Geography of South America: geology, climate, deserts, reservoirs, natural resources and ecology. Geography presentation on the topic "Soil of South America" ​​(Grade 7)

see also nature photos of South America: Venezuela (Orinoco and Guiana Plateau), Central Andes and Amazonia (Peru), Precordillera (Argentina), Brazilian Highlands (Argentina), Patagonia (Argentina), Tierra del Fuego (from the section Natural landscapes of the world).

South America is characterized by a large diversity zonal types of soil and vegetation cover and exceptional richness of flora, including tens of thousands of plant species. This is due to the position of South America between the subequatorial belt of the northern hemisphere and the temperate belt of the southern hemisphere, as well as the peculiarities of the development of the mainland, which first took place in close connection with other continents of the southern hemisphere, and later - in almost complete isolation from large land masses, except for connections with North America through the Isthmus of Panama.

Most of South America, up to 40 ° S, together with Central America and Mexico forms Neotropical floristic kingdom. The southern part of the mainland is within Antarctic realm(Fig. 84).

Rice. 84. Floristic zoning of South America (according to A.L. Takhtadzhyan)

Within the land that connected the South American platform with the African platform, obviously, there was a common for both continents flora formation center savannas and tropical forests, which explains the presence in their composition of some common species and genera of plants. However, the separation of Africa and South America at the end of the Mesozoic led to the formation of independent flora on each of these continents and the separation of the Paleotropical and Neotropical kingdoms. The Neotropics are characterized by a great richness and a high degree of endemism of the flora, due to the continuity of its development since the Mesozoic and the presence of several large centers of speciation.

The Neotropics are characterized by endemic families like bromeliads, nasturtiums, cannas, cacti. The oldest center for the formation of the cactus family was apparently located on the Brazilian Highlands, from where they spread throughout the mainland, and after the emergence of the Isthmus of Panama in the Pliocene, they also penetrated to the north, forming a secondary center on the Mexican Highlands.

Flora of the eastern part South America is much older than the flora of the Andes. The formation of the latter occurred gradually, as the mountain system itself arose, partly from elements of the ancient tropical flora of the east, and to a large extent from elements that penetrated from the south, from the Antarctic region, and from the north, from the North American Cordillera. Therefore, there are large species differences between the flora of the Andes and the Extra-Andean East.

Within Antarctic realm south of 40°S there is an endemic, not rich in species, but very peculiar flora. It was formed on the ancient Antarctic continent before the beginning of the continental glaciation of Antarctica. Due to cooling, this flora migrated to the north and has survived to this day in small areas of land within the temperate zone of the southern hemisphere. It reached its greatest development in the southern part of the mainland. The Antarctic flora of South America is characterized by representatives of the bipolar flora found on the arctic and subarctic islands of the northern hemisphere.

The flora of the South American continent has given mankind many valuable plants included in the culture not only in the Western Hemisphere, but also beyond. This is primarily potatoes, the ancient centers of cultivation of which are located in the Peruvian and Bolivian Andes, north of 20 ° S, as well as in Chile, south of 40 ° S, including on the island of Chiloe. Andes - the birthplace of tomatoes, beans, pumpkins. Until now, the exact ancestral home has not been clarified and the wild ancestor of cultivated corn is unknown, but, undoubtedly, it comes from the Neotropical kingdom. South America is also home to the most valuable rubber - hevea, chocolate, cinchona, cassava and many other plants grown in the tropical regions of the Earth. The richest vegetation of South America is an inexhaustible source of enormous natural wealth - food, fodder, industrial, medicinal plants.

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 size of the territory they occupy.

Humid tropical (equatorial) forests of South America on ferrallitic soils, named by A. Humboldt hylaea, and in Brazil called selva, occupy a significant part of the Amazonian lowland, adjacent areas of the Orinok lowland and the slopes of the Brazilian and Guiana highlands. They are also characteristic of the coastal strip of the Pacific Ocean within Colombia and Ecuador. Thus, tropical rain forests cover areas with an equatorial climate, but, in addition, they grow on the slopes of the Brazilian and Guiana highlands facing the Atlantic Ocean, in higher latitudes, where there are abundant trade winds for most of the year, and in during a short dry period, the lack of rain is compensated by high humidity.

The hylaea of ​​South America is the richest type of vegetation on the Earth in terms of species composition and density of vegetation cover. They are characterized by high height and complexity of the forest canopy. In areas not flooded by rivers in the forest, there are up to five tiers of various plants, of which at least three tiers consist of trees. The height of the highest of them reaches 60-80 m.

Species richness in the hylaea of ​​South America is huge, more than 300000 plant species are endemic. In this respect, they are superior to the tropical rainforests of Africa and even Southeast Asia. The upper tiers of these forests are formed by palm trees, for example, Mauritia aculeata, Mauritia armata, Attalea funifera, as well as various representatives of the legume family. Of the typical American trees, Bertolettia excelsa, which produces nuts with a high fat content, mahogany tree with valuable wood, etc., should be mentioned.

The South American rainforest is characterized by chocolate tree species with caulifloral flowers and fruits sitting right on the trunk.

The fruits of the cultivated chocolate tree (Theobroma cacao), rich in valuable nutritious tonic substances, provide the raw material for making chocolate. These forests are the birthplace of the Hevea rubber (Hevea brasiliensis) (Fig. 85).

Rice. 85. Distribution of some plants in South America

Found in the tropical forests of South America symbiosis some trees and ants, such as several species of cecrops (Cecropia peltata, Cecropia adenopus).

The tropical rainforests of South America are particularly rich in creepers and epiphytes, often brightly and beautifully blooming. Among them are representatives of the family of arroinaceae, bromeliads, ferns and orchid flowers, unique in their beauty and brightness. Tropical rainforests rise up the slopes of the mountains up to about 1000-1500 m without undergoing significant changes.

The world's largest array of virgin forests existed in the north of the Amazon basin and on the Guiana Plateau.

However soil under this richest plant community in terms of volume of organic mass, they are thin and poor in nutrients. Decay products, continuously coming to the ground, quickly decompose in a uniformly hot and humid climate and are immediately absorbed by plants without having time to accumulate in the soil. After clearing the forest, the soil cover quickly degrades, and large amounts of fertilizers are required for agricultural use.

As the climate changes, i.e. with the advent of the dry season, tropical rainforests are moving into savannas And tropical woodlands. In the Brazilian Highlands, between the savannahs and the tropical rainforest, there is a strip of almost pure palm forests. Savannahs are common in a large part of the Brazilian Highlands, mainly in its interior regions. In addition, they occupy large areas in the Orinok Lowland and in the central regions of the Guiana Highlands. In Brazil, typical savannahs on red ferralite soils are known as campos. Their herbaceous vegetation consists of high grasses of the genera Paspalum, Andropogon, Aristida, as well as representatives of the legume and Compositae families. Woody forms of vegetation are either completely absent, or are found in the form of individual specimens of mimosa with an umbrella-shaped crown, tree-like cacti, spurges and other xerophytes and succulents.

In the dry 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 on red-brown soils. Many of them lose their leaves during the dry period of the year, others have a swollen trunk in which moisture accumulates, for example, the cottonwort (Cavanillesia platanifolia). The trunks and branches of Caatinga trees are often covered with creepers and epiphytic plants. There are also several types of palm trees. The most remarkable caatinga tree is the carnauba wax palm (Copernicia prunifera), which produces vegetable wax, which is scraped or boiled from its large (up to 2 m long) leaves. Wax is used for making candles, rubbing floors and other purposes. Sago and palm flour are obtained from the upper part of the carnauba trunk, the leaves are used to cover roofs and weave various products, the roots are used in medicine, and the local population uses the fruits in raw and boiled form. No wonder the people of Brazil call carnauba the tree of life.

On the Gran Chaco plain, in especially arid regions, on brown-red soils, thickets of thorny bushes And sparse forests. In their composition, two species belong to different families, they are known under the common name "quebracho" ("break the ax"). These trees contain a large amount of tannins: red quebracho (Schinopsis Lorentzii) - up to 25%, white quebracho (Aspidosperma quebracho blanco) - somewhat less. Their wood is heavy, dense, does not rot and sinks in water. Quebracho is heavily cut down. At special factories, tanning extract is obtained from it, sleepers, piles and other items are made from wood, designed for a long stay in water. Algarrobo (Prosopis juliflora) is also found in the forests - a tree from the mimosa family with a twisted trunk and a strongly branching spreading crown. The fine, delicate foliage of the algarrobo leaves no shade. The low tiers of the forest are often represented by thorny shrubs that form impenetrable thickets.

Northern hemisphere savannahs differ from southern savannahs in appearance and species composition of the flora. To the south of the equator, among the thickets of cereals and dicotyledons, palm trees rise: Copernicia (Copernicia spp.) - in drier places, winding Mauritia (Mauritia flexuosa) - in swampy or flooded areas. The wood of these palms is used as a building material, the leaves are used for weaving various products, the fruits and core of the Mauritia trunk are edible. Acacias and tall tree cacti are also numerous.

Red and red-brown soil savannahs and tropical woodlands are characterized by a higher humus content and greater fertility than the soils of moist forests. Therefore, in the areas of their distribution are the main areas of plowed land with plantations of coffee trees, cotton, bananas and other cultivated plants exported from Africa.

pacific coast between 5 and 27° S and the Atacama Basin, with their constant lack of rain, have the most typical desert soils and vegetation in South America. Plots of almost barren stony soils alternate with massifs of free-flowing sands and vast surfaces occupied by saltpeter solonchaks. Extremely sparse vegetation is represented by sparsely standing cacti, thorny cushion-like shrubs and ephemera of bulbous and tuberous plants.

subtropical vegetation occupies relatively small areas in South America.

The extreme southeast of the Brazilian Highlands, which receives abundant rainfall throughout the year, is covered subtropical forests from araucaria with an undergrowth of various shrubs, including Paraguayan tea (Ilex paraguaiensis). Paraguayan tea leaves are used by the local population to make a widespread hot drink that replaces tea. According to the name of the round vessel in which this drink is made, it is called mate or yerba mate.

The second type of subtropical vegetation of South America is subtropical steppe, or pampas, characteristic of the eastern, most humid parts of the La Plata lowland south of 30 ° S, is a 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 steppes of the temperate zone (feather grass, bearded vulture, fescue). The pampa is connected with the forests of the Brazilian Highlands by a transitional type of vegetation, close to the forest-steppe, where grasses are combined with thickets of evergreen shrubs. The vegetation of the pampas has been the most severely destroyed and is now almost completely replaced by crops of wheat and other cultivated plants. To the west and south, as precipitation decreases, vegetation of dry subtropical steppes and semi-deserts appears on gray-brown soils and gray soils with spots of salt marshes in place of dried lakes.

The subtropical vegetation and soils of the Pacific coast are similar in appearance to the vegetation and soils of the European mediterranean. Thickets of evergreen shrubs on brown soils predominate.

