Description of savanna woodlands and shrubs. Zone of savannas and woodlands. Concept, essence, geographical location of savannah and woodland. Climatic features of the territory, characteristics of flora and fauna. Description of the process of formation and

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Savannas and woodlands of Africa Flora and fauna Completed by: Nikita Antipov

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Description of the natural zone Savannah and woodlands are a typical natural zone for the subequatorial climate zone. Savannah is a tropical forest-steppe, located between tropical deserts and a zone of evergreen tropical forests. Savannas are characterized by a predominance of grass cover in combination with individual trees or groups of trees. Savannas and woodlands occupy 40% of the continent's area.

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Climate and map of climatic zones The natural zone of savannas and woodlands is characterized by trade wind-monsoon circulation of air masses, where dry tropical air dominates in winter, and humid equatorial air in summer. As you move away from the equatorial belt, the duration of the rainy season decreases from 8-9 months to 2-3 months per year. external borders zones. The annual amount of precipitation also decreases in the same direction (from 2000 mm to 250 mm per year). Also characteristic feature Savannahs have relatively small seasonal temperature fluctuations (from 15 to 32 degrees), but daily amplitudes can be significant, reaching 25 degrees. All these characteristic climatic features are reflected in all components natural environment savannas and woodlands.

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Climatic features In savannas and woodlands, two seasons of the year are clearly expressed: Dry Wet

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Soil Savannah soils directly depend on the duration of the rainy season and are characterized by a leaching regime. Closer to the equatorial forests, where this season lasts up to 9 months, red ferrallitic soils are formed. In areas where the rainy season is less than 6 months, typical savannah red-brown soils are characteristic, and on the borders with semi-deserts the soils are unproductive and thin layer humus.

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Flora Savannah vegetation has adapted to the dry continental climate and long droughts and has a strongly xerophytic character. All grasses usually grow in tufts. The leaves of cereals are dry and narrow, hard and covered with a waxy coating. The foliage on the trees is small, protected from excessive evaporation. Many species are distinguished by a high content of essential oils. In savannas, tall grasses grow up to 3 meters. Trees, such as acacias and baobabs, grow here alone or in separate groups.

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Baobab Baobab is rightfully considered one of the symbols of Africa. This tree lives for 4-5 thousand years, its height rarely exceeds 25 m, but its girth is up to 40 m. Baobabs are not afraid of fires, but their enemies are elephants. They eat wet bark. Monkeys feast on the fruits of the tree. In a trunk up to 10 m thick, the baobab stores water: its soft wood, like a sponge, can accumulate up to 120 tons of water. The tree can lose weight and gain weight.

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Acacia Umbrella acacia. Branched acacias rise like huge umbrellas among the tall grasses. More common are Senegalese, whitish, giraffe acacia and other species. Due to its crown, which has a flattened shape, the acacia is called umbrella-shaped. The adhesives contained in the bark are widely used in industry, and the wood is used to make high-quality expensive furniture.

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Animal world The fauna of the savannah is a unique phenomenon. No other corner of the planet has such an abundance of large animals. Before the arrival of white colonizers, countless herds of herbivores roamed the expanses of savannas, moving from place to place in search of watering places. They were followed by numerous predators (lions, cheetahs, hyenas, etc.), and the predators were followed by carrion eaters (jackals and vultures). However, over time the situation has changed radically. The construction of roads, cattle breeding and plowing of large areas, and steppe fires have put wild animals in distress. The salvation was the creation of numerous reserves where hunting and all economic activities are prohibited. Herds of gazelles, antelopes, zebras and buffaloes eat and trample grass vegetation, preventing bushes from settling. It is thanks to these animals that the savanna has its characteristic “park look”. Among the many species of ungulates, the most numerous are wildebeest; next to them you can always find small herds of African horses - zebras.

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Large animals The fauna of the savannah in this region is represented mostly by herbivorous representatives of the fauna: Giraffes Zebras Antelopes Rhinoceroses African elephants Hippopotamuses

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Insectivores and reptiles with birds The fauna of the savannah and woodlands is rich in representatives of reptiles: Pythons Chameleons Vipers Lizards Rivers and lakes are inhabited by crocodiles, and from the avifauna one can distinguish ostriches, hammer-headed herons and tiny sunbirds. In the South African sub-region, which is not so rich in vegetation, fur-covered insectivores - golden moles - are abundant, as well as kaffir striders, slightly reminiscent of jerboas.

