Natural area soil types humus content. The main types of soils in Russia, their brief description. Soil as a habitat for living organisms

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THE SOIL- the most superficial layer of land on the globe, resulting from changes in rocks under the influence of living and dead organisms (vegetation, animals, microorganisms), solar heat and precipitation. The soil is a very special natural formation, having only its inherent structure, composition and properties. The most important property of the soil is its fertility, i.e. ability to ensure the growth and development of plants. In order to be fertile, the soil must have a sufficient amount of nutrients and a supply of water necessary for plant nutrition, it is precisely in its fertility that the soil, as a natural body, differs from all other natural bodies (for example, a barren stone), which are not able to meet the needs of plants in the simultaneous and the joint presence of two factors of their existence - water and minerals.

Soil is the most important component of all terrestrial biocenoses and the biosphere of the Earth as a whole, through the soil cover of the Earth there are numerous ecological connections of all organisms living on earth and in the earth (including humans) with the lithosphere, hydrosphere and atmosphere.

The role of the soil in the human economy is enormous. The study of soils is necessary not only for agricultural purposes, but also for the development of forestry, engineering and construction. Knowledge of soil properties is necessary to solve a number of health problems, exploration and mining, organization of green areas in urban areas, environmental monitoring, etc.

Soil science: history, relationship with other sciences.

The science of the origin and development of soils, the patterns of their distribution, the ways of rational use and increasing fertility is called soil science. This science is a branch of natural science and is closely related to the physical, mathematical, chemical, biological, geological and geographical sciences, based on the fundamental laws and research methods developed by them. At the same time, like any other theoretical science, soil science develops on the basis of direct interaction with practice, which checks and uses the revealed patterns and, in turn, stimulates new searches in the field of theoretical knowledge. To date, large applied sections of soil science have been formed for agriculture and forestry, irrigation, construction, transport, mineral exploration, public health and environmental protection.

From the moment of the systematic occupation of agriculture, mankind first empirically, and then with the help of scientific methods, studied the soil. The most ancient attempts to evaluate various soils are known in China (3 thousand BC) and Ancient Egypt. In ancient Greece, the concept of soil developed in the course of the development of ancient natural-philosophical natural science. During the period of the Roman Empire, a large number of empirical observations on the properties of the soil were accumulated and some agronomic methods of its cultivation were developed.

The long period of the Middle Ages was characterized by stagnation in the field of natural science, but at the end of it (with the beginning of the disintegration of the feudal system), interest in the study of soils reappeared in connection with the problem of plant nutrition. A number of works of that time reflected the opinion that plants feed on water, creating chemical compounds from water and air, and the soil serves them only as a mechanical support. However, by the end of the 18th century. this theory was replaced by the humus theory of Albrecht Thayer, according to which plants can only feed on soil organic matter and water. Thayer was one of the founders of agronomy and the organizer of the first higher agronomic educational institution.

In the first half of the 19th century The famous German chemist Justus Liebig developed the mineral theory of plant nutrition, according to which plants absorb minerals from the soil, and only carbon in the form of carbon dioxide from humus. J. Liebig believed that each crop depletes the supply of minerals in the soil, therefore, in order to eliminate this deficiency of elements, it is necessary to introduce into the soil mineral fertilizers factory prepared. Liebig's merit was the introduction into practice Agriculture application of mineral fertilizers.

The value of nitrogen for the soil was studied by the French scientist J.Yu. Bussengo.

By the middle of the 19th century. extensive material has been accumulated on the study of soils, but these data were scattered, not brought into a system and not generalized. There was no single definition of the term soil for all researchers.

The founder of soil science as an independent natural-historical science was the outstanding Russian scientist Vasily Vasilyevich Dokuchaev (1846–1903). Dokuchaev first formulated the scientific definition of soil, calling soil an independent natural-historical body, which is the product of the combined activity of the parent rock, climate, plant and animal organisms, soil age, and partly the terrain. All the factors of soil formation that Dokuchaev spoke of were known before him, they were consistently put forward by various scientists, but always as the only determining condition. Dokuchaev was the first to say that the formation of soil occurs as a result of the combined action of all factors of soil formation. He established the view of the soil as an independent special natural body, equivalent to the concepts of a plant, animal, mineral, etc., which arises, develops, continuously changes in time and space, and in this way he laid a solid foundation for a new science.

Dokuchaev established the principle of the structure of the soil profile, developed the idea of ​​\u200b\u200bthe patterns of spatial distribution certain types soils covering the land surface in the form of horizontal, or latitudinal zones, established vertical zonality, or zonality, in the distribution of soils, which is understood as the regular replacement of some soils by others as they rise from the foot to the top of high mountains. He also owns the first scientific classification of soils, which was based on the entire set the most important features and soil properties. Dokuchaev's classification was recognized by world science and the names he proposed "chernozem", "podzol", "salt marsh", "salt" became international scientific terms. He developed methods for studying the origin and fertility of soils, as well as methods for mapping them, and even in 1899 compiled the first soil map of the northern hemisphere (this map was called the "Scheme of Soil Zones of the Northern Hemisphere").

In addition to Dokuchaev, a great contribution to the development of soil science in our country was made by P.A. Kostychev, V.R. Williams, N.M. Sibirtsev, G.N. Vysotsky, P.S. Kossovich, K.K. Gedroits, K. D. Glinka, S. S. Neustruev, B. B. Polynov, L. I. Prasolov and others.

Thus, the science of soil as an independent natural formation was formed in Russia. Dokuchaev's ideas had a strong influence on the development of soil science in other countries. Many Russian terms have entered the international scientific lexicon (chernozem, podzol, gley, etc.)

Important studies for understanding the processes of soil formation and studying the soils of different territories were carried out by scientists from other countries. This is E.V. Gilgard (USA); E.Ramann, E.Blank, V.I.Kubiena (Germany); A. de Zigmond (Hungary); J. Milne (Great Britain), J. Aubert, R. Menin, J. Durand, N. Lenef, G. Erar, F. Duchaufour (France); J. Prescott, S. Stephens (Australia) and many others.

For the development of theoretical concepts and successful study of the soil cover of our planet, business ties between different national schools are necessary. In 1924 the International Society of Soil Scientists was organized. For a long time, from 1961 to 1981, a large and complex work was carried out to compile the Soil Map of the World, in which Russian scientists played a large role.

Soil study methods.

One of them is comparative geographical, based on the simultaneous study of the soils themselves (their morphological features, physical and chemical properties) and soil formation factors in different geographical conditions with their subsequent comparison. Currently, soil research uses various chemical analyzes, analyzes of physical properties, mineralogical, thermochemical, microbiological and many other analyses. As a result, a certain relationship is established between the change in certain soil properties and the change in soil-forming factors. Knowing the patterns of distribution of soil-forming factors, it is possible to create a soil map for a vast territory. It was in this way that Dokuchaev made the first world soil map in 1899, known as the Schemes of Soil Zones of the Northern Hemisphere.

Another method is the method of stationary studies It consists in the systematic observation of a soil process, which is usually carried out on typical soils with a certain combination of soil-forming factors. Thus, the method of stationary studies refines and details the method of comparative geographical studies. There are two methods for studying soils.

Soil formation.

The process of soil formation.

All rocks covering the surface of the globe, from the very first moments of their formation, under the influence of various processes, began to immediately collapse. The sum of the processes of transformation of rocks on the surface of the Earth is called weathering or hypergenesis. The totality of weathering products is called the weathering crust. The process of transformation of the original rocks into the weathering crust is extremely complex and includes numerous processes and phenomena. Depending on the nature and causes of the destruction of rocks, physical, chemical and biological weathering is distinguished, which usually comes down to the physical and chemical effects of organisms on rocks.

The processes of weathering (hypergenesis) extend to a certain depth, forming a zone of hypergenesis . The lower boundary of this zone is conditionally drawn along the roof of the upper horizon of groundwater (formation) waters. The lower (and larger) part of the hypergenesis zone is occupied by rocks altered to some extent by weathering processes. Here, the latest and ancient weathering crusts formed in more ancient geological periods are distinguished. The surface layer of the hypergenesis zone is the substrate on which soil is formed. How does the process of soil formation take place?

In the process of weathering (hypergenesis), the original appearance of rocks, as well as their elemental and mineral composition, changed. Initially massive (i.e. dense and hard) rocks gradually passed into a fragmented state. Grass, sand, and clay can serve as examples of rocks crushed as a result of weathering. Becoming fragmented, rocks acquired a number of new properties and features: they became more permeable to water and air, the total surface of their particles increased in them, which increased chemical weathering, new compounds were formed, including easily water-soluble compounds and, finally, mountain rocks acquired the ability to retain moisture, which is of great importance for providing plants with water.

However, the weathering processes themselves could not lead to the accumulation of plant food elements in the rock, and, consequently, they could not turn the rock into soil. Easily soluble compounds formed as a result of weathering can only be washed out of rocks under the influence of atmospheric precipitation; and such a biologically important element as nitrogen, consumed by plants in large quantities, is not contained at all in igneous rocks.

Loose and capable of absorbing water, rocks became a favorable environment for the vital activity of bacteria and various plant organisms. Gradually, the upper layer of the weathering crust was enriched with the products of vital activity of organisms and their dying remains. The decomposition of organic matter and the presence of oxygen led to complex chemical processes, which resulted in the accumulation of elements of ash and nitrogen food in the rock. Thus, the rocks of the surface layer of the weathering crust (they are also called soil-forming, bedrock or parent rocks) became soil. The composition of the soil, therefore, includes a mineral component corresponding to the composition of bedrocks, and an organic component.

Therefore, the beginning of the process of soil formation should be considered the moment when vegetation and microorganisms settled on the weathering products of rocks. From that moment on, the crushed rock became soil, i.e. a qualitatively new body, possessing a number of qualities and properties, the most significant of which is fertility. In this respect, all existing soils on the globe represent a natural-historical body, the formation and development of which is associated with the development of all organic life on the earth's surface. Once born, the soil-forming process never stopped.

Soil formation factors.

The development of the soil-forming process is most directly influenced by the natural conditions in which it proceeds; its features and the direction in which this process will develop depend on one or another of their combinations.

The most important of these natural conditions, called factors of soil formation, are the following: parent (soil-forming) rocks, vegetation, wildlife and microorganisms, climate, terrain and soil age. To these five main factors of soil formation (which Dokuchaev named) now add the action of water (soil and ground) and human activity. The biological factor always plays a leading role, while the remaining factors are only the background against which the development of soils in nature occurs, but they have a great influence on the nature and direction of the soil-forming process.

Soil-forming rocks.

All existing soils on Earth originated from rocks, so it is obvious that they are directly involved in the process of soil formation. The chemical composition of the rock is of the greatest importance, since the mineral part of any soil contains mainly those elements that were part of the parent rock. The physical properties of the parent rock are also of great importance, since such factors as the granulometric composition of the rock, its density, porosity, and thermal conductivity most directly affect not only the intensity, but also the nature of the ongoing soil-forming processes.

Climate.

