics of one of the soil types (optional):
Polar zone soils
The most common type of automorphic soils in the Arctic is arctic-tundra soils. The thickness of the soil profile of these soils is determined by the depth of seasonal thawing of the soil-ground layer, which rarely exceeds 30 cm. The differentiation of the soil profile due to cryogenic processes is weakly expressed. In soils formed in the most favorable conditions, only the plant-peaty horizon (A 0) is well defined and the thin humus horizon (A 1) is much worse.
In arctic-tundra soils, due to excess atmospheric moisture and the high surface of permafrost, high humidity is maintained throughout the short season of positive temperatures. Such soils have a weak acidic or neutral reaction (pH 5.5 to 6.6) and contain 2.5–3% humus. In relatively quickly drying areas with a large number of flowering plants, soils with a neutral reaction and a high humus content (4–6%) are formed.
The landscapes of Arctic deserts are characterized by salt accumulation. Salt efflorescence is common on the soil surface, and in summer small brackish lakes can form as a result of salt migration.
soils of the tundra (subarctic zone)
The soil-forming rocks are dominated by various types of glacial deposits.
Tundra-gley soils are common above the surface of permafrost; they are formed under conditions of difficult drainage of soil-groundwater and oxygen deficiency. They, like other types of tundra soils, are characterized by the accumulation of weakly decomposed plant residues, due to which in the upper part of the profile there is a well-defined peaty horizon (At), consisting mainly of organic matter. Below the peaty horizon there is a thin (1.5–2 cm) humus horizon (A 1) of brown-brown color. The humus content in this horizon is about 1–3%, the reaction is close to neutral. Under the humus horizon lies a gley soil horizon of a specific bluish-gray color, which is formed as a result of reduction processes under conditions of water saturation of the soil layer. The gley horizon continues to the upper surface of the permafrost. Sometimes, between the humus and gley horizons, a thin spotted horizon with alternating gray and rusty spots appears. The thickness of the soil profile corresponds to the depth of seasonal thawing of the soil.
soils of the deciduous forest zone:
1. Gray forest soils formed in inland areas (central regions of Eurasia and North America). In Eurasia, these soils stretch in islands from the western borders of Belarus to Transbaikalia. Gray forest soils are formed under continental climatic conditions. In Eurasia, the severity of the climate increases from west to east, average January temperatures vary from –6° C in the west of the zone to –28° C in the east, the duration of the frost-free period is from 250 to 180 days. Summer conditions are relatively the same - the average July temperature ranges from 19 to 20 ° C. Annual precipitation varies from 500–600 mm in the west to 300 mm in the east. The soils are soaked by precipitation to great depths, but since the groundwater in this zone lies deep, the leaching water regime is not typical here; only in the most humidified areas does the soil layer become completely wetted to groundwater.
The vegetation under which gray forest soils formed is represented mainly by broad-leaved forests with rich grass cover. To the west of the Dnieper there are hornbeam-oak forests, between the Dnieper and the Urals there are linden-oak forests, to the east of the Urals, within the West Siberian Lowland, birch and aspen forests predominate, and larch appears even further east.
The mass of litter from these forests significantly exceeds the mass of litter from taiga forests and amounts to 70–90 c/ha. The litter is rich in ash elements, especially calcium.
The soil-forming materials are predominantly cover loess-like loams.
Favorable climatic conditions determine the development of soil fauna and microbial populations. As a result of their activity, a more energetic transformation of plant residues occurs than in soddy-podzolic soils. This causes a more powerful humus horizon. However, part of the litter is still not destroyed, but accumulates in the forest litter, the thickness of which is less than the thickness of the litter in soddy-podzolic soils.
Structure of the gray forest soil profile:
A 0 – forest litter from tree and grass litter, usually of low thickness (1–2 cm);
A 1 – humus horizon of gray or dark gray color, fine- or medium-clumpy structure, containing a large number of grass roots. In the lower part of the horizon there is often a coating of siliceous powder. The thickness of this horizon is 20–30 cm.
A 2 is a washout horizon, gray in color, with an unclear leaf-plate structure and a thickness of about 20 cm. Small ferromanganese nodules are found in it.
B – inwash horizon, brownish-brown in color, with a clearly defined nutty structure. Structural units and pore surfaces are covered with dark brown films, and small ferromanganese nodules are found. The thickness of this horizon is 80–100 cm.