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Predators Cheetah The large cat cheetah is the fastest predator on the planet. It can reach a speed of 110 km per hour. When running, a cheetah relies not on three, but only on two paws - this explains its seemingly flying movements. In the vast expanses of the savannah, the animal is required to be strong or to be fast. Speed is the key to being able to catch up with your prey or stay alive while fleeing. The cheetah is both strong and amazingly fast. Its speed and flexibility allow it to catch up and overcome even stronger, but less agile prey, such as an antelope or zebra. The coloring of the cheetah - yellow-fawn with black spots - allows it to hide in thickets of dense grasses and sneak up on its prey unnoticed.

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Seasonal migration of animals In winter, when drought sets in, the savanna dries out, turning into a lifeless, dried-out steppe. Animals migrate to areas where there is still a sufficient amount of water, however, at this time it is still too little. Heat and drought - very difficult conditions even for animals adapted to this climate. When the drought finally ends and summer begins, the rainy season suddenly begins. The dried-out savannah blossoms and fills with greenery, as if by magic. Herds of zebras, elephants and antelope are returning to gain strength before the next drought

Geographical location, natural conditions

Savannas and woodlands are typical of a subequatorial climate with a sharp division of the year into dry and rainy seasons. Savannas are climatic regions characteristic of more elevated tropical countries with a dry continental climate. In Asia, the largest areas of savannah and woodland zones are confined to the Deccan Plateau and the interior of the Indochina Peninsula.

A distinctive feature of the savannah climate is the alternation of dry and wet seasons, which take approximately six months, replacing each other. Characterized by the alternation of two different air masses - humid equatorial and dry tropical. The monsoon winds, which bring seasonal rains, significantly influence the climate of the savannas. Since these landscapes are located between the very wet natural zones of equatorial forests and the very dry zones of deserts, they are constantly influenced by both. But moisture is not present long enough in savannas for multi-story forests to grow there, and arid ones winter periods"in 2-3 months they 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, trees shed their leaves, grasses wither and dry out, and sometimes burn out. The temperature contrast between day and night reaches 15-18 degrees Celsius. During this period, many rivers dry up, become shallow, and the level groundwater goes down. “Winter” gives way to “spring”, when leafless trees and shrubs begin to bloom. The “summer” period - the most humid and rainy - lasts, as a rule, four to five months. The temperature drops and the humidity increases, reaching almost 90%. At this time, trees open their leaves, grass grows wildly, and the soil fills with water. The rivers become full. Before the next “winter” there comes a short “autumn”, when cereals and trees bear fruit and evaporation decreases. Nature is preparing for a new dry period.

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

Vegetable world

The savannas of Asia include trees and shrubs of legumes, myrtaceae, and Diptera (Figure 1). Tree and shrub forms of savannas are characterized by a powerful root system, penetrating to a considerable depth even with a relatively small size of the above-ground part, and the presence of a thick crust on the trunks. The trees are often low-growing, with twisting, sometimes straight or curved trunks, with spreading crowns. The umbrella-shaped crown shape is widespread. In general, savannah communities are relatively floristically poor and poorly varied in structure. Depending on the moisture conditions, the height of the grass stand and the degree of its density change, and the species composition of trees and shrubs varies. The grasses that form the basis of savannah communities are characterized by more or less pronounced xeromorphism, their vegetative parts are represented by dense turf, and long rhizomes are developed. The size of plants varies quite significantly depending on moisture and soil conditions. The generative shoots of cereals, which produce a large number of seeds, reach especially high heights. Woody vegetation gives way to formations of tall grasses: bearded grass, alang-alang, wild sugar cane. In summer the savanna turns green, in winter it turns yellow. Single palms, banyans and acacias.

Figure 1 – Indian savanna

Animal world

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

The structure of the animal population is significantly simplified compared to seasonally wet forests and woodlands.

In savannas, termites play a leading role in the disposal 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 savannas is carried out by cockroaches, crickets, darkling beetles, larvae of golden beetles, bronze beetles and other beetles, earthworms, and terrestrial mollusks.

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

Figure 2 – Nilgai antelopes

Among the consumers of green mass of plants in savannas are various insects: butterfly larvae (caterpillars), phytophagous beetles - beetles, bronze beetles, leaf beetles, golden borers, harvester ants, cicadas and stick insects. The most numerous in this trophic group are locusts. Massive gregarious species capable of long-distance migrations are common to savannas and seasonal woodlands. Among phytophagous birds, granivorous species of the weaver family (Ploceidae) predominate, surpassing other groups of birds both in numbers and in species diversity.

