Moist equatorial forests of savannas and woodlands. African savannas

Geographical location, natural conditions

Savannahs and light forests are typical of the subequatorial climate with a sharp division of the year into dry and rainy seasons. Savannahs are climatic regions characteristic of more elevated tropical countries with a dry continental climate. In Asia, the largest areas of the savannah and light forest zone are confined to the Deccan Plateau and the inner parts of the Indochina Peninsula.

A distinctive feature of the climate of the savannas is the alternation of dry and wet seasons, which take about half a year, replacing each other. The change of two different air masses is characteristic - humid equatorial and dry tropical. Monsoon winds, bringing seasonal rains, significantly affect the climate of the savannahs. Since these landscapes are located between the very humid natural zones of the equatorial forests and the very dry zones of the deserts, they are constantly influenced by both. But moisture is not present in the savannas long enough for multi-tiered forests to grow there, and dry "winter periods" of 2-3 months do not allow the savannah to turn into a harsh desert. "Winter" in the savannah is a dry and relatively cold period lasting two to three months. During this time, the trees shed their leaves, the grasses wither and dry up, and sometimes burn out. The contrast of day and night temperatures reaches 15-18 degrees Celsius. During this period, many rivers dry up, become shallow, and the groundwater level drops. "Winter" is replaced by "spring", when the flowering of still leafless trees and shrubs begins. The "summer" period - the most humid and rainy - lasts, as a rule, four to five months. The temperature drops, and the humidity increases, amounting to almost 90%. At this time, the trees open their leaves, grasses grow wildly, and the soil is filled with water. The rivers become full. Before the next "winter" there comes a short "autumn", when cereals and trees bear fruit, evaporation decreases. Nature is preparing for a new dry period.

The savannas are characterized by the dominance of red-brown and black merged soils. These soils are characterized by low humus content (1.5-3%). Soil reaction is close to neutral, they are saturated with bases. In some profiles, in the lower part, there are ferruginous concretions. The total thickness of the profile on leveled surfaces is 1.5-2 meters. Dark-colored (black) coalesced montmorillonite soils appear in relief depressions, in the area of ​​distribution of red-brown soils. Such combinations are especially widespread in the southern part of the Deccan Plateau.

Vegetable world

In the savannahs of Asia, there are trees and shrubs from legumes, myrtle, dipterocarp (Figure 1). Tree-shrub forms of savannas are characterized by a powerful root system that penetrates to a considerable depth even with a relatively small size of the aerial part, the presence of a thick crust on the trunks. The trees are often stunted, with winding, sometimes straight or curved trunks, with spreading crowns. The umbrella-shaped form of the crown is widespread. On the whole, savannah communities are comparatively poor in floristics and have little diversity in structure. Depending on the moisture conditions, the height of the herbage, the degree of its density, and the species composition of trees and shrubs vary. Grasses, which form the basis of savannah communities, are characterized by more or less pronounced xeromorphism, their vegetative parts are represented by dense tufts, and long rhizomes are developed. The size of plants, depending on moisture and soil conditions, varies quite significantly. The generative shoots of cereals that produce a large number of seeds reach a particularly high height. Woody vegetation gives way to formations of tall grasses: bearded man, alang-alang, wild sugarcane. In the summer the savannah turns green, in the winter it turns yellow. Solitary palms, banyans and acacias.

Figure 1 - Indian savannah

Animal world

The leading environmental factors that determine the existence of animals in typical tree-shrub and grass savannahs are the presence of one or two dry periods, the duration of which is up to six months, limited rainfall, the presence of a well-developed grass cover and the absence of a pronounced tree layer: separately growing trees or their groups are far apart. All this leads to the formation in animals of clearly expressed adaptations to endure an unfavorable period of drought (or two periods in the equatorial regions). The duration of anabiosis in many insects, amphibians, and some reptiles in these regions is much longer than in seasonally humid communities. Migrations of birds and migrations of large herbivores acquire a special scope.

The structure of the animal population is significantly simplified in comparison with seasonally wet forests and light forests.

In savannahs, termites play a leading role in the utilization of dead plant matter. It is here that the total population density of termites, the number and size of their above-ground structures reach their maximum values. In addition to termites, the processing of detritus in the savannahs is carried out by kivsyaki, cockroaches, crickets, dark beetles, larvae of goldfish, bronze beetles and other beetles, earthworms, and terrestrial mollusks.

