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

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

Climate as a factor of soil formation

The atmospheric climate is understood as the average state of the atmosphere of a particular territory (the globe, continents, countries, regions, regions, etc.), characterized by the average indicators of meteorological elements (temperature, precipitation, humidity, etc.) and their extreme indicators that give the amplitudes 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 radiates and heats the atmosphere. The moisture of precipitation, getting into the soil, is absorbed by plants and returns to the atmosphere through transpiration or as a result of physical evaporation. The basis for identifying the main thermal groups of climates is the sum of the average daily temperatures above 10 ° C during the growing season.

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

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

An important role in the formation of soils is played by the distribution of precipitation by seasons, the intensity of precipitation, which determines their wetting and erosion force, the relative humidity of the air and the strength of the wind also by seasons. 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 impact on soil formation. The direct influence is reflected in the direct influence of the climate elements (soil moistening with precipitation moisture and its wetting, heating and cooling, etc.). Indirect influence is manifested through the influence of climate on flora and fauna.

* Evaporation - evaporation from an 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-erosional, aeolian forms, etc.) and forms (geomorphology). There are three groups of relief forms: macro-relief, mesorelief and micro-relief.

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

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

Microrelief is understood as small landforms that occupy insignificant areas (from several square decimeters to several hundred square meters), with fluctuations in relative heights within one meter. These include hillocks, depressions, depressions arising on flat relief surfaces due to subsidence phenomena, permafrost deformations, or other reasons.

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

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

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

Semihydromorphic soils - are formed during a 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. In the conditions of slope relief forms, the manifestation of water erosion is possible, i.e. soil washout and erosion.

Parent rocks as a factor in soil formation

Parent rocks are characterized by their origin, composition, structure and properties.

The parent 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 affect 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 products of their vital activity in the soil formation process.

Soil age

The process of soil formation takes place over time. Each new cycle of soil formation (seasonal, annual, perennial) introduces certain changes in the conversion of organic and mineral substances in the soil profile. Distinguish between the concept of absolute and relative soil age.

Absolute age is the time elapsed from the beginning of soil formation to the present. It ranges from several years to millions of years. The soils of tropical territories that have not undergone various kinds of disturbances (water erosion, deflation, etc.) are of 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 in connection with changes in natural conditions (climate, vegetation, hydrological conditions). In this regard, relict features may persist in the soil profile.

Relative age characterizes the rate of the soil-forming process, the rate at which one stage of soil development changes 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 man is a specific powerful factor of influence on the soil (cultivation, fertilizers, reclamation, etc.) and on the entire range of environmental conditions for the development of the soil-forming process (vegetation, climate elements, hydrology). This is a factor of conscious, targeted impact on the soil, causing a change in its properties and regimes (reactions during liming, nutrient regime when applying fertilizer, water-air and redox regimes during drainage and irrigation reclamation, etc.) at a much faster pace, than it happens under the influence of natural soil formation.

Interrelation of soil formation factors

Soil formation factors have a specific effect on soil formation and cannot be substituted for 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 planet's surface and the dynamics of the atmosphere; vegetation and soils in this cycle evolve with the climate.

The biogeomorphological development cycle 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 sediments.

The task 2 Factors of soil formation of solonetzes

Saline soils are introzonal soils.

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

There are several theories on the origin of solonetzes. Common to them is the recognition of the leading role of the sodium ion in the development of unfavorable saline properties.

According to the colloidal-chemical theory of K.K. Gedroyts, salt licks were formed during the dispersal of salt marshes salted 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. Colloids enriched with sodium have the ability to retain water on their surface, swell strongly, acquire coagulation resistance and significant mobility. With a high content of 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 as a result of the hydrolysis of minerals and the exchange reaction between the sodium in the absorbing complex and the calcium of the carbonate salts of the soil solution:

[AUC -] + Ca (HCO 3) 2 - [AUC -] 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 some depth under the action of electrolyte salts from the ash-like state they turn into gels, accumulate, which leads to the formation of an illuvial (solonetz) horizon.