The climate plays a huge role in the processes of soil formation, its influence is very diverse. The main meteorological elements that determine the nature and characteristics climatic conditions, are temperature and precipitation. The annual amount of incoming heat and moisture, the peculiarities of their daily and seasonal distribution determine quite definite processes of soil formation. The climate affects the nature of rock weathering, affects the thermal and water regimes of the soil. The movement of air masses (wind) affects the gas exchange of the soil and captures small soil particles in the form of dust. But the climate affects the soil not only directly, but also indirectly, since the existence of this or that vegetation, the habitat of certain animals, as well as the intensity of microbiological activity are determined precisely by climatic conditions.

Vegetation, animals and microorganisms.

Vegetation.

The importance of vegetation in soil formation is extremely high and diverse. Penetrating the upper layer of soil-forming rock with their roots, plants extract nutrients from its lower horizons and fix them in the synthesized organic matter. After the mineralization of dead parts of plants, the ash elements contained in them are deposited in the upper horizon of the soil-forming rock, thereby creating favorable conditions for the nutrition of the next generations of plants. So, as a result of the constant creation and destruction of organic matter in the upper horizons of the soil, the most important property for it is acquired - the accumulation, or concentration of elements of ash and nitrogen food for plants. This phenomenon is called the biological absorption capacity of the soil.

Due to the decomposition of plant residues, humus accumulates in the soil, which is of great importance in soil fertility. Plant residues in the soil are a necessary nutrient substrate and the most important condition for the development of many soil microorganisms.

In the process of decomposition of soil organic matter, acids are released, which, acting on the parent rock, increase its weathering.

The plants themselves, in the course of their life activity, secrete various weak acids with their roots, under the influence of which sparingly soluble mineral compounds partially pass into a soluble, and therefore, into a form assimilated by plants.

In addition, vegetation cover significantly changes microclimatic conditions. For example, in the forest, in comparison with treeless territories, the summer temperature is lowered, the humidity of air and soil is increased, the strength of the wind and the evaporation of water over the soil are reduced, more snow, melt and rain water accumulates - all this inevitably affects the soil formation process.

Microorganisms.

Thanks to the activity of microorganisms inhabiting the soil, organic residues are decomposed and the elements contained in them are synthesized into compounds absorbed by plants.

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, chernozem will never form, which is formed under the influence of a meadow-steppe plant formation.

Animal world.

Animal organisms are important for soil formation, and there are a lot of them in the soil. Invertebrates living in the upper soil horizons and in plant remains on the surface are of the greatest importance. In the course of their life activity, they significantly accelerate the decomposition of organic matter and often produce very profound changes in the chemical and physical properties of the soil. An important role is also played by burrowing animals, such as moles, mice, ground squirrels, marmots, etc. By repeatedly breaking the soil, they contribute to the mixing of organic substances with minerals, as well as increasing the water and air permeability of the soil, which enhances and accelerates the processes of decomposition of organic residues in the soil. . They also enrich the soil mass with the products of their vital activity.

Vegetation serves as food for various herbivores, therefore, before getting into the soil, a significant part of the organic residues undergoes significant processing in the digestive organs of animals.

Relief

has an indirect effect on the formation of soil cover. Its role is reduced mainly to the redistribution of heat and moisture. A significant change in the height of the terrain entails significant changes in temperature conditions (it gets colder with height). The phenomenon of vertical zonality in the mountains is connected with this. Relatively small changes in altitude affect the redistribution of precipitation: low areas, depressions and depressions are always more humid than slopes and elevations. The exposure of the slope determines the amount of solar energy entering the surface: the southern slopes receive more light and heat than the northern ones. Thus, the features of the relief change the nature of the impact of climate on the process of soil formation. It is obvious that soil formation processes will proceed differently under different microclimatic conditions. Of great importance in the formation of the soil cover is also the systematic flushing and redistribution of fine earth particles by atmospheric precipitation and melt water over the elements of relief. The significance of the relief is great in conditions of heavy precipitation: areas deprived of the natural runoff of excess moisture are very often swamped.

Soil age.

Soil is a natural body constant development, and the form that all soils on Earth have today is only one of the stages in a long and continuous chain of their development, and individual current soil formations, in the past, represented other forms and in the future may undergo significant transformations even without drastic changes external conditions.

There are absolute and relative age of soils. The absolute age of soils is the period of time elapsed from the moment the soil appeared to the current stage of its development. The soil arose when the parent rock came to the surface and began to undergo soil formation processes. For example, in Northern Europe, the process of modern soil formation began to develop after the end of the last ice age.

However, within the boundaries of different parts of the land that have simultaneously freed themselves from water or ice cover, soils will by no means always go through the same stage of their development at each given moment. The reason for this may be differences in the composition of soil-forming rocks, in relief, vegetation and other local conditions. The difference in the stages of soil development in one common area with the same absolute age is called the relative age of the soils.

The time of development of a mature soil profile for different conditions is from several hundred to several thousand years. The age of the territory in general and soil in particular, as well as changes in the conditions of soil formation in the process of their development, have a significant impact on the structure, properties and composition of the soil. Under similar geographical conditions of soil formation, soils of different age and history of development can differ significantly and belong to different classification groups.

The age of soils is therefore one of the most important factors to be taken into account when studying a particular soil.

Soil and groundwater.

Water is the medium in which numerous chemical and biological processes take place in the soil. 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 the soil with the chemical compounds it contains, sometimes causing salinization. Waterlogged soils contain an insufficient amount of oxygen, which causes the suppression of the activity of certain groups of microorganisms.

Human economic activity affects some factors of soil formation, for example, vegetation (cutting down forests, replacing it with herbaceous phytocenoses, etc.), and directly on soils through its mechanical processing, irrigation, application of mineral and organic fertilizers, etc. As a result, often soil-forming processes and soil properties change. In connection with the intensification of agriculture, human influence on soil processes is continuously increasing.

The impact of human society on the soil cover is one of the aspects of the general influence of man on environment. Now the problem of destruction of the soil cover as a result of improper agricultural tillage and human construction activities is especially acute. The second most important problem is soil pollution caused by chemicalization of agriculture and industrial and domestic emissions into the environment.

All factors do not affect in isolation, but in close interconnection and interaction with each other. Each of them affects not only the soil, but also each other. In addition, the soil itself in the process of development has a certain influence on all factors of soil formation, causing certain changes in each of them. Thus, due to the inseparable connection between vegetation and soils, any change in vegetation is inevitably accompanied by a change in soils, and, conversely, a change in soils, in particular, their moisture regime, aeration, salt regime, etc. inevitably entails a change in vegetation.

Soil composition.

The soil consists of solid, liquid, gaseous and living parts. Their ratio varies not only in different soils, but also in different horizons of the same soil. A decrease in the content of organic matter and living organisms from the upper soil horizons to the lower ones and an increase in the intensity of the transformation of the components of the parent rock from the lower horizons to the upper ones are regular.

Mineral substances of lithogenic origin predominate in the solid part of the soil. These are fragments and particles of primary minerals of various sizes (quartz, feldspars, hornblende, mica, etc.) formed in the process of weathering of secondary minerals (hydromica, montmorillonite, kaolinite, etc.) and rocks. The sizes of these fragments and particles are varied - from 0.0001 mm to several tens of cm. This variety of sizes determines the friability of the soil. The bulk of the soil is usually fine earth - particles with a diameter of less than 1 mm.

The mineralogical composition of the solid part of the soil largely determines its fertility. The composition of mineral substances includes: Si, Al, Fe, K, Mg, Ca, C, N, P, S, much less microelements: Cu, Mo, I, B, F, Pb, etc. The vast majority of elements are in oxidized form. Many soils, mainly in soils of insufficiently moistened areas, contain a significant amount of calcium carbonate CaCO 3 (especially if the soil was formed on carbonate rock), in the soils of arid regions - CaSO 4 and other more easily soluble salts (chlorites); soils, humid tropical areas are enriched with Fe and Al. However, the realization of these general regularities depends on the composition of parent rocks, the age of soils, topography, climate, and so on.

The composition of the solid part of the soil also includes organic matter. There are two groups of organic substances in the soil: those that have entered the soil in the form of plant and animal residues and new, specific humic substances. substances resulting from the transformation of these residues. There are gradual transitions between these groups of soil organic matter; in accordance with this, the organic compounds contained in the soil are also divided into two groups.

The first group includes compounds contained in large quantities in plant and animal residues, as well as compounds that are waste products of plants, animals and microorganisms. These are proteins, carbohydrates, organic acids, fats, lignin, resins, etc. These compounds in total make up only 10–15% of the total mass of soil organic matter.

The second group of soil organic compounds is represented by complex from humic substances, or humus resulting from complex biochemical reactions from compounds of the first group. Humic substances make up 85–90% of the organic part of the soil; they are represented by complex high-molecular acidic compounds. The main groups of humic substances are humic acids and fulvic acids. . In the elemental composition of humic substances important role play carbon, oxygen, hydrogen, nitrogen and phosphorus. Humus contains the main nutrients of plants, which, under the influence of microorganisms, become available to plants. Humus content in the upper horizon different types soil content varies widely: from 1% in gray-brown desert soils to 12–15% in chernozems. Different types of soils differ in the nature of the change in the amount of humus with depth.

The soil also contains intermediate decomposition products of organic compounds of the first group.

When organic matter decomposes in the soil, the nitrogen contained in them is converted into forms available to plants. Under natural conditions, they are the main source of nitrogen nutrition for plant organisms. Many organic substances are involved in the creation of organo-mineral structural units (lumps). The structure of the soil thus arising largely determines its physical properties, as well as water, air and thermal regimes.

The liquid part of the soil or, as it is also called, the soil solution - this is the water contained in the soil with gases dissolved in it, mineral and organic matter that got into it when passing through the atmosphere and seeping through the soil layer. The composition of soil moisture is determined by the processes of soil formation, vegetation, common features climate, as well as seasons, weather, human activities (fertilization, etc.).

The soil solution plays a huge role in soil formation and plant nutrition. The main chemical and biological processes in the soil can only take place in the presence of free water. Soil water is the medium in which the migration of chemical elements occurs in the process of soil formation, the supply of plants with water and dissolved nutrients.

In non-saline soils, the concentration of substances in the soil solution is low (usually does not exceed 0.1%), and in saline soils (saline and solonetz soils), it is sharply increased (up to whole and even tens of percent). A high content of substances in soil moisture is harmful to plants, because. this makes it difficult for them to receive water and nutrients, causing physiological dryness.

The reaction of the soil solution in soils of different types is not the same: acid reaction (pH 7) - soda solonetzes, neutral or slightly alkaline (pH = 7) - ordinary chernozems, meadow and brown soils. Too acidic and too alkaline soil solution adversely affects the growth and development of plants.

The gaseous part, or soil air, fills the pores of the soil that are not occupied by water. The total volume of soil pores (porosity) ranges from 25 to 60% of the soil volume ( cm. Morphological features of soils). The ratio between soil air and water is determined by the degree of soil moisture.

