Climatic features of variable humid forests. Zone of variable-moist subtropical forests

For tropical wet evergreens, or as they are sometimes called, rainforests are characterized by a three-tier structure of the tree canopy. The tiers are poorly demarcated. The upper tier is made up of giant trees 45 m or more in height, 2-2.5 m in diameter. The middle tier is represented by trees about 30 m high with a trunk diameter of up to 90 cm. Smaller, exceptionally shade-tolerant trees grow in the third tier. There are many palm trees in these forests. The main area of ​​\u200b\u200btheir growth is the Amazon basin. Here they occupy vast areas, including, in addition to the northern part of Brazil, French Guiana, Suriname, Guyana, the southern part of Venezuela, the west and south of Colombia, Ecuador and the east of Peru. In addition, this type of forest is found in Brazil in a narrow strip along the Atlantic coast between 5 and 30°S. Similar evergreen forests also grow along the Pacific coast from the border of Panama to Guayaquil in Ecuador. Here are concentrated all types of the genus Svitania (or mahogany), rubber-bearing genus Hevea, Brazil nut (Bertolletia excelsa) and many other valuable species.

Tropical variable-humid deciduous forests distributed in the southeast of Brazil and in the south of Paraguay. Tree species in them are relatively small in height, but often with thick trunks. Legumes are widely represented in the forests. Subtropical deciduous broadleaf forests most common in the south of Brazil and Parguay, in the west of Uruguay and in the north of Argentina along the Parana and Uruguay rivers. montane evergreen forests cover the slopes of the Andes from Venezuela to central Bolivia. These forests are characterized by thin-stemmed low trees forming dense stands. Due to the fact that these forests occupy steep slopes and are far from populated areas, they are exploited very little.

Araucaria forests located in two isolated regions. Brazilian Araucaria (Araucaria brasiliana) is predominant in the states of Parana, Santa Catarina and Rio Grande do Sul in Brazil, as well as in Uruguay, Eastern Paraguay and Argentina. A less significant massif is formed by forests of Chilean araucaria (A. araucana) found in the Andes at 40°S. in the altitude range from 500 to 3000 m above sea level. seas. These forests are characterized by hardwood species, among which the most important is embuya (Phoebe porosa). In the undergrowth of the araucaria forests, the mate shrub, or Paraguayan tea (Ilex paraguariensis), is also widespread on plantations.

Low growing xerophilous forests distributed in the east of Brazil, in the northern part of Argentina and in the western part of Paraguay. The most important tree species in these forests is the red querbacho (Schinopsis sp.), from which tannin is obtained. mangrove forests occupy the coastal strip of the Atlantic part of South America. These forests are dominated by red mangrove (Rhizophora mangle), forming pure stands or mixed with Avicenna (Avicennia marina) and Conocarpus erecta.

In addition to timber harvesting, rubber, food products (seeds, nuts, fruits, beans, leaves, etc.), oils, medicinal substances, tannins, resins, including chicle (Zschokkea lascescens), raw materials for the production of chewing gum.

Venezuela. Evergreen (on laterites) and deciduous forests grow on the slopes of the spurs of the Andes and the Guiana Highlands. On the territory of the low llanos, tall-grass savannah with groves of the Mauritian palm is widespread, and in the high llanos, xerophilic light forests and shrub communities are common. Mangroves stretch around Lake Maracaibo, giving way to undersized xerophilous, and to the south - evergreen tropical forests. In the south of the country, in the upper reaches of the river. Orinoco and its right tributaries grow moist evergreen tropical forests, almost inaccessible to exploitation. Of the tree species of economic value, mahogany, roble-colorado, baku, balsa, espave (Anacardium spp.), angelino (Ocotea caracasana), oleo-vermelho (Myroxylon balsamum), pao-roxo, guaiacum, tabebuya (Tabebuia pentaphylla ), ceiba (Ceiba pentandra), almasigo (Bursera simaruba), kurbaril (Hymenaea courbaril), adobe (Samanea saman), etc.

Landscape in the center of Venezuela

Colombia. According to natural conditions, two regions are distinguished: the eastern (plain) and the western (mountainous, where the Colombian Andes stretch). The first region is largely occupied by humid evergreen forests of the Magdalena basins and the left tributaries of the Amazon. To the north and west of the Guajira peninsula, along the Caribbean coast, low-growing xerophilous forests extend, in which divi-divi beans (Libidibia coriaria) are harvested for tannin. Guaiac wood (Guaiacum spp.) is also harvested here - this is one of the hardest and heaviest woods in the world, used for the manufacture of rollers, blocks and other engineering products.

Mangrove forests stretch along the Pacific and Caribbean coasts. In evergreen tropical hylaea, especially in the lower part of the Magdalena basin and along the mouth of the river. Atrato, cativo wood (Prioria copaifera) is harvested for export, as well as baku, or "Colombian mahogany" (Cariniana spp.), caoba, or real mahogany (Swietenia macrophylla), roble colorado, or Panamanian mahogany (Platymiscium spp.) , purple tree, or paoroxo (Peltogyne spp.), etc. In the eastern part of the elevated plain along the tributaries of the Orinoco, savanna-llanos with rare trees and gallery forests with Mauritian palm (Mauricia sp.) are common. The forests of the mountain regions of the Andes are characterized by a peculiar altitudinal zonality. On the lower parts of the lee slopes and on the northern ridges, deciduous forests or thorny shrubs are common. In the adjacent part of the mountains (from 1000 to 2000 m) mountain broad-leaved evergreen forests grow with tree ferns, wax palm (Copernicia cerifera), cinchona, coca (Erythroxylon coca) and various orchids. Cultivated crops include cocoa and coffee trees. At an altitude of 2000 to 3200 m, humid alpine hylaea, in which there are many species of evergreen oaks, shrubs and bamboos.

