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

The content of the article

THE SOIL- the most surface layer of the earth's land, resulting from changes in rocks under the influence of living and dead organisms (vegetation, animals, microorganisms), solar heat and precipitation. The soil is a completely special natural formation with only its inherent structure, composition and properties. The most important property of the soil is its fertility, i.e. the ability to ensure the growth and development of plants. To be fertile, the soil must have a sufficient amount of nutrients and a supply of water necessary for plant nutrition; it is precisely by its fertility that the soil, as a natural body, differs from all other natural bodies (for example, barren stone), which are not able to provide the need of plants for 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 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 for solving a number of problems in health care, exploration and extraction of minerals, the organization of green zones in the urban economy, environmental monitoring, etc.

Soil Science: History, Relationship with Other Sciences.

The science of the origin and development of soils, the patterns of their distribution, 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 and 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. By now, large applied sections of soil science have been formed for agriculture and forestry, irrigation, construction, transport, prospecting for minerals, health care and environmental protection.

Since the systematic occupation of agriculture, mankind, first empirically, and then using scientific methods, studied the soil. The earliest attempts to evaluate various soils are known in China (3 thousand BC) and Ancient Egypt. In ancient Greece, the idea of \u200b\u200bsoil was formed in the process of the development of ancient natural philosophical natural science. During the period of the Roman Empire, a large number of empirical observations of soil properties were accumulated and some agronomic methods of soil 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 decomposition 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 Albrecht Thayer's humus theory, 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 assimilate minerals from the soil, and only carbon in the form of carbon dioxide from humus. Y. Liebikh believed that each harvest depletes the supply of minerals in the soil, therefore, in order to eliminate this deficiency of elements, it is necessary to apply factory-prepared mineral fertilizers to the soil. The merit of Liebig was the introduction of the use of mineral fertilizers into the practice of agriculture.

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

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

The outstanding Russian scientist Vasily Vasilyevich Dokuchaev (1846-1903) became the founder of soil science as an independent natural history science. Dokuchaev was the first to formulate the scientific definition of soil, calling the 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 about which Dokuchaev spoke were known before him, they were consistently put forward by different 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 joint action of all factors of soil formation. He established a view of soil as an independent special natural body, equivalent to the concepts of plant, animal, mineral, etc., which arises, develops, continuously changes in time and space, and with this 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 regularity of the spatial distribution of certain types of soils covering the land surface in the form of horizontal or latitudinal zones, established vertical zoning, or zonality, in the distribution of soils, which is understood as the regular change of some soils by others as they rise from the foot to the top of the high mountains. He also belongs to the first scientific classification of soils, which was based on the entire set of the most important characteristics and properties of the soil. Dokuchaev's classification was recognized by world science and his proposed names "black earth", "podzol", "saline", "solonetz" have become 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.)

Scientists from other countries have also carried out important studies for understanding the processes of soil formation and studying the soils of different territories. They are E.V. Gilgard (USA); E. Ramann, E. Blank, V. I. Kubiena (Germany); A. de Sigmond (Hungary); J. Milne (Great Britain), J. Aubert, R. Menien, J. Durand, N. Leneuf, G. Hérard, F. Duchaufour (France); J. Prescott, S. Stephens (Australia) and many others.

For the development of theoretical concepts and the successful study of the soil cover of our planet, business contacts between different national schools are necessary. In 1924 the International Soil Science Society 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 the compilation of which Russian scientists played a large role.

Soil study methods.

One of them is comparatively geographical, based on the simultaneous study of the soils themselves (their morphological characteristics, physical and chemical properties) and the factors of soil formation in different geographical conditions with their subsequent comparison. Nowadays, in soil research, various chemical analyzes, analyzes of physical properties, mineralogical, thermochemical, microbiological and many other analyzes are used. As a result, a definite connection is established in the change of certain soil properties with a 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 "Schemes of soil zones of the Northern Hemisphere."

Another method is the stationary research method 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 research clarifies and details the method of comparative geographical research. 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 immediately to collapse. The sum of the transformation processes of rocks on the Earth's surface is called weathering or hypergenesis. The collection of weathering products is called the weathering crust. The process of transforming the original rocks into the weathering crust is extremely complex and includes numerous processes and phenomena. Depending on the nature and causes of destruction of rocks, physical, chemical and biological weathering is distinguished, which usually comes down to the physical and chemical effects of organisms on rocks.