The extreme southeast (Patagonia) is characterized by vegetation dry steppes and semi-deserts of the temperate zone. Gray-brown soils predominate, salinization is widespread. The vegetation cover is dominated by tall grasses (Roa flabellata, etc.) and various xerophytic shrubs, often pillow-shaped, undersized cacti.

In the extreme southwest of the mainland, with its oceanic climate, insignificant annual temperature differences and an abundance of precipitation, moisture-loving evergreen subantarctic forests, multi-tiered and very diverse in composition. They are close to tropical forests in the richness and diversity of plant life forms and the complexity of the forest canopy structure. They abound with vines, mosses, lichens. Along with various tall coniferous trees of the genera Fitzroya, Araucaria and others, evergreen deciduous species are common, for example, southern beeches (Nothofagus spp.), Magnolia, etc. There are many ferns and bamboos in the undergrowth. These moisture-soaked forests are difficult to clear and uproot. They are still one of the most important natural resources Chile, though heavily affected by logging and fires. Almost without changing their composition, the forests rise along the slopes of the mountains to a height of 2000 m. Forest burozems develop under these forests. To the south, as it gets colder, the forests become depleted, creepers, tree ferns and bamboo disappear. Conifers (Podocarpus andinus, Austrocedrus chilensis) predominate, but evergreen beeches and magnolias remain. Beneath these depleted subantarctic forests, podzolic soils form.

Determinants overall structure soil cover of the continent……………………………………………………………..………2-4

Soil-geographical zoning of South and Central America……………………………………………………………………………..5

Soil cover of equatorial and tropical humid forest areas………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………6-19

Soil cover of savanna-xerophyte-forest areas……………...20-27

South American meadow-steppe sector……………………………28-34

Southern Pacific subboreal forest sector……………...35-36

Agricultural use of the soils of South America. Agricultural crops……………………………………..……… 37

Bibliography…………………………………………………...……… ..38

FACTORS DETERMINING THE GENERAL STRUCTURE OF THE SOIL COVER OF THE CONTINENT

The general nature of the soil cover of South America is determined by: the significant length of the continent in the meridional direction; the presence of a mountain barrier along the western coasts; the predominance in the equatorial, tropical and subtropical zones of the eastern transfer of moisture from the Atlantic Ocean, the presence of the cold Peruvian Current along the Pacific coast; the predominance of the western transport of moisture in the temperate zone of South America and the presence of the cold Falkland current along the coasts of Patagonia; distribution in the equatorial and tropical belts of ancient leveling surfaces with a thick ferralitic, often strongly lateritized weathering crust; distribution in the subtropical part of the continent of alluvial plains; the presence of active volcanoes and associated volcanogenic sediments in the northern and southern Andes.

South America is the only continent in the southern hemisphere that extends into the temperate and cold temperate zones. Five geographical zones cross it: northern tropical, equatorial, southern tropical, subtropical and temperate. The largest and widest part of the continent lies in the equatorial-tropical latitudes.

The continent is protected from the west by the high barrier of the Andes, which, along with the direction of humid air masses, determines the nature of the moistening of the adjacent plains. The latter is especially pronounced in the south of the continent, where the western transfer of air masses predominates. The western slopes of the Andes in southern Chile receive 2000-5000mm precipitation, and Patagonia lying in the rain shadow - 150-250mm. The arid climate of Patagonia is aggravated by the presence of the cold Falkland Current along the Atlantic coast. Therefore, the plains of the temperate zone of South America, regardless of the fact that they lie in the eastern oceanic sector, are dominated by landscapes and soils of desert steppes and deserts.

In the subtropical zone, on the contrary, the eastern transfer of moisture from the Atlantic Ocean and the maximum amount of precipitation (1000-2000mm) falls on the east coast; inside the continent, as the sea air masses transform, the amount of precipitation decreases to 300-400mm. These are the arid regions of the inner Pampas and the province of Gran Chaco. The meridional stretch of the humidification zones determines the same direction of the landscape and soil zones: in the north of the eastern most humid part, there are subtropical moist forests on red soils and tall-grass prairies on chernozem-like soils; in the more inland regions of the dry pampas there are subtropical chernozems, and in the Andean part, in the Gran Chaco, there are subtropical dry and desert steppes on gray-brown soils in combination with solonetzes and solonchaks.

The Pacific coast and the western slopes of the Andes in the subtropical and tropical zones receive the minimum amount of precipitation, as they are under the influence of cold southeastern and southern air masses coming from the eastern periphery of the Pacific anticyclone. The dryness is exacerbated by the cold Peruvian current running along the western coasts of the continent. Desert landscapes and soils dominate here with pronounced phenomena of salt accumulation both on the low coasts and on the high uplands. Only to the north of the equator are the western slopes of the Andes moistened more than the eastern ones, due to the bringing of moisture from the Pacific Ocean by southwesterly winds.

In the equatorial zone, on the plains in the river basin. The Amazons, lying east of the Andes and receiving moisture from the Atlantic Ocean, the climate is the most humid, precipitation from 2000 to 5000mm, no significant dry period. Moist equatorial tropical forests on yellow ferralite soils predominate. To the north and south, somewhat asymmetrically with respect to the equator, are tropical regions, where 2000-1000mm rainfall and a dry period lasting from 3 to 5 months. These are zones of seasonally humid tropical forests and savannahs on red ferrallitic and alferritic soils, no less poor than the soils of permanently humid forests; they are associated in their distribution with the ancient ferrallitic weathering crust covering most of the surface of the Brazilian and Guiana highlands.

On the inland, arid plateaus somewhat isolated from the Atlantic Ocean, in the northeastern part of the Brazilian Highlands, the climate is drier, which is the reason for the appearance of xerophytic shrubs and light forests on red-brown and red-brown soils.

On the whole, in the equatorial and tropical zones, the humidification zones coincide with the direction of the thermal belts; therefore, the latitudinal zonality of landscapes and soils is expressed in this part of the continent.

The extensive alluvial plains of the Amazon and Parana river basins are associated with the distribution of modern superaquatic and paleohydrogenous landscapes and soils.

A series of mountainous soil zones are associated with the mountain ranges and uplands of the Andes, which are significantly different in the northern, central, and southern Andes.

SOIL GEOGRAPHICAL ZONING OF SOUTH AND CENTRAL AMERICA

There are seven soil sectors in the territory under consideration: the Equatorial Pacific Oceanic humid forest, the Equatorial American–African humid forest, the Southern Atlantic humid forest, the American–African savanna–xerophyte–forest, the South American meadow–steppe, the Andean–Patagonian desert, and the Southern Pacific subboreal forest. Some sectors are closed within the continent and have a small extent.

Some sectors continue in Africa and form "bridges" between the two continents. The mountainous volcanic regions of Central America and the northern Andes are part of the Equatorial Pacific humid forest sector, which includes Malaysia and New Guinea. The Southern Pacific Forest Sector links Southern Chile with New Zealand.

According to the nature of the macrostructure of the soil cover, a number of soil areas are distinguished:

1) mountainous areas of the Andean belt, with a combination of mountain zonal bioclimatogenic and volcanogenic macrostructures: Central American, Equatorial Andean, Central Andean, Chilean-Ognezemelskaya;

2) areas where a combination of elements of plain and mountain zonal bioclimatogenic structures with paleoclimatogenic and disordered lithogenic structures is observed: Caribbean, Central Brazilian, East Brazilian, Atlantic;

3) areas where plain-zonal bioclimatogenic macrostructures are combined with paleohydrogenic and modern hydrogenic ones: Amazonian, Eastern Pampa region;

4) the areas of predominance of bioclimatogenic are plain-zonalxstructures: Paraguayan-Predandian, South Argentinean-Patagonian.

SOIL COVER IN EQUATORIAL AND TROPICAL MOISTURE FOREST AREAS

South America includes, in part or in full, three humid forest sectors: the Equatorial Pacific, the Equatorial American-African, and the South Atlantic. The equatorial Pacific sector is represented by two mountainous regions: Central American and Equatorial Andean; Equatorial American-African sector - one large Amazonian region, including several soil districts; The southern Atlantic sector - the Atlantic.

Central American soil region

The narrow strip of land in Central America is characterized by a significant variety of bioclimatic and lithological-geomorphological conditions and, accordingly, soils.

According to the nature of the relief, this territory is divided into the eastern low-plain part and the western - mountainous. The highest mountain ranges of the Southern Sierra Madre and Eastern (volcanic) Sierra Madre, stretching along the coasts of the Pacific Ocean, rise to abs. high 3700-3800 l, and at the highest points exceed 4200-4500m.

The mountain ranges of Central America are composed of a complex of various Cretaceous and Paleogene sedimentary rocks, among which limestones occupy a significant place. According to the nature and structure of the soil cover, the Central American region is divided into two sub-regions: the western mountainous and the eastern mountainous-plain. The western mountainous sub-region includes the mountain ranges named above and the high plateaus of the Mexican Central Mesa, lying at 2000-2500m.

The composition and structure of the soil cover in this area are significantly different on the windward, wet, and leeward drier mountain slopes and on high intermountain plateaus.

The southwestern slopes of the Southern Sierra Madre and the eastern slopes of the Eastern Sierra Madre, covered with deciduous tropical forests, humid mixed forests and occupied by red ferrallitic tropical soils, and dark red ferrallitic soils on the rocks of the main composition, are the most moistened.

Eastern (Volcanic) Sierra Madre is a country of modern grandiose active volcanoes; the largest of them are Colima, Popocatepetl, Orizaba. Volcanic ash covers mountain slopes and highlands, basaltic lava flows and volcanic mudstone flows fill intermountain depressions. Water-soluble products of volcanic eruptions, chlorides, sulfates are removed and accumulated in local relief depressions - basins filled with lacustrine deposits. The snow line in the Eastern (Volcanic) Sierra Madre is at an altitude of 4500m. The upper vertical zone is formed by subalpine and alpine mountain meadow soils.

On better moistened mountain slopes under forest vegetation, the soils are similar to red and yellow soils. Within the Central Mesa and on the highlands in the river basin. Balsac, dark-colored soils on volcanic ash and weathering products of basic lavas are widespread. These soils contain about 5% humus, slightly acidic, neutral or slightly alkaline in the upper part, slightly clayey in the lower part of the profile, in some places with a carbonate accumulation horizon. Solonchakous dark-colored meadow soils and solonchaks of sulfate-chloride-soda and soda composition appear in local relief depressions (Gerasimov, 1968). The natural vegetation of the highlands is represented by a grassy savanna dominated by Gramme grass and aristids with acacias, cacti and agaves in the tree layer.

Central Mesa is the most populated and used agricultural region in Mexico.