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

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

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

Topic 1. Africa

§ 15. Savannas and woodlands

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

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

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

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

Determine what major landforms are occupied by the savannah and woodland zones on the mainland.

During the rainy season, grass grows quickly and trees become covered with leaves. With the onset of the dry season, the grasses burn out, some types of trees shed their leaves, and the savanna becomes yellow, and after the fire - black.

Soils and vegetation. Unlike the poor nutrients Red-yellow ferrallitic soils of the moist equatorial forest, savannah soils contain more humus, since plant residues decompose slowly during the dry period. Red ferrallite soils have formed at the border with forests. Then they are replaced by reddish-brown soils, which, closer to the deserts, gradually turn into less fertile reddish-brown soils.

The vegetation of 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 savannas formed closer to the zone of variable-humid forests. There is tall and thick grass cover here, more trees, among which are the shea butter tree and the doum palm. Tall, almost 5-meter tall, elephant grass grows. In the river valleys, gallery forests stretch in narrow strips.

The further north and south you go, the poorer the vegetation. This savanna 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 there are several types of acacias with a dense crown in the form of umbrellas, as well as tree-like spurge. The baobab tree also grows here (Fig. 27), which is also called the monkey tree, or bread 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 drought it sheds its 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 during the rainy season. The fruits of the tree ripen at the beginning of the dry season; monkeys readily feast on them.

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

Rice. 27. Baobab

How are savanna plants adapted to the long dry season?

If the dry season lasts more than 8-9 months, then some of the trees die. their place is taken by shrubs. Such a savanna becomes like a desert. In northern Africa, on the border with the Sahara, it is called Sahel (Arab, region), 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 savannahs in search of food and water. Animals make especially large transitions during the dry period.

The African elephant (Fig. 28) is the largest living land animal. The length of its body reaches 7 m, and the weight of adult males is 5-7 tons. Since grassy food is low in calories, the elephant needs 100-300 kg of it per day. Every day the animal drinks 100-200 liters of water. In the past, these giants were mercilessly exterminated for ivory(that's what elephant tusks are called). 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 very tall trees. Despite the long neck, the giraffe is capable of jumping high. However, due to high blood pressure, one cannot run for a long time.

Buffalo, various antelopes, and zebras live in large herds. They are constantly in wait for predatory animals: 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: rhinoceroses, hippos and crocodiles.

The largest bird on the planet lives here - 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. The most common insects are ants and termites, which build tall structures of various shapes. Together with numerous soil microorganisms, they often complete the food chains in the savanna ecosystem.

Rice. 28. African elephant

Rice. 29. African ostrich

Think about what branches of crop and livestock breeding are common in the savannah zone.

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

Briefly about the main thing!

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

Savannah soils 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 savannas is diverse. Herbs predominate. Among the trees, the most famous are baobab, umbrella acacia, euphorbia, and aloe. All plants are adapted to a long dry season.

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

1. What features does the climate of the natural zone of savannas and woodlands have?

2. Name the main types of savannah soils. Why are they more fertile than the soils in the humid equatorial forest zone?

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

4. Name the most famous herbivores, carnivores and omnivores of the savannah.

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

6. Compare Various types African savannas: tall grass, typical and deserted.

Tropical zones are limited on the equator side by the summer position of the tropical front, and on the temperate latitude side by the winter position of the polar front. Tropical air is formed in it. which from subtropical pressure maxima goes to the equator in the form of trade winds. Tropical air is formed in anticyclones from descending equatorial air, as well as from polar air of temperate latitudes. Tropical air is here all year round is the main air mass.

The air of the trade winds is dry, especially in the trade winds that arise over the continents and have lower layers Very high temperature. But closer to the equator, the trade winds, which over the ocean approach the eastern shores of the continents, are moistened.

1.Location:

The zone of savannas and woodlands is developed in Africa, South America, Asia (Hindustan) and in northwestern Australia. In Africa it covers Sudan, East Africa, the watershed plateaus of the Congo - Zambezi and Zambezi - Limpopo, part of the Kalahari Basin; in South America - the Orinoco Basin and part of the Guiana Massif, as well as the vast territory of the Brazilian Massif and the Gran Chaco; in Australia - the northern quarter of the continent; In Asia - Hindustan south of 22 0 N. latitude.