The composition of soil air, which includes N 2, O 2, CO 2, volatile organic compounds, water vapor, etc., differs significantly from atmospheric air and is determined by the nature of many chemical, biochemical, and biological processes occurring in the soil. The composition of soil air is not constant, depending on external conditions and seasons, it can vary significantly. For example, the amount of carbon dioxide (CO 2 ) in the soil air varies significantly in annual and daily cycles due to different rates of gas release by microorganisms and plant roots.

Between soil and atmospheric air there is a constant gas exchange. The root systems of higher plants and aerobic microorganisms vigorously absorb oxygen and release carbon dioxide. Excess CO 2 from the soil is released into the atmosphere, and atmospheric air enriched with oxygen penetrates into the soil. The gas exchange of the soil with the atmosphere can be hindered either by the dense composition of the soil or by its excessive moisture. In this case, the oxygen content in the soil air sharply decreases, and anaerobic microbiological processes begin to develop, leading to the formation of methane, hydrogen sulfide, ammonia, and some other gases.

Oxygen in the soil is necessary for the respiration of plant roots, so the normal development of plants is possible only under conditions of sufficient air access to the soil. With insufficient penetration of oxygen into the soil, plants are inhibited, slow down their growth, and sometimes die completely.

Oxygen in the soil is also of great importance for the vital activity of soil microorganisms, most of which are aerobes. In the absence of air access, the activity of aerobic bacteria ceases, and in connection with this, the formation of nutrients necessary for plants in the soil also ceases. In addition, under anaerobic conditions, processes occur that lead to the accumulation of compounds harmful to plants in the soil.

Sometimes the composition of soil air may contain some gases that penetrate through the strata of rocks from their places of accumulation; this is the basis for special gas geochemical methods for prospecting for mineral deposits.

The living part of the soil consists of soil microorganisms and soil animals. The active role of living organisms in the formation of soil determines its belonging to bioinert natural bodies - the most important components of the biosphere.

Water and thermal regimes of the soil.

The water regime of the soil is a combination of all phenomena that determine the inflow, movement, consumption and use of soil moisture by plants. Soil water regime – the most important factor in soil formation and soil fertility.

The main sources of soil water are precipitation. A certain amount of water enters the soil as a result of condensation of steam from the air, sometimes closely spaced groundwater plays a significant role. In areas of irrigated agriculture, irrigation is of great importance.

The flow of water is as follows. Part of the water entering the soil surface flows down in the form of surface runoff. The largest amount of moisture entering the soil is absorbed by plants, which then partially evaporate it. Some water is used for evaporation , moreover, part of this moisture is retained by the vegetation cover and evaporates from its surface into the atmosphere, and part evaporates directly from the soil surface. Soil water can also be consumed in the form of subsoil runoff, a temporary phenomenon that occurs during periods of seasonal soil moisture. At this time, gravitational water begins to move along the most permeable soil horizon, the aquiclude for which is a less permeable horizon. Such seasonally existing waters are called perched waters. Finally, a significant part of soil water can reach the surface of groundwater, the outflow of which occurs along an impervious bed-water barrier, and leave as part of the groundwater runoff.

Atmospheric precipitation, melt and irrigation water penetrate the soil due to its water permeability (ability to pass water). The more large (non-capillary) gaps in the soil, the higher its water permeability. Of particular importance is the permeability for the absorption of melt water. If in autumn the soil is frozen in a highly moistened state, then usually its water permeability is extremely low. Under forest vegetation that protects the soil from severe freezing, or in fields with early snow retention, melt water is absorbed well.

depends on the water content in the soil technological processes when tilling the soil, supplying plants with water, physicochemical and microbiological processes that determine the conversion of nutrients in the soil and their entry with water into the plant. Therefore, one of the main tasks of agriculture is to create a water regime in the soil that is favorable for cultivated plants, which is achieved by the accumulation, conservation, rational use of soil moisture, and, if necessary, by irrigation or drainage of land.

The water regime of the soil depends on the properties of the soil itself, climate and weather conditions, the nature of natural plant formations, on cultivated soils - on the characteristics of cultivated crops and the technique of their cultivation.

The following main types of soil water regime are distinguished: leaching, non-leaching, effusion, stagnant and frozen (cryogenic).

Pripromyvny In the type of water regime, the entire soil layer is annually soaked to groundwater, while the soil returns less moisture to the atmosphere than it receives (excess moisture seeps into groundwater). Under the conditions of this regime, the soil-ground stratum is, as it were, annually washed with gravitational water. The leaching type of water regime is typical for a humid temperate and tropical climate, where the amount of precipitation is greater than evaporation.

The non-leaching type of water regime is characterized by the absence of continuous wetting of the soil layer. Atmospheric moisture penetrates the soil to a depth of several decimeters to several meters (usually no more than 4 m), and between the soaked soil layer and the upper boundary of the capillary fringe of groundwater, a horizon with constant low humidity (close to the wilting point) appears, called the dead horizon of drying. . This regime differs in that the amount of moisture returned to the atmosphere is approximately equal to its entry with precipitation. This type of water regime is typical for a dry climate, where the amount of precipitation is always significantly less than evaporation (a conditional value that characterizes the maximum possible evaporation in a given area with an unlimited supply of water). For example, it is characteristic of the steppes and semi-deserts.

effusion the type of water regime is observed in a dry climate with a sharp predominance of evaporation over precipitation, in soils that are fed not only by atmospheric precipitation, but also by the moisture of shallow groundwater. With an effusion type of water regime, groundwater reaches the soil surface and evaporates, which often leads to soil salinization.

The stagnant type of water regime is formed under the influence of the close occurrence of groundwater in a humid climate, in which the amount of precipitation exceeds the sum of evaporation and absorption of water by plants. Due to excessive moisture, perched water is formed, resulting in waterlogging of the soil. This type of water regime is typical for depressions in the relief.

The permafrost (cryogenic) type of water regime is formed on the territory of continuous distribution of permafrost. Its peculiarity is the presence of a permanently frozen aquifer at a shallow depth. As a result, despite the small amount of precipitation, in the warm season, the soil is supersaturated with water.

The thermal regime of the soil is the sum of the phenomena of heat transfer in the system of the surface layer of air - soil - soil-forming rock, its characteristics also include the processes of transfer and accumulation of heat in the soil.

The main source of heat entering the soil is solar radiation. The thermal regime of the soil is determined mainly by the ratio between the absorbed solar radiation and the thermal radiation of the soil. The features of this ratio determine the differences in the regime of different soils. The thermal regime of the soil is formed mainly under the influence of climatic conditions, but it is also influenced by the thermophysical properties of the soil and its underlying rocks (for example, the intensity of absorption of solar energy depends on the color of the soil, the darker the soil, the more solar radiation it absorbs) . Permafrost rocks have a special effect on the thermal regime of the soil.

The thermal energy of the soil is involved in the phase transitions of soil moisture, being released during ice formation and condensation of soil moisture and consumed during ice melting and evaporation.

The thermal regime of the soil has a secular, long-term, annual and daily cyclicity associated with the cyclicity of the receipt of solar radiation energy on the earth's surface. On a long-term average, the annual heat balance of a given soil is zero.

Daily fluctuations in soil temperature cover the thickness of the soil from 20 cm to 1 m, annual fluctuations - up to 10–20 m. soil cooling). The depth of soil freezing rarely exceeds 1–2 m.

Vegetation has a significant influence on the thermal regime of the soil. It delays solar radiation, as a result of which the temperature of the soil in summer can be lower than the air temperature. Forest vegetation has a particularly noticeable effect on the thermal regime of soils.

The thermal regime of the soil largely determines the intensity of mechanical, geochemical and biological processes occurring in the soil. For example, the intensity of the biochemical activity of bacteria increases with an increase in soil temperature to 40–50°C; above this temperature, the vital activity of microorganisms is inhibited. At temperatures below 0 ° C, biological phenomena are sharply slowed down and stop. The thermal regime of the soil has a direct impact on the growth and development of plants. An important indicator The provision of plants with soil heat is the sum of active soil temperatures (i.e. temperatures above 10 ° C, at these temperatures there is an active vegetation of plants) at a depth of the arable layer (20 cm).

Morphological features of soils.

Like any natural body, the soil has a sum of external, so-called morphological features, which are the result of the processes of its formation and therefore reflect the origin (genesis) of soils, the history of their development, their physical and Chemical properties. The main morphological features of the soil are: soil profile, color and color of soils, soil structure, granulometric (mechanical) composition of soils, soil composition, neoplasms and inclusions.

Soil classification.

Each science, as a rule, has a classification of the object of its study, and this classification reflects the level of development of science. Since science is constantly developing, the classification is being improved accordingly.

In the Dodokuchaev period, it was not the soil that was studied (in modern view), but only its individual properties and aspects, and therefore classified the soil according to its individual properties - chemical composition, particle size distribution, etc.

Dokuchaev showed that the soil is a special natural body, which is formed as a result of the interaction of soil formation factors, and established character traits soil morphology (primarily the structure of the soil profile) - this gave him the opportunity to develop a classification of soils on a completely different basis than previously done.

For the main classification unit, Dokuchaev took the genetic types of soils formed by a certain combination of soil formation factors. This genetic classification of soils is based on the structure of the soil profile, which reflects the development of soils and their regimes. The modern classification of soils used in our country is a developed and supplemented by Dokuchaev's classification.

Dokuchaev singled out 10 soil types, and in the supplemented modern classifications there are more than 100 of them.

According to the modern classification used in Russia, one genetic type combines soils with a single profile structure, with a qualitatively similar soil formation process that develops under conditions of the same thermal and water regimes, on parent rocks of a similar composition and under the same type of vegetation. Depending on the moisture content, the soils are combined into rows. A distinction is made between automorphic soils (i.e. soils that receive moisture only from atmospheric precipitation and are not significantly affected by groundwater), hydromorphic soils (i.e. soils that are significantly affected by groundwater), and transitional automorphic soils. -hydromorphic soils.

Soil genetic types are subdivided into subtypes, genera, species, varieties, categories, and they are combined into classes, series, formations, generations, families, associations, etc.

The genetic classification of soils developed in Russia for the First International Soil Congress (1927) was accepted by all national schools and contributed to the elucidation of the main patterns of soil geography.

Currently, a unified international classification of soils has not been developed. A significant number of national soil classifications have been created, some of them (Russia, USA, France) include all the soils of the world.

The second approach to the classification of soils took shape in the 1960s in the United States. The American classification is based not on an assessment of the conditions of formation and related genetic characteristics of various soil types, but on taking into account easily detectable morphological features of soils, primarily on the study of certain horizons of the soil profile. These horizons were called diagnostic .

The diagnostic approach to soil taxonomy turned out to be very convenient for compiling detailed large-scale maps of small areas, but such maps could hardly be compared with survey small-scale maps built on the basis of the principle of geographic and genetic classification.

In the meantime, by the early 1960s, it became clear that a world soil map was needed to determine a strategy for agricultural food production, the legend of which should be based on a classification that eliminated the gap between large-scale and small-scale maps.

