Biological factor of soil formation. Soil formation factors The role of living organisms in creating soil

Soil is the layer of earth that covers the rocks of the earth. It plays an important role in various terrestrial ecosystems. Soil formation factors are various plant and animal organisms, soil-forming rocks, relief, water, climate, age. Also, with the advent of humanity, its economic activity became one of the main ones. Let's consider the factors of soil formation.

Soil-forming rocks

Soil-forming rocks are a nutrient medium in which soil formation processes occur, which contain numerous mineral components involved in soil formation. Approximately 60-90 percent of the total weight of the soil is minerals. The physical properties of the soil (the content of plant nutrients, the rate of movement of substances in the soil, as well as its chemical and mineralogical composition) directly depend on the nature of the parent rocks.

The nature of the parent rocks has a strong influence on the type of soil. Ash-type soils can often be found in forested areas. Soils of the podzolic type can be formed in soil-forming rocks containing a large number of potassium carbonates. But if the soil-forming rocks contained a large amount of calcium carbonates, then the soils will have a significant difference from podzolic soils.

Vegetation as a soil formation factor

During the life activity of various living organisms, plants, and microorganisms, organic compounds are formed in the soil. The main role belongs to vegetation. Green plants are, one might say, the only creators of the very first organic substances. They absorb carbon dioxide from the atmosphere, and they take water and minerals from the soil; with the help of solar energy, they form various non-simple, energy-rich organic compounds. The highest content of organic matter is in forest communities and the tropics, with high humidity. But tundras, deserts and swampy places are deprived of organic matter.

When a plant dies, both as a whole and its individual parts, organic matter enters the soil. Under the influence of animals, bacteria and various chemical and physical agents, decomposition occurs on the soil surface, with the further formation of humus. The mineral part of the soil is enriched with ash substances. Plant material that has not yet had time to decompose forms a protective litter. It is these formations that affect gas exchange processes in the soil, the vital activity of microorganisms, the thermal regime of the topmost layer of soil, and the permeability of precipitation.

Vegetation can affect the structure and nature of organic matter in the soil, as well as its moisture regime. The degree of influence of vegetation on the nature and structure of organic matter depends on the composition and condition of the plants, as well as on numerous other factors.

Animal organisms

Animal organisms are designed to transform organic matter in the soil. Both aboveground and soil animal organisms are involved in the transformation process. The main function in the soil environment is given to protozoa and invertebrates. However, some vertebrates that spend a lot of time in the soil, such as moles, also play an important function. All soil animals can be divided into two groups: biophages and saprophages. The former feed exclusively on living organisms or their tissues, while the latter prefer organic substances.

The main number of soil animals is represented by saprophages (earthworms). A large number of saprophages feed on dead vegetation and then release their excrement into the soil. If you trust Darwin's calculations, then in a few years the entire soil mass passes through the digestive tract of worms. Saprophages play a huge role in creating the soil profile and humus content.

Small rodents are numerous above-ground participants in the soil formation process. Plant and animal residues that fall into the soil begin to participate in a rather complex process of their change. Some of them decompose into water, salts and carbon dioxide, and certain parts turn into complex organic matter in the soil.

Microorganisms

Microorganisms are the main factors of soil formation; they are calculated not even in thousands, but in billions per hectare of soil. They are diverse both in composition and in their biological activity. These are various bacteria, fungi, viruses, unicellular algae and many others. They participate in the biological cycle of substances. With the help of microorganisms, the processes of decomposition of complex organic and mineral substances into simple substances occur. Then simple substances are utilized either by microorganisms themselves or by plants. It is the organic matter formed during the decomposition of plant and animal remains that is called humus or humus.

Climate as a soil formation factor

Climate is an important factor influencing soil formation. The biological and physical processes occurring in the soil depend only on it. It affects the thermal and water regimes of the soil. Thermal regime is a set of heat exchange processes between the “ground layer - soil - soil-forming nature”. The thermal regime is responsible for the processes of heat transfer and accumulation in the soil. The nature of the thermal regime can be determined based on the ratio of absorbed solar energy and thermal radiation of the soil. The nature depends on the heat capacity, soil color, moisture content and other various factors. Vegetation has a great influence on the thermal regime.

Water mode

Basically, the water regime of the soil can be determined by the amount of precipitation and the process of its evaporation. In addition, there is a peculiarity of their distribution throughout the year. Water, washing away the soil, has a significant impact on it and its composition.

