Valuable plants of the desert. Vegetation in the desert

Deserts are common in areas where the climate is even drier and hotter than in the steppes. In our country, they adjoin the steppe zone from the south, but not along its entire length. Deserts are concentrated mainly in Central Asia and Kazakhstan. They also exist in the extreme southeast of the European part of the country (in the lower reaches of the Terek, the Volga and the Urals). There is a small array of them in Transbaikalia, on the border with Mongolia and China.

The main features of the desert climate are not a large number of rainfall (no more than 300 mm per year) and very strong summer heat (average temperature in July - about + 30 ° C). This makes the conditions for the existence of plants in the desert extremely difficult. It is especially unfavorable that the heat coincides with the dry period. It is in the summer, when precipitation is especially needed, that they are negligible. Sometimes there is not a drop of rain for several months. Evaporation in desert regions is many times higher than precipitation, plants almost constantly lack moisture. It is also unfavorable for plants in the desert that in summer the soil surface becomes very hot (up to 50-60 ° C). Such high temperatures not all representatives of the flora can tolerate. Finally, the desert is also characterized by extremely strong temperature fluctuations during the day. An unbearably hot summer day gives way to a very cold night. The same goes for the seasons. After a long hot summer, a rather severe winter sets in with frosts and snow cover (though very thin).

Desert soils are more or less saline, contain harmful easily soluble salts, which also affects plants negatively. Serozems and gray-brown desert soils are most characteristic of deserts.

The vegetation cover of deserts in different regions is not the same. However, almost everywhere it is more or less strongly sparse - the plants are far from being joined by their above-ground parts. The general appearance of the area, the colors of the landscape in the desert are usually determined not so much by plants as by soil. Extreme sparseness is a characteristic feature of the vegetation cover of deserts. The main mass of plants here are species that are especially resistant to drought (extreme xerophytes). To endure a sharp lack of moisture, they are helped by special devices that reduce evaporation: a greatly reduced leaf area, their dense pubescence, a thick film of a waterproof substance on the surface of the leaves (cuticle), etc. Sometimes the leaves are underdeveloped and are tiny scales. In this case, the functions of the leaves are taken over by green stems containing chlorophyll.

One of the adaptations for enduring a long summer drought is dropping leaves with the onset of heat. This phenomenon is very common in the desert. In some desert plants, even part of the young shoots of the current year fall off.

Succulent, fleshy plants (the so-called succulents) adapt in a peculiar way to the transfer of drought. Some of them have strongly thickened stems, while others have leaves. These plants store water in their aerial part (a special aquifer tissue serves for this). They are protected from strong evaporation by an outer integumentary tissue with a thick cuticle film on the surface. There are usually very few stomata in plants of this type, which also reduces water loss.

Along with xerophytes, there are also plants in deserts that cannot endure drought at all. We mean ephemera and ephemeroids. They develop only in spring, when the desert is quite humid and not yet hot. With the onset of the summer heat, all these plants completely complete their development and dry out. They seem to be running out of drought.

Finally, one more interesting type of plants can be found in deserts - the so-called phreatophytes, or pump plants. These plants, even during the most intense heat, when all living things are exhausted from the heat, stand with bright green leaves and open flowers, as if not feeling the scorching sun. The reason for this strange behavior is that the roots of pump plants penetrate extremely deep into the soil (up to 20-30 m) and reach the groundwater level. Therefore, these plants are always provided with water in sufficient quantities. That is why they are not afraid of any heat. An example of such plants can be a small semi-shrub camel's thorn.

As we saw in the previous chapter, the steppes are dominated by perennial grasses. The situation is quite different in the deserts. Here the leading role belongs to woody plants. Among them there are semi-shrubs, shrubs and even small trees (saxaul can be an example of the latter). The grasses in the desert are of no significant importance, except for the ephemera and ephemeroids, which develop for a very short time in the spring.

Desert plants belong to a wide variety of families. There are Compositae, and legumes, and cruciferous, and cereals. There are even some sedges. However, many of the most common desert plants belong to the haze family. This is a characteristic feature of the desert flora. In the vegetation cover of all other zones, the species of this family do not play a large role. Residents middle lane country, the haze family is unfamiliar. However, many people know a weed called quinoa or white gauze. This plant just belongs to the haze family. Beets also belong to the same family.

Wormwoods are also widespread in deserts, their role in the vegetation cover is also very large.

Deserts in our country are represented by several types - sandy, clay, saline. It is easy to see that this classification is based on soil characteristics. Soil conditions, as is known, are strongly reflected in the nature of vegetation. This dependence is especially great in the desert zone with its extremely harsh, extremely arid climate.

Whether the soil is sandy or clayey is extremely important for desert plants. This depends on the conditions of the water supply. And in the desert, water is the most important, determining factor. Whether a plant gets a little more or a little less water is a matter of life and death. It is not surprising, therefore, that different types of deserts have completely different vegetation cover.

The characteristic features of desert vegetation are most clearly expressed in clay deserts, to which we now turn. It is in this type of desert that the general appearance of vegetation and its other features are most closely related to climatic conditions and are entirely determined by them. Here, plants are content only with the amount of water that comes from the atmosphere with precipitation.

Clay deserts do not represent something uniform in vegetation throughout their entire length. They vary greatly in different areas. These differences are due to the frequency of precipitation. In some areas, precipitation falls throughout the year, but little by little, in small portions, while in others - mainly in the spring, but in relatively large quantities. Territories of the first type are common in the northern part of the desert zone, they are called northern clay deserts. The areas where precipitation is timed to coincide with spring are located in the south, these are the southern clay deserts.

The landscape of the northern deserts changes relatively little during the warm season, from spring to autumn. We see here a rather monotonous picture - grayish-greenish spots and clumps of plants against the background of a light brown soil surface. The vegetation cover is far from continuous, with large open spaces visible everywhere. Plants are squat, low - no higher than knee-deep. They seem to be spread out on the ground.

One of the most characteristic plants of the northern clay desert is gray earth wormwood (Artemisia terraealbae). It grows in the form of a small bush with a bluish, grayish-greenish color, does not attract attention to itself in any way. To get to know this polynya, it is best to dig it out with a shovel. The root of the plant is thick, strong, woody, extending deep into the soil. Of course, it will not be possible to extract it entirely - it is several meters long. Underground organs of wormwood in terms of power of development and weight are much superior to above-ground ones. This is typical of desert plants. Most of them are in the ground.

