Plays an important role in soil formation processes. Organisms and their role in soil formation and soil fertility. The role of microorganisms in soil formation

Three groups of organisms participate in soil formation: green plants, microorganisms and animals that form complex biocenoses on land.

At the same time, the functions of each of these groups as soil formers are different.

GREEN PLANTS are the only primary source of organic substances in the soil, and their main function as soil formers should be considered the biological cycle of substances - the supply of nutrients and water from the soil, the synthesis of organic mass and its return to the soil after the completion of the life cycle. The consequence of the biological cycle is the accumulation of potential energy and elements of nitrogen and ash nutrition of plants in the upper part of the soil, which determines the gradual development of the soil profile and the main property of the soil - its fertility. Green plants participate in the transformation of soil minerals - the destruction of some and the synthesis of new ones, in the formation of the composition and structure of the entire root-inhabited part of the profile, as well as in the regulation of water-air and thermal regimes. The nature of the participation of green plants in soil formation varies depending on the type of vegetation and the intensity of the biological cycle.

MICROORGANISMS. The main functions of MO are the decomposition of residues and soil humus to simple salts used by plants, participation in the formation of humic substances, and in the destruction and new formation of soil minerals. The ability of some MO groups to fix atmospheric nitrogen is also important.

ANIMALS (protozoa, invertebrates and vertebrates).

Protozoa– flagellates, rhizomes and ciliates. The role of protozoa in soil processes is not clear. It is possible that protozoa, by eating old bacterial cells, facilitate the reproduction of the remaining ones and lead to the appearance of. the number of younger biologically active individuals.

Earthworms. Their role is varied - they improve the physical properties, structure of the soil and its chemical composition.

By making passages and burrows, they improve the physical properties of the soil: increasing its porosity, aeration, moisture capacity and water permeability. They enrich the soil with caprolites, which contributes to an increase in the amount of humus, an increase in the amount of exchangeable bases, a decrease in soil acidity and a more water-resistant structure.

Insects(beetles, ants, etc.). By making numerous moves in the soil, they loosen the soil and improve its physical and water properties. Insects, actively participating in the processing of plant residues, enrich the soil with humus and minerals.

Vertebrates(rodents) - dig holes in the soil, mixing and throwing a huge amount of earth to the surface.

Modern idea of ​​humus formation

The process of converting organic residues in the soil is called humus formation, the result of which is education humus.

The transformation of organic residues into humus occurs in the soil with the participation of microorganisms, animals, air oxygen and water.

The transformation of organic residues into humus (humus formation) is a set of processes of decomposition of initial organic residues, synthesis of secondary forms of microbial plasma and their humification. Scheme according to Tyurin:

The processes of decomposition and mineralization of organic residues are biocatalytic in nature and proceed according to the following scheme with the participation of enzymes secreted by microorganisms.

The main point of all hypotheses about humification is the idea of ​​humification as a system of reactions of condensation or polymerization of monomers - relatively simple intermediate decomposition products - amino acids, phenols, quinones, etc. (A.G. Trusov, M.M. Kononova, V. Flyig, F. Duchaufour).

Another hypothesis of humification was proposed in the 30s of the current century by I.V. Tyurin. He believed that the main feature of humification are the reactions of slow biochemical oxidation of various high-molecular substances with a cyclic structure. For substances that easily humify in soil, I.V. Tyurin included proteins of plant and microbial origin, lignin, and tannins.

I.V. Tyurin’s hypothesis was confirmed and further developed in the works of L.N. Alexandrova and her staff. Research has shown that humification is a complex bio-physical-chemical process of converting high-molecular-weight intermediate products of the decomposition of organic residues into a special class of organic compounds - humic acids. Humification is a long process during which gradual aromatization of humic acid molecules occurs not due to condensation, but through partial elimination of the least stable part of the macromolecule of newly formed humic acids.

Humification develops not only in soils, but also at the bottom of reservoirs, in composts, during the formation of peat, coal, i.e. wherever plant residues accumulate and conditions are created that are favorable for the life of microorganisms and the development of this process, which is very widespread in nature.

Conditions affecting the process of soil formation and humus formation:

water-air and thermal regimes of soils,

composition and nature of input of plant residues,

species composition and intensity of microorganism activity,

mechanical composition,

physical and chemical properties of soil.