In the Asian savannas, herbivores and ungulates are not as diverse as in Africa. Here they share these food resources with rodents and other phytophages. The most common in savanna woodlands is the large nilgai antelope (Boselaphus tragocamelus) (Figure 2), a kind of four-horned antelope (Tetraceros quadricornis), the males of which sometimes have two pairs of horns, and now the rare blackbuck antelope (Antilopa cervicagra) with spirally twisted horns grazes in open spaces .

Figure 2 - Nilgai Antelopes

Among the consumers of the green mass of plants in the savannahs, various insects are also represented: larvae (caterpillars) of butterflies, phytophagous beetles - beetles, bronze beetles, leaf beetles, gold beetles, reaper ants, cicadas and stick insects. The most numerous in this trophic group are locusts. Mass gregarious species capable of long-distance migrations are common for savannas and seasonal light forests. Among phytophagous birds, granivorous species of the Ploceidae family predominate, surpassing other groups of birds both in number and in species diversity.

The green parts of plants and seeds are used as food by lagomorphs and rodents.

Birds of the pheasant family (Phasianidae) are common in the savannas - francolins, guinea fowls, of which the helmet-bearing guinea fowl (Numida mitratd) is most common.

There are not many large predators in the South Asian savannahs. In addition to the Asiatic lion, now almost exterminated, jackals and striped hyenas are common in these savannahs.

The territory of the African continent between evergreen forests and semi-deserts and deserts can be called a zone of savannas and woodlands somewhat conditionally, with a very generalized, "small-scale" approach. Different biomes and classes of biocenotic formations are represented here.

The area is dominated by tall grass, typical and deserted savannahs. There are also woodlands and thorny forests and shrubs that are leafless during the dry season. The first three groups naturally replace each other when moving from the array of evergreen equatorial forests to the north, towards the Sahara.

They form bands parallel to each other, the almost ideal latitudinal extent of which is interrupted only to the east of the White Nile. In East Africa, all these three groups are also represented, although it is rather difficult to replace each other due to the features of the relief.

Here, park savannahs and light forests already have a greater share. On the Somali Peninsula, dry thorny forests and shrubs are widely represented. Tall grass savannahs and typical savannahs have been almost completely replaced south of the evergreen equatorial forests. Here the groupings follow in this order: woodlands, park savannahs, deserted savannahs. The latter already occupy the Kalahari region and gradually pass into the desert to the southwest.

On the High Veld plateau there are grasslands growing in a mild subtropical climate. For all their originality, they are in many ways close to the park savannah (its grassy areas).

The same can be said about some grasslands on the East African plateau.

A common feature of the conditions for the existence of these complexes is the periodicity in moistening at high year-round temperatures. During the dry season, less moisture always enters than evaporates, and during the wet season, vice versa. Therefore, the duration of the wet and dry periods is a stronger factor, more determining the nature of climax biocenoses, than the annual amount of precipitation.

Soil and hydrological (edaphic) conditions, which affect the moisture regime, are also of no small importance.

When comparing the territorial confinement of forests, light forests and savannahs with climatic indicators, the following can be noted.

Within the limits of the same moisture and temperature areas, one can meet completely different landscape-biogeographic complexes. Some of these examples are easily explained by local edaphic features. First of all, this applies to gallery forests, wetlands, uplands, in other words, to groups confined to river valleys, rifts, lake shores, poorly drained depressions, slopes of uplands, etc. However, there are still other cases where differences relate to upland groups.

It is precisely such examples, so far little studied, that are of particular interest from the point of view of the origin and development of biocenoses in the seasonally arid tropical regions of Africa.

Vegetation and flora. The wettest parts of the range of tall-grass savannahs with individual trees and groves are still found within the belt of humid equatorial forests.

This is the result of regressive succession of secondary communities. Along the periphery of evergreen forests, tall-grass savannahs and woodlands with a high grass cover become predominant. They are interspersed with areas of dense forest, mostly secondary, where there are deciduous species, but evergreens predominate.

This transitional, in some places very wide strip in West Africa, even in the most open typical tall-grass savannah regions, is a derivative that arose on the site of closed forests.

