T.V. Lukarevskaya

When we enter the forest on a summer day, we immediately notice fluttering butterflies, singing birds, jumping frogs, we rejoice at a running hedgehog, meeting a hare. One gets the impression that it is these well-visible animals that form the basis of our fauna. In fact, the animals that are easy to see in the forest are only an insignificant part of it.

The basis of the population of our forests, meadows, fields is made up of soil animals. The soil, at first glance so lifeless and unsightly, turns out, upon close examination, literally stuffed with life. If you look closely, you will see extraordinary pictures.

Some inhabitants of the soil are not difficult to see. It - earthworms, centipedes, insect larvae, small mites, wingless insects. Others can be viewed with a microscope. In the thinnest films of water that envelop the soil particles, rotifers, flagellates scurry, amoebas crawl, roundworms wriggle. How many real toilers are here, indistinguishable to the naked eye, but doing, nevertheless, a titanic job! All these invisible creatures keep our common home - the Earth - clean. Moreover, they also warn of the danger that threatens this house when people behave unreasonably in relation to nature.

In the soil middle band In Russia, per 1 m2, you can find up to 1 thousand species of soil inhabitants that are very different in number: up to 1 million ticks and springtails, hundreds of millipedes, insect larvae, earthworms, about 50 million roundworms, while the number of protozoa is even difficult to estimate.

This whole world, living according to its own laws, ensures the processing of dead plant residues, cleaning the soil from them, maintaining a water-resistant structure. Soil animals constantly plow the soil, moving particles upward from the lower layers.

In all terrestrial ecosystems the vast majority of invertebrates (both in the number of species and in the number of individuals) are inhabitants of the soil or are closely related to the soil at a certain period of their life cycle... According to the calculations of Boucle (1923), the number of insect species associated with the soil is 95–98%.

Centipede Earthworm

There are no animals equal to nematodes in their ability to adapt to living conditions. In this respect, they can only be compared with bacteria and the simplest unicellular organisms. This universal adaptability is largely due to the development of a dense outer cuticle in nematodes, which increases their vitality. In addition, the body shape and movement patterns of nematodes were found to be suitable for life in various environments.

Nematodes take part in the mechanical destruction of plant tissues: they are "drilled" into dead tissue and, with the help of secreted enzymes, destroy cell walls, opening the way for bacteria and fungi to enter.

In our country, losses in the yield of vegetables, grain and industrial crops due to damage from roundworms sometimes reach 70%.

Nematode

The formation of tumors - galls - on the roots of the host plant is caused by another pest - the southern rootworm nematode (Meloidogyne incognita). Greatest harm it brings vegetable growing in the southern regions, where it is found in the open field. In the north, it is found only in greenhouses, damaging mainly cucumbers and tomatoes. The main harm is done by females, while males, having completed development, go into the soil and do not feed.

Soil nematodes have a bad reputation: they are seen primarily as pests of cultivated plants. Nematodes destroy the roots of potatoes, onions, rice, cotton, sugarcane, sugar beet, ornamental and other plants. Zoologists are developing measures to combat them in the fields and in greenhouses. A great contribution to the study of this group of animals was made by the famous evolutionary biologist A.A. Paramonov.

Nematodes have long attracted the attention of evolutionists. They are not only extremely diverse, but also remarkably resistant to physical and chemical factors. Wherever they begin to study these worms, new species unknown to science are found everywhere. In this regard, nematodes seriously claim the second - after insects - place in the animal world: experts believe that there are at least 500 thousand species, but there is reason to believe that the true number of nematode species is much higher.

how animal habitat soil very different from water and air. The soil is a loose thin surface layer of land in contact with the air. Despite its insignificant thickness, this shell of the Earth plays a critical role in the spread of life. The soil is not just a solid, like most rocks of the lithosphere, but a complex three-phase system in which solid particles are surrounded by air and water. It is permeated with cavities filled with a mixture of gases and aqueous solutions, and therefore extremely diverse conditions are formed in it, favorable for the life of many micro- and macroorganisms. In the soil, temperature fluctuations are smoothed out compared to the surface layer of air, and the presence of groundwater and the penetration of precipitation create moisture reserves and provide a moisture regime intermediate between the aquatic and terrestrial environment. The soil concentrates reserves of organic and mineral substances supplied by dying vegetation and animal carcasses. It all defines greater saturation of the soil with life.

Every animal to live need to breathe... Conditions for breathing in soil are different than in water or air. Soil contains solids, water and air. Solid particles in the form of small lumps occupy a little more than half of the soil volume; the rest of the volume is accounted for by the gaps - pores that can be filled with air (in dry soil) or water (in soil saturated with moisture).