Ecuador. Three natural areas are distinguished on the territory of the country: 1) a watershed plateau with moist equatorial forests - hylaea, or selva(together with the upper reaches of the left tributaries of the Amazon); 2) Andes ranges; 3) the Pacific forest-savannah plain and the western slopes of the Andes. The evergreen tropical forests of the first region are poorly studied and difficult to access. On the western slopes of the Andes, up to a height of 3000 m, evergreen mountain broad-leaved forests (hylaea) grow, largely disturbed by slash-and-burn agriculture. They produce a lot of cinchona bark, as well as balsa, kapok from the fruits of ceiba, leaves of the toquilla palm, or hipihapa (Carludovica palmata), used to make Panama hats. Tagua palm (Phytelephas spp.) is also found here, the hard endosperm of the fruits of which is used to produce buttons, and various rubber plants. The lower part of the western slopes is characterized by evergreen tropical forests. In the river valley Guayas is intensively harvested for export balsa wood.

Guyana, Suriname, Guiana. The forests of these countries, located along the coast of the Atlantic Ocean and along the Guiana Highlands, are evergreen tropical with a number of valuable species. The green tree, or betabaro (Ocotea rodiaei), which is exported in Guyana and Suriname, stands out in particular. Apomate (Tabebuia pentaphylla), canalette (Cordia spp.), pekia (Caryocar spp.), espave (Anacardium spp.), habillo (Hura crepitans), wallaba (Eperua spp.), carap (Carapa guianensis), virola are no less valuable. (Virola spp.), Simaruba (Simaruba spp.), etc.

Brazil. There are more than 7 thousand species of woody and shrubby plants in the flora, of which there are over 4.5 thousand species in the Amazonian selva. High bertholecia grow (giving brazil nuts, etc.), various rubber plants, including brazilian hevea, which has become a valuable plantation crop in many countries of South Asia and Africa, laurels, ficuses, brazilian mahogany, or "pau brazil", which gave the name to the country (Caesalpinia echinata), chocolate tree, or cocoa, mahogany, jacaranda, or rosewood, oleo vermelho, roble colorado and sapukaya, or paradise nut (Lecythis ustata), and many others. In the east, the selva turns into light palm forests, among which we note the valuable babasu palm (Orbignya speciosa), which has highly nutritious nuts. South of the Amazonian selva, landscapes of tropical dry woodlands are common - caatinga, in which trees grow that shed their leaves in the dry season and accumulate moisture in the rainy season, for example, the bottle tree (Cavanillesia arborea), thorny shrubs, cacti (Cereus squamulosus). In the floodplains, there is a carnauba, or wax, palm (Copernicia cerifera), from the leaves of which wax is collected, which is used in technology. From the south, subtropical deciduous forests adjoin forests dominated by palms and savannahs. In the southeast of the country, along the Brazilian Highlands, there are araucaria forests from the Brazilian, or Paran, araucaria (pinheiro, or "Brazilian pine"). Along with it, embuya, tabebuya, cordia grow, and in the undergrowth of yerbamate, Paraguayan tea is prepared from its leaves. Araucaria forests are involved in intensive exploitation.

Along the Atlantic coast and at the mouth of the Amazon, mangrove forests grow, dominated by red mangrove with an admixture of black mangrove (Avicennia marina) and white mangrove (Conocarpus erecta). Tannin is extracted from the bark of these trees.

Argentina. There are several natural regions. The east is dominated by evergreen forests, in which more than 100 species of trees of great economic importance grow. Among them are cabreuva (Myrocarpus frondosus), kanzherana (Cabralea oblongifolia), Brazilian araucaria, tabebuya, etc. In the west, evergreen ice grows along the slopes of the Andes at an altitude of 2000-2500 m above sea level. seas. Palo blanco (Calycophyllum multiflorum), cedro salteno (Cedrela balansae), roble cryolo (Amburana cearensis), nogal cryolo (Juglans australis), tarco (Jacaranda mimosifolia), type blanco (Tipuana tipu), etc. In the south, along the slopes of the Andes, subantarctic vegetation extends, among which several species of southern beech, alerce, "Cordillera cypress" (Austrocedrus chilensis), etc., are distinguished. palosanto (Bulnesia sarmientoi), guaiacan (Caesalpinia paraguarensis), and others. To the south, along the eastern slopes of the Andes, there are xerophilic broad-leaved forests of the temperate zone with algarrobo, acacias (Acacia caven), carcass (Celtis spinosa), quebracho-blanco.

Paraguay. Forest cover 51%. In the east of the country, mixed tropical evergreen and deciduous forests are common, turning in the west (in the Gran Chaco region) into woodlands and savannahs. The main tree species is quebracho blanco (Aspidosperma quebracho-blanco).

Uruguay. Forests occupy an insignificant part of the total territory of the country and are located in the lower reaches of the Rio Negro and in the valley of the river. Uruguay. The forest cover of the country is 3%. Large areas are beginning to be occupied by artificial plantations - pines on coastal dunes and eucalyptus plantations.

Published according to the monograph: A.D. Bukshtynov, B.I. Groshev, G.V. Krylov. Forests (Nature of the world). M.: Thought, 1981. 316 p.

