It plays an important role in soil formation. The main factors of soil formation. Vegetation as a factor in soil formation

The soil as a special natural body is formed as a result of the close interaction of the following factors - climate, vegetation, soil-forming rocks, terrain and the age of the country (time). Combinations of soil formation factors are combinations of environmental conditions for the development of the soil-forming process and soils.

Climate as a factor in soil formation

Atmospheric climate is understood as the average state of the atmosphere of a particular territory (the globe, continents, countries, regions, regions, etc.), characterized by average indicators of meteorological elements (temperature, precipitation, air humidity, etc.) and their extreme indicators that give the amplitude of fluctuations during the day, seasons and the whole year.

The main source of energy for biological and soil processes is solar radiation, and the main source of moisture is precipitation. Solar radiation is absorbed by the earth's surface, and then gradually radiated and heats the atmosphere. The moisture of precipitation, getting into the soil, is absorbed by plants and returned to the atmosphere through transpiration or as a result of physical evaporation. The basis for identifying the main thermal groups of climates are the sums of average daily temperatures above 10 ° C during the growing season.

According to the conditions of moistening by precipitation during soil research, six main groups of climates are distinguished.

The criterion for such a division is the ratio of precipitation to evapotranspiration *, called the humidification coefficient.

An important role in the formation of soils is played by the distribution of precipitation by the seasons of the year, the intensity of precipitation, which determines their wetting and eroding power, the relative humidity of the air and the strength of the wind, also by season. All these phenomena affect many features of biological and soil processes and determine the development of water and wind erosion of soils.

The climate has a direct and indirect effect on soil formation. The direct influence is manifested in the direct impact of climate elements (moistening of the soil with moisture from precipitation and its wetting, heating and cooling, etc.). Indirect influence is manifested through the impact of climate on flora and fauna.

* Evaporation - evaporation from the open water surface, mm.

Relief as a factor of soil formation

The characteristic of the relief is based on the study of its genesis (tectonic, suffusion, glacial-accumulative, glacial-erosion, eolian forms, etc.) and forms (geomorphology). There are three groups of landforms: macrorelief, mesorelief and microrelief.

The macrorelief is understood as the largest landforms that determine the general appearance of a large territory: plains, plateaus, mountain systems. The emergence of macrorelief is associated mainly with tectonic phenomena in the earth's crust.

Mesorelief - forms of relief of medium size: ridges, hills, hollows, valleys, terraces and their elements - flat areas, slopes of different steepness.

Microrelief is understood as small landforms occupying insignificant areas (from a few square decimeters to several hundred square meters), with fluctuations in relative heights within one meter. These include hillocks, depressions, depressions that occur on even terrain surfaces due to subsidence, permafrost deformations, or other causes.

The relief appears as main factor redistribution of solar radiation and precipitation depending on the exposure and steepness of the slopes and affects the water, thermal, nutrient, redox and salt regimes.

At present, according to the position in the relief and the redistribution of precipitation determined by it, the following groups of soils are distinguished, which are called moistening rows.

Automorphic soils - are formed on flat surfaces and slopes in conditions of free runoff of surface water, with a deep occurrence of groundwater (deeper than 6 m).

Semi-hydromorphic soils - are formed during short-term stagnation of surface water or when groundwater occurs at a depth of 3--6 m (the capillary border can reach the roots of plants).

Hydromorphic soils - are formed under conditions of prolonged surface stagnation of water or when groundwater occurs at a depth of less than 3 m (the capillary border can reach the soil surface).

The relief has a great influence on the development of erosion processes. Under the conditions of slope relief forms, the manifestation of water erosion, i.e., washout and erosion of the soil, is possible.

Soil-forming rocks as a factor in soil formation

Soil-forming rocks are characterized by their origin, composition, structure and properties.

The soil-forming rock is the material basis of the soil and transfers to it its mechanical, mineralogical and chemical composition, as well as physical and Chemical properties, which subsequently gradually change to varying degrees under the influence of the soil-forming process.

The properties and composition of parent rocks affect the composition of the settling vegetation, its productivity, the rate of decomposition of organic residues, the quality of the resulting humus, the features of the interaction of organic substances with minerals, and other aspects of the soil-forming process.

Soil-forming rocks influence the direction and speed of the soil-forming process.

Biological factor of soil formation

The biological factor of soil formation is understood as the diverse participation of living organisms and their metabolic products in the soil formation process.

Soil age

The process of soil formation proceeds in time. Each new cycle of soil formation (seasonal, annual, long-term) introduces certain changes in the transformation of organic and mineral substances in the soil profile. Distinguish between the concept of absolute and relative age of soils.

Absolute age is the time elapsed from the beginning of soil formation to the present. It ranges from a few years to millions of years. The soils of tropical territories that have not undergone various kinds of disturbances (water erosion, deflation, etc.) have the greatest age.

The youngest soils are developed in the modern floodplain. As noted above, over a long period of their development, soils go from the initial (“young”) phase to mature soil. At the same time, they can change in their properties and characteristics due to changes in natural conditions (climate, vegetation, hydrological conditions). In this regard, relict features can be preserved in the soil profile.