Under aerobic conditions with a sufficient amount of moisture (60-80% of the total moisture capacity) and a favorable temperature (25-30°C), organic residues decompose intensively, and mineralization of intermediate decomposition products and humic substances proceeds intensively. As a result, it accumulates in the soil little humus And many elements ash and nitrogen nutrition of plants (for example, in gray soils and other subtropical soils).

Anaerobic conditions inhibit the process of decomposition and mineralization, the process of humification is actively underway, as a result of which stable humic substances are formed.

Humic substances arise from proteins, lignin, tannins and other components of plant, animal and microbial residues.

Humus formation is influenced by the chemical composition of decomposing organic residues and the species composition of soil microorganisms and the intensity of their vital activity.

Humus formation is influenced by the mechanical composition and physicochemical properties of soils:

in sandy and sandy loam soils - good aeration, rapid decomposition of organic residues and mineralization of residues and humic substances;

in clayey and loamy soils, the process of decomposition of organic residues slows down, and more humic substances are formed.

Along with green plants, microorganisms play an important role in the soil-forming process. These are predominantly single-celled organisms lacking chlorophyll, which are not capable of directly absorbing solar energy and, in the overwhelming majority, obtain the energy they need through the decomposition of ready-made organic substances created by higher green plants.

Thus, the activity of microorganisms is the opposite of the activity of green plants: while green plants synthesize organic matter from mineral compounds, water and carbon dioxide, lower organisms decompose this organic matter into its component parts, using the energy released for their life activity.

Microorganisms are distributed almost everywhere in nature. They are found in the soil and air, on high mountains and bare rocks, in the desert and in the depths of the Arctic Ocean.

The development of microorganisms in the soil is closely related to organic matter: the richer the soil in plant residues, the more microorganisms it contains. Cultivated soils that are well cultivated and fertilized with manure are especially rich in them.

1 g of soddy-podzolic soil contains 300-400 million bacteria; chestnut soils - 1-1.5 billion; chernozems, very rich in organic matter, - 2-3 billion. Despite the negligible size of microorganisms, their total weight in the soil often reaches 1-3 tons per 1 hectare.

Microorganisms are unevenly distributed in the soil layer. The upper layers of soil are richest in them within approximately 30-40 cm; with depth, the number of microorganisms gradually decreases.

The root system of plants has a great influence on the distribution of microflora in the soil. It constantly releases various organic and mineral compounds into the environment, which serve as a good source of nutrition for microorganisms. In the root zone of plants, the most favorable water and air regimes for microorganisms are usually created. This root zone is called the rhizosphere. The number of microorganisms in it is hundreds and sometimes thousands of times greater than outside the root zone. Microorganisms cover the root system of plants with an almost continuous layer. The abundance of microflora in the rhizosphere and throughout the soil layer plays a large role in the development of soil fertility.

World organisms include bacteria, which are divided into:

- autotrophic bacteria, they absorb carbon from carbon dioxide, using the energy of oxidation of certain mineral compounds (chemoautotrophs);

Heterotrophic bacteria, they use the energy of the Sun to carry out photosynthesis (photoautotrophs).

Nitrogen-containing organic compounds resulting from the process ammonification Under the influence of decomposition by bacteria, ammonia is formed. It can be partially absorbed by the soil, converted into nitrates or molecular nitrogen. In progress nitrification Ammonia is initially converted to nitrous acid and later to nitric acid. Nitric acid combines with bases in the soil to produce nitrates, which are used by plants as nitrogen food.

Nitrogen-fixing bacteria play a great role in increasing soil fertility. They are divided into:

1 free-living bacteria that participate in the decomposition of organic matter to mineral matter;

2 nodule bacteria that inhabit cells on the roots of leguminous plants (clover, beans), as a result of which microbiological accumulation of nitrogen from the atmosphere occurs;

3 heterotrophic bacteria that absorb carbon from ready-made organic compounds, decomposing complex compounds into simple ones. Due to their activity, dead organic matter is destroyed with the formation of mineral substances (decomposers). As a result of biochemical transformations, the nitrogen contained in the proteins of organic substances, under the influence of heterotrophic bacteria, becomes available for absorption by plants.

Microorganisms that decompose organic residues in the soil are divided into three main groups: aerobic bacteria, anaerobic bacteria and fungi.

Aerobic bacteria can live and multiply only with free access to air. Insufficient air supply has a depressing effect on the vital activity of these bacteria, and complete cessation of air supply causes death.

Anaerobic bacteria develop without access to free oxygen. Anaerobes are divided into:

a) obligate anaerobes (lat. obligatus - obligatory, indispensable), which can live only in the complete absence of oxygen;

c) facultative anaerobes (pfacultatif - possible, optional), capable of living both in the absence of oxygen and in the presence of it.

