The tundra occupies such areas as the coastal outskirts of Greenland, the western and northern outskirts of Alaska, the coast of Hudson Bay, and some areas of the Newfoundland and Labrador peninsulas. In Labrador, due to the severity of the climate, the tundra reaches 55° N. sh., and in Newfoundland it drops even further south. The tundra is part of the circumpolar Arctic subregion of the Holarctic. The North American tundra is characterized by permafrost, highly acidic soils, and rocky soils. Its northernmost part is almost completely barren or covered only with mosses and lichens. Large areas are occupied by swamps. In the southern part of the tundra, a rich herbaceous cover of grasses and sedges appears. Some dwarf tree forms are characteristic, such as creeping heather, dwarf birch (Betula glandulosa), willow and alder.

Next comes the forest-tundra. It reaches its maximum size west of Hudson Bay. Woody forms of vegetation are already beginning to appear. This strip forms northern border forests in North America dominated by species such as larch (Larix laricina), black and white spruce (Picea mariana and Picea canadensis).

On the slopes of the Alaska mountains, lowland tundra, as well as on the Scandinavian Peninsula, gives way to mountain tundra and char vegetation.

In terms of species, tundra vegetation North America almost no different from the European-Asian tundra. There are only some floristic differences between them.

Coniferous forests temperate zone occupy most of North America. These forests form the second and last vegetation zone, which stretches across the entire continent from west to east and is latitudinal zone. Further to the south, latitudinal zonality is preserved only in the eastern part of the continent.

On the Pacific coast, taiga is distributed from 61 to 42° N. sh., then it passes through the lower slopes of the Cordillera and then spreads to the plain to the east. In this territory the southern border of the zone coniferous forests rises north to a latitude of 54-55° N, but then it descends back to the south to the territories of the Great Lakes and the St. Lawrence River, but only its lower reaches.<

Coniferous forests along the line from the eastern slopes of the Alaska mountains to the Labrador coast are distinguished by significant uniformity in the species composition of the species.

A distinctive feature of the coniferous forests of the Pacific coast from the forest zone of the east is their appearance and composition of species. So, the forest zone of the Pacific coast is very similar to the eastern regions of the Asian taiga, where endemic coniferous species and genera grow. But the eastern part of the continent is similar to the European taiga.

The “Hudson” eastern taiga is characterized by the predominance of fairly developed coniferous trees with a high and powerful crown. This composition of species includes such endemic species as white or Canadian spruce (Picea canadensis), Banks pine (Pinus banksiana), American larch, balsam fir (Abies balsamea). From the latter, a resinous substance is extracted, which finds its way into technology - Canada balsam. Although conifers predominate in this zone, there are still many deciduous trees and shrubs in the Canadian taiga. And in burnt areas, of which there are many in the Canadian taiga region, even deciduous trees predominate.

Deciduous tree species in this coniferous zone include: aspen (Populus tremuloides), balsam poplar (Populus balsamifera), paper birch (Betula papyrifera). This birch tree has white and smooth bark, which the Indians used to build their canoes. It is characterized by a very diverse and rich undergrowth of berry bushes: blueberries, raspberries, blackberries, black and red currants. This zone is characterized by podzolic soils. In the north they turn into soils of permafrost-taiga composition, and in the south they become soddy-podzolic soils.

The soil and vegetation cover of the Appalachian zone is very rich and diverse. Here, on the slopes of the Appalachians, rich broadleaf forests grow in species diversity. Such forests are also called Appalachian forests. These forests are very similar to the genera of East Asian and European forests, in which the dominant role is dominated by endemic species of noble chestnut (Castanea dentata), may beech (Fagus grandifolia), American oak (Quercus macrocarpa), red sycamore (Platanus occidentalis). A characteristic feature of all these trees is that they are very powerful and tall trees. These trees are often covered with ivy and wild grapes.

Introduction

Eurasia is the largest continent on Earth, with an area of ​​53,893 thousand square kilometers, which is 36% of the land area. Population - more than 4.8 billion people.

The continent is located in the Northern Hemisphere between approximately 9° and 169° West longitude, with some of the islands of Eurasia located in the Southern Hemisphere. Most of continental Eurasia lies in the Eastern Hemisphere, although the extreme western and eastern ends of the continent are in the Western Hemisphere. Contains two parts of the world: Europe and Asia.