The eastern mountain-plain subregion of the Central American soil region has a more humid climate. Dry periods are not expressed here, forest vegetation dominates everywhere: on the plains - tropical rainforests, on the mountain slopes - mixed, with tree ferns. Both on the plains and in the mountains, powerful ferrallitic weathering crusts with red-yellow and yellow ferrallitic soils are everywhere developed. In the higher belt of mountains, high-humus mountain ferralitic and allitic soils appear. Above 3800m - zone of acidic peaty mountain-meadow soils.

On the Yucatan Peninsula, composed of limestones, dark red ferralitic soils are more saturated and richer in humus than the rest of the soils of the piedmont plains. With a close occurrence of limestones, red-brown soils saturated with bases are formed on its eluvium. Here the slopes are terraced in places - these are traces of the ancient agricultural culture of the Mayan Indian tribe.

The coastal lowlands are occupied by groundwater sandy lateritic and bog soils, moving with sandy illuvial-ferruginous-humus podzols.

The very low economic level of development of the countries of Central America does not allow the use of even the best lands of this vast territory.

Equatorial Andean soil region

This predominantly mountainous region includes a system of mountain ranges that converge near the equator and fan out to the north. Mountains rise above 5000m; the highest peaks are volcanoes. In some places, for example, in the Eastern Cordillera, there are extensive leveled surfaces lying on the abs. high 2500-3000m. Most of the leveled surfaces are covered with thick layers of volcanic ash. There are a number of active or recently extinct volcanoes. In Ecuador, most soils, even on steep slopes, are developed on volcanic ash. They got the name "Andosols". These soils have a thick humus dark horizon, with interlayers of ash turning deeper into brownish or reddish-yellow.

Andosols are characterized by: allophane composition of the clay fraction, high absorption capacity, ability to absorb not only cations, but also anions, in particularPO4, a large number of movable Al, very low bulk density due to the porosity of volcanic glass. In a humid climate, Andosols are a stable type, especially with the periodic supply of new volcanic material.

On the plateaus of the Eastern Cordillera, at altitudes of 2200-I 3200 m near the capital of Colombia - Bogota, in a temperate warm climate, with average monthly temperatures of about 14-I16 ° C, corn, wheat, beans, potatoes are grown on Andosols.

Above 3200-3500 and up to abs. you. 4000m there is a “paramo” belt of high-mountain subalpine and alpine shrub-herbaceous vegetation. Dark-colored mountain-meadow soils with a coarse-humus and powerful humus horizon are common here. A colder climate, and most importantly, sharp fluctuations in daily temperatures prevent the cultivation of crops, these territories are used as pastures. On the flat surfaces of the plateau, large areas are swampy.

On the slopes of the mountains, where there is no significant accumulation of volcanic ash and falls from 3000 to 1000mm precipitation, there are a number of high-altitude zones.

Upper forest belt (tierra fria), located within 3000-2000m, represented by forests of fogs (nephelogilea). This belt is associated with mountainous brown and acidic multi-humus brown forest soils, podzolized in places. Middle forest belt (tierra-templad) - from 1000-1500 to 2000-2800m - this is a mountain gley, dominated by mountain humus allitic and mountain humus ferrallitic soils.

The lower belt of mountains and foothill plains (tierra caliente) is a special soil region extending from Guaiaquila in Ecuador to the Isthmus of Panama near the western slope of the Andes. In relief, it is an alternation of low coastal ridges and low foothills of the Andes, alluvial plains of river and sea terraces, estuaries and deltas with alluvial sediments and in places coastal sand dunes.

In the northern part of this belt, red-yellow ferralitic and red-yellow podzolic soils predominate, and podzols appear on well-drained sandy terraces. Hydromorphic, alluvial and saline soils are widespread on the coastal plain. In the central and southern parts of the territory, Andosols and accompanying alluvial and hydromorphic soils containing volcanic ash stretched in a narrow strip at the foot of the Andes. In the southern part, the soil cover is even more diverse: here, in the conditions of a hilly relief, somewhat more fertile soils are common, transitional between saturated brown forest and red-brown Mediterranean soils. Dark red ferrallitic soils are also widespread here, developing on ancient alluvium on terraces, with a high content of basic volcanic ash. The level of fertility and the need for fertilizers are very different here, and economic use is also very diverse. On the most fertile and well-drained soils on alluvium and on ash-volcanic soils (andosols), bananas and cocoa are grown, on less fertile soils, oil palm and fiber crops, on poor soils of heavy mechanical composition with poor drainage, rice. In places, in the conditions of a hilly relief, the shifting culture of agriculture has still been preserved, but it is gradually being replaced by cocoa or coffee plantations, although in some places it is unsafe due to steep slopes, thin soils and possible erosion. Plots of hydromorphic soils and black merged soils are used for pastures. Significant areas of fertile soils in river estuaries are underutilized due to salinity, close brackish water horizon and lack of capital flood protection.

Amazonian soil region

This area is the largest in South America, it covers one flat equatorial soil zone of yellow and red-yellow ferralitic soils of moist equatorial and tropical forests. It stretches across the entire continent - from the eastern foothills of the Andes to the Atlantic coast. The area includes the entire Amazonian lowland, the Guiana Highlands and the northern part of the Brazilian Highlands framing the lowland from the south. Throughout the region, the climate is humid, annual moisture is uniform, sometimes with one short somewhat drier period. The most heavily moistened is the western Predian part of the region and its extreme eastern Atlantic part, where the annual precipitation ranges from 2000 to 5000mm in year. The dominant vegetation in the Amazonian soil region is moist equatorial and subequatorial forests. The main background - the selva - is interspersed with small islands of grassy savannas confined to flat surfaces experiencing seasonal flooding by atmospheric waters.

The central part of the region - the Amazonian lowland itself, is widest in the western part and narrows towards the east.

From the north and south, the lowland is framed by ancient shields: the Guiana and Brazilian highlands. In large areas of uplifted plains, the surface mantle is represented by quartz sands; along with white quartz sands, pink and red sands are common, with ferruginous films on the surface of quartz grains, often with ferruginous concretions. These sands are erosion products of the ancient weathering crust of acidic quartz-bearing rocks.

The products of erosion and redeposition of the ancient weathering crust, including quartz sands, cover large areas within the Amazonian lowland.

Only in conditions of highly dissected relief, on surfaces renewed by erosion, less poor weathering products have a fersiallitic or fersiallite-allite character. In the Amazonian soil region, yellow and red-yellow ferralitic soils dominate. They differ mainly in the amount and degree of hydration of iron oxide hydrates: yellow ferralitic ones contain less iron oxides and it is more hydrated than in red-yellow ferralitic ones. Otherwise, they have similar properties.

These soils are formed on ferralitic weathering crust or products of its erosion and redeposition, which do not contain any primary minerals except quartz.

The humus content in the upper soil horizons is about 3.0%, humus penetrates deep along the profile; at a depth of 100cm its content is about 2%. The humus is very light and, as studies by IP Gerasimov and OA Chichagova (1964) have shown, it has a pronounced fulvate composition. The profile is morphologically weakly differentiated and includes horizons: humus (Af) - brownish or yellowish black, loose, 5-10cm. Beneath it is a powerful metamorphic mountain. IN T - yellow-brown or red-brown, loose, well aggregated, riddled with termite passages, well air and water permeable, without noticeable signs of silt particles being washed into it. At a depth of 100-150cm the color becomes brighter - red or orange. The low content of humus, low absorption capacity, lack of primary minerals - the source of bases, low content of phosphorus, nitrogen and trace elements cause very low fertility of these soils and limit their use in agriculture.

Along with yellow and red-yellow ferralitic soils, other zonal types are also common in this zone, the nature of which is closely related to the composition of parent rocks and the stage of development of the relief.

Where ancient planation surfaces have been severely dissected, for example, in the Guiana Highlands, and the ancient weathering crust has been washed away, the weathering products of massive rocks appear somewhat more fertile compared to red-yellow ferrallitic soils. Dark red ferrallitic soils are formed, with a higher content of humus, a well-defined structure, a high content of iron oxides, less acidic. Groundwater laterites, soils with horizons of ferruginous concretions forming solid ferruginous slabs, are common in relief depressions with close occurrence of groundwater.

Differences in relief and soil-forming rocks lead to differentiation of the soil cover within the region and make it possible to distinguish a number of soil districts: the Amazonian lowland, the Guianan, the Brazilian, and the Atlantic.

Amazonian lowland soil district yellow ferralitic, groundwater lateritic, marsh soils and sandy podzols. This territory lies on abs. altitude below 200m and is an alluvial plain with wide terraces and wide river valleys. The degree of dissection of the relief is small, with the exception of the territories adjacent to the Brazilian Highlands. Most of the territory is covered with tropical rainforest, with small patches of grassy savannah confined to flat, poorly drained surfaces.

The soils of this district are predominantly yellow ferralitic, with a low content of iron oxides, very acidic, highly unsaturated, and often light in texture. Poor groundwater lateritic soils with accompanying hydromorphic soils are widespread. These soils are of low natural fertility. Somewhat more fertile soils are found in small massifs in places where loose deposits contain weathering products of basic rocks and limestones.

A significant part of the territory is occupied by soils on young alluvium. These are peaty-bog and humus-bog soils. Low terraces composed of quartz sandy material are occupied by very poor, acidic sandy soils.

A large amount of incoming organic residues and a high mobility of humus (mainly its fulvate composition) determine the formation of thick illuvial-humus podzols on sandy terraces, often with signs of soil moisture. The waters of many rivers and streams in the Amazon basin are so rich organic matter that have dark color. In some places on high terraces they occur in the form of small, slightly elevated patches of black, relatively fertile soils. This "terrapreta"- cultural soils created during long-term agricultural cultivation by Indian tribes and currently abandoned, but have not lost the fertility created by labor. Their dark color is due to the large number of inclusions of charcoal.

Large areas on yellow ferrallitic and ferruginous-concretional (lateritized) ferrallitic soils and well-drained alluvial soils are occupied by rubber plantations; tobacco and some fiber crops are also confined to sandy ferrallitic soils.

Guiana Upland Soil District red-yellow ferrallitic and red-yellow fersiallitic podzolized soils, laterites and thin stony soils of mountain slopes.

The territory, an isolated northern section of the Brazilian Shield, has a hilly and mountainous topography, with several levels of ancient denudation surfaces well preserved from erosion and with several younger surfaces forming lower steps. Absolute altitudes in this area range from 0 to 1500m, and individual table heights reach 2000m. The natural vegetation is tropical rainforests, and on the young Denudation surfaces (Ruppini area) grassy savannahs. Small islands of herbaceous vegetation interspersed with forests, most of them of anthropogenic origin.Red-yellow ferrallitic, ferrsiallitic and podzolic soils of the region are developed on sloping and steep slopes, respectively on mudstones, siltstones and quartz sandstones. Dark red (reddish-brown) ferralitic soils occur on the main igneous rocks and their deluvium. These soils are highly valued by Indian farmers.