It owes its origin to slash-and-burn agriculture, followed by periodic burning of cereals during the dry period. The origin of this grouping is betrayed, in particular, by the presence of certain trees characteristic of the closed forest, such as the oil palm.

Outwardly, the so-called Guinean tall-grass wet savannas and savanna woodlands are extremely close to such derivative savanna woodlands and tall grass savannas.

The tree species here lose their leaves during the dry period, they are hardy to fires that occur regularly during the dry periods (or period) of the year. The characteristic tree of the Guinean savannah is considered to be the large-leaved butyrospermum from the Sapota family. Often no distinction is made between the two types of wet savannahs described, then the oil palm is considered as a characteristic element of the Guinean savannahs.

In West Africa, the most typical and common trees of the southern part of the tall-grass Guinean savannas are close to the types of evergreen forests. In similar climatic conditions, in addition, a few remains of deciduous light tropical forests have been preserved. They include many tree species, although floristically they are not as rich as hylei, their average height is lower, often only two tiers are expressed, crown density is less.

Mostly trees of the upper tier are deciduous, under its canopy many more evergreen plants are preserved.

Rare light-colored groupings exist in the Guinean zone, but they are little preserved. Most of the area is open space dominated by high grasses (elephant grass): pennisetums, bearded vultures, aristides. A plant such as the Guinean sansevier does not have an above-ground stem at all. From the rhizome, tall, sharp, hard leaves with a characteristic transverse stripe extend upwards.

This plant is often grown in our rooms. Frequent burning of dry grass destroys species of mature trees and young shoots unadapted to fire. Therefore, primary light tropical forests and light forests are almost everywhere easily replaced by tall grass savannah.

The Guinean tall grass savanna and miombo forests of the southern parts of the mainland are replaced by more arid areas. It is dominated by typical, or Sudanese, open-type savannas with individual trees or clumps of trees and shrubs.

The park savannas and woodlands of East and South Africa are very close to the Sudanese savannas. Of the trees, the baobab is typical. Representatives of the mimosa family with umbrella-shaped crowns, thinly dissected leaves become background: acacia, parkia. A doom palm with a branching trunk appears. Some species also penetrate from the Guinean savannah. A general view, for example, would be a lofira, which is usually lower here.

With frequent fires, the trunk of this plant can be almost destroyed, and then it looks like a grassy shrub, since the roots always give new shoots to replace the dead.

In southern Africa (Angola, Zambia, Malawi, Mozambique, part of Madagascar) the strip of park savannahs is in many respects also close to the sparse southern variants of miombo. Tree species are formed by deciduous (rain-green) trees. Species of legumes with pinnate foliage (brachystegia) and small-leaved umbrella species - acacias, albizia predominate.

The grass cover in the Sudanese savannah is lower than in the Guinean one. The composition of the species can be close, often bearded and aristids predominate. Geophytes are also characteristic - bulbous and rhizomatous plants from the families of lilies, amaryllis, etc.

During the dry season, in most grasses, the above-ground organs dry up, and trees and shrubs shed their leaves.

The floristically sharply depleted Sahelian, or deserted, savannahs border the Sahara, with a predominance of acacia tree species.

The ground cover consists mainly of turf grasses with the participation of ephemeroid geophytes. It is rare, unclosed, in some places it disappears altogether. Because of this, fires cannot have a strong impact on the appearance and species composition of phytocenoses.

But it is the Sahelian savannah that is most sensitive to grazing and trampling by livestock. Therefore, here the vegetation cover is strongly changed.

In sparsely populated areas, thorny light forests with shrubs can develop. The villages are characterized by the doom palm and the date palm. "Under close moistening conditions, but with two short wet and two long dry periods in Somalia and eastern Ethiopia, thorny low-growing forests and shrubs are common with the participation of succulents - tree-like spurges, aloe, etc.

The South African desert savannas in the Kalahari region have a similar character, they gradually become more sparse and give way to the desert. Floristically, the last two groups are richer than the Sahelian savanna - there are more species related to other tropical plants of the continent.

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The zone of savannas and light forests occupies the Guiana and Brazilian plateaus and the Orinok lowland. Here, as elsewhere in the subequatorial belt, there are dry and wet seasons. The savannahs of the Northern Hemisphere, called llanos, have a longer rainy season. Therefore, there are more trees here than in the savannahs of the Southern Hemisphere, which are called campos.