K-K. Gedroyc distinguishes two stages in the development of alkaline soils: the first is soil salinization with neutral sodium salts, i.e. the formation of saline soils, and the second - the dispersal of saline soils and the development of solonetz soils with their characteristic profile structure and properties. In the stage of dispersal of saline soils, Gedroyts distinguished three phases: removal of soluble salts; soda formation; dispersing soil particles and carrying them down the profile.

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

Subsequent studies (E.N. Ivanova, 1932) established that solonetzes during the dispersal of saline soils can form only if the Na +: (Ca 2+ + Mg 2+) ratio in the salt composition of the salt marshes is equal to 4.

IN natural conditions such a ratio of salts in a soil solution is very rare. When settling saline soils saline with neutral salts, which contain more than 20% calcium salts, solonetz properties are not manifested. Thus, the theory of the formation of solonetzes from saline soils saline with neutral salts cannot be recognized as universal.

The biological theory of the formation of salt licks was developed by VR Williams, who believed that the source of sodium salts is steppe and semi-desert vegetation - wormwood, saltwort, camphorosma, kermek, etc. During the mineralization of plant residues, a large amount of salts is formed, including soda.

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

This soil has a densely drained constitution and is sharply differentiated. This indicates low soil fertility, and not productivity.

V.V. Dokuchaev laid the foundation for the doctrine of the factors of soil formation. 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, parent 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 the soil on the factors of soil formation can be shown by the schematic formula:

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

where f is a function; K - climate; P - breed; O - organisms; Р - relief;
HD - 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. Currently, the basis for such a conclusion is, firstly, the growing pace of obtaining quantitative (digital) data on in various conditions and, secondly, widespread computerization and the use of mathematical methods for studying mass digital data.

Parent rocks

Parent rocks... The rocks on which they form are called parent or parent rocks. 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 a loose constitution, porosity, water permeability and other properties favorable for soil formation. Their power can reach more than a hundred meters.

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

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

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

Relief belongs to the most important factors of soil formation. Influences soil formation mainly indirectly, redistributing water, heat and solid soil particles. 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 atmospheric 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 micro-relief is markedly different. The forms of macro-relief (plains, mountains, lowlands) may be associated with a change in the amount of precipitation as the air masses that bring them spread. This creates conditions for a gradual change in the types of vegetation, and hence the soil. In the mountains, when the altitude of the terrain changes, the air temperature and the nature of moisture change, which determines the vertical zoning of the climate, vegetation and soils.

Elements of the mesorelief (hills, ridges, watersheds, ravines) redistribute solar energy and precipitation in a limited area. On flat areas of the relief, almost all atmospheric precipitation is absorbed by the soil; slopes lose water due to runoff, and in depressions it can accumulate unnecessarily, causing waterlogging.

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

Negative and positive elements of the relief, which are nearby, have, as a rule, different water-air and food regimes, unequal reaction (pH).

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

The forms of microrelief (small depressions, hummocks, 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 (swampy) and hydromorphic soils are distinguished. The last two groups (rows) of soils are in conjugate dependence on automorphic soils, that is, the soils of depressions are affected by surface and ground waters enriched in chemical elements and compounds extracted from the soils of the above-located areas. The geochemical dependence of semi- and hydromorphic soils on automorphic soils is called geochemical coupling.

The geochemical relationship in the mesorelief conditions has a one-way direction.

Under microrelief conditions, this bond has a two-way direction - chemical elements migrating with the surface runoff into microdepressions enrich them. But the desiccation of microhighs causes capillary pulling up of soil water from depressions - some of the elements are 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. It is they who 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 characteristics of their daily and seasonal distribution. The water and thermal regimes of the soil directly affect the development and diversity of organisms, the value of their biomass, the rate and nature of 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 is quickly mineralized. In arid regions, during the absence of precipitation, a slowdown in biological and physicochemical processes is observed. A different picture is observed in a cold, boreal climate - there is a slow decomposition of litter and even peat can form. The presence of a frosty period determines the freezing of the soil, the cessation of biological and a sharp suppression of physicochemical processes.

