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Land cover of South America

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Land cover of South America

South America is characterized by a large variety of zonal types of land cover and the exceptional richness of the 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 continent’s development, which took place first in close connection with other continents of the southern hemisphere, and later almost completely isolated from large land masses, if not considered connections with North America through the Isthmus of Panama.

Most of South America, up to 40 ° S, together with Central America and Mexico forms the Neotropical Floristic Kingdom. The southern part of the continent enters the limits of the Antarctic Floristic Kingdom.

Within the land bounding the South American platform with the African one, apparently, there was a common center for the formation of the savanna flora and tropical forests for both continents, which explains the presence of some common plant species and genera in their composition. However, the separation of Africa and South America at the end of the Mesozoic led to the formation of an independent flora on each of these continents and the separation of the Paleotropic and Neotropical kingdoms. Neotropics are characterized by great wealth and a high degree of endemism of the flora, due to the continuity of its development from the Mesozoic and the presence of several large centers of speciation.

The flora of the South American continent has given mankind many valuable plants that have become part of the culture, not only in the western hemisphere, but also beyond. These are 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 Chiloe Island. Andes – the birthplace of tomatoes, beans, pumpkins. It is still not clear exactly the ancestral homeland and the wild ancestor of cultivated maize is unknown, but undoubtedly it comes from the Neotropical Kingdom. South America is also home to the most valuable rubber – hevei, chocolate, cinchona trees, cassava and many other plants grown in tropical regions of the Earth. The richest vegetation of South America is an inexhaustible source of vast natural resources – food, fodder, industrial, medicinal plants.

The tropical rainforests are uncommon in the vegetation cover of South America, which have no equal on Earth, neither in terms of species richness, nor in the size of their territory.

The wet tropical (equatorial) forests of South America on ferralitic soils are gilles, and in Brazil they are called the jungle, occupy a significant part of the Amazonian lowland, the adjacent areas of the Orynok lowland and the slopes of the Brazilian and Guiana highlands. They are also characteristic of the Pacific coastal zone within Colombia and Ecuador. Thus, tropical rainforests cover areas with an equatorial climate, but, in addition, they grow along the slopes of the Brazilian and Guiana highlands, facing the Atlantic Ocean, in higher latitudes, where heavy trade winds are heavy for most of the year. during the short dry period the lack of rain is compensated by high humidity.

The gilles of South America are the richest species of the Earth in terms of species composition and plant cover density. They are characterized by high height and complexity of the forest canopy. On the flood-free areas 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.

As the climate changes, that is, with the advent of the dry season, tropical rainforests turn into savannas and tropical light forests. On the Brazilian Highlands between savannas and tropical rainforest, there is a strip of almost pure palm forests. Savannah are spread over a large part of the Brazilian Highlands, mainly in its inland areas. 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 ferralitic soils are known as campos. Their herbaceous vegetation consists of high grasses of the genera Paspalum, Andropogon, Aristida, as well as representatives of the leguminous and complex-color families. Woody forms of vegetation are either completely absent, or are found in the form of individual specimens of mimosa with an umbrella-like crown, tree-like cacti, euphorbia and other xerophytes and succulents.

In the dry northeast of the Brazilian Highlands, a large area is occupied by so-called caatinga, which is a rarefied forest of drought-resistant trees and shrubs on red-brown soils. Many of them lose their leaves for a dry period of the year, others have a bloated trunk in which moisture accumulates, for example, vatnik (Cavanillesia platanifolia). The trunks and branches of the kathingi trees often cover lianas and epiphytic plants. There are also several types of palm trees. The most remarkable kaatinga tree is carnauba wax tree (Copernicia prunifera), which gives 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. From the upper part of the trunk carnauba receive sago and palm flour, the leaves go to cover the roofs and weave various products, the roots are used in medicine, and the local people use the fruits in food in raw and cooked form. No wonder the people of Brazil called the carnauba tree of life.