In campos, among the herbs, there are separately growing cacti, spurges, mimosas, in llanos - different types of palms. The soils are red ferrallitic and red-brown.

In the river valleys, evergreen gallery forests grow, which, in terms of the composition of vegetation and wildlife, resemble tropical rainforests. The farther from the Atlantic Ocean, the more the vegetation of the savannas changes.

In the west, they pass into the shrub savannah, where a very hard quebracho tree is found.

The fauna of the savannas of South America is much poorer than that of Africa. There are no large herds of ungulates here. Of the herbivores, there are small deer, tapirs, baker pigs, of predators - the jaguar and puma. The local "orderly" is an armadillo that feeds on carrion, and in case of danger quickly rolls up into a ball and burrows into the ground.

The anteater feeds on termites. The largest bird in the savannas is the rhea, which resembles an ostrich in appearance.

The savannas of the southern hemisphere have been greatly altered by human activities.

The vegetation of the savannas was replaced by plantations of coffee and peanuts, which are native to the local savannas. Large areas are also occupied by cities and mining areas.

Russia in the poem dead souls

Savannahs and woodlands

Savannah is a vast expanse in the tropical zone, with intermittent precipitation, covered with grassy vegetation with sparsely scattered trees and shrubs. The most common savannas are in central Africa. The main mass of plants of the cereal savannah are cereals that reach a great height (up to). The savannahs in the Orinoc lowland are called llanos, in Brazil they are called campos.

Savannah is a zonal type of landscape in tropical and subequatorial climatic zones.

In this natural zone, the change of the wet and dry seasons is clearly expressed at consistently high air temperatures (from + 15°С to + 32°С). As you move away from the equator, the period of the wet season decreases from 8-9 months to 2-3, and precipitation - from 2000 to a year. The violent development of plants in the rainy season is replaced by droughts of the dry period with a slowdown in the growth of trees, grass burning out. Some plants are able to store moisture in the trunks (baobabs, bottle tree).

The savannah is characterized by the predominance of grassy cover, among which high (up to) cereals dominate. Shrubs and solitary trees rarely grow among them, the frequency of which increases towards the equator.

Of the woody vegetation on different continents, palm trees, a variety of acacias, tree-like cacti are found here.

Savannah soils depend on the length of the rainy season.

Closer to the equatorial forests, where the rainy season lasts 7-9 months, red ferrallitic soils form. Where the duration of the rainy season is less than 6 months, typical red-brown savannah soils are common. On the borders with semi-deserts, where scarce rains fall for only 2-3 months, unproductive soils with a thin layer of humus are formed.

The dense and tall grass cover provides abundant food for the largest animals, such as elephants, giraffes, rhinos, hippos, zebras, antelopes, which in turn attract such large predators as lions, hyenas and others.

The world of birds in the savannas is rich and diverse. A small beautiful bird lives here - a nectary, the largest birds on Earth are ostriches. Of the predatory animals, the secretary bird with long legs stands out for its appearance and habits.

She hunts for small rodents, reptiles. There are many termites in the savannah.

Savannahs are located mainly in the Southern Hemisphere from 30 ° to 5-8 ° south latitude. In the Northern Hemisphere, they cross Africa, forming a transition zone directly south of the Sahara - the Sahel. Most of the savannas are in Africa. Here they occupy about 40% of the continent.

Savannahs in northern South America are called llanos (Spanish.

llanos - plural of "plain"), and on the Brazilian plateau - campos (port, satro - field). This is an area of ​​intensive animal husbandry in Brazil.

Savannas play a very important role in human economic life. Significant areas are plowed up here, cereals, cotton, peanuts, jute, sugar cane and others are grown.

Animal husbandry is developed in drier places. Some species of trees growing in savannahs are used by humans for their own purposes.

So, teak wood gives solid valuable wood that does not rot in water.

Anthropogenic impact on savannahs often leads to their desertification.

Literature.

1. Barkov A.S. Dictionary-reference book on physical geography / A.S. Barkov. - M .: State. study.-teacher. Publishing House of the Ministry of Education of the RSFSR, 1948. - 304 p.
2. Student's handbook.

   Geography / Comp. T.S. Mayorova. - M .: Philologist. Society "Slovo", Center for the Humanities. Sciences at the faculty of journalism of Moscow State University. M.V. Lomonosov, TKO "AST", 1996. - 576 p.

