And semi-deserts are specific natural zones, the main distinguishing feature of which is drought, as well as poor flora and fauna. Such a zone can form in all climatic zones - the main factor is a critically low amount of precipitation. Deserts and semi-deserts are characterized by a climate with a sharp daily temperature difference and a small amount of precipitation: no more than 150 mm per year (in spring). The climate is hot and dry, evaporates before it can be absorbed into the water. Temperature changes are characteristic not only of the change of day and night. The winter and summer temperature difference is also very large. The general background of weather conditions can be defined as extremely severe.
Deserts and semi-deserts are waterless, dry areas of the planet where no more than 15 cm of precipitation falls per year. The most important factor in their formation is wind. However, not all deserts experience hot weather; some of them, on the contrary, are considered the coldest regions of the Earth. Representatives of flora and fauna have adapted to the harsh conditions of these areas in different ways.
Sometimes the air in deserts in summer reaches 50 degrees in the shade, and in winter the thermometer drops to minus 30 degrees!
Such temperature changes cannot but affect the formation of the flora and fauna of the semi-deserts of Russia.
Deserts and semi-deserts are found in:
- The tropical belt is most of these territories - Africa, South America, the Arabian Peninsula of Eurasia.
- Subtropical and temperate zones - in South and North America, Central Asia, where the low percentage of precipitation is complemented by relief features.
There are also special types of deserts - Arctic and Antarctic, the formation of which is associated with very low temperatures.
There are many reasons why deserts arise. For example, the Atacama Desert receives little rainfall because it is located at the foot of the mountains, which cover it from rain with their ridges.
Ice deserts formed for other reasons. In Antarctica and the Arctic, the bulk of the snow falls on the coast; snow practically does not reach the interior regions. Precipitation levels generally vary greatly; one snowfall, for example, can result in a year's worth of precipitation. Such snow deposits form over hundreds of years.
Natural area desert
Climate features, desert classification
This natural area occupies about 25% of the planet's land area. There are 51 deserts in total, 2 of which are icy. Almost all deserts were formed on ancient geological platforms.
General signs
The natural zone called “desert” is characterized by:
- flat surface;
- critical volume of precipitation(annual norm - from 50 to 200 mm);
- rare and specific flora;
- peculiar fauna.
Deserts are often found in the temperate zone of the Earth's Northern Hemisphere, as well as in the tropical and subtropical zones. The relief of such an area is very heterogeneous: it combines highlands, island mountains, small hills and strata plains. Basically, these lands are drainless, but sometimes a river can flow through part of the territory (for example, the Nile, Syr Darya), and there are also drying lakes, the outlines of which are constantly changing.
Important! Almost all desert areas are surrounded by or near mountains.
Classification
There are different types of deserts:
- Sandy. Such deserts are characterized by dunes and often experience sandstorms. The largest is the Sahara, characterized by loose, light soil that is easily blown by the winds.
- Clayey. They have a smooth clay surface. They are found in Kazakhstan, the western part of Betpak-Dala, on the Ustyurt plateau.
- Rocky. The surface is represented by stones and rubble, which form placers. For example, Sonora in North America.
- Salt marshes. The soil is dominated by salts, and the surface often looks like a salt crust or quagmire. Distributed on the coast of the Caspian Sea, in Central Asia.
- Arctic— located in the Arctic and Antarctica. They can be snowless or snowy.
Climatic conditions
The desert climate is warm and dry. The temperature depends on the geographical location: the maximum +58°C was recorded in the Sahara on September 13, 1922. A distinctive feature of the desert area is a sharp temperature drop of 30-40°C. During the day the average temperature is +45°C, at night - +2-5°C. In winter, the deserts in Russia can be frosty with light snow.
In desert lands it has low humidity. Strong winds with a speed of 15-20 m/s or more often occur here.
Important! The driest desert is the Atacama. There has been no rainfall on its territory for more than 400 years.
Semi-desert in Patagonia. Argentina Flora
The desert flora is very sparse, consisting mainly of sparse shrubs that can extract moisture deep in the soil. These plants are specially adapted to live in hot and dry habitats. For example, a cactus has a thick waxy outer layer to keep water from evaporating. Sagebrush and desert grasses need very little water to survive. Desert and semi-desert plants have adapted to protect themselves from animals by growing sharp needles and thorns. Their leaves are replaced by scales and spines or covered with hairs that protect the plants from excessive evaporation. Almost all sand plants have long roots. In sandy deserts, in addition to herbaceous vegetation, there is also shrub vegetation: zhuzgun, sand acacia, teresken. Shrub plants are low and poorly leafy. Saxaul also grows in deserts: white on sandy soils, and black on saline soils.