Relative age characterizes the rate of the soil-forming process, the rate of change from one stage of soil development to another. It is associated with the influence of the composition and properties of rocks, relief conditions on the speed and direction of the soil-forming process.

Human production activity

Production activity a person is a specific powerful factor influencing the soil (cultivation, fertilizers, melioration, etc.) and the entire complex of environmental conditions for the development of the soil-forming process (vegetation, climate elements, hydrology). This is a factor of conscious, directed impact on the soil, causing a change in its properties and regimes (reactions during liming, nutrient regime when fertilizing, water-air and redox regimes during drainage and irrigation reclamation, etc.) at a much faster pace, what happens under the influence of natural soil formation.

The relationship of soil formation factors

Soil formation factors have a specific effect on soil formation and cannot be replaced by each other. In this sense, they are equivalent. There are two main cycles in the development of natural ecosystems, landscapes and soils - bioclimatic and biogeomorphological.

The bioclimatic cycle of development is determined by cosmic and planetary phenomena, the distribution of solar radiation on the surface of the planet, and the dynamics of the atmosphere; vegetation and soils in this cycle evolve with the climate.

The biogeomorphological cycle of development is determined by geological, geomorphological and geochemical processes; in it, the development of vegetation and soil cover is associated with the formation of relief and surface deposits.

The task 2 Factors of soil formation of solonetzes

Solonetzes are introzonal soils.

Soils are called solonetzes, containing in the absorbed state a large amount of exchangeable sodium, and sometimes magnesium in the illuvial horizon (B). They have a sharp profile differentiation. Solonetzes, like solonchaks, belong to the category of saline soils, however, unlike solonchaks, they contain water-soluble salts not in the uppermost horizon, but at a certain depth.

There are several theories regarding the origin of salt licks. Common to them is the recognition of the leading role of the sodium ion in the development of unfavorable solonetzic properties.

According to the colloid-chemical theory of K. K. Gedroits, solonetzes were formed during the settlement of solonchaks, saline with neutral sodium salts.

In soils containing a large amount of sodium salts, conditions are created for saturation of the absorbing complex with sodium ions by displacing other cations from it. Soil particles saturated with sodium lose their state of aggregation due to high hydration of the sodium ion. Sodium-enriched colloids have the ability to retain water on their surface, swell strongly, become resistant to coagulation, and become highly mobile. With a high content of the sodium ion, the solubility of organic and mineral compounds of the soil also sharply increases as a result of the appearance of an alkaline reaction. This reaction is formed due to the hydrolysis of minerals and the exchange reaction between sodium in the absorbing complex and calcium carbonate salts of the soil solution:

[PPK -] + Ca (HCO 3) 2 - [PPK -] Ca 2+ + 2NaHCO 3.

Alkalinization of the solution promotes further dispersion of soil colloids. Due to their high mobility, they are leached from the upper horizon and, at a certain depth, under the action of electrolyte salts, they turn from a sol-like state into gels and accumulate, which leads to the formation of an illuvial (alkaline) horizon.

K-K. Gedroits distinguishes two stages in the development of solonetzic soils: the first is the salinization of soils by neutral sodium salts, i.e. the formation of solonchaks, and the second - the resettlement of solonchaks and the development of solonetzic soils with their characteristic profile structure and properties. Gedroits identified three phases in the stage of settlement of solonchaks: removal of soluble salts; the formation of soda; dispersion of soil particles and their removal down the profile.

Close views on the genesis of solonetzes were developed by K. D. Glinka, who believed that for the formation of these soils, the processes of soil salinization with sodium salts and their settlement are alternately necessary. Glinka wrote that the alternation of these processes, which has been going on for centuries, leads to the formation of solonetzes.

Subsequent studies (E. N. Ivanova, 1932) found that solonetzes during the settlement of solonchaks can be formed only if the ratio of Na + : (Ca 2+ + Mg 2+) in the salt composition of the solonchak is ?4.

IN natural conditions such a ratio of salts in the soil solution is very rare. During the resettlement of solonchaks saline with neutral salts, which contain more than 20% of calcium salts, solonetzic properties do not appear. Thus, the theory of the formation of solonetzes from solonchaks saline with neutral salts cannot be recognized as universal.

The biological theory of the formation of solonetzes was developed by V. R. Williams, who believed that the source of sodium salts is steppe and semi-desert vegetation - wormwood, saltwort, camphor, kermek, etc. When plant residues are mineralized, a large amount of salts, including soda, is formed.

The enrichment of soils with easily soluble salts leads to the saturation of the absorbing complex with sodium, and the non-saline soil gradually turns into solonetz.

This soil has a densely merged texture and is sharply differentiated. This indicates low soil fertility, and no yield.

V.V. Dokuchaev laid the foundation for the study of soil formation factors. He was the first to establish that soil formation is closely related to the physical and geographical environment.