Moisture in the soil present in various states:

  • bound (hygroscopic and film) is firmly held by the surface of soil particles;
  • capillary occupies small pores and can move along them in different directions;
  • gravity fills larger voids and slowly seeps down under the influence of gravity;
  • vaporous contained in soil air.

Composition soil air changeable. With depth in it, the oxygen content drops sharply and the concentration of carbon dioxide increases. Due to the presence of decomposing organic matter in the soil, the soil air can contain a high concentration of toxic gases such as ammonia, hydrogen sulfide, methane, etc. When the soil is flooded or intensive rotting of plant residues, completely anaerobic conditions can occur in places.

Temperature fluctuations cutting only on the soil surface. Here they can be even stronger than in the surface air. However, with each centimeter deeper, the daily and seasonal temperature changes become less and less and at a depth of 1-1.5 m are practically not traced.

All these features lead to the fact that, despite the great heterogeneity of ecological conditions in the soil, it acts as fairly stable environment, especially for motile organisms. It is clear that animals can move relatively quickly in the soil only in natural voids, cracks, or previously dug passages. If there is nothing of this on the way, then the animal can advance only by breaking through the passage and shoveling the earth back, or by swallowing the earth and letting it pass through the intestines.

Inhabitants of the soil. The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment. For microorganisms, the huge total surface of soil particles is of particular importance, since the vast majority of the microbial population is adsorbed on them. Due to this structure of the soil, numerous animals that breathe through the skin... Moreover, hundreds of species of real freshwater animalsinhabiting rivers, ponds and swamps. True, these are all microscopic creatures - lower worms and unicellular protozoa. They move, float in a film of water covering soil particles. If the soil dries up, these animals secrete a protective shell and, as it were, fall asleep, fall into a state of suspended animation.

Among soil animals, there are also predators and those that feed on parts of living plantsmainly by roots. There is in the soil, and consumers of decomposing plant and animal residues; it is possible that bacteria play a significant role in their nutrition. "Peaceful" moles eat a huge amount of earthworms, snails and insect larvae, they even attack frogs, lizards and mice. Predators are found among almost all groups of invertebrates living in the soil. Large ciliates feed not only on bacteria, but also on the simplest animals, such as flagellates. Predators include spiders and hay makers close to them.

Soil animals find their food either in the soil itself or on its surface. The vital functions of many of them are very useful. Earthworms are especially helpful. They drag a huge amount of plant residues into their burrows, which promotes the formation of humus and returns to the soil the substances extracted from it by plant roots.

Not only earthworms "work" in the soil, but also their closest relatives:

  • whitish annelid worms (enchitreids, or pot worms),
  • some types of microscopic roundworms (nematodes),
  • small mites,
  • various insects,
  • wood lice,
  • centipedes,
  • snails.

The purely mechanical work of many animals living in it affects the soil. They make tunnels, mix and loosen the soil, and dig holes. These are moles, marmots, ground squirrels, jerboas, field and forest mice, hamsters, voles, mole rats. The relatively large passages of some of these animals go 1-4 m deep. In some places, for example, in the steppe zone, a large number of dung beetles, beetles, crickets, tarantulas, ants, and termites in the tropics dig holes and burrows in the soil.

In addition to the permanent inhabitants of the soil, among large animals there is a great environmental group burrow dwellers (gophers, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but multiply, hibernate, rest, and escape danger in the soil. A number of other animals use their burrows, finding a favorable microclimate in them and shelter from enemies. Norniks have structural features characteristic of terrestrial animals, but have a number of adaptations associated with a burrowing way of life. For example, badgers have long claws and strong muscles on the forelimbs, a narrow head, and small auricles. In rabbits, in comparison with hares that do not burrow holes, the ears and hind legs are noticeably shortened, the skull is stronger, the bones and muscles of the forearms are more developed, etc.

In the course of evolution, the inhabitants of the soil have developed adaptation to appropriate living conditions:

  • features of the shape and structure of the body,
  • physiological processes,
  • reproduction and development,
  • the ability to endure adverse conditions, behavior.

Earthworms, nematodes, most millipedes, and the larvae of many beetles and flies have a highly elongated flexible body that makes it easy to move through winding narrow passages and cracks in the soil. Bristles in earthworms and other annelids, hairs and claws in arthropods allow them to significantly accelerate their movements in the soil and hold firmly in burrows, clinging to the walls of the passages. How slowly the worm crawls along the surface of the earth and with what speed, in essence, instantly, it hides in its hole. While laying new passages, some soil animals, for example, worms, alternately stretch and contract the body. At the same time, cavity fluid is periodically pumped into the front end of the animal. It swells strongly and pushes soil particles apart. Other animals, such as moles, clear their way by digging the ground with their front paws, which have turned into special digging organs.