Experts from the Food and Agriculture Organization of the United Nations (FAO), together with the United Nations Educational, Scientific and Cultural Organization (UNESCO), have begun to create an International Soil Map of the World. The work on the map lasted more than 20 years, and more than 300 soil scientists from different countries took part in it. The map was created through discussion and agreement between various national scientific schools. As a result, a map legend was developed, which was based on a diagnostic approach to determining the classification units of all levels, although it also took into account individual elements of the geographic and genetic approach. The publication of all 19 sheets of the map was completed in 1981, since then new data have been obtained, certain concepts and formulations in the map legend have been clarified.

Basic regularities of soil geography.

The study of the regularities of the spatial distribution of different types of soils is one of the fundamental problems of the Earth sciences.

The identification of regularities in soil geography became possible only on the basis of V.V. Dokuchaev’s concept of soil as a result of the interaction of soil formation factors, i.e. from the standpoint of genetic soil science. The following main patterns were identified:

Horizontal soil zonality. In large flat areas, soil types that arise under the influence of soil formation conditions typical for a given climate (i.e., automorphic soil types that develop on watersheds, provided that precipitation is the main source of moisture) are located in extensive strips - zones elongated along strips with close atmospheric humidification (in areas with insufficient moisture) and with the same annual sum of temperatures (in areas with sufficient and excessive moisture). Such types of soils Dokuchaev called zonal.

This creates the main regularity of the spatial distribution of soils in the flat areas - horizontal soil zoning. Horizontal soil zonality does not have a planetary distribution; it is typical only for very vast flat areas, for example, the East European Plain, part of Africa, the northern half of North America, Western Siberia, flat spaces of Kazakhstan and Central Asia. As a rule, these horizontal soil zones are located latitudinally (i.e., they are elongated along the parallels), but in some cases, under the influence of the relief, the direction of the horizontal zones changes dramatically. For example, the soil zones of the western part of Australia and the southern half of North America extend along the meridians.

The discovery of horizontal soil zonality was made by Dokuchaev on the basis of the theory of soil formation factors. It was important scientific discovery, on the basis of which the doctrine of natural zones was created .

From the poles to the equator, the following main natural zones replace each other: the polar zone (or the zone of the Arctic and Antarctic deserts), the tundra zone, the forest-tundra zone, the taiga zone, the mixed forest zone, the broad-leaved forest zone, the forest-steppe zone, the steppe zone, the semi-desert zone, the zone deserts, a zone of savannahs and light forests, a zone of variable-moist (including monsoon) forests and a zone of humid evergreen forests. Each of these natural zones is characterized by quite definite types of automorphic soils. For example, on the East European Plain, latitudinal zones of tundra soils, podzolic soils, gray forest soils, chernozems, chestnut soils, and brown desert-steppe soils are clearly expressed.

The ranges of subtypes of zonal soils are also located inside the zones in parallel strips, which makes it possible to distinguish soil subzones. So, the zone of chernozems is subdivided into subzones of leached, typical, ordinary and southern chernozems, the zone of chestnut soils - into dark chestnut, chestnut and light chestnut.

However, the manifestation of zoning is characteristic not only of automorphic soils. It was found that certain zones correspond to certain hydromorphic soils (i.e. soils, the formation of which occurs with a significant influence of groundwater). Hydromorphic soils are not azonal, but their zoning manifests itself differently than in automorphic soils. Hydromorphic soils develop next to automorphic soils and are geochemically associated with them; therefore, a soil zone can be defined as the territory of distribution of a certain type of automorphic soils and hydromorphic soils that are in geochemical conjugation with them, which occupy a significant area, up to 20–25% of the area of ​​soil zones.

Vertical soil zonality. The second pattern of soil geography is vertical zonality, which manifests itself in the change of soil types from the foot of the mountain system to its peaks. With the height of the terrain it becomes colder, which entails natural changes in climatic conditions, flora and fauna. In accordance with this, soil types also change. In mountains with insufficient moisture, the change in vertical belts is due to a change in the degree of moisture, as well as the exposure of slopes (the soil cover here acquires an exposition-differentiated character), and in mountains with sufficient and excessive moisture, it is due to a change in temperature conditions.

At first, it was believed that the change in vertical soil zones was completely analogous to the horizontal zonality of soils from the equator to the poles, but later it was found that among mountain soils, along with types common both on the plains and in the mountains, there are soils that form only in mountainous conditions. landscapes. It was also found that very rarely a strict sequence of vertical soil zones (belts) is observed. Separate vertical soil belts fall out, mix, and sometimes even change places, so it was concluded that the structure of the vertical zones (belts) of a mountainous country is determined by local conditions.

The phenomenon of facies. IP Gerasimov and other scientists found that the manifestation of horizontal zoning is corrected by the conditions of specific regions. Depending on the influence of oceanic basins, continental spaces, and large mountain barriers, local (facies) climate features are formed on the path of the movement of air masses. This is manifested in the formation of features of local soils up to the appearance of special types, as well as in the complication of horizontal soil zonality. Due to the phenomenon of facies, even within the distribution of one soil type, soils can have significant differences.

Intrazonal soil subdivisions are called soil provinces . A soil province is understood as a part of the soil zone, which is distinguished by specific features of subtypes and types of soils and soil formation conditions. Similar provinces of several zones and subzones are combined into facies.

Mosaic of the soil cover. In the process of detailed soil-surveying and soil-cartographic work, it was found that the idea of ​​the homogeneity of the soil cover, i.e. The existence of soil zones, subzones, and provinces is very conditional and corresponds only to the small-scale level of soil research. In fact, under the influence of meso- and microrelief, variability in the composition of parent rocks and vegetation, and the depth of groundwater, the soil cover within zones, subzones, and provinces is a complex mosaic. This soil mosaic consists of varying degrees of genetically related soil areas that form a specific soil cover pattern and structure, all of whose components can only be shown on large-scale or detailed soil maps.

Natalia Novoselova

Literature:

Williams W.R. soil science, 1949
Soils of the USSR. M., Thought, 1979
Glazovskaya M.A., Gennadiev A.N. , Moscow, Moscow State University, 1995
Maksakovskiy V.P. Geographical picture of the world. Part I general characteristics peace. Yaroslavl, Upper Volga book publishing house, 1995
Workshop on General Soil Science. Publishing House of Moscow State University, Moscow, 1995
Dobrovolsky V.V. Geography of soils with the basics of soil science. M., Vlados, 2001
Zavarzin G.A. Lectures on Natural History Microbiology. M., Nauka, 2003
Eastern European forests. History in the Holocene and the present. Book 1. Moscow, Science, 2004



At the core geographic zoning lie climate change, and above all differences in the flow of solar heat. The largest territorial units of the zonal division of the geographical shell - geographic zones.

natural areas - natural complexes occupying large areas, characterized by the dominance of one zonal landscape type. They are formed mainly under the influence of climate - the features of the distribution of heat and moisture, their ratio. Each natural zone has its own type of soil, vegetation and wildlife.

The external appearance of the natural area is determined vegetation type . But the nature of vegetation depends on climatic conditions - thermal conditions, moisture, illumination.

As a rule, natural zones are elongated in the form of wide strips from west to east. There are no clear boundaries between them, the zones gradually move into one another. The latitudinal location of natural zones is disturbed by the uneven distribution of land and ocean, relief, and remoteness from the ocean.

For example, in the temperate latitudes of North America, natural zones are located in the meridional direction, which is associated with the influence of the Cordilleras, which prevent the passage of moist winds from the Pacific Ocean into the interior of the mainland. In Eurasia, there are almost all zones of the Northern Hemisphere, but their width is not the same. For example, the zone of mixed forests gradually narrows from west to east as the distance from the ocean increases and the continentality of the climate increases. In the mountains, natural zones change with height - high-altitudezonation . The altitudinal zonality is due to climate change with uplift. The set of altitudinal belts in the mountains depends on the geographical position of the mountains themselves, which determines the nature of the nature of the lower belt, and the height of the mountains, which determines the nature of the highest altitudinal zone for these mountains. The higher the mountains and the closer they are to the equator, the more altitudinal zones they have.

The location of the altitudinal belts is also affected by the direction of the ridges relative to the sides of the horizon and the prevailing winds. Thus, the southern and northern slopes of the mountains may differ in the number of altitudinal zones. As a rule, there are more of them on the southern slopes than on the northern ones. On slopes exposed to moist winds, the nature of the vegetation will differ from that of the opposite slope.

The sequence of changes in altitudinal belts in the mountains practically coincides with the sequence of changes in natural zones on the plains. But in the mountains, belts change faster. There are natural complexes that are typical only for mountains, for example, subalpine and alpine meadows.

Natural land areas

Evergreen tropical and equatorial forests

Evergreen tropical and equatorial forests are located in the equatorial and tropical zones of South America, Africa and the Eurasian islands. The climate is humid and hot. The air temperature is constantly high. Red-yellow ferralitic soils are formed, rich in iron and aluminum oxides, but poor in nutrients. Dense evergreen forests are the source of a large amount of plant litter. But organic matter entering the soil does not have time to accumulate. They are absorbed by numerous plants, washed out by daily precipitation into the lower soil horizons. The equatorial forests are characterized by multilayered.

The vegetation is represented mainly by woody forms that form multi-tiered communities. Characterized by high species diversity, the presence of epiphytes (ferns, orchids), lianas. Plants have hard leathery leaves with devices that get rid of excess moisture (droppers). Animal world It is represented by a huge variety of forms - consumers of rotting wood and leaf litter, as well as species that live in tree crowns.

Savannahs and woodlands

Natural areas with their characteristic herbaceous vegetation (mainly cereals) in combination with individual trees or their groups and shrub thickets. They are located north and south of the equatorial forest zones of the southern continents in tropical zones. The climate is characterized by the presence of a more or less long dry period and high air temperatures throughout the year. In savannahs, red ferrallitic or red-brown soils are formed, which are richer in humus than in equatorial forests. Although nutrients are washed out of the soil during the wet season, humus accumulates during the dry season.

Herbaceous vegetation with separate groups of trees predominates. Umbrella crowns are characteristic, life forms that allow plants to store moisture (bottle-shaped trunks, succulents) and protect themselves from overheating (pubescence and wax coating on the leaves, the location of the leaves with an edge to the sun's rays). The fauna is characterized by an abundance of herbivores, mainly ungulates, large predators, animals that process plant litter (termites). With distance from the equator in the Northern and Southern Hemispheres, the duration of the dry period in the savannas increases, the vegetation becomes more and more sparse.

Deserts and semi-deserts

Deserts and semi-deserts are located in tropical, subtropical and temperate climatic zones. The desert climate is characterized by extremely low rainfall throughout the year.

The daily amplitudes of air temperature are large. In terms of temperature, they vary quite a lot: from hot tropical deserts to deserts of the temperate climate zone. All deserts are characterized by the development of desert soils, poor in organic matter, but rich in mineral salts. Irrigation allows them to be used for agriculture.