All climatic zones and natural zones are represented in Eurasia.

A natural zone is part of a geographical zone with homogeneous climatic conditions.

Natural areas take their name from their native vegetation and other geographic features. The zones naturally change from the equator to the poles and from the oceans deep into the continents; have similar temperature and moisture conditions that determine homogeneous soils, vegetation, fauna and other components of the natural environment. Natural zones are one of the stages of physical-geographical zoning.

The main natural zones of the subequatorial and equatorial belts of Eurasia considered in the course work are the zone of variable humid forests, including monsoon forests, the zone of savannas and woodlands, and the zone of equatorial forests.

The zone of variable humid, monsoon forests develops on the plains of Hindustan, Indochina and in the northern half of the Philippine Islands, the zone of savannas and woodlands - on the Deccan Plateau and the interior of the Indochina Peninsula, humid equatorial forests - throughout the Malay Archipelago, the southern half of the Philippine Islands, the southwest the islands of Ceylon and the Malacca Peninsula.

The course work provides a detailed description of these natural zones, reflecting the geographical location, climate, soils, flora and its ecological features, animal population and its environmental features. A current topic is also developed - environmental problems of the equatorial and subequatorial belts of Eurasia. First of all, these include the deforestation of moist equatorial forests and the desertification of savannas under the influence of grazing.

Zone of variable humid, including monsoon forests

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 areas of the lower reaches of the Ganges-Brahmaputra, coastal areas of Indochina and the Philippine archipelago, and are especially well developed in Thailand, Burma, and the Malay Peninsula, where at least 1,500 millimeters of precipitation falls. On drier plains and plateaus, where precipitation does not exceed 1000-800 millimeters, seasonally wet 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 savannas, woodlands and shrubs.

The soils here are ferralitic, but predominantly red. As the amount of rain decreases, the concentration of humus in them increases. They are formed as a result of ferralite weathering (the process is accompanied by the decomposition 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 silica content, high aluminum and iron content, low cation exchange and high anion absorption capacity, predominantly red and variegated yellow-red color of the soil profile, and a very acidic reaction. Humus contains mainly fulvic acids. They contain 8-10% humus.

The hydrothermal regime of seasonally wet tropical communities is characterized by constantly high temperatures and a sharp change in wet and dry seasons, which determines the specific features of the structure and dynamics of their fauna and animal population, which significantly 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 timing of the breeding season mainly to the wet season, in the complete or partial cessation of activity during drought, in the migratory movements of animals both within the biome in question and outside it during the unfavorable dry season. Falling into complete or partial suspended animation is characteristic of many terrestrial and soil invertebrates, amphibians, and migration is characteristic of some flight-capable insects (for example, locusts), birds, chiropterans and large ungulates.

Monsoon forests are vast green areas with lush vegetation and rich wildlife. During the rainy season, they resemble equatorial evergreen forests. Found in subequatorial and tropical climates. They attract tourists and photographers with a variety of picturesque landscapes.

Description

Monsoon rainforests are most common in the tropics. Most often they are located at an altitude of 850 meters above sea level. They are also called deciduous because the trees lose their leaves during periods of drought. Heavy rains return them to their former richness and color. The trees here reach a height of twenty meters, the leaves on the crowns are small. Evergreen species and many lianas and epiphytes are common in the undergrowth. Orchids grow in the monsoon zone. They are found in the Brazilian coastal mountain ranges, the Himalayas, Malaysia, Mexico, and Indochina.

Peculiarities

Monsoon forests in the Far East are famous for their diversity of plants and animals. Warm and humid summers and an abundance of plant food create favorable conditions for the habitat of insects, birds, and mammals. Coniferous and broad-leaved trees are found here. Among the inhabitants of the forests, sable, squirrel, chipmunk, hazel grouse, as well as animals rare for the climatic zone of Russia were noticed. Typical inhabitants of monsoon forests are the Ussuri tiger, black bear, sika deer, wolf, and raccoon dog. There are many wild boars, hares, moles, and pheasants on the territory. Reservoirs subequatorial climate are rich in fish. Some species are protected.