The continent of South America is located in all geographical zones, with the exception of the subantarctic and antarctic. The wide northern part of the mainland lies in low latitudes, so the equatorial and subequatorial belts are most widespread. A distinctive feature of the continent is the wide development of natural forest zones (47% of the area). 1/4 of the world's forests are concentrated on the "green continent"(Fig. 91, 92).

South America gave humanity many cultivated plants: potatoes, tomatoes, beans, tobacco, pineapple, hevea, cocoa, peanuts, etc.

natural areas

In the equatorial geographical zone there is a zone humid equatorial forests occupying the Western Amazon. They are named by A. Humboldt hylaea, and by the local population - the selva. The humid equatorial forests of South America are the richest in species composition of forests on Earth. They are rightfully considered the "gene pool of the planet": they have more than 45 thousand plant species, including 4000 woody ones.

Rice. 91. Endemic animals of South America: 1 - giant anteater; 2- hoatzin; 3 - lama; 4 - sloth; 5 - capybaras; 6 - armadillo

Rice. 92. Typical trees of South America: 1 - Chilean araucaria; 2 - wine palm; 3 - chocolate tree (cocoa)

There are flooded, non-flooded and mountain hylaea. In river floodplains, flooded with water for a long period, depleted forests grow from low trees (10-15 m) with respiratory and stilted roots. Cecropia (“ant tree”) prevails, giant victoria-regia swim in the reservoirs.

In elevated areas, rich, dense, multi-tiered (up to 5 tiers) non-flooded forests are formed. Up to a height of 40-50 m, single-standing ceiba (cotton tree) and Bertoletia, which gives Brazil nuts, rise. The upper tiers (20-30 m) form trees with valuable wood (rosewood, pau brazil, mahogany), as well as ficus and hevea, from the milky juice of which rubber is obtained. In the lower tiers, under the canopy of palm trees, chocolate and melon trees grow, as well as the oldest plants on Earth - tree ferns. The trees are densely intertwined with vines, among the epiphytes there are many brightly colored orchids.

Near the coast, mangrove vegetation is developed, poor in composition (nipa palm, rhizophora). Mangroves- these are thickets of evergreen trees and shrubs of the swampy zone of marine tides of tropical and equatorial latitudes, adapted to salt water.

Moist equatorial forests form on red-yellow ferralitic soils that are poor in nutrients. Falling leaves in a hot and humid climate quickly rot, and the humus is immediately absorbed by plants, not having time to accumulate in the soil.

Hylaean animals are adapted to life on trees. Many have prehensile tails, like the sloth, opossum, prehensile-tailed porcupine, broad-nosed monkeys (howler monkeys, arachnids, marmosets). Pig-peccaries and tapir live near the reservoirs. There are predators: jaguar, ocelot. Turtles and snakes are numerous, including the longest - anaconda (up to 11 m). South America is the "continent of birds". Gilea is a home for macaws, toucans, hoatsins, tree chickens and the smallest birds - hummingbirds (up to 2 g).

The rivers are teeming with caimans and alligators. They are home to 2,000 species of fish, including the dangerous predatory piranha and the world's largest arapaima (up to 5 m in length and weighing up to 250 kg). There are electric eel and freshwater dolphin iniya.

Zones stretched across three geographical zones variable-moist forests . Subequatorial variable-humid forests occupy the eastern part of the Amazonian lowland and the adjacent slopes of the Brazilian and Guiana plateaus. The presence of a dry period causes the appearance of deciduous trees. Among the evergreens, cinchona, ficuses, and balsa, which have the lightest wood, predominate. In tropical latitudes, on the humid eastern outskirts of the Brazilian Plateau, on mountainous red soils, rich evergreen tropical forests grow, similar in composition to equatorial ones. The southeast of the plateau on the red and yellow soils is occupied by sparse subtropical variable-moist forests. They are formed by Brazilian araucaria with an undergrowth of yerba mate ("Paraguayan tea") shrub.

Zone savannas and woodlands distributed in two geographical zones. In subequatorial latitudes, it covers the Orinoc lowland and the interior regions of the Brazilian Plateau, in tropical latitudes, the Gran Chaco plain. Depending on the moisture, humid, typical and desert savannas are distinguished, under them, respectively, red, brown-red and red-brown soils develop.

Tall-grass wet savannah in the Orinoco basin is traditionally called llanos. It is flooded for up to six months, turning into an impenetrable swamp. Cereals, sedges grow; Mauritius palm dominates the trees, which is why llanos is called the "palm savannah".

On the Brazilian plateau, the savannahs are called campos. Wet shrub-tree savannah occupies the center of the plateau, typical grassy savannah occupies the south. Undersized shrubs grow against the background of grassy vegetation (bearded vultures, feather grasses). Palm trees (wax, oil, wine) dominate among the trees. The arid northeast of the Brazilian Plateau is occupied by the deserted savanna - caatinga. This is a woodland of thorny shrubs and cacti. There is a bottle-shaped tree that stores rainwater - a bombaks vatochnik.

Savannahs continue in tropical latitudes, occupying the Gran Chaco plain. Only in tropical woodlands is the quebracho tree (“break the ax”) with hard and heavy wood sinking in water. Plantations of coffee tree, cotton, bananas are concentrated in the savannahs. Dry savannahs are an important pastoral area.