Soil salinization is widespread. The vegetation is sparse and has specific adaptations to an arid climate: the leaves are turned into thorns, the root system greatly exceeds the aerial part, many plants are able to grow on saline soils, bringing salt to the surface of the leaves in the form of plaque. Great variety of succulents. Vegetation is adapted either to "capture" moisture from the air, or to reduce evaporation, or both. The animal world is represented by forms that can do without water for a long time (storage water in the form of fat deposits), travel long distances, survive heat by going into holes or hibernating.

Many animals are nocturnal.

Hard-leaved evergreen forests and shrubs

Natural zones are located in subtropical zones in a Mediterranean climate with dry, hot summers and wet, mild winters. Brown and red-brown soils are formed.

The vegetation cover is represented by coniferous and evergreen forms with leathery leaves covered with a wax coating, pubescence, usually with a high content of essential oils. So the plants adapt to the dry hot summer. The animal world is strongly exterminated; but herbivorous and leaf-eating forms are characteristic, there are many reptiles, birds of prey.

Steppes and forest-steppes

Natural complexes characteristic of temperate zones. Here, in a climate with cold, often snowy winters and warm, dry summers, the most fertile soils, chernozems, are formed. The vegetation is predominantly herbaceous, in typical steppes, prairies and pampas - cereals, in dry variants - sagebrush. Almost everywhere natural vegetation has been replaced by agricultural crops. The animal world is represented by herbivorous forms, among which ungulates are heavily exterminated, mainly rodents and reptiles, which are characterized by a long period of winter dormancy, and birds of prey have survived.

broad-leaved and mixed the woods

Broad-leaved and mixed forests grow in temperate zones in a climate with sufficient moisture and a period of low, sometimes negative temperatures. The soils are fertile, brown forest (under deciduous forests) and gray forest (under mixed forests). Forests, as a rule, are formed by 2-3 species of trees with a shrub layer and a well-developed grass cover. The animal world is diverse, clearly divided into tiers, represented by forest ungulates, predators, rodents, and insectivorous birds.

Taiga

Taiga is distributed in the temperate latitudes of the Northern Hemisphere in a wide strip in climate conditions with short warm summers, long and severe winters, sufficient rainfall and normal, sometimes excessive moisture.

In the taiga zone, under conditions of abundant moisture and relatively cool summers, intensive washing of the soil layer occurs, and little humus is formed. Under it thin layer as a result of washing the soil, a whitish layer is formed, which in appearance is similar to ash. Therefore, such soils are called podzolic. The vegetation is represented by various types of coniferous forests in combination with small-leaved ones.

The tiered structure is well developed, which is also characteristic of the animal world.

Tundra and forest tundra

Distributed in subpolar and polar climatic zones. The climate is harsh, with a short and cold growing season, long and harsh winters. With a small amount of precipitation, excessive moisture develops. The soils are peat-gley, under them there is a layer of permafrost. The vegetation cover is represented mainly by grass-lichen communities, with shrubs and dwarf trees. The fauna is peculiar: large ungulates and predators are common, nomadic and migratory forms are widely represented, especially migratory birds, which spend only the nesting period in the tundra. There are practically no burrowing animals, few grain eaters.

polar deserts

Distributed on islands in high latitudes. The climate of these places is extremely severe, winter and polar night dominate most of the year. Vegetation is sparse, represented by communities of mosses and scale lichens. The animal world is connected with the ocean, there is no permanent population on land.

Altitude zones

They are located in a variety of climatic zones and are characterized by a corresponding set of altitudinal zones. Their number depends on the latitude (in the equatorial and tropical regions it is larger and on the height of the mountain range) the higher, the greater the set of belts.

Table "Natural areas"

Summary of the lesson "Natural areas". Next topic:

For the horizons, a letter designation is adopted, which makes it possible to record the structure of the profile. For example, for sod-podzolic soil: A 0 -A 0 A 1 -A 1 -A 1 A 2 -A 2 -A 2 B-BC-C .

The following types of horizons are distinguished:

• Organogenic- (litter (A 0, O), peat horizon (T), humus horizon (A h, H), sod (A d), humus horizon (A), etc.) - characterized by biogenic accumulation of organic matter.
• Eluvial- (podzolic, glazed, solodized, segregated horizons; denoted by the letter E with indices, or A 2) - characterized by the removal of organic and / or mineral components.
• illuvial- (B with indices) - characterized by the accumulation of matter removed from the eluvial horizons.
• Metamorphic- (B m) - are formed during the transformation of the mineral part of the soil in place.
• Hydrogen storage- (S) - are formed in the zone of maximum accumulation of substances (highly soluble salts, gypsum, carbonates, iron oxides, etc.) brought by groundwater.
• Cow- (K) - horizons cemented by various substances (highly soluble salts, gypsum, carbonates, amorphous silica, iron oxides, etc.).
• gley- (G) - with prevailing reducing conditions.
• Subsoil- parent rock (C) from which the soil was formed, and underlying underlying rock (D) of a different composition.

Soil solids

The soil is highly dispersed and has a large total surface of solid particles: from 3-5 m² / g for sandy soils to 300-400 m² / g for clay soils. Due to the dispersity, the soil has significant porosity: the pore volume can reach from 30% of the total volume in waterlogged mineral soils to 90% in organogenic peat soils. On average, this figure is 40-60%.

The density of the solid phase (ρ s) of mineral soils ranges from 2.4 to 2.8 g / cm³, organogenic: 1.35-1.45 g / cm³. Soil density (ρ b) is lower: 0.8-1.8 g/cm³ and 0.1-0.3 g/cm³, respectively. Porosity (porosity, ε) is related to densities by the formula:

ε = 1 - ρ b /ρ s

The mineral part of the soil

Mineral composition

About 50-60% of the volume and up to 90-97% of the mass of the soil are mineral components. The mineral composition of the soil differs from the composition of the rock on which it was formed: the older the soil, the stronger this difference.

Minerals that are residual material during weathering and soil formation are called primary. In the zone of hypergenesis, most of them are unstable and are destroyed at one rate or another. Olivine, amphiboles, pyroxenes, and nepheline are among the first to be destroyed. More stable are feldspars, which make up up to 10-15% of the mass of the solid phase of the soil. Most often they are represented by relatively large sand particles. Epidote, disthene, garnet, staurolite, zircon, tourmaline are distinguished by high resistance. Their content is usually insignificant, however, it makes it possible to judge the origin of the parent rock and the time of soil formation. The most stable is quartz, which weathers over several million years. Due to this, under conditions of prolonged and intense weathering, accompanied by the removal of mineral destruction products, its relative accumulation occurs.

The soil is characterized by a high content secondary minerals, formed as a result of deep chemical transformation of primary, or synthesized directly in the soil. Particularly important among them is the role of clay minerals - kaolinite, montmorillonite, halloysite, serpentine and a number of others. They have high sorption properties, a large capacity of cation and anion exchange, the ability to swell and retain water, stickiness, etc. These properties largely determine the absorption capacity of soils, its structure and, ultimately, fertility.

The content of minerals-oxides and hydroxides of iron (limonite, hematite), manganese (vernadite, pyrolusite, manganite), aluminum (gibbsite) and others is high, which also strongly affects the properties of the soil - they are involved in the formation of the structure, the soil absorbing complex (especially in heavily weathered tropical soils), take part in redox processes. Carbonates play an important role in soils (calcite, aragonite, see carbonate-calcium balance in soils). In arid regions, readily soluble salts (sodium chloride, sodium carbonate, etc.) often accumulate in the soil, affecting the entire course of the soil-forming process.

Grading

Ferret's triangle

Soils can contain particles with a diameter of less than 0.001 mm, and more than a few centimeters. A smaller particle diameter means a larger specific surface, and this, in turn, means larger values ​​of cation exchange capacity, water-holding capacity, better aggregation, but less porosity. Heavy (clay) soils may have problems with air content, light (sandy) - with water regime.

For detailed analysis the entire possible range of sizes is divided into sections called factions. There is no single classification of particles. In Russian soil science, the scale of N. A. Kachinsky is adopted. The characteristic of the granulometric (mechanical) composition of the soil is given on the basis of the content of the fraction of physical clay (particles less than 0.01 mm) and physical sand (more than 0.01 mm), taking into account the type of soil formation.

The determination of the mechanical composition of the soil according to the Ferre triangle is also widely used in the world: on one side, the proportion of silt is deposited ( silt, 0.002-0.05 mm) particles, according to the second - clay ( clay, <0,002 мм), по третьей - песчаных (sand, 0.05-2 mm) and the intersection of the segments is located. Inside the triangle is divided into sections, each of which corresponds to one or another granulometric composition of the soil. The type of soil formation is not taken into account.

Organic part of the soil

The soil contains some organic matter. In organogenic (peat) soils, it can predominate, but in most mineral soils, its amount does not exceed a few percent in the upper horizons.

The composition of the organic matter of the soil includes both plant and animal remains that have not lost the features of the anatomical structure, as well as individual chemical compounds called humus. The latter contains both non-specific substances of a known structure (lipids, carbohydrates, lignin, flavonoids, pigments, wax, resins, etc.), which make up up to 10-15% of the total humus, and specific humic acids formed from them in the soil.

Humic acids do not have a specific formula and represent a whole class of macromolecular compounds. In Soviet and Russian soil science, they are traditionally divided into humic and fulvic acids.

Elemental composition of humic acids (by mass): 46-62% C, 3-6% N, 3-5% H, 32-38% O. Composition of fulvic acids: 36-44% C, 3-4.5% N, 3-5% H, 45-50% O. Both compounds also contain sulfur (from 0.1 to 1.2%), phosphorus (hundredths and tenths of a%). Molecular weights for humic acids are 20-80 kDa (minimum 5 kDa, maximum 650 kDa), for fulvic acids 4-15 kDa. Fulvic acids are more mobile, soluble throughout the entire range (humic acids precipitate in an acidic environment). The carbon ratio of humic and fulvic acids (C HA /C FA) is an important indicator of the humus status of soils.

In the molecule of humic acids, a core is isolated, consisting of aromatic rings, including nitrogen-containing heterocycles. The rings are connected by "bridges" with double bonds, creating extended conjugation chains, causing the dark color of the substance. The core is surrounded by peripheral aliphatic chains, including hydrocarbon and polypeptide types. The chains carry various functional groups (hydroxyl, carbonyl, carboxyl, amino groups, etc.), which is the reason for the high absorption capacity - 180-500 meq / 100 g.

Much less is known about the structure of fulvic acids. They have the same composition of functional groups, but a higher absorption capacity - up to 670 meq/100 g.

The mechanism of formation of humic acids (humification) is not fully understood. According to the condensation hypothesis (M. M. Kononova, A. G. Trusov), these substances are synthesized from low molecular weight organic compounds. According to the hypothesis of L. N. Alexandrova, humic acids are formed by the interaction of high-molecular compounds (proteins, biopolymers), then gradually oxidized and split. According to both hypotheses, enzymes, formed mainly by microorganisms, take part in these processes. There is an assumption about a purely biogenic origin of humic acids. In many properties, they resemble the dark-colored pigments of mushrooms.

soil structure

The structure of the soil affects the penetration of air to the roots of plants, the retention of moisture, and the development of the microbial community. Depending only on the size of the aggregates, the yield can vary by an order of magnitude. The optimal structure for plant development is dominated by aggregates ranging in size from 0.25 to 7-10 mm (agronomically valuable structure). An important property of the structure is its strength, especially water resistance.