In the mountains, there are small areas with a relatively leveled relief, where ferrallitic soils are widespread with a high content of ferruginous nodules. Poor ground-water laterites, quartz-sandy acidic soils on pink and white sands are common on ancient denudation surfaces, some of which (especially the highest ones) have thick ancient horizons of true laterites. Thin stony soils are quite widespread in this area. Pastoralism is developed on unimproved pastures in areas of grassy savannahs, and on the slopes of mountain valleys there are small areas of shifting agriculture.

Brazilian Upland Soil District red-yellow and dark red ferralitic soils and quartz-sandy soils.

This area has a predominantly humid climate, with a short dry season; heavily forested. Absolute altitudes range from 200 to 1000m. The relief is predominantly hilly plateaus, with wide summit surfaces inclined to the north. The soils of the district are poorly studied. According to a few observations, red-yellow and dark red ferralitic soils are found here on the weathering products of shales and phyllites. On slightly undulating surfaces of uplands composed of sandstones, quartz-sandy acidic soils (quartz regosols) are widespread. In hilly areas, red-yellow podzolic soils form. In depressions, on loose sediments, the formation of yellow ferralitic soils is possible. Agricultural development of this territory is very weak; it is crossed by only one road. Some rivers are navigable. The mode of transportation is pedestrian or air. The indigenous population is very rare, mainly engaged in the collection of natural fruits and plants and hunting, and only in some places conducts shifting agriculture to obtain the main food crop - cassava.

Soils have a very low level of fertility; if they are used over large areas, there is a danger of erosion, especially of red-yellow podzolic soils on slopes. Soils need regular fertilization if used consistently.

Atlantic Soil District seaside acidic solonchak, marsh and sandy soils.

Most of the Primorskaya Lowland lies at altitudes of less than 50m above ur. seas; the groundwater level is high, the waters are often saline; the coast is very gentle, in many places with a strip of marches and mangrove forests. The coastal zone is built up by sediment carried by rivers, especially the Amazon and Orinoco. The climate is tropical. Natural vegetation is closely related to the nature of soils. There are mangrove swamp forests withAvicenna And Rhizophora , reed (reed) swamps, tropical forests and savannahs with rare xerophytic shrubs.

Hydromorphic soils that develop on Holocene sediments and marine sediments predominate: silt-gley, mineral gley, and coastal saline soils. These soils contain minerals of the illite-montmorillonite group, which significantly distinguishes them from most other soils of the Amazon region, which have a kaolinite composition.

Acid sulfate soils with very low pH values ​​are a hallmark of the county. They are confined to relief elements where the water level periodically drops and oxidation of sulfides occurs, usually present in the restored undrained soils of the coasts. Acidic sulphate soils often contain a lot of mobile aluminum, which, like the high acidity of soils, makes them sterile for a number of years after drying. Most of the bog soils in the lower horizons are saline.

The belt of peaty bog soils is currently not used; their development is possible only under drainage conditions. The white and ferruginous sandy soils of the interior of the lowlands are rough pastures and forested areas. Silty-gley, mineral gley soils and coastal solonchaks of about. Marajos are occupied by good natural pastures, but they are not suitable for the cultivation of grain crops, except for some varieties of rice.

Most of the poor groundwater laterites are infertile, with many areas swampy or subject to periodic flooding. Cattle grazing on pastures with lateritic soils often suffer from a lack of minerals in the feed.

Atlantic moist forest soil region

The area is located between 5 and 23 ° S. sh. It covers the eastern most elevated, up to abs. high 800-2000m, the heavily dissected part of the Brazilian Highlands and its eastern slopes facing the Atlantic Ocean. This area is well hydrated. Two soil districts are distinguished here: Northeastern Brazilian and Southwestern Parano-Uruguay.

Northeast Brazilian Soil Region . The ground cover is dominated by very poor red-yellow, ferrallitic and red-yellow podzolic ferrallitic soils under tropical rainforests. At an altitude of about 2000m deciduous forests appear on humus ferrallitic acidic soils, and where the peaks reach 2100-2200m, forests disappear and are replaced by mountain peat bogs.

In the lower zone of humid tropical forests, among red-yellow ferralitic soils, somewhat more fertile dark red ferralitic soils are not uncommon, associated either with eluvium-deluvium of less acidic rocks, or with relatively dry areas where the degree of soil leaching decreases.

Alluvial and hydromorphic soils are widespread along the river valleys.

In the production of crops, this district occupies a special place, since it is located between two large cities: Rio de Janeiro and Sao Paulo. Various crops are grown here, and fertilization increases soil fertility. The remoteness makes it difficult for agricultural use of certain parts of the district, and they are occupied by natural forests. In a number of districts of the district, arable land has been abandoned due to a decline in fertility and the development of soil erosion. Soil erosion, especially of red-yellow podzolic soils, is a factor limiting the development of agriculture. These soils have a compacted horizon of poor water permeability and a less stable structure.

The soils of the river valleys were previously poorly developed due to flooding and the lack of drainage systems. In connection with the development of agricultural technology, their importance is increasing and they are currently used in agriculture and horticulture.

At the foot of the mountains stretches a narrow strip of the Atlantic coastal lowland, in some places it expands to 50km. Absolute heights range from 0 to 350m. Several geomorphological levels and associated soil combinations are distinguished here:

1) low-lying accumulative surfaces with a close level of groundwater are occupied by soddy and humus-gley low-humus gley and alluvial soils, which are often combined with well-drained soils of low hills;

2) ancient elevated sea terraces, in some places significantly dissected, in the northern part of the coastal lowland of the state of Rio de Janeiro, Espirito Santo, South Bahia and in places in Pernambuco are occupied by kaolinite yellow ferrallitic soils, very reminiscent of the soils of the Amazon basin. In the northern part of the district, on terraces, there are also poor red-yellow podzolic soils, highly unsaturated, which are transitional formations to ground-water lateritic soils and, in some places, to podzols;

3) low-hilly relief, worked out in igneous rocks and less often in clay shales, is characterized by poor red-yellow podzolic soils, in some places somewhat more saturated bases. The latter are widely used for a variety of tropical crops.

Southwestern Parano-Uruguay Soil District is located within the basalt plateau, the highest parts of which lie at an altitude of 1500m.

Low plateaus are occupied by coniferous-deciduous subtropical forests; coniferous araucaria forests dominate on high plateaus( Araucaria angustifolia ); with patches of tall grass prairie. Under the coniferous forests there are dark brown ferralitic and fersiallite soils, acidic, highly unsaturated, with a high content of absorbed aluminum, and a powerful humus horizon. Under grassy vegetation, reddish-black soils of the subtropical prairies are developed "rubrozems", as they were called by Simonson and Bromao (Simonson, Bromao).

At altitudes between 400-800m under coniferous and mixed forests and areas of prairies, dark red ferrallitic and fersiallitic soils are common on the weathering products of basalts. They are less acidic and have a higher absorption capacity than typical dark red ferrallitic soils.

In relatively drier valleys open to the west, soils of siallitic composition appear, similar to red-brown "Mediterranean"; they are more saturated, have clayey metamorphic and well-developed humus horizons. This gives them a similarity to the reddish-black soils of the prairies as well.

Poor podzolized red and yellow soils appear on acidic rocks, especially sandstones.

The agricultural use of soils is complicated by the very strong manifestation of erosion processes; and most of the territory is occupied by grazing and forest lands. In the drier valleys there are vineyards, tobacco plantations and soybean crops.

SOIL COVER OF SAVAN-XEROPHYTIC FOREST AREAS

South America includes the northern and southern branches of the horseshoe-shaped American-African savanna-xerophyte-forest sector. The northern branch includes one Carnbian soil region, the southern branch, covering the Brazilian Highlands and the Pre-Andean plains in the subtropical zone of the continent, includes three soil regions: Central Brazilian, East Brazilian and Paraguayan-Pre-Andean.

Caribbean soil region

The region occupies the northern subequatorial part of the continent - the Llanos-Orinoco plains, mountain ranges and the Greater and Lesser Antilles.

The plains are dominated by savannah and xerophyte-forest type of vegetation, which is replaced by treeless grassy groups in the lowlands, which experience periodic flooding.

Three soil districts are distinguished in the continental part of the region: the Llanos-Orinoco, the Northeastern and Caribbean Andes, and the Caribbean Lowland.

District of Llanos Orinoco is a vast treeless area covered with grassy and palm savannahs, located between the Guiana Highlands and the Caribbean Andes and encompassing the Orinoco basin. According to the nature of the relief and soil cover, the district is divided into two parts: the western lowland and the eastern elevated. Western Llanos - flat alluvial plain with abs. you. about 50m. Bog and waterlogged soils of varying degrees predominate here, groundwater laterites are widespread. The most elevated and relatively dry areas are occupied by very poor red-yellow ferralitic, often strongly lateritized soils. Agriculture is not developed, the territory is used as pasture.

Eastern Llanos - elevated plains lying on the abs. you. 200-300m, dissected by erosion into separate table remains - mezas, on the surface of which a lyinginsituferrallitic weathering crust.

Very poor red ferrallitic soils are located on the surface of the remnant hills on the ancient ferralitic weathering crust. At the outcrops of carbonate rocks, less acidic, often calcium-saturated, red-brown fersiallite soils appear. In places, poor quartz sandy soils are common. The area is used as pasture. In places, wind erosion of soils is highly developed.

Mountain District of the Northeast and Caribbean Andes receives a large amount of rainfall and is covered with forests; lower mountain belt up to a height of 1000-1500m occupied by mountain xerophyte forests on red fersiallite and red-brown soils. The higher belt is formed by mesophytic forests and tropical mountain forests on mountain red-yellow and red fersiallitic and ferrallitic humus soils. At altitudes 2500m and above, there are mountain moist forests of the cold belt on acidic mountain polyhumus brown forest soils. Soils are common in dry intermountain valleys. Soils of mountain slopes and valleys are mainly used in the mesophytic forest belt for coffee plantations. At lower levels along the terraces of the rivers are cocoa plantations.

District of the Caribbean Lowlands the northern part of Venezuela and Colombia is occupied by red ferralitic and ferritic soils of seasonally humid tropical forests and savannahs and red-brown soils of dry light forests. Large spaces in the Maracaibo depression and on the alluvial plains of the river. Magdalen is occupied by marsh soils. In many soils of the district there is a significant admixture of volcanic ash. These soils stand out more high level fertility.

The islands of the West Indies have an equally complex and variegated soil cover, which is due to the structure of the relief (many islands are mountainous) and the variety of soil-forming rocks.

The influence of rocks on the nature of the soils of Cuba has been studied in detail by SV Zonn. Sedimentary rocks are predominantly distributed on the island: Cretaceous and Jurassic limestones, sandstones, shales, Tertiary limestones and marls, in places ultrabasic igneous rocks - serpentinites. The ancient weathering crust has been washed away in most of the territory. The products of its erosion, mixed with less weathered deluvium of rocks of different composition, compose a mantle of deluvial and alluvial Quaternary deposits on piedmont plumes and coastal plains. In some places on the plains, montmorillonite clays are common, in places carbonate and containing sulfates.