The animals of the savannas are characterized by a protective brown coloration (spicy-horned deer, red nosokha, maned wolf, ostrich rhea). Rodents are abundantly represented, including the largest in the world - the capybara. Many hylaean animals (armadillos, anteaters) also live in the savannas. Termite mounds are everywhere.

On the Laplat lowland south of 30 ° S. sh. formed subtropical steppes . In South America they are called pampas. It is characterized by rich forb-grass vegetation (wild lupine, pampas grass, feather grass). The chernozem soils of the pampas are very fertile, therefore they are heavily plowed. The Argentine pampa is the main wheat and forage grass growing area in South America. The fauna of the pampas is rich in rodents (tuco-tuco, viscacha). There are pampas deer, pampas cat, puma, ostrich rhea.

Semi-deserts and deserts South America extends into three geographical zones: tropical, subtropical and temperate. In the west of the tropics, tropical deserts and semi-deserts stretch in a narrow strip along the Pacific coast and on the high plateaus of the Central Andes. This is one of the driest regions on Earth: in the Atacama Desert, it may not rain for years. Dry grasses and cacti grow on the infertile sierozems of coastal deserts, receiving moisture from dews and fogs; on gravelly soils of high-mountainous deserts - creeping and pillow-shaped grasses and thorny shrubs.

The fauna of tropical deserts is poor. The inhabitants of the highlands are llamas, a spectacled bear, and a chinchilla with valuable fur. There is an Andean condor - the largest bird in the world with a wingspan of up to 4 m.

To the west of the pampas, in conditions of a continental climate, subtropical semi-deserts and deserts are widespread. On the sierozems, light forests of acacias and cacti are developed, on salt marshes - saltwort. In the harsh temperate latitudes in flat Patagonia, dry grasses and thorny shrubs grow on brown semi-desert soils.

The southwestern outskirts of the mainland in two belts are occupied by natural forest zones. In the subtropics, under the conditions of the Mediterranean climate, a zone is formed dry hardwood forests and shrubs . The coast and slopes of the Chilean-Argentine Andes (between 28° and 36° S) are covered with forests of evergreen southern beeches, teak, perseus on brown and grey-brown soils.

To the south are located wet evergreens and mixed forests . In the north of the Patagonian Andes, in a subtropical humid climate, moist evergreen forests grow on mountain brown forest soils. With abundant moisture (more than 3000-4000 mm of precipitation), these rainforests are multi-tiered and rich, for which they received the name "subtropical hylaea". They consist of evergreen beeches, magnolias, Chilean araucaria, Chilean cedar, South American larch with a rich undergrowth of tree ferns and bamboos. In the south of the Patagonian Andes, in a temperate maritime climate, mixed forests of deciduous beech and coniferous podocarpus grow. Here you can meet a pudu deer, a Magellanic dog, an otter, a skunk.

Andean highlands occupies a vast territory with a well-defined altitudinal zonality, which is most fully manifested in the equatorial latitudes. Up to a height of 1500 m, a hot belt is common - hylaea with an abundance of palms and bananas. Above the level of 2000 m - a temperate zone with cinchona, balsa, tree ferns and bamboos. Up to the level of 3500 m, the cold belt extends - an alpine hylaea from a stunted crooked forest. It is replaced by a frosty belt with alpine meadows of paramos from cereals and undersized shrubs. Above 4700 m - a belt of eternal snow and ice.

Bibliography

1. Geography grade 8. Textbook for the 8th grade of institutions of general secondary education with the Russian language of instruction / Edited by Professor P. S. Lopukh - Minsk "Narodnaya Asveta" 2014

Variably humid forests, unlike permanently humid forests, grow in areas of the planet where precipitation does not occur all year round, but only during the rainy season. At the same time, with the drought season, they have to shed their leaves in order to protect themselves from excessive evaporation in conditions of moisture deficiency. Variably humid forests grow mainly on the territory of the subequatorial climatic zone. They occupy the northern tip of South America, the countries of the American isthmus, large areas of Brazil, where they are called caatinga, in Africa - south and north of the equator, the central part of Madagascar, northeast Hindustan, the east coast of Indochina and northern Australia. They are also often referred to as deciduous variable rain forests or monsoon forests, as they often grow in areas with monsoonal climates. The biodiversity here is also very high, however, much less than in the humid equatorial forests. Animals and plants here have to adapt to strongly changing weather conditions throughout the year. Precipitation falls here during the summer, reaching an average of 1000 to 2000 mm per year, but at the end of the rainy season, drought sets in sharply, and there is practically no rain during the winter. Variably humid forests are home to significantly more mammals, deer, many rodents, monkeys and felines live here. There are many birds in the trees. The soils here are also ferralitic, but predominantly red. With a decrease in the amount of rain, the concentration of humus in them increases. Alternately humid forests, as well as equatorial forests, are threatened by man. The restoration of these forests is possible, however, it will take a long time, so it is necessary to think about their rational use.

Variably humid forests, unlike permanently humid forests, grow in areas of the planet where precipitation does not occur all year round, but only during the rainy season. At the same time, with the drought season, they have to shed their leaves in order to protect themselves from excessive evaporation in conditions of moisture deficiency. Variably humid forests grow mainly on the territory of the subequatorial climatic zone.

They occupy the northern tip of South America, the countries of the American isthmus, large areas of Brazil, where they are called caatinga, in Africa - south and north of the equator, the central part of Madagascar, northeast Hindustan, the east coast of Indochina and northern Australia. They are also often referred to as deciduous variable rain forests or monsoon forests, as they often grow in areas with monsoonal climates.