V.V. Dokuchaev identified five factors of soil formation - climate, soil-forming rocks, living and dead organisms, age and terrain. In modern soil science, human economic activity and groundwater are added to the listed factors. When studying soils, it is important to take into account the mutual relationships and influence of all factors of soil formation.

The functional dependence of soil on soil formation factors can be shown by a schematic formula:

Soil \u003d f (K + P + O + R + HD + HW) t,

where f is a function; K - climate; P - breed; O - organisms; P - relief;
XD - economic activity; GW - groundwater; t is time.

The functional relationship between soil and soil formation factors is so complex that the solution of the above formula is not yet possible. However, V.V. Dokuchaev pointed out that these difficulties are temporary and there is every reason to expect that complex relationships between the soil and the factors that form it will be found. At present, the basis for such a conclusion is, firstly, the increasing pace of obtaining quantitative (digital) data on various conditions and, secondly, the widespread computerization and use mathematical methods studying massive digital data.

Soil-forming rocks

Soil-forming rocks. The rocks on which they form are called soil-forming or parent. The most common are loose sedimentary rocks. They are of Pleistocene (Quaternary) age. They cover 90% of the territory of the extratropical part of the northern hemisphere. Sedimentary rocks are characterized by loose structure, porosity, water permeability and other properties favorable for soil formation. Their thickness can reach more than a hundred meters.

There are the following genetic types sedimentary rocks: eluvial, deluvial, alluvial, moraine, water-glacial, lacustrine-glacial, eolian, etc.

The parent rock is the material basis, the substrate on which the soil is formed. The soil largely inherits from the original rock its granulometric, mineralogical, chemical composition and properties. However, the soil-forming rock is not the skeleton of the soil, inert to the processes developing in it. It consists of a variety of mineral components that are involved in the process of soil formation in various ways. Among them are particles that are practically inert to chemical processes, but playing an important role in the formation of the physical properties of the soil. Other constituents of soil-forming rocks are easily destroyed and enrich the soil with certain chemical elements, thus, the composition and structure of soil-forming rocks has an extremely strong influence on the process of soil formation.

So, for example, soils are usually formed in coniferous-deciduous (mixed) forests. However, when soil-forming rocks within the forest zone contain an increased amount of calcium carbonates, soils are formed that differ sharply from soddy-podzolic soils. But in landscapes where loess-like deposits are located, containing an increased amount of calcium carbonates, peculiar soddy-calcareous soils are formed, which differ sharply appearance and properties from . Thus, the carbonate content of the rock is essential, on which soils with good physicochemical properties can form. The best soil-forming rocks are loesses and loess-like loams, as well as carbonate rocks- they form relatively fertile soils.

Relief is one of the most important factors in soil formation. Affects soil formation mainly indirectly by redistributing water, heat and soil solids. The influence of the relief affects mainly the redistribution of heat and water that enter the land surface. A significant change in the height of the terrain entails a significant change in temperature conditions, relatively minor change height affects the redistribution of precipitation, the exposure of the slope is of great importance for the redistribution of solar energy, determines the degree of impact on the soil of groundwater.

The role and significance of macro-, meso- and microrelief differ markedly. With the forms of macrorelief (plains, mountains, lowlands), a change in the amount of precipitation may be associated with the spread of air masses that bring them. This creates conditions for a gradual change in vegetation types, and hence soils. In the mountains, when the height of the terrain changes, the air temperature and the nature of moisture change, which determines the vertical zonality of the climate, vegetation, and soils.

Mesorelief elements (hills, ridges, watersheds, ravines) redistribute solar energy and precipitation over a limited area. In the flat areas of the relief, almost all atmospheric precipitation is perceived by the soil; slopes lose water due to runoff, and in depressions it can accumulate excessively, causing waterlogging.

There is a significant difference in the insolation of the southern and northern slopes - up to 10°C, which affects the water regime and the nature of the vegetation.

Negative and positive relief elements located nearby, as a rule, have a different water-air and food regime, and an unequal reaction (pH).

Surface and internal runoff causes a directed migration of solid particles (dissolved substances) - the exchange of substances between the forms of meso- and microrelief is established. As a result, the thickness of the humus horizon on the slope can be 2–3 times less than in the depression. A strong runoff of water from steep slopes causes, creates difficult conditions for the settlement of plants.

Forms of microrelief (small depressions, bumps, hillocks) contribute to the emergence of differences in the habitat of plants, the formation of the microstructure of the vegetation cover and a wide variety of soil combinations and complexes.

Depending on the position in the relief and the degree of moisture, automorphic (soils of watersheds, slopes), semi-hydromorphic (waterlogged) and hydromorphic soils are distinguished. The last two groups (rows) of soils are in conjugated dependence on automorphic soils, that is, the soils of depressions are affected by surface and ground waters enriched with chemical elements and compounds extracted from soils located above. The geochemical dependence of semi- and hydromorphic soils on automorphic ones is called geochemical conjugation.

The geochemical relationship under mesorelief conditions is unilateral.