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

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

The climatic conditions of the globe change naturally from the equator to the poles, and in mountainous countries - from the bottom to the top. In the same direction, the composition of vegetation and animals undergoes a regular change. Interrelated changes in such important factors of soil formation affect the distribution of the main soil types. It should be emphasized that the influence of climate elements, as well as of all other factors of soil formation, is manifested only in interaction with other factors. So, for example, in the conditions of the alpine alpine zone, the amount of precipitation is approximately the same as in the taiga zone, however, the same amount of precipitation in the first and second cases does not determine the same type of soil: mountain meadows 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... Soil formation occurs under the influence of surface and ground waters. Their role is reduced mainly to the movement of turbid substances, dissolved compounds under the influence of gravitational and capillary forces, hydrolysis of soil minerals; with stagnant water, gley and processes develop.

A certain influence on soil formation is exerted by groundwater... Water is a medium in which numerous chemical and biological processes in the soil take place. For most of the soils in the interfluve areas, precipitation is the main source of water. However, where groundwater is shallow, it has a strong impact 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, cause salinization. Waterlogged soils contain insufficient oxygen, which suppresses the activity of some groups of microorganisms. As a result of the impact of groundwater, special soils are formed.

Biological factor... It is leading 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 rocks with plant and animal organisms in certain climatic conditions creates specific qualitiesdistinguishing soil from rocks.

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

Through activities microorganisms 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 soil horizons, in the root zone. Microorganisms are pioneers of soil formation, they are the first to settle on a material rock.

Bacteria - the most common group of microorganisms in the soil. They 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 is carried out organic matter, which enters the soil annually. In this case, the release of chemical elements that were firmly associated with organic matter occurs.

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, oxidizing ammonium nitrogen, first to nitrogenous, and then to nitric acid... As a result of this, plants receive such a nutrient they need as nitrogen. For one year of activity of nitrifying bacteria, up to 300 kg of nitric acid salts can be formed per 1 ha of soil.

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

Certain groups of bacteria are capable of absorbing molecular nitrogen from the air and converting it into a protein form. This ability is possessed by free-living in the soil and nodule bacteria that live in symbiosis with legumes. 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. Thus, sulfur bacteria oxidize hydrogen sulfide to sulfuric acid - as a result, up to 200 kg / ha of sulfates accumulates in the soil per year.

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

Actinomycetes, or radiant mushrooms, decompose cellulose, lignin, humus substances of the soil, participate in the formation of humus.

Mushrooms... Their content is measured in tens of thousands of specimens per gram of soil. The most common fungi are molds, and in forest soils - mucor mushroom. 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 soil surface. Their maximum number is observed during wet periods. In forest soils, diatoms, blue-green algae prevail. They enrich the soil with organic matter and are actively involved in the weathering of rocks.

Lichens - complex symbiotic formation of fungus and algae. They are found everywhere - on the soil, on trees, bare rocks. They destroy rocks by acting on them mechanically and chemically. Organic remains of lichens and mineral grains of rocks are essentially primitive soil for higher organisms to settle 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 largest biomass in forest communities is 1–4 thousand c / ha. Herbaceous communities form less 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 returns to the soil. Every year it 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 process of their life synthesize organic matter and in a certain way distribute it in the soil in the form of a root mass, and after the death of the aboveground part, in the form of plant litter. The constituent parts of 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, which are contained in small amounts in soil-forming rocks, but are necessary for the normal life of plants. After the plants die off and their remains decompose, 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 dry matter mass of plants is carbon, oxygen, hydrogen and nitrogen. In addition, so-called ash elements (about 5%) accumulate in plants - calcium, magnesium, potassium, sodium, sulfur, chlorine, etc. - about 70 chemical elements. Many chemical elements accumulate in the soil (as part of organic matter) due to biogenic accumulation. It has been established that leguminous plants accumulate more calcium, magnesium, nitrogen in their composition; cereals - phosphorus, silica, i.e. there is selectivity in the absorption of chemical elements.

Coniferous forest litter, decomposing, forms many fulvic acids, which contributes to the development of podzolic soil formation. The soil formation process develops under the meadow herbaceous vegetation. Mosses are distinguished by their high moisture content and therefore contribute to 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 vegetation formation of coniferous forests will never form, which is formed under the influence of the meadow-steppe herbaceous formation.