Several aboveground stems. In the lowest part, near the soil surface, they are very strong, woody, resembling thick rods. Above, the stems become thinner and softer, small leaves are visible on them. It is easy to guess that the upper part of the stem, bearing the leaves, is very young, it is only a few weeks old, or maybe months. The age of the lower, woody part is much older - several years. The further fate of the one and the other part is completely different. The young part of the stem dies in winter, while the old part is preserved, giving next spring new escape. Consequently, the stalk of wormwood is perennial only at the base, like in trees and shrubs, and throughout the rest of its length it is annual, like in herbs. Plants of this type are called shrubs. They are characteristic of our deserts.

In the northern desert, we also meet another semi-shrub - anabasis saline, or biyurgun (Anabasis salsa). It grows in a small dense bush, the height of which does not exceed 15-20 cm. This plant, like wormwood, has a powerful, thick root that penetrates deep into the soil. Woody stems extending from the root are spread over the surface of the earth, numerous green branches rise straight up from them, forming a dense bunch. Each branch is divided into small segments. Biyurgun leaves are very small, barely noticeable, oppositely arranged. They play almost no role in plant nutrition. Their functions are performed by green rod-shaped stems. This phenomenon is not uncommon among desert plants. The reduction in leaf area is a useful adaptation: it reduces evaporation.

Biyurgun belongs to the haze family. Its flowers are small, almost imperceptible. They are devoid of pedicels and sit directly on the stems, in their upper part, in fairly large numbers.

Another semi-shrub common in the northern desert is the leafless anabasis, or itsegek (Anabasis aphylla). This is a close relative of the Biyurgun already familiar to us (another species of the same genus). However, its bushes are much larger and taller. The thin green stems of the plant are directed upwards and strongly branched, which makes it somewhat similar to an ordinary broomstick sticking up. Lateral branches depart from the main branches in pairs, oppositely. The stems of the plant, divided into segments, break easily. The leaves are almost invisible. Small flowers sit directly on the stem in its upper part and do not catch the eye at all. The fruits are much more noticeable - they are equipped with large membranous wings of a rounded shape. During the fruiting period, itsegek seems to be transformed: the ends of the branches become shaggy from a multitude of round membranous processes. The plant appears to be in full bloom.

Itsegek is of great economic importance, as it contains the alkaloid anabazine, which is poisonous to insects. This substance, extracted from the plant, serves as the basis for the preparation of anabazine sulfate, which is widely used to control agricultural pests.

In the northern clay desert, it is also found black, or leafless, saxaul (Haloxylon aphyllum). This is one of the few trees that can grow in deserts. Saxaul is surprisingly hardy: it is able to endure extremely severe drought, unbearable heat, saline soil. The appearance of the saxaul is peculiar: the trunk of the tree is clumsy, winding, low; the crown is very loose, almost giving no shade. Saxaul has no leaves. Hanging down from the branches are long green twigs, thin as a knitting needle. They hang in bunches like strands of some strange thick hair. The wind shakes them and shakes them in all directions. If you pick a green twig of saxaul, you can see that it consists of separate segments that are tightly closed together. The plant has absolutely no leaves (hence the species name "leafless"). Black saxaul is named because its crown has a rather dark green coloring. This coloration persists in spring and summer. By autumn, the crown becomes orange-brown.

Saxaul belongs to the haze family and has small, inconspicuous flowers. They do not stand out on the plant. However, fruits equipped with membranous wings are very noticeable. From afar, they look like flowers.

In some places, the saxaul forms thickets, but they do not at all look like real forests. The trees are very low, no more than 4-5 m tall, stand far apart, there is no shade under them. On hot summer days scorching rays the sun heats up the soil so much that even desert lizards climb trees. Often saxaul grows in the form of a bush. And then its thickets are somewhat reminiscent of rare shrub willows along the sandy banks of the large Central Russian rivers.

Saxaul lives for a relatively short time - rarely more than 50-60 years. Old trees, with their small height, however, have a relatively thick trunk at the bottom (its thickness at the root can reach 35-40 cm). Up the trunk quickly disappears. Saxaul wood is very hard and heavy. It is an excellent fuel, very valuable in desert regions. Previously, the saxaul was intensively cut down, so its thickets were destroyed on vast areas. Currently, measures are being taken to restore saxaul forests.

These are major plants northern clay desert. Due to the fact that this type of desert is usually dominated by sagebrush and representatives of the haze family (the so-called saltworts), deserts of this type are called saltwort-sagebrush. Nai large areas we find such deserts in Southern Kazakhstan (to the south of the line: the lower reaches of the Ural River - Chelkar - Aktogay).

Let us now turn to the southern clay deserts. The living conditions of plants and the vegetation itself are completely different here than in the north. The appearance of the southern desert varies greatly during the growing season. In the spring, when it rains and it is already warm enough, the soil is covered with a solid green carpet of grass, like in a meadow. Only this carpet is very low, squat. By the summer, with the onset of drought, the vegetation completely burns out. The surface of the soil becomes completely dry and at the same time hard as a stone. There are no plants left on it. This continues for about nine months of the year.

In the southern desert there are almost no semi-shrubs, herbaceous plants dominate. The vast majority of them are ephemera (annual plants) and ephemeroids (perennials). Such a desert is called ephemeral.

One of the most common plants of the southern desert - sedge short columnar(Carex pachystilis). Its leaves are very narrow, and the plant itself is relatively small. In order to see the characteristic features of this sedge, it must be dug out of the ground. The underground part of the plant is much more powerful than the aboveground. A horizontal rhizome is located shallow in the soil - rather thick, almost like a pencil, and at the same time long. Numerous and unusually highly branched thin roots grow from it, which densely penetrate the upper soil layer. In sedge thickets, the soil is so saturated with roots and rhizomes that it is difficult for a shovel to penetrate it. The concentration of roots in the upper soil layer has for the plant importance. Indeed, during the spring rains, it is this layer that is wetted with water; water hardly penetrates deeper into the clay.

In the spring, when the rains have passed, the sedge thickets resemble green lawn- the earth is completely covered with young tender greenery. At this stage of development of vegetation, this is an excellent pasture. Sedge in springtime is an excellent fodder plant. But this does not last long. Very soon the heat comes, and the sedge dries up, burns out. In the summer there is no trace of her. Only in the soil, like in other ephemeroids, underground organs remain alive. They sometimes dry up almost to a crunch, but do not die.