For respiration, anaerobic bacteria use the oxygen of various oxidized compounds, while performing reduction work. Therefore, reduction processes are very typical for anaerobic soil conditions.

In loose, well-ventilated soils, the aerobic process of decomposition of organic matter always predominates. On the contrary, in soils that are compacted, heavy or swampy, with continuous organic matter, anaerobic processes will inevitably dominate. In the upper layers of the soil, where air penetrates freely, mainly aerobic processes take place, while in the lower layers with difficult gas exchange, anaerobic processes take place. Moreover, in each individual, more or less compacted, lump of soil, both processes can occur simultaneously: inside the lump anaerobic, in the surface parts aerobic.

The aerobic process is accompanied by the release of thermal energy, while the anaerobic process proceeds without a noticeable increase in temperature.

Favorable conditions for cultivated plants can be created in the soil only with the simultaneous development of aerobic and anaerobic processes, which is only possible in loose soils with good aeration.

Higher plants, as producers and the main source of organic matter entering the soil, play a special role in soil formation.

They are a kind of powerful pump that pumps chemical elements and water from the soil to their organs. Plant roots, penetrating into the soil, loosen it and actively influence its phase composition.

The forest area on the planet is about 30%. Optimal conditions for forest vegetation are the excess of total precipitation over evaporation. Excess moisture with the dominance of woody, especially coniferous, vegetation promotes intensive leaching of dissolved compounds, deep destruction of minerals and removal of soil-forming products beyond the profile.

Under forest vegetation in the soils, a specific biocenosis of vertebrates, invertebrates, and fungi is formed. The total phytomass of forest vegetation ranges from 3 to 5 thousand centners/ha, with about 500 centners/ha accounting for rhizomass, i.e. roots.

The main role in forest soil formation belongs to ground litter and thin roots. The total surface of the sucking root endings of a hundred-year-old pine stand per 1 hectare can be up to 1.5 hectares. In conifers, up to 95% of the rhizomass is concentrated in the top layer of soil (0-30 cm). Mycorrhiza is always associated with tree roots. Therefore, a significant number of microorganisms live in the rhizosphere of trees, and the number of protozoa is 5-10 times higher compared to their average content in soils.

The acidity of the soil in coniferous forests increases due to the leaching of acidic substances from living leaves, pine needles and bark by rainwater. Acidification to pH 3.3-4.5 can be caused by the activity of mosses and lichens. In the rhizosphere of coniferous species, the concentration of hydrogen ion is always higher (pH lower by 0.2-0.6) than outside the rhizosphere. An aqueous extract from spruce needles has a pH of about 4, from pine litter - 4.5, and leaves of broad-leaved trees - about 7. The sharp differences in the reaction of solutions of products from leaves and needles are explained by the fact that leaves and needles have different ash contents and base contents . With low ash content, the litter may have a pH of about 4.5-4.6. The neutral reaction is typical for the forest floor of deciduous forests.

The roles of woody and herbaceous vegetation in soil formation are significantly different. This is due to the depth of penetration into the soil layer and the distribution of the root system, as well as differences in the amount and nature of the entry of plant residues into the soil and their ash composition.

The set of processes by which plants absorb chemical elements from the soil, synthesize and decompose organic matter, and return chemical elements to the soil is called the biological cycle of substances in the plant-soil system.

Some chemical elements participating in the biological cycle are not retained by the soil, are carried by geochemical intrasoil runoff beyond the soil profile and are included in the large geological cycle of chemical elements.

To characterize the biological cycle of substances, the following indicators are used: reserves of phytomass (centner/ha) in the above-ground and underground parts of plants, the amount of annual growth of phytomass and litter, the content of ash chemical elements in different parts of plants and in litter. The ratio of the mass of litter to the mass of annual litter serves as an indicator of the intensity of the biological cycle.

The root system of plants absorbs macroelements (Ca, N, K, P, S, Al, Fe) and microelements (Zn, B, Mn...) from the soil solution of mineral nutrition and releases ions (H +, OH -) and enzymes in equivalent quantities and other organic compounds actively involved in soil processes. On average, temperate climate vegetation absorbs 100-600 kg/ha of minerals from the soil annually. The amount of chemical elements absorbed from the soil and returned to it with plant litter depends on the type of phytocenosis.