Animal organisms (insects, earthworms, small vertebrates, etc.) that live 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 digging activity of soil animals is also important.

Zoomass on Earth is less than phytomass and amounts to several billion tons. Deciduous forests have the largest zoo mass - 600–2000 kg / ha, in the tundra - 90 kg / ha.

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

Soil insects loosen the soil, process plant residues, enrich the soil with plant matter and mineral nutrition elements.

Diggers (ground squirrels, moles, mice, etc.) dig through the soil, create burrows 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, and change its composition.

A very special factor of soil formation - time... All processes occurring in the soil take place in time. It takes a certain time for the influence of external conditions to affect, in order for the soil to form in accordance with the factors of soil formation. Since the geographical conditions do not remain constant, but change, the evolution of soils takes place in time. Soil age is the length of time the soil has existed. The soil-forming process, like any other, takes place in time. Each new cycle of soil formation (seasonal, annual, perennial) makes 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 VV Dokuchaev) has a certain value in the formation and development of soils.

Studies have established the duration of the course of individual soil formation processes. So, 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 soil. 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. Thus, on the territory of Belarus, the soils of its northern part (within the boundaries of the last Valdai (Poozero) glaciation) are young - 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 parent rock, topography, etc. As a result, soils are formed with varying degrees of soil profile development - their relative age will be different.
To determine the absolute age of soils and organic matter, the 14C radioactive isotope 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 in the range of up to 40-50 thousand years.

Human economic activity is a powerful factor affecting the soil, especially in the context of the growing intensification of 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 directional way, changes it in accordance with their needs. With the development of science and technology, with the development public relations the use of soil and its transformation are intensified.

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

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

The introduction of mineral and organic fertilizers, liming of acidic soils, peat of sandy and sanding of clay soils changes the chemical composition of soils, their properties. Mechanical soil cultivation 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, the development of erosion, soil pollution, a sharp deterioration in chemical and physical properties. Therefore, the 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, there is a natural redistribution of chemical elements, a kind of exchange of matter. The same takes place in the systems of living organisms - 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 became clear that the movement of matter in the soil is diverse, but open migration cycles are of primary importance. Migration processes occurring during soil formation, in turn, are included in planetary cycles that cover the entire biosphere.

Therefore, we can conclude that the soil - it is a special natural formation, where the processes of cyclic migration of chemical elements on the land surface, 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 impact on the soil and other factors changes.

Relief - the totality of all forms of the earth's surface. It has an exceptionally great influence on the formation of the soil cover. Distinguish between 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), wavy (plain alternates with elevated), gently undulating (wide rises are replaced by wide depressions), flat. There are 3 forms of relief:

· Macro-relief - large forms of the earth's surface, occupying large areas (plains, plates, valleys, gullies, hollows). The influence of the 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 atmospheric precipitation changes, which creates a condition for the change of vegetation and soils.
· Mesorelief - a combination of medium forms of relief with fluctuations in height up to 10 m, occupy less significant areas (hills, mounds, ridges).
· Microrelief - small relief forms, up to 1 m high, occupy small areas (hummocks, hillocks, bumps in swamps).
· Nanorelief - areas of relief up to 25 cm high (small bumps, 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, subsurface runoff.

The relief has a direct and indirect effect on soil formation. Direct determines the level of groundwater (waterlogging 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 particular point in the world. It is characterized by the concepts of radiant energy of the sun and atmosphere.

The radiant energy of the sun is a 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?. Most 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, the rate of chemical reactions. Moisture (precipitation) seeps through the soil, forms a soil solution, contributes to the redistribution of soil particles and humus along the profile. The wind causes the scattering of soils, blows away soil particles, transfers 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 therefore soils.

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

· Time of soil formation. The soil is considered formed when it reaches equilibrium with the landscape conditions, this process can occur quickly (20 - 30 years). The complete formation of soils is judged by the severity of the horizon.
· Time of soil existence. It starts after formation and lasts longer in time (maybe millennia). In this case, its evolution can occur, since the relief, vegetation, climate can change, and all this can be reflected on the soil.
· Soil age. It is customary to distinguish between absolute age - the time from the beginning of soil formation to the present time and relative age; the degree of development of a given soil, the rapidity of the stage change, is characterized, therefore, the relative age can be judged by the degree of development of the soil profile.
· The rate of soil formation. Scientists consider the speed along the soil cover of the mound.

