Natural zone of semi-deserts: characteristics, geographical location, climate and semi-desert soils, photos, pictures. Deserts: characteristics and types Deserts geographical location climate plants animals

The report “Deserts” for children on the subject of the world around us will help you prepare for the lesson.

Message on the topic “Desert”

Desert is a natural zone characterized by a flat surface, sparseness or absence of flora and specific fauna.
Most often, in deserts, the annual precipitation is less than 200 mm, in extraordinary areas - less than 50 mm, and in some deserts there is no precipitation for decades.

Deserts can be found on all continents, with the exception of Europe. They extend across the temperate zone of the Northern Hemisphere and the subtropics and tropics of both hemispheres.

The largest deserts- these are the Sahara, Victoria, Karakum, Atacama, Nazca, and the Gobi Desert.

Deserts usually come in five types:

• sandy(vegetation is very rare, mostly thorny bushes, with roots going deep into the ground, this is necessary for water supply)
• clay,
• saline,
• rocky,
• snowy deserts(located beyond the polar circles and inhabited by animals resistant to cold).

The type of climate found in deserts is usually hot and arid. In this natural zone, daytime temperatures can rise to +50°C, while at night they can drop to 0°C. In the northern regions, the thermometer can drop to minus 40 °C. For these reasons, the climate of deserts is considered continental.

Life in deserts is concentrated mainly near oases - places with dense vegetation and bodies of water, as well as in river valleys.

Desert flora

The peculiarity of desert plants is that they must evaporate moisture as little as possible and obtain water at great depths or have their own supply of water. The plants have small, hard leaves or spines instead of leaves. The roots penetrate deep into the ground. Plants in the desert do not form a continuous cover. They are solitary, often growing in small groups among sand or cracked clay.

Tree trunks are most often severely curved. The most common desert plant is saxaul bushes. They grow in groups, forming small groves. Instead of foliage, their branches are covered with small scales.
How does this shrub survive in such arid soils? Nature has provided them with powerful roots that go into the ground to a depth of 15 meters.

And another desert plant - camel-thorn its roots can reach moisture from a depth of up to 30 meters. The spines or very small leaves of desert plants allow them to use moisture very economically through evaporation.
Among the various cacti, growing in the desert, there is Echinocactus Gruzoni. The juice of this one and a half meter plant perfectly quenches thirst.

In the South African desert there is a very amazing flower - fenestraria. Only a few of its leaves are visible on the surface of the earth, but its roots are like a tiny laboratory. This is where the nutrients are produced, thanks to which this plant even blooms underground.
One can only be amazed at the adaptability of plants to extreme desert conditions.

In the heat of the day, the desert seems uninhabited. Only occasionally do you see a lizard or some kind of bug. But as night falls, the desert comes to life. Animals crawl out of their hiding places to replenish their food supplies.

How do animals escape the heat? Some bury themselves in the sand. Already at a depth of 30 cm, the temperature is 40°C lower than on the ground. Kangaroo jumper, may not come out of its underground shelter for several days. Its burrows contain reserves of grains that absorb moisture from the air. They quench his hunger and thirst.

Jackals and coyotes Frequent breathing and sticking out your tongue save you from the heat.

African foxes, hares, hedgehogs Excess heat is emitted by large ears.

Long legs of ostriches and camels help to escape from the hot sand.
And the camel is more adapted to life in the desert than others. Thanks to its wide, calloused feet, it can walk on hot sand. Its thick and dense coat prevents moisture evaporation. The fat accumulated in the humps is converted into water if necessary. Although he can easily live without water for more than two weeks.
Desert insects “thought of” reflecting the scorching rays of the sun with the surface of their bodies.
Some animals ( turtles, jerboas, toads, frogs) can spend the entire hot summer in hibernation.
In the summer, to avoid getting burned, desert snakes crawl sideways on the sand, and lizards run so fast that their paws do not have time to warm up.
To find food in the desert, animals must move quickly, have good hearing and vision, and be able to camouflage themselves.
Desert snakes lie in wait for their prey, completely buried in the sand, only their head with closely spaced ears and eyes peeks out.

You can write a report on deserts using this information.

Questions to consider:

1. Characteristics of the desert

2. Desert Vegetation

3. Desert fauna

4. Desertification

5. Semi-desert

6. Protection of deserts and semi-deserts

7. Occupations of the population of deserts and semi-deserts

1. Characteristics of the desert.

Desert - a geographical zone with a hot, arid climate and sparse sparse vegetation in the temperate subtropical and tropical zones of the Earth.

The area of ​​deserts is estimated at 31.4 million km 2 (about 22% of land).

Deserts are found on every continent except Europe and are located within the borders of approximately 60 countries. In the mountains, the desert forms an altitudinal zone (high-mountain desert), and on the plains it forms a natural zone.Distributed in the temperate zone of the Northern Hemisphere, subtropical and tropical zones of the Northern and Southern Hemispheres.

Large deserts of the world:

Gobi – Central Asia, Mongolia and northern China

Taklamakan borders the Pamirs and Tibet from the north. Central Asia

Sahara - North Africa

Libyan Desert – north of the Sahara

Namib - Southwestern coast of Africa

Kyzylkum - between the Syrdarya and Amudarya rivers, Uzbekistan, Kazakhstan

Karakum - Turkmenistan

Atacama – Northern Chile, South America

Northern Mexico

Great Victoria Desert

Great Sandy Desert

Climatic conditions:

One of the main features of the desert is the lack of moisture, which is explained by the insignificant (50- 200 mm per year) by the amount of precipitation that evaporates faster than it seeps into the soil. Sometimes there is no rain for several years. Most of the territory is drainless, and only in places there are transit rivers or lakes that periodically dry up and change their shape (Lop Nor, Chad, Air). Some deserts formed within ancient river, delta and lake plains, others on platform land areas. Deserts are often surrounded by or bordered by mountains.

Over the course of a long geological history, deserts have changed their boundaries. For example, the Sahara - the greatest desert in the world - stretched for 400- 500 km south of the current position.

Precipitation 50-200 mm per year

There are 200-300 clear days a year

Air temperature +45° in the shade. Surface temperature during the day + 50-60° (up to 80° and even 94° - Death Valley), at night + 2-5° (sudden changes)

Dry winds, storms. Winter in Russia frosts with thin snow cover.

Contrary to the popular belief that the desert is an endless, monotonous sea of ​​sand, the most common are rocky deserts, or hamads, often located on plateaus or mountain ranges with outcrops of bizarre shapes. Among them, pebble and gravelly deserts stand out, impressive with their almost complete lifelessness. Areas of such deserts can be seen in the Sahara, Kyzylkum, and on the Arabian Peninsula. Under conditions of a huge daily temperature range, with periodic wetting and drying of rocks, a characteristic shiny dark crust is formed on their surface, the so-called desert tan, which protects the rock from rapid weathering and destruction. Often rocky deserts turn into sandy ones. In Central Asia they are called kumas, in Africa - ergs, in Arabia - nefuds. Sands are easily transported by the wind, forming aeolian landforms: dunes, dunes, safes, etc. Single dunes and dunes not secured by vegetation can move tens of meters per year. Sometimes sand blown by the wind makes a special sound. In such cases, they talk about singing dunes or dunes (in Dagestan, the singing dune is declared a natural monument). But the bulk of the sand is motionless, as it is held in place by the long roots of shrubs and grasses that have adapted to conditions of constant moisture deficiency. The largest sandy deserts in the world include: the Libyan Desert, Rub al-Khali, Nefud, Great Sandy Desert, Great Victoria Desert, Karakum Desert, Kyzylkum.