Flora of desert and semi-desert Most desert and semi-desert plants bloom in the spring, reproducing flowers until the hot summer begins. During wet winter and spring years, semi-desert and desert plants can produce a surprising amount of spring flowers. Pine trees, junipers and sage grow in desert canyons and rocky mountains. They provide shelter from the scorching sun for many small animals.
The least known and underestimated species of desert and semi-desert plants are lichens and cryptogamous plants. Cryptogamous or secretogamous plants - spore fungi, algae, pteridophytes, bryophytes. Cryptogamous plants and lichens need very little water to survive and live in dry, hot climates. These plants are important because they help stop erosion, which is very important for all other plants and animals because it helps keep the soil fertile during high winds and hurricanes. They also add nitrogen to the soil. Nitrogen is an important nutrient for plants. Cryptogamous plants and lichens grow very slowly.
Annual ephemerals and perennial ephemeroids grow in clay deserts. In solonchaks there are halophytes or solyankas.
One of the most unusual plants that grow in this area is saxaul. It often moves from place to place under the influence of the wind.
Fauna
The fauna is also sparse - reptiles, spiders, reptiles or small steppe animals (hare, gerbil) can live here. Among the representatives of the order of mammals, the camel, antelope, wild ass, steppe sheep, and desert lynx live here.
To survive in the desert, animals have a specific sandy coloration, can run fast, dig holes and live for a long time without water, and are preferably nocturnal.
Among the birds you can find the raven, saxaul jay, and desert chicken.
Important! In sandy deserts there are sometimes oases - this is a place that is located above the accumulation of underground water. There is always dense and abundant vegetation and ponds here.
Leopard in the Sahara desert Characteristics of the climate, flora and fauna of the semi-desert
Semi-deserts are a type of landscape that is an intermediate option between desert and steppe. Most of them are located in the temperate and tropical zones.
General signs
This zone is distinguished by the fact that there is absolutely no forest on it, the flora is quite unique, as is the composition of the soil (very mineralized).
Important! Semi-deserts exist on all continents except Antarctica.
Climatic conditions
They are characterized by hot and long summers with temperatures of approximately 25°C. Evaporation here is five times higher than precipitation levels. There are few rivers and they often dry up.
In the temperate zone they run in an unbroken line across Eurasia in an east-west direction. In the subtropical zone they are often found on the slopes of plateaus, highlands and plateaus (Armenian Highlands, Karoo). In the tropics these are very large areas (Sahel zone).
Fennec foxes in the desert of Arabia and North Africa Flora
The flora of this natural zone is uneven and sparse. It is represented by xerophytic grasses, sunflowers and wormwood, and ephemerals grow. On the American continent, the most common are cacti and other succulents; in Australia and Africa, xerophytic shrubs and low-growing trees (baobab, acacia) are most common. Here the vegetation is often used to feed livestock.
In the desert-steppe zone, both steppe and desert plants are common. The vegetation cover mainly consists of fescue, wormwood, chamomile, and feather grass. Often wormwood occupies large areas, creating a dull, monotonous picture. In some places, kochia, ebelek, teresken, and quinoa grow among the wormwood. Where groundwater comes close to the surface, thickets of shin weed are found on saline soils.
The soil, as a rule, is poorly developed; its composition is dominated by water-soluble salts. Among the soil-forming rocks, ancient alluvial and loess-like deposits, which are reworked by winds, predominate. Gray-brown soil is typical for elevated flat areas. Deserts are also characterized by salt marshes, that is, soils that contain about 1% of easily soluble salts. In addition to semi-deserts, salt marshes are also found in steppes and deserts. Groundwater, which contains salts, when reaching the soil surface is deposited in its upper layer, resulting in soil salinization.
Fauna
The fauna is quite diverse. To the greatest extent it is represented by reptiles and rodents. Mouflon, antelope, caracal, jackal, fox and other predators and ungulates also live here. Semi-deserts are home to many birds, spiders, fish and insects.
Protection of natural areas
Some desert areas are protected by law and recognized as nature reserves and national parks. The list of them is quite long. From the deserts man guards:
- Etosha;
- Joshua Tree (in Death Valley).
Among semi-deserts the following are subject to protection:
- Ustyurt Nature Reserve;
- Tiger beam.