Climatic conditions

Climatic conditions can affect soil-forming rocks, flora and fauna, and much more, but this effect is only indirect. Because only the distribution of the main types of soils is related to climatic conditions.

Relief as a soil formation factor

Relief is a soil-forming factor involved in the redistribution of heat and water over the surface of the earth. If there is a change in the altitude of the area, then there is a change in the thermal and water regimes of the soil. The zonality of the mountainous soil cover is determined by the relief. Relief also affects the nature of the influence of groundwater and rainwater on the soil and the migration of water-soluble substances.

Time as a soil formation factor

Time is also an important factor in soil formation, because it is one of the most important processes in nature. The age of soils in Western Siberia, North America, and Western Europe was determined using the radiocarbon method - from several hundred to several thousand years. In addition, in modern times, human economic activity is a particularly significant factor.

Now you know what soil formation factors are.

Soil is a living organism consisting of countless microscopic living beings. The number and diversity of living microorganisms in soil is immeasurable. 1 g of soil contains billions of bacteria, fungi, algae and other organisms, and in addition, a great many earthworms, woodlice, centipedes, snails and other soil organisms, which, as a result of the metabolic process, process dead protein organisms and other organic residues into nutrients available for uptake by plants. Thanks to their activity in the soil, humus is formed from the original plant and protein material, from which, as a result of combining with water and oxygen, nutrients for plants are released. The loose structure of the soil is also achieved largely due to the activities

soil organisms that naturally mix minerals and organic matter, producing a new enriched substance. This significantly increases soil fertility. The study of soil-dwelling animals is the subject of a special branch of science - soil zoology, which was formed only in our century. After specialists developed methods for recording and recording animals, which was associated with significant technical difficulties, a whole kingdom of creatures appeared before the eyes of zoologists, diverse in structure, lifestyle and their significance in the natural processes occurring in the soil. In terms of biological diversity, the fauna of the soil can only be compared with coral reefs - a classic example of the richest and most diverse natural communities on our planet.

Among them are large invertebrates such as earthworms, and microorganisms that cannot be seen with the naked eye. In addition to their small sizes (up to 1 mm), most soil-dwelling invertebrate animals also have an inconspicuous coloring of the body covers, whitish or gray, so they can only be seen after special treatment with fixatives, under a magnifying glass or microscope. Microorganisms form the basis of the animal population of the soil, the biomass of which reaches hundreds of centners per hectare. If we talk about the number of earthworms and other large invertebrates, then it is measured in tens and hundreds per square meter, and the number of small and microscopic organisms reaches millions and billions of individuals.

For example, protozoa and roundworms (nematodes) with a body size of up to 0.01 mm, in their physiology, are typically aquatic creatures capable of breathing oxygen dissolved in water. Their small size allows them to content themselves with microscopic droplets of moisture that fill narrow soil cavities. There the worms move, find food, and reproduce. When the soil dries out, they are able to remain in an inactive state for a long time, becoming covered on the outside with a dense protective shell of solidified secretions.

Larger soil organisms include soil mites, springtails, and small worms - the closest relatives of earthworms. These are already real land animals. They breathe atmospheric oxygen, inhabit air cavities within the soil, root passages, and burrows of larger invertebrates. Small sizes, flexible

Soil organisms are a vital link in a closed metabolic cycle. Thanks to their vital activity, all products of organic origin are decomposed, processed and acquire a mineral form accessible to plants. Minerals dissolved in water move from the soil to the roots of plants, and the cycle begins again

body allow them to use even the narrowest gaps between soil particles and penetrate deep horizons of dense loamy soils. For example, oribatid mites go 1.5-2 m deep. For these small soil inhabitants, the soil is also not a dense mass, but a system of passages and cavities connected to each other. Animals live on their walls, like in caves. Overmoistening of the soil turns out to be just as unfavorable for its inhabitants as drying out. Soil invertebrates with body sizes larger than 2 mm are clearly visible. Here you can find various groups of worms, terrestrial mollusks, crustaceans (woodlice, amphipods), spiders, harvestmen, false scorpions, centipedes, ants, termites, larvae (beetles, dipterous and hymenopteran insects), butterfly caterpillars. Earthworms and some insect larvae have highly developed muscles. By contracting their muscles, they increase the diameter of their body and push soil particles apart. Worms swallow soil, pass it through their intestines and move forward, as if “eating” through the soil. Behind them they leave their excrement with metabolic products and mucus, abundantly secreted in the intestinal cavity. The worms cover the surface of the burrow with these mucous lumps, strengthening its walls, so such burrows remain in the soil for a long time.