Clay deserts develop on clayey deposits of various origins. Largest clay deserts: Ustyurt, Dashte-Lut, Deshte-Kevir Betpak-Dala and others. Their relief is characterized by takyrs and sors.

Saline deserts are formed on saline (saline) soils and are scattered in separate spots among other types of deserts.

TAKYR - flat clayey surfaces, almost devoid of vegetation, in the deserts of the subtropical zone, an area of ​​several m2 up to tens of km 2 . In spring they are usually filled with water.

SALT CHARKS - soil types of steppe, semi-desert and desert zones. Contains water-soluble salts, 0.5-10% humus. In the Russian Federation - in the Caspian lowland.

SORA (blinders), closed depressions in deserts Wed. Asia, covered with a crust of salts or a puffy layer of salt dust. They are formed in sands due to evaporation and salinization of near-surface groundwater or on strata of salt-bearing bedrock under conditions of an exudate water regime with the formation of salt marshes.

SAHEL (Arabic - coast, outskirts) - the name of the transition strip (width up to 400 km ) from the Sahara deserts to the savannas of West Africa. Semi-deserts and deserted savannas predominate. Precipitation 200- 600 mm in year; frequent droughts.

Desert types

Based on their position, a distinction is made between continental deserts (Gobi, Taklamakan), located inside the continent, and coastal deserts (Atacama, Namib), stretching along the western coasts of the continents.

Deserts are sandy (Sahara, Karakum, Kyzylkum, Great Victoria Desert), clayey (Southern Kazakhstan, southern Central Asia), rocky (England, Israel) and saline (Caspian lowland).

2. Desert vegetation.

Desert vegetation does not form a closed cover and usually occupies less than 50% of the surface, characterized by a great variety of life forms and great sparseness.

Plant types:

1. Succulents - agave, aloe, cacti

2. The root system reaches groundwater

(roots 20-30 m ) - camel-thorn

3. Heat-resistant, able to tolerate dehydration - wormwood

4. Ephemeroids - develop for a short period of time, then rhizomes or bulbs remain in the soil. – tulip, sedge, bluegrass

XEROPHYTES (from the Greek xeros - dry and phyton - plant), plants adapted to life in arid habitats. Several types: succulents - heat-resistant, but do not tolerate dehydration (agave, aloe, cacti); hemyxerophytes - do not tolerate prolonged dehydration, the root system reaches groundwater (sage, camel thorn); euxerophytes - heat-resistant, able to tolerate dehydration (wormwood, gray speedwell, some mullein); poikiloxerophytes - when dehydrated, they go into suspended animation (some mosses).

EPHEMERA, annual herbaceous plants, the entire development of which usually occurs in a very short time (several weeks), usually in early spring. Characteristic of steppes, semi-deserts and deserts (for example, dimorphic quinoa).

EPHEMEROIDS, perennial herbaceous plants, the above-ground organs of which develop from autumn to spring and die in the summer, while the underground organs (bulbs, tubers) persist for several years. Characteristic of steppes, semi-deserts and deserts (species of tulip, sedge, bluegrass)

Plant adaptations:

root system deep into the soil;

modified leaves or spines, scales;

pubescent leaves - contributes to less evaporation;

dropping leaves with the onset of heat;

flowering only in spring.

Sandy deserts of Asia (Karakum, Kyzylkum, mouth of the Volga River)

Herbs, trees, leafless shrubs and semi-shrubs:

white saxaul (5 m),

sand acacia,

Chingil silvery - bush,

juzgun,

ephedra,

camel thorn (a genus of subshrubs and perennial herbs of the legume family, eaten by camels, root length 20- 30 m.),

grate - cereal,

swollen sedge,

seline (aristida) - cereal

Clay deserts of Asia (South Kazakhstan, lower reaches of the Ural River, south of Central Asia)

wormwood,

solyanka,

black saxaul (12 m ), Wood is used for fuel; green twigs are food for camels and sheep. Good sand fixer

bulbous bluegrass,

desert alyssum,

milkweed.

Asia. Saline deserts (Caspian lowland)

saltwort

knobby sarsazan

Africa

Celine (aristide)

Date palm trees in oases

America

Succulents (agave, aloe, cacti - cereus, prickly pear), yucca

3. Desert fauna

Accessories:

protective sand coloring,

fast run,

go without water for a long time,

hibernate

nocturnal lifestyle,

holes in the sand

bird nests on the ground (on bushes and trees).

Insects and arachnids: scarab, slowworm, scorpion, desert locust

Reptiles:fast foot-and-mouth disease, steppe agama, monitor lizard, round-headed lizard, frilled lizard, land iguana, sand boa, arrow snake, viper, efa, steppe viper, Central Asian tortoise, panther tortoise (Africa).

Birds:Sadzha (grouse), saxaul jay, desert warbler, field pipist, desert whiter, avdotka.

Rodents:jerboas, thin-toed ground squirrel, gerbils, giant mole rat.

Eared hedgehog.

Ungulates:goitered gazelle, antelopes, including gazelles, saiga, kulan.

Predatory:wolf, fennec fox, striped hyena, house (reed cat), sand cat, jackal, coyote, manul, caracal, South Russian bandaged, honey badger, Cape South African fox.

4. Desertification

The advance of deserts onto other areas of the earth is called desertification.

Causes:

Overgrazing.

Intensive long-term cultivation of the land.

Drought.

The Sahara, moving south, annually takes away 100 thousand hectares of arable land and pastures.

Atacama moves at speed 2.5 km per year.

Thar - 1 km per year.

5. Semi-deserts

Semi-deserts - areas that combine the nature of steppes and deserts, found in temperate, subtropical and tropical zones of the Earth (except Antarctica) and forming a natural zone located between the steppe zone in the north and the desert zone in the south.

In temperate Asia:

from the Caspian lowland to the eastern border of China.

In the subtropics:

Anatolian plateau, Armenian Highlands, Iranian plateau, Karoo , Flinders, Andean foothills, Rocky Mountain valleys, etc.

In the tropics of Africa:

south of the Sahara, in the Sahel zone (desert savannah)

Plants:

Russia:tulips, sedge, bluegrass, wormwood, mullein, solyanka.

America: cacti.

Africa and Australia: thickets of bushesand rare low-growing trees (acacia, doum palm, baobab)

Animals:

hares

rodents (gophers, jerboas, gerbils, voles, hamsters), meerkats,

reptiles;

antelope,

bezoar goat,

mouflon,

kulan, Przewalski's horse

predators: jackal, striped hyena, caracal, serval, steppe cat, fennec fox, house

birds,

many insects and arachnids (karakurt, scorpions).