The color of animals constantly living in the soil is usually pale - grayish, yellowish, whitish. Their eyes, as a rule, are poorly developed or completely absent. But the organs of smell and touch have developed very subtly.

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Inhabitants of the soil

Any garden, even the smallest, is not only trees, shrubs, vines, flowers and herbs that we have planted or sown. Whether we like it or not, other tenants will surely appear in it, settling in, as they say, without prior arrangement, and guests, very numerous, dropping in for just a few minutes or staying for a long time. In addition, even before the bookmark, it already had its own world, which had developed long ago. Crawling, jumping, flying, in a word, living his tense, difficult life, he is extremely rich and diverse. Let's take a closer look at him. And let's start our acquaintance with the inhabitants of the soil.

Soil: breathable and silent.

Soil is not just earth, mechanical mass, a mixture of small and large particles, mineral and organic, as it is sometimes imagined, no, it is all inhabited, assimilated by various organisms that live and develop. In all directions and to a considerable depth, the roots of trees, shrubs, flowers, grasses penetrate it. Their excretions and residues after decay have a very significant effect not only on the physical and chemical properties of soil aggregates, but also on the biological activity of the soil. They affect it comprehensively: they promote the penetration of air into the deep layers, cause shifts in the equilibrium of an aqueous solution, promote the decomposition of minerals, and provide the microworld with organic nutrition.

Much depends on the amount and composition of plant root exudates, since they determine the development of microorganisms in the root zone, as well as the activity of biochemical processes here. The roots themselves serve as food for many inhabitants of the soil - ticks and nematodes, fungi grow on them, forming mycorrhiza, and bacteria that form nodules develop here.

There are millions of them in a gram.

Often on the soil surface, especially in shaded areas, under trees and bushes, it is easy to notice green or even bluish-green, like velvet, surfaces or pads. To the touch from below, they are often hard, like crusts, sometimes thin and delicate, like films, or they lie like a felt coating on a damp surface. This phenomenon is called soil bloom. It is caused by algae. It is clearly noticeable in spring, when there is a lot of moisture, the soil is not yet covered with plants, but it is already warm and sunny. Then, hundreds of millions of green algae cells can develop on one square meter, and their biomass in this area reaches 100 grams or more. In summer, they actively grow along the edges of ridges, in aisles, under trees and bushes. They also inhabit tree trunks, crevices and depressions of the bark on them, live on fallen leaves and under them. Their number varies from 5 thousand to 1.5 million in each gram of soil. In sod-podzolic, for example, their biomass in a layer of 10 centimeters usually ranges from 40 to 300 kilograms per hectare.

Along with other plants, algae form a lot of organic matter, thereby contributing to the accumulation of humus in the soil, increasing its fertility.

They carry out photosynthesis and release oxygen in environment and cyanobacteria. Some of them form on the surface of the soil rather large, several centimeters, dark olive-green mucous-cartilaginous colonies, consisting of numerous filaments located inside the mucus. Sometimes such colonies cover the land almost entirely. Others form blurry films of a purple hue on it. Most often they can be found in contaminated areas. They are pure green in color, do not form any crusts or films, but populate the topsoil very densely, sometimes giving it a greenish tint.

The representatives of mushrooms are also innumerable in the garden. They are sometimes the cause of many diseases of horticultural crops and often cause considerable damage to the harvest of fruits and berries. Most of the fungi live in the soil, where their mycelium (mycelium) often reaches a total length of 1000 meters per gram. Mushrooms decompose organic matter and synthesize hydrolytic enzymes, which allows them to assimilate complex substances such as pectin, cellulose and even lignin. In a day, they are able to decompose organic matter three to seven times more than they themselves can assimilate. And in the soil, their biomass often exceeds the bacterial one.

Marsupials cause such dangerous diseases as powdery mildew and apple or pear scab. On old, dying parts of trees, stumps and roots, tars and cap mushrooms grow. Among them, in the garden, mushrooms are most often found developing on a dung or humus substrate, as well as mushrooms, toadstools and a number of inedible lamellar mushrooms.

One cannot but mention unicellular mushrooms - different types yeast. They develop well in the soil environment at low temperatures, close to zero, and almost stop developing at 20 degrees Celsius. There are many yeast fungi on the leaves, inside them, in the nectar of flowers, in the sap of trees, on fruits and berries.