The biodiversity here is also very high, however, much less than in the humid equatorial forests.

Animals and plants here have to adapt to strongly changing weather conditions throughout the year.

Precipitation falls here during the summer, reaching an average of 1000 to 2000 mm per year, but at the end of the rainy season, drought sets in sharply, and there is practically no rain during the winter. Variably humid forests are home to significantly more mammals, deer, many rodents, monkeys and felines live here. There are many birds in the trees. The soils here are also ferralitic, but predominantly red. With a decrease in the amount of rain, the concentration of humus in them increases.

Alternately humid forests, as well as equatorial forests, are threatened by man. The restoration of these forests is possible, however, it will take a long time, so it is necessary to think about their rational use.

Variably moist forests wikipedia
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Permanently humid equatorial forests. There are 3 arrays along the equator:

Forests of the Amazon (South America), the northern coast of the Gulf of Guinea and about. Madagascar (Africa), Southeast Asia, New Guinea, Malay Peninsula, southern Philippines.

Also, permanently humid forests can be found in the subtropical and tropical zones, due to the fact that there are high temperatures throughout the year and the territory is constantly under the influence of the trade winds.

These territories are: Northern coast of Australia, Eastern coast of Brazil, Western part of India.

Climate characteristic:

Rainfall - 1500-2000

Evaporation - 700-1200

High-Ivanov coefficient 1.5-3 (excessive moisture - more precipitation than evaporation)

Vegetation:

Phytomass – 650T/ha, Productivity – 40T/ha per year

There are 50-100 plant species per 1 ha.

Forests differ in tiers, are polydominant - several species of plants dominate on each tier. The upper tier - trees 50-60m (characterized by diversity), the middle - 20-30m (well developed and closed), the lower one is rather poorly expressed due to low radiation. Under the canopy of the forest, there is significant shading.

Soils: Greyolitic (yellow) soils are formed on powerful weathering slopes (20 m or more), have excessive moisture and leaching regime throughout the year.

Soils are poor in bases and humus (5.7cm), because there is a rapid decomposition of plant residues, but are rich in oxides of iron and aluminum.

Variably humid equatorial forests. They are located between the zone of permanently humid forests and the savannah. This is the wettest part of the subequatorial climate. Summer rains and a dry period are characteristic. The zone in Africa is presented from the north and south of the equator, the forests of the South.

America on the periphery of the Amazonian permanently humid forests, For the forests of Central America, in the east of about. Java, Bali, Also in the region of Hindustan (Bombay).

Climate characteristic:

Rainfall - 1200-1600

Evaporation - 1200-1400

Coefficient of High - Ivanov 1-1.2

The dry period can last up to 5 months, then evaporation is greater than the amount of precipitation, during rains precipitation> evaporation.

Vegetation:

Phytomass – 500T/ha, Productivity – 16T/ha per year

The tallest trees are 25-30m, layering is less pronounced than in constantly wet forests.

In the dry season, leaf fall is observed.

The shrub layer is better expressed than in variable-humid forests. Grasses appear in the herbaceous layer.

Soils: red feramide soils are formed. In the dry season, there is no leaching regime of soils + deciduousness + less decay = humus horizon 10-15cm. Humus is formed under conditions when the leaching regime is replaced by a non-leaching one.

Savannah landscapes.

Savannahs are called zones with a predominance of cereals in the subequatorial and tropical zones.

They are characterized by stand-alone trees.

There are 3 subzones of savannahs: wet savannahs, typical savannahs, deserted savannahs.

Savannahs are very widespread. In Africa, m / y deserts and variable-humid subequatorial forests, as well as in the east and south. South America - south of the Amazon, On the Caribbean coast (turn into woodlands), in the Orinoco Delta.

Sev. America - in the "rain shadow" of Central America and Mexico (Pacific Coast). Asia - the Hindustan Peninsula, in the interior of Thailand, Kombodia. Vast belts of savannas in Australia.

Climate characteristic:

Precipitation - 1000-1500 (for wet), 500-1000 (typical), 200-500 (desert)

Evaporation - 1500-2400 (for wet), 2400-3800 (typical), 3500-4200 (desert)

High-Ivanov coefficient 0.4-1; 02,-0.4; 0.02-0.2

Savannahs are characterized by alternating wet and dry seasons.

The maximum duration of the dry season is 10 months (in desert savannas). The minimum dry season is 3 months. Evaporation > amount of precipitation.

Vegetation:

Phytomass — 40T/ha (in typical); 15T/ha (in deserted),

Productivity - 12T/ha per year; 4t/ha per year

Characteristic sparse woody vegetation. This is due to the fact that plants compete for soil moisture.

There are areas of forests along the banks of rivers and lakes. For the savannas, a developed animal world with a large number of herbivores is typical.

Soils: Red feralite soils are common in wet savannahs. In typical and deserted - red-brown soils. All soils are formed in the process of non-leaching water regime. In humid savannahs, the humus horizon reaches 15 cm; towards desert savannahs, the humus horizon decreases.

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1) Variable rain forests grow south and north of the equatorial rain forests: in tropical Africa, America, Hindustan, Sri Lanka, Indochina, China, North and Northeast Australia.
3) They differ from their colder and drier counterparts in their red or reddish color and strong weathering of minerals.

In these areas, more than 1000 mm of precipitation falls annually in the form of rain (in some places more than 10 thousand mm), that is, a layer of water more than one meter thick.