6. Protection of deserts and semi-deserts

Reserves and national parks

Desert:

Semi-desert:

Ustyurt Reserve,

Tiger beam,

Aral-Paigambar.

Listed in the Red Book: Bandage, mole rat, gazelle, saiga, saja, caracal, serval

7. Occupations of the population of desert and semi-desert

Desert:breeding of sheep, goats and camels, irrigated agriculture and gardening only in oases (cotton, wheat, barley, sugar cane, olive tree, date palm).

Semi-desert:Pasture livestock farming and oasis farming are developed on irrigated lands.

Camels live in deserts (dromedary camels in Africa, Bactrian camels in Asia).

The desert was and remains an extreme natural environment for human life, although it was in desert conditions that ancient civilizations arose and existed: Egypt, Mesopotamia, Khorezm, Assyria, etc. Life usually arose near a well, river or other water source. This is how oases appeared, the first “islands” of life created by human labor. Life in the oases and the occupations of the population differed significantly from the conditions of the desert itself, where people are doomed to eternal nomadism under the scorching sun and dust storms in search of water. Breeding sheep and camels has become a traditional occupation of nomads. Irrigated agriculture and horticulture developed only in oases, where plants such as cotton, wheat, barley, sugar cane, olive trees, date palms, etc. had long been cultivated. The rapid influx of population into large oases led to the formation of the first cities.

FAMOUS DESERTS OF THE WORLD

GOBI (from Mongolian - waterless place), a strip of deserts and semi-deserts in Central Asia, in the south and southeast of Mongolia and in adjacent areas of China. Bounded in the north by mountainsMongolian Altai and Khangai, in the south - Nanshan and Altyntag. Divided intoTrans-Altai Gobi , Mongolian Gobi , Alashan Gobi , Gashunskaya Gobiand Dzungarian Gobi. Area over 1000 thousand km2 .

Plains predominate at an altitude of 900- 1200 m , composed mainly of rockschalk, Paleogene And Neogene. They alternate with more ancient small hills, ridges and island ridges (up to 1800 m ). Sloping piedmont plains are dissected by numerous dry channels flowing into closed depressions, which are occupied by drying lakes, salt marshes or hard clay surfaces; There are also small massifs of shifting sands.

The climate is sharply continental and temperate (temperature fluctuations from –40 °C in January to + 45°C in July). Precipitation per year ranges from 68 mm in the northwest of the Alashan Gobi to 200 mm in northeast Mongolia; there is a summer maximum. There are almost no rivers with constant flow; most riverbeds are watered only in summer. The soils are gray-brown and brown, often in combination with sandy deserts, salt marshes and takyrs. Carbonate, gypsum-bearing and coarse gravelly soil varieties are typical.

Desert vegetation is sparse and sparse. On the plateau and piedmont plains there is small-shrub gypsophilic vegetation (barnyard grass, parfolia, teresken, reomuria, several species of saltpeter and saltwort). On the salt marshes, in addition to saltpeter and saltwort, there are tamarisks and potash grass. On the sands there are sand wormwood, Zaisan saxaul, kopeck grass, perennial and annual grasses. Semi-deserts are widespread in the northeast and east of Mongolia, where, along with wormwood and solyanka, cereal groups are developed, and rare clumps of dwarf shrub caragana are found. A wild camel, a wild ass, a Przewalski's horse, several species of antelope, and many rodents and reptiles have been preserved. Many endemic species of flora and fauna. Great Gobi Nature Reserve (within Mongolia).

Livestock (small ruminants, camels, horses, and, to a lesser extent, cattle). Fairly abundant groundwater is of great importance for water supply. Agriculture is developed only in river valleys.

KYZYLKUM, desert in Wed. Asia, in the area between the Amu Darya and Syr Darya rivers, in Uzbekistan, Kazakhstan and partly in Turkmenistan. OK. 300 thousand km2 . Plain (height up to 300 m ) with a number of closed depressions and isolated mountain ranges (Sultanuizdag, Bukantau, etc.). Most of it is occupied by ridge sands; in the north-west there are many takyrs; there are oases. Used as pasture.

SAHARA desert in Africa, the largest in the world. St. 7 million km2 . The countries of Morocco, Tunisia, Algeria, Libya, Egypt, Mauritania, Mali, Niger, Chad, Sudan are located entirely or partially on the territory of the Sahara. OK. 80% of the Sahara are plains with a height of 200- 500 m . In the northeast there are drainage depressions: Qattara (133 m), El-Fayoum, etc. In the central part there are mountain ranges: Ahaggar, Tibesti (Mount Emi-Kusi, 3415 m , the highest point of the Sahara). Rocky and gravelly (hamads), pebble (regs) and sandy (including ergs) deserts predominate. The climate is tropical desert: there is less rainfall in most of the territory 50 mm per year (on the outskirts 100 - 200 mm ). Average temperatures in January are not lower than 10 °C; absolute maximum 57.8 °C, absolute minimum -18 °C (Tibesti). Daily air temperature amplitudes are more than 30 °C, soil temperatures are up to 70 °C. In addition to the transit river. Nile and parts of the Niger, there are no permanent watercourses. Dry beds of ancient and modern watercourses (wadis, or oueds) predominate. Groundwater feeds numerous oases. The vegetation cover is extremely sparse and sometimes absent. Farming (date palm, grains, vegetables) in oases. Nomadic and semi-nomadic livestock raising.

TAKLA MAKAN desert in western China, one of the largest sand deserts in the world. Length from west to east over 1000 km, width up to 400 km , sand area over 300 thousand km2 .

It was formed under conditions of long-term accumulation of sediments within the Tarim Basin, which is composed mainly of alluvial deposits (the Tarim River and its tributaries), partially blown over. The surface is flat, gradually decreasing to the north and east from 1200- 1300 m to 800-900 m . In the west, single ridges rise above Taklamakan (the highest point is Mount Chongtag, 1664 m ), composed of sandstones.

Most of the territory is covered with sands up to 300 m . In the southwest dunes predominate, in the northeast there are sand ridges of complex configuration (including large ones, sometimes stretching for 10- 13 km , - the so-called whale backs), sand pyramids (height 150- 300 m ) etc. Along the outskirts of Taklamakan, significant areas are occupied by salt marshes.

The climate is moderately warm, sharply continental, with negligible (less 50 mm per year) amount of precipitation. The atmosphere is characterized by high dust content. The rivers flowing from Kunlun penetrate into the depths of Taklamakan by 100- 200 km , gradually drying up in the sands. Only the Khotan River crosses the desert and in summer brings its waters to the Tarim River, which flows along the western and northern outskirts of Taklamakan.

Depth of groundwater in relief depressions (within ancient deltas and old rivers) 3- 5 m , they are usually difficult for plants to access, so most of the territory is devoid of vegetation cover and only in places with close groundwater there are sparse thickets of tamarisk, saltpeter, and reeds. Along the outskirts of Taklamakan and river valleys one can find turanga poplar, oleaster, camel thorn, annual saltwort, and saxaul. The fauna is poor (rare herds of antelopes, hares, gerbils, jerboas, voles); in river valleys there are wild boars.