Under microrelief conditions, this relationship has a two-way direction - chemical elements migrating with surface runoff into microdepressions enrich them. However, the drying up of microhighs causes capillary pulling up of soil waters from depressions - some part of the elements is also pulled up.

Climate. The climate has a great influence on the development of soil-forming processes. It is associated with providing the soil with energy (heat) and water. They determine the hydrothermal regime of the soil.

The development of the soil-forming process depends on the annual amount of incoming heat and moisture, the features of their daily and seasonal distribution. The water and thermal regimes of the soil directly affect the development and diversity of organisms, the magnitude of their biomass, the rate and nature of the decomposition of organic matter, the formation of humus, and the destruction of the mineral part of the soil. So, in a dry hot climate, a large amount of humus does not accumulate in the soil - a small amount of litter is formed, its organic matter quickly mineralizes. In arid regions, during the absence of precipitation, there is a slowdown in biological and physico-chemical processes. A different picture is observed in a cold, boreal climate - here there is a slow decomposition of litter and even peat can form. The presence of a frosty period causes freezing of the soil, the cessation of biological and a sharp depression of physical and chemical processes.

The hydrothermal regime also determines the speed and direction of the processes of movement of water-soluble salts along the profile. Thus, in conditions of a moderately cold humid climate, a significant removal of organic and mineral compounds into the lower part of the soil profile or into groundwater occurs. The processes of salt movement in a hot dry climate are different - water rises through capillaries from the lower layers, which can cause soil salinization.

The movement of air masses (wind) affects the gas exchange of the soil and captures small soil particles in the form of dust. Wind causes the process of physical weathering of rocks. It blows out clay and silt particles from the soil surface, sands it, and causes erosion. Wind can also contribute to soil salinization by carrying salts from the surface of saline water basins.
The climate affects the soil not only directly, but also indirectly, influencing biological processes (the distribution of higher plants, the intensity of microbiological activity).

The climatic conditions of the globe naturally change from the equator to the poles, and in mountainous countries - from the foot to the top. In the same direction, a regular change is experienced by the composition of vegetation and animals. Interconnected changes in such important factors of soil formation affect the distribution of the main types of soils. It should be emphasized that the influence of climate elements, like all other factors of soil formation, is manifested only in interaction with other factors. So, for example, in the conditions of the high-mountainous alpine zone, the amount of precipitation is approximately the same as in the conditions of the taiga zone, however, the same amount of precipitation in the first and second cases does not determine the same type of soil: mountain-meadow soils are developed in the alpine zone, and podzolic soils are developed in the taiga zone. soil, due to the significant difference in many factors of soil formation.

Water. Soils are formed under the influence of surface and ground waters. Their role is reduced mainly to the movement of turbulent substances, dissolved compounds under the influence of gravitational and capillary forces, the hydrolysis of soil minerals; when water stagnates, gley processes develop.

have a certain effect on soil formation. groundwater. Water is the medium in which numerous chemical and biological processes take place in the soil. For most of the soils in the interfluve areas, the main source of water is atmospheric precipitation. However, where groundwater is shallow, it has a strong effect on soil formation. Under their influence, the water and air regimes of soils change. Groundwater enriches soils with chemical compounds that they contain, in some cases causing salinization. Waterlogged soils contain an insufficient amount of oxygen, which leads to the suppression of the activity of certain groups of microorganisms. As a result of the impact of groundwater, special soils are formed.

biological factor. It is the leader in the process of soil formation. Its development became possible only after the emergence of life. Without life there would be no soil. Soil formation on Earth began only after the appearance of life. Any rock, no matter how deeply decomposed and weathered it may be, will not yet be soil. Only long-term interaction of parent breeds with plant and animal organisms in certain climatic conditions creates specific qualities distinguishing soil from rocks.

The following groups of organisms are involved in soil formation: microorganisms, green plants and animals. Acting together, they form complex biocenoses. However, each of these groups performs specific functions.

Thanks to the activities microorganisms there is a decomposition of organic residues and the synthesis of the elements contained in them into compounds absorbed by plants. Microorganisms include bacteria, actinomycetes, fungi, algae and protozoa. Their number in 1 g of soil ranges from millions to billions of individuals. The mass of microorganisms is from 3 to 8 t/ha, or about 1–2 t/ha of dry matter. There are especially many microorganisms in the upper horizons of the soil, in the root zone. Microorganisms are the pioneers of soil formation, they are the first to settle on the material rock.

bacteria- the most common group of microorganisms in the soil. Carry out various processes of transformation of organic and mineral compounds. Thanks to their activities, a grandiose process of processing a colossal amount of dead organic matter that enters the soil every year. In this case, the release of chemical elements that were firmly associated with organic matter.

Of great importance is the activity of heterotrophs, which determine the process of ammonification - the decomposition of organic matter with the formation of ammonium forms of nitrogen. Nitrification is also useful - the activity of autotrophic aerobic bacteria that oxidize ammonium nitrogen first to nitrogenous, and then to nitric acid. As a result of this, plants receive such an essential nutrient as nitrogen. In one year of activity of nitrifying bacteria, up to 300 kg of nitric acid salts per 1 ha of soil can be formed.