See details:

1. Savannah of Australia.
2. African savannas.
3. Savannas of South America.

The concept, essence, geographical location of the savannah and woodlands. Climatic features of the territory, characteristics of flora and fauna.

Description of the process of formation and development of agriculture on the territory of the savannah and woodlands.

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

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savannah

1. Geographical position
2. Animal world
3. plant world

Geographical position

Savannah covers almost 40% of the surface of the African continent. They are located around evergreen equatorial forests.

To the north, it borders the Equatorial Forests of the Guinea-Sudanese Savannah, which stretches for 5,000 kilometers from the western coast of the Atlantic Ocean to the eastern shores of the Indian Ocean.

From the Tana rivers in Kenya, the saunas extend across southern Africa to the Zambezi River valley, and then turn west for 2,500 miles down the Atlantic coast.

Animal world

The African savannah is a completely unique phenomenon in terms of the diversity of large animals.

Nowhere else in the world can you find such an abundance of wildlife.

At the end of the 19th century, the savannas did not threaten the savannas. But at the beginning of the 20th century, with the advent of European colonialists armed with firearms, large-scale shooting of herbivores began.

Countless herds that began to plummet over large areas of animal savannah. Their number has been reduced to a minimum.

He found a compromise between human economic activity and the unique diversity of the animal world.

And he embodied in the creation of national parks in the savannah. There are many predators: leftists, cheetahs, hyenas, leopards.

From herbivorous animals live the zebra, the blue-beast, the gazelle, the Impala, the giant heavyweights of the antelope. The rare Oryx antelope can also be found in the Kudu Savannah bushland. The real pearl of the African savannah are elephants and giraffes.

plant world

The vegetation cover of these places is rich and varied. Savannah is located in the sub-equatorial zone during the nine months of the rainy season, which contributes to the intensive growth of various plants.

Baobab is a typical representative of the tree world.

The tree trunk of this tree is saturated with moisture, which allows the Baobab to survive even during heavy fires during the drought period. There are also various palm trees, mimosa, acacia, spaghetti bushes.

They are found, as a rule, in subequatorial belts. These zones are found in both hemispheres. But sections of the savannah can be found in the subtropics and tropics. This zone is characterized by a number of features. The climate in the savannah is always seasonally humid. There is a clear change of periods of drought and rain. It is this seasonal rhythm that determines all natural processes. Woodlands and savannahs are characterized by ferrallitic soils. The vegetation of these zones is sparse, with isolated groups of trees.

Savanna climate

Savannahs and light forests have climatic features. First, it is a clear, rhythmic change of two periods: drought and heavy rains. Each of the seasons, as a rule, lasts about six months. Secondly, the savanna is characterized by a change in air masses. Wet equatorial comes after dry tropical. The climate is also affected by frequent monsoon winds. They bring seasonal heavy rains with them. Savannahs are almost always located between the dry zones of deserts and humid equatorial forests. Therefore, these landscapes are constantly influenced by both zones. At the same time, it is important to note that moisture does not last long enough in these areas. Therefore, multi-tiered forests do not grow here. But even relatively short winter periods do not allow the savannah to turn into a desert.

Savannah soils

The savannah and light forests are characterized by the predominance of red-brown, as well as merged black soils. They differ primarily in the low content of humus masses. Soils are saturated with bases, so their pH is close to neutral. They are not fertile. In the lower part, in some profiles, ferruginous concretions can be found. On average, the thickness of the upper earthen layer is approximately 2 meters. In the area of ​​predominance of red-brown soils, dark-colored montmorillonite soil appears in places where the relief is lowered. Especially often such combinations can be found in the Deccan plateau in its southern part.

savannas of australia

The savannas and woodlands of Australia occupy a significant area of ​​the mainland. They are concentrated in the northern part of the continent. They also occupy large areas on the island of New Guinea, capturing almost the entire southern part. The Australian savannah is different. It is neither African nor South American. During the rainy season, its entire territory is covered with bright flowering plants. It is dominated by the ranunculus, orchid and lily families. Cereals are also often found in this zone.