Important! The Red Book includes such desert inhabitants as the serval, mole rat, caracal, and saiga.
Chara desert. Transbaikal region Economic activity
The climatic features of these zones are unfavorable for economic life, but throughout history entire civilizations developed in the desert zone, for example, Egypt.
Special conditions forced us to look for a way to graze livestock, grow crops and develop industry. Taking advantage of the available vegetation, sheep are usually grazed in such areas. Bactrian camels are also bred in Russia. Farming here is possible only with additional irrigation.
The development of technological progress and the unlimited supply of natural resources have led to the fact that man has reached the deserts. Scientific research has shown that in many semi-deserts and deserts there are considerable reserves of natural resources, such as gas, precious minerals. The need for them is constantly increasing. Therefore, equipped with heavy equipment and industrial tools, we are going to destroy previously miraculously untouched territories.
- The two largest deserts on planet Earth: Antarctica and the Sahara.
- The height of the highest dunes reaches 180 meters.
- The driest and hottest area in the world is Death Valley. But, nevertheless, more than 40 species of reptiles, animals and plants live in it.
- Approximately 46,000 square miles of arable land turns to desert each year. This process is called desertification. According to the UN, the problem threatens the lives of more than 1 billion people.
- When passing through the Sahara, people often see mirages. To protect travelers, a mirage map was compiled for caravan drivers.
Natural zones of deserts and semi-deserts are a huge variety of landscapes, climatic conditions, flora and fauna. Despite the harsh and cruel nature of the deserts, these regions have become home to many species of plants and animals.
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 occurrence 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.
The flora of deserts in particularly severe ones may be completely absent; where moisture remains sufficient, some plants grow, but the flora is still not very diverse. Desert plants usually have very long roots - more than 10 meters - in order 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.
Raven), the other is characteristic only of deserts and semi-deserts. Among the mammals typical for this zone are the Bactrian camel, the goitered gazelle, the wild ass, the steppe sheep, the sand hare, the long-eared hedgehog, the comb-toed and woolly-footed jerboa, the slender-toed ground squirrel, the mouse-like rodents gerbils, the sand cat, the desert lynx, the hyena, the cheetah, and the caracal. Birds include the bustard, desert hen, crow, warbler, bullfinch, shrike, nightjar, lark, saxaul jay and sparrow.
In the deserts there are numerous lizards (grey monitor lizard, long-eared round-headed lizard, reticulated and striped foot-and-mouth disease, crested gecko), snakes (sand boa, cobra, viper, efa, arrow snake), and turtles (steppe). Invertebrates include beetles (anthia ground beetle, darkling beetle, saxaul woodcutter, slow dung beetle), spiders (karakurt, tarantula), Asian locust, termites, mosquitoes.
The tugai on the reservoirs are inhabited by the coot duck, pelican, egret, mute swan, avocet, etc. Wild boar, Bukhara deer, reed cat, jackal, and pheasant live in the thickets. In addition, birds that are satellites of human settlements nest in the desert and semi-desert zone: sparrow, swallow, stork, Senegalese dove, Indian oriole, paradise flycatcher.
The fauna of deserts and semi-deserts has a number of features associated with specific living conditions. For example, sparse, low-growing vegetation in open spaces and its periodic burning, on the one hand, cannot feed large herbivores in one place for a long time and forces them to make long journeys in search of food and water, and on the other hand, they have nowhere to hide from enemies and their only salvation is flight. This is why desert ungulates are excellent runners (gaiters, kulans). Their natural enemies - predators - in turn are not inferior to them in running speed (wolves and especially cheetahs). For birds, visiting distant watering places is possible if they have the ability to fly quickly. This is different, for example, from sajhi and sandgrouse, which inhabit predominantly wormwood and solyanka semi-deserts. Possessing long and sharp wings, they quickly cover a distance of up to 100 km during daily flights to bodies of water, where they immediately drink about 0.25 liters of water.
In addition to fast running and flying, many desert animals are characterized by jumping with the help of long hind limbs (jerboas, hares), increased maneuverability of movements (lizards, ground beetles, crickets, tarantulas), general mobility at a fast pace (dune cat, ferret, long-eared hedgehog , sand hare).
A significant part of desert inhabitants survive safely in open spaces thanks to the fact that they use burrows as shelters. In them they escape from enemies, heat and cold, they are in them during winter torpor or summer hibernation.