Rocks are the basis of the soil. Their thickness is from several centimeters to several meters. They transfer their properties to the soils that are formed on them: morphological (color); chemical (the more complex the chemical composition of the mountain people, the more complex the composition of the soil and the more nutrients in it); mineralogical (influences the direction of the soil-forming process, contributes to the formation of soil structure and the accumulation of humus); physical (sandy mountain fallows contribute to the washing of soils, clayey - stagnation of moisture and the development of the process of waterlogging, determines fertility, mineralogical composition). The particle size distribution affects the formation of the soil profile. On heavy mountain fallows, heavy-textured soils are formed.

Green plants play a leading role in soil formation, they extract ash elements and nitrogen from the rock, synthesize organic matter in the process of photosynthesis, which, together with ash elements through litter and waste, enters the soil and soil. 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 new formation 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 the breakdown of 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 solvation take place.

The soil fauna accelerates the humification of plant residues, and more biologically active substances accumulate in the soil under its influence. In the soil penetrated by 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 (mining and processing of minerals, waste disposal, and so on). This is a factor of conscious, targeted impact on the soil, causing a change in its properties and regimes (nutrient regime when applying fertilizer, water-air and redox regimes during drainage and irrigation reclamation, etc.) at a much faster pace than occurs under the impact of natural soil formation.

humus soil forest organic

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

In the soil occurs:

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.
Movement of the original soil substances and products of their destruction.
The accumulation of these transported substances in different parts of the soil due to precipitation from solutions and coagulation.
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, causing the continuous transition of organic matter into mineral and mineral into organic matter.

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 manifestation is determined by the balance of certain compounds. The genetic horizon is something constantly changing. The soil-forming process is continuous in time. In its development, it goes through a number of stages, and each stage corresponds to a certain type of soil.

It is easy to come to the conclusion that the following factors are involved 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 influences the nature of the soil. The nature and severity of the soil-forming process under various 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 a difference 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 mineral substances from the soil, concentrate scattered compounds and turn them into organic matter in 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 be very slow. Animals are of much lesser importance in the life of the soil, but their activity also cannot be ignored: diggers 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 alimentary tract, spewing out, thereby increasing the amount of organic matter in the soil. The soil "population", consisting of ants, snails, ticks, spiders, woodlice, millipedes, earthworms and other invertebrates, if we take only the topsoil 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 entire 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 soil organic matter. It largely determines the moisture and water regime of the soil, that is, it controls the movement of substances and the differentiation of the soil to the horizons. Finally, more or less richness of a given area with vegetation and the nature of this vegetation depends 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 conditions of lighting and heating depend on the exposure.

Person deliberately and actively intervenes in the process of soil formation by irrigating or draining soils, planting or destroying vegetation, mechanically cultivating soils and introducing various fertilizers into them, etc. On the globe, under the influence of man in populated areas, special cultivated soils arise.

The soil changes over time, passing through certain stages. Soil formation should be considered a fairly rapid process. During excavations of barrows in the steppe between Izyum and Artyomovsk, it was found that the thickness of chernozem in the virgin steppe (0.75 m) is twice as large as the thickness under the barrows (0.33-0.40 m). Since the burial mounds here are about 6 thousand years old, it is easy to calculate that the thickness of 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 a particular type of soil should not be confused with the age of the soil cover in a given area, which may be the product of a long-term regular evolution of the soil cover during the previous geological periods.

Acquiring known features and properties in the process of development, the soil actively reacts to all external influences, changing them and refracting in itself. Depending on its color, structure, water permeability, texture, 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, moist 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 it is not the atmospheric climate that matters, but the soil climate, which, although always depends on the atmospheric climate, at the same time is always extremely different from it.

The totality of the above factors, their entire complex, is important for soil formation. As a result of the interaction and struggle of these factors, the process of soil formation takes on 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 specific analysis of the individual main types of soils and the conditions most favorable to their occurrence.

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