Individual oases (mainly in the valleys of the Tarim and Yarkand rivers). There is no permanent population. Near the southern outskirts of Taklimakan, among the sands, there are the ruins of ancient settlements, confined to dry valleys.

ATACAMA (Atacama), desert in northern Chile, in the South. America, along the Pacific coast, between 22-27° S. sh.; less precipitation 50 mm in year. The river is crossed. Loa. Large deposits of copper ores (Chukicamata, El Salvador), saltpeter (Taltal), table salt, and borax.

ADDITIONAL MATERIAL

Przewalski's horse (Equus caballus), an equine mammal. Body length 2.3 m , height at withers approx. 1.3 m . This is a completely typical horse, densely built, with a heavy head, thick neck, strong legs and small ears. Its tail is shorter than that of a domestic horse, and its mane is erect and short. The color is sandy-red or reddish-yellow. The mane and tail are black-brown, a black-brown belt runs down the middle of the back, and the end of the muzzle is white. In summer the hair is short and tight, in winter it is longer and thicker.

This wild horse was discovered and described in Central Asia by N. M. Przhevalsky in 1878. It was once widespread, but by the end of the 19th century it survived only in the southwest of Mongolia (in Dzungaria), where it was last seen (in natural conditions) in 1967-1969. Przewalski's horse herds consisted of 5-11 mares and foals led by a stallion. They were very mobile and constantly moved, which was determined by both poor winter pastures and uneven rainfall in their habitats. Constant migrations have led to the fact that these horses have become very hardy and strong. They always emerged victorious from fights with domestic stallions.

The main reason for the destruction of the population in natural conditions is fishing (hunting, poaching) and competition for watering places with livestock. Almost immediately after the discovery of the animals, the owner of the Askania-Nova park F. Falz-Fein and later the animal dealer K. Gagenbeck began to look for opportunities to get these rare animals. In this struggle, various means were used. Hagenbeck, having learned about Falz-Fein's suppliers in Biysk, with the help of his agents, bought 28 foals. Despite the fact that by the beginning of the 20th century, 52 purebred Przewalski horses were brought to Europe, only three pairs served as a source for breeding. The Przewalski's horse is kept in many zoos around the world; several dozen individuals live in semi-free conditions in the Askania-Nova Nature Reserve. An international plan has been developed for the reintroduction of Przewalski's horse into its original habitat - the mountain-steppe zone of Mongolia.

Jerboas (jerboas, Dipodidae) are a family of mammals of the rodent order; includes 11 genera and about 30 species, including the three-toed dwarf jerboa, the great jerboa, the long-eared jerboa, and the hairy jerboa. Jerboas are characterized by a large head with a blunt muzzle, long rounded ears, large round eyes and long vibrissae, a short short body (body length 4- 26 cm ), small front legs, powerful jumping hind legs. Large ears, eyes and long vibrissae indicate a highly developed hearing, twilight vision and touch, which are necessary for jerboas when searching for food and protecting themselves from enemies at night. The small front legs are used for grasping and holding food, as well as for digging holes, in which jerboas achieve great skill. The hind limbs are jumping limbs, and in connection with this function they are greatly modified: the foot is elongated and the three middle metatarsal bones are fused into one common bone called the tarsus. The tail plays an important role when moving: it serves to maintain body balance when jumping, especially during sharp turns at a fast pace. The black and white tassel at the end of the tail in many species is called a banner and serves as a signaling device for intraspecific communication. In addition to gnawing food, the incisors serve to loosen the soil when digging holes, while the limbs are used mainly for raking out loosened soil.

Jerboas are distributed from Northern and Northeastern Africa, Southeast Europe, Asia Minor and Western Asia through Transcaucasia, Central Asia, Kazakhstan, the extreme south of Siberia (Altai, Tuva, Transbaikalia) to Northeast China and Mongolia. They are mainly found in semi-desert and desert landscapes, only a few species inhabit the steppe zone, and some penetrate into the mountains to higher altitudes 2 km above sea level. Different species have developed adaptations to living on loose or dense soils, and therefore jerboas can be found in sandy, clayey, and gravelly semi-deserts and deserts.

Jerboas are typically nocturnal animals. Before dawn, they hide in holes that they build themselves. The main passage of the jerboa's burrow runs obliquely below the surface with one or more blind backup passages approaching almost to the surface. The main passage is clogged for the day with an earthen plug called a kopeck. From this penny, which has not yet dried out in the early morning, you can find a jerboa's hole. If you start digging out an inhabited hole, the animal knocks out the ceiling of one of the emergency passages and jumps out through it. In the far part of the main passage, the jerboa digs up a hole with a rounded living chamber, which is lined with finely chewed blades of grass. Jerboas spend the winter period in deep hibernation in their burrows.

The food for jerboas is the seeds of various plants and lily bulbs, which they dig from the ground. The diet also includes green parts and roots of plants, and in some species a significant proportion of the diet consists of animal food (small insects and their larvae). In spring and summer, the animals reproduce; the female gives birth to 1-8 cubs (usually 2-5).

Jerboas play an important role in desert biocenoses. They have a significant impact on soil and vegetation cover and serve as food for desert predators. In many areas, jerboas are background animals. Some species damage plants that strengthen sand; they can be carriers of pathogens of a number of infectious diseases of animals and humans.

GERBILS (Gerbillinae), a subfamily of mammals of the rodent order; includes about 100 species, grouped into 13 genera, including dwarf, small, large, short-eared, fat-tailed gerbils, taters (barefoot gerbils). Externally, gerbils resemble rats or mice. Their body length is up to 19 cm , reddish-yellow long tail with a tassel. The back is yellow-sandy, the belly is white.

Gerbils are common in the desert steppes and deserts of Africa, Asia and Southeast Europe. They feed mainly on plant foods, but can also eat small invertebrates. They do not hibernate during the winter, but in cold weather they do not leave their burrows for a long time, feeding on prepared reserves. Many breed year-round, with females having multiple litters of 2 to 12 young. Gerbils are carriers of the pathogens of plague and tick-borne typhus; they damage agricultural lands. These animals are often kept at home.

GEYRAN (Gazella subgutturosa), an artiodactyl mammal of the genus of true gazelles (Gazella) of the gazelle subfamily (Antilopinae); forms 2-4 weakly expressed subspecies. Body length 95- 125 cm , height at withers 60- 75 cm, weight 18-33 kg . Males have black and lyre-shaped horns up to 40 cm . Females are usually hornless. The color of the upper body and sides is sandy. The underparts, neck and inside of the legs are white. The tail is two-colored: the main part is sandy, the end is black. When a frightened gazelle runs, it raises it to the top, and its tail stands out sharply against the background of a white mirror. For this feature, the Kazakhs and Mongols called the gazelle the black tail (kara-kuyryuk, khara-sulte). Young goitered gazelles have a pronounced facial pattern in the form of a dark brown spot on the bridge of the nose and two dark stripes extending forward from the eyes.