Woody plants are also characteristic of the Australian savannah. Primarily eucalyptus, casuarina and acacia. They are concentrated in separate groups. Casuarinas have very interesting leaves. They consist of individual segments and resemble needles. In this area there are also interesting trees with thickened trunks. In them, they accumulate the necessary moisture. Because of this feature, they are called "bottle trees". The presence of such peculiar plants makes the Australian savanna unique.

African savannas

African savannahs and woodlands are bordered by tropical forests from the north and south. The nature here is unique. In the border zone, forests gradually thin out, their composition becomes noticeably poorer. And a patch of savannah appears in the midst of a continuous forest massif. Such changes in vegetation occur due to the shortening of the rainy season and the increase in the dry season. As you move away from the equatorial zone, the drought becomes longer and longer.

There is an opinion supported by facts that such a wide distribution of tall-grass savannahs, which are replaced by mixed deciduous and evergreen forests, is directly related to human economic activity. For quite a long time, vegetation was constantly burned in these territories. Therefore, the inevitable disappearance of the closed tree layer occurred. This contributed to the arrival of numerous herds of hoofed mammals to these lands. As a result, the restoration of woody vegetation has become almost impossible.

Savannas and woodlands of Eurasia

On the territory of Eurasia, savannahs are not common. They are found only in most of the Hindustan peninsula. Also, woodlands can be found on the territory of Indochina. Monsoon climate prevails in these places. In European savannahs, lone acacias and palm trees grow mainly. Grasses are usually tall. In some places you can find patches of forest. The savannahs and woodlands of Eurasia differ from those of Africa and South America. The main animals in these territories are elephants, tigers, antelopes. There is also an abundance of different types of reptiles. Rare areas of forests are represented by deciduous trees. During the dry season, they shed their leaves.

Savannahs and Woodlands of North America

The savannah zone in North America is not as widespread as in Australia and Africa. The open spaces of woodlands are mainly occupied by grassy herbaceous species. Tall grass alternates with small scattered groves.

The most common tree species that characterize the savannas and woodlands of North America are mimosa and acacia. During the dry season, these trees shed their foliage. The grasses dry up. But during the rainy season, the savannas bloom. From year to year, the area of ​​woodlands only increases. The main reason for this is the active economic activity of man. Savannahs are formed on the site of a cut down forest. The fauna of these zones is much poorer than on other continents. Some species of ungulates, cougars, rodents and a large number of snakes and lizards are found here.

Savannas of South America

The savannas and woodlands of South America border on tropical forests. Due to climate change, which is associated with the appearance of a long dry season, these zones are moving into one another. On the highlands of Brazil, savannas are located in a significant part of it. They are concentrated mainly in the hinterland. Here you can also find a strip of almost pure palm forest.

Savannahs and woodlands also occupy large areas in the Orinok Lowland. They are also found in the Guiana Highlands. In Brazil, typical savannahs are better known as campos. The vegetation here is represented mainly by cereal species. There are also many representatives of the family Asteraceae and legumes. Tree forms are completely absent in places. In some places, you can still find remote areas of small thickets of mimosa. Tree-like cacti, spurges and other succulents and xerophytes also grow here.

brazilian caatinga

Savannahs and woodlands in the northeast of Brazil are represented by a sparse forest, in which predominantly drought-resistant shrubs and trees grow. This area is called "Caatinga". The soils here are red-brown. But more interesting are the trees. In the dry season, many of them shed their leaves, but there are also species that have a swollen trunk. In it, the plant accumulates a sufficient amount of moisture. These species include, for example, a vatochnik. Caatinga trees cover vines and other epiphytic plants. There are also several types of palm trees in these areas. The most famous of these is the carnauba wax palm. Vegetable wax is obtained from it.

Theme 1. Africa

§ 15. Savannas and woodlands

Remember: 1. How are soils formed? What determines their fertility? 2. What are food chains in an ecosystem?

Climatic conditions. Savannahs and woodlands are the largest area in Africa, occupying about 40% of its territory. They resemble grassy steppes with trees and shrubs that grow singly or in small groups.

Savannas formed mainly in the subequatorial climatic zone, which is characterized by two seasons - dry and wet.