Weathering (hypergenesis) processes spread to a certain depth, forming a zone of hypergenesis . The lower boundary of this zone is conventionally drawn along the top of the upper horizon of underground (stratal) waters. The lower (and most) part of the hypergenesis zone is occupied by rocks, to one degree or another altered by weathering processes. Here the newest and ancient weathering crust is distinguished, formed in more ancient geological periods. The surface layer of the hypergenesis zone is the substrate on which the 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 turned into a fractured state. Examples of rocks crushed as a result of weathering are grit, sand, and clay. Becoming fragmented, the 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, increasing chemical weathering, new compounds were formed, including easily soluble in water compounds, and, finally, mountainous breeds 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, therefore, could not transform the rock into soil. The easily soluble compounds formed as a result of weathering can only be washed out of rocks under the influence of atmospheric precipitation; and such an important biological element as nitrogen, consumed by plants in large quantities, is completely absent in igneous rocks.

Loose and water-absorbing rocks became a favorable environment for the life of bacteria and various plant organisms. Gradually, the upper layer of the weathering crust was enriched with the products of the vital activity of organisms and their dying off remains. The decomposition of organic substances and the presence of oxygen led to complex chemical processes, as a result of which the elements of ash and nitrogen food accumulated 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. Thus, the composition of the soil 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 products of weathering of rocks. From that moment on, the crushed rock became soil, i.e. a qualitatively new body with a number of qualities and properties, the most essential of which is fertility. In this respect, all existing soils on the globe are 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 it was born, the soil-forming process never stopped.

Factors of soil formation.

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 combination of them.

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

Parent rocks.

All existing soils on Earth originated from rocks, so it is obvious that they are most 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, in the main, those elements that were part of the parent rock. The physical properties of the parent rock are also of great importance, since factors such as the granulometric composition of the rock, its density, porosity, and thermal conductivity 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 of climatic conditions are temperature and precipitation. The annual amount of incoming heat and moisture, the peculiarities of their daily and seasonal distribution, determine completely definite processes of soil formation. The climate affects the nature of weathering of rocks, affects the thermal and water regimes of the soil. The movement of air masses (wind) affects the gas exchange of the soil and captures fine soil particles in the form of dust. But the climate affects the soil not only directly, but also indirectly, since the existence of one or another vegetation, the habitat of certain animals, as well as the intensity of microbiological activity is determined precisely by climatic conditions.

Vegetation, animals and microorganisms.

Vegetation.

The importance of vegetation in soil formation is extremely great and diverse. Penetrating the roots of the upper layer of the parent rock, plants extract nutrients from its lower horizons and fix them in the synthesized organic matter. After the mineralization of dead plant parts, the ash elements contained in them are deposited in the upper horizon of the parent 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 an essential 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.

Plants themselves, in the course of their vital activity, secrete various weak acids with their roots, under the influence of which hardly soluble mineral compounds are partially converted into a soluble, and therefore, into a form assimilated by plants.

In addition, the vegetation cover significantly changes the microclimatic conditions. For example, in the forest, in comparison with treeless areas, the summer temperature is lower, the humidity of the air and soil is increased, the wind force and evaporation of water above the soil are reduced, more snow, melt and rainwater accumulates - all this inevitably affects the soil-forming 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 that are 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 vegetation formation of coniferous forests, chernozem will never form, which is formed under the influence of meadow-steppe vegetation formation.

Animal world.

Animal organisms, which are abundant in the soil, are of great importance for soil formation. The most important are invertebrates living in the upper soil horizons and in plant residues on the surface. In the course of their vital activity, they significantly accelerate the decomposition of organic matter and often produce very profound changes in the chemical and physical properties of the soil. Burrowing animals, such as moles, mice, ground squirrels, marmots, etc., play an important role. Repeatedly digging through the soil, they contribute to the mixing of organic substances with minerals, as well as to increase the water and air permeability of the soil, which enhances and accelerates the 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 entering the soil, a significant part of 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 mainly reduced to the redistribution of heat and moisture. A significant change in the altitude of the terrain entails significant changes in temperature conditions (it gets colder with height). This is associated with the phenomenon of vertical zoning in the mountains. Relatively small changes in altitude affect the redistribution of atmospheric precipitation: low areas, hollows and depressions are always moistened to a greater extent than slopes and rises. The exposure of the slope determines the amount of solar energy coming to 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. Obviously, in different microclimatic conditions, the processes of soil formation will proceed in different ways. Of great importance in the formation of the soil cover is the systematic washout and redistribution of fine-earth particles by atmospheric precipitation and melt water over the relief elements. The significance of the relief is great in conditions of abundant precipitation: areas devoid of natural runoff of excess moisture are very often subject to waterlogging.