At the same time, in soil with a lack of oxygen, denitrification can occur - the reduction of soil nitrates to molecular nitrogen, which leads to its loss by the soil.

Certain groups of bacteria are able to absorb molecular nitrogen from the air and convert it into a protein form. This ability is possessed by free-living in the soil and nodule bacteria that live in symbiosis with leguminous plants. After the death of nitrogen-fixing bacteria, the soil is enriched with biological nitrogen - up to 200 kg/ha.

With the help of bacteria, the processes of oxidation of various substances are carried out. So, sulfur bacteria oxidize hydrogen sulfide to sulfuric acid - as a result, up to 200 kg / ha of sulfates accumulate in the soil per year.

A large group of iron bacteria use the energy of ferrous iron oxidation to absorb carbon.

actinomycetes, or radiant fungi, decompose fiber, lignin, humus substances of the soil, participate in the formation of humus.

Mushrooms. Their content is measured in tens of thousands of copies in one gram of soil. Mold fungi are the most common, and in forest soils - mucor fungus. Mushrooms decompose lignin, fiber, proteins, tannins. This produces organic acids that can convert soil minerals. Often, fungi enter into symbiosis with green plants, while forming mycorrhiza on the roots, which improves the nitrogen nutrition of plants.

Seaweed develop on the surface of the soil. Their maximum number is observed during wet periods. Diatoms, blue-green algae predominate in forest soils. They enrich the soil with organic matter, actively participate in the weathering of rocks.

Lichens- a complex symbiotic formation of a fungus and algae. They are found everywhere - on the soil, on trees, bare rocks. Destroy rocks by acting on them mechanically and chemically. Lichen organic remains and mineral grains rock are essentially primitive soil for the settlement of higher organisms on it.

higher plants. Green plants play a major role in soil formation. On land, 15,1010 tons of biomass is produced annually, synthesized by green plants through photosynthesis.

Biomass is the total amount of living organic matter in a plant community. The highest biomass in forest communities is 1–4 thousand centners/ha. Herbaceous communities form a smaller biomass. Meadow steppes – 250 c/ha, dry steppes – 100 c/ha, deserts – 43 c/ha. Part of the biomass in the form of root residues and ground litter is returned to the soil. Annually enters the soil (litter, roots): taiga forest - 4-6 t/ha, meadow steppes - about 14 t/ha, agrophytocenosis - 3-8 t/ha. Plants in the course of their life activity synthesize organic matter and in a certain way distribute it in the soil in the form of a root mass, and after the aerial part dies off, in the form of plant litter. The components of the litter after mineralization enter the soil, contributing to the accumulation of humus and the acquisition of a characteristic dark color of the upper soil horizon. In addition, plants accumulate individual chemical elements that are contained in soil-forming rocks in small quantities, but are necessary for the normal life of plants. After the death of plants and the decomposition of their remains, these chemical elements remain in the soil, gradually enriching it.

The second important function of green plants is the concentration of ash elements and nitrogen. Up to 95% of the mass of dry matter of plants is carbon, oxygen, hydrogen and nitrogen. In addition, so-called ash elements (about 5%) - calcium, magnesium, potassium, sodium, sulfur, chlorine, etc. - about 70 chemical elements accumulate in plants. Many chemical elements accumulate in the soil (as part of organic matter) due to biogenic accumulation. It has been established that leguminous plants in their composition accumulate more calcium, magnesium, nitrogen; cereals - phosphorus, silica, i.e. there is selectivity in the absorption of chemical elements.

Forest litter of coniferous species, decomposing, forms a lot of fulvic acids, which contributes to the development of the podzolic process of soil formation. Under meadow herbaceous vegetation, the process of soil formation develops. Mosses are distinguished by high moisture capacity and therefore contribute to the waterlogging of soils.

Higher plants and microorganisms form certain complexes, under the influence of which various types of soils are formed. Each plant formation corresponds to a certain type of soil. For example, under the plant formation of coniferous forests, it will never form, which is formed under the influence of a meadow-steppe grassy formation.

animal organisms(insects, earthworms, small vertebrates, etc.) living in the soil are also involved in soil formation. There are a lot of them in the soil. Their main role is the transformation of soil organic matter. The burrowing activity of soil animals is also important.

The zoomass on Earth is less than the phytomass and amounts to several billion tons. Broad-leaved forests have the largest zoomass - 600–2000 kg/ha, in the tundra - 90 kg/ha.

Earthworms are the most common group of soil animals - there are thousands of them on one hectare - millions of individuals. They make up 90% of the zoomass in taiga and deciduous forests. For a year, 50–380 tons of soil are processed per 1 ha. At the same time, its porosity and physical properties are improved. C. Darwin found that in the conditions of England, on each hectare, worms annually pass 20–26 tons of soil through their body. Ch. Darwin believed that the soil is the result of animal activity, and even recommended calling it animal layer.