In the savannas, in the direction from the equator to tropical deserts, the duration of the dry season is growing - from 3 to 9 months a year. During this time, it rains only occasionally. When the rainy season begins, the dusty yellow-black edge turns into a wonderful green park. Gray from the smoke of fires and dust, the air becomes transparent and clean. The first tropical downpours after a drought are amazing. It's always hot before it starts to rain. And then a cloud appears in the sky, a roar of thunder is heard, and finally a downpour begins. Closer to the equator, the rainy season is longer (up to 9 months a year), closer to the tropics it is shorter (only 3 months). When there is a drought in the Northern Hemisphere, it rains in the Southern Hemisphere.

Determine what major landforms are occupied by the zone of savannahs and light forests on the mainland.

In the rainy season, grasses grow quickly, trees become leafy. With the onset of the dry season, the grasses burn out, some types of trees shed their leaves and the savannah turns yellow, and after the fire - black.

Soils and vegetation. In contrast to the nutrient-poor red-yellow ferrallitic soils of the humid equatorial forest, savannah soils contain more humus, since plant residues decompose slowly during the dry period. Red ferralitic soils have formed on the border with forests. Further, they are replaced by red-brown soils, which, closer to the deserts, gradually turn into less fertile reddish-brown soils.

The vegetation of the savannas is not as rich as in the humid equatorial forests, but it is also impressive in its diversity. However, with distance from the equator, it gradually becomes depleted due to the increase in the duration of the dry season. Thus, tall-grass savannahs formed closer to the zone of variable-humid forests. There is a high and dense grass cover, more trees, among which are the shea butter tree, the doum palm. A tall, almost 5-meter, elephant grass grows. Gallery forests stretch in narrow strips in the river valleys.

The farther north and south, the poorer the vegetation. This savannah is called typical, or dry. It doesn't rain here for six months. The grass is already lower (1 - 1.5 m); among the trees - several species of acacias with a dense crown in the form of umbrellas, as well as tree-like euphorbia. The baobab also grows here (Fig. 27), which is also called the monkey, or breadfruit, tree.

Baobab is one of the sacred symbols of Africa. The tree lives 4-5 thousand years. This is one of the thickest trees on the planet - the trunk reaches 45 m in girth. The height of baobabs usually does not exceed 25 m. During the rainy season, the tree turns green, and during the drought sheds leaves to retain more moisture. Baobabs don't burn. Their trunks, almost hermetically protected by thick gray bark, contain up to 120 liters of water. Baobab uses moisture sparingly even in the rainy season. The fruits of the tree ripen at the beginning of the dry season, monkeys willingly feast on them.

On the border with semi-deserts, deserted savannahs are formed, where grasses and trees are adapted to dry weather, which prevails here most of the year. Soddy cereal grasses, thorny bushes, milkweeds and aloe predominate.

Rice. 27. Baobab

How are savannah plants adapted to the long dry season?

If the dry season lasts more than 8-9 months, then some of the trees die. bushes take their place. Such a savanna becomes like a desert. In northern Africa, on the border with the Sahara, it is called the Sahel (Arab, edge), and in South Africa - bush (English bush - bush).

Animal world. Only in the African savannas can you see so many giant herbivores. They all roam the savannas in search of food and water. Animals make especially large transitions during the dry period.

The African elephant (ill. 28) is the largest of the modern land animals. The length of his body reaches 7 m, and the mass of adult males is 5-7 tons. Since grassy food is low in calories, an elephant needs 100-300 kg per day. Every day the animal drinks 100-200 liters of water. In the past, these giants were mercilessly exterminated for ivory (the so-called elephant tusks). Now they need protection.

The tallest animal on the planet, the giraffe, also lives in the savannas of Africa. Its height reaches 5-7 m. So the animal has adapted to get leaves from the highest trees. Despite the long neck, the giraffe is able to jump high. However, due to high blood pressure, can not run for a long time.

Buffaloes, various antelopes, zebras keep in large herds. Predatory animals constantly lie in wait for them: lions, cheetahs, leopards - and their constant companions - jackals, hyenas and vultures, feeding on scraps left by large predators. These are the natural "orderlies" of the savannah.

There are many omnivorous animals in the savanna: rhinos, hippos and crocodiles.

The largest bird on the planet lives here - the African ostrich, which reaches 2-2.5 m (Fig. 29). He doesn't fly, but he runs well. The local population harnesses the birds to small carts to transport mail.

Among other birds, the marabou with a huge beak and the secretary bird of prey stand out.