Soil age.

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

There are absolute and relative soil ages. The absolute age of soils is called the period of time elapsed from the moment the soil was formed to the present stage of its development. The soil arose when the parent rock came out 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 limits of different parts of the land, which were simultaneously freed from the water or ice cover, the soil will not always go through the same stage of its development at each given moment. The reason for this may be differences in the composition of the parent rocks, in the relief, vegetation and other local conditions. The difference in the stages of soil development in one common territory, which has the same absolute age, is called the relative soil age.

The development time of a mature soil profile for different conditions is from several hundred to several thousand years. The age of the territory in general and of the 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 geographic conditions of soil formation, soils with different ages and developmental histories can differ significantly and belong to different classification groups.

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

Soil and ground waters.

Water is a medium in which numerous chemical and biological processes in the soil take place. 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 chemical compounds that they contain, sometimes causing salinization. Waterlogged soils contain insufficient oxygen, which causes suppression of the activity of some groups of microorganisms.

Human economic activity affects some factors of soil formation, for example, on vegetation (deforestation, replacing it with herbaceous phytocenoses, etc.), and directly on the soil by 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 constantly increasing.

The impact of human society on the soil cover is one of the sides of the overall human impact on the environment. Nowadays, the problem of destruction of the soil cover as a result of improper agricultural soil cultivation and human construction activities is especially acute. The second major problem is soil pollution caused by chemicalization of agriculture and industrial and household emissions into the environment.

All factors do not influence 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 effect on all factors of soil formation, causing certain changes in each of them. So, 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.

Soil consists of solid, liquid, gaseous and living parts. Their ratio is not the same not only in different soils, but also in different horizons of the same soil. Naturally, 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 transformation of the components of the parent rock from the lower horizons to the upper ones.

The solid part of the soil is dominated by mineral substances of lithogenic origin. These are fragments and particles of primary minerals of various sizes (quartz, feldspars, hornblendes, mica, etc.), which are 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 looseness of the soil structure. 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 trace elements: Cu, Mo, I, B, F, Pb, etc. The vast majority of elements are in oxidized form. In many soils, mainly in soils of insufficiently moistened territories, there is a significant amount of calcium carbonate CaCO 3 (especially if the soil was formed on a carbonate rock), in soils of arid regions - CaSO 4 and other more readily soluble salts (chlorites); soils in humid tropical regions are enriched in Fe and Al. However, the implementation of these general laws depends on the composition of the parent rocks, soil age, relief features, climate, etc.

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 got into the soil in the form of plant and animal residues and new, specific humic substances arising 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 products of the vital activity 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 a complex complex of humic substances, or humus, which arose as a result of 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 compounds of acidic nature. The main groups of humic substances are humic acids and fulvac acids . Carbon, oxygen, hydrogen, nitrogen and phosphorus play an important role in the elemental composition of humic substances. The humus contains the main elements of plant nutrition, which, under the influence of microorganisms, become available to plants. The humus content in the upper horizon of different types of soils 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 resulting structure of the soil largely determines its physical properties, as well as water, air and thermal conditions.

The liquid part of the soil or, as it is also called, the soil solution Is the water contained in the soil with dissolved gases, minerals and organic substances that have got into it when passing through the atmosphere and seeping through the soil. The composition of soil moisture is determined by the processes of soil formation, vegetation, general features of the climate, as well as the season, weather, human activities (fertilization, etc.).

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 environment in which the migration of chemical elements occurs during 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 (salt marshes and solonetzes) it is sharply increased (up to as many as tens of percent). The high content of substances in the soil moisture is harmful to plants, because this makes it difficult for them to get water and nutrients, causing physiological dryness.

The reaction of the soil solution in soils of different types is not the same: acidic reaction (pH 7) - soda solonetzes, neutral or slightly alkaline (pH \u003d 7) - ordinary chernozems, meadow and brown soils. Too acidic and too alkaline soil solution negatively affects the growth and development of plants.