Goitered gazelle is common in Western, Middle and Central Asia, Southern Kazakhstan, as well as in Eastern Transcaucasia. It lives in flat, hilly deserts and cereal-salt semi-deserts. As good runners, goitered gazelles prefer areas with dense soil, avoiding loose sand. In summer, they graze in the morning and evening, and spend the hottest time lying down, saving moisture. The beds are located on level ground near trees, often favorite ones, and bushes. Dzheyran moves after the shadow of the tree, hiding, first of all, his head from the sun. Raised from its rest, the gazelle quickly jumps up and rushes at a speed of 55- 60 km/h about 200-300 m , then looks around. In winter it grazes almost all day.

Goitered gazelles feed on herbaceous or shrubby plants, in summer choosing the grasses most saturated with moisture: barnyard grass, onions, ferules. Goitered gazelles usually go to watering places with open and level banks without dense coastal thickets in 10- 15 km once every 3-7 days. They are able to quench thirst not only with fresh, but also with brackish water (including from the Caspian Sea). The grass that goitered gazelles eat may also contain significant amounts of salt.

In spring and summer, animals live alone or in small groups of 2-5 animals. In autumn and winter they gather in herds of several dozen to hundreds of animals. Then the rut occurs. The beginning of the rut is preceded by the installation of rutting latrines by males. In September, males dig small holes with their front hooves and leave their excrement there. Other males, finding such holes, may throw out old excrement and leave their own there. Obviously, such pits serve as markers of occupied territory. Pregnancy in females lasts 5.5 months. In May, the female brings one, or less often two, cubs. For the first days, newborns only lie on a bare piece of ground. The sandy-brown color of the baby gazelle blends so well with the soil that you can easily step on the baby without noticing it. The cub begins to follow its mother and feed itself after two weeks. The main natural enemy of the goitered gazelle is the wolf.

In captivity, the gazelle is well tamed and reproduces, but does not live long. The gazelle population is declining, although work is underway to restore the number of animals. The subspecies from the Arabian Peninsula (Gazella subgutturosa marica) is listed in the International Red Book.

Fennec (Fennecus zerda) is a species of predatory animal of the wolf family. Outwardly it resembles a miniature fox. Body length approx 40 cm , tail to 30 cm ; weight 1.5 kg ; ears are large (height up to 15 cm ) and wide. The coat is long, reddish-cream, fawn or almost white on top; The tip of the fluffy tail is black. Fennec fox lives in the deserts of North Africa and South-West Asia. It is active at night and spends the day in a deep hole. Huge ears allow the Fenech to catch the slightest rustle. In case of danger, he buries himself in the sand. When hunting, the fennec can jump high and far. It feeds on small rodents, birds and their eggs, lizards, insects, carrion, and plants. The female's pregnancy lasts 51 days. Cubs (2–5) are born in March–April in a burrow with a nesting chamber lined with grass, feathers and wool.

JACKALS, a group of species of predatory mammals of the wolf family. The most common is the Asian jackal (Canis aureus), which in appearance is similar to a small wolf. Its body length is up to 85 cm , tail about 20 cm ; weight 7–13 kg. The color of the coat in winter is fawn, dirty yellow, with a noticeable red and black tint, the tail is reddish-brown with a black tip. It is found in southern Eurasia, North Africa; in Russia mainly in the North Caucasus. The Asian jackal prefers to settle in thickets of bushes and reeds, on plains, near rivers, lakes and seas. It is less common in the foothills. The jackal uses natural niches and depressions, crevices among stones, and sometimes abandoned holes as shelters. The animal is active mainly at night, but often during the day. Migrates only in search of food.

The jackal is omnivorous, but feeds mainly on small animals: rodents, birds, fish, as well as insects, carrion and the remains of the prey of large predators. It also eats fruits and berries, including grapes, watermelons, melons, and plant bulbs. Living near villages, he also hunts poultry. When going out to hunt, the jackal emits a loud howl, which is picked up by all its relatives nearby. They hunt more often alone or in pairs. The jackal forms pairs for life; the male takes an active part in creating a hole and raising offspring. The rut occurs from January to February. Pregnancy lasts about 2 months. Usually 4–6, rarely 8 puppies are born. The Asian jackal is a carrier of dangerous diseases (rabies and plague). It has no commercial significance.

The scooping jackal (Canis mesomelas) and the side-striped jackal (Canis adustus) live in Eastern and Southern Africa. In their lifestyle and habits they are similar to the Asian jackal. The Ethiopian jackal (Canis simensis) is found in Ethiopia. Outwardly, he looks like a dog with a fox head. A wide black stripe stretches along the middle of the back, sharply demarcated from the red sides and limbs. The belly is white, the tail is long red, with a black end. The Ethiopian jackal lives in the mountains at altitude 3000 m , it feeds on rodents and hares. Its numbers are small and this animal is protected.

COYOTE (grass wolf, Canis latrans), a predatory mammal of the wolf family. Body length approx 90 cm , tail - 30 cm . Erect ears, a long fluffy tail, which, in contrast to a wolf, he holds down when running. The coat is thick, long, grayish or reddish-brown in color on the back and sides, very light on the belly. The end of the tail is black. The coyote is distinguished by developed higher nervous activity; it is able to adapt to a changing environment.

The coyote lives in the prairies and steppes of North and Central America. Runs into the forests by accident. His lifestyle has a lot in common with the jackal. It makes its lair in caves, hollows of fallen trees, and deep burrows. The loud howl of a coyote is an integral part of the color of the prairies. It feeds on rodents, hares, rabbits, birds and lizards, sometimes fish and fruits, and does not disdain carrion. It rarely attacks domestic animals (goats, sheep). Hunts both alone and in a pack; destroys a lot of harmful rodents. It is completely safe for humans. Pairs form for life, the rut takes place in January-February. Pregnancy lasts 60-65 days. There are 5-10, sometimes up to 20 cubs in a litter.

CARCAL (Felis caracal), a predatory mammal of the cat family, genus of cats. Body length 65- 82 cm , tail 20- 31 cm ; weight 11- 13 kg . In appearance and ear tufts it resembles a lynx. But he has a thinner, more slender body, with tall, thin legs; It is also distinguished by a uniform light red color. There are small black markings on the face and ears, and the ends of the ears are decorated with tassels.

It lives in the deserts of Africa and Asia, including in the south of Turkmenistan. It hunts mainly at night, and during the day finds shelter in abandoned burrows. The caracal steals prey and overtakes it with large (up to 4.5 m ) jumping. Mainly feeds on rodents: gerbils, jerboas, ground squirrels, and tolai hares; less often birds, small antelopes, hedgehogs, porcupines. Can hunt livestock and poultry.

Cubs (1 to 4) are born in early April. In ancient times, caracals were trained to hunt antelope, hares and birds. It has no commercial significance. Few in number. The caracal is listed in the International Red Book. Protected in the Repetek Nature Reserve.

KULAN (onager, Equus hemionus), an equine mammal. Body length 2.0- 2.4 m , height at withers 110- 137 cm , weight 120- 127 kg . In appearance, the kulan is slender and light. The head is relatively heavy, the ears are longer than those of a horse. The tail is short, with a black-brown brush at the end, like that of donkeys and zebras. Colored sandy yellow in various shades. The belly and inner parts of the legs are white. From the withers to the croup and along the tail there is a narrow black-brown stripe. The mane is low.