Another plant of the same type is bulbous bluegrass (Poa bulbosa). This plant is also small and goes through exactly the same development cycle as the sedge. But the appearance of bluegrass and the features of its structure are completely different. The plant forms small dense turfs with numerous thin shoots rising up. At the base, the shoots are thickened like small elongated bulbs. These bulbs, being released under the blows of the hooves of livestock or as a result of the natural destruction of turfs, can give rise to new plants.

Bluegrass inflorescences are small panicles with small spikelets. Interestingly, in the inflorescences, instead of individual spikelets, tiny shaggy bulbs often develop. They serve as a means of reproduction and, having fallen to the ground, germinate, giving a new plant. Sometimes, in wet weather, the germination of the bulbs occurs already in the panicle, that is, right on the mother's shoot. In dry years, the bulbs lie on the ground until the next spring. They perfectly tolerate long summer drought. These bulbs do not die for a long time when stored dry. Having lain for several years in the herbarium together with the mother plant, they remain alive.

Bulbous bluegrass is a perennial plant. This is a typical ephemeroid. It is green only in spring. In the summer all above-ground part dries up completely, and in early spring, with the onset of rains, development begins again.

In the southern deserts, another group of plants is also well represented - annual grasses, which quickly develop from seeds in spring and dry out by summer, that is, ephemera. Among them are, for example, spring grits, desert beetroot, some spurges, astragalus, etc. The period from seed germination to the formation of new seeds in these plants is extremely short - sometimes less than two months.

These are main features southern clay deserts and some of the most common representatives flora. Deserts of this type can be found in the extreme south of Central Asia (to the west of Ashgabat, in the Kushka region, between Dushanbe and the border with Afghanistan).

Let's get acquainted now with the sandy deserts occupying huge spaces in Central Asia and partly in Kazakhstan. The most famous of these deserts are the Karakum and Kyzylkum. In its natural, more or less preserved state, the sandy desert is something quite peculiar, unlike other types of deserts. To the very horizon, as far as the eye can see, there are large hills that look like gigantic sea ​​waves frozen in immobility. The surface of the earth is covered with thickets of shrubs, and, moreover, quite high. In these thickets sometimes you can not see a person. The dominance of the bushes is the most characteristic sandy desert.

It is most interesting to visit the sandy desert in spring. The shrubs are in full bloom, and it seems that you are in some kind of amazing garden. Individual bushes do not grow too densely, and a delicate green cover of young grass is everywhere visible on the soil. In some places, small trees of white saxaul with sparse bluish crowns rise above the bushes. In places, saxaul forms entire groves.

The sandy desert has a rich and varied flora. Not only shrubs grow here, but also perennial grasses, ephemeral annuals, semi-shrubs, and trees.

The pomp and richness of the flora is explained by the fact that the sandy desert is more humid than the clay one. It sounds paradoxical, but it is true nonetheless. The fact is that sand easily absorbs water from atmospheric precipitation, but hardly gives it away. Sandy soil, consisting of relatively large particles, is easily permeable to moisture. However, the friability of such soil, the absence of capillaries in it greatly slow down the reverse evaporation. In addition, sand in desert conditions has the ability to condense water vapor that is in the atmosphere. On cold summer nights, water vapor, easily penetrating into the sandy soil, condenses in it. The sand is somewhat dampened, but certainly not completely wet. However, even this small additional amount of water greatly affects the plant world, improves the living conditions of plants during a long summer drought. If you dig a deep enough hole in the sandy desert in summer, you can be sure that the sand is wet not in its entire thickness, but only at a certain depth (no deeper than 1-2 m from the surface). This is a constant moisture horizon that persists all year round. It is he who nourishes the plants with moisture in the summer. In spring, there is another wet horizon in the soil - the uppermost one. It is moistened by melting snow and spring rains. From the deeper layer, mainly trees and shrubs draw water, from the uppermost layer, mainly grasses,

Let us now turn to the trees and shrubs of the sandy desert. Here is one of these plants - sand acacia, or suzen(Ammoden-dron conollyi). This is a small tree or shrub several meters tall. In spring, the sand locust attracts attention with its greenish-silvery foliage and unusual blackish-purple flowers. The flowers are relatively small, collected in long inflorescences-brushes. They have a structure characteristic of legumes (acacia belongs to this family). The complex leaves of the plant are quite peculiar: each of them consists of a short, sharp petiole, similar to a thorn, and two narrow, long leaves. These leaves do not sit at the end of the spine, but approximately in the middle of its length. When the leaves fall, the spine is exposed. The surface of the leaves is covered with dense silvery-silky pubescence. Acacia fruits are also peculiar - flat, spirally curved beans. They are similar in shape to a propeller.

Sandy acacia (separate fruit); Chingil - a branch with fruits

The sand locust is one of the thorny desert plants. Such plants are not uncommon in deserts.

Another plant of the sandy desert is silver chingil (Halimodendron argenteum). This shrub also belongs to the legume family. Its branches are covered with sharp strong spines, reaching 6 cm in length. Spines extend from the stem at almost a right angle. During flowering at the base of the spine, between it and the stem, a loose bunch of large purple flowers appear, sitting on rather long pedicels (sometimes the flowers are almost white). There are also small paired pinnate leaves of the plant, consisting of one to five pairs of leaflets.

The fruits of chingil are very peculiar - strongly swollen leathery beans, similar to fish bubbles. Such light fruits, once on the surface of loose, loose sand, never sink into it. The wind rolls them in different directions, but the sand cannot fall asleep. This is useful for the plant: the fruits cannot be buried too deep in the sandy layer.

But the most remarkable shrubs of the sandy desert are the various types of juzgun (Calligonum). Juzgun is interesting primarily because it looks completely leafless. It seems that the shrub consists of only one branch - thicker and thinner. But in fact, the plant has leaves. True, they are very small and inconspicuous, the functions of the leaves are performed by thin green twigs that appear on the plant every spring. Dzhuzgun is a strongly branched shrub, its branches are usually articulated and winding. They are completely smooth, there are no thorns on them. The height of the plant can reach several meters. It is also interesting that juzgun belongs to the buckwheat family. Almost all representatives of this family are grasses, and juzgun and a few other shrubs are an exception.