Such a special group of lower plants as lichens also has its representatives in the garden. Their body is made up of two different organisms - fungus and algae. Free-living lichen fungi are not found. They grow slowly, especially crustal ones - they grow from 1 to 8 millimeters per year. Most often they can be seen on the bark of trees, especially old ones, or directly on the soil, where they form crusts and bushes. Resistant to direct and bright sunlight and drying out, they are able to absorb water directly from the atmosphere, even at low humidity. Lichens secrete complex organic acids, the so-called lichen, which have antibiotic properties. Studies have shown that lichens are home to many yeasts and other fungi, spores and bacteria.

Bacteria are involved in almost all biochemical processes in the soil. They make up the bulk of the microbiological population of the soil - their number reaches hundreds of millions and even billions in one gram - and largely determine its biological activity.

Inhabitants of the dark halls.

Numerous soil animals have a very significant effect on the composition of the soil, its structure and fertility in general. Their number in the middle lane is greatest in the uppermost part of the soil horizon, and decreases sharply at a depth of half a meter or more. In the steppe and forest-steppe zones, on chernozems, they penetrate twice and three times deeper. If there is enough water in the soil pores, unicellular animals actively develop here - flagellates, ciliates, sarcodes. Their number is large - up to several hundred thousand in one gram of soil, and their biological mass reaches 40 grams per square meter.

Life in soil, which has the finest capillaries, has led to the fact that the simplest animals here are 5-10 times smaller than those of similar creatures living in rivers, lakes, ponds. In some of them, the cells have become flat, the usual outgrowths and spines are absent. Among rhizopods there are naked and conchial amoebas, they do not have a constant body shape, but rather overflow from place to place, flowing around their victims - plant cells that they feed on - and thus include them in their protoplasm. Ciliates - typical inhabitants of water bodies - in the soil are much less than flagellates and amoebas, but scientists still found representatives of 43 genera!

But worms play an especially important role in the life of the soil, in enriching it with the organic matter necessary for plants. They are divided into two groups - lower and higher. The former include rotifers and nematodes - the simplest of the multicellular living creatures.

Rotifers have circular rows of cilia on the front of the body, thanks to which they rotate and move. They usually live in ponds, lakes, rivers, but are also found in the soil - they float in water capillaries and films. They feed on bacteria and unicellular algae.

Among the higher worms, enchitreids play a noticeable role in the life of the soil, measuring from 3 to 45 millimeters in length and 0.2-0.8 millimeters thick. The smallest ones move through the soil along its natural pores and channels, while others make their way, eating it. Enchitreid biomass in good garden plots often reaches 5 grams per square meter. Most of them are in the upper layer of the soil, since their main food is dying roots. Sometimes they gnaw out areas damaged by nematodes. They are also abundant where there is moist humus. In this they differ from earthworms, of which there are also about 200 species.

Snails. Lives in the garden and another group of animals - snails. Although they, like other molluscs, for the most part are typical inhabitants of water bodies, the so-called pulmonary snails have adapted to terrestrial image life. Due to the presence of a shell, they relatively easily tolerate unfavorable conditions - cold, drought, heat, and slugs that do not have a shell, in the heat and cold, hide under mulch, leaf litter or go deeper into the soil. Among the pulmonary snails there are herbivores and predators, some cause significant damage to plants, for example, grape.

Slugs feed on freshly fallen leaves, grass, and dying tissues, but they can also damage living plants. The so-called field slug damages the seedlings of vegetable, garden, field and forest crops... Some feed on algae, lichens, mushrooms, that is, they perform the functions of orderlies and are harmless to the garden.

There are still many tiny creatures in the soil that affect the life of fruit and berry crops. Some of them are visible to the naked eye and are called tardigrades, or cubs. Their body is short, in a kind of shell (cuticle). Four pairs of short legs, like muscular tubercles with claws. In the mouth, the stylet is a kind of knife with which they pierce the tissues of plants and suck out the contents of living cells. In the soil with leaf litter, there are many springtails and armored mites, woodlice, millipedes, insect larvae. Woodlice, like earthworms, make small passages in the soil, improve its porosity, aeration, and process the primary plant material into humus. Centipedes are terrestrial animals, but they lead a secretive lifestyle, hiding in soil burrows, under mulch or leaves. Among them there are very small ones, 1.5-2 millimeters, and quite large ones, 10-15 centimeters, for example geophiles. The body of a centipede consists of many segments, each of which has two limbs. These include kivsyaki, which are very common in the garden.