The gaseous part, or soil air, fills the pores of the soil not occupied by water. The total volume of soil pores (porosity) is from 25 to 60% of the soil volume ( cm... Morphological characteristics 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 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 the season, it can change significantly. For example, the amount of carbon dioxide (CO 2) in the soil air changes significantly in the annual and daily cycles due to the different rates of gas emission by microorganisms and plant roots.

Constant gas exchange takes place between the soil and atmospheric air. 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. 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, therefore, the normal development of plants is possible only under conditions of sufficient air access to the soil. With insufficient oxygen penetration into the soil, plants are inhibited, slow down their growth, and sometimes even completely die.

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 stops, and in this regard, the formation of nutrients necessary for plants in the soil stops. In addition, under anaerobic conditions, processes occur that lead to the accumulation of compounds harmful to plants in the soil.

Sometimes, some gases may be present in the soil air, penetrating through the strata of rocks from places of their accumulation; this is the basis for special gas geochemical methods of 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 the phenomena that determine the intake, movement, consumption and use of soil moisture by plants. Soil water regime – the most important factor in soil formation and soil fertility.

Precipitation is the main source of soil water. A certain amount of water enters the soil as a result of condensation of steam from the air, sometimes nearby groundwater plays a significant role. In areas of irrigated agriculture, irrigation is of great importance.

Water consumption is as follows. Part of the water entering the soil surface flows down as surface runoff. The largest amount of moisture entering the soil is absorbed by plants, which then partially evaporate it. Some water is consumed 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 subsurface runoff - a temporarily existing 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 Finally, a significant part of the soil water can reach the surface of the groundwater, the outflow of which occurs along the waterproof bed-water confinement, and leave as part of the groundwater runoff.

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

Technological processes during soil cultivation, the supply of water to plants, physicochemical and microbiological processes that determine the transformation of nutrients in the soil and their supply with water to the plant depend on the water content in the soil. 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 the cultivated soils - on the characteristics of cultivated plants and their cultivation technique.

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

Pririmyvny in the type of water regime, the entire soil layer is annually soaked to groundwater, while the soil returns to the atmosphere less moisture than it receives (excess moisture seeps into the groundwater). Under the conditions of this regime, the soil-subsoil stratum is washed out by gravitational water every year. The flushed type of water regime is typical for humid temperate and tropical climates, where the amount of precipitation is greater than evaporation.

The non-flush type of water regime is characterized by the absence of continuous soaking of the soil mass. Atmospheric moisture penetrates into the soil to a depth of several decimeters to several meters (usually no more than 4 m), and between the wetted soil layer and the upper boundary of the capillary border of groundwater there is a horizon with constant low moisture (close to wilting moisture), called the dead horizon of desiccation ... This mode differs in that the amount of moisture returned to the atmosphere is approximately equal to its intake 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 conventional value characterizing the maximum possible evaporation in a given area with an unlimited supply of water). For example, it is typical for 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 feed not only on precipitation, but also on the moisture of shallow groundwater. With the effusion type of water regime, groundwater reaches the soil surface and evaporates, which often leads to land 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 atmospheric precipitation exceeds the sum of evaporation and absorption of water by plants. Due to excessive moisture, a perch is formed, resulting in waterlogging of the soil. This type of water regime is typical for depressions in the relief.

Permafrost (cryogenic) type of water regime is formed on the territory of continuous permafrost. Its peculiarity is the presence at a shallow depth of a constantly frozen water-resistant horizon. As a result, despite the small amount of precipitation, the soil is oversaturated with water in the warm season.

The thermal regime of the soil is the sum of the phenomena of heat exchange 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 peculiarities 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, however, 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 has a special effect on the thermal regime of the soil.

The thermal energy of the soil participates in the phase transitions of soil moisture, being released during ice formation and condensation of soil moisture and wasted 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 solar radiation energy entering the earth's surface. On average, the annual heat balance of a given soil is equal to zero.

Daily fluctuations in soil temperature cover the soil thickness from 20 cm to 1 m, annual - up to 10-20 m. Soil freezing depends on the climatic characteristics of a given site, the freezing temperature of the soil solution, the thickness of the snow cover and the time of its fall (since the snow cover reduces cooling the soil). The depth of soil freezing rarely exceeds 1–2 m.