The predominant form of aggregates is an important diagnostic feature of the soil. There are round-cubic (granular, lumpy, lumpy, dusty), prism-shaped (columnar, prismatic, prismatic) and slab-like (platy, scaly) structure, as well as a number of transitional forms and gradations in size. The first type is characteristic of the upper humus horizons and causes a large porosity, the second - for illuvial, metamorphic horizons, the third - for eluvial ones.

Neoplasms and inclusions

Main article: Soil neoplasms

Neoplasms- accumulations of substances formed in the soil in the process of its formation.

Neoplasms of iron and manganese are widespread, whose migratory ability depends on the redox potential and is controlled by organisms, especially bacteria. They are represented by concretions, tubes along the root paths, crusts, etc. In some cases, the soil mass is cemented with ferruginous material. In soils, especially in arid and semi-arid regions, calcareous neoplasms are common: plaque, efflorescence, pseudomycelium, concretions, crust formations. Gypsum neoplasms, also characteristic of arid regions, are represented by plaques, druses, gypsum roses, and crusts. There are new formations of easily soluble salts, silica (powder in eluvial-illuvial differentiated soils, opal and chalcedony interlayers and crusts, tubes), clay minerals (cutans - incrustations and crusts formed during the illuvial process), often together with humus.

TO inclusions include any objects that are in the soil, but not associated with the processes of soil formation (archaeological finds, bones, shells of mollusks and protozoa, rock fragments, debris). The assignment of coprolites, wormholes, molehills and other biogenic formations to inclusions or neoplasms is ambiguous.

Soil liquid phase

Conditions of water in the soil

Soil is divided into bound and free water. The first soil particles are so firmly held that it cannot move under the influence of gravity, and free water is subject to the law of gravity. Bound water, in turn, is divided into chemically and physically bound.

Chemically bound water is part of some minerals. This water is constitutional, crystallization and hydrated. Chemically bound water can only be removed by heating, and some forms (constitutional water) by calcining minerals. As a result of the release of chemically bound water, the properties of the body change so much that one can speak of a transition into a new mineral.

Physically bound water is retained by the soil by the forces of surface energy. Since the magnitude of the surface energy increases with an increase in the total total surface of the particles, the content of physically bound water depends on the size of the particles that make up the soil. Particles larger than 2 mm in diameter do not contain physically bound water; this ability is possessed only by particles having a diameter less than the specified one. In particles with a diameter of 2 to 0.01 mm, the ability to retain physically bound water is weakly expressed. It increases with the transition to particles smaller than 0.01 mm and is most pronounced in red colloidal and especially colloidal particles. The ability to retain physically bound water depends on more than just particle size. A certain influence is exerted by the shape of the particles and their chemical and mineralogical composition. Humus and peat have an increased ability to retain physically bound water. The particle holds the subsequent layers of water molecules with less and less force. It is loosely bound water. As the particle moves away from the surface, the attraction of water molecules by it gradually weakens. The water goes into a free state.

The first layers of water molecules, i.e. hygroscopic water, soil particles attract with tremendous force, measured in thousands of atmospheres. Being under such a high pressure, the molecules of tightly bound water are very close together, which changes many of the properties of water. It acquires the qualities of a solid body, as it were. The soil retains loosely bound water with less force, its properties are not so sharply different from free water. Nevertheless, the force of attraction is still so great that this water is not subject to the force of gravity of the earth and differs from free water in a number of physical properties.

Capillary duty cycle determines the absorption and retention of moisture brought by atmospheric precipitation in a suspended state. The penetration of moisture through the capillary pores into the depth of the soil is extremely slow. Soil permeability is mainly due to non-capillary off-duty ratio. The diameter of these pores is so large that moisture cannot be held in them in a suspended state and seeps into the soil without hindrance.

When moisture enters the soil surface, the soil is first saturated with water to the state of field moisture capacity, and then filtration through non-capillary wells occurs through the water-saturated layers. Through cracks, shrew passages and other large wells, water can penetrate deep into the soil, ahead of water saturation up to the field capacity.

The higher the non-capillary duty cycle, the higher the water permeability of the soil.

In soils, in addition to vertical filtration, there is horizontal intrasoil movement of moisture. Moisture entering the soil, encountering a layer with reduced water permeability on its way, moves inside the soil above this layer in accordance with the direction of its slope.

Interaction with the solid phase

Main article: Soil absorption complex

The soil can retain substances that have entered it through various mechanisms (mechanical filtration, adsorption of small particles, formation of insoluble compounds, biological absorption), the most important of which is ion exchange between the soil solution and the surface of the soil solid phase. The solid phase is predominantly negatively charged due to the spalling of the crystal lattice of minerals, isomorphic substitutions, the presence of carboxyl and a number of other functional groups in the composition of organic matter, therefore the cation-exchange capacity of the soil is most pronounced. However, the positive charges responsible for the anion exchange are also present in the soil.

The totality of soil components with ion-exchange capacity is called the soil absorption complex (SAC). The ions that make up the PPC are called exchange or absorbed ions. A characteristic of the CEC is the cation exchange capacity (CEC) - the total number of exchangeable cations of the same kind held by the soil in a standard state - as well as the amount of exchangeable cations that characterizes the natural state of the soil and does not always coincide with the CEC.

The ratios between the exchangeable cations of PPC do not coincide with the ratios between the same cations in the soil solution, that is, the ion exchange proceeds selectively. Preferably, cations with a higher charge are absorbed, and if they are equal, with a higher atomic mass, although the properties of the PPC components may somewhat violate this pattern. For example, montmorillonite absorbs more potassium than hydrogen protons, while kaolinite does the opposite.

Exchangeable cations are one of the direct sources of mineral nutrition for plants, the composition of the NPC is reflected in the formation of organomineral compounds, soil structure and its acidity.

Soil acidity

soil air.

Soil air consists of a mixture of various gases:

1. oxygen, which enters the soil from atmospheric air; its content may vary depending on the properties of the soil itself (its friability, for example), on the number of organisms that use oxygen for respiration and metabolic processes;
2. carbon dioxide, which is formed as a result of the respiration of soil organisms, that is, as a result of the oxidation of organic substances;
3. methane and its homologues (propane, butane), which are formed as a result of the decomposition of longer hydrocarbon chains;
4. hydrogen;
5. hydrogen sulfide;
6. nitrogen; more likely to form nitrogen in the form of more complex compounds (for example, urea)

And this is not all the gaseous substances that make up the soil air. Its chemical and quantitative composition depends on the organisms contained in the soil, the content of nutrients in it, the weathering conditions of the soil, etc.

Living organisms in the soil

Soil is a habitat for many organisms. Creatures that live in the soil are called pedobionts. The smallest of these are bacteria, algae, fungi, and single-celled organisms that live in soil water. Up to 10¹⁴ organisms can live in one m³. The soil air is inhabited by invertebrates such as mites, spiders, beetles, springtails and earthworms. They feed on plant remains, mycelium, and other organisms. Vertebrates also live in the soil, one of them is the mole. He is very well adapted to living in completely dark soil, so he is deaf and almost blind.

The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment.

• For small soil animals, which are united under the name of nanofauna (protozoa, rotifers, tardigrades, nematodes, etc.), the soil is a system of micro-reservoirs.
• For air-breathers of slightly larger animals, the soil appears as a system of shallow caves. Such animals are united under the name microfauna. The sizes of representatives of soil microfauna range from tenths to 2-3 mm. This group mainly includes arthropods: numerous groups of ticks, primary wingless insects (springtails, protura, two-tailed insects), small species of winged insects, centipedes symphyla, etc. They do not have special adaptations for digging. They crawl along the walls of soil cavities with the help of limbs or wriggling like a worm. Soil air saturated with water vapor allows you to breathe through the covers. Many species do not have a tracheal system. Such animals are very sensitive to desiccation.
• Larger soil animals, with body sizes from 2 to 20 mm, are called representatives of the mesofauna. These are insect larvae, centipedes, enchytreids, earthworms, etc. For them, the soil is a dense medium that provides significant mechanical resistance when moving. These relatively large forms move in the soil either by expanding natural wells by pushing apart soil particles, or by digging new passages.
• Soil megafauna or soil macrofauna are large excavations, mostly mammals. A number of species spend their entire lives in the soil (mole rats, mole voles, zokors, Eurasian moles, African golden moles, Australian marsupial moles, etc.). They make whole systems of passages and holes in the soil. The appearance and anatomical features of these animals reflect their adaptability to a burrowing underground lifestyle.
• In addition to the permanent inhabitants of the soil, among large animals, a large ecological group of burrow dwellers can be distinguished (ground squirrels, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but breed, hibernate, rest, and escape danger in the soil. A number of other animals use their burrows, finding in them a favorable microclimate and shelter from enemies. Norniks have structural features characteristic of terrestrial animals, but have a number of adaptations associated with a burrowing lifestyle.

Spatial organization

In nature, there are practically no situations where any single soil with properties that are unchanged in space extends for many kilometers. At the same time, differences in soils are due to differences in the factors of soil formation.

The regular spatial distribution of soils in small areas is called the soil cover structure (SCC). The initial unit of SPP is the elementary soil area (EPA) - a soil formation within which there are no soil-geographical boundaries. ESAs alternating in space and to some extent genetically related form soil combinations.

soil formation

Soil-forming factors :

• Elements of the natural environment: soil-forming rocks, climate, living and dead organisms, age and terrain,
• as well as anthropogenic activities that have a significant impact on soil formation.

Primary soil formation

In Russian soil science, the concept is given that any substrate system that ensures the growth and development of plants "from seed to seed" is soil. This idea is debatable, since it denies the Dokuchaev principle of historicity, which implies a certain maturity of soils and the division of the profile into genetic horizons, but is useful in understanding the general concept of soil development.

The rudimentary state of the soil profile before the appearance of the first signs of horizons can be defined by the term "initial soils". Accordingly, the “initial stage of soil formation” is distinguished - from the soil “according to Veski” until the time when a noticeable differentiation of the profile into horizons appears, and it will be possible to predict the classification status of the soil. The term "young soils" is proposed to assign the stage of "young soil formation" - from the appearance of the first signs of horizons to the time when the genetic (more precisely, morphological-analytical) appearance is sufficiently pronounced for diagnosis and classification from the general positions of soil science.

Genetic characteristics can be given even before the maturity of the profile, with an understandable share of prognostic risk, for example, “initial soddy soils”; "young propodzolic soils", "young carbonate soils". With this approach, nomenclature difficulties are resolved naturally, based on the general principles of soil-ecological forecasting in accordance with the Dokuchaev-Jenney formula (representation of soil as a function of soil formation factors: S = f(cl, o, r, p, t ...)).