Agrocenoses, replacing biogeocenoses, make enormous changes in the biological cycle of substances. With the harvest of cultivated plants, a colossal amount of ash elements is irretrievably removed from the soil. Thus, with a wheat harvest of 20-25 kg/ha, up to 150-200 kg/ha of basic mineral nutrition elements (N, P, K, Ca, Mn, Fe, S, Si, Al, Mg) are removed from the soil.

The rate of decomposition of organic residues and the nature of the substances formed as a result of this process depend on climatic conditions and the composition of vegetation. The chemical composition of organic substances formed during photosynthesis depends on the type of plant. Mosses and wood have a high lignin content. Cereals contain a lot of hemicellulose, and pine needles contain wax, fats and resins.

During the decomposition of organic residues, ash elements absorbed by plants from the soil are returned to the soil.

The intensity index of the biological cycle of substances is maximum in swampy landscapes (more than 50), where there is a progressive accumulation of peat and the formation of bog peat soils. In dark coniferous taiga forests, the intensity index of the biological cycle is much lower (10-17). Mineralization of litter in coniferous forests occurs slowly and organic horizons form on the soil surface, and the formation of a peat layer is often observed. The intensity of the biological cycle in the steppes is 1.0-1.5. The steppe felt formed in natural steppe ecosystems from herbaceous vegetation decomposes within a year.

The decomposition products of needles, leaves, grasses, and trunks differ in their chemistry and influence on soil formation. Thus, the decomposition products of steppe grasses have a reaction close to neutral (pH = 7). Extracts from spruce needles, heather, lichens, and sphagnum moss have an acidic reaction (pH 3.5-4.5). Extracts from wormwood have an alkaline reaction (pH 8.0-8.5).

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Animals inhabit the entire globe: land surface, soil, fresh water and seas. While climbing Chomolungma (Everest), climbers noticed chough mountain birds at an altitude of about 8000 m. Worms, crustaceans, mollusks and other animals have been found in the deepest depressions of the World Ocean down to a depth of 11,000m. Many animals live secretly or are microscopic in size, so we don't notice them. Other animals, on the contrary, are constantly encountered by us, for example, insects, birds, animals.

The significance in nature is as great as the significance of plants. Many plants are pollinated only by animals, and animals also play a large role in dispersing the seeds of some plants. To this it should be added that animals, along with bacteria, take an active part in the formation of soil. Earthworms, ants and other small animals constantly introduce organic matter into the soil, crush it and thereby contribute to the creation of humus. The burrows of these burrowing animals more easily penetrate the water and air necessary for plant life to the roots. From botany you know that green plants enrich the air with oxygen, necessary for the breathing of all living beings. Plants serve as food for herbivorous animals, which in turn serve as food for carnivorous animals. Thus, animals cannot exist without plants. But the life of plants, as was said, depends on the life of animals. The sanitary importance of animals is very great - they destroy the corpses of other animals, the remains of dead plants and fallen leaves. Many aquatic animals purify water, the purity of which is as important for life as the purity of air.

The animal world has always been and is very important to us. Our distant ancestors, who lived 100-150 thousand years ago, knew wild animals, birds, fish and other animals. This is understandable: after all, people’s lives largely depended on hunting and fishing. The meat of hunted animals was one of the main sources of food; clothing was made from the skins of killed animals; knives, scrapers, needles, and spear tips were made from bones. Tendons were used when sewing skins instead of threads and for bow strings. The success of the hunt depended not only on the strength and dexterity of the hunters. But it also depends on the ability to detect a bird’s nest or an animal’s lair, and find the necessary trace. Choose the right time for the raid. Some animals had to be caught in placed snares and nets, others had to be laid in wait, hiding, and others had to be noisily pursued by the whole tribe and driven into camouflaged pits. It was also important for humans to escape from predators. Distinguish poisonous snakes from harmless ones. Having studied the habits of wild animals, ancient people managed to tame some of them. The first domestic animal was a dog, which was used as a hunting assistant. Later domestic pigs appeared. Cattle, poultry.