Many desert animals have various devices for digging holes: combs on their toes (for example, the crested jerboa, the lizard - the crested gecko) or brushes and bristles on the legs (in insects), with which they rake out soil particles. The process of digging holes itself is carried out using incisors (in vertebrates) and claws (in invertebrates). Animals often camouflage their burrows by placing them under a bush, stone, uneven ground or in thickets of herbaceous vegetation. Some burrowers close the entrance to the hole with a plug of earth or sand.
Many birds take refuge or nest in abandoned burrows of badgers, ground hares (jerboas), slender-toed ground squirrels and other desert mammals (for example, ground sparrow, shelduck, stonechat). However, birds are more willing to inhabit desert areas where there are cliffs, ravines, woody vegetation and water. They are attracted by such shelters as protection from wind and heat. Snakes (cobra, arrow-snake) hide in rodent burrows.
A means of protection from enemies is also the ability to dive into the sand in case of danger (for example, in round-headed lizards, sand boa, sand tarantula, etc.).
Animals that do not dig burrows camouflage their shelters located on the surface of the earth (for example, the beds of goitered gazelle, sand hare, or tolai). Desert coloration is also widespread among the most diverse groups of desert inhabitants, with a predominance of light sandy-yellow tones in the color of the coat (camel, goitered gazelle, kulan, sand hare, etc.), in the color of feathers (sadzhi, hazel grouse, steppe buzzards), in the color of scales (in lizards - monitor lizards, geckos, round heads), in the color of chitinous cover (in desert beetles, flies). In some cases, this coloring has a camouflage value.
Living in an open landscape requires desert dwellers to be very careful and take timely measures to save themselves if an enemy approaches. Well-developed organs of vision, hearing and smell help them in this. Among mammals, some run away, others hide in holes, and others hide. Birds behave in a similar way. Most of them occupy an elevated area, from where it is easier to spot danger, and here they remain alert. Some birds with short legs, sitting on the ground, notice the approach of the enemy only at close range. In this case, they hide (for example, sandgrouses) or, quickly working with their wings, cover themselves with dust, which contributes to camouflage (for example, some larks).
In deserts, animals have to experience high temperatures during the summer during the day and low temperatures during the winter and at night. That is why desert inhabitants, in the process of evolution, have developed various forms of adaptive behavior in connection with the characteristics of daily and seasonal activity.
Semi-desert constitutes the transition from steppes to deserts. Its landscapes are different
the following characteristics: whereas in the steppes vegetation forms, as a rule,
a continuous carpet, in semi-deserts we see areas between plants
bare soil, but still the area under vegetation, unlike deserts, is larger
areas of bare spaces; soils and soils, as well as surface and ground waters
usually salted; many salt lakes, a lot of salt marshes; the salt licks to the south freeze;
maximum precipitation in June and May; soils in the north are light chestnut, in the south
grey-brown;
soil
And
vegetable
cover
different
motley.
Geographical location of semi-deserts in Russia. Semi-desert occupies the area
the lower reaches of the Volga, starting on the right bank just below Dubovka, and in the Trans-Volga region it goes south
from the Saratov - Uralsk railway. To the west the semi-desert goes to the middle Don and
large Manych lakes, south to the lower reaches of the Sulak River, and beyond the Ural River the southern
its border goes approximately along the line: the mouth of the Emba - the northern cliff of Ust-urt -
north of the Aral Sea - north of Balkhash, including the Hungry Steppe or
Bedpakdala to the desert.
3. Climate. Climate type.
Deserts are common in the temperate zone of the Northern Hemisphere, subtropical and
tropical
belts
Northern
And
Southern
hemispheres.
The temperature regime of a desert depends primarily on its geographical
provisions. Desert air, having extremely low humidity, is practically
protects the soil surface from solar radiation. Temperatures of + 50° C are common, and
the maximum temperature recorded in the Sahara is 58° C. At night
the temperature is much lower, since the heated soil quickly loses heat. Daily allowance
Temperature ranges in deserts of the tropical zone can reach 40° C.
Temperate desert temperatures exhibit significant seasonal
fluctuations. Summer in such deserts is usually warm, even hot, and winter is cold, with
temperatures
below
0°
WITH.
The annual precipitation is less than 200 mm, in extra-arid areas - less than 50 mm, and in
some deserts have had no precipitation for decades; humidification coefficient, reflecting
the ratio of precipitation and evaporation is 0-0.15).
4. Typical Soils
These are dry steppes. There is humus in the soils of dry steppes
arrives less: grass is rarer, and black soil
cannot be formed. Plants have deep roots
because water often lies far from the surface,
and the humus horizon is quite powerful, but the humus in
it is much less than in chernozems. These soils
lighter, brown, chestnut color, that's why
called chestnut soils.