The fruits of juzgun are very original. In different species, they are different in appearance. In some species, the fruits are similar to miniature hedgehog, in others - on a small ball of tangled red hair, in others - they surprise with their bizarre membranous processes. The fruit itself is a small, very hard nut. Its surface in many species of juzgun is completely covered with numerous long bristles sticking out in all directions. The bristles are rather stiff, intertwined. Thanks to this, the fruit retains its spherical shape well and always looks loose and fluffy. In other types of juzgun, several wide pterygoid processes extend from the surface of the nutlet in different directions, and the general shape of the fruit also remains spherical. All these processes, of course, are not just decoration. They are vital to the plant. Loose, light fruits, similar to balls, roll freely on the surface of loose sand and never sink deep into it. Driven by the wind, they roll along the dunes and bounce like balls. Sand can never fill them up, even during strong storms.

In the sandy deserts of Central Asia, juzgun is used by the local population as fuel. Solid wood of larger specimens is sometimes used for small household crafts. Juzgun is also planted on moving, wind-blown sands to secure them. It is one of the best sand binders. The reproduction of juzgun does not present any particular difficulties: its cuttings quickly take root, and the seeds germinate well. The plant also has a fodder value: its shoots and fruits are eaten by livestock.

White saxaul (Haloxylon persicum) is often found in the sandy desert. This tree, reaching 5 m in height, in many ways resembles the black saxaul already familiar to us. True, the color of its crown is somewhat lighter, slightly whitish. This impression is created by the fact that the branches of the previous year have almost White color, and the shoots of the current year are light green. The trunk of the tree is curved, gnarled, covered with light gray bark. The wood is very strong and so heavy that it sinks in water. It breaks quite easily, but does not prick. This is a very valuable fuel, giving a lot of heat (almost as much as coal). White saxaul differs from black in that it has very poorly developed, but still quite distinguishable leaves. They look like small scales, turning at the top into a rather long point. Such scales are located on the shoots in pairs, oppositely and closely adjacent to the surface of the stem. Both types of saxaul differ in one more way: the black shoots taste salty or sour-salty, while the white shoots are unpleasantly bitter.

White saxaul, like black saxaul, is of great economic importance in the desert regions of Central Asia, being a valuable fuel for the local population. The stock of firewood per 1 ha can reach several tons.

Both types of saxaul are also widely used for fixing shifting sands and landscaping. Finally, they also have a fodder value: camels and sheep feed on their young shoots.

In addition to trees and shrubs, in the sandy desert there are also various herbaceous plants. The development of many of them is timed to spring, when the desert is quite humid, but not very hot yet. When the soil dries out, the life of ephemeral annuals ends, they completely die, scattering their seeds. In ephemeroid perennials, only the above-ground organs die, while the underground part remains alive.

Of the ephemeroid grasses in the sandy desert, the most widespread is the swollen sedge, or ilak (Carex physodes). In early spring this plant forms rather dense, but very low thickets on the soil, creating a real green carpet under rarely standing shrubs and trees. Numerous brownish spots are clearly visible from a distance against a greenish background. Close up, you can see that a separate speck is a small bunch of reddish-brownish oval bags the size of a bean grain. All of them are gathered together at the top of the stem and stick out in different directions. The bags are filled with air, and at the bottom of each is a small nut, which is the fruit of a plant. Other sedges also have sacs, but they are many times smaller than the desert sedge in question (their size is usually no larger than a hemp seed). Strongly swollen, bubble-like sacs are the plant's adaptation to life among the sandy expanses. Falling to the ground, due to their lightness, they always remain on its surface, they are not covered by sand. We saw something similar in one of the bushes of the sandy desert - chingil.

The swollen sedge has narrow and relatively short leaves. fresh greens plants in spring time- an excellent fodder for cattle grazing in the desert. This sedge is a valuable fodder plant.

The underground organs of the sedge are long rhizomes, from which many thin, highly branched roots extend, which absorb water. The upper layer of sand is very densely permeated with a network of these roots. They usually do not go deeper than 10-15 cm.

Sedge swollen - characteristic plant immovable, fixed sands. It grows especially magnificently in depressions between sandy mounds, where the sand is most dense.

We have already said that the sandy desert, if it is little disturbed, has a fairly dense vegetation cover. The sand, held together by the roots of plants, remains motionless, not blown by the wind. Vegetation disturbances in the sandy desert have detrimental effects. Excessive grazing of livestock, mass cutting of saxaul lead to the destruction of the vegetation cover. Bare, unfastened sand under the influence of the wind begins to move, becomes mobile. The dunes are starting to move. In light winds, sand flows in characteristic streams on their exposed surface. During a hurricane, huge masses of sand rise into the air - sandstorms arise.

Moving sands are a terrible elemental force. There are many cases in history when flowering oases and entire cities in the desert were covered with sand.

What is the fate of loose sands, do they always remain mobile? Sooner or later, individual plants appear on the surface of barkhans, and over time their number increases, and a vegetation cover can form. If this happens, then the sands stop.

One of the first to settle on the bare sand is the interesting cereal Aristida, or Selin (Aristida karelinii). It is surprisingly adapted to life in these harsh conditions. Its long roots, similar to thick cords, extend far to the sides in a horizontal direction. The wind often blows sand off them, and they are exposed. But this does not cause much harm to the plant. The fact is that the roots of selin are well protected from drying out and mechanical damage. They are completely covered from the surface with a thick and durable cover of grains of sand - like firework sticks with a combustible composition. A tube-shaped cover is formed from mucus secreted by the roots and cementing grains of sand.

Celine also tolerates falling asleep well with sand. The tufts of grass may be almost completely covered, but nevertheless the celine does not die. The plant has new shoots and roots, it continues to live as if nothing had happened.

The danger of being covered up always haunts the plants of the sands, as well as the danger of exposing the roots. However, the inhabitants of the sandy desert have a variety of adaptations that allow them to survive in these conditions. One of them is the ability to quickly form new roots on stems partially covered with sand. Old root system, being too deep in the sand, it may die, but the newly formed young roots save the plant.