Kulan is widespread in Western, Middle and Central Asia. However, the once large range has shrunk significantly. The number is restored only in nature reserves, including in the south of Turkmenistan (Badkhyz Nature Reserve). The kulan was introduced to the island of Barsakelmes and to the foothills of the Kopetdag. Habitats depend on territorial features. The animal can inhabit hilly plains or foothills, deserts and semi-deserts. With the exception of spring, when pastures are covered with young, lush grass, kulans need daily watering and do not move further than 10 days from water bodies. 15 km . When in danger, they can reach speeds of 60- 70 km/h without slowing down for several kilometers. There are no strictly defined periods of grazing and rest.

The kulan is peaceful towards most animals, except sheep, and often grazes with goitered gazelle and herds of horses. These animals have developed mutual communication; as soon as the goitered gazelle becomes wary, or shouts in alarm to the birds, the kulan takes off from its place. An angry kulan is very ferocious.

Kulans have well-developed vision, hearing and sense of smell. Approach the kulan undetected at a distance of 1- 1.5 km impossible. However, he can pass by a motionless person at a distance 1.5 m , and this is due to the characteristics of his visual apparatus. The kulans can hear the click of a camera from a distance 60 m . These are silent animals. With a cry reminiscent of a donkey, but more dull and hoarse, the male calls the herd.

The rut occurs from May to August. During the rutting period, the male begins to prance in front of the females, raising his head high. Often runs around the herd, jumps, screams, rolls on its back, tears with its teeth and throws up tufts of grass.

Even before the start of the rut, adult males drive young kulans out of the herds. During this period, serious fights between males occur. With their mouths bared and their ears flattened, they, with bloodshot eyes, rush at each other, trying to grab the hock joint. If one succeeds, then he begins to spin the opponent in a circle and gnaw his neck.

Pregnancy of females lasts 331-374 days, on average 345. Cubs are born from April to August. For the first hours they lie motionless, but already on the first day they begin to graze with their mother. The grown-up little kulan becomes very active. When he wants to eat, he walks around his mother, digs the ground with his foot near her belly, and throws his legs over her neck. The male protects the cubs from possible attacks by young kulans. Animals reproduce in captivity. Kulans are protected everywhere, two subspecies - the Syrian kulan (Equus hemionus hemippus) and the Indian kulan (Equus hemionus khur) are listed in the International Red Book.

CAMELS (Camelus), a genus of mammals of the camelid family of the order Callus; includes two species: dromedary (one-humped) and bactrian (two-humped). Length up to 3.6 m . Camels are characterized by the following characteristics: they do not have hooves - their legs end in two toes with blunt claws, and the lower surface of the foot is protected by an elastic calloused pad. They are common in the deserts of Central Asia (Bactrian), as well as in Africa, Arabia, Asia Minor, and India (Dromedar).

Camels feed on shrub and semi-shrub saltworts, tree leaves, and bulbs. The well-known ability of camels to go without water for a long time is due to the fact that they can tolerate a slight increase in body temperature without increased moisture loss. This feature allows you to spend less moisture on cooling. In addition, moderate dehydration in a camel is not accompanied by thickening of the blood and disruption of its circulation, as in mammals not adapted to desert conditions. Camels are able to drink quickly and a lot (they drink about 130–135 liters of water in 10 minutes).

The rut occurs in winter. Usually one, rarely two, cubs are born. Only Bactrian has survived in the wild. The dromedary is domesticated and used as a pack and draft animal, as well as for milk, meat and wool.

BACTRIAN - a domesticated Bactrian camel, differs little from the wild Bactrian camel. Many zoologists do not make a difference between the concepts of Bactrian camel and Bactrian. Domestic camels have larger humps, wider feet, and well-developed calluses on the knees of the front legs. The proportions of the skulls of domestic and wild animals have small but consistent differences. The color of the coat of domestic camels is variable - from light, sandy-yellow to dark brown, while wild ones have a constant reddish-brown-sandy color. The Bactrian camel was domesticated more than a thousand years BC. As an animal resistant to low temperatures and anhydrous conditions, it has become widespread in Mongolia, Northern China and Kazakhstan. There are several breeds of domestic Bactrian camels - Kalmyk, Kazakh, Mongolian.

DROMEDAR (dromedary, one-humped camel; Camelus dromedarius), a mammal of the camelid genus of the callosed order. Length approx 2.1 m , height at withers 1.8- 2.1 m . Unlike Bactrian, it has one hump, as well as shorter and lighter hair. The dromedary camel was domesticated in ancient times, probably in Arabia or North Africa. Not found in the wild. It is widespread in Africa, Arabia, Asia Minor and Central Asia, India, and was introduced to Mexico and Australia. Several breeds are known: high-speed riding Maharis (North Africa), riding Indian Rajputanas, pack Turkmen dromedaries.

Its lifestyle is similar to Bactrian. It tolerates heat better, but worse - frost. Can survive without water for up to 10 days. Passes under saddle in a day 80 km at speeds up to 23 km/h . However, in a caravan the dromedary passes no more than 30 km , since it must graze for a long time. Herbivorous. The rut occurs in winter. When crossed with Bactrian, it produces fertile offspring (the so-called bunks), which are superior in endurance to their parents. But the offspring when crossing hybrids turns out to be weak.

Deserts and semi-deserts of Eurasia extend from the Caspian lowland to China. In Russia, this occupies the territory of the southeastern regions of the country. The Arctic desert is located in the northern territories. A distinctive feature of deserts and semi-deserts is the high fluctuation of winter and summer temperatures. Semi-deserts are located in the northern part of the natural zone. The climate here is milder, so they are characterized by a steppe landscape. Closer to the south, where it becomes arid and the vegetation cover practically disappears, there is a desert zone.

Geographical location and natural conditions

Arctic desert, as well as deserts and semi-deserts on the map of Russia

In the area of ​​the left bank of the Volga, deserts and semi-deserts stretch to Kazakhstan. The lands from the right bank of the river extend to the foothills of the Caucasus. The territories lie on the Caspian lowland, which is a flat area. Millions of years ago there was a seabed here. Most of the deserts are a flat land surface, and only in the west are there steep slopes.

Climate

The natural zone is located in an area of ​​sharply continental climate. Rain and snow fall infrequently, making the climate dry but harsh. Most precipitation occurs in spring and summer. The level of evaporation exceeds the amount of precipitation.
The desert experiences strong daily and annual temperature ranges. During the day, the temperature difference can reach thirty degrees Celsius. In winter, the thermometer drops to -30°C and the winds rage. Their gusts blow away the snow cover from the soil, causing it to take on a black tint. Summer temperatures exceed +40°C. It rains rarely, but dust storms and dry winds often occur.