Over time, the role of animals in human life has changed. The importance of wild animals as a source of food decreased markedly as meat, wool and milk began to be obtained from domestic animals. But humans have new enemies from the animal world - various insects that harm cultivated plants. knows many examples of starvation of entire nations as a result of the destruction of crops by hordes of locusts. In the 20th century as a result of the enormous scale of human economic activity - deforestation. Construction of hydroelectric power stations, expansion of cultivated areas, etc. - many wild animals found themselves in difficult living conditions, their numbers decreased, some species became rare, others disappeared. Predatory fishing exterminated valuable animals. There was a need for their protection. It is known that animals play a very important role in providing the world's population with food and raw materials for industry. A significant proportion of food products, as well as leather, wax, silk, wool and other raw materials, are obtained from domestic animals. Fishing, especially marine fishing, and fishing for crustaceans and mollusks are also important for obtaining food products and vitamins. Medicines, etc. Feed flour for fattening livestock and fertilizer are prepared from fishing waste. Fur of wild animals (leather, horns, shells, etc.). Many animals (for example, birds and predatory insects) play a large role in the destruction of pests of cultivated and valuable wild plants. There are many animals known to cause damage to human economies. Among them are various pests of cultivated plants, animals that destroy food supplies, damage products made of leather, wool, wood, etc. There are such animals. Which cause various diseases (malaria, helminthic diseases, scabies, etc.). Some animals are carriers of diseases (lice carry typhus from sick people, mosquitoes carry malaria, fleas carry plague).

The animal world is an important part of the natural environment. Taking care of it is the basis for its wise use. Knowing the characteristics of individual species. Their role in nature allows a person to protect animals that are useful to him, help increase their numbers, and limit the proliferation of agricultural pests, carriers and pathogens. In our country, caring for the animal world is given great importance

The role of animals in soil formation, even more than that of plants, is associated with their biogeocenological activity.

Academician S.S. Schwartz believed that the evolution of organisms is inextricably linked with their role in the biogeocenosis and with the evolution of the biogeocenosis itself. The ecosystem and biogeocenosis determine the resistance of an animal species to various adverse influences, their variability, and even the problem of the origin of life itself is connected specifically with the primary ecosystem: the conditions for the emergence of life were an ecological component of the first ecosystem.

The connection of animals with the soil and their participation in soil formation can be different. Animals live in the soil itself, on its surface, above the surface of the soil. Some of them change their lifestyle depending on the season, the stages of their development, and the availability of food. Others lead only one lifestyle. It is clear that the role of all these animals should be assessed based on the specific conditions of their habitat.

Animals living in the soil primarily include invertebrates, insects, earthworms, etc. The largest amount of data has been accumulated on the activities of earthworms. The role of worms in soil processing, noted by Darwin, has already been mentioned. A ten-centimeter layer of garden soil developed on carbonate rock, according to Darwin, within ten years passes through the intestines of worms, enriched with humus, microorganisms, and enzymes. Worms drag plant debris into the soil. Worms make deep passages deep into the soil, through which water penetrates and plant roots go. Worms structure the soil, creating a fine-grained mass enriched with humus, which is resistant to the destructive effects of water. It was discovered that in some soils, such as under ravine forests (forests located in ravines), the upper layer of chernozem consists entirely of coprolites - lumps of soil that have passed through the earthworm's food tract. The coprolite structure of the humus horizon of this soil distinguishes it from the corresponding horizon of ordinary chernozem. Earthworms are the main reason for the digging activity of moles, which, in search of food (and worms are their main food), make their own tunnels in the soil layer.

Ground beetles, widespread beetles that live in the upper layer of soil and on its surface, have been shown by detailed studies to accumulate lead in their bodies. If we consider that ground beetles are predators, then the complex trophic relationship leading to such accumulation is obvious.

Larvae of dipterans (various flies and midges, mosquitoes, etc.) often live in the upper soil layers and participate in the decomposition of litter. They, like worms, improve the humus status of the soil, increase the yield of humic acids, increase the content of nitrogen, ammonium compounds, and overall humus content. Under their influence, the thickness of the humus horizon increases in the initial period of its formation.

Of course, invertebrate animals are accompanied by a certain microflora, which enhances the enzymatic activity of soils. All invertebrates and their larvae make tunnels, loosening and mixing the soil.

Some species of mammals also live in the soil. These are marmots, gophers, mice, moles, shrews, hamsters and many others.

Their impact on the soil is very noticeable. Moles mix the soil and throw material from the lower horizons to the surface. The mass of such emissions can be sixty tons per hectare. Mole rats behave similarly to moles, living in moist, hydromorphic soils of the steppes, in meadow-chernozemic, meadow-chestnut soils along gullies. They also throw soil to the surface and mix the upper horizons, but unlike moles, they feed on plants.