If sand covers trees and shrubs, they produce abundant growth from horizontal roots extending far away from the mother plant. The parent specimen itself, buried in sand, may die, but the daughter ones, formed from the roots, come to replace it. The plant seems to roam, moving from one place to another. Finally, the root system of desert trees and shrubs suffers little if it is partially exposed due to sand blowing. It is reliably protected by an integumentary fabric from loss of water. Sometimes you see that a tree stands with half-exposed roots, as if on props, but it still does not die, it remains alive.

Solonchak deserts have a significant distribution in the desert zone. They develop on flat low clay areas, devoid of noticeable hillocks and depressions.

Soils in this type of desert contain a lot of easily soluble salts that are harmful to plants, most often table salt, sodium sulfate and soda. Therefore, in saline deserts, only such representatives of the flora are found that are able to tolerate salinity (halophytes).

Saline deserts are very different from other types of deserts, primarily because the plants here never dry out. They always remain fresh, juicy - in spring, and in summer, and in autumn. Vegetation cover is usually quite dense, almost continuous. Its colors are very attractive and change throughout the year. In spring, the carpet of plants is bright green, by summer it becomes yellowish, then bright yellow. With the onset of autumn, the color changes to pink, then blood red, and finally purple.

Soleros; Sarsazan - part of the plant

In the vegetation cover of the salt marsh desert, succulents play the main role - succulent fleshy plants with strongly thickened stems or leaves. Almost all of them belong to the haze family. However, there are also plants with ordinary, unthickened aboveground organs the flora of the saline desert is very poor, there are few species. This usually happens in especially harsh conditions of existence. Sometimes on a large area (several hectares) you can count no more than a dozen species. Often one species dominates over a wide area.

Salicornia herbacea is one of the most characteristic plants of the salt marsh desert. This small herbaceous plant is a typical succulent: its stems are thick, juicy. There are absolutely no leaves. The plant has a peculiar appearance and slightly resembles some strange fleshy horsetail. The main stem of saltwort is almost always upright, side branches depart from it in pairs, which then branch weakly. Both the stem and branches consist of many individual segments of irregular cylindrical shape (each segment expands at the top). Saltwort shoots are juicy, rich in water. If you chew them, you feel that they taste salty. Developing on highly saline soil, the plant, together with the soil solution, absorbs a lot of salts, and they accumulate in its tissues.

Soleros is one of the most typical halophytes (salt lovers). It grows well in salt-rich soil where so many other plants cannot thrive. Saltwort is well adapted to such specific conditions. It is interesting that on soil that is not completely saline, this plant develops worse than on slightly saline soil. Its best growth was noted at 2 - 3% NaCl in the soil. If there are more salts, the plant develops worse. The limiting concentration is surprisingly high - 17% NaCl. Only under these conditions does the soleros die.

Like many other inhabitants of salt marshes, soleros develops very slowly. In spring, when a green carpet of grasses appears in other types of deserts, soleros barely begins to develop. It blooms in the hottest time - from June to September. The plant does not die until winter, remaining juicy and fresh all the time. Only its color changes - from green to bright red. However, even in summer, red tones already clearly appear.

Soleros belongs to the haze family. Its small flowers, located at the ends of the shoots, are almost entirely hidden in special cavities between the segments. Only stamens and short stigmas of pistils protrude outside.

Another characteristic plant of the saline desert is the knobby sarsazan (Halocnemum strobilaceum). This is a real semi-shrub. It grows in the form of a splayed-branched bush, the lower part of which is made up of lignified branches. The shoots of the current year are peculiar - thick, juicy, jointed. They are densely covered with spherical non-developing buds, similar to small cones (hence the specific name "knobby"). Young shoots, like those of soleros, are salty in taste. It should be noted that sarsazan has a lot in common with soleros: both plants are halophytes and succulents, both belong to the haze family, both often form almost pure thickets over a large area. However, sarsazan is usually a more or less large bush, spread out in the form of a pillow on the ground, and soleros is annual plant with a well-defined herbaceous main stem. Sarsazan, as a rule, is somewhat higher (reaches half a meter).

Saline deserts are usually found where groundwater is fairly close. Salinization of the soil layer occurs due to the fact that the water evaporating from the surface of the soil is replaced by more and more portions of water from below, from the ground. Even if groundwater contains few salts, then in this case, the constant movement of these substances into upper layer soils and their accumulation there sooner or later lead to salinization. After all, water evaporates all the time, but salts remain.

Saline deserts are connected mainly with the river terraces of the Syrdarya, Amudarya and some other rivers of the desert zone, or with depressions where atmospheric water flows. They do not occupy such large areas as other types of deserts and are most often found in the form of inclusions.

So we have considered Various types deserts, got acquainted with their features. Now we should say a little about the northern border of the desert zone, about the transition between steppes and deserts.

In the extreme north of the desert zone, there is a rather wide transitional strip between the steppe and the desert - the so-called semi-desert. It is considered the northernmost subzone of the desert zone. This territory is characterized by the joint growth of both plants of the southern steppe, especially feather grass and fescue, and representatives of the northern clay desert, i.e. semi-shrub wormwood and saltwort. The vegetation cover here has a pronounced patchy character, which is due to numerous micro-highs and micro-lows of the relief. In shallow saucer-shaped depressions, where the soil is better moistened and less saline, steppe plants. On flat low hillocks, where, on the contrary, it is especially dry and there are more salts in the soil, plants characteristic of the desert predominate.

It remains to say a little about economic use areas in the desert zone. Huge areas of deserts still serve as pastures for livestock. Animal husbandry is the leading branch of the national economy in these areas, so the importance of natural vegetation as a source of food is very high. From this point of view, sandy deserts are the most important, followed by clayey (wormwood and saltwort) and then ephemeral deserts. Sandy deserts as a pasture are especially valuable in that even in the driest years they provide sufficient fodder mass (plants develop here due to the horizon of condensation moisture in the soil).

The desert is the edge of the sun. There is a lot of warmth and sunshine here. However, for the successful cultivation of many agricultural plants, irrigation is necessary. In the oases of the desert zone, when irrigated, they successfully grow "white gold" - cotton. This most valuable culture is spreading wider and wider, occupies ever larger areas. In our desert regions, remarkable in their own way, ripen palatability melons are the best in the world. Excellent, very sweet grapes, apricots, peaches, pomegranates and many other fruits and various vegetables are grown here. The desert more and more submits to man, serves him. The national economic significance of desert vegetation, both natural and cultural, is very great.

Now that we have become familiar with all the vegetation zones Soviet Union, starting from the tundra and ending with the desert, it is advisable to dwell on some general points regarding vegetation zones.