Insect larvae. The soil of the garden is also densely populated by various representatives of the countless insect family. Many always, and others only at a certain stage live in the soil, for example, the larvae of the ground beetle, click beetle, beetle, May beetle, dung beetle. Some larvae behave like earthworms, others damage healthy plant roots and cause significant damage to them, especially during mass reproduction. So, for pupation, more than a hundred caterpillars of the meadow moth go into the soil on each square meter. Wireworms - long, yellowish, hard to the touch larvae of click beetles, legless larvae of weevils have a noticeable effect on the condition of some garden and vegetable garden crops. Larvae of some butterflies and sawfly beetles also live in the soil. photosynthesis cyanobacteria soil

Medvedka. Well adapted to constant life in soil, especially in structural, high-moisture, black earth, and such an insect as the bear. She is able to quickly make rather wide, long strokes at the very surface of the soil and cause considerable damage to the crop, especially in areas with loose, humus and sufficiently moist soil. She and her larvae feed on the roots and stems of plants: they eat out tubers, corms, roots and seeds. Strawberries, strawberries, and vegetable crops suffer the most from them.

Adult insects and their larvae overwinter in the soil. They wake up in the spring as soon as it warms up. The places inhabited by the bear can be easily found by the winding rolls of loose earth and holes that come out to the soil surface, as well as damaged plants. Usually in May, bears make nests in the ground at a depth of up to 15 centimeters the size of a hen's egg and lay 300-350 eggs in them, from which larvae (nymphs) soon appear, living in the soil for more than a year. And the entire period of development of a bear from an egg to an adult insect lasts about two years. They destroy the bear with the help of poisoned baits or mechanically. The activity of such widespread insects as ants is great, but since their role in the garden is very diverse, we will talk about them separately, as well as about earthworms, frogs, birds, bees, and here we will briefly touch on only the main ones after earthworms - rodents and moles.

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When we enter the forest on a summer day, we immediately notice fluttering butterflies, singing birds, jumping frogs, we rejoice at a running hedgehog, meeting a hare. One gets the impression that it is these well-visible animals that form the basis of our fauna. In fact, the animals that are easy to see in the forest are only an insignificant part of it.

The basis of the population of our forests, meadows, fields is made up of soil animals. The soil, at first glance so lifeless and unsightly, turns out, upon close examination, literally stuffed with life. If you look closely, you will see extraordinary pictures.

Some inhabitants of the soil are not difficult to see. These are earthworms, centipedes, insect larvae, small mites, wingless insects. Others can be viewed with a microscope. In the thinnest films of water that envelop the soil particles, rotifers, flagellates scurry, amoebas crawl, roundworms wriggle. How many real toilers are here, indistinguishable to the naked eye, but doing, nevertheless, a titanic job! All these invisible creatures keep our common home - the Earth - clean. Moreover, they also warn of the danger that threatens this house when people behave unreasonably in relation to nature.

In the soil of central Russia, per 1 m 2, you can find up to 1 thousand species of soil dwellers that are very different in number: up to 1 million ticks and springtails, hundreds of millipedes, insect larvae, earthworms, about 50 million roundworms, the number of protozoa is even difficult estimate.

This whole world, living according to its own laws, ensures the processing of dead plant residues, cleaning the soil from them, maintaining a water-resistant structure. Soil animals constantly plow the soil, moving particles upward from the lower layers.

In all terrestrial ecosystems, the overwhelming majority of invertebrates (both in the number of species and in the number of individuals) are inhabitants of the soil or are closely related to the soil at a certain period of their life cycle. According to calculations by Boucle (1923), the number of insect species associated with soil is 95–98%.

There are no animals equal to nematodes in their ability to adapt to living conditions. In this respect, they can only be compared with bacteria and the simplest unicellular organisms. This universal adaptability is largely due to the development of a dense outer cuticle in nematodes, which increases their vitality. In addition, the body shape and movement patterns of nematodes were found to be suitable for life in various environments.

Nematodes take part in the mechanical destruction of plant tissues: they are "drilled" into dead tissue and, with the help of secreted enzymes, destroy cell walls, opening ways for bacteria and fungi to enter.

In our country, losses in the yield of vegetables, grain and industrial crops due to damage from roundworms sometimes reach 70%.

The formation of tumors - galls - on the roots of the host plant causes another pest - southern rootworm nematode(Meloidogyne incognita). It brings the greatest harm to vegetable growing in the southern regions, where it is found in the open field. In the north, it is found only in greenhouses, damaging mainly cucumbers and tomatoes. The main harm is done by females, while males, having completed development, go into the soil and do not feed.