2. Characteristics of temperature conditions, precipitation:

The temperature of the coldest month within the zone is from 12 to 20 0, the warmest is 20-35 0. atmospheric precipitation per year in different areas from 100 to 500 mm (in some places up to 1000 mm). The change between dry and wet seasons is very distinct. The river network is sparse: during the rainy season there are rapid short floods, during drought there is long shallow water, small watercourses dry up.

3.Soil:

Soils are black, red-brown, brown, gray-brown; in India, in red-brown soils at shallow depths, a compacted horizon of carbonate nodules (kankara) forms.

4.Vegetation:

At its core, savanna is a tropical type of herbaceous vegetation, differing from steppe vegetation by the presence of xerophilic, low-growing, sparsely standing trees, many of which are characterized by an umbrella crown. The main background of the savannah is created by hard-leaved grasses. Trees growing in the savanna have a long root system, reaching 50-60 m, many trees acquire an umbrella-shaped crown (acacia) to reduce evaporation. In West Africa large areas occupy wet savannas, where the height of cereals can reach 5 m. In dry savannas, the height of cereals is much smaller; powerful deciduous trees - baobabs - are often found (height up to 25 m, trunk diameter - 10 m or more, tree age can reach 1000 years). In the savannas of Australia, eucalyptus trees with an admixture of acacias grow; large spaces are occupied by dense thickets of xerophytic shrubs - scrub. In the Orinoco llanos, the main background consists of various cereals with rare groves of palm trees. In the Brazilian massif there are grass savannas, savannas with scattered crooked trees, shrubs, individual palm trees, as well as dry woodlands (caatinga) of cacti and trees with barrel-shaped trunks. In the Gran Chaco there are palm groves, drying up tropical swamps (pantanals), and dry-loving quebracho forests. In Hindustan there are shrub and herbaceous-shrub savannas, with acacias, thorny bushes, and succulents. Biomass in the savanna is 500-1500 c/ha.

5. Animal world:

The fauna of the savannah is exceptionally rich. The abundance of grasses also leads to an abundance of ungulates, many rodents, large and small predators, and reptiles. In the savannas of Africa, ungulates are common, most of them being antelope. There are rhinoceroses, giraffes, elephants, lions, jackals, and hyenas. They live in the savannahs of Australia different kinds kangaroos, a lot of rodents and insects.

The zones do not form continuous stripes everywhere. The boundaries of many zones deviate from parallels, and great contrasts in nature are observed within the same zones. Therefore, along with zonality, another geographical pattern is distinguished - azonality. Azonality– changes in components and complexes associated with the manifestation endogenous processes. The reason for azonality is the heterogeneity of the earth's surface, the presence of continents and oceans, mountains and plains on the continents, the uniqueness of local factors: the composition of rocks, relief, moisture conditions, etc. Endogenous relief is azonal, i.e. placement of volcanoes and tectonic mountains, structure of continents and oceans.

There are two main forms of manifestation of azonality - sectorality geographical zones and altitudinal zone. Within geographic zones, three sectors are distinguished: continental and two oceanic. The sectorality is most clearly expressed in the temperate and subtropical regions. geographical zones, weakest in the equatorial and subarctic.

Altitudinal zonation is a natural change in zones from the foot to the top of a mountain. Altitudinal zones are not copies, but analogues of latitudinal zones; their identification is based on a decrease in temperature with height, and not a change in the angle of incidence sun rays. In addition, the spectrum of solar radiation changes in the mountains: the proportion of ultraviolet rays increases. When climbing mountains, the pressure decreases, and there is no change in the length of day and night, as when moving from the equator to the poles. Most important differences between latitude zones and similar altitudinal zones are as follows:

1. Among the latitudinal zones there are zones not only of thermal, but also of dynamic origin (for example, areas of subtropical pressure maxima); there cannot be altitudinal belts of similar origin.

2. Temperature changes with altitude much faster than in the horizontal direction from the equator to the poles. In the Northern Region, the temperature decreases on average by 0.5 0 for each degree of latitude, in the vertical troposphere - by an average of 6 0 per kilometer. It is the rapid decrease in temperature with height that predetermines the possibility of altitudinal climatic zones, provided that the relief of the earth's surface is raised to a sufficient height (the change of zones in the mountains occurs faster).

3.Altitudinal zonation in the mountains is formed not simply under the influence of changes in altitude, but also under the influence of specific forms of the earth's relief. The difference in relief is one of the fundamental ones for the environment in which latitudinal zones and altitudinal zones are formed. Altitudinal zonation is therefore more diverse and changeable than zonality, and is much more susceptible to local factors (in the mountains there is a belt of subalpine and alpine meadows, which is not present on the plains).