Vegetation has a significant effect on the thermal regime of the soil. It traps solar radiation, as a result of which the soil temperature 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 the 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 abruptly inhibited and stopped. The thermal regime of the soil has a direct impact on the growth and development of plants. An important indicator of the soil heat supply to plants is the sum of active soil temperatures (i.e. temperatures above 10 ° C, at these temperatures active vegetation of plants takes place) at a depth of the arable layer (20 cm).

Morphological characteristics of soils.

Like any natural body, the soil has a sum of external, so-called morphological characteristics, 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, new formations 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 developing all the time, the classification is being improved accordingly.

In the pre-dokuchaev period, they studied not the soil (in the modern view), but only its individual properties and aspects, therefore, the soil was classified 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 the characteristic features of soil morphology (first of all, the structure of the soil profile) - this gave him the opportunity to develop a soil classification on a completely different basis than it was done earlier.

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

Dokuchaev identified 10 soil types, and in the amended modern classifications there are more than 100.

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

Genetic soil types are subdivided into subtypes, genera, species, varieties, categories, and they are combined into classes, rows, formations, generations, families, associations, etc.

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

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

The second approach to soil classification was developed in 1960 in the United States. The American classification is not based on an assessment of the formation conditions and associated genetic characteristics of various soil types, but on the basis of easily detectable morphological features of soils, primarily on the study of some 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 territories, but such maps practically could not be compared with overview small-scale maps based on the principle of geographic and genetic classification.

Meanwhile, by the early 1960s, it had become clear that defining a strategy for agricultural food production needed a world soil map, the legend of which should be based on a classification that eliminated the gap between large and small-scale maps.

Experts from the United Nations Food and Agriculture Organization (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 discussions and agreements between various national scientific schools. As a result, a map legend was developed, which was based on a diagnostic approach to the definition of classification units of all levels, although it also took into account certain elements of the geographic-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.

Studying the patterns of spatial distribution of different types of soils is one of the fundamental problems of earth sciences.

Revealing the regularities of 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 basic patterns were identified:

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

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

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

The following main natural zones replace each other from the poles to the equator: polar zone (or zone of arctic and Antarctic deserts), tundra zone, forest-tundra zone, taiga zone, mixed forest zone, deciduous forest zone, forest-steppe zone, steppe zone, semi-desert zone, zone deserts, a zone of savannas and woodlands, a zone of variable humid (including monsoon) forests and a zone of moist evergreen forests. Each of these natural zones is characterized by completely specific 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 areas of subtypes of zonal soils are also located within the zones in parallel stripes, 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 hydromorphic soils correspond to certain zones (i.e., soils, the formation of which occurs under a significant influence of groundwater). Hydromorphic soils are not azonal, but their zoning is manifested differently than that of automorphic soils. Hydromorphic soils develop next to automorphic soils and are geochemically related to them; therefore, a soil zone can be defined as the territory of a certain type of automorphic soils and hydromorphic soils in geochemical conjugation with them, which occupy a significant area - up to 20–25% of the area of \u200b\u200bsoil zones.

Vertical soil zoning. The second regularity of soil geography is vertical zoning, 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 regular changes in climatic conditions, flora and fauna. Soil types change accordingly. In mountains with insufficient moisture, the change in vertical zones is determined by a change in the degree of moisture, as well as the exposure of slopes (the soil cover here acquires an exposure-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 is completely analogous to the horizontal zoning of soils from the equator to the poles, but later it was found that among mountain soils, along with types common both on plains and in mountains, there are soils formed only in mountainous conditions. landscapes. It was also found that the strict sequence of the vertical soil zones (belts) is very rarely 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. I.P. Gerasimov and other scientists have revealed that the manifestation of horizontal zoning is corrected by the conditions of specific regions. Depending on the influence of oceanic basins, continental spaces, large mountain barriers on the path of air masses movement, local (facies) climatic features are formed. This is manifested in the formation of the features of local soils up to the appearance of special types, as well as in the complication of horizontal soil zoning. Due to the phenomenon of facies, even within the distribution of one soil type, the soil 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 the specific features of subtypes and types of soils and the conditions of soil formation. Similar provinces of several zones and subzones are combined into facies.