5. Inland Waters
In semi-deserts, a kind of dense micronetwork of local runoff is formed,
consisting of weakly expressed hollows and shallow depressions that collect
predominantly melted snow water. In this respect, the semi-desert differs significantly from
desert zones in which the surface runoff is so small that it is not sufficient for
formation of even a rare local runoff micronetwork. The presence of closed
basins and depressions contribute to the formation of shallow lakes containing usually
bitter salt water. Some lakes contain large reserves of self-propelled
table salt and healing mineral mud (Elton, Baskunchak).
The difficulties of water supply in semi-deserts are aggravated by the fact that groundwater here
are not abundant, often occur at great depths and due to salinity in
in most cases unsuitable for economic use. Poverty
local fresh waters sharply increases the importance of large transit rivers, which
there is relatively little here.
6. Typical Animals
The fauna of the deserts and semi-deserts of Russia is also quite diverse. Only during the day when
the scorching rays of the sun do not spare anyone or anything, few people can be seen here, most of the animals
are nocturnal - geckos, gerbils, jerboas, boa constrictors hide in deep holes during the day. From
The permanent residents here are mostly rodents: field mice, gophers and jerboas,
hamsters. A real guard can be called the gopher, which is like a column, wary
looks in all directions, and if he suddenly sees a person, he immediately emits a whistle - that means it’s time
hide. And everyone seems to fall through the ground - into their holes. Once upon a time, steppe people also lived here
marmots are bobaks, but today they are almost completely exterminated by hunters. Almost all rodents for the winter
hibernate, and some of them fall asleep even when it becomes unbearably hot. Rodents are
the main food for many predators, birds and snakes, the abundance of which is simply amazing. Of the large
animals stand out saigas. Just recently, these antelopes were on the verge of extinction, but
Thanks to environmental efforts, their numbers have increased. Saigas are very graceful even
when running at speeds up to 80 km/h!
A lot of birds appear in the semi-desert zone in spring and early summer. Some of them make their own
nests right in the ground. And their camouflage coloring saves them from danger, but the chicks very quickly
develop while avoiding unnecessary risks.
Even minor human intervention in the life of flora and fauna leads to its change and, to
unfortunately, not always for the good. The same thing happened with this natural area. Many plants
birds and animals are listed in the Red Book. Nature reserves have been created to save endangered species -
Bogdinsko-Baskunchaksky and Astrakhansky, reserves - Sands of Burley, Stepnoy, Ilmenno-Bugrovoy,
35 natural monuments were created
7.
SAIGAS
KORSAK
STEPPE MARCHOT
FIELD MOUSE
JERBOA
8. Typical Plants
BLOODROOT
CAMEL
TURNY
SANDY
ACACIA
vegetation
deserts
Russia
relatively
varied.
Full rights
masters
are considered
wormwood and ephemeroids, but many other cereals, cacti, camel thorn, ephedra,
kendyr, sand acacia, perennial
herbs and even flowers - tulips, remerias,
malkomiya. The conditions in which these people live
plants provoked the development of different
abilities
For
devices
survival: some plants quickly
wither, but at the same time retain their
organs (bulbs, tubers), while others go through a full life cycle in two to three months.
Deserts and semi-deserts of Russia
English РусскийRules
Tropical and subtropical deserts and semi-deserts
A significant part of the land on the globe is occupied by deserts, semi-deserts and arid zones. The desert biome is characteristic of zones of the Earth where rainfall is less than 250 mm per year. Tropical and subtropical desert biomes are found in the driest areas of the tropical climate zone and in the subtropical arid climate, or trade wind zone.
The trade wind zone is adjacent to the Northern and Southern Tropics, extending approximately between 25° and 30° latitude. Average annual temperatures in this zone are high (25-30 °C), but very sharp daily temperature changes of 40-50 °C are characteristic, which significantly exceed the differences between winter and summer average daily temperatures (10-20 °C); Night frosts are possible. Precipitation in the form of rain, frost, dew or fog is scanty: less than 300 mm/year, and in many areas less than 100 mm/year.
They fall more or less evenly throughout the year or are confined to the “wet” season, which falls either in winter or summer. In some places there are two “wet” seasons, and in some places there are years without any precipitation at all.