4. The structure of the altitudinal zonation very strongly depends on the exposure of the mountain slope (on the southern and northern, on the leeward and windward slopes, a different spectrum of zones is formed: on the windward slopes a forest can grow, on the leeward, in drier conditions - steppe), under the influence of which a asymmetry of zonality, i.e. difference in heights of belts of the same name on opposite slopes.

5. Under certain conditions, it occurs altitudinal inversion(there is no inversion of latitudinal zones). The most common cause of inversions is the stagnation of cold air in intermountain basins, which rolls down here from mountain slopes and peaks (tundra is located at the bottom of the basin, coniferous forest is on the slopes).

At the same time, altitudinal zonality has much in common with horizontal zonality: the change of zones when ascending mountains occurs in the same sequence as on the plains when moving from the equator to the poles. Latitudinal zoning determines the type of altitudinal zonation: each zone has its own typical set of zones. The altitudinal zone always begins at the foot of the mountain range with an analogue of the latitudinal zone on which the mountain foot rests. In the mountains located in the steppe zone, the first altitudinal zone is mountain-steppe. The number of altitudinal zones generally depends on the height of the mountains and the latitude of the place. The simplest spectrum is observed in the mountains of polar latitudes - there is a single glacier belt there. In temperate latitudes there are already from three to five zones, in equatorial belt The most complete range of altitudinal zones is developing.

Along with altitudinal zonality, we can talk about the depth zonation of underwater landscapes. F.N. Milkov distinguishes shallow-water landscapes of the shelf, bathyal landscapes of the continental slope, abyssal landscapes of the ocean floor and ultra-abyssal landscapes of deep-sea trenches.

No consensus regarding whether the altitudinal zone is zonal or azonal. F.N. Milkov attributed altitudinal zonation to a manifestation of zonality. He wrote that there are geographical zones of plains, characterized by a relatively simple structure, and there are geographical areas of mountainous countries, characterized by a more complex structure, changing in horizontal and vertical directions. S.V. Kalesnik believed that altitudinal zonation is azonal. ON THE. Gvozdetsky believed that there were two forms of geographic zoning: horizontal - on the plains and high-altitude - in the mountains. A.G. Isachenko came to the conclusion that there are three zonal patterns: latitudinal zonality (latitudinal zonality), sectorality (meridional zonality) and altitudinal (vertical) zonality.

The article gives a definition of what savanna is. The climatic features of the natural zone are described, and characteristics of soils, flora and fauna are given.

This information will be useful for schoolchildren and students when preparing for a lesson, report or exam.

What are savannas

Savannas are vast areas that occupy a significant part of the subequatorial belt, covered with tall grassy vegetation and rare trees.

From the description of the natural zone of savannas and woodlands, the main points should be noted:

The grass cover is higher than in the steppes, and it is based on hard-leaved grasses.
Vegetation density can be high or low, so that the soil is visible.
There may be no trees at all, but there are areas that are almost sparse forest.

Geographical position

Location - subequatorial belt in both the northern and southern hemispheres. The map of natural zones shows that grassy areas cover almost 40% of the area of Africa, and certain territories are also located in Australia, North-East Asia, and America.

In South America, the natural zone covers the Brazilian Highlands and the plains of the Orinoco River. In Brazil, areas are occupied predominantly by open forest; in the Orinoco basin there is almost no woody vegetation. South American savannas have different names: Brazilian - campos, Venezuelan - llanos.

In Asia, the natural area occupies separate areas India, Burma, Ceylon, Indochina.

In Australia, grassy areas are located in the northeast and are characterized by a pronounced dry period.

Savanna plants

The flora is represented by a high grass cover with isolated trees and shrubs, and small groups of trees.

elephant grass

Most plants are hydrophytes, but there are also xerophytes adapted to the dry season. During the dry months, cereals burn out and many trees lose their leaves. Grasses stretch up to 3 m, and in the lowlands up to 5 m.

Characteristic plant species:

elephant grass;
oil palm;
doom palm;
pandanus;
baobab is a thick tree with an unusually shaped trunk.

In wetter places, the grass cover becomes lower (up to 1.5 m), supplemented by acacias - trees with a dense spreading crown, reminiscent of an umbrella.