Rare orchids grow in the humid forests of Brazil, Mexico, and Indochina. About sixty percent are sympodial species, well known among gardeners. The red-yellow soils of monsoon areas are favorable for ficus, palm trees, and valuable tree species. The most famous ones include teak, satin, tallow, and iron. For example, it is capable of forming a dark grove from its trunks. A huge banyan tree grows in the Indian Botanical Garden, which has almost two thousand (!) trunks. The crown of the tree covers an area of ​​​​twelve thousand square meters. Variably humid forests become the habitat of bamboo bears (pandas), salamanders, tigers, leopards, poisonous insects and snakes.

Climate

Which predominates monsoon forests? Winters here are mostly dry, summers are not hot, but warm. The dry period lasts three to four months. The average air temperature is lower than in the humid tropics: the absolute minimum is -25 degrees, the maximum is 35 with a “+” sign. The temperature difference ranges from eight to twelve degrees. A characteristic feature of the climate is prolonged rainfall in the summer and its absence in the winter. The difference between the two opposite seasons is huge.

Monsoon forests are known for their morning fog and low clouds. This is why the air is so saturated with moisture. By noon, the bright sun completely evaporates moisture from the vegetation. In the afternoon, a foggy haze forms in the forests again. High air humidity and cloudiness persist for a long period of time. In winter, precipitation also falls, but rarely.

Geography

IN subequatorial zone, due to large amounts of precipitation and its uneven distribution, high temperature contrast, monsoon forests develop. On the territory of Russia, they grow in the Far East, have a complex topography, and a rich flora and fauna. There are humid forests in Indochina, Hindustan, the Philippine Islands, Asia, North and South America, and Africa. Despite the long rainy seasons and prolonged drought, the fauna in monsoon forest zones is poorer than in humid equatorial zones.

The most pronounced phenomenon of monsoons is on the Indian continent, where a period of drought is replaced by heavy downpours, the duration of which can be seven months. This change in weather is typical for Indochina, Burma, Indonesia, Africa, Madagascar, northern and eastern Australia, and Oceania. For example, in Indochina and the Hindustan Peninsula, the dry period in forests lasts seven months (from April to October). Trees with large crowns and an irregular arch grow in vast monsoon areas. Sometimes forests grow in tiers, which is especially noticeable from above.

The soil

Monsoon wet soils are characterized by a red tint, granular structure, and low humus content. The soil is rich in useful microelements such as iron and silicon. There is very little sodium, potassium, magnesium, and calcium in moist soil. In Southeast Asia, yellow soils and red soils predominate. Central Africa and are characterized by dry black soil. Interestingly, as the rains stop, the concentration of humus in monsoon forests increases. A reserve is one of the forms of wildlife protection in an area rich in valuable plants and animals. It is in humid forests that many species of orchids are found.

Plants and fauna

Monsoon forests in the subequatorial climate of Hindustan, China, Indochina, Australia, America, Africa, and the Far East (Russia) are characterized by a diversity of fauna. For example, in Southeast Asia, teak trees are common in variable humid zones, as are Indochinese laurel and ebony. There are also bamboo, vines, butea, and cereals. Many trees in forests are highly valued for their healthy and durable wood. For example, teak bark is dense and resistant to destruction by termites and fungi. Sal forests grow at the southern foot of the Himalayas. In the monsoon regions of Central America there are many thorny bushes. The valuable jat tree also grows in humid climates.

In subequatorial climates, fast-growing trees are common. Palms, acacias, baobab, spurge, cecropium, entandrophragma, ferns predominate, and there are many other types of plants and flowers. The humid climate zone is characterized by a wide variety of birds and insects. Woodpeckers, parrots, toucans, and butterflies are found in the forests. Among the terrestrial animals found in monsoon woodland are marsupials, elephants, various representatives of the cat family, freshwater, amphibians, frogs, and snakes. This world is truly bright and rich.

The subequatorial climate zone is transitional and occurs in the northern and southern hemispheres, from the tropical zones.

Climate

In summer, in the zones of the subequatorial belt, the monsoon type of climate prevails, which is characterized by large amounts of precipitation. Its characteristic feature is the change of air masses from equatorial to tropical depending on the season of the year. In winter, dry trade winds are observed here.

The average monthly temperature varies between 15-32º C, and the amount of precipitation is 250-2000 mm.

The rainy season is characterized by high rainfall (almost 95% of the year) and lasts about 2-3 months. When tropical easterly winds prevail, the climate becomes arid.