Soil insects loosen the soil, process plant residues, enrich the soil with plant matter, mineral nutrients.

Shrews (ground squirrels, moles, mice, etc.) dig through the soil, create holes in the soil, mix the soil, thereby contributing to better aeration and the fastest development of the soil-forming process, and also enrich the organic mass of the soil with the products of their vital activity, change its composition.

A very special factor of soil formation - time. All processes occurring in the soil occur in time. In order for the influence of external conditions to have an effect, so that in accordance with the factors of soil formation the soil is formed, a certain time is required. Since geographic conditions do not remain constant, but change, the evolution of soils over time occurs. Soil age is the length of time the soil has existed. The soil-forming process, like any other, proceeds in time. Each new cycle of soil formation (seasonal, annual, long-term) introduces certain changes in the transformation of mineral and organic substances in the soil. The degree of accumulation of substances in the soil or their leaching can be determined by the duration of these processes. Therefore, the time factor (“age of the country”, according to V.V. Dokuchaev) has a certain significance in the formation and development of soils.

Research has established the duration of individual processes of soil formation. Thus, a certain level of accumulation of humus in the soil is established from 100–600 years. On young mountain moraines, sediments of drained lakes, a sufficiently formed soil is formed in 100–300 years.

Distinguish the concept absolute and relative age soils. Absolute age- this is the time that has passed from the beginning of soil formation to the present stage of its development. It can range from a few thousand to a million years.

The soil-forming process began earlier in those territories that quickly freed themselves from water and ice cover. So, on the territory of Belarus, the soils of its northern part are young (within the boundaries of the last Valdai (Poozersky) glaciation) - their age is about 10–12 thousand years; the soils of the southern territories of the republic have more mature age. At the same time, within the boundaries of the same territory, of the same absolute age, the soil-forming process can proceed at different rates. This is due to the territorial heterogeneity of the soil-forming rock, relief, etc. As a result, soils with different degrees of development of the soil profile are formed - their relative age will be different.
To determine the absolute age of soils and organic matter, the radioactive isotope 14C and its ratio with 12C are used. The half-life of 14C is 5600 years. The 12C isotope is stable. Knowing the radiocarbon activity of humus, it is possible to determine its age within the range of up to 40–50 thousand years.

Human economic activity is a powerful factor influencing the soil, especially in conditions of increasing intensification Agriculture. It differs sharply from all other factors in its effect on the soil. If the influence of natural factors on the soil manifests itself spontaneously, then a person in the process of his economic activity acts on the soil in a directed way, changes it in accordance with its needs. With the development of science and technology, with the development public relations soil use and transformation are intensifying.

Man and his armament with powerful means of influencing environment, including on the soil (fertilizers, machines, drainage, irrigation, chemicalization, etc.) significantly change natural ecological systems.

Land reclamation, deforestation or planting, creation of artificial reservoirs - all this has a corresponding effect on the water regime of the territory, and hence the soil.

The application of mineral and organic fertilizers, liming of acidic soils, peating of sandy and sanding clay soils changes the chemical composition of soils and their properties. Mechanical tillage causes a change in the complex of physical, chemical and biological properties of the soil.

The systematic application of measures to improve the soil leads to their cultivation.

However, the incorrect implementation of certain measures, the irrational use of soils can cause their significant deterioration - lead to waterlogging, erosion, pollution of the soil environment, and a sharp deterioration in chemical and physical properties. Therefore, human impact on the soil must be scientifically substantiated; aimed at increasing its fertility, at the formation of sustainable highly productive agroecosystems.

Over the past decades, it has been established that the interaction of soil formation factors sets in motion huge masses of matter. As a result of the interaction of rocks and living organisms, a regular redistribution of chemical elements occurs, a kind of metabolism. The same takes place in the systems of living organisms - the atmosphere, rocks - precipitated atmospheric water, etc. In the soil, these migration processes are especially intense, since all factors of soil formation are simultaneously involved in them. Initially, it was believed that the movement of chemical elements is carried out in the form of more or less closed circuits. Later it turned out that the movement of matter in the soil is diverse, but open cycles of migration are of primary importance. Migration processes that occur during soil formation, in turn, are included in planetary cycles covering the entire biosphere.

Therefore, it can be concluded that the soil this is a special natural formation, where the processes of cyclic migration of chemical elements on the surface of the land, the exchange of substances between landscape components reach the highest stress. Simultaneously with the energetic redistribution of matter in the soil, solar energy is actively transformed and accumulated..

Soils develop under the influence of well-known factors of soil formation established since the time of V.V. Dokuchaev. These factors interact so closely that with a change in one of them, the effect on the soil of other factors also changes.