C – soil-forming rock (cover loess-like loam of a yellowish-brown color with a well-defined prismatic structure, often containing carbonate formations).
The type of gray forest soils is divided into three subtypes - light gray, gray and dark gray, the names of which are associated with the intensity of the color of the humus horizon. With the darkening of the humus horizon, the thickness of the humus horizon slightly increases and the severity of leaching of these soils decreases. The eluvial horizon A 2 is present only in light gray and gray forest soils; dark gray soils do not have it, although the lower part of the humus horizon A 1 has a whitish tint. The formation of subtypes of gray forest soils is determined by bioclimatic conditions, therefore light gray forest soils gravitate to the northern regions of the strip of gray soils, gray ones to the middle ones, and dark gray ones to the southern ones.
Gray forest soils are much more fertile than soddy-podzolic soils; they are favorable for growing grain, fodder, horticultural and some industrial crops. The main disadvantage is the greatly reduced fertility as a result of centuries of use and significant destruction as a result of erosion.
2. Brown forest soils formed in areas with a mild and humid oceanic climate, in Eurasia - this Western Europe, Carpathians, Mountainous Crimea, warm and humid regions of the Caucasus and Primorsky Krai of Russia, In North America - the Atlantic part of the continent.
The annual precipitation is significant (600–650 mm), but most of it falls in the summer, so the flushing regime operates for short periods of time. At the same time, mild climatic conditions and significant atmospheric humidity activate the processes of transformation of organic matter. A significant mass of litter is processed and mixed by numerous invertebrates, contributing to the formation of a humus horizon. When humic substances are destroyed, clay particles begin to slowly move into the leaching horizon.
The profile of brown forest soils is characterized by a poorly differentiated and thin, not very dark humus horizon.
Profile structure:
A 1 – humus horizon of gray-brown color, the humus shade gradually decreases at the bottom, the structure is lumpy. Thickness – 20–25 cm.
B – washout horizon. Bright brown-brown at the top, clayey, down brown tint will decrease and the color approaches the color of the parent rock. The thickness of the horizon is 50–60 cm.
C – soil-forming rock (fawn-colored loess-like loam, sometimes with carbonate formations).
With a large amount of applied fertilizers and rational agricultural technology, these soils produce very high yields of various agricultural crops, in particular, the highest yields of grain crops are obtained on these soils. In the southern regions of Germany and France, brown soils are used mainly for vineyards.
bog soils
Swamp soils are soils that form under conditions of prolonged or constant excess moisture (swamping) under moisture-loving swamp vegetation. Typically, bog soils form in the forest zone of temperate zones. After drainage, crops are grown on the swamp soils and peat is extracted. Swamp soils are common in the Russian Federation, Belarus, Ukraine, Canada, USA, Brazil, Argentina, Indonesia, etc. Swamp soils are divided into peat and peat-gley soils.
General diagram of the structure of the soil cover of the globe
To identify the general patterns of horizontal zonation of the soil cover, let us turn to the diagram of soil zones on the “ideal continent”. The latter is a flat landmass stretching from the polar latitudes to the equator and washed by oceans to the east and west.
Polar belt. This belt includes soil zones: 1) Arctic desert soils; 2) arctic-tundra soils; 3) tundra gley soils. The first soil zone is located north of 75-80° N. w. Arctic desert soils are found in the northern part of Greenland and the islands of the Canadian archipelago, on Spitsbergen, Franz Josef Land, and the Severnaya Zemlya islands.
On real continents - North America and Eurasia - the boundary of the Arctic soil zone is advanced furthest south in the eastern part of the continents. In North America, this phenomenon is associated with the cooling effect of the Greenland glaciers, and in East Asia - with its close position to the global pole of cold.
Tundra soil zone in the form of a latitudinal strip extends across the entire ideal continent. Its southern border has an arcuate shape: its northernmost position is in the central continental sector; along the eastern and western coasts, the southern border of tundra soils runs along 62-63° N. w.
The shift of the boundaries of tundra soils to the south in the oceanic, wetter sectors of the continents is associated with an increase in absolute and relative air humidity here. The more continental the climate and drier the air, the further north (even in low temperatures) forest vegetation moves.
Boreal belt. In the most humid, oceanic sectors of the continents at a latitude of about 60° N. w. The soils of the southern tundra are replaced by areas of subarctic meadows and woodlands with soddy subarctic coarse humus and soddy-peaty soils.