Let's go back to the tundra. As we have already said, the vegetation cover here is very low, mosses, lichens and small shrubs (dwarf willows and others) play an important role. All this is due to the fact that there is very little heat in the tundra, although there is enough moisture and light for plants. The fact that the summer is too short and cool also plays a role. Consequently, the main determining factor in the life of the plant world of the tundra is the lack of heat.

In the forest zone, the situation is somewhat different. -Northern forests adjacent to the tundra zone also experience some lack of heat. The trees here are stunted, they do not form a dense forest. But further south, the heat becomes quite enough and the forest acquires its typical appearance: it is quite high and dense. In the very south of the forest zone, a new factor begins to play a role in plant life - humidity. There is a noticeable lack of moisture here, and coniferous trees that are demanding on moisture can no longer grow in the forest. Dominance passes to broad-leaved trees, which are less demanding on moisture. They form deciduous forests. Therefore, in the north of the forest zone, the determining factor is heat, and in the south, moisture.

Further south, moisture becomes less and less. The forest gives way first to the forest-steppe, and then to the steppe. In the steppe zone, the lack of moisture does not allow even the most unpretentious forest trees to grow on watershed spaces. The increase in aridity of the climate in the direction to the south also affects the steppe vegetation. The herbage of the steppe is becoming lower and less frequent, the role of feather grasses is increasing, more and more more plants, which "run away" from drought (ephemers and ephemeroids). In the forest-steppe and steppe, the determining factor, as in the south of the forest zone, is humidity and water supply conditions.

To an even greater extent, this applies to the desert zone. Here the lack of moisture is especially acute. Plants experience "water starvation" throughout almost the entire summer. And summer in the desert is very long and extremely hot. In the loamy watershed areas of deserts, plants are forced to be content with the small amount of moisture that comes from the atmosphere. In this regard, the vegetation cover of the desert is sparse, open, the plants are more or less distant from each other, and the bare surface of the soil is visible everywhere. Only on salt marshes, which are located in closed depressions, are plants better supplied with moisture, but their living conditions here are extremely unfavorable due to the very high salinity of the soil.

All of the above can be summarized in the following way. In the tundra and in the north of the forest zone, the determining factor in plant life is the lack of heat. Starting from the southern part of the forest zone and further up to the deserts, the most important factor is the lack of moisture. Moreover, in the direction to the south, it is more and more intensified.

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How the desert blooms

One tenth square meter in the soil of the desert are many thousands of plant seeds, which, after the rainy season, germinate with astonishing rapidity. In less than two weeks, some have time to sprout, bloom and produce seeds, quickly turning the bare earth into a colorful and fragrant garden.

Seeds usually do not germinate on first contact with moisture. Most need to swell first. This is due to a special substance that inhibits germination. Only after the water dissolves and washes it off, the seeds can sprout. This mechanism prevents the emergence of sprouts before the soil is sufficiently moistened. In the desert, seeds often germinate with the onset of the second rather than the first rainy season. There are also those that lie in the soil for several years in anticipation of suitable conditions.

"Living Stones"

Many animals escape the hot desert sun by burrowing into the ground. Surprisingly, some plants in South West Africa do basically the same thing. A number of representatives of the Aizoon family, such as lithops, or, as these plants are called, "living stones", are completely buried in the sand, and only parts of the leaves open to sunlight - leaf windows - look out to the surface. Others are so similar to pebbles or small stones scattered across the desert that they can only be detected when an unusually large flower is born.

"Living stones" are able to survive where the annual rainfall is just above 10 mm, since most of the necessary moisture is brought to them by fog coming from the sea. The conditions in which these plants live make them carefully conserve moisture. Burrowing into the ground, they hide from the sun and reduce evaporation.

Even without their feathery flowers, South African "living stones" would be amazing plants. Deserts are not always bare. After the winter rains, the ground at the foot of these mountains in California is covered with bright colors.

Trees in the desert

Ordinary broad-leaved trees do not tolerate desert conditions well, because with their spreading crowns, too much water evaporates from the leaves. Among the trees most characteristic of arid regions are many species of acacia, whose crowns look like umbrellas. When water becomes scarce, their leaves curl up and droop, and then fall off. New leaves appear after rains.

Many tree-like plants of the desert look quite bizarre. African baobabs have exorbitantly swollen trunks made up of loose wood. From the thick water-storing trunks of the idria tree growing in Baja California, thin branches covered with thorns extend in all directions, and leaves appear on them only when there is enough moisture. Belonging to the same family, brilliant fouquieria is dry, woody stems without leaves for most of the year, but in the rainy season, the plant glows with scarlet flowers.

Why don't plants wither in the sun?

In the desert, plants conserve the moisture that they manage to get. Wax coating on leaves and stems helps to reduce water loss. Others are covered with dense felt of silvery hairs that reflect the sun's rays. When water becomes scarce, some plants shed their leaves. Many have tiny openings, the stomata through which gas exchange occurs, deeply embedded in the leaf tissue, which minimizes moisture loss due to evaporation.

agave plant

For 10, 20 and even 50 (but not 100) years, the American agave, or agave, is just a rosette of leaves. almost never rise above the ground. Although "only" is probably not the right expression to describe the agave that grows in the deserts of Mexico and the southwestern United States: its leaves, armed with sharp thorns, reach 3 m in length.

A mature agave is no longer just a rosette of leaves, a stem with yellow flowers rises from it by 6 m or even more. After pollination of the flowers, fruits are formed that fall to the ground and give rise to new plants. And the parent plant dies after its first and only flowering.

Indoor plants from the desert

Desert plants have become popular houseplants because they are hardy and because many of them look quite unusual. The peanut cactus, hooked ferrocactus, or cephalocereus (old man cactus) are nothing like the green-leaved plants we are used to. In addition to a variety of cacti, desert plants such as some species of spurge, stonecrop, aloe and "living stones" are grown indoors. All of them store water in their fleshy leaves or stems.

But even these hardy desert dwellers do not always survive in room conditions. They grow best when given an environment that is as close to their natural habitat as possible, which often means high temperatures and plenty of light. Although excess moisture will not kill them, the soil must be loose so that the water does not stagnate. Most of the water these plants require during the period rapid growth- an attentive observer will easily notice its onset. Plants originating in the Northern Hemisphere typically grow vigorously in the spring and then enter a dormant period when they only need to be watered once every few weeks.