And insect larvae have special formations on the limbs, head, and sometimes on the back, with which they act like a shovel. For example, in mole crickets, the front legs are turned into strong digging tools - they are expanded, with jagged edges. These scrapers are capable of loosening even very dry soil. In larvae

Khrushchev, which digs passages to a considerable depth, uses the upper jaws as a tool for loosening, which have the form of triangular pyramids with a jagged top and with powerful ridges on the sides. The larva hits the soil lump with these jaws, breaks it into small particles and scoops them up under itself. Other large soil inhabitants live in existing cavities. They are distinguished, as a rule, by a very flexible thin body and can penetrate very narrow and winding passages. Digging activity animals is of great importance to the soil. The system of passages improves its aeration, which favors the growth of roots and the development of aerobic microbial processes associated with humification and mineralization of organic material. It is not for nothing that Charles Darwin wrote that long before man invented the plow, earthworms learned to cultivate the soil correctly and well. He dedicated a special book to them, “The Formation of the Soil Layer by Earthworms and Observations on the Lifestyle of the latter.”

Main role soil organisms is the ability to quickly process plant residues, manure, household waste, turning them into high-quality natural organic fertilizer vermicompost. In many countries, including ours, they have learned to breed worms on special farms to produce organic fertilizers. The following examples will help to evaluate the contribution of the invisible workers of the soil in shaping its structure. Thus, ants building soil nests throw more than a ton of soil per 1 hectare to the surface from deep layers of soil. In 8-10 years they process almost the entire horizon populated by them. And desert woodlice lift from a depth of 50-80 cm to the surface soil enriched with elements of mineral nutrition for plants. Where the colonies of these woodlice are located, the vegetation is taller and denser. Earthworms are capable of processing up to 110 tons of earth per 1 hectare per year.

Moving in the ground and feeding on dead plant debris, animals mix organic and mineral soil particles. By dragging ground litter into deep layers, they thereby improve the aeration of these layers and promote the activation of microbial processes, which leads to the enrichment of the soil with humus and nutrients. It is animals who, through their activities, create the humus horizon and soil structure.

The role of earthworms in the biological life of the soil

Earthworms loosen the soil, penetrating, unlike other soil organisms that can live only in one soil layer, into different layers of soil. Air and water penetrate through the holes made by the worms to the roots of the plants.

Earthworms help enrich the soil with oxygen, which prevents the processes of decay of organic material

: Earthworms absorb organic residues, along with which mineral particles, grains of clay, soil algae, bacteria, and microorganisms enter the digestive tract. There, this heterogeneous material is mixed and processed, thanks to metabolic processes, supplemented by secretions of the intestinal microflora of the worm, acquiring a new state, and then enters the soil in the form of droppings. This qualitatively improves the composition of the soil and gives it a sticky, lumpy structure.

Man learned to cultivate the soil, fertilize it and obtain high yields. Does this replace the activities of soil organisms? To some extent, yes. But with intensive land use using modern methods, when the soil is overloaded with chemicals (mineral fertilizers, pesticides, growth stimulants), with frequent disturbances of its surface layer and its compaction by agricultural machines, deep disturbances of natural processes occur, which lead to gradual soil degradation and a decrease in its fertility. Excessive amounts of mineral fertilizers poison the earth and kill its biological life. Chemical treatments destroy not only pests in the soil, but also beneficial animals. This damage takes years to repair. Today, during the period of greening our thinking, it is worth thinking about what criteria to evaluate the damage caused to the crop. Until now, it was customary to count only losses from pests. But let's also count the losses caused to the soil itself from the death of soil formers.

To preserve the soil, this unique natural resource of the Earth, capable of self-restoring its fertility, it is necessary, first of all, to preserve its animal world. Soil organisms and soil formers do what humans with their powerful technology cannot yet do. They need a stable environment. They need oxygen in the system of passages made and a supply of organic residues, shelters and passages that are not disturbed by humans. Reasonable farming, gentle methods of soil cultivation and maximum avoidance of chemical plant protection products mean the creation of conditions for preserving the living bioworld of the soil - the key to its fertility.