Drier areas are characterized by thorny semi-savannas. The trees are without leaves almost all year round, the grass carpet is sparse and low (up to 1 m).

The flora is represented by low prickly tree species, succulents, and cushion shrubs. Some scientists call these areas the African steppe.

Soils

The main ones are red-brown and lateritic soils, characterized by sufficient humus content due to the abundant decomposition of grass.

Due to periodic moisture in the soil layers, saturation with metal oxides occurs actively, so crusts often appear on the surface of the earth.

Seasonality of moisture affects the processes of soil formation. In the wet season, soil layers are intensively leached; in the dry season, soil solutions rise due to heating of the earth's surface. Therefore, the accumulation of humus, blackening of soils, and the formation of chernozems are typical for dry savannas, where the period without precipitation is long.

Relief

On the African continent, the zone of savannas and woodlands occupies the plateau of East Africa, the watershed plateaus of the Zambezi, Congo, Limpopo rivers, and certain areas of the high Kalahari plains.

Savannah in Tanzania

In South America, savannas are found on the Brazilian and Guiana plateaus, the Gran Chaco plain, and in the Orinoco basin.

In Australia - on the northeastern plains.

Climate and climate zones

Savannas are located in the subequatorial climate zone. Two seasons are clearly identified: dry winter and wet summer. The annual temperature ranges from 18 to 32°C. Temperature fluctuations are slow and unexpressed.

The dry cool period lasts from November to April. The average temperature is 21°C. The weather is sunny, fires are frequent. No more than 4 inches (100 mm) of precipitation falls.

The dry season is the time of migration. Huge herds of ungulates go in search of food and water, and predators rush after them. Woody species survive in dry times thanks to their deep root system and dense, fire-resistant bark.

The hot, humid period begins in May and lasts until October. The amount of precipitation during the period reaches 10 - 30 inches (250 - 750 mm). Heavy rain falls in the afternoon.

During the rainy season, the life of the savannah is in full swing, the land is reborn after drought, covered with a lush green carpet.

Savannah inhabitants

The savannah fauna is unique. Nowhere else on the planet is there such a diversity of large ungulates and predators.

Unfortunately, since the beginning of the 20th century, wildlife has been seriously suffering due to the activities of poachers and indefatigable hunters, the construction of roads, and the allocation of large areas for cattle breeding and agriculture.

Horse antelope

The list of animals that have disappeared due to hunting includes:

white-tailed wildebeest;
horse antelope;
zebra quagga.

Ungulates

The largest group of savanna ungulates lives in Africa.

The most common:

blue wildebeest;
zebras;
Thompson's gazelles;
Grant's gazelles;
impalas;
Cannes;
cow antelope;
swamp;
giraffes;
buffalos;
warthogs;
African elephants.

Antelope Kudu

Rare ungulates found only in nature reserves are kudu and oryx.

Black and white rhinoceroses are on the verge of extinction. Their luxurious horn, as seen in the photo, is a valuable catch for poachers.

Great efforts are made in the reserves to preserve these animals.

Predators

Carnivorous animals are as diverse as herbivores.

African leopards

Common on the African plains:

lions;
spotted hyenas;
wild dogs;
leopards;
cheetahs;
caracals;
Nile crocodiles.

The American steppes are inhabited by:

jaguars;
ocelots;
maned wolves;
cougars.

Dingo dog

In Australia:

monitor lizards;
Dingo dogs.

Birds

The diversity of African birds is amazing and attracts tourists from all over the world.

African ostrich

In the trees, birds coexist with baboons and numerous species of monkeys. Flamingos decorate the ponds.

Rhea ostriches are inhabitants of the Brazilian steppes, emus ostriches are inhabitants of Australian ones.

Insects

Among the insects that eat green parts of plants are:

locusts (the most common family);
bronze;
cicadas;
Khrushchev;
caterpillars;
leaf beetles;
goldenrod;
stick insects.

The most common recyclers of dead organic matter are:

termites (savannas have the largest number of termite mounds, often of enormous size);
crickets;
worms;
cockroaches;
centipedes;
darkling beetles;
terrestrial molluscs.

Termites are the main food source for Australian and South American anteaters.

Every year more and more deserts encroach on savannas. This is especially noticeable in Africa. The main reason Why savannas give way to deserts is human activity. People take too much water from reservoirs for their needs, which is why vegetation experiences severe moisture deficiency.

Other causes of desertification are global warming and intensive cattle breeding. Grazing large cattle eats the grass so actively that the grass cover does not have time to recover.