In Africa, there are many reptiles, various types of snakes, pythons. Among the insects, the most common are ants and termites, which build tall buildings of various shapes. Together with numerous soil microorganisms, they often complete the food chain in the savannah ecosystem.

Rice. 28. African Elephant

Rice. 29. African ostrich

Think about the crop and livestock industries that are common in the savannah zone.

Now most of the savannah area is plowed up and used for growing crops, as well as for grazing livestock. Natural savannahs have been preserved in a few places, as well as in reserves and national parks.

Briefly about the main thing!

Savannahs and woodlands occupy the largest area in terms of area among the natural zones of Africa. They are located in both hemispheres mainly within the subequatorial climatic zone. Therefore, in this zone there are two seasons - dry and wet.

The soils of the savannah are more fertile than the soils of moist equatorial forests. They vary from red feralites near the equator to red-brown and reddish-brown soils in the desert region.

The vegetation of the savannas is diverse. Herbs dominate. Among the most famous trees are baobab, umbrella acacia, euphorbia, aloe. All plants are adapted to a long dry season.

The fauna of the savannas is also diverse. Especially a lot of ungulates. They are hunted by lions, cheetahs, leopards. African elephant, giraffe, hippopotamus, rhinoceros, African ostrich stand out for their size.

1. What features does the climate of the natural zone of savannahs and light forests have?

2. What are the main types of savannah soils. Why are they more fertile than soils in the zone of moist equatorial forests?

3. Compare the vegetation of the savannah zone and humid equatorial forests.

4. Name the most famous herbivorous, carnivorous and omnivorous animals of the savannas.

5. Make several food chains in the African savannah ecosystem.

6. Compare the different types of African savannas: tall grass, typical and deserted.

Savannahs and light forests are specific natural zones that are located only in certain climatic zones. What features do they have?

Location

The natural zone of savannas and light forests is located in the subequatorial belts of the Northern and Southern hemispheres. They occupy almost 40% of the territory of Africa, northeast Asia, there are separate areas in Australia. The plan for describing the natural zone of the savannah includes climate, soil, flora and fauna.

Rice. 1. There are savannahs on almost all continents.

Climate

Climatic features determine the development of flora and fauna of natural areas. The climate of the savanna and light forest zone is seasonally humid. There is a clear change of periods of rains and droughts. This is due to the trade wind-monsoon air circulation.

Closer to the equator, the rainy season lasts up to 9 months. As you move away from the equator, the rainy period is reduced to 3 months.

These areas are also characterized by slight seasonal temperature fluctuations. In summer, the rainy season begins here - the most favorable time for the steppe. The herbaceous cover is growing rapidly, animals are returning from their places of migration. In winter, the savannah is very dry, and the air temperature is about 21 degrees Celsius. In the dead of winter, the savannas are prone to frequent fires.

The soil

The characteristics of the soil of savannahs and light forests are associated with the rainfall regime. In the immediate vicinity of the equator are red ferralitic soils. As you move away from it, red-brown soils typical of savannahs appear. Closer to the deserts, the soil becomes very poor, with a small amount of humus.

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Flora

Savannahs and light forests, despite the not very favorable climate, are inhabited by different species of animals and birds. Among them you can find:

• elephants;
• lions;
• zebras;
• giraffes;
• armadillos;
• antelope;
• rhinos;
• ostriches;
• marabou.

All these animals and birds have adapted to the arid climate. But even they have to migrate to other areas when there is no water left in the savannah.

For many years, mankind exterminated these animals. Now there are fewer and fewer of them, reserves have been created for most species in order to preserve them in nature.

Rice. 2. Savannah wildlife

Fauna

The vegetation of savannahs and light forests is mainly herbaceous. It is represented by cereal plants, perennial grasses, shrubs. They grow rapidly in the savanna, occupying large areas of the territory.

Trees are rare and small. Often covered with creepers and lichen.

The most characteristic tree of the savannah is the baobab. It is a tree with a thick trunk and a broad, spreading crown that provides shade for the animals. In Africa, there is a gigantic baobab almost 200 meters high, its trunk is 44 meters thick.

Rice. 3. The main tree of the savannah is the baobab

What have we learned?

Savannahs and woodlands are natural areas with pronounced climatic fluctuations. The rainy season in the savanna can last from 3 to 9 months a year. Despite difficult weather conditions, savannahs are distinguished by a variety of flora and fauna.

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