Nutrients in the soil

Plants can obtain all the components necessary for life from the soil only in mineral form. Nutrients that are rich in organic matter, humus and organic fertilizers can be absorbed by plants only after the process of decomposition of organic compounds or their mineralization is completed.

The presence of sufficient nutrients in the soil is one of the main factors for the successful development of plants. Plants build their aboveground part, root system, flowers, fruits and seeds from organic substances: fats, proteins, carbohydrates, acids and other substances produced by the green leafy mass of plants. To synthesize organic substances, plants need ten main elements, which are called biogenic. Biogenic chemical elements are constantly included in the composition of organisms and perform certain biological functions that ensure the viability of organisms. Biogenic macroelements include carbon (C), calcium (Ca), iron (Fe), hydrogen (H), potassium (K), magnesium (Mg), nitrogen (N), oxygen (O), phosphorus (P), sulfur (S). The plant receives some of these elements from the air, for example oxygen and carbon; it receives hydrogen from the decomposition of water during the process of photosynthesis.

Nutrient metabolism process

Nutrients play a vital role in the cyclical process of metabolism, ensuring the life of plants. Water dissolves nutrients and trace elements, creating a soil solution that is absorbed by plant roots. Solar energy helps transform nutrients through the process of photosynthesis, which, in turn, depends on the presence in plant tissue of a number of trace elements involved in the formation of the colored substance chlorophyll

Instead, the remaining elements come to the plant exclusively from the soil in the form of compounds dissolved in water, the so-called soil solution. If there is a serious deficiency of any of the elements in the soil, the plant weakens and develops only to a certain stage until it exhausts its internal biological reserve of this element existing in the plant tissues. After this stage, the plant may die. In addition to biogenic macroelements, plant development requires microelements, which are usually contained in very small quantities, but nevertheless play an important role in metabolic processes. Microelements include: aluminum (A1), boron (B), cobalt(Co), copper (Cu), manganese (Mn), molybdenum Mo), sodium (Na), silicon (Si), zinc (Zn). Hei - residue or excess of microelements leads to To metabolic disorders, which leads to

entails a lag in the growth and development of the plant, a decrease in yield and other consequences. Some of the listed microelements are not vital and are often classified by researchers into the group of so-called “useful elements.” Nevertheless, their presence is required for the full development of the plant. All components must be present in the plant’s nutrition in a balanced form, since the absence of at least one of the main elements, such as nitrogen, phosphorus, potassium or calcium, inevitably entails insufficiency or inability for the plant to absorb the other three elements, as well as other nutrients . That is why the presence of all elements is so important for the plant to fully absorb the entire nutritional complex.

The ability of plants to absorb nutrients from the environment is determined by the quality and volume of the root system. Plants absorb nutrients throughout the growing season, but unevenly. The need of plants for nutrients changes during different periods of development. During the period of intensive growth, plants especially need nitrogen; during flowering and fruiting, the need for phosphorus and potassium increases. Assimilated nutrients are selectively fixed in various plant organs.

Green plants

Different groups of plants determine the unequal course of the biological cycle. Lower plants have a short life span and, therefore, determine the rapid circulation of elements in the biological cycle . Higher plants have a developed root system, providing a large area of ​​contact between the organism and the soil. The cycle takes place within one year in herbaceous vegetation and over several years (tens, hundreds, thousands) in woody vegetation. At the same time, different elements are not retained by plant organisms for the same amount of time. In nature, a combination of the considered groups of plants is often observed. The following groups are distinguished:

lichen-moss formations occupy the tundra and swamps;

tree formations are taiga and deciduous forests, humid subtropical forests and tropical (rain) forests;

The group of transitional woody-herbaceous formations includes xerophytic forests; this group of plants is typical of forest-steppe and savanna;

the group of herbaceous formations includes upland and swampy meadows, prairies, temperate steppes, subtropical shrub steppes;

The desert formation is in turn divided into subboreal, subtropical, and tropical.

Each formation is characterized by its own special composition and properties of organic matter, processes of decomposition of organic matter. The biomass of each plant formation also has its own differences, which is reflected in the composition of soil organic matter.

Seaweed distributed in all soils, in their surface layer. Diatoms, blue-green and green algae are common in the soil. Their number depends on soil moisture. They are all autotrophs. They synthesize organic matter through photosynthesis. Algae, when they die, enrich the soil with organic matter that is easily decomposed by microorganisms. Participate in rock weathering processes.