The wide development of limestones and serpentinites significantly affects the nature of the soil cover. The weathering products of these rocks are associated with slightly acidic or neutral clay red ferrallitic soils. These most fertile soils are widely used in agriculture, especially for the cultivation of sugar cane.

Red ferrallitic acidic soils are associated with gneisses, ferruginous sandstones, and marbled, quartz-bearing limestones.

Marl weathering products are associated with dark-colored humus calcareous soils effervescent from the surface - an analogue of humus-calcareous soils, or "rendzin". These soils are heavily clayed. In some places, they acquire the features of brown soils of dry forests and shrubs, characteristic of dry subtropics.

On the plains, the soil cover is also very diverse. Dark-colored merged soils (slitozems) are associated with montmorillonite clays. The composition of humus is dominated by humic acids. Slithozems are among the most fertile soils of the plains and are widely used in agriculture, mainly for the cultivation of sugar cane.

Clay plains are interspersed with sandy quartz sands formed from the surface, underlain at a shallow depth by heavier deposits, and in some places by dense rocks. Their formation is associated with the weathering products of acidic quartz-containing rocks: gneisses, sandstones.

Central Brazilian soil region

The region covers the interior of the Brazilian Highlands. The soil cover of this area is poorly studied. The vegetation is represented by alternating two types of groupings: campos-serrados tree-shrub vegetation and open savannas - campos-limpos. Within the region there are patches of rainforest associated with river valleys and some isolated, often rocky, uplands.

Dominates the Brazilian highlands campos-serrados - xerophytic shrub savannah, with a sparse grassy cover of hard turf grasses and low trees and shrubs( curatella americana , Qualea grandiflora and etc.).

Significant areas here are covered with rewashed, very poor quartz sands.

The soils of the region are represented by the so-called "serra-do phase" - red and dark red ferrallitic soils of both light and heavy mechanical composition. Another widespread group is formed by red and yellow acidic sandy soils.

The red ferrallitic soils of the savannas of the Brazilian Highlands are very similar to the red-yellow soils of tropical forests. This is due to the specific composition of parent rocks - ferralitic weathering crusts. The differences from forest soils are: a brighter red color due to dehydration of iron oxide hydrates during dry periods, a lower content of humus, similar in composition to the humus of forest soils (fulvic acids predominate), and a slightly higher absorption capacity.

Red ferrallitic soils with ferruginous concretions are widespread in the northern part of the region. In many valleys, especially in the Bananal region, there are meadow gley soils, peaty bog and groundwater laterites. In the eastern part, there are thin stony soils at the outcrops of quartzites.

Low fertility limits the agricultural use of soils. Farming is mostly primitive: with inefficient introduction of only organic residues from the "cerrado" vegetation. To improve soil fertility, it is necessary not only to apply fertilizers, but also microelements, since plants here need zinc, boron, and sulfur.

The soils of the north-eastern part of the region - district are very poor and infertile.

Laterites and ferralitic soils with a large amount of ferruginous concretions are the most widespread here. Some of these nodular ferrallites and nodular red-yellow podzolic soils are confined to ancient denudation surfaces, on which red and yellow acidic sands (quartz regosols) are also quite common. Red-yellow ferralitic soils without ferruginous concretions are encountered in places.

The soils of the southern part of the Central Brazilian soil region are somewhat fertile.

The most common soils associated with the weathering products of basalts, sandstones and shales. Dark red ferralitic soils predominate (terraroxalegitima) in places of basalt outcrops. No less common are soils of the same color, but with a clayey illuvial-metamorphic horizon -ter­ raroxaestructurada, or reddish-brown ferralitic soils high degree saturation. They develop on younger surfaces, on traps. There are ferrallitic soils of medium mechanical composition on the weathering products of sandstones. Poorer red-yellow ferralitic soils form on gneisses, while red-yellow podzolic soils form on shales and sandstones. Most of the red-yellow podzolized soils are poor and contain little bases, but on gneisses and sandstones with carbonate cement they are richer in bases and, liketerraroxaestructurada, the most fertile soils of the region. There are massifs of acidic yellow and white sandy soils confined to ancient denudation surfaces with sandstone outcrops.

Land developed for agriculture is not permanent. Many of them, once cleared from under the forest, were used for coffee plantations, and then, as soil fertility decreased and due to lack of fertilizers, they were abandoned. Only on dark red ferrallitic soils and on some of the least poor red-yellow podzolic soils is it possible to obtain more stable crops of woody crops, such as coffee. The western part of the state of São Paulo and northern Parana is the main region for the cultivation of coffee, cotton, sugarcane, soybeans and citrus fruits in Brazil.

East Brazilian soil region

The region occupies a vast depression in the river basin. Sao Francisco in the northeastern part of the Brazilian Highlands, is outside the influence of humid equatorial air masses and is protected from the humid masses of the South Atlantic by a coastal rise. Most of the territory lies within 500m above ur. seas. The soil cover of this area is represented by combinations of relict highly alkaline poor ferralitic soils, which occupy parts of the plateau less affected by erosion, and soils corresponding to modern arid conditions. The latter in the eastern part of the region are developed on crystalline rocks and are represented mainly by red-brown soils. Soils of light mechanical composition are very widespread on the weathering products of sandstones. Sand dunes appear in places. Salt soils and dark-colored coalesced montmorillonite soils occur in relief depressions. In places, ancient lateritic crusts are exposed on the surface. In the eastern part of the region, on low river and sea terraces, subsoil laterites occur.

Lack of water is the main obstacle to agricultural development of the territory. Rare rains are torrential in nature, causing severe soil erosion on the slopes, flooding of rivers and streams. But following these short periods of flooding, the rivers dry up for a long period.

Paraguayan-Predandian soil region

This is the southernmost region of the savanna-xerophyte-forest sector, located between 16 and 38 ° S. sh. It is elongated in the meridional direction and occupies the internal dry plains and foothills of the eastern slopes of the Andes. Two soil-bioclimatic provinces are distinguished here: the northern one is of red-brown and brown solonetsous soils and solonchaks, and the southern one is of brown and gray-brown soils.

The province of red-brown, brown solonetzic and saline soils covers the Gran Chaco plain. The surface of the plain is slightly inclined from the foot of the Andes to the east. The plain is covered with proluvial-alluvial deposits of rivers composed of weakly weathered material. There are no ancient weathering crusts so typical of the Brazilian highlands and associated relict soils here.

The El Chaco plains are an area of ​​intracontinental accumulation of not only solid runoff products, but also readily soluble salts. On the piedmont plains, in an arid climate, salts accumulate in waters, sediments and soils. Salt lakes, often drying up and turning into vast salt marshes, are especially common in the center of the province. strong winds, characteristic of this territory, carry salts from the surface of solonchaks to the surrounding elevated relief elements.

The vegetation is represented by xerophytic thorny shrubs, with a large participation of cacti. In less arid "peripheral areas" patches of herbaceous vegetation occur.

The general solonetzization of soils is facilitated by the constant aeolian accumulation of sodium salts on the soil surface and the subsequent leaching of colloids saturated with sodium at the onset of the rainy period. Therefore, strongly saline brown soils dominate even on relatively elevated relief elements.

Much of the plain is used as seasonal pasture. Agriculture requires irrigation, relief planning, and melioration of solonetsous soils.

The province of brown and grey-brown soils occupies the western part of the inner dry pampas with xerophytic shrubs. The grass cover is dominated by grasses.

Soils of relatively light texture prevail here, formed on loess-like sandy loams, with a large admixture of volcanic glass.

Soils have dark brown humus mountains. A, with a humus content of 2-3%, a well-developed clayey mountain. They are saturated with bases, have a neutral and alkaline reaction. The content of humus varies depending on the mechanical composition, but in general the soils of the eastern part of the province are more humus and can be considered as brown soils, and the western part - less humus - as gray-brown soils. Solonets and solonetzic soils are common in the western part of the province.

The main disadvantage of these soils for agricultural use is the danger of wind erosion and lack of moisture.

SOUTH AMERICAN MEADOW-STEPPE SECTOR

soil area Eastern pampas

In South America, meadow steppes are confined to the eastern Atlantic part of the continent and are limited in their distribution by the subtropical zone. The meadow-steppe sector includes only one soil region of the Eastern Pampas: brunizems, hydromorphic chernozem-like soils, and meadow slitozems, covering the most well-moistened eastern regions of the Argentine-Uruguayan pampas. The region extends north and south from the mouth of the river. La Plata and is located between 31 and 39 ° S. sh. and 57-59° E. e. This is the largest array of the most fertile soils in South America.

Almost the entire territory is covered with Quaternary deposits of considerable thickness, represented by loess-like medium and heavy silty loams up to several hundred meters thick.

Soil-forming rocks are eolian loess-like and alluvial-lacustrine deposits. The mechanical composition of the deposits is the heaviest in the east, lighter in the west. As a rule, these sediments are carbonate and rich in easily decomposable minerals, like hornblende, pyroxene, plagioclase, and contain a lot of volcanic glass; volcanic material is brought by the eolian route from the Andes, where there are a number of large active volcanoes.

The vegetation of the pampas is grassy tall-grass meadow steppes.

Currently, natural vegetation has been destroyed in large areas. Wheat, corn, sunflower, forage crops are cultivated here: oats, barley, rye, alpha, potatoes. Unplowed areas are used as highly productive natural pastures.

By the nature of the relief, the pampas are undulating, poorly drained plains with closed saucer-shaped suffusion depressions. Along the river valleys, especially along Paraguay and La Plata, low-lying alluvial plains stretch, periodically flooded. The groundwater level is very close. Many soils of the low accumulative levels of the pampa retained in their profile signs of the previous superaqueous stage. One of the most striking relics of the former hydromorphic regime is dense calcareous horizons or, as Argentinean soil scientists call them, “tosca” horizons.

The predominant soil type on relatively elevated and better drained elements in the humid eastern pampas is prairie chernozem soils, or brunizems.

Argentine brunizems have dark brown (almost black) humus mountains. And with a capacity of 35-40cm, humus content 3.0--3.4% in the upper and about 2% in the lower part, loose, with a granular structure. Below is a transitional mountain. AB, dark, grayish-brown, with a well-defined nutty structure, the humus content is about 1.5%, its lower limit runs togo-70 cm. At a depth of 70-150 cm located metamorphic mountains. Carbonate horizon up to 150-170cm absent. The soils are very slightly acidic (pH 6.1-6.2) in the upper part of the profile and neutral or slightly alkaline (pH 7.2-7.5) in the lower part. The degree of soil saturation in the mountains. And about 88-85%, in the mountains. Vsh - 94%; absorption capacity 18-20mg-eq per 100 G; in the composition of the absorbed bases 60-70% calcium, about 25% magnesium and 5-10% potassium; absorbed sodium is about 1-2%. The content of silt in the soil layer is 18-23%, while in the soil-forming rock it is only 7-10%. Silty and sandy fractions are 60-70% composed of volcanic glass.