Mosaicity of the soil cover. In the process of detailed soil survey and soil cartographic work, it was found that the idea of \u200b\u200bthe uniformity of the soil cover, i.e. The existence of soil zones, subzones, and provinces is rather arbitrary and corresponds only to the small-scale level of soil research. In fact, under the influence of meso- and micro-relief, variability of the composition of soil-forming rocks and vegetation, the depth of groundwater, the soil cover within zones, subzones and provinces is a complex mosaic. This soil mosaic consists of different degrees of genetically related soil areas, which form a certain pattern of the soil cover and create its structure, all components of which can only be shown on large-scale or detailed soil maps.

Natalia Novoselova

Literature:

Williams V.R. Soil science, 1949
Soils of the USSR... M., Thought, 1979
Glazovskaya M.A., Gennadiev A.N. , M., Moscow State University, 1995
Maksakovsky V.P. Geographic picture of the world... Part I. General characteristics of the world. Yaroslavl, Verkhne-Volzhsky book publishing house, 1995
Workshop on General Soil Science... Moscow State University Publishing House, Moscow, 1995
Dobrovolsky V.V. Soil geography with the basics of soil science... M., Vlados, 2001
Zavarzin G.A. Lectures on natural history microbiology... M., Science, 2003
Eastern European forests. Holocene history and modern times... Book 1. Moscow, Nauka, 2004



At the heart of geographic zoning climate change lies, and above all differences in the supply of solar heat. The largest territorial units of zonal division of the geographic envelope - geographic zones.

Natural areas - natural complexes occupying large areas, characterized by the dominance of one zonal type of landscape. 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, flora and fauna.

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

As a rule, natural zones are stretched out in the form of wide strips from west to east. There are no clear boundaries between them, the zones gradually merge into one another. The latitudinal location of natural zones is disturbed by the uneven distribution of land and ocean, relief, 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 inland. 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 with distance from the ocean and an increase in the continentality of the climate. In the mountains, natural zones change with height - high-risezonation ... Altitudinal zoning is due to climate change with upward movement. The set of altitudinal zones in the mountains depends on the geographical position of the mountains themselves, which determines the nature of the lower belt, and the height of the mountains, which determines the nature of the uppermost altitude belt 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 zones is also affected by the direction of the ridges relative to the sides of the horizon and the prevailing winds. So, 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 wet winds, the vegetation will differ from that of the opposite slope.

The sequence of changes in altitude zones in the mountains practically coincides with the sequence of changes in natural zones on the plains. But in the mountains, the belts change faster. There are natural complexes 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 islands of Eurasia. The climate is humid and hot. The air temperature is constantly high. Red-yellow ferralite soils are formed, rich in iron and aluminum oxides, but poor in nutrients. Dense evergreen forests are a source of large amounts 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 multi-tiered.

The vegetation is represented mainly by arboreal forms that form multi-tiered communities. It is characterized by a high species diversity, the presence of epiphytes (ferns, orchids), lianas. Plants have tough, leathery leaves with devices that remove excess moisture (droppers). The fauna is represented by a huge variety of forms - consumers of decaying wood and leaf litter, as well as species that live in tree crowns.

Savannahs and woodlands

Natural areas with typical herbaceous vegetation (mainly grasses) 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 the tropical zones. The climate is characterized by a more or less prolonged dry period and high air temperatures throughout the year. In savannas, red ferralite 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 builds up during the dry season.

Herbaceous vegetation with separate groups of trees prevails. Characterized by umbrella crowns, life forms that allow plants to store moisture (bottle-shaped trunks, succulents) and protect themselves from overheating (pubescence and waxy bloom on the leaves, the arrangement of leaves with an edge to the sun's rays). The animal world is characterized by an abundance of herbivorous animals, 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 bit: from hot tropical deserts to deserts of the temperate climatic 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 scarce and has specific adaptations to the arid climate: the leaves are turned into thorns, the root system greatly surpasses the aboveground part, many plants are able to grow on saline soils, bringing salt to the surface of the leaves in the form of plaque. The variety of succulents is great. Vegetation is adapted to either "trapping" moisture from the air, or to reduce evaporation, or both. The fauna is represented by forms that can do without water for a long time (store water in the form of fatty deposits), travel long distances, experience the heat, go into holes or go into hibernation.

Many animals are nocturnal.

Stiff-leaved evergreen forests and shrubs

Natural areas are located in subtropical zones in a Mediterranean climate with dry hot summers and humid, 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 waxy bloom, pubescence, usually with a high content of essential oils. This is how plants adapt to dry hot summers. The fauna is greatly exterminated; but herbivorous and deciduous forms are characteristic, there are many reptiles, birds of prey.