Microorganisms participate in the transformation of organic residues, turning them either into humus or destroying organic matter into final products, while complex organic compounds decompose into mineral salts accessible to vegetation . Bacteria They assimilate atmospheric nitrogen and supply it to higher plants, synthesize complex organic compounds, building their bodies from them. They participate in redox processes in the soil, changing the degree of oxidation of various organic and mineral compounds. Thus, almost all links in the soil-forming process are associated with the vital activity of microorganisms. Microorganisms carry out all these processes with the help of enzymes.

Mushrooms- These are saprophytic heterotrophic organisms. It is impossible not to note the important role of fungi, which develop better in soils with low pH values. These organisms have a wide range of hydrolytic enzymes, through which they decompose all types of organic substances. In particular, they decompose compounds resistant to hydrolysis and oxidation such as lignin, phenols, quinones, aromatic hydrocarbons, waxes

The role of worms in soil formation is great, as well as mammals living in the soil, making passages in the soil with a diameter of several millimeters to 4 to 12 cm, mixing the soil to different depths, mainly to a depth of 1 meter, secreting enzymes, organic acids, increasing the biomass of the soil when dying.

What is soil?

Soil is the top fertile layer of the earth's crust.

How are soils different from rocks?

The soils are fertile. The soil may have a different composition, but the rock is constant. Soil contains solid, liquid and gaseous particles.

What is humus formed from?

Humus is formed from dead living organisms and their parts (annual grasses, fallen leaves, dead animals)

Why do you fertilize the soil?

The soil is fertilized in order to increase its fertility.

Compare the structure of podzolic soil and chernozem soil. Find similarities and differences.

Questions and tasks

1. What parts are included in the soil?

Soil consists of solid, liquid and gaseous parts. The solid part of the soil is particles of destroyed rocks and humus mixed with each other. Sand and clay particles are the inorganic part of the soil, and humus is the organic matter. The liquid part of the soil is water with organic and inorganic substances dissolved in it. The gaseous part is soil air.

2. What conditions influence the formation of soils?

Soil formation depends on many conditions: rock composition, climate, surface and groundwater, vegetation, animals.

3. What is the role of climate and living organisms in the formation of soils?

Climate is related to more than just providing the soil with heat and water. The rate of weathering of rocks and the formation of humus, the nature of vegetation and animal life depend on it. Soils are very closely related to living organisms. Dying plants and their parts turn into humus with the help of microorganisms. Soil animals dig up and mix the soil. The role of earthworms is especially important.

4. On what properties of the soil does its natural fertility depend? How can you increase soil fertility?

Soil fertility is determined by their properties: the content of humus, moisture, air, as well as the composition of soil-forming rocks. Soil fertility can be increased using various agricultural techniques: loosening, moistening, and fertilizing.

5. What structure do soils have? Why is the upper soil horizon called humus?

In the soil, humus and transition horizons and parent rock are distinguished. The top layer of the horizon is called humus, because it consists of humus - dead particles of plants and animals.

6. Based on Figure 203, tell us about the differences between podzolic soils and chernozems.

Podzolic and chernozem soils in their structure have humus, transitional horizons, and parent rock. Unlike podzolic soil, chernozem has a thick humus horizon, so the transition horizon lies much lower.

7. Why is soil called an invaluable natural resource?

Soil is an invaluable gift of nature, since it has a unique property - fertility. This property of the soil gives life to vegetation. Vegetation is the main producer of energy. The soil “feeds” all living organisms. It is a habitat for some.

Soil formation is a complex natural process of soil formation from rock under the influence of soil-forming factors within the Earth's biogeosphere.

Soil formation is an important link in the process of geological and biological circulation of matter and energy. Geological cycle is the process of transferring substances from land to ocean and back. Biological cycle is a set of processes of exchange of matter and energy between soil, parent rock, atmosphere and biota.

Soil formation is a specific biosphere process, as a result of which the soil acquires a number of specific characteristics that are absent in the parent soil-forming rock and distinguish the soil from all other components of the biosphere. Among the most significant characteristics of this kind is the presence of specific organic matter in the soil - soil humus And biophilic elements.

Biophilic elements are elements that living organisms absorb from the geochemical environment and use them in life support processes. These include: macroelements - N, C, O, H, Ca, Mg, Na, K, P, S, Cl, Si, Fe and microelements - Cu, Co, Mn, Zn, V, Ni, Mo, Sr, B, Se, F, Br, I. As a result of soil formation, the soil acquires a specific structure. The soil profile is a system horizons

, more or less parallel to the daytime surface, the formation of which is determined by soil formation mechanisms.