Soil formation is accompanied by intense intrasoil clay formation, which is facilitated by constant soil moisture, a warm climate, and an abundance of roots. Enhances biochemical weathering and susceptibility to weathering processes of the source material (consisting largely of volcanic dust),

Many brunizems, located on somewhat lowered surfaces, have heavily clayey mountains.B m twith a silt content of up to 40% with a content in the rock of 10-15%, and in the mountains. A - 18-25%. This horizon has a blocky-nutty structure, is plastic when wet, and hard when dry. Clay films are observed on the surface of structural units, indicating the process of washing out the silt from the mountains. A. Absorption capacity in the illuvial horizon increases to 30-35mg-eq, what he says (as well as physical properties) about the presence of montmorillonite. These soils are also slightly acidic, slightly unsaturated, carbonate-free, and do not contain noticeable amounts of absorbed sodium. It can be assumed that the montmorillonitization of these soils is associated with weathering under conditions of longer moisture stagnation and the addition of magnesium and silica with surface and groundwater.

In closed relief depressions, on poorly drained surfaces, on river terraces, real heavy clayey, fused dark-colored montmorillonite soils (slitozems) appear, often gleyed and containing carbonates in deep horizons. Here, in areas of wet meadows subject to periodic surface waterlogging, soils classified as “planosols” are common. According to morphological and chemical properties, Argentine planosols are meadow solods. Salt licks occur in places And solonetzes, large areas are occupied by meadow gley and meadow-marsh soils. To the north, due to the increasing dryness of the climate, the areas of meadow solonetzes and solonchaks increase.

Andean-Patagonian desert-steppe sector

The sector elongated meridionally crosses the southern half of the continent from the coasts of the Pacific to the coasts of the Atlantic Ocean. It stretches from tropical to temperate latitudes and includes territories that are very diverse in terms of the nature of the relief and the structure of the soil cover. The tropical part of the sector, facing the coasts of the Pacific Ocean, covers the desert and desert-steppe highlands of the central Andes.And coastal tropical deserts of PeruAnd northern part of Chile. In the subtropical zone, the sector under consideration includes the mountainous xerophyte-forest regions of central Chile and the desert-steppe and desert central regions of Argentina, lying east of the Andes. In the temperate zone, this sector includes the desert steppes and deserts of Patagonia, stretching east from the southern Andes to the Atlantic coast. This sector is divided into two large areas: foothill-plain, South Argentine-Patagonian and mountainous Central Andean.

Central Andean soil region

The region extends from 18 to 38°S. sh. and according to the types of structure of mountain zonality it is divided into two soil districts - Puno-Atakama and Subtropical Andean.

Puno-Atakama District high-mountain and foothill desert, desert-steppe and solonchak soils occupies the Central Andes proper between 18-30 ° S. sh. and represents one of the greatest mountain deserts in the world. Eastern Cordillera (Cordillera Real) with a height of over 6000m protects the territory from humid eastern air masses. Precipitation falls on the eastern slopes of the mountains, covered with forests and xerophytic light forests.

Strong winds blow the surface of the soil, blow out fine particles, therefore, in large areas, soils have a light mechanical composition and an undeveloped profile. The areas less affected by wind erosion are occupied by reddish-brown desert soils, often saline.

In eastern Pune, the amount of precipitation slightly increases, and here high-altitude cold steppes (khalka) appear on slightly more humus high-mountain steppe soils, with a large amount of volcanic ash.

The western frame of Pune is a chain of high, active and recently extinct volcanoes, rising to a height of 5800-6800m. Their peaks are covered with snow, but the slopes, composed of lavas, volcanic tuffs and mudstone (mudflow) deposits, are devoid of vegetation in most of the territory.

On the slopes of mountains at altitudes of 2500-3500m a meager cover of xerophytic shrubs and cacti appears. Stony, thin mountainous desert soils with an unformed profile predominate here. However, in areas less exposed to erosion and burial under ash, soils have a slightly differentiated profile, in which a small, somewhat more clayey horizon stands out under a loose porous crust. All soils are carbonate, in many soils the carbonate horizon is strongly cemented and acquires the character of a calcareous slab. In the river valleys, the soils are saline. The lower part of the western slopes of the mountains and the piedmont coastal plains are just as deserted. Precipitation here is highly irregular, but some soil moisture is obtained from night dews, as the cold Humboldt current along the coast contributes to the formation of fogs.

In large areas, the surface is completely devoid of vegetation and covered with a powerful crust of salts - sulfates, chlorides and sodium nitrates (Chilean saltpeter). Intensive salt accumulation on the piedmont plains is associated with the removal of water-soluble products emitted by volcanoes and their accumulation in an extra-arid climate. Agriculture is practiced only on small areas of alluvial soils along river terraces. Irrigation is difficult due to lack of water and irregular flow.

Subtropical Andean District mountain brown, red-brown And gray-brown soils is located between 30-38 ° S. sh., covers the Coastal Cordillera abs. you. up to 2300m, Main Cordillera up to 6000-6900m and the Longitudinal Valley between them. Rainfall in the north - 300-400mm, to the south increases to 800-1000mm.

In the Longitudinal Valley and the Coastal Cordillera, brown soils of dry forests and shrubs predominate, in places there are reddish-brown soils if they form on eroded ancient red-colored weathering crust. On the most well-moistened slopes of the mountains of the Main Cordillera, mountain brown forest soils appear under mountain deciduous forests, which change with mountain meadow soils with height. The Coastal Plains and the Longitudinal Valley are centers of agriculture and horticulture. Corn, wheat, fiber crops are cultivated here. Irrigated agriculture predominates.

South Argentine-Patagonian soil region

The region is elongated meridionally and is divided into two provinces: the Central Argentinean soil of subtropical deserts and semi-deserts and the Patagonian cold, brown desert sandy and stony soils.

The southern Argentinean province of soils of subtropical deserts and semi-deserts covers piedmont plains and intermountain basins of the front ranges of the Andes (Salta, Tucuman, Catamarca, Sierra de Córdoba). The plains lie on abs. you. 1000-1500m, descending towards the east.

By the nature of the relief, these are undulating plains, representing merged fans of alluvial and proluvial material, significantly reworked by the wind. Eolian processes are highly developed, and most soils have a weakly formed profile. Soils less affected by wind erosion have the following profile: underdeveloped grayish or brownish mountains. And, where the cellular structure is well expressed, it passes into the mountains. IN T - heavier mechanical composition, brown or reddish brown, without signs of washout. Most soils are carbonate. Alkaline soils appear in relief depressions; closed drainless depressions, blind mouths of rivers are occupied by salt marshes. Agriculture is not developed here. In small areas where irrigated agriculture is carried out, soils are highly susceptible to secondary salinization.

The Patagonian province of brown desert, sandy and rocky soils covers the Patagonian plateau and lies between 34-50 ° S. sh.

Brown desert-steppe soils dominate. In large areas, the soil surface is covered with a desert shell of crushed stone or pebbles, formed as a result of very intense soil deflation. Under the stony "bridge" one can hardly distinguish a light gray thin humus horizon of various mechanical composition, usually with a well-defined cellularity. This is a carbonate-free and uninhabited horizon. Beneath it is a horizon of somewhat heavier mechanical composition, but without signs of silt illuviation. This horizon has a brown or reddish-brown color, usually carbonate-free or very low-carbonate. Carbonates and readily soluble salts are usually present in the parent rock. In the northern part of Patagonia, solonetzes and salt marshes are found in river valleys. The western high plateaus have a less desert appearance, where the vegetation cover is represented by mountainous dry shrub steppes on mountain chestnut soils.

The southernmost part of Patagonia, where the climate is more humid, is also occupied by chestnut soils with a significant proportion of sandy soils in the soil cover. Volcanic ash is present in large quantities in all soils.

The soils of the river valleys are used for grass crops and orchards, provided they are irrigated. A small amount of water and highly developed phenomena of secondary salinization of soils limit their agricultural use.

SOUTH PACIFIC SUBBOREAL FOREST SECTOR

Patagonian-Fuegoland soil region

The extreme southwestern part of the Andean mountain belt belongs to the subboreal forest sector of the southern hemisphere; in South America it is represented by only one Patagonian-Fierce soil region. It stretches from 38 to 56 ° S. sh., i.e. up to. southern tip of Tierra del Fuego. In the northern part of the Cordillera region rise to 4000m and higher, in the south they do not exceed 2000m. Powerful glaciers descend along the valleys, which in the south almost reach the sea coasts, the coast is very indented, has a fjord character and is replete with small islands. There are many active volcanoes in the northern part of the province, which determines the nature of soil-forming rocks over large areas.

The northern part of the province is dominated by high-humus, acidic ash-volcanic soils - "trumao". On ancient surfaces, on the red-colored kaolinite weathering crust of old volcanic ash deposits, red earths appear. On acid sedimentary rocks - micaceous schists and others - acid brown forest soils are formed. On terraces of rivers and alluvial fans, poorly drained, there are powerful peaty soils with interlayers of volcanic ash, called "nadis".

In the northern part of the province - between Valdivia, Puerto Montt and on about. Chiloe - significant areas of alluvial soils, volcanic soils and red soils are used in agriculture for crops of wheat, oats, potatoes, etc. Soils are poor in available phosphorus, they contain mobile aluminum, which increases acidity. Many soils of depressions have dense ferruginous horizons, which impairs their drainage and, consequently, hinders agricultural use.

In the southern part of the Patagonian Andes and in Tierra del Fuego, under deciduous forests and shrubs, peaty, acidic brown forest soils are developed, podzolized in places. On the slopes of the mountains facing the Patagonia plateau and receiving 300-250mm rainfall, under shrubby cereal steppes - mountain-steppe, chestnut soils. The steppes also cover the extreme northeastern part of Tierra del Fuego, but most eastern plains the islands are occupied by damp, cryophytic meadows and low-lying sphagnum bogs, with a complex of neutral (on carbonate deposits) and acidic peaty-meadow soils, podzolized in places; on sandy deposits they are replaced by illuvial-humus podzols. Large areas in relief depressions are occupied by peat-gley soils.

These areas are used as pastures for sheep.

AGRICULTURAL USE OF SOILS OF SOUTH AMERICA. AGRICULTURAL CROPS.