Vegetable world

The soils in semi-deserts are saline because they are based on ancient marine rocks. Wormwood-grass vegetation grows in semi-deserts. The lands contain little humus, and as a result of human economic activity they turn into shifting sands, and therefore are infertile. Nevertheless, the vegetation cover of the natural area is variegated. Feather grass, fescue, white wormwood, black wormwood, desert wheatgrass, and viviparous bluegrass grow here. From April to November, semi-desert lands are used as pastures. In June, with the onset of the dry period, the vegetation disappears, and the semi-desert becomes like a desert.

Closer to the south, the climate becomes arid, and the lands turn into a real desert. It is usually divided into two subzones: northern and southern. In the northern part the climate is mild. Subshrubs dominate here: saltmarsh barnacle, gray quinoa, and redberry. adapt to living conditions, many of them are leafless to reduce moisture evaporation. Vegetation in one form or another is located throughout the desert. In the southern part there are small trees and shrubs: sand acacia, Richter's solyanka, white saxaul. These areas also serve as pastures.

Animal world

In the semi-desert and desert zones there are many that have adapted to harsh conditions. Animals dig deep holes to wait out the heat of the day in them. Jerboas, gophers, mice and voles have developed optimal conditions for existence in the harsh conditions of the natural zone.

During the polar night, which lasts 90 days, winter begins. Summer comes with a polar day. There are no transitional seasons. Winter temperatures are low, down to -60°C. There is little precipitation. Winds blow snow cover off the soil. Summer doesn't last long. The air temperature in July is +3°C. During the polar day, the sun does not warm the air well. The snow does not melt for 300 days a year, and winter comes overnight.

Trees and bushes are completely absent. In summer the lands are covered with lichens and mosses. Sedge and cereals grow on rocky soil. In the Arctic desert in summer you can find green oases with polar poppy, saxifrage, buttercup and Arctic pike.

The soil thaws to a depth of 40 cm. Iron oxides accumulate in the upper part, causing the soil to acquire a brown tint. There is sand and stones on the surface. Spherical formations, spherulites, are a landmark of cold deserts.

The fauna is scarce. Animals living in the Arctic desert feed on seafood. Polar bears, leading a semi-aquatic lifestyle, breed off the coast of Chukotka, on Franz Josef Land. In the Wrangel Island Arctic Nature Reserve, dens have been created for them. Arctic foxes, lemmings, hares, and reindeer come from here in the summer. Seals and walruses set up their rookeries on the coast. Birds are considered the most numerous class. Bird markets are organized by eider ducks, gulls, tundra partridges, guillemots, and terns. When the polar day arrives, snow geese, geese, plovers and dunlins flock to the Arctic.

Ecological problems of deserts and semi-deserts of Russia

The main threat to turning deserts into wastelands is human intervention. Recent scientific research has shown that these areas contain deposits of oil and natural gas. Due to technological progress, the need for them is constantly growing. Oil production pollutes nearby areas more than others. The entry of “black gold” into the environment entails an environmental disaster.

The desert and semi-desert zones of Russia are home to many different species of animals, some of which are listed in the Red Book. Poaching puts the survival of valuable animals into question. The process of desertification itself causes damage to agriculture. The number of pastures is decreasing.

Due to anthropogenic influence, ice in the Arctic is melting, as a result of which the Arctic desert zone itself is shrinking. If it disappears, a large number of flora and fauna will disappear from the face of the Earth. Snowmobiles and other land vehicles pollute with exhaust emissions. Ozone holes negatively affect animal life. destroys mining, waste, . Large fish species are under threat of extinction. Their food, small fish and seafood, is caught on an industrial scale.

Deserts and semi-deserts need our protection. Already today there are nature reserves in the territories, but this is not enough. Work to protect natural areas must be controlled at the state level. Every effort should be made to resolve existing problems so that new ones do not arise.

And very poor wildlife. All this is due to the extremely harsh climatic conditions of the planet where they are located. Deserts, in principle, can form in almost any region. Their formation is primarily associated with low rainfall. This is why deserts are primarily found in the tropics. Tropical deserts occupy the territory of most of tropical Africa and the western coast of the tropical zone, as well as the territory of. Here their formation is associated with the year-round dominance of tropical waters, the influence of which is enhanced by the terrain and cold currents off the coast. Also, a large number of deserts are located in the subtropical and temperate zones of the Earth. This is a territory in South America, where their formation is due to the isolation of the southern tip of the continent from the penetration of moist air by cold currents, as well as in the interior and Central Asia. Here, the formation of deserts is already associated with a strong continental climate due to the great distance from the coast, as well as mountain systems that prevent the penetration of moisture from the ocean. The formation of deserts can also be associated with extremely low temperatures on the planet; we consider this type of deserts, also called Antarctic deserts, separately.

The natural conditions of deserts are extremely harsh. The amount of precipitation here does not exceed 250 mm per year, and in large areas it is less than 100 mm. The Atacama Desert is the driest in the world, where no rainfall has been recorded for 400 years. The largest desert in the world is the Sahara, located in the North (pictured. Author: Rosa Cabecinhas and Alcino Cunha). Its name is translated from Arabic as “desert”. The highest temperature on the planet, +58°C, was recorded here. Under the scorching rays of the sun in the summer months, when it reaches its zenith at noon, the sand under your feet heats up to enormous temperatures, and sometimes you can even fry eggs on the stones. However, as the sun sets, the temperature in the desert drops sharply, changes reaching tens of degrees during the day, and on a winter night frosts even occur here. This is due to the constantly clear sky due to the downward flows of dry air from the equator, because of this, almost no clouds form here. The vast open spaces of deserts do not at all prevent the movement of air along the surface of the earth, which leads to the emergence of strong winds. Dust sandstorms come unexpectedly, bringing clouds of sand and streams of hot air. In spring and summer, a strong wind rises - samum, which can literally be translated as “poisonous wind”. It can last only 10-15 minutes, but the hot dusty air is very dangerous for humans, it burns the skin, the sand does not allow you to breathe freely, many travelers and caravans died in the deserts under this deadly. Also, at the end of winter - beginning of spring, a seasonal wind begins to blow from the desert almost every year - khamsin, which in Arabic means “fifty”, since on average it blows for fifty days.

Deserts, unlike tropical deserts, are also characterized by strong temperature changes throughout the year. Hot summer gives way to cold, harsh winter. Air temperature fluctuations over the year can be about 100°C. Winter frosts in the deserts of the temperate zone of Eurasia drop to -50°C, the climate is sharply continental.

In especially severe deserts, the flora of deserts may be completely absent; where moisture remains sufficient, some plants grow, but the flora is still not diverse. Desert plants usually have very long roots—more than 10 meters—to extract moisture from groundwater. In the deserts of Central Asia, a small shrub grows - saxaul. In America, a significant part of the flora is made up of cacti, in Africa - milkweed. The fauna of deserts is also not rich. Reptiles predominate here - snakes, monitor lizards, scorpions also live here, and there are few mammals. One of the few that was able to adapt to these difficult conditions was the camel, which was not accidentally nicknamed the “ship of the desert.” By storing water in the form of fat in their humps, camels are able to travel long distances. For the indigenous nomadic peoples of the deserts, camels are the basis of their economy. Desert soils are not rich in humus, however, they often contain many minerals and are suitable for agriculture. The main problem for plants remains water shortage.