Anthropogenic soil formation

In the scientific literature for lands after mining and other disturbances of the soil cover, the generalized name “technogenic landscapes” has been fixed, and the study of soil formation in these landscapes has taken shape in “reclamation soil science”. The term "technozems" was also proposed, essentially representing an attempt to combine the Dokuchaev tradition of "-zems" with man-made landscapes.

It is noted that it is more logical to apply the term "technozem" to those soils that are specially created in the process of mining technology by leveling the surface and pouring specially removed humus horizons or potentially fertile soils (loess). The use of this term for genetic soil science is hardly justified, since the final, climax product of soil formation will not be a new "-earth", but a zonal soil, for example, soddy-podzolic or soddy-gley.

For technogenically disturbed soils, it was proposed to use the terms "initial soils" (from the "zero moment" to the appearance of horizons) and "young soils" (from the appearance to the formation of diagnostic features of mature soils), indicating the main feature of such soil formations - the time stages of their development. evolution from undifferentiated rocks to zonal soils.

Soil classification

There is no single generally accepted classification of soils. Along with the international one (FAO Soil Classification and WRB, which replaced it in 1998), many countries around the world have national soil classification systems, often based on fundamentally different approaches.

In Russia, by 2004, a special commission of the Soil Institute. V. V. Dokuchaeva, led by L. L. Shishov, prepared a new classification of soils, which is a development of the 1997 classification. However, Russian soil scientists continue to actively use the USSR soil classification of 1977.

Among the distinguishing features of the new classification, we can mention the refusal to use factor-environmental and regime parameters for diagnosis, which are difficult to diagnose and often determined by the researcher purely subjectively, focusing attention on the soil profile and its morphological features. A number of researchers see this as a departure from genetic soil science, which focuses on the origin of soils and the processes of soil formation. The 2004 classification introduces formal criteria for assigning soil to a particular taxon, and uses the concept of a diagnostic horizon, which is accepted in the international and American classifications. Unlike the WRB and the American Soil Taxonomy, in the Russian classification, horizons and characters are not equivalent, but are strictly ranked according to their taxonomic significance. Undoubtedly, an important innovation of the 2004 classification was the inclusion of anthropogenically transformed soils in it.

The American school of soil scientists uses the Soil Taxonomy classification, which is also widespread in other countries. Its characteristic feature is the deep elaboration of formal criteria for assigning soils to a particular taxon. Soil names constructed from Latin and Greek roots are used. The classification scheme traditionally includes soil series - groups of soils that differ only in granulometric composition and have an individual name - the description of which began when the US Soil Bureau mapped the territory at the beginning of the 20th century.

Soil classification - a system for dividing soils by origin and (or) properties.

• Soil type is the main classification unit, characterized by the commonality of properties determined by the regimes and processes of soil formation, and by a single system of basic genetic horizons.
  • A soil subtype is a classification unit within a type, characterized by qualitative differences in the system of genetic horizons and in the manifestation of overlapping processes that characterize the transition to another type.
    • Soil genus - a classification unit within a subtype, determined by the characteristics of the composition of the soil-absorbing complex, the nature of the salt profile, and the main forms of neoplasms.
      • Soil type - a classification unit within a genus, quantitatively differing in the degree of expression of soil-forming processes that determine the type, subtype and genus of soils.
        • Soil variety is a classification unit that takes into account the division of soils according to the granulometric composition of the entire soil profile.
          • Soil category - a classification unit that groups soils according to the nature of soil-forming and underlying rocks.

Distribution patterns

Climate as a factor in the geographical distribution of soils

Climate, one of the most important factors in soil formation and geographic distribution of soils, is largely determined by cosmic causes (the amount of energy received by the earth's surface from the sun). The manifestation of the most general laws of soil geography is associated with climate. It affects soil formation both directly, by determining the energy level and hydrothermal regime of soils, and indirectly, by influencing other factors of soil formation (vegetation, vital activity of organisms, soil-forming rocks, etc.).

The direct influence of climate on the geography of soils is manifested in different types of hydrothermal conditions of soil formation. The thermal and water regimes of soils affect the nature and intensity of all physical, chemical and biological processes occurring in the soil. They regulate the processes of physical weathering of rocks, the intensity of chemical reactions, the concentration of soil solution, the ratio of the solid and liquid phases, and the solubility of gases. Hydrothermal conditions affect the intensity of the biochemical activity of bacteria, the rate of decomposition of organic residues, the vital activity of organisms and other factors, therefore, in different regions of the country with unequal thermal conditions, the rate of weathering and soil formation, the thickness of the soil profile and weathering products are significantly different.

The climate determines the most general patterns of soil distribution - horizontal zonality and vertical zonality.

The climate is the result of the interaction of climate-forming processes occurring in the atmosphere and the active layer (oceans, cryosphere, land surface and biomass) - the so-called climate system, all components of which continuously interact with each other, exchanging matter and energy. Climate-forming processes can be divided into three complexes: processes of heat exchange, moisture exchange and atmospheric circulation.

The value of soils in nature

Soil as a habitat for living organisms

The soil has fertility - it is the most favorable substrate or habitat for the vast majority of living beings - microorganisms, animals and plants. It is also significant that in terms of their biomass, the soil (the land of the Earth) is almost 700 times greater than the ocean, although the share of land accounts for less than 1/3 of the earth's surface.

Geochemical features

The property of different soils to accumulate various chemical elements and compounds in different ways, some of which are necessary for living beings (biophilic elements and microelements, various physiologically active substances), while others are harmful or toxic (heavy metals, halogens, toxins, etc.) , manifests itself in all plants and animals living on them, including humans. In agronomy, veterinary science and medicine, such a relationship is known in the form of so-called endemic diseases, the causes of which were revealed only after the work of soil scientists.

The soil has a significant impact on the composition and properties of surface and groundwater and the entire hydrosphere of the Earth. Filtering through the soil layers, water extracts from them a special set of chemical elements, characteristic of the soils of the catchment areas. And since the main economic indicators of water (its technological and hygienic value) are determined by the content and ratio of these elements, the disturbance of the soil cover also manifests itself in a change in water quality.

Regulation of the composition of the atmosphere

Soil is the main regulator of the composition of the Earth's atmosphere. This is due to the activity of soil microorganisms, which produce a variety of gases on a huge scale -

Arctic desert zone. Franz Josef Land, Novaya Zemlya, Severnaya Zemlya, and the New Siberian Islands lie in this zone. The zone is characterized by a huge amount of ice and snow in all seasons of the year. They are the main element of the landscape.

The arctic air prevails here all year round, the radiation balance for the year is less than 400 mJ/m 2 , the average temperature in July is 4-2°C. Relative humidity is very high - 85%. Precipitation is 400-200 mm, and almost all of it falls in solid form, which contributes to the formation of ice sheets and glaciers. However, in some places the supply of moisture in the air is small, and therefore, with an increase in temperature and a strong wind, a large lack of it is formed and strong evaporation of snow occurs.

The soil-forming process in the Arctic takes place in a thin active layer and is at the initial stage of development. In the valleys of rivers and streams and on sea terraces, two types of soils are formed - typical polar desert soils on drained polygonal plains and polar desert solonchak soils in saline coastal areas. They are characterized by a low content of humus (up to 1.5%), weakly expressed genetic horizons and very small thickness. In the Arctic deserts, there are almost no swamps, few lakes, and salt spots form on the surface of the soil in dry weather with strong winds.

The vegetation cover is extremely sparse and patchy, it is characterized by poor species composition and exceptionally low productivity. Low-organized plants dominate: lichens, mosses, algae. The annual growth of mosses and lichens does not exceed 1-2 mm. Plants are extremely selective in their distribution. More or less close groupings of plants exist only in places sheltered from cold winds, on fine earth, where the thickness of the active layer is greater.

The main background of the Arctic deserts is formed by scale lichens. Hypnum mosses are common, sphagnum mosses appear only in the south of the zone in very limited quantities. Of the higher plants, saxifrage, polar poppy, grains, chickweed, arctic pike, bluegrass and some others are characteristic. Cereals grow luxuriantly, forming hemispherical pillows up to 10 cm in diameter on a fertilized substrate near nesting gulls and lemming burrows. An ice ranunculus and a polar willow grow near the snow patches, reaching only 3-5 cm in height. The fauna, like the flora, is poor in species; there are lemmings, arctic foxes, reindeer, polar bears, and among the birds the white partridge and snowy owl are ubiquitous. On the rocky shores there are numerous bird colonies - mass nesting of sea birds (guillemots, little auks, white gulls, fulmars, eiders, etc.). The southern shores of Franz Josef Land, the western shores of Novaya Zemlya are a continuous bird colony.

Each natural zone is defined using several features: vegetation type, fauna, climatic conditions, etc. The type and composition of the soil also directly depends on these factors. In addition, the fertility of the land is affected by humidity, evaporation, and relief features.

The soil gives life to plants, which are the beginning of the food chains of ecosystems. Therefore, one or another type of natural complex and climate plays a decisive role in the formation of soil cover.

Relationship between soil and natural areas

This table proposes to consider the correspondence between ecosystem types and main soil classes.

Zone name	soil type		soil properties	soil formation conditions
Arctic deserts	arctic	Very little	infertile	Lack of heat and vegetation
	Tundra-gley		Low power, gel layer	Permafrost, little heat, waterlogging
Taiga of the European part	Podzolic	Slightly	Flushing, acidic	Fallen needles strongly oxidize the soil, permafrost
Taiga of Eastern Siberia	taiga-permafrost	Slightly	Infertile, cold	Permafrost
mixed forests	Sod-podzolic	More than in podzolic	More fertile	Flushing in the spring, more plant residues
broadleaf forests	gray forest		More fertile	Mild climate, fallen tree leaves are rich in ash elements
Steppes and forest-steppes	Chernozems, chestnut		The most fertile	Lots of plant remains, warm climate
semi-deserts	Brown, gray-brown	less humus	Soil salinization	Dry climate, sparse vegetation
	Desert yellowish gray		Due to rare rains, salts are almost not washed out.	Lack of moisture and poverty of organic matter
Hard-leaved evergreen forests and shrubs	Brown		High fertility with sufficient moisture	The growing season lasts all year round
Tropical rainforests	Red-yellow ferralitic and red-brown	The share of humus is 3-10%	Good washing of the soil cover, high content of iron hydroxide	High humidity, year-round high temperatures, huge plant biomass

The diversity of the surrounding landscapes and climate affects the fertility of the land in different ways. So, some soils can give life to a huge number of crops, while others are practically barren.

Soil types

Soil, like vegetation, is formed in certain climatic conditions. Therefore, the tundra is overgrown with mosses and low shrubs, and, for example, the tropical forest is distinguished by lush and lush vegetation. All types of soils are located in accordance with geographical zonality.

Tundra

The tundra zone, which occupies about 3%, is located in the subarctic climate zone. The ecosystem occupies the entire coast of the Arctic Ocean and the islands north of Antarctica. The land in the tundra is formed under the influence of severe frosts, excessive moisture and a modest vegetation cover.