In the sectoral structure of agriculture in the countries of the Amazon and La Plata, plantations of tropical perennial crops stand out, primarily coffee, for the production of which Brazil traditionally ranks first in the world (1.25 million tons), and sugar cane - in Brazil, Guyana, Suriname and French Guiana. Among the food - corn and rice, as well as cassava. On the steppe chernozems of the Argentinean Pampa, wheat and corn are grown, and since the 60s of the XX century. - soy. The production of industrial crops - cotton, tobacco, tungu, etc. - is increasing. Brazil is the world leader in the cultivation of oranges (18.6 million tons), it provides 80% of the world's exports of orange juice and concentrate.
In many countries, monoculture of agriculture still prevails: in Brazil, Colombia, Guatemala, El Salvador, Costa Rica and Haiti, coffee is the main crop, in Ecuador (their main exporter on the world market), Honduras and Panama - bananas, Guyana and the Dominican Republic. Republic - sugar cane, Peru and Nicaragua - cotton. In many South American countries, one of the main crops is corn, for the production of which Brazil and Argentina are second only to the United States. structure _

seljskogo _ hozyajstva

Unlike North America, where changes in vegetation depend to a large extent on changes in temperature conditions, in South America, with its high temperatures, the nature of the vegetation depends mainly on the degree of moisture. A large amount of solar heat allows the plants of the southern mainland to vegetate throughout the year almost everywhere. As in Africa, the main factor determining the length of the growing season is the degree of moisture. The latter in the hot zone decreases not from the oceans deep into the mainland, but from the equator to the tropics, and only in the subtropics do the differences between the oceanic and inland territories sharply come out. In this regard, the main forest areas in South America are dressed in the equatorial regions. Humid equatorial forests (hyley), including hyley with a short dry period (deciduous-evergreen forests), and monsoon forests cover the Amazon and the 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 most ancient 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, that is, when there were still direct connections with Africa and other parts of the hypothetical Gondwana. Therefore, 12% of the genera of dicotyledonous plants are common to the Neotropical and Paleotropical regions. The long isolation of South America in the Tertiary period determined the high endemism of its flora. Endemic or have in South America the center of their species distribution, not only many genera of plants, but even entire families (jugs - Marcgraviaceae, bromeliads - Bromeliaceae, etc.). From the neotropical hygrophilous flora, apparently, the flora of the savannahs, mountain tropical forests, and even partly the xerophilic flora of the semi-deserts originated. Species of cacti, agaves, and bromeliads, for example, originally arose in humid equatorial forests; ecologically adapting and changing, they penetrated both the western desert coast, and the semi-deserts of Argentina, and the inter-Andean plateaus. Predominantly in the form of epiphytes, they are widespread in the Amazon and at the present time. The equatorial forests were thus the most important center the formation of the vegetation cover of South America, most of which is included in the Neotropical floristic region. Almost as ancient is the flora of the savannas and woodlands. They are located north and south of the humid equatorial and monsoon forests on the plains and plateaus of the east of the mainland up to 30 ° S. sh., and in the west - between 0-5 ° S. sh., occupying an area approximately equal to the hylaea and monsoon forests.

Savannahs 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. sh. Moist forests also cover the slopes of the southern Andes, south of 38 ° S. sh. Up to 46°S sh. they are composed of evergreen hardwoods and conifers (hemigilea). On the western, windward slopes, the forests are denser, on the eastern slopes - sparse and have an admixture of deciduous species. In the extreme south of the Patagonian Andes, on the western slopes they pass into mixed, deciduous-evergreen subantarctic forests, and on the eastern slopes, into predominantly deciduous forests. Due to the fact that in the Quaternary the southern Andes were almost completely covered by glaciers, the settlement of this segment of the mountains occurred relatively recently. Apparently, the center of the spread of flora to the southern Andes after the glaciation was the subtropical Andes of middle Chile, where during the glaciation there were a number of refuges that allowed many relics to survive. etc., from the Andes of middle Chile, the southern beech (Nothofagus), Alerce (Fitzroya cupressoides var. patagontca) moved south. in the west of South America, moist forests are replaced by hard-leaved (Mediterranean) forests and shrubs.Young types of meadow-steppe, semi-desert and desert vegetation prevail in the subtropics in the east of the mainland, including on the eastern slopes of the Andes.Shrub semi-deserts are also common in Patagonia, which lies even further south in rain shadow of the Andes, the vegetation cover of Patagonia also formed only in the post-glacial period from the Antarctic flora.Patagonia and southern Chile belong to Antarctic floristic region. Very young is the vegetation cover of the intermountain plateaus and western slopes of the Central Andes. Recent uplifts of this area and Quaternary glaciations have caused significant changes in climate and vegetation. In the Tertiary time, there was a mesophilic tropical flora, and now mountain-steppe, semi-desert and desert types of vegetation predominate. Due to the position of South America mainly in low latitudes, various types of lateritic soils predominate in it. Hot forest areas with constant and heavy rainfall are characterized by podzolized lateritic soils, which are difficult to separate from a very thick weathering crust. In areas with seasonal moisture, red, brown-red, and red-brown soils are typical.

Ancient ferruginous crusts are widely distributed. Lateritization processes are still manifested in the humid subtropics in the east of the mainland, where red soils and reddish-black soils of the prairies are characteristic. Further to the west, as in North America, they are successively replaced by gray-brown soils and gray soils, and in the extreme west by brown soils. Soil types of cool temperate latitudes are represented by brown forest soils - in the west, chestnut and brown, desert-steppe - in the east. In the Andes, altitudinal zonality with mountain types of zonal soils is clearly expressed. Contrasts of natural conditions and features of the paleogeographic 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 zoogeographic kingdom with a single Neotropical region. Endemic are three families of the order of edentulous (armadillos, anteaters and sloths), broad-nosed monkeys, bats (vampires), rodents (guinea pigs, agoutis, chinchillas), entire orders of birds (Nanda ostriches, tinamou and hoatzins, as well as vultures, toucans , 500 species of hummingbirds, many genera of parrots, etc.) Of the reptiles, endemic caimans, iguana lizards and boa constrictors are characteristic, among fish - electric eel, doubly-harmed siren and others. Insects are distinguished by particular diversity and endemism (3400 species out of 5600). Only in the Pleistocene did the jaguar and puma, skunks, otters, tapirs, peccaries and llamas migrate to South America from North America and spread widely. In South America, there are no a number of animals that are widespread on other continents (big-nosed monkeys, almost no insectivores, few ungulates). The ecological conditions of the desert-steppe spaces and cool forests of the southern Andes differ sharply from the hot savannahs and forests of the more northern parts of the mainland. Therefore, the fauna of these territories also differs significantly. The southern regions are combined into the Chilean-Patagonian zoogeographic subregion, the northern ones - into the Brazilian one.

Unlike North America, where changes in vegetation depend to a large extent on changes in temperature conditions, in South America, with its high temperatures, the nature of the vegetation depends mainly on the degree of moisture. A large amount of solar heat allows the plants of the southern mainland to vegetate throughout the year almost everywhere. As in Africa, the main factor determining the length of the growing season is the degree of moisture. The latter in the hot zone decreases not from the oceans deep into the mainland, but from the equator to the tropics, and only in the subtropics do the differences between the oceanic and inland territories sharply come out. In this regard, the main forest areas in South America are dressed in the equatorial regions. Humid equatorial forests (hyley), including hyley with a short dry period (deciduous-evergreen forests), and monsoon forests cover the Amazon and the 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 most ancient 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, that is, when there were still direct connections with Africa and other parts of the hypothetical Gondwana. Therefore, 12% of the genera of dicotyledonous plants are common to the Neotropical and Paleotropical regions. The long isolation of South America in the Tertiary period determined the high endemism of its flora. Endemic or have in South America the center of their species distribution, not only many genera of plants, but even entire families (jugs - Marcgraviaceae, bromeliads - Bromeliaceae, etc.). From the neotropical hygrophilous flora, apparently, the flora of the savannahs, mountain tropical forests, and even partly the xerophilic flora of the semi-deserts originated. Species of cacti, agaves, and bromeliads, for example, originally arose in humid equatorial forests; ecologically adapting and changing, they penetrated both the western desert coast, and the semi-deserts of Argentina, and the inter-Andean plateaus. Predominantly in the form of epiphytes, they are widespread in the Amazon and at the present time. Thus, the equatorial forests were the most important center for the formation of the vegetation cover of South America, most of which is included in the Neotropical floristic region. Almost as ancient is the flora of the savannas and woodlands. They are located north and south of the humid equatorial and monsoon forests on the plains and plateaus of the east of the mainland up to 30 ° S. sh., and in the west - between 0-5 ° S. sh., occupying an area approximately equal to the hylaea and monsoon forests.

Savannahs 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. sh. Moist forests also cover the slopes of the southern Andes, south of 38 ° S. sh. Up to 46°S sh. they are composed of evergreen hardwoods and conifers (hemigilea). On the western, windward slopes, the forests are denser, on the eastern slopes - sparse and have an admixture of deciduous species. In the extreme south of the Patagonian Andes, on the western slopes they pass into mixed, deciduous-evergreen subantarctic forests, and on the eastern slopes, into predominantly deciduous forests. Due to the fact that in the Quaternary the southern Andes were almost completely covered by glaciers, the settlement of this segment of the mountains occurred relatively recently. Apparently, the center of the spread of flora to the southern Andes after the glaciation was the subtropical Andes of middle Chile, where during the glaciation there were a number of refuges that allowed many relics to survive. etc., from the Andes of middle Chile, the southern beech (Nothofagus), Alerce (Fitzroya cupressoides var. patagontca) moved south. in the west of South America, moist forests are replaced by hard-leaved (Mediterranean) forests and shrubs.Young types of meadow-steppe, semi-desert and desert vegetation prevail in the subtropics in the east of the mainland, including on the eastern slopes of the Andes.Shrub semi-deserts are also common in Patagonia, which lies even further south in rain shadow of the Andes, the vegetation cover of Patagonia also formed only in the post-glacial period from the Antarctic flora.Patagonia and southern Chile belong to Antarctic floristic region. Very young is the vegetation cover of the intermountain plateaus and western slopes of the Central Andes. Recent uplifts of this area and Quaternary glaciations have caused significant changes in climate and vegetation. In the Tertiary time, there was a mesophilic tropical flora, and now mountain-steppe, semi-desert and desert types of vegetation predominate. Due to the position of South America mainly in low latitudes, various types of lateritic soils predominate in it. Hot forest areas with constant and heavy rainfall are characterized by podzolized lateritic soils, which are difficult to separate from a very thick weathering crust. In areas with seasonal moisture, red, brown-red, and red-brown soils are typical.