Steppe and forest-steppe

Natural complexes characteristic of temperate zones. Here, in a climate with cold, often snowy winters and warm, dry summers, the most fertile soils are formed - chernozems. Herbaceous vegetation predominates, in typical steppes, prairies and pampas - cereal, in dry varieties - wormwood. Almost everywhere, natural vegetation has been replaced by agricultural crops. The fauna is represented by herbivorous forms, among which ungulates are strongly exterminated, mainly rodents and reptiles, which are characterized by a long period of winter rest, and birds of prey have survived.

Broadleaf and mixed the woods

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

Taiga

Taiga is widespread in the temperate latitudes of the Northern Hemisphere in a wide strip in climates with short warm summers, long and severe winters, sufficient precipitation and normal, in some places excessive moisture.

In the taiga zone, under conditions of abundant moisture and a relatively cool summer, intensive washing of the soil layer occurs, and little humus is formed. Under its thin layer, as a result of soil washing, a whitish layer is formed, which in appearance looks like 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 and long and severe winters. With a small amount of precipitation, excessive moisture develops. The soils are peaty-gley, under them is a layer of permafrost. The vegetation cover is represented mainly by herb-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 their 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 harsh; winter and polar night dominate most of the year. Vegetation is scarce, represented by communities of mosses and crustaceans. The fauna is associated with the ocean; there is no permanent population on land.

Altitude zones

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

Table "Natural areas"

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

For 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) - formed during the transformation of the mineral part of the soil in place.
• Hydrogen accumulative - (S) - are formed in the zone of maximum accumulation of substances (readily soluble salts, gypsum, carbonates, iron oxides, etc.) brought by groundwater.
• Cow - (K) - horizons cemented by various substances (readily soluble salts, gypsum, carbonates, amorphous silica, iron oxides, etc.).
• Gley - (G) - with prevailing reducing conditions.
• Subsoil - the parent rock (C) from which the soil was formed, and the underlying underlying rock (D) of a different composition.

Solid phase of soils

The soil is highly dispersed and has a large total surface area of \u200b\u200bsolid particles: from 3-5 m2 / g for sandy to 300-400 m2 / g for clayey. Due to the dispersion, the soil has significant porosity: the pore volume can reach from 30% of the total volume in swampy 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 \u003d 1 - ρ b / ρ s

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 hypergenesis zone, most of them are unstable and disintegrate at one rate or another. Olivine, amphiboles, pyroxenes, and nepheline are among the first to be destroyed. Feldspars are more stable, making up 10-15% of the mass of the solid phase of the soil. Most often they are represented by relatively large sandy particles. Epidote, disthene, garnet, staurolite, zircon, tourmaline are distinguished by high resistance. Their content is usually insignificant, but it allows one to judge the origin of the parent rock and the time of soil formation. Quartz has the greatest stability, which wears out in several million years. Due to this, under conditions of prolonged and intense weathering, accompanied by the removal of the products of the destruction of minerals, its relative accumulation occurs.

The soil is characterized by a high content of secondary mineralsformed as a result of deep chemical transformation of the 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.

A high content of minerals-oxides and hydroxides of iron (limonite, hematite), manganese (vernadite, pyrolusite, manganite), aluminum (gibbsite), etc., also strongly affecting the properties of the soil - they are involved in the formation of a structure, a soil absorbing complex (especially in strongly 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

Ferré triangle

The soil 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 area, and this, in turn, means higher cation exchange capacity, water-holding capacity, better aggregation, but lower porosity. Heavy (clay) soils can have problems with air content, light (sandy) soils with water regime.

For a 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 characterization 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.

In the world, the determination of the mechanical composition of the soil according to the Ferret triangle is also widely used: the share of silty ( silt, 0.002-0.05 mm) particles, the second - clayey ( 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 a particular grain size distribution 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 prevail, but in most mineral soils, its amount does not exceed several 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 nonspecific substances of a known structure (lipids, carbohydrates, lignin, flavonoids, pigments, wax, resins, etc.), constituting 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 high molecular weight compounds. In Soviet and Russian soil science, they are traditionally divided into humic and fulvic acids.

Elemental composition of humic acids (by weight): 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