Depending on the relief and drainage, the following types of tundra soils are distinguished:

• acid brown - receive a sufficient amount of moisture and oxygen, are located in the mountain tundra or on hills;
• tundra-gley - are, on the contrary, in the lowlands, are formed in conditions of stagnant water, poor drainage and lack of oxygen;
• peat-gley - located in the southern tundra and forest tundra, where the climate is warmer and milder than in a typical tundra;
• tundra-marsh - lie in the recesses of the relief, can form tundra solonchaks;
• soddy acid soils - are located in floodplains, grasses and cereals grow on them, as a result of which these soils are relatively rich in nutrients;
• polygonal peatlands - common in some areas of the tundra, formed during the Holocene, when there was a forest zone in these places.

Throughout the tundra lies a layer of permafrost. It is located close to the surface, as a result of which the earth is highly moistened and swampy. Strong cooling of the soil adversely affects the processes of soil formation and vegetation development.

Podzolic

South of the tundra is a huge ecosystem - the taiga. The podzolic type of soil is characteristic of these northern coniferous forests. Its distinguishing feature is high humidity and a high degree of oxidation due to fallen pine needles.

Since the taiga zone has a large extent from north to south, the podzolic type is divided into several types depending on climatic conditions:

• gley-podzolic - common in the northern taiga, shrubs, dwarf trees, northern conifers grow on them;
• actually podzolic - characteristic of a typical taiga, where spruces, cedars, firs, pines, etc. grow on a cover of moss and lichen;
• sod-podzolic - the southern taiga zone, where deciduous trees begin to be mixed with conifers.

In addition to distribution by subzones, podzolic soils are divided according to the thickness of the layer, structure and nature of soil formation.

gray forest

This type of soil lies below the surface of broadleaf forests. It contains a significant proportion of humus, which gives the soil a shade from light to dark gray.

Depending on the content of organic matter and fertility, forest soils are divided into:

• light gray - the content of humus is insignificant (up to 5%), according to their characteristics they are close to soddy-podzolic soils of the southern taiga;
• gray - the proportion of humus here can be up to 8%, humic acids are also present;
• dark gray - the amount of organic matter reaches 10%, this is the most fertile and slightly acidic type of forest soil.

This amount of organic matter is formed due to the relatively dry climate, as well as the processes of decay of fallen leaves and grass cover.

Chernozem

Chernozem soils are formed in steppe and forest-steppe regions with a warm, dry climate and rich meadow-herbaceous vegetation. This is the richest type of soil cover in organic and mineral substances. The chernozem is rich in magnesium, iron and calcium, and the humus content reaches 15%, the layer thickness of which is 1-1.5 m.

By composition, chernozem is divided into subtypes:

• podzolized - painted in gray or dark gray, and due to podzolization processes they have a characteristic whitish coating;
• leached - unlike the podzolized subtype, they do not have a plaque, but contain a leached brownish horizon;
• ordinary - located in the north of the steppe zone, have a dark gray or black color, the thickness of the humus layer reaches 80 cm;
• typical - in them, chernozem processes are expressed as much as possible, the thickness of humus can take more than 120 cm;
• southern - common in the south of the steppes, they show a gradual decrease in the proportion of humus (up to 7%), and the thickness of the fertile layer is about 60 cm.

At present, the areas occupied by chernozem soils are almost completely plowed up. Only small areas in ravines, beams, virgin fields, and also in nature reserves remained intact.

Bolotnaya

The main area of ​​distribution is plains covered with tundra and taiga. Wetland is formed as a result of excessive moisture, as well as processes such as gleying and peat formation. The concept of "gleying" means that the soil is formed with the participation of microorganisms and the constant washing of a significant layer of soil. Peat is created as a result of the decomposition of plant residues.

Depending on the location on the surface of the relief, the composition of vegetation and soil, the swamps are divided into:

• riding - occupy flat flat areas, are formed as a result of the influence of groundwater or atmospheric waters, the surface is covered with sphagnum mosses;
• transitional - occupy an intermediate position between the upland and lowland types, the formation occurs with alternate wetting with hard and soft waters;
• low-lying - located in the recesses of the relief, sedge and cereal grasses, dwarf birches, willows, etc. grow on them.

Peat of low-lying swamps has the most beneficial properties: it has a low degree of acidity and is saturated with minerals. Swamp soils are best formed in small reservoirs and lakes with stagnant water.

Lugovaya

Meadow soils are formed in places where meadow vegetation grows.

This type of soil is divided into two subtypes:

• typical meadow - formed in the area of ​​groundwater at 1.5-2.5 m, under the plants of meadow zones;
• wet-meadow (marshy-meadow) - are located in the lower areas of river valleys, in conditions of constant moisture, cereal and sedge grasses grow on them.

All types of meadow soil have a good humus content (4-6%), so they are intensively used for agriculture.

comparison table

It contains a brief description of natural complexes, as well as their geographical location, soils and vegetation that grows there.

It can be concluded that the most favorable conditions for the development of flora are a warm climate and high, year-round humidity.

Economic importance

Soil is the most important element in the formation of all living organisms on Earth. At the same time, the composition of the soil is formed due to the vital processes of plants and animals. But not every type of soil can give a good harvest.

On what kind of soil is best to grow certain crops, it is written below:

1. Clay. With the addition of peat, sand and ash, it is excellent for growing fruit trees, shrubs, potatoes, peas, and beets.
2. Sandy. It is fertilized with peat, compost, clay or mulching. This type of soil is suitable for growing almost all crops.
3. Sandy. To increase fertility, fertilizers are applied, mulched, and green manure plants are planted. It can also grow almost all kinds of vegetables and fruits.
4. Loamy. It contains a large amount of nutrients, you just need to add mineral fertilizers and mulch. Suitable for most types of crops.
5. Chernozem. The most fertile soil type, requiring no fertilizer at first. After a few years, it is recommended to sow green manure plants and add organic matter. All fruit and vegetable crops take root perfectly on it.
6. Peaty-marshy. It is recommended to apply fertilizers from sand, clay, phosphorus and organic matter into it. On such soil it is good to grow berry bushes.
7. Lime. Requires a large amount of fertilizer due to lack of manganese and iron. Suitable for plants that are not too demanding on soil acidity.

The soil is a unique natural phenomenon. When drawing up a plan for cultivating a plot or field, it is necessary to correctly calculate the load on the soil, because it takes several thousand years to form a small layer of earth.

Features of soils and vegetation of different natural zones

Each natural zone is characterized by a certain set of flora, fauna, climatic features and soil type.

1. Arctic deserts. They are located in the north of Eurasia and North America. Vegetation is practically absent, the soil is infertile.
2. Tundra. Covers the coast of the Arctic Ocean. The ground is covered with mosses, lichens, grasses. Shrubs and dwarf trees begin to appear in the south of the zone. The soil is thin, there is permafrost.
3. Taiga. The largest ecosystem by area. It occupies most of the temperate forests. Coniferous trees dominate: pines, spruces, fir, larches, cedars. The soil is acidic, cold and unsuitable for most plants.
4. Mixed forests. They are located south of the taiga. Deciduous and coniferous trees. The land is more fertile due to more plant residues.
5. Broad-leaved forests. They are located in Europe, the Russian Plain, Asia, and in places in South America. Oaks, ash-trees, lindens, maples grow here. The soil is fertile due to fallen leaves and a warm climate.
6. Steppes and forest-steppes. The Russian steppes occupy a wide strip in the south of the country. On other continents, in terms of climatic and natural conditions, the African savannas, North American prairies and South American pampas are similar to the steppes. Grassy plains with some small forests in the north. The most fertile soil, consisting of varieties of chernozem.
7. Semi-deserts and deserts. They are located in the south of Eurasia, in Africa, in Australia. Occasionally there are plants - shrubs, cacti, cereals and herbs. The earth is saline, hot and dry climate does not allow most plants to grow.
8. Subtropics and tropics. Located on the Mediterranean coast. The earth is colored red-yellow due to the large amount of iron. The subtropics are heterogeneous: acacias, chestnuts, oaks, hornbeams, and beeches grow in the subtropical forests in southern Russia. In other areas of the zone, pines, oaks, ferns, bamboo and palm trees coexist simultaneously. A huge number of heat-loving plants grow in tropical forests.

Thus, vegetation and soil composition are interconnected: the more plants, the warmer the climate, the richer and more saturated the earth will be.

Animals

Natural areas are inhabited by a wide variety of animals that have been able to adapt to the conditions of these places. Consider the composition of the fauna of various ecosystems.

Arctic

The coldest zone is inhabited by animals and birds that are perfectly adapted to extreme frosts: very thick fur or feathers, white color to hide in snowy spaces, etc. The total number of inhabitants is small, but they all have their own uniqueness and beauty: polar bears, arctic foxes, arctic hares, polar owls, walruses, seals.

Tundra

There is already a greater variety of living organisms. Many animals move south for the winter to the forests, but there are also those who live in the tundra all year round. The main inhabitants of the tundra are represented by reindeer, arctic foxes, hares, wolves, polar and brown bears, lemmings, polar owls. There are a lot of mosquitoes and midges in the tundra due to the large accumulation of swamps.

forest zone

Temperate forests stretch in a wide strip from the northern forest-tundra to the southern forest-steppes. The diversity of fauna also varies from north to south. So, in the taiga, the species composition of animals is not as diverse as in mixed and broad-leaved forests. But basically the animal composition of the forest zone is approximately the same: brown bears, wolves, foxes, lynxes, elks, red deer, hares.

Steppe

In the wide and open expanses of the steppes, large animals have nowhere to hide, so small predators and animals live here. These are mainly steppe wolves, corsac foxes, saigas, hares, marmots, prairie dogs, bustards, storks.

Desert

If the Arctic is an extremely cold desert, then the tropical type of this zone is very hot and dry. The local inhabitants have learned to do without water for a long time and have adapted to the unbearable heat: camels, antelopes, fennec foxes, monitor lizards, scorpions, snakes and lizards.

Tropics

The rainforests are home to the largest variety of animals on the planet. These forests are multi-tiered, and each tier is inhabited by thousands of different creatures. Among the main inhabitants can be listed: leopards, tigers, elephants, antelopes, okapi, gorillas, chimpanzees, parrots, toucans, as well as a huge number of butterflies and insects.

The richest belt in terms of vegetation

The equatorial and subequatorial climatic zones of the Earth are recognized as areas with the most diverse and numerous flora and fauna. Multilayer tropical forests grow and develop on ferralitic red-yellow soils. High trunks of palms, ficuses, chocolate, banana, iron and coffee trees wrap around vines, mosses, ferns and orchids grow on their surface.

Such a variety of plants is due to the absence of frosts: the temperature even on the coldest days does not fall below +20°C. Also, the nature of the tropics is characterized by a huge amount of precipitation. Up to 7000 mm of precipitation falls in the form of heavy showers per year in the tropics. In conditions of constant humidity and heat, most of the plants on Earth grow and develop.

Video

This video talks about the soil and plants of various natural areas.

 

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