Main factors of soil formation

The soil-forming process occurs under the influence of natural conditions external to the soil - soil-forming factors. Soil formation factors should be divided into two types: natural (natural) and anthropogenic (artificial).

Natural (natural) factors.

There are six natural soil formation factors:

1. parent or soil-forming rocks;

2. climate;

3. relief;

4. plants and living organisms;

5. gravity

All natural factors are equivalent. Each of them has its own specific effect on soil formation, and without the participation of any of them, soil formation is impossible. Soil-forming rock is the basis from which soil is formed. The mineral part in the vast majority of soils makes up 90–95% of the soil mass. Highlight parent rock in soil formation: formation of the composition of soil masses and underlying rock. The composition of rocks determines the chemical, mineralogical, granulometric composition of future soils (Fig. 2.2.), for example, the richest soils are formed on carbonate loams, and on sands they are poorer, but warmer and better aerated. The rock also largely determines the rate of soil formation. The source rocks on the territory of Russia are mostly represented by Quaternary sedimentary mixed rocks.

Figure 2.2. Functions and role of soil-forming rock in soil formation.

Climatic factor determines the supply of soil formation with moisture (precipitation) and energy (solar radiation - light and heat). The climate at different latitudes of the globe is different. There are arctic, subarctic, temperate, subtropical and tropical climates. In accordance with climatic conditions, plant zones are distinguished, differing in the amount of plant organic matter, and, accordingly, in the speed and duration of the biological cycle and the type of soil formation process. Favorable for life hydrothermal conditions ensure the flow of processes in the soil, influence communities of plant and animal organisms, increasing their productivity, which ultimately affects the intensity of soil formation. It is known that when the temperature increases by 10 o C, the rate of chemical reactions increases by 2–4 times (van’t Hoff’s rule) (Table 2.1.).

Table 2.1. Sums of active temperatures in different geographical zones

*Sum of active temperatures is an indicator characterizing the amount of heat and expressed as the sum of average daily air or soil temperatures exceeding a certain threshold: 0, 5, 10 o C or the biological minimum temperature required for plant development. For example, the heat requirement of some crops: spring wheat 1200–1700; oats –1000÷1600; millet – 1410÷1950; buckwheat – 1200÷1400; corn – 1100÷2900; potatoes – 1200÷1800.

The water regime of geographical zones is determined by the ratio of the average annual precipitation to annual evaporation - the so-called humidification coefficient (HC) G.N. Vysotsky-N.N. Ivanova. It is the most objective indicator of atmospheric humidification. At KU >1, the moisture is excessive (observed in high latitudes - approximately north and south of the 50th parallel), and at KU<1 – недостаточное увлажнение (например, в пустынях КУ практически приближается к нулю).

Relief determined by the nature of the alternation of low and high land areas. There are three types of relief: microrelief (fluctuations in heights up to several meters); mesorelief (elevation fluctuations up to several tens of meters); macrorelief (height fluctuations from several tens to several hundred meters). The influence of relief is associated with the amount of light, heat and moisture reaching the soil surface. The degree of illumination and heating of soils is affected by the angle of the relief, the exposure of the slope, and the steepness (there is more heat on the southern slope than on the northern). The relief redistributes water received from the atmosphere. Most of the water flows into the low-lying part of the relief. All elevations on the ground are positive elements of the relief; they have the least amount of moisture. Usually there is a coarse mechanical rock (boulders, stone, gravel) on top, and a finer and finer material (loams, forests) below. Positive elements of the relief do not participate in soil formation processes through groundwater, but negative elements do. Relief influences climatic conditions, and accordingly the life of plants, animals, microorganisms, the redistribution of heat and moisture, which affects soil formation processes in general. In addition, the relief determines the movement of soil masses along the slope as a result of erosion and accumulative processes.

Functions plant and living organisms in soil formation are very diverse. Soil formation is a biogenic process, and it begins with the appearance of plants and living organisms on massive crystalline or sedimentary rocks. Plant and living organisms are the only source of organic matter, which serves as material for the formation of soil humus. Another important function of organisms is based on the ability of living matter to selectively absorb elements from soils. Thanks to this property, organisms largely determine the chemical composition of soils. In Fig. 2.2. plant and living organisms are represented, without whose participation the soil-forming process is impossible.