Gophers, a family of sac rats, live in North America. They mainly feed on nuts and roots, which they drag into their burrows to a depth of one and a half meters. Gophers, like moles, throw material from deeper horizons onto the soil surface. Gophers help deepen the soil layer and allow deeper penetration of plant roots.

The role of marmots and gophers in soil formation can reach large scales and be dual. Living in the steppes, they dig deep burrows and throw onto the soil surface material partially enriched with calcium carbonate and various soluble salts. According to zoologists and soil scientists, ground squirrel emissions to the surface contribute to an increase in the salt content in the upper layers of the area surrounding the burrow. This deteriorates the soil and reduces its fertility. But since gophers live in one place for a long time and create a whole system of burrows and passages in the soil, then, after this area is abandoned by gophers, it begins to settle, a depression is formed into which water flows, and ultimately a large depression with more fertile than surrounding soils, often dark-colored.

A special place in soil formation is occupied by mouse-like rodents, lemmings, voles, etc. They create burrows, paths on the soil surface from burrow to burrow, tunnels both in the litter and in the upper layers of the soil. These animals have “toilets” where the soil is enriched with nitrogen and alkalized day after day. Mice contribute to faster grinding of litter, mixing of soil and plant residues. In tundra soils, the main role is played by lemmings, in forest soils - mice and moles, in steppe soils - mole rats, gophers, and marmots.

In a word, all animals living in the soil, one way or another, loosen it, mix it, enrich it with organic matter and nitrogen.

Foxes, badgers, wolves, sables and other land animals make shelters in the soil - burrows. There are entire colonies of burrowing animals that exist in one place for several centuries, and sometimes millennia. Thus, it was found that the badger hole near Arkhangelsk arose on the border of the early and middle Holocene, that is, eight thousand years ago. Near Moscow, the age of a badger's hole exceeded three thousand years. Thus, settlements of burrowing animals may have been founded earlier than even such ancient cities as Rome.

Over the long period of existence of burrows, one can assume a variety of influences of animals on the soil. For example, a change in the composition of plants near burrows. When cleaning out burrows, animals repeatedly buried soil humus horizons, so excavating burrows makes it possible to trace the history of biogeocenosis over a significant period of time.

Wild boars spend the night in secluded places, in swamps, in small forest streams, in dense grasses. At the same time, they compact the soil, promote the regeneration of trees and provide all sorts of “small services” to forest plants, fertilizing them and helping in the fight against competitors.

In soils dug up by wild boars, usually in the first year the content of organic matter in the layer decreases to five centimeters and increases in the layer five to ten centimeters. Wild boars create a special ecological niche in forests for trees, grasses, and animals. Sometimes, under the influence of wild boar, more humus-rich, looser soil is formed, sometimes more bare. Their random distribution within the biogeocenosis does not remove their important role in its life. Wild boars can cause the emergence of a new parcel in a given place, and therefore new soil.

Other large animals (elk, deer) have a lesser impact on the soil, almost without disturbing it. But they often eat aspen, gnawing its bark, and bite off the tops of young pines and spruces. These actions may first affect the vegetation cover and then the soil cover.

Some tropical researchers believe that animals such as elephants engage in a multi-year cycle that helps transform rainforest into savanna - first by destroying shrubs, undergrowth, and then the trees themselves. Elephants leave the savannah when they lack food. After a fire, which often happens in the savannah, it is again overgrown with forest. It is clear that in this cycle the soils themselves and a number of their properties (acidity, humus content, etc.) change.

Tigers and bears have a completely unexpected impact on the soil.

Tigers in our country are found mainly in the Ussuri region and the Amur taiga. One detail of the tiger's behavior has a direct bearing on the soil. The tiger wanders in a certain territory along its favorite paths, often covering distances of several tens of kilometers. From time to time, like a cat, he scrapes the soil near the path with his paw. In this case, of course, the grass and litter are torn off, and the top layer of soil dug up by claws is exposed. After a certain time, the scrape, as zoologists call this place, becomes overgrown, and the soil on it, like on the wild boar’s pores, is enriched with organic matter and can also serve as a new ecological niche for the regeneration of plants.

Tigers in Sikhote-Alin set up their observation posts and resting places on sites located in high rocks, usually with a good view. On these sites a completely specific complex of plants is created, and the soils on them are usually underdeveloped and slightly compacted.