Soil nematodes have a bad reputation: they are seen primarily as pests of cultivated plants. Nematodes destroy the roots of potatoes, onions, rice, cotton, sugarcane, sugar beet, ornamental and other plants. Zoologists are developing measures to combat them in the fields and in greenhouses. A great contribution to the study of this group of animals was made by the famous evolutionary biologist A.A. Paramonov.

Nematodes have long attracted the attention of evolutionists. They are not only extremely diverse, but also remarkably resistant to physical and chemical factors. Wherever they begin to study these worms, new species unknown to science are found everywhere. In this regard, nematodes seriously claim a second place - after insects - in the animal world: experts believe that there are at least 500 thousand species, but there is reason to believe that the true number of nematode species is much higher.

General characteristics.

Soil - is a product of the vital activity of organisms, including microorganisms, both modern and belonging to "former biospheres". Soil is the most important component of any ecological system of the land, on the basis of which the development of plant communities takes place, which in turn form the basis food chains all other organisms that form the ecological systems of the Earth, its biosphere. People are no exception here: the well-being of any human society is determined by the availability and condition of land resources, soil fertility.

Meanwhile, during the historical time, up to 20 million km2 of agricultural land has been lost on our planet. For every inhabitant of the Earth, today there is an average of only 0.35-0.37 hectares, whereas in the 70s this value was 0.45-0.50 hectares. If the current situation does not change, then in a century, at such a rate of losses, the total area of \u200b\u200bland suitable for agriculture will decrease from 3.2 to 1 billion hectares.

V.V. Dokuchaev identified 5 main soil-forming factors:

· Climate;

· Parent rock (geological base);

· Topography (relief);

· alive organisms;

At present, human activities can be called another factor in soil formation.

Soil formation begins with primary succession, manifested in physical and chemical weathering, leading to loosening from the surface of parent rocks such as basalts, gneisses, granites, limestones, sandstones, shales. This weathering layer is gradually colonized by microorganisms and lichens, which transform the substrate and enrich it with organic matter. As a result of the activity of lichens in the primary soil, the most important elements of plant nutrition, such as phosphorus, calcium, potassium and others, accumulate. Plants can now settle on this primary soil and form plant communities that define the face of biogeocenosis.

Gradually, the deeper layers of the earth are involved in the soil formation process. Therefore, most soils have a more or less pronounced layered profile, divided into soil horizons. A complex of soil organisms settles in the soil - edaphon : bacteria, fungi, insects, worms and burrowing animals. Edafon and plants participate in the formation of soil detritus, which is passed through the body by detritivores - worms and insect larvae.

For example, earthworms on a hectare of land process about 50 tons of soil per year.

During the decomposition of plant detritus, humic substances are formed - weak organic humic and fulvic acids - the basis of soil humus. Its content ensures the structure of the soil and the availability of mineral nutrients to plants. The thickness of the humus-rich layer determines the fertility of the soil.

Soil contains 4 important structural components:

· Mineral base (50-60% of the total soil composition);

· Organic matter (up to 10%);

Air (15-20%);

Water (25-35%).

Mineral base - an inorganic component formed from the parent rock as a result of its weathering. Mineral fragments vary in size (from boulders to grains of sand and the smallest particles of clay). It is the skeletal soil material. It is divided into colloidal particles (less than 1 micron), fine soil (less than 2 mm) and large fragments. The mechanical and chemical properties of the soil are determined by the small particles.

The structure of the soil is determined by the relative content of sand and clay in it. The most favorable for plant growth is soil containing sand and clay in equal amounts.

In the soil, as a rule, 3 main horizons are distinguished, differing in mechanical and chemical properties:

· Upper humus-accumulative horizon (A), in which organic matter is accumulated and converted, and from which some of the compounds are carried down by washing waters.

· Washout horizon or illuvial (B), where the substances washed from above are deposited and converted.

· Mother breed or horizon (C), material that is converted to soil.

Within each layer, more fractional horizons are distinguished, differing in their properties.

The main properties of the soil as ecological environment are its physical structure, mechanical and chemical composition, acidity, oxidation-reduction conditions, organic matter content, aeration, moisture capacity and moisture content. Various combinations of these properties form many varieties of soils. On Earth, in terms of prevalence, the leading position is occupied by five typological groups of soils:

  1. soils of humid tropics and subtropics, mainly red earth and yellow soils characterized by the richness of the mineral composition and high mobility of organic matter;
  2. fertile soils of savannas and steppes - chernozems, chestnut and brown soils with a thick humus layer;
  3. scarce and extremely unstable soils of deserts and semi-deserts belonging to various climatic zones;
  4. relatively poor soils of temperate forests - podzolic, sod-podzolic, brown and gray forest soils ;
  5. permafrost soils, usually shallow, podzolic, marsh , gley depleted in mineral salts with a poorly developed humus layer.