Green lower and higher plants use the radiation energy of the Sun in the process of growth, involving a huge amount of chemical elements in the biological cycle, annually forming about 233 billion tons of organic matter on the surface and inside the soil. Plant roots purely mechanically loosen the soil, increasing the water and air permeability of rocks, and change the properties of parent rocks with their secretions, which promotes the development of microorganisms.

Microorganisms, due to the enzymes they secrete, decompose organic matter and form organo-mineral compounds - humus. According to E.N. Mishustina (1987) the number of microorganisms ranges from several hundred in 1 g of soddy-podzolic soils to 3 billion in chernozem soils. The mass of microorganisms can range from 3 to 8 t/ha in chernozem soils.

Fungi decompose fiber, lignin and other organic matter in the soil and also contribute to the formation of humus.

Earthworms (live at depths of up to 12 m), making passages in the soil, loosen and aerate it, which promotes the development of the root system of plants; in addition, by processing organic residues, they form humus. In one year, worms living on 1 hectare are capable of processing up to 100 tons of organic residues and mixing ~120 tons of soil.

Insects and animals also actively destroy organic matter, mineralize it and, thus, act as intermediaries in the exchange between the soil and the atmosphere, ensuring the cycle of nutrients.

Earth's gravity. A.A. Rode and V.N. Smirnov consider the Earth’s gravitational field to be a factor that determines the downward process of movement of liquid and solid substances.

Time. The age of soils is calculated from the beginning of the soil-forming process. Soil is a natural, constantly changing natural body. It is believed that the form that all soils existing on Earth have today represents only one of the stages in a long and continuous chain of their evolution, and individual current soil formations in the past represented other forms and in the future may undergo significant transformations even without drastic changes. changes in external conditions.

Distinguish absolute And relative age soil Absolute age of soils They call the period of time that has passed from the moment the soil appeared to the current stage of its development. The soil arose when the parent rock came to the surface and began to undergo soil formation processes. For example, in Northern Europe, the process of modern soil formation began to develop after the end of the last ice age.

However, within different parts of the land that were simultaneously freed from water or glacial cover, soils will not always have the same stage of development at any given moment. The reason for this may be differences in the composition of soil-forming rocks, relief, vegetation and other circumstances. Relative age of soils call the difference in the stages of soil development on one common territory that has the same absolute age.

The development time of a mature soil profile for different conditions ranges from several hundred to several thousand years. (According to L. Aleksandrovsky’s data, an increase in the thickness of the humus horizon to 15 cm occurs in approximately 100 years). The age of the territory in general and the soil in particular, as well as changes in the conditions of soil formation in the process of their evolution, have a significant impact on the structure, properties and composition of the soil. Under similar geographical conditions of soil formation, soils of different ages and histories can differ significantly and belong to different classification groups.

So, we can state that all natural factors of soil formation are interconnected and act simultaneously, influencing not only the intensity of the biological cycle and soil formation, but also each other. Thus, changes in microclimatic conditions can cause a change in vegetation cover and soils. Soils, in turn, can affect vegetation change and change microclimatic conditions

Anthropogenic (artificial) factors. The influence of human economic activity on soil formation is manifested in the regulation of the composition and nature of vegetation, changes in the properties of the soils themselves and the processes occurring in them. In vast forest and agricultural areas, mechanized soil cultivation is carried out, during which natural vegetation is destroyed, forests are exploited, reclamation work is carried out, and organic, bacterial and mineral fertilizers are applied. The natural physical and chemical properties of soils change, the directions of soil formation processes that are undesirable for humans are suspended, and the biological properties change. With an increase, for example, in the calcium content (liming), more organic matter becomes in the soil, the reaction of the environment changes, and the number of microorganisms and nutrients increases; as a result, soil fertility increases. Drainage stops the swamp process, and irrigation in dry areas creates conditions for the accumulation of organic matter in soils, increasing soil fertility and plant yields.

As a result of human economic activity, the nature and intensity of the biological cycle of substances change, soils additionally receive organic matter and nutrients, a powerful arable horizon is formed, and cultivated soils with increased fertility are created. Various economic activities cover 500 million hectares of land. However, the use of incorrect farming techniques causes the development of unfavorable soil-forming processes: waterlogging, salinization, destruction of organic matter and loss of nutrients.