Deserts are such natural areas that are characterized by high temperatures, lack of humidity, almost complete absence of precipitation and a strong drop in temperature at night. Deserts are not associated with fertile soils where fruits and vegetables, trees and flowers grow. However, the flora of these natural areas unique and varied. It will be discussed in this article.

Fitness

Botanists still do not have reliable information about how desert plants have changed. According to one version, some adaptive functions were acquired by them millions of years ago due to changes in environment. Therefore, representatives of the flora were forced to adapt to adverse conditions. So, during the rain, the processes of growth and flowering are activated. So, what are the characteristics of desert plants?

• The root system is very deep, it is highly developed. The roots penetrate the soil to a great depth in search of groundwater. By absorbing them, they transfer moisture upper parts plants. Those representatives of the flora that have this feature are called phreatophytes.
• The roots of some plants, on the contrary, grow horizontally to the surface of the earth. This allows them to absorb as much as possible more water during periods of rain. Those species that combine both of the above features are best adapted to life in desert regions.
• For representatives of the flora growing in deserts, it is very important to accumulate a large amount of water. Absolutely all parts of plants, especially stems, help them in this. These organs not only perform a storage function, but are also the site of photosynthesis reactions. Simply put, stems can replace leaves. To keep moisture longer in the body of the plant, the stems are covered with a thick layer of wax. It also protects them from the heat and the scorching sun.
• The leaves of desert cultures are small, they contain wax. They also store water. Not all plants have leaves. In cacti, for example, they are represented by prickly thorns. This prevents the waste of moisture.

So, there are properties created by evolution that allow representatives of the flora to exist in the desert zone. What plants can be found there? Below is a description of the most popular of them.

Cleistocactus Strauss

This plant, often referred to as a woolen torch. It has to do with his appearance. Cleistocactus can grow up to 3 meters. Its stems grow vertically upwards, have a gray-green color. The ribs of the culture are dotted with medium-sized white areoles, located at a short distance from each other. It is about 5 mm. Thanks to this, the plant seems woolen, which is why it got its "folk" name.

Flowering occurs at the end of summer. At this time, dark red flowers are formed, which have a cylindrical shape. Cleistocactus can be grown at low temperatures that reach -10 ° C. The homeland of culture is the territory of Argentina and Bolivia.

Wollemia

This desert plant, described in this article, is one of the rarest conifers in the world (discovered in 1994). It can only be found on the territory of such a mainland as Australia. Wollemia is considered one of the ancient species plants. Most likely, the history of the tree began at least 200 million years ago, and today it belongs to the relic.

The plant looks mysterious and unusual. So its trunk is shaped like an ascending chain. On each tree, female and male cones are formed. Wollemia perfectly adapts to adverse environmental conditions. It tolerates fairly low temperatures, dropping to -12 ° C.

desert iron tree

This plant can be found in North America, namely, in height it can reach 10 m. The diameter of the trunk, on average, is about 60 cm, but in some places it can expand or narrow. The plant can be either a bush or a tree. Its bark changes color over time. young tree has a smooth shiny skin gray color, and subsequently it becomes fibrous.

Despite the fact that this plant is considered an evergreen, at low (colder than 2 ° C) temperatures, it loses its foliage. With a long absence of precipitation, the leaves also fall off. The flowering period begins in late April - May and ends in June. At this time, pale pink, purple, purple-red or white flowers appear. The density of a desert tree is very high, it exceeds that of water, which is why the plant sinks. It is solid and heavy. Since the wood is strong and fibrous, it is used to make knife handles.

Euphorbia obese

Because of its unusual shape, it is often called the "baseball" plant. This representative of the flora is common in South Africa, namely in the Karoo desert.

Euphorbia has a small size. So, its diameter is about 6 - 15 cm and depends on age. The shape of this typical desert plant is spherical. However, it becomes cylindrical over time. In most cases, Euphorbia obese has 8 facets. They have tiny bumps on them. The flowers of this representative of the flora are commonly called cyathias. This plant can store water for a long period of time.

Cylindropuntia

These desert plants are often referred to as "cholla". They can be found in the United States, namely in the southwestern regions and in the Sonoran Desert. This representative of the flora is a perennial. Its entire surface is covered with sharp silver needles. Their size is 2.5 cm. Due to the fact that the cylindric densely covers all free space, the plant can be confused with a small dwarf forest. A large amount of water accumulates in a thick trunk, which allows the culture not to suffer much from the hot desert climate. The flowering period begins in February and ends in May. At this time, greenish flowers form on the plant.

carnegia

What other desert plants exist? These include This representative of the flora can reach truly gigantic sizes. So its height is about 15 m. This plant grows in the United States, in the state of Arizona, in the Sonoran Desert.

The flowering period of Carnegia is in the spring. An interesting fact is that the cactus flower is national symbol state of Arizona. Thanks to the presence of thick spikes, the culture saves precious water. Carnegia is a long-liver. Her age can reach 75 - 150 years.

african hydnora

One of the strangest desert plants common in Africa is due to its unusual and very extravagant appearance, not all botanists classify this organism as a representative of the flora. Hydnora has no leaves. The brown trunk can merge with the surrounding space. This plant becomes most noticeable during the flowering period. At this time, spherical flowers form on the stem. Outside they are painted Brown color, and inside - in orange. In order for insects to pollinate the plant, hydnora emits a pungent odor. Thus, she continues her race.

Baobab

Known to many, it belongs to the genus Adansonia. Its homeland is the African continent. This tree is most often found in the southern region of the Sahara desert. Most of the local landscape is represented by the baobab. By the presence of this plant, you can determine whether there are nearby sources of fresh water in the desert. Plants can adapt to unfavorable conditions different ways. So, the growth rate of the baobab directly depends on the availability and amount of groundwater or precipitation, so the trees choose the wettest places for their life.

This plant is long-lived. The maximum age ever reached by representatives of this species is 1500 years. Baobab is not only a guide through the desert, but it can also save lives. The fact is that not far from this tree you can find food and water. Some parts of the plant can be used as medicines or sheltered under a spreading crown from the heat. People from all over the world compose legends about this representative of the flora. It attracts many tourists. Previously, the names of scientists and travelers were carved on it, but now the tree trunks are defaced with graffiti and other drawings.