The zone of tropical and subtropical deserts and semi-deserts is most extensive in the Northern Hemisphere of the Old World, where it stretches from the eastern Canary Islands through all of North Africa (Sahara), Southern Eritrea, Somalia, the Arabian Peninsula, Southern Iran and Pakistan to Northwestern India; in the New World it is represented in Northern and Central Mexico, Arizona and California.
In the Southern Hemisphere, tropical and subtropical deserts and semi-deserts are limited to the western coasts of South America between 4° and 24° S.
w. and South Africa between 18° and 28° S, as well as Central Australia, where they reach the coast in places in the northwest and south.
Desert vegetation varies from relatively dense thickets of low-growing shrubs (Figure 23) to areas completely devoid of higher plants (northern Chile, certain areas of the Libyan Desert).
The flora and structure of desert communities are greatly influenced not only by the amount of precipitation, but also by the characteristics of the substrate. Due to the scarcity of precipitation and low mortmass production by sparse vegetation, soil formation in deserts is extremely slow.
At the same time, the openness of the vegetation cover creates conditions for strong wind erosion of the substrate. The consequence of both processes is that the properties of soils are almost entirely determined by the granulometric composition of the bedrock.
It is the properties of geological rocks and the nature of their physical weathering that determine the type of desert.
Figure 23 – Profile of tropical scrub desert
Least favorable for the life of higher plants rocky And gravel deserts in which intense wind erosion has removed the fine-grained component of the substrate.
Therefore, the surface of such deserts is represented by continuous layers of stones such as cobblestones or gravel. The surface of the stones practically does not retain moisture, which easily seeps through large cracks, becoming unavailable for use by plants. Therefore, such deserts are either completely devoid of higher vegetation, or very rare higher plants live in cracks and crevices of rocks.
Sandy Deserts are generally more favorable for plant habitat, since sands retain water well in the soil horizon accessible to plants.
Semi-deserts and deserts of Russia are interesting areas in everything
These deserts vary greatly depending on the mobility of the substrate. On highly mobile sands, vegetation is completely absent. Low-moving sands are inhabited by a few shrub and perennial herbaceous species, adapted to tolerate both being covered with sand and exposing the root system when sand is blown out from under the plant.
The richest vegetation is on the still sands. Here live plants that develop a very deep root system, thanks to which they can extract water from the constantly moist horizons of the pound, as well as succulents with a superficial root system, adapted to quickly absorb water from rare rains and retain it in their body for a long time.
Some types of sandy deserts have a variety of ephemeroids and ephemera.
Fine-grained material blown out and washed out of the pound accumulates in low areas of the relief, which leads to the appearance there clayey deserts. Such places receive more moisture, coming with the flow of water through temporary surface watercourses and through the capillary system of the pound. With good drainage in the clay desert, ephemerals develop especially well, taking advantage of short periods of increased soil moisture after rare rains.
If there is no outflow of water, then the moisture in the soil solutions evaporates, and the salts they bring accumulate in the soil. As a result, salinity develops, which has an extremely depressing effect on most terrestrial plants (Figure 24). Only some higher halophytic plants are able to live on saline soils. Very highly saline areas, where a salt crust protrudes on the soil surface, are usually devoid of higher plants.
Tropical and subtropical deserts are very different floristically, since they are located in the territories of different floristic kingdoms, but the types of their formations are similar.
Shrub and subshrub formations consist of flocks of scleromorphic and usually thorny plants with small, entire, falling leaves or leaves strongly reduced to small scales and photosynthetic stems. During particularly long droughts, such shrubs fall into suspended animation, in which some species can remain for several years without harm.
At the same time, they dry out greatly, some even to an air-dry state, and after rain, within a few days they restore normal vegetation, flourish and form mature seeds in 2 - 3 weeks. The herbaceous layer consists of different ephemeroids and ephemera.
Ephemera can also form independent formations without the participation of shrubs. Some deserts are characterized by formations of perennial grasses, in which the main role is played by narrow- and stiff-leaved grasses, belonging to different roles in different phytochories.
In American and African deserts, there are special formations of succulents that are difficult to compare with the usual types of formations in other regions due to the unique life forms of the plants that compose them.
Stem succulents range in size from large tree-like forms to small plants that can be likened to turf grasses. In the New World, all this diversity is represented by different species and genera of the Cactus family ( Cactaceae), and in Africa - surprisingly similar cactus-like euphorbias (Euphorbia) and various representatives of the Lastovnevye family ( Asclepiadaceae).
A prominent component of succulent formations are large rosette leaf succulents: agaves (Agave) in America and rosette aloe (Aloe) and Aizoonaceae ( Aizoaceae) in Africa.