Countries of the subequatorial belt

The subequatorial climate zone passes through the countries of: South Asia (the Hindustan Peninsula: India, Bangladesh and the island of Sri Lanka); Southeast Asia (Indochina Peninsula: Myanmar, Laos, Thailand, Cambodia, Vietnam, Philippines); southern North America: Costa Rica, Panama; South America: Ecuador, Brazil, Bolivia, Peru, Colombia, Venezuela, Guyana, Suriname, Guiana; Africa: Senegal, Mali, Guinea, Liberia, Sierra Leone, Ivory Coast, Ghana, Burkina Faso, Togo, Benin, Niger, Nigeria, Chad, Sudan, Central African Republic, Ethiopia, Somalia, Kenya, Uganda, Tanzania , Burundi, Tanzania, Mozambique, Malawi, Zimbabwe, Zambia, Angola, Congo, DRC, Gabon, as well as the island of Madagascar: Australia;

Natural zones of the subequatorial belt

Map of natural zones and climate zones of the world

The subequatorial climate zone includes the following natural zones:

• savannas and woodlands (South America, Africa, Asia, Oceania);

And woodlands are predominantly found in the subequatorial climate zone.

Savannas are mixed grasslands. The trees here grow more regularly than in the forests. However, despite the high density of trees, there are open spaces covered with herbaceous vegetation. Savannas cover about 20% of the Earth's land area and are often in the transition zone between forests and deserts or grasslands.

• altitudinal regions (South America, Africa, Asia);

This natural zone is located in mountainous areas and is characterized by climate change, namely a decrease in air temperature by 5-6 ° C as the altitude increases above sea level. In areas of high altitude, there is less oxygen and lower atmospheric pressure, as well as increased ultraviolet radiation.

• variable-humid (including monsoon) forests (South America, North America, Asia, Africa);

Variably humid forests, along with savannas and open forests, are mainly found in the subequatorial zone. The flora does not have a wide variety of species, unlike the equatorial rainforests. Since this climate zone has two seasons (dry season and rainy season), the trees have adapted to these changes and are mostly broad-leaved deciduous species.

• moist equatorial forests (Oceania, Philippines).

In the subequatorial zone, moist equatorial forests are not as widespread as in the equatorial zone. They are characterized by a complex forest structure, as well as a wide variety of flora, which is represented by evergreen tree species and other vegetation.

Soils of the subequatorial belt

This belt is dominated by red soils of variable rainforests and tall grass savannas. They are characterized by a reddish tint, granular structure, and low humus content (2-4%). This type of soil is rich in iron and has negligible silicon content. Potassium, sodium, calcium and magnesium are found here in negligible quantities.

Mountain yellow earth, red earth and lateritic soils are common in Southeast Asia. In South Asia and central Africa, black soils of dry tropical savannas are found.

Animals and plants

The subequatorial climate zone is home to fast-growing trees, including balsa trees and members of the cecropia genus, as well as trees that grow longer (more than 100 years), such as sweetenia and various species of entandrophragma. Gabonese mahogany trees are common in tropical rainforests. Here you can find baobab, acacia, various types of palm trees, milkweed and parkia, as well as many other plants.

The subequatorial climate zone is characterized by a variety of fauna, especially birds (woodpeckers, toucans, parrots, etc.) and insects (ants, butterflies, termites). However, there are not many terrestrial species, these include.

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 rain forests, as well as in northeastern Australia.

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

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

Climate. In the summer months, the temperature in areas of variable-humid forests reaches 27 degrees Celsius; in the winter months, the thermometer rarely drops below 21 degrees. The rainy season comes after the hottest month. During the summer rainy season there are frequent thunderstorms, and there may be continuous cloud cover for several days in a row, often turning into rain. During the dry period, some areas may not receive rain for two to three months.

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

Vegetation.

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

Animals.

The fauna of the variable humid forests is rich and diverse. The lower tier is home to many rodents, large animals include elephants, tigers and leopards; monkeys, pandas, lemurs, and all kinds of felines find refuge among the tree branches. There are Himalayan bears, raccoon dogs and wild boars. The variety of birds is represented by pheasants, parrots, partridges and black grouse. Pelicans and herons live on the banks of rivers and lakes.

Man has destroyed a significant part of the variable rain forests. In place of cleared forests, rice, tea bushes, mulberries, tobacco, cotton, and citrus fruits are grown. It will take a long time to restore lost forest areas.