Deserts of the world

The bulk of the world's deserts lie on platforms and occupy very ancient land areas.

Asian, African and Australian deserts are located above sea level at an altitude of 200 to 600 m.

The deserts of Central Africa and North America lie at an altitude of 1000 m.

Some deserts border mountains, while others are surrounded by mountains. Mountains are an obstacle to the passage of cyclones, so precipitation will only fall on one side of the mountains, and on the other there will be little or no precipitation.

The reason for the formation of deserts is the uneven distribution of heat and moisture, as well as the geographical zonation of the planet.

Temperature and atmospheric pressure create special conditions for the circulation of atmospheric air masses and the formation of winds. It is the nature of the general atmospheric circulation and the geographical conditions of the area that create a certain climatic situation, due to which a desert zone is formed in both the northern and southern hemispheres.

There are different types of deserts depending on the natural areas and surface type.

Deserts are:

• sandy;
• rocky;
• clayey;
• salt marshes.

Without Antarctica, the planet's deserts occupy 11% of the land surface, or more than 16.5 million square meters. km. They are distributed in the temperate zone of the Northern Hemisphere, as well as in the Southern Hemisphere within the tropical and subtropical zones.

From the point of view of moisture, some deserts have not received precipitation for decades, and deserts in extra-arid regions receive less than 50 mm per year.

Aeolian landforms are widespread in deserts, while the erosional type of relief formation is weakened.

Deserts are mostly drainless, but sometimes they can be crossed by transit rivers, for example, the Amu Darya, Nile, Syr Darya, Yellow River, etc.

Drying rivers - in Africa these are wadis, and in Australia - creeks and lakes that change their size and shape, for example, Eyre, Chad, Lop Nor.

Desert soils are poorly developed, and groundwater is often mineralized.

Vegetation cover is very sparse, and in very arid deserts it is completely absent.

In places where there is underground water, oases with dense vegetation and reservoirs appear in deserts.

Snowy deserts formed in the Arctic Circle.

In deserts such amazing phenomena can occur that do not exist in other natural areas.

Among these phenomena is “dry fog”, which occurs during calm weather, but the air is filled with dust and visibility completely disappears.

At very high temperatures, the phenomenon of “dry rain” can occur - precipitation evaporates before reaching the surface of the earth.

Note 2

Tonnes of moving sand can produce high-pitched, melodious sounds with a metallic tint, and they are called “singing sands.” You can also hear in the desert both the “sound of the sun” and the “whisper of the stars.”

Stones bursting at 40-degree heat are capable of making a special sound, and at a temperature of -70...-80 degrees, water vapor turns into ice crystals, which collide with each other and begin to rustle.

Definition 1

Thus, a desert is a special natural zone that has an almost flat surface with sparse or almost absent flora and specific fauna

Semi-deserts of the world

Semi-desert or otherwise deserted steppe is formed under dry climate conditions.

They have specific vegetation and soil cover and are characterized by the absence of woody vegetation.

As a rule, they combine elements of steppe and desert landscapes well.

In the north, the semi-desert is limited by the steppe and desert in the south.

The semi-deserts of the temperate zone go from the west from the Caspian lowland to the east of Asia to the eastern border of China, which is approximately 10 thousand km.

Subtropical semi-deserts are quite widespread on the slopes of plateaus, plateaus and highlands, for example, the Anatolian Plateau, the Iranian Plateau, the foothills of the Andes, the valleys of the Rocky Mountains, etc.

Tropical semi-deserts occupy large areas, especially in Africa; for example, the Sahel zone in West Africa is located south of the Sahara and has the appearance of a deserted savannah.

Russian semi-deserts occupy a small area. This is the Caspian lowland, which is a transition zone between steppes and deserts. In addition, it is the most northwestern edge of the vast Eurasian deserts.

The Caspian lowland receives the largest amount of total solar radiation per year on the territory of the Russian Plain.

The climate of the semi-desert is continental, which distinguishes it from the steppes. There is a pronounced high summer temperature of +22...+25 degrees, and cold winters with little snow.

January temperatures range from -12...-16 degrees. The winter period is characterized by strong winds, low snow cover and soil that freezes up to half a meter deep. The short spring accounts for the highest amount of precipitation, the annual amount of which is 300 mm with evaporation of 800 mm.

Desert and semi-desert climate

Deserts and semi-deserts of the world occupy several climatic zones - the temperate zone of the Northern Hemisphere, the subtropical and tropical zone of the Northern and Southern Hemispheres, the polar zone where ice deserts form.

The predominant climate is continental with very hot summers and cold winters.

Precipitation, as a rule, is a very rare occurrence for deserts - from once a month to once every few years.

Small amounts of precipitation do not reach the surface of the earth and evaporate immediately into the air.

In tropical and subtropical deserts, the average temperature during the day ranges from +50 degrees during the day to 0 degrees at night. In the Arctic deserts up to -40 degrees.

The maximum temperature, for example, in the Sahara was +58 degrees.

In tropical deserts, daily amplitudes are 30-40 degrees; in temperate deserts, they are about 20 degrees.

During the day, the desert air is also dry - from 5 to 20% during the day, and from 20 to 60% at night.

The driest deserts are those of South America. Low air humidity in deserts does not protect the surface from solar radiation.

In the deserts of the Atlantic and Pacific coasts, as well as the Persian Gulf, the climate is more favorable, because air humidity due to the proximity of water increases to 80-90%, and daily temperature fluctuations decrease. In such deserts there is sometimes even dew and fog.

Temperate deserts are characterized by seasonal fluctuations - warm and even hot summers and severe winters with frosts down to -50 degrees. There is little snow cover.

A characteristic phenomenon for all deserts is constantly blowing winds. Their speed can reach 15-20 m/s. Their formation is caused by strong heating of the surface and the resulting convective air currents, as well as the terrain, which is why sand and dust storms are frequent in deserts.

The winds have their own names - in the Sahara it is sirocco, in the deserts of Libya and Arabia - gabli and khamsin, in Australia - brickfielder, and in Central Asia - Afghan.

The queen of deserts is the largest among the hot ones - the Sahara, located in North Africa.

For most of the year, the Sahara is influenced by the northeast trade wind. The Atlas Mountains are a barrier to the penetration of humid Mediterranean air into the Sahara.

The July temperature is +35 degrees in the central part, but in many places it is +50 degrees. At night, the thermometer drops to +10...+15 degrees.

Daily temperatures are high and amount to 30 degrees, and on the soil surface they reach 70 degrees.

According to the precipitation regime, three zones are distinguished - northern, central, southern.

In the north, precipitation falls no more than 200 mm in winter. In the central zone, precipitation occurs sporadically, and its average value does not exceed 20 mm. Within 2-3 years they may not fall out at all. But sometimes there are heavy rainfalls in such areas, causing severe flooding.

The Sahara changes its aridity from west to east. The Atlantic coast is dry because the Canary Cold Current, which runs along the western coasts, cools the air and there is often fog.

Due to the condensation of water vapor, precipitation increases slightly at the tops of mountain ranges and in the highlands. The Sahara is characterized by a high degree of evaporation.