Heat and moisture are the basis of lush vegetation, which injects organic acids into the soil all year round, and warm soil waters carry them to a great depth, dissolving the minerals of rocks. It is very important that the age of the surface layers of soil in the tropics and subtropics reaches hundreds of thousands and millions of years. With such strong and long weathering, most minerals and chemical elements are washed out and the most stable minerals remain in the soil - kaolinite, quartz, as well as a large amount of iron and aluminum oxides, for which they are called ferralite soils (from "ferrum" - "iron, aluminum" and "lithos" - "stone").

The most important iron oxides that give color to the soil are red hematite, as well as yellow limonite and brown goethite, which contain impurities of crystalline water. Differences in the color of the soils of the tropics and subtropics are also associated with the humidity of the climate and the degree of weathering of minerals.

The most humid soils of the equatorial zone are red-yellow soils (in the subtropical zone they are called krasnozems and yellow soils). In these forest soils, the litter and a small humus horizon give way to weathering horizons with red and yellow coloration. Heavily weathered, but variable wet soils of subequatorial tall grass savannahs are called red.

In them, the humus horizon is much thicker than in forest equatorial soils. In savannahs and hardwood forests, where it is still drier, the soils are less weathered, they have less red hematite and more brown goethite, therefore they are called red-brown and brown-red. Here the humus horizon is less dark in color and thinner, and calcium carbonates can appear in the soil profile.

The soils of the subtropical zone often represent, as it were, transitions between the red soils of low latitudes and the soils of the temperate zone. The wettest red and yellow soils are the closest soil
4) Among the plants of variable-moist forests, evergreen, coniferous and deciduous trees are distinguished. Evergreens include palm trees, ficuses, bamboo, all kinds of magnolia, cypress, camphor tree, tulip tree. Deciduous trees are represented by linden, ash, walnut, oak, maple. Of the evergreens, fir and spruce are often found.
5)
Among the plants of variable-moist forests, evergreen, coniferous and deciduous trees are distinguished.

Evergreens include palm trees, ficuses, bamboo, all kinds of magnolia, cypress, camphor tree, tulip tree.

Deciduous trees are represented by linden, ash, walnut, oak, maple. Of the evergreens, fir and spruce are often found. Other inhabitants of such a forest, chain-tailed monkeys, live mainly on trees. They are small in size and have a black and white color. As is clear from the name of the species, these monkeys are distinguished by a particularly tenacious tail. There are also many bats, fish and reptiles here. Note that about 2,000 species of fish live here, which is from the freshwater fauna of the whole world.
2) The climate there is very difficult, as the sun can shine and heavy rain can immediately begin.

It can rain very heavily and there is a lot of precipitation. For these forests, the most testing month is May. May is very hot, small rivers and small reservoirs dry up.

Landscapes of subtropical variable-moist forests and landscapes of broad-leaved forests of the temperate zone.

Landscapes of subtropical variable-humid (monsoon) forests are found on the eastern coasts of the continents. In Eurasia - eastern China, the southern part of Japan (to Tokyo), the south of South Korea. Here the monsoon forests are pronounced. Sev.

America is the southeastern United States. South America - the south of Brazil, the upper reaches of the Uruguay River. Africa - in South Africa (southeastern part, at the foot of the Dragon Mountains). Australia - m / y along the coast of the Tusman Sea and the Great Dividing Range; in northern New Zealand.

Climate characteristic:

Rainfall - 1000-1600

Evaporation - 750-1200

Coefficient High - Ivanov 1-1.5

Throughout the year, the amount of precipitation is greater than evaporation.

It rains in summer, there is little rain in winter. But in accordance with this, the decrease in evaporation occurs in proportion to the decrease in the amount of precipitation. Excess moisture all year round. This zone is analogous to humid equatorial forests, only with a different thermal and radiation background.

Vegetation:

Character-on polydominance - there are different types, a cat.

represent tree forests. These forests are forever green. Layering is developed, creepers are characteristic, grassy cover is developed. The fauna of Asia is diverse (a relic is a panda), many animals do not correspond to this zone. In the east of Asia, from the equator to the north, one natural zone replaces another: humid equatorial forests - subequatorial humid forests - subtropical forests - deciduous forests - taiga. This is due to the fact that the monsoon type of climate dominates here.

There is a mixing of types of zones, some penetrate into others.

All in. America exists coniferous forests, different. species of oaks, rich fauna.

South America - araucaria forests, hardwoods.

Soils: zheltozems and krasnozems are formed. Permanent decomposition of litter throughout the year, constant washing regime. Small humus horizon.

Temperate broadleaf forest zone in Zap. Europe is occupied by huge spaces (France, Ireland, Germany, etc.).

In Eurasia, there are 2 large tracts of broad-leaved forests - Zap. Europe (up to Scandinavia) and the Far East (North of Japan, Korea). All in. America - the Ohio River Basin, Fr. Michigan, in the upper reaches of the Missouri river. in Yuzh. America - south of the zone of hardwood forests. Australia - about. Tasmania, south Part of New Zealand.

Climate characteristic:

Rainfall - 600-1000

Evaporation - 500-1000

High-Ivanov coefficient 1-1.2.

Throughout the year, there is more precipitation than evaporation.

Vegetation:

Deciduous forests are formed, this is due to the negative. temperatures in winter when photosynthesis is not possible.

Under these conditions, in the north of the zone, a subtaiga zone is distinguished, where conifers are present in the upper tier, and broad-leaved species are present in the lower tier. Beeches, oaks, hornbeams grow in such forests.