The main part of the boreal belt is occupied by a forest zone, which has the shape of an arc, curved to the north. Three sectors are clearly visible: the western and eastern podzolic soils and the central - the coldest and continental sector - podzolic and taiga-permafrost soils. The width of the last sector decreases as you approach the western and eastern sectors. The zone of podzolic soils, depicted on old diagrams and maps as a continuous strip across the entire Eurasian continent, on modern maps separated by the area of distribution of taiga-permafrost soils into two segments.
Subboreal belt. This belt is characterized by a variety of soil zones and a more complex structure of horizontal zoning. The following are distinguished: 1) the inland sector with a wide range of latitudinal soil zones rapidly changing from north to south; 2) two symmetrical oceanic sectors with uniform soil cover; 3) a sector transitional from inland to eastern, where a series of inland zones changes the latitudinal direction to the meridional in accordance with the increase in climate aridity from the eastern coasts with a monsoon climate to the interior parts of the continents.
The tendency towards a change in the latitudinal extent of intracontinental zones to the meridional one can also be traced during the transition to the western oceanic sector, but to a lesser extent, since an increase in climate dryness is observed not only towards the central parts of the continents, but also to the south, with approaching the subtropical zone.
In the inland sector there are gray forest soils, chernozems, chestnut soils, brown desert-steppe and gray-brown desert soils. They form a system of concentric arcs open to the south. The northernmost position of the zone boundary is confined to the inner, driest part of the continents, where the northern border of the steppes and accompanying chernozems is located at 55-57° N. latitude, chestnut soils - about 52°, brown desert-steppe soils reaches 48-50° N. w. As we approach more humid, oceanic regions, all soils shift south in the west to 45° N. latitude, in the east - up to 38° N. w.
The zone of gray forest soils of broad-leaved and small-leaved forests is very narrow, broken and expressed only in the inland sector. As it approaches the oceanic coasts, it thins out and is replaced by near-oceanic, rather wide areas of brown forest soils. These soil-bioclimatic regions do not have the form of latitudinal zones. In contrast to the inland sector with rapid change and diversity of zones, these areas are characterized by uniformity of bioclimatic conditions and, to some extent, soils.
Subtropical zone. It is characterized by the absence of pronounced latitudinal soil zones, with the exception of the vast area of subtropical deserts and their characteristic desert soils.
The eastern coastal sector is located in the area of the eastern monsoons. Here, yellow soils and red soils are formed under evergreen subtropical forests. They are replaced to the west by a series of meridional soil zones of reddish-black soils of subtropical prairies, brown soils of xerophytic subtropical forests and shrubs, chernozem soils of subtropical steppes, gray-brown soils of shrub steppes and gray soils of subtropical semi-deserts.
The western oceanic sector of the subtropical zone, in contrast to the eastern one, is characterized by a “Mediterranean” type of climate with a pronounced dry summer period and a more or less humid winter period. Depending on the degree of moisture, brown soils of subtropical forests and shrubs, gray-brown soils of xerophytic shrub steppes and gray soils of semi-deserts alternate here.
Almost all of these areas have complex terrain with alternating mountain ranges, plateaus and intermountain depressions. Therefore, in the western oceanic sector of the subtropical belt on real continents, horizontal soil zones are not expressed; mountain zoning dominates here.
Tropical and equatorial zones. They are characterized by the presence of latitudinal soil zones, with the desert zone in the tropical zone extending to the western coasts.
In the direction from deserts to the equator, the following soil-bioclimatic zones successively change: desert savannas, dry savannas, xerophytic tropical forests, seasonally wet tropical forests and tall grass savannas, permanently wet tropical forests. Each of these zones corresponds to a specific spectrum of soils. On the diagram of an ideal continent, in the eastern oceanic sector, ferrallitic differentiated soils, as well as red-brown savannas, penetrate to the north. The latitudinal zones here bend and acquire a meridional character.
A mirror image of the zone systems in the southern and northern hemispheres is observed only for the equatorial, tropical and partly subtropical zones. In the subboreal zone of the southern hemisphere, the position of semi-desert landscapes is unusual; directly off the west coast. The reason for this is cold currents and mountain ranges in the west.
The structure of the actual horizontal zoning of different belts, the configuration and direction of the zones are different due to spatiotemporal changes in hydrothermal conditions.