Ancient ferruginous crusts are widely distributed. Lateritization processes are still manifested in the humid subtropics in the east of the mainland, where red soils and reddish-black soils of the prairies are characteristic. Further to the west, as in North America, they are successively replaced by gray-brown soils and gray soils, and in the extreme west by brown soils. Soil types of cool temperate latitudes are represented by brown forest soils - in the west, chestnut and brown, desert-steppe - in the east. In the Andes, altitudinal zonality with mountain types of zonal soils is clearly expressed. Contrasts of natural conditions and features of the paleogeographic 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 zoogeographic kingdom with a single Neotropical region. Endemic are three families of the order of edentulous (armadillos, anteaters and sloths), broad-nosed monkeys, bats (vampires), rodents (guinea pigs, agoutis, chinchillas), entire orders of birds (Nanda ostriches, tinamou and hoatzins, as well as vultures, toucans , 500 species of hummingbirds, many genera of parrots, etc.) Of the reptiles, endemic caimans, iguana lizards and boa constrictors are characteristic, among fish - electric eel, doubly-harmed siren and others. Insects are distinguished by particular diversity and endemism (3400 species out of 5600). Only in the Pleistocene did the jaguar and puma, skunks, otters, tapirs, peccaries and llamas migrate to South America from North America and spread widely. In South America, there are no a number of animals that are widespread on other continents (big-nosed monkeys, almost no insectivores, few ungulates). The ecological conditions of the desert-steppe spaces and cool forests of the southern Andes differ sharply from the hot savannahs and forests of the more northern parts of the mainland. Therefore, the fauna of these territories also differs significantly. The southern regions are combined into the Chilean-Patagonian zoogeographic subregion, the northern ones - into the Brazilian one.

Latin America is the very place on Earth where natural resources have been preserved almost untouched since the Mesozoic era.

The favorable climate and features of the development of the mainland have caused the fact that today the nature of countries Latin America attracts more and more tourists. They are eager to see many outlandish plants that are not found anywhere else. The flora of South America is rightfully considered the main wealth of the mainland. Such well-known plants as tomatoes, potatoes, corn, chocolate tree, rubber tree were discovered here.

rainforest plants

The tropical rain forests of the northern part of the mainland still amaze with the richness of species, and today scientists continue to discover new plant species here. In these forests there are different types of palm trees, melon tree. There are 750 species of trees and 1,500 species of flowers per 10 square kilometers of this forest.

The forest is so dense that it is extremely difficult to move through it, vines also make it difficult to move. A characteristic plant for the rainforest is ceiba. The forest in this part of the mainland can reach a height of over 100 meters and spread over 12 levels!

Humid tropical (equatorial) forests of South America on ferrallitic soils, called hylaea by A. Humboldt, and in Brazil called selva, occupy a significant part of the Amazonian lowland, adjacent areas of the Orinok lowland and the slopes of the Brazilian and Guiana highlands. They are also characteristic of the coastal strip of the Pacific Ocean within Colombia and Ecuador. Thus, tropical rain forests cover areas with an equatorial climate, but, in addition, they grow on the slopes of the Brazilian and Guiana highlands facing the Atlantic Ocean, in higher latitudes, where there are abundant trade winds for most of the year, and in during a short dry period, the lack of rain is compensated by high humidity.

The hylaea of ​​South America is the richest type of vegetation on the Earth in terms of species composition and density of vegetation cover. They are characterized by high height and complexity of the forest canopy. In areas not flooded by rivers in the forest, there are up to five tiers of various plants, of which at least three tiers consist of trees. The height of the highest of them reaches 60-80 m.

The humid tropical forests of South America are especially rich in vines and epiphytes, often blooming brightly and beautifully. Among them are representatives of the family of arroinaceae, bromeliads, ferns and orchid flowers, unique in their beauty and brightness. Tropical rainforests rise up the slopes of the mountains up to about 1000-1500 m without undergoing significant changes.

Under the influence of human activities, vegetation has undergone significant changes. In just 15 years, from 1980 to 1995, the area of ​​forests in South America decreased by 124 million hectares. In Bolivia, Venezuela, Paraguay and Ecuador, the rate of deforestation over this period exceeded 1% per year. For example, in 1945, in the eastern regions of Paraguay, forests occupied 8.8 million hectares (or 55% of the total area), and in 1991 their area was only 2.9 million hectares (18%). In Brazil, about 15 million hectares of forests were destroyed between 1988 and 1997. It should be noted that after 1995

there has been a marked decrease in the rate of deforestation. The main cause of deforestation in the Brazilian Amazon remains the expansion of agricultural land, mostly permanent pastures. The destruction of forests leads to the destruction of the upper soil horizon, the development of accelerated erosion and other processes of soil degradation. Due to deforestation and overloading of pastures, soil degradation processes have affected almost 250 million hectares of land.

tropical savanna plants

To the south of the selva there are variable-moist forests and savannahs, where the quebracho tree grows, which is famous for its very hard and very heavy wood, a valuable and expensive raw material. In the savannas, small forests give way to thickets of cereals, shrubs and tough grasses.

Cerrado

The Cerrado region in east-central and southern Brazil is the largest savannah biome in South America. Cerrado contains more than ten thousand plant species, 44% of which are endemic. About 75% of the territory has been lost since 1965, while the rest has been fragmented.

Pantanal

Two other areas of the savannah further south are the Pantanal and the Pampas. Although the Pantanal is a savanna, during the rainy season it becomes a wetland and is a habitat for aquatic plants. When the Pantanal dries up, savannahs appear instead of water. This unique area is threatened by various human activities, including shipping, artificial drainage, mining, Agriculture and urban waste.

Pampas

Further south are the pampas - the South American steppes. Here you can find many types of herbs, common for Eurasia: feather grass, bearded vulture, fescue. The soil here is quite fertile, as there is less rainfall and it is not washed out. Shrubs and small trees grow among the grasses.

Flora of mediterranean climate and temperate forests

This climate is characterized by warm, dry summers and cool, wet winters. The vegetation consists mainly of leathery-deciduous evergreen shrubs that are well adapted to the long summer drought. The Chilean Matorral is the only Mediterranean area that has bromeliads. In lower areas, many shrubs are dry deciduous, meaning they shed their leaves in summer.

Because South America extends far south, it has a small region of temperate forests called the Valdivian Forests. They range from temperate rain forest to drier temperate forests, and in all cases nothophagus tend to predominate. It is dominated by small evergreen trees and shrubs. Fuchsias, which are valued all over the world for their beautiful flowers,

grow in the undergrowth. Although not rich in species, the temperate rainforests of the southern part of the continent can be quite dense.

desert plants

The south of the mainland is desert, the climate is more severe there, and therefore the vegetation is much poorer. Shrubs, some types of grasses and cereals grow on the stony soil of the Patagonian desert. All plants are resistant to drought and constant weathering of the soil, among them are resinous chanyar, chukuraga, Patagonian fabiana.

Atacama Desert

In the Atacama Desert, one of the driest in the world, there is some humidity, but it is limited to certain areas. Coastal areas below 1000 meters receive regular fog (called camanchacas).

The rainfall in the Atacama Desert is so low that even cacti (which normally accumulate moisture) can hardly get enough water from a single rainstorm, so many plants, including species from the Bromeliad family, take some of the necessary moisture from the mists. There is no regular fog in sections of medium height; thus, there is almost no vegetation cover. In higher areas, the rising air cools enough to produce moderate rainfall, although the vegetation is still desert. Shrubs tend to grow near stream beds where their roots can reach a permanent water source. The Atacama Desert often appears barren, but when enough moisture is available, the ephemera changes its appearance.

Patagonian wilderness

Conditions in the Patagonian desert are less harsh. Vegetation ranges from grassland tussocks near the Andes to much shrub-steppe flora further east.

In the shrub steppes of Patagonia, cushion-shaped plants and kulembay shrubs are found. Where the soil is salty, quinoa and other salt-tolerant shrubs grow.

4 unusual plants of South America

jacaranda

You can meet him in Brazil, Argentina and the West Indies.

Jacaranda is so beautiful during the flowering period that streets, squares and squares are decorated with it. This tree is especially loved in Buenos Aires. It blooms almost always.

So, at the end of spring and at the beginning of winter, the flowering of jacaranda is the most abundant, and in summer and autumn - a little more modest. However, the spectacle is incredible anyway. Bright purple delicate flowers cover the crown so densely that it is almost impossible to see green leaves behind them, very similar to mimosa leaves.

Although jacaranda is not such a rarity in South America, it is unlikely that anywhere else you can walk along a thick carpet of crumbling purple petals and enjoy the violet scent emanating from these beautiful trees.

Psychotria

Psychotria is considered no less interesting - a small tree whose flowers resemble juicy scarlet lips, as if folded into a kiss. In total, there are about a hundred species of this plant, and you can find it in Panama, Ecuador, Colombia and Costa Rica. With its seductive appearance, the flowers of this plant attract the main pollinators - butterflies and hummingbirds.

Psychotria is under the threat of complete extinction due to uncontrolled deforestation. But you can still catch "hot sponges" by finding them in Latin American forests.

Balsa

If you decide to go to Ecuador, then you may be lucky to see the balsa, or the so-called hare tree. This is a very tall tree from the baobab family.

It almost disappeared from the face of the Earth because of its valuable wood: very light, soft and loose, after drying it becomes harder than oak. Balsa was once used to make boats, rafts and canoes, but today its wood is only enough for surfboards and fishing lures. This tree is called hare because of its fruits - pods with seeds, which, after opening, become like fluffy hare legs.

There are no more balsa forests left, but small groups of these trees can still be found in the rain and humid Ecuadorian forests.

cashew tree piranji

Another unique tree grows in Brazil, near the city of Natal.

This is the Piranji cashew tree, which is already 177 years old and has “snipped off” almost two hectares of land. Piranji is a mutant tree. An ordinary cashew tree grows like a tree, but not Piranji, as its branches, as soon as they touch the ground, take root, as a result of which the tree continues to grow. Thus, a single tree replaced a whole forest. By the way, it still bears fruit - about 80 thousand fruits a year. It is the largest cashew tree in the world as it is 80 times the size of a normal cashew tree.

conclusions

The plants of South America are also quite diverse. The Amazon rainforests occupy vast areas, including, in addition to northern Brazil, French Guiana, Suriname, Guyana, southern Venezuela, western and southern Colombia, Ecuador, and eastern Peru. In addition, this type of forest is found in Brazil in a narrow strip along the Atlantic coast, as well as on the Pacific coast from the border of Panama to Guayaquil in Ecuador. Trees in these forests reach 80 m (ceiba), melon tree, cocoa, rubber hevea grow. Plants are entwined with vines, many orchids. However, scientists fear that these “lungs of the planet” may disappear from the surface of the Earth by the end of the 21st century (such a sad forecast was made by climatologists participating in a conference on climate change, which was held in Copenhagen from March 6 to 18, 2009 ).

The savannahs occupy the Orinok Lowland and most of the Guiana and Brazilian Highlands. In the northern hemisphere, among tall grasses (llanos), there are tree-like spurges, cacti, mimosa, bottle trees. In the south (campos) it is much drier, there are more cacti. The steppes of South America (pampas) have fertile reddish-black soils, cereals predominate. Deserts and semi-deserts are located in the temperate zone in Patagonia. The soils are brown and gray-brown, dry grasses, cushion-shaped shrubs.

Video

Sources

http://latintour.ru/sa/sa-info/rasteniya.html