Soils: Brown sandy soils are formed in coastal areas, sandy sulfur soils are formed in continental areas.

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Geographical location, natural conditions

In the subequatorial zone, due to seasonal precipitation and uneven distribution of precipitation over the territory, as well as contrasts in the annual course of temperatures, landscapes of subequatorial variable humid forests develop on the plains of Hindustan, Indochina and in the northern half of the Philippine Islands.

Variably humid forests occupy the most humid regions of the lower reaches of the Ganges-Brahmaputra, the coastal regions of Indochina and the Philippine archipelago, are especially well developed in Thailand, Burma, the Malay Peninsula, where at least 1500 millimeters of precipitation falls. On drier plains and plateaus, where the amount of precipitation does not exceed 1000-800 millimeters, seasonally moist monsoon forests grow, which once covered large areas of the Hindustan peninsula and southern Indochina (Korat Plateau). With a decrease in precipitation to 800-600 millimeters and a reduction in the rainfall period from 200 to 150-100 days a year, forests are replaced by savannahs, woodlands and shrubs.

The soils here are ferralitic, but predominantly red. With a decrease in the amount of rain, the concentration of humus in them increases. They are formed as a result of ferralitic weathering (the process is accompanied by the decay of most of the primary minerals, with the exception of quartz, and the accumulation of secondary ones - kaolinite, goethite, gibbsite, etc.) and humus accumulation under the forest vegetation of the humid tropics. They are characterized by low content of silica, high content of aluminum and iron, low cation exchange and high anion absorption capacity, predominantly red and variegated yellow-red color of the soil profile, very acid reaction. Humus contains mainly fulvic acids. Humus contain 8-10%.

The hydrothermal regime of seasonally humid tropical communities is characterized by constantly high temperatures and a sharp change in the wet and dry seasons, which determines the specific features of the structure and dynamics of their fauna and animal population, which noticeably distinguish them from communities of tropical rainforests. First of all, the presence of a dry season lasting from two to five months determines the seasonal rhythm of life processes in almost all animal species. This rhythm is expressed in the confinement of the breeding period mainly to the wet season, in the complete or partial cessation of activity during the drought, in the migratory movements of animals both within the biome under consideration and outside it during the unfavorable dry season. Falling into full or partial anabiosis is typical for many terrestrial and soil invertebrates, for amphibians, and migration is typical for some insects capable of flight (for example, locusts), for birds, bats and large ungulates.

Vegetable world

Variably humid forests (Figure 1) are similar in structure to hylaea, differing at the same time in a smaller number of species. In general, the same set of life forms, variety of vines and epiphytes is preserved. Differences are manifested precisely in the seasonal rhythm, primarily at the level of the upper tier of the forest stand (up to 30% of the trees of the upper tier are deciduous species). At the same time, the lower tiers include a large number of evergreen species. The grass cover is represented mainly by ferns and dicots. In general, these are transitional types of communities, in places largely reduced by man and replaced by savannahs and plantations.

Figure 1 - Variably humid forest

The vertical structure of humid subequatorial forests is complex. Usually there are five tiers in this forest. The upper tree layer A is formed by the tallest trees, isolated or forming groups, the so-called emergents, raising their “heads and shoulders” above the main canopy - a continuous layer B. The lower tree layer C often penetrates into layer B. Tier D is commonly called shrub. It is formed mainly by woody plants, of which only a few can hardly be called shrubs in the exact sense of the word, or rather, these are “dwarf trees”. Finally, the lower tier E is formed by grasses and tree seedlings. The boundaries between adjacent tiers may be better or worse. Sometimes one tree layer imperceptibly passes into another. Tree layers are better expressed in monodominant communities than in polydominant ones.

The most common teak forest, which is characterized by a teak tree. Trees of this species can be considered an essential component of the summer green forests of India, Burma, Thailand and the relatively dry regions of eastern Java. In India, where very small patches of these natural zonal forests still remain, ebony and marado or Indian laurel grow chiefly along with teak; all these species provide valuable timber. But teak wood, which has a number of valuable properties, is especially in great demand: it is hard, resistant to fungi and termites, and also reacts poorly to changes in humidity and temperature. Therefore, teak growers specially grow teak (in Africa and South America). The monsoon forests are best explored in Burma and Thailand. In them, along with teak wood, there are Pentacme suavis, Dalbergia paniculata, Tectona hamiltoniana, whose wood is stronger and heavier than teak wood, then giving bast fibers Bauhinia racemosa, Callesium grande, Ziziphus jujuba, Holarrhenia dysenteriaca with white soft wood used for turning and woodcarving. One of the bamboo species, Dendrocalamus strictus, grows in the shrub layer. The layer of grasses consists mainly of grasses, among which the bearded vulture predominates. Along the shores of estuaries and in other areas of the sea coast protected from storms, the muddy tidal strip (littoral) is occupied by mangroves (Figure 2). The trees of this phytocenosis are characterized by thick stilted roots, like thin piles extending from the trunks and lower branches, as well as respiratory roots sticking out of the silt in vertical columns.

Figure 2 - Mangroves

Extensive swamps stretch along the rivers in the tropical rainforest zone: heavy rains lead to regular high floods, and floodplains are constantly flooded in the floodplains. The marshy forests are often dominated by palm trees, and the species diversity is less here than in drier places.