An extremely unique type of desert is represented by coastal foggy deserts (Chilean-Peruvian and Namib), stretching in a narrow strip up to 100 km wide along the western coasts of South America and South Africa, respectively.
Figure 24 – Profile of desert vegetation in a relief depression: 1-sandy desert with parfolia (Zygophyllum sp.) and tamarisk (Tamarix sp.); 2- area of salinity manifestation: 3 - saline clay desert with tamarisk (Tamarix sp.): 4 - crusty solonchak without higher plants.
In these deserts there is almost no rain, but fogs are very frequent, on the coast itself - nightly.
It is the moisture of fogs, condensing on the ground and plants, that becomes the main source of moisture for the plants and animals living there. Some plants of coastal foggy deserts have learned to absorb moisture condensing on their shoots directly with their leaves and stems. A number of species of American tillandsias ( Tillandsia) They do it so successfully that they do without roots at all.
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Semi-deserts- landscapes located between the steppe and the desert in temperate and subtropical geographical areas, as well as between the savannah and the desert in the tropical geographical zone.
Semi-dry are formed in dry climatic conditions. In total for all of them - a long hot and warm period (average temperature 20-25 ° C, and in the tropics 30 ° C), strong evaporation, which is 3-5 times higher than the amount of annual precipitation (100-300 mm per year) , poor surface drainage, inland waters are poorly developed, many drying channels, vegetation is not covered.
Despite the common characteristics of all semi-arid deserts, they have many differences.
Temperate Crescents in Eurasia, a wide strip (up to 500 km) extends from the western part of the Caspian lowlands, through Kazakhstan, Mongolia to Eastern China. In America, semi-deserts appear with shorter injuries in the interior and foothills.
Among the semi-deserts located in the tropical and subtropical groups, they are characterized by cold winters (up to -20 ° C).
Semi-deserts
The soil here is light chestnuts, which suit the steppe and brown desert, often a physiological solution. If we move south along the temperate zone hemi-basins, we see that the characteristics of stairs disappear and the characteristics of deserts increase. There are also meadows and corn stalks, and among them you already see wormwood and salt. Animals have many wise men and turtles, snakes and lizards.
second Crescents of the subtropical group.
They are mainly located in the transition from desert to mountainous steppes as a high altitude zone in the Cordillero and Andorra, Western Asia, Australia and especially Africa.
The floors are pebbled, taupe and grey. Grains and various types of shrubs, there are many cacti here. The animal world is dominated by rodents, snakes and lizards.
third Tropical Crescents.
These are desert savannas. They define both the desert and the sea coast - in Africa, the Sahara and Kalahari, in South America the Atacama in the north and northwest of the Brazilian Highlands, Asia and Australia.
The floors here are thin and red-brown.
The temperature in the tropical halves, even in the coldest months, does not fall below + 10 ° C, and in summer it rises to 35 ° C. Here they are very rare. Precipitation does not exceed 200 mm per year. Due to lack of moisture, the corn is very thin. Groundwater in tropical deserts is very deep and partially saline.
Only plants that can tolerate overheating and dehydration can live in such conditions.
They have a deeply rooted root system, small narrow leaves or thorns; Some plants have leaves coated or coated with wax that protects them from sunlight. These include herbaceous grass, agave, cactus, and sand acacia.
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Deserts and semi-deserts of Russia
Plants of deserts and semi-deserts in Russia
The peninsular zone enters the Russian lowland only in the southeast, where Ergeni and the northern half of the Caspian Plain are occupied. Its southern border west of the Volga is approximately 150 km from the Caspian Sea coast; in the Volga and the Urals it moved even further away from the sea and here: lake, Lake Baskunchak Aralsor - the mouth of more or less Uzen - the Ural River south of Kalmykov.
The situation in the southeast of the Russian Plain in the depths of the Eurasian continent is determined by the harsh continental dry climate of this zone.
Summer in semi-deserts is hot and sunny. The average July temperature reaches 23-25°, in the city of Novouzensk during the warm period 85 days occur with dry winds.
Winter is as cold as on the Kola Peninsula: the average January temperature is -7-8 ° in the southwest of the region and -13-14 ° in the northeast. The snow cover is thin from 10 to 30 cm.
Emptiness and semi-desert of Russian deserts: where it is located, map, climate, flora and fauna
Total precipitation is 300-200 mm; this is three to four times less than the volatility value. For example, in Novouzensk the annual precipitation is 250 mm, and evaporation is 910 mm.