Saxaul

A desert plant may look like a shrub or a low tree. It can be found on the territory of such states as Kazakhstan, Turkmenistan, Uzbekistan, Afghanistan, Iran and China. Often, several trees grow near each other at once. In this case, they form a kind of forest.

Saxaul is a desert plant that can reach a height of 5 - 8 m. The trunk of this representative of the flora is curved, but its surface is very smooth. The diameter varies within one meter. Massive, bright green crown looks very noticeable. The leaves are represented by small scales. With the participation of green shoots, the process of photosynthesis takes place. When strong gusts of wind act on the tree, the branches begin to flutter and cascade down. During flowering, pale pink or crimson flowers appear on them. In appearance, one might think that saxaul is a very fragile plant that is not able to withstand bad weather. However, this is not so, because it has a very powerful root system.

These plants are specially adapted to live in hot and dry habitats. The cactus has a thick, waxy outer layer to keep water from evaporating. Sagebrush and desert grasses need very little water to survive. Plants of deserts and semi-deserts have adapted to protect themselves from animals by growing sharp needles and thorns.

Most desert and semi-desert plants bloom in spring, reproducing flowers until the onset of hot summer. In the years of wet winter and spring, surprisingly many spring flowers can produce semi-desert and desert plants. In desert canyons, on rocky mountains get along pine trees, growing junipers and sage Shrublands. 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 mystogamous plants - spore fungi, algae, ferns, 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 important nutrient for plants. Cryptogamous plants and lichens grow very slowly.

Many people destroy desert plants without even knowing their important role. Many people see the desert and think that this is not such a significant life. Desert plants have developed various ways to reduce water loss and get as much water as possible.

Some plants have long roots to get water by penetrating deep into the soil, or branched roots to collect water over a large area. Due to the thick waxy layer on the stems and leaves, they retain water, and the tissues are protected from strong sunlight. Some plants have needle-thorns instead of leaves to reduce water loss from the trunk. Many desert and semi-desert plants are succulents, and they store water in their swollen stems and leaves.

Some desert plants are "drought avoiders". They exist like seeds and grow when it's raining. Their flowers quickly produce seeds and then die. There are "drought resistant" plants - perennials that have the ability to store water or minimize water use.

Some plants of deserts and semi-deserts:

Mormon Tea, Mormon tea. This medium sized shrub grows up to 4 meters in height. Numerous green, jointed, glabrous branches with conspicuous nodes. It actually has small, scale-like leaves and small flowers of male and female cones that bloom from February to April.

Fairy Duster, Fairy flower. The Fairy Duster is a low, densely branched shrub. She is a member of the Fabaceae family. , which includes acacias and mimosas. Without thorns, this perennial shrub provides food for many desert animals, birds and insects.

Forget-me-not family (Boraginaceae), genus Plagiobothrys is also called Popcorn flower. Spiral stems and small open white flowers cluster at the top of the spool, looking like popcorn. There are over 40 species of this plant. Cryptantha augustifolia, in the same family, has narrow leaves.

Desert Botanical Garden can give the most complete picture of the plants of deserts and semi-deserts.

Speaking of the desert, first of all, we imagine sandy expanses where there is no water, no animals, no plants. But such a landscape is not universal, and nature in the desert is very diverse. Some species of birds, mammals, herbivores, insects and reptiles are found in deserts. So, they have something to eat in the desert.

Despite the hot and dry climate, strong winds and sandstorms, lack of precipitation, representatives of the animal world are able to survive in such conditions. Some species of flora have also adapted to these conditions.

What are the conditions for plant life in deserts?

The local flora has adaptations thanks to which it survives:

• spines;
• powerful root system;
• fleshy leaves;
• small height.

These adaptations allow plants to gain a foothold in the soil. Long roots reach groundwater and the leaves retain moisture for a long time. Since shrubs and trees grow from each other at a certain distance, they can absorb moisture to the maximum in their radius. Only under such conditions does the flora exist in the desert.

What types of flora grow in deserts?

The flora of the desert is very unusual. Most common in this area different kinds cacti. They are different sizes and forms, but in general it is a massive body and spines. Some species live for hundreds of years. Aloe is also found here, has thorns and fleshy leaves.

Baobabs also grow in deserts. These are trees that have massive trunks and long roots, so they feed on underground water sources. Quite often in the deserts there are spherical tumbleweed bushes. The jojoba tree also grows here, from the fruits of which valuable oil is obtained.

In the desert, there are numerous small plants that bloom when it rains. During this period, the desert is dressed in colorful flowers. Among the small plants come across camel thorns and.

Among other plants in the deserts, lithops and elm, creosote bush and comb, cereus, slipway grow. Wormwood, sedge, bluegrass and other herbaceous plants, trees and shrubs grow in oases.

All desert plants have adapted to harsh climatic conditions. But, despite the thorns, thorns, small size, the desert flora is magnificent and amazing. When it rains, the plants even bloom. Anyone who has seen the blooming desert with their own eyes will never forget this magnificent miracle of nature.

Informative video about plants in the desert

How do plants adapt to life in the desert?

A variety of plants in the desert is possible because they have special adaptations and differ significantly from the vegetation of forests and steppes. If the plants of these natural zones have powerful stems and branches, then desert plants have very thin stems in which moisture accumulates. Leaves and branches change into thorns and shoots. Some plants have scales instead of leaves, for example, y. Although desert plants have small size, they have a long and powerful root system, which allows you to gain a foothold in sandy ground. On average, the length of the roots reaches 5-10 meters, and in some species even more. This allows the roots to reach the groundwater that the plants feed on. So that every shrub, tree or perennial received enough moisture, they grow on a certain plant from each other.

So, the most adapted to life in the desert different types flora. Since cacti live for several decades, and some individuals grow for more than 100 years. Different shapes and shades have ephemera, which bloom especially vividly during rain. In some places you can find original forests of saxaul. They can grow as trees or shrubs that reach an average of 5 meters, but can be higher. Very large shrubs are found in the desert. It can be sand acacias. They have thin trunks and small leaves with small purple flowers. It has a yellow flowering creosote bush. It is adapted to prolonged drought and harsh climatic conditions, repels animals, highlighting bad smell. Various succulents grow in the desert, for example, lithops. It is worth emphasizing that any desert in the world can surprise you with the diversity and beauty of the flora.