Relief - the totality of all forms of the earth's surface. It has an exceptionally great influence on the formation of soil cover. There are positive relief (convex relief forms) and negative (concave relief forms), external and internal. There are groups or categories of relief, such as hilly relief (alternating hills and plains), undulating (flatland alternates with elevated), gently undulating (wide elevations are replaced by wide depressions), flat. There are 3 landforms:

Macrorelief - large forms of the earth's surface, occupying large areas (plains, plateaus, valleys, beams, basins). The influence of macrorelief forms is as follows: regulation of the distribution of atmospheric moisture; change in thermal regime depending on the absolute height; on the plains, as one moves from north to south, the amount of precipitation changes, which creates the condition for a change in vegetation and soils.
· Mesorelief - a combination of medium relief forms with height fluctuations up to 10 m, occupying smaller areas (hills, mounds, ridges).
· Microrelief - small landforms, up to 1 m high, occupy small areas (hummocks, tubercles, hummocks in swamps).
· Nanorelief - areas of relief up to 25 cm high (small hummocks, elevations near tree trunks).

Significance of mesorelief, microrelief and nanorelief forms: redistribution of solar energy and atmospheric precipitation; precipitation flows into depressions, which leads to an uneven distribution of moisture; surface runoff, subsoil runoff.

The relief has a direct and indirect effect on soil formation. Direct determines the level of groundwater (bogging develops in depressions); provides runoff and movement of soil particles. Indirectly affects the temperature, water, air regimes of soils; affects the distribution of vegetation.

Climate is the average state of the atmosphere at a certain point on the globe. It is characterized by the concepts of radiant energy of the sun and the atmosphere.

The radiant energy of the sun is the source of energy for all processes on Earth. Energy costs for soil formation in different climatic conditions differ: in the tundra and desert 1000 - 5000 kcal/cm?; in the forests and steppes of the temperate zone 10,000 - 40,000 kcal / cm?. The main part of the energy is spent on evaporation and transpiration (95 - 99%), the rest - on biological processes.

The atmosphere is the source of precipitation, and there are 3 main factors: temperature, precipitation, wind. Temperature determines the course of all processes, affects the process of humus formation, and the rate of chemical reactions. Moisture (precipitation) seeps through the soil, forms a soil solution, and promotes the redistribution of soil particles and humus along the profile. The wind causes the soil to disperse, blows out soil particles, and transfers them from one place to another. Regulates the temperature and water regime of the soil.

The climate has both direct and indirect effects. Direct - through humidification, heating, cooling. Indirect - by influencing other factors of soil formation. The climate leads to a change in vegetation, and hence soils.

Time is a factor in the existence of any matter, including soil. Speaking of time, allocate the following concepts:

Time of soil formation. The soil is considered formed when it reaches equilibrium with the conditions of the landscape, this process can be completed quickly (20 - 30 years). The complete formation of soils is judged by the severity of the horizon.
Time of existence of soils. It begins after formation and lasts longer in time (maybe millennia). At the same time, its evolution can take place, since the relief, vegetation, climate can change, and all this will be reflected in the soil.
Soil age. It is customary to distinguish between absolute age - the time from the beginning of soil formation to the present and relative age, which characterizes the degree of development of a given soil, the speed of changing stages, so the relative age can be judged by the degree of development of the soil profile.
The rate of soil formation. Scientists calculate the speed according to the soil cover of the mound.

Rocks are the basis of the soil. Their thickness varies from a few centimeters to several meters. They convey to the soils that form on them their properties: morphological (color); chemical (the more difficult chemical composition mountain people, the more complex the composition of the soil and the more nutrients in it); mineralogical (affects the direction of the soil-forming process, promotes the formation of soil structure and the accumulation of humus); physical (sandy mountain ranges contribute to soil washing, clayey - moisture stagnation and the development of the swamping process, determines fertility, mineralogical composition). The granulometric composition affects the formation of the soil profile. On heavy mountain parody, soils heavy in mechanical composition are formed.

Green plants play a leading role in soil formation, they extract ash elements and nitrogen from the rock, synthesize organic matter during photosynthesis, which, together with ash elements, enters the soil and onto the soil through litter and waste. Each plant formation has its own characteristics of transformation and interaction of decay products with the mineral part of the soil, forming a certain type of soil. Microorganisms play the main role in the processes of humification and mineralization of plant residues and humus, in the destruction and neoformation of soil minerals. They have a great influence on the composition of soil air, regulating the ratio between and in it. By releasing hydrolytic and redox enzymes, microorganisms catalyze the processes of splitting proteins, carbohydrates, lignin, lipids, resins, tannins and other complex organic compounds to simple ones, affect oxidation and reduction of organic compounds to simple mineral salts. With their participation, under anaerobic conditions, the processes of gleying, peat accumulation, and solodization proceed.

Soil fauna accelerates the humification of plant residues, and more biologically active substances accumulate in the soil under its influence. In the soil permeated with passages, water permeability and aeration change.

Human activity is a powerful factor influencing the soil in order to increase its fertility, its cultivation, and also simply changes the appearance of the soil cover (extraction and processing of minerals, waste disposal, and so on). This is a factor of conscious, directed impact on the soil, causing a change in its properties and regimes (nutritional regime when fertilizing, water-air and redox regimes during drainage and irrigation melioration, etc.) at a much faster pace than it happens under influence of natural soil formation.

humus soil forest organic

From all of the above, it is clear that the soil-forming process is composed of many particular processes, mutually conditioned and contradictory.