No less interesting is the role of the bear in soil formation processes. The bear does not dig a den; he only finds a suitable place for it under a fallen tree, under roots, etc. In this sense, he does not affect the soil. Its role in soil formation is indirect. Bears make a series of trails along river banks, overgrown with tall grass and bushes and difficult to navigate. These trails are then used by other animals, including herbivores, to search for food. Gradually, thanks to grazing, the vegetation of the coastal part changes, sometimes it is overgrown with forest. And with a change in biogeocenosis, as always, there is a change in soils: soddy soils are replaced by forest soils, soddy-podzolic soils, or others similar to the first.

Bears tear up anthills, which, of course, is harmful for the forest: the enemies of all forest pests are destroyed. But this harm is not so great, since there are enough anthills in the natural forest. Often anthills are renewed in the same place, and sometimes the loose litter of pine needles and branches remains lifeless for a long time, not overgrown with grass after the death of a forest anthill.

When hunting for gophers, bears dig up their passages and burrows, which is accompanied by loosening the soil, increasing water absorption, and increasing humus formation. By biting the tops of berry shoots, bears contribute to the growth of berry patches and the preservation of their corresponding soils. The role of the bear in maintaining berry fields is obviously much more important than it seems at first glance. Some seeds, having passed through the bear's gastrointestinal tract, lose their viability, but others, on the contrary, become more viable. Thus, bears regulate ground cover, which is accordingly transmitted to the soil.

Bears, like wolves, are needed to regulate the number of herbivores. In short, the role of the bear in the biogeocenosis is quite large.

Birds, insects, some mammals, such as squirrels, martens, etc., which make up most of the biogeocenosis, live above the soil. Some of these animals constantly lead an arboreal lifestyle, almost never descending to the ground. But some, like squirrels, descend and build storage areas in the soil for their supplies (nuts, seeds). In spring, untouched reserves germinate and promote plant dispersal. Nutcracker does a similar job. In Kamchatka, the nutcracker collects pine nuts in dwarf cedar, which grows in the mountains at an altitude of eight hundred to nine hundred meters above sea level. Of course, the nutcracker eats grass seeds and rowan berries, but nuts are its main food. For the winter, the nutcracker makes reserves by burying pine nuts in the soil, and very often it makes these reserves in the valley of the Kamchatka River, and not in the mountains, apparently due to the deep snow cover. But if the reserves turn out to be untouched, then in the spring they germinate, and a clump of dwarf cedar is formed among the larch forest. Peaty-coarse humus soil, in turn, is formed under the dwarf dwarf tree.

Particularly noteworthy is the role of insects in biogeocenosis. They pollinate plants, serve as food for other animals, being a link in the trophic chain, and decompose organic substrates: litter, litter, fallen tree trunks. Insects accelerate the circulation of substances in biogeocenoses. Insect larvae living in the soil have already been discussed. But even those that live above the ground can have a significant impact on the soil. Some insects are so-called phytophages. They feed on green foliage of plants. There are xylophages that feed on wood.

The activity of the oak leaf roller, widespread in our deciduous forests, is interesting. The leaf roller butterfly lays eggs in the summer, from which caterpillars emerge in the spring. Caterpillars feed on oak leaves, rolling them into a tube (the name of the insects is associated with this). In June, the caterpillars pupate and then butterflies emerge from the pupae. At the beginning of June, the oak leaves bloom, and there are years when all the foliage on the oak trees is eaten by the leaf roller. Oak forests stand bare as in autumn. But the natural mechanism works, and already in July the oak trees are covered with foliage again, while the leaves of the second generation are usually larger, two to three times larger than the first. This may be the result of trees receiving fertilizer in the form of leaf roller excrement. Research shows that the total mass of foliage is only ten percent less than the mass of foliage in forests untouched by the leaf roller. Leaf roller excrement enriches the soil with available forms of nitrogen, enzymes and humic substances. The total amount of carbon ultimately entering the soil remains the same. And although during the most active activity of the leaf roller caterpillars the forest makes a depressing impression - the trees are bare and a constant rustling is heard - the caterpillars eat the leaves, ultimately the leaf roller accelerates the circulation of matter in the biogeocenosis.

Mosquitoes occupy a special place in forest, tundra, swamp and floodplain biogeocenoses. They also pollinate plants and serve as food for birds and other insects, in particular dragonflies. They concentrate some microelements, such as molybdenum, and enrich the soil with them, thereby stimulating the absorption of nitrogen from the atmosphere.

Many other animals not named here influence the soil and biogeocenosis as a whole. In deserts and semi-deserts, for example, ants bring to the surface several tons of soil material from the lower horizons.