There are floodplain soils along the river banks;

Saline soils are a separate group: salt marshes, salt licks, and etc. which account for 25% of soils.

Salt marshes - soils are constantly highly moistened with saline waters up to the surface, for example, around bitter-salt lakes. In summer, the surface of salt marshes dries up, covered with a salt crust.

Salt licks - not saline from the surface, the top layer is leached, structureless. The lower horizons are compacted, saturated with sodium ions, and when dry, they crack into pillars and lumps. The water regime is unstable - in the spring - stagnation of moisture, in the summer - severe drying out.

Saline

Solanchak salt licks

Solonetzic soils (slightly salted)

Soil organic matter.

Each type of soil corresponds to a certain plant, animal world and the collection of bacteria - edaphon. Dying or dead organisms accumulate on the surface and inside the soil, forming soil organic matter called humus ... The humification process begins with the destruction and grinding of organic matter by vertebrates, and then it is transformed by fungi and bacteria. These animals include phytophages feeding on tissues of living plants, saprophages consuming dead plant matter, necrophages feeding on animal corpses, coprophages , destroying animal excrement. All of them make up a complex system called saprophilic complex of animals .

Humus differs in the type, shape and nature of its constituent elements, which are subdivided into humic and non-humic substances. Non-humic substances are formed from compounds found in plant and animal tissues, for example, proteins and carbohydrates. When these substances decompose, carbon dioxide, water, ammonia are released. The energy generated by this is used by soil organisms. In this case, complete mineralization of nutrients occurs. As a result of the vital activity of microorganisms, humic substances are processed into new, usually high-molecular compounds - humic acids or fulvic acids .

Humus is subdivided into nutritious, which is easily processed and serves as a source of nutrition for microorganisms, and stable, which performs physical and chemical functionsby controlling the balance of nutrients, the amount of water and air in the soil. Humus tightly sticks together mineral soil particles, improving its structure. Soil structure also depends on the amount of calcium compounds. The following soil structures are distinguished:

· mealy,

· powdery

· grainy,

· nutty,

· lumpy

· clayey.

The dark color of humus contributes to better soil warming, and its high moisture content contributes to the retention of water in the soil.

The main property of the soil is its fertility, i.e. the ability to provide plants with water, mineral salts, air. The thickness of the humus layer determines the fertility of the soil.

Humidity and aeration.

Soil water is subdivided into:

· gravitational,

· hygroscopic,

· capillary,

· vaporous

Gravitational water - mobile, is the main type of mobile water, fills wide gaps between soil particles, seeps down by gravity until it reaches groundwater. Plants absorb it easily.

Hygroscopic water in the soil is retained by hydrogen bonds around individual colloidal particles in the form of a thin, strong cohesive film. It is released only at a temperature of 105 - 110 ° C and is practically inaccessible to plants. The amount of hygroscopic water depends on the content of colloidal particles in the soil. In clay soils, it is up to 15%, in sandy soils - 5%.

As the amount of hygroscopic water accumulates, it turns into capillary water, which is retained in the soil by surface tension forces. Capillary water easily rises to the surface through the pores from groundwater, evaporates easily, and is freely absorbed by plants.

The vaporous moisture occupies all pores free from water.

There is a constant exchange of soil, ground and surface waters, changing its intensity and direction depending on the climate and seasons.

All moisture-free pores are filled with air. On light (sandy) soils, aeration is better than on heavy (clay) soils. The air regime and the humidity regime are related to the amount of precipitation.

Ecological groups of soil organisms.

On average, the soil contains 2-3 kg / m2 of live plants and animals, or 20-30 t / ha. Moreover, in temperate plant roots are 15 t / ha, insects 1 ton, earthworms - 500 kg, nematodes - 50 kg, crustaceans - 40 kg, snails, slugs - 20 kg, snakes, rodents - 20 kg, bacteria - 3 tons, mushrooms - 3 tons, actinomycetes - 1.5 tons, protozoa - 100 kg, algae - 100 kg.

The heterogeneity of the soil leads to the fact that for different organisms it acts as a different environment. By the degree of connection with soil as a habitat animalscombined into 3 groups:

· Geobionts - animals permanently living in the soil (earthworms, primary wingless insects).