On the plain of the Gran Chaco, in particularly arid areas, thorny shrubs and sparse forests are spread on brown-red soils. In their composition, two species belong to different families, they are known under the general name “kebracho” (“break the ax”). These trees contain a large amount of tannins: red kebracho (Schinopsis Lorentzii) – up to 25%, white kebracho (Aspidosperma quebracho blanco) – slightly less. Their wood is heavy, dense, resists rotting and sinks in water. Kebracho stubbornly cut down. At special factories, tanning extract is obtained from it, sleepers, piles and other objects intended for a long stay in water are made from wood. Algarobos (Prosopis juliflora) is also found in forests – a tree from the mimosa family with a curved trunk and a strongly branching spreading crown. Small tender foliage of algarrobo gives no shade. The low tiers of the forest are often represented by thorny bushes forming impassable thickets.

The savannas of the northern hemisphere differ from the southern savannas in their appearance and species composition of the flora. South of the equator, among the thickets of grasses and dicots, palms are raised: copernicia (Copernicia spp.) – in drier places, and Mauritia flexuosa – in marshy or river-flooded areas. The wood of these palm trees is used as a building material, the leaves are used for weaving various products, the fruit and core of the mauristion stem are edible. Acacias and tall tree cacti are also numerous.

The red and red-brown soils of savanna and tropical light forests are distinguished 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 tree, cotton, bananas and other cultivated plants exported from Africa.

The Pacific coast is between 5 and 27 ° S. and the Atacama Basin, with their constant rainlessness, has the most typical desert soils and vegetation in South America. Areas of almost barren stony soils alternate with masses of loose sand and extensive surfaces occupied by saltpetre salt marshes. Extremely sparse vegetation is represented by rarely standing cacti, prickly pincushion bushes and ephemera of bulbous and tuberiferous 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 with subtropical forests of Araucaria with undergrowth from various bushes, including Paraguayan tea (Ilex paraguaiensis). Paraguayan tea leaves are used by local people to make a widespread hot drink that replaces tea. By 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 in South America – the subtropical steppe, or pampa, characteristic of the eastern, most humid parts of the La Plata lowland south of 30 ° S – is grassy grass vegetation on fertile reddish-black soils that form on volcanic rocks. It consists of the South American species of those genera of cereals, which are widespread in Europe in the steppes of the temperate zone (feather grass, bearded, fescue). With the forests of the Brazilian Highland, the pampa is associated with a transitional type of vegetation close to the forest-steppe, where the herbs are combined with thickets of evergreen shrubs. Pampa vegetation has undergone the most severe extermination and is now almost completely replaced by crops of wheat and other cultivated plants. To the west and south, as the precipitation decreases, the vegetation of dry subtropical steppes and semi-deserts appears on gray-brown soils and gray soils with spots of salt marshes at the site of dry lakes.

The subtropical vegetation and soils of the Pacific coast resemble the vegetation and soils of the European Mediterranean. Thickets of evergreen shrubs on brown soils predominate.

For the extreme southeast (Patagonia), the vegetation of dry steppes and semi-deserts of the temperate zone is characteristic. Gray-brown soils predominate, salinization is widespread. The vegetation cover is dominated by high cereals (Roa flabellata, etc.) and various xerophytic shrubs, often pillow-shaped, low-growing cacti.

In the extreme southwest of the continent with its oceanic climate, insignificant annual differences in temperature and abundance of precipitation, moisture-loving evergreen sub-Antarctic forests, multi-tiered and very diverse in composition, grow. They are close to tropical forests for the richness and diversity of life forms of plants and the complexity of the forest canopy structure. They are full of lianas, mosses, lichens. Along with various high-coniferous trees from 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 underbrush. These moisture-saturated forests are difficult to clear and uproot. They are still one of the most important natural resources of Chile, although they have suffered greatly from logging and fires. Almost without changing its composition, forests rise along the mountain slopes up to a height of 2000 m. Under these forests forest burozems develop. To the south, as the climate gets cold, the vines, tree ferns and bamboo disappear. Conifers (Podocarpus andinus, Austrocedrus chilensis) prevail, but evergreen beeches and magnolias remain. Podzolic soils are formed under these depleted sub-Antarctic forests.

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