The life of termites is specific. They live in deep layers of soil almost all their lives, feed on coarse fiber, and build special pyramids and tunnels.

Wasps and bumblebees, when digging holes, change the properties of soils, affecting the absorption of water by the soil and its density.

The variety of connections between animals and soils requires research, and interesting discoveries await scientists along the way. It is very important to know the other side of the relationship: how soils affect animals. Previously, these issues were dealt with by ecologists and zoologists who studied the living conditions of animals. But many questions would be clearer if soil scientists also dealt with them.

The biogeocenotic approach requires the study of all the diverse connections in biogeocenoses, which is why soil zoology, which reveals the role of soil in the natural system, is so important.

In recent years, volcanologist E.K. Markhinin has put forward a volcanic hypothesis of the origin of life. He found that during volcanic eruptions, various amino acids are formed in the gas cloud, and other organic substances are synthesized. The volcanic gas cloud contains enormous reserves of energy, which can contribute to the synthesis of substances such as nucleic acids.

But even earlier, in the 30s, academicians N. G. Kholodny and then V. R. Williams expressed a hypothesis about the origin of life in the soil, or more precisely, in a loose substrate, a product of weathering of rocks. Williams called it a weathered piece of junk. In favor of this assumption, we can say that life as a system of self-reproducing units that build themselves from material supplied in limited quantities could most reliably form on a soil particle, a soil matrix, just as polymers of humic substances are now formed on it. If this hypothesis is true, then we can assume that life and soil on our planet arose simultaneously.

Soil-forming rocks greatly influence the speed of the soil-forming process and its direction. The composition and properties of the soils formed on them are largely related to the characteristics of soil-forming rocks, since soils largely inherit their chemical, mineralogical and granulometric composition from the rocks. The relationship between the properties of soils and the nature of the soil-forming rock is especially clear in the early stages of soil formation. At later stages of soil development, this relationship becomes less clear due to the profound transformation that mineral components undergo under the influence of weathering and soil formation processes. Soils formed in the same bioclimatic environment, but on different rocks, have similar properties, but these properties never completely coincide. Even in the humid tropics, where the intensity of weathering and soil formation processes is highest, differences between soils formed on different rocks do not completely disappear. Thus, soils developed on basic and acidic igneous rocks are characterized by the same relative content of monovalent cations and calcium, but have different Si0 2: Al 2 0 3 ratios, reflecting differences in the composition of the parent rocks.

The rate of soil formation, other things being equal, depends on how resistant the rock is to the effects of bioclimatic factors. Soil development slows down with increased rock density, coarse grain size, and high quartz content. There are cases when soils formed on very dense bedrock (granites, granite-gneisses), freed from the glacier 7...10 thousand years ago, remain at the primitive stage, having a profile thickness of 10...15 cm. In depressions and on the interslope plains of the same territory, where the products of glacial deposits (sands, sandy loams, light and sandy loams) act as soil-forming rocks, full-profile podzolic soils have developed.

The direction of the soil-forming process largely depends on the nature of the soil-forming rocks. Differences in the composition and properties of soil-forming rocks within one bioclimatic region can have a significant impact on soil formation. Soils formed on such rocks will belong to different soil types.

On the other hand, under certain bioclimatic conditions, the influence of lithology on the soil-forming process can be so significant that the differences between soils formed by different types of soil formation are smoothed out, and features determined by the genesis and properties of the parent rock come to the fore. For example, solonetzes, solonetzic and solonetzic chernozems of the southern Trans-Urals, formed on a kaolinite weathering crust, are closer to each other according to the most important diagnostic characteristics than each of these soils with soil of the same type formed on a different parent rock.
The material composition and physical properties of the soil-forming rock largely determine the level of soil fertility. Thus, highly fertile soils will never form on poor quartz sands. Rocks rich in nutrients transfer them to soils.

Soils, to a greater or lesser extent, inherit the water-physical properties of soil-forming rocks. Soils developed on sands and sandy loams have a loose texture, high water permeability and low moisture capacity. On loess and loess-like rocks, soils of loamy granulometric composition with optimal water permeability and moisture holding capacity are formed. And soils developed on clays are characterized by high density, low water permeability and high moisture capacity.

Soil-forming rocks play a large role in the formation of the structure of the soil cover. With a homogeneous parent rock in flat, weakly dissected areas, there is a great uniformity (same type) of the soil cover. Under conditions of dissected relief and high diversity of parent rocks, micro- and meso-combinations of contrasting soils - lithogenic mosaics - are formed.