· Geophylls - animals, part of the cycle of which necessarily takes place in the soil (most insects: locusts, a number of beetles, long-legged mosquitoes).

· Geoxenes - animals that sometimes visit the soil for temporary shelter or refuge (cockroaches, many hemiptera, coleoptera, rodents, and other mammals).

Depending on the size of the soil inhabitants, it can be divided into the following groups.

· Microbiotype, microbiota - soil microorganisms, the main link in the detrital chain, an intermediate link between plant residues and soil animals. These are green, blue-green algae, bacteria, fungi, protozoa. The soil for them is a system of micro-reservoirs. They live in soil pores. They are able to tolerate soil freezing.

· Macrobiotype, macrobiota - large soil animals, up to 20mm in size (insect larvae, millipedes, earthworms, etc.). the soil for them is a dense medium that provides strong mechanical resistance when moving. They move in the soil by expanding natural wells by moving the soil particles apart or by digging new passages. In this regard, they have developed adaptations for digging. There are often specialized respiratory organs. They also breathe through the integument of the body. For the winter and during the dry period, they move to deep soil layers.

· Megabyotype, megabyota - large diggers, mainly mammals. Many of them spend their whole lives in the soil (golden mole, mole vole, zokors, moles of Eurasia, marsupial moles of Australia, mole rats, etc.). A system of holes and passages is laid in the soil. They have underdeveloped eyes, a compact, rolling body with a short neck, short thick fur, strong compact limbs, digging limbs, strong claws.

· Burrowers - badgers, marmots, ground squirrels, jerboas, etc. They feed on the surface, reproduce, hibernate, rest, sleep, escape from danger in soil burrows. The structure is typical for terrestrial ones, however, burrowers have adaptations - strong claws, strong muscles on the forelimbs, a narrow head, and small auricles.

· Psammophiles - residents of loose sands. They have peculiar limbs, often in the form of "skis", covered with long hairs, horny outgrowths (fine-toed ground squirrel, comb-toed jerboa).

· Gallophiles - inhabitants of saline soils. They have adaptations for protection from excess salts: dense integuments, devices for removing salts from the body (larvae of desert darkling beetles).

Plants are divided into groups depending on the requirements for soil fertility.

· Eutotrophic or eutrophic - grow on fertile soils.

· Mesotrophic - less demanding soil fertility.

· Oligotrophic - content small amount nutrients.

Depending on the exactingness of plants for individual soil trace elements, the following groups are distinguished.

· Nitrophils - they are demanding on the presence of nitrogen in the soil, they settle where there are additional sources of nitrogen - felling plants (raspberries, hops, bindweed), garbage (nettle shiritsa, umbrella plants), pasture plants.

· Calciophils - demanding for the presence of calcium in the soil, settle on calcareous soils (lady's slipper, Siberian larch, beech, ash).

· Calciophobes - plants avoiding soils with a high calcium content (sphagnum mosses, marsh, heather, warty birch, chestnut).

All plants are subdivided into 3 groups depending on the soil pH requirements.

· Acidophiles - Plants that prefer acidic soils (heather, whitewort, sorrel, small sorrel).

· Basiphylls - plants that prefer alkaline soils (coltsfoot, field mustard).

· Neutrophils - plants that prefer neutral soils (meadow foxtail, meadow fescue).

Plants growing on saline soils are called halophytes (European salineros, gnarled sarsazan), and plants that cannot withstand excessive salinization - glycophytes ... Halophytes have a high osmotic pressure, allowing the use of soil solutions, are able to release excess salts through the leaves or accumulate them in their body.

Plants adapted to free-flowing sands are called psammophytes ... They are able to form adventitious roots when covered with sand, adventitious buds are formed on the roots when they are exposed, often have a high growth rate of shoots, flying seeds, strong covers, have air chambers, parachutes, propellers - devices for not falling asleep with sand. Sometimes a whole plant is able to break away from the ground, dry out and, along with the seeds, be carried by the wind to another place. Seedlings sprout quickly, arguing with the dune. There are adaptations for the transfer of drought - covers on the roots, suberization of roots, strong development of lateral roots, leafless shoots, xeromorphic foliage.

Plants growing in peat bogs are called oxylophytes ... They are adapted to high soil acidity, strong moisture, anaerobic conditions (wild rosemary, sundew, cranberry).

Plants that live on stones, rocks, and scree are lithophytes. As a rule, these are the first settlers on rocky surfaces: autotrophic algae, crustose lichens, leaf lichens, mosses, lithophytes from higher plants. They are called crevice plants - hasmophytes ... For example, saxifrage, juniper, pine.