Surface flow is not important for half of the shelf, so it does not have its own river network. Groundwater is salty and generally not suitable for drinking.
In addition to climate, landscape areas are most strongly influenced by the geological and geomorphological characteristics of the area - low altitude, plains, weak erosion with logging, and the presence of saline bedrock and quartz rocks.
There is little sludge or spillage in the area. Instead of these forms of erosion, the widespread form of the basin - steppe depressions, outflows, litters, etc. occurs differently: from suffusion to sedimentation and tectonic karst (some floods).
Continental climate, flat landscapes and physiological soil contribute to the accumulation of salt in the soil of semi-deserts, including the ability to dissolve well.
Solonezes are characteristic of semi-deserts as light chestnut soils, which are zonal here.
Lack of soil moisture and salinity results in incomplete, curious, spreading vegetation. The abundance of cavity faces causes extreme diversity and complexity of vegetation and soil cover. Due to lack of moisture, even the slightest depression - a depth of 10-20 cm - causes sudden changes in the soil and vegetation.
It can be said that this is a complex semi-desert zone in which the grassy steps in depression are closely intertwined, the Pellino-salt desert on solonetzes and the Bilni-chamomile desert is actually semi-deposition on light brown soil.
In the animal world, semi-deserts play the exclusive role of rodents.
Among them there are many squirrels present in abundance and influence on the landscape, which are represented here by two species - the small grass squirrel living on the loamy plains and the yellow soils inhabiting the sand.
The occurrence of claws is very high. In some places on one hectare we can count up to 740-750 holes of polite squirrels. Protein emissions create microtopography characteristic of the Caspian Sea, further increasing the complexity of soil cover and vegetation.
In addition to proteins, squirrels, rodents, coats of arms, sponges, voles, steppe varieties, and mice are common in polvircinine.
Within the range there is the saga antelope, which previously settled in the steppe and forest-steppe zones of the Russian Plain. There are wild pigs in the reeds of the river valleys. Wolves, wolves, leaf corsacs, and steppe grouse are common.
The composition of birds (steppe eagle, back, back), reptiles and insects is also quite diverse.
Much of the desert is used as pasture.
A lot of developed and irrigated agriculture is being developed.
In the semi-desert zone, two landscapes can be distinguished.
Instructions
Animals of the semi-deserts of Russia differ from other organisms in their unique ability to survive in such harsh conditions. Although semi-deserts are not yet deserts, the climatic conditions there leave much to be desired. In summer, the temperature in these places can reach 50°C and heat up to 70°C. In winter, in the semi-deserts of Russia, temperatures down to -30°C occur. During this time, the nature of the local semi-deserts comes to life: the ground is covered with green grass, irises, tulips, poppies, etc. bloom. But by the end of spring, all this safely burns out from the sun, leaving behind wormwood, thorns, cacti and other “dry” plants. Sometimes in Russian semi-deserts along rivers you can find trees and shrubs shrouded in vines.
Animals of Russian semi-deserts adapt to the harsh climate in their own way: they dig holes that help them hide from the heat during the day and protect themselves from enemies. Most of the animals in these places are nocturnal. In winter, on the contrary, they try to make all the necessary forays during the day, while there is at least some sun.
The permanent inhabitants of Russia's semi-deserts are rodents: voles, ground squirrels, hamsters, and jerboas. For example, gophers can generally be called real “sentinels.” Taking a firm stance, like a rooted post, he maintains his post: he warily peers at everything, looks around, and if he suddenly sees a predator or a person, he hurries to warn his fellow creatures about it. If a gopher whistles, it’s time to hide. All the other gophers, hearing the characteristic whistle, seem to fall through the ground into their holes.
In turn, rodents are food for larger animals (birds, snakes, large mammals) that live in the harsh Russian semi-deserts. Many of the local birds have adapted to make their own nests right on the ground. These feathered creatures are saved from enemies by their protective coloring, and their chicks grow quite quickly. Here you can also find steppe eagles, desert chickens, and even bustards. Egrets, pelicans, ducks and mucker swans nest near ponds.
The semi-deserts of Russia are inhabited by snakes such as cobra and viper, some species of turtles, and large poisonous spiders, tarantulas. Among the large animals in these places, hares, foxes, wolves and saigas are common. It is curious that the latter were considered an endangered species until recently, but actions aimed at protecting nature have borne fruit: the number of saigas has increased significantly. By the way, these small antelopes are called the pearl of Russian semi-deserts and deserts.