Animal world

The fauna of the seasonally humid subtropical communities is not as rich as the fauna of the humid equatorial forests due to the dry period, which is unfavorable for animals. Although the species composition of various groups of animals in them is specific, at the level of genera and families, a great similarity with the gilea fauna is noticeable. Only in the driest variants of these communities - in light forests and thorny bushes - do species related to typical representatives of the fauna of arid communities begin to noticeably predominate.

Forced adaptations to drought contributed to the formation of a number of special animal species characteristic of this particular biome. In addition, some species of phytophagous animals are here more diverse in species composition than in Hylaea, due to the greater development of the herbaceous layer and, accordingly, the greater diversity and richness of herbaceous food.

The layering of the animal population in seasonally humid communities is noticeably simpler than in humid tropical forests. The simplification of layering is especially pronounced in light forests and shrub communities. However, this mainly concerns the tree layer, since the stand itself is less dense, diverse and does not reach such a height as in the hylaea. On the other hand, the herbaceous layer is much more pronounced, since it is not shaded so strongly by woody vegetation. The population of the litter layer is also much richer here, since the deciduousness of many trees and the drying of grasses during the dry period ensure the formation of a rather thick litter layer.

The presence of a layer of litter formed by leaf and grass decay ensures the existence of a trophic group of saprophages with a diverse composition. The soil-litter layer is inhabited by nematode roundworms, megacolocidal annelids, small and large nodule worms, oribatid mites, springtail springtails, cockroaches, and termites. All of them are involved in the processing of dead plant mass, but the leading role is played by termites already familiar to us from the fauna of giley.

Consumers of green mass of plants in seasonal communities are very diverse. This is determined primarily by the presence of a well-developed grass layer in combination with a more or less closed tree layer. Thus, chlorophytophages specialize either in eating the leaves of trees or in using herbaceous plants, many feed on plant sap, bark, wood, and roots.

Plant roots are eaten by larvae of cicadas and various beetles - beetles, gold beetles, dark beetles. The juices of living plants are sucked by adult cicadas, bugs, aphids, worms and scale insects. The green plant mass is consumed by caterpillars of butterflies, stick insects, herbivorous beetles - beetles, leaf beetles, weevils. Seeds of herbaceous plants are used as food by reaper ants. The green mass of herbaceous plants is eaten mainly by various locusts.

Numerous and diverse consumers of green vegetation and among vertebrates. These are terrestrial turtles from the genus Testudo, granivorous and frugivorous birds, rodents and ungulates.

The monsoon forests of South Asia are home to the wild chicken (Callus gallus) and the common peacock (Pavochstatus). In the crowns of trees, Asian necklace parrots (Psittacula) get their food.

Figure 3 - Asian ratuf squirrel

Among herbivorous mammals, rodents are the most diverse. They can be found in all tiers of seasonal tropical forests and light forests. The tree layer is inhabited mainly by various representatives of the squirrel family - palm squirrels and a large ratuf squirrel (Figure 3). In the terrestrial layer, rodents from the mouse family are common. In South Asia, large porcupine (Hystrix leucura) can be found under the forest canopy, Rattus rats and Indian bandicots (Bandicota indica) are common everywhere.

Various predatory invertebrates live in the forest floor - large centipedes, spiders, scorpions, predatory beetles. Many spiders that build trapping nets, such as large nephilous spiders, also inhabit the tree layer of the forest. Praying mantises, dragonflies, ktyr flies, predatory bugs prey on small insects on the branches of trees and shrubs.

Small predatory animals prey on rodents, lizards and birds. The most characteristic are various viverrids - civet, mongoose.

Of the large carnivores in the seasonal forests, the leopard is relatively common, penetrating here from the hylae, as well as tigers.

Variably moist forests grow in those areas of the Earth where precipitation in the form of rain does not fall all year round, but the dry season lasts a short time. They are located in Africa north and south of the equatorial rainforests, as well as in the northeast of Australia.

See geographical position zones of variable humid forests on the map of natural zones.

The life of variable humid forests is closely related to seasonal climatic changes: during the dry season, under conditions of moisture deficiency, plants are forced to shed their leaves, and during the wet season, again dress in foliage.

Climate. In the summer months, the temperature in the areas of variable-moist forests reaches 27 degrees Celsius, in the winter months the thermometer rarely drops below 21 degrees. The rainy season comes after the hottest month. Thunderstorms are common during the summer rainy season, overcast days can be observed for several days in a row, often turning into rain. During the dry season in some areas, rain may not fall for two to three months.

Variably humid forests are dominated by yellow earth and red earth soil. The structure of the soil is granular-cloddy, the humus content gradually decreases downwards, on the surface - 2-4%.

Among the plants of variable humid forests, evergreen, coniferous and deciduous trees are distinguished. Evergreens include palm trees, ficuses, bamboo, all kinds of magnolia, cypress, camphor tree, tulip tree. Deciduous trees are represented by linden, ash, walnut, oak, maple. Of the evergreens, fir and spruce are often found.

Animals.

The animal world of variable rainforests is rich and varied. Many rodents live in the lower tier, among large animals - elephants, tigers and leopards, monkeys, pandas, lemurs, all kinds of felines have found shelter among the branches of trees. There are Himalayan bears, a raccoon dog and a wild boar. A variety of birds is represented by pheasants, parrots, partridges and black grouse. Pelicans and herons are found on the banks of rivers and lakes.

Man has destroyed a significant part of the variable rainforests. Rice, tea bush, mulberry, tobacco, cotton, citrus fruits are grown on the site of cut down forests. It will take a long time to restore the lost areas of forests.