What happens in the soil:

The destruction of mineral and organic substances, both those that were in the parent rock, and those that are introduced into the soil during its existence and development.
The movement of the original substances of the soil and the products of their destruction.
The accumulation of these transportable substances in different parts of the soil due to precipitation from solutions and coagulation.
The formation of new compounds as a result of the interaction of transported substances with each other and with the original substances of the parent rock.
The exchange of substances between the plant and the soil, which determines the continuous transition of organic matter into mineral and mineral into organic.

If these processes last for some time, the soil acquires a certain profile, is divided into horizons, and the stability of each horizon and the degree of its severity is due to the balance of certain compounds. The genetic horizon is something that is constantly changing. The soil-forming process is continuous in time. In its development, it passes through a number of stages, and each stage corresponds to a certain type of soil.

It is easy to conclude that the following factors take part in soil formation.

Rocks. They serve as a source of formation of the mineral part of the soil, as well as a source of energy associated with them (chemical, surface, thermal), which takes part in soil formation. Their composition undoubtedly affects the nature of the soil. The nature and degree of manifestation of the soil-forming process under certain hydrothermal conditions is to a certain extent predetermined by the chemical and mechanical composition of the rocks. However, with the same other factors of soil formation, soils of the same type are formed on different parent rocks, and, conversely, with differences in soil formers, different soils are formed from the same rock.

organisms. The role of vegetation in soil formation is colossal, since dead plants or their parts serve as the main source of soil humus, living plants extract minerals from the soil, concentrate scattered compounds and turn them into the organic matter of their body. Microbes serve as intermediaries between living and dead agents of soil formation. They mineralize organic matter, making it available to plants again. In the absence of microorganisms, decomposition would proceed very slowly. Animals are much less important in the life of the soil, but their activity cannot be ignored either: excavators mix the soil and, making moves in it, facilitate the access of moisture and air there; worms, swallowing the soil and then passing it through the food tract, spewing out, thereby increasing the amount of organic matter in the soil. The soil "population", consisting of ants, snails, mites, spiders, wood lice, centipedes, earthworms and other invertebrates, if we take only the top layer of soil with a thickness of 20-25 cm, varies, depending on conditions, from 3.5 to 38 million individuals per hectare.

Climate- one of the most important factors of soil formation, affecting the whole process both directly and indirectly. It affects the nature and intensity of weathering, which means the creation of one or another type of mineral soil mass. It affects the vital activity of microorganisms, which means the creation of one or another quality and quantity of the organic mass of the soil. It determines to a large extent the moisture and water regime of the soil, that is, it controls the movement of substances and the differentiation of the soil into horizons. Finally, the greater or lesser abundance of vegetation in a given region and the nature of this vegetation depend on the climate.

Relief. The nature of the relief affects soil formation, since the distribution of climates and vegetation depends on the height of the relief forms, the degree of moisture penetration into the soil (or its rolling down the slope) depends on the steepness of the slopes, and the lighting and heating conditions depend on the exposure.

Human consciously and actively interferes in the process of soil formation by irrigating soils or draining them, planting or destroying vegetation, mechanically tilling soils and introducing various fertilizers into them, etc. Special cultivated soils arise on the globe under the influence of man in populated areas.

The soil changes over time, passing through certain stages. Soil formation should be considered a fairly fast process. During the excavation of mounds in the steppe between Izyum and Artyomovsk, it was found that the thickness of the chernozem in the virgin steppe (0.75 m) is twice as much as the thickness under the mounds (0.33-0.40 m). Since the mounds have stood here for about 6 thousand years, it is easy to calculate that the thickness of the chernozem increased by 5-6 mm per century, and the beginning of chernozem formation took place about 12 thousand years ago. At the same time, the rate of formation of one or another type of soil should not be confused with the age of the soil cover of a given locality, which may be the product of a long, regular evolution of the soil cover during previous geological periods.

Acquiring certain features and properties in the process of development, the soil actively reacts to all kinds of external influences, changing them and refracting them in itself. Depending on its color, structure, water permeability, mechanical composition, etc., the soil, despite the abundance of moisture, may remain relatively dry or, conversely, be relatively moist in a dry climate; despite the large amount of heat received, it can remain relatively cold, since, for example, light soils reflect a lot of sunlight, wet soils spend a lot of heat on evaporation, etc. Therefore, speaking about the importance of climate, we must remember that for the process of soil formation what matters is not the atmospheric climate, but the climate of the soil, which, although it always depends on the atmospheric climate, at the same time always differs from it extremely strongly.

For soil formation, the totality of the factors listed above, the whole complex of them, is important. As a result of the interaction and struggle of these factors, the process of soil formation acquires one or another real direction. The essence of the soil-forming process is to resolve the contradictions created by the coexistence and interaction of various factors.

Let us now turn to a concrete analysis of the individual principal types of soils and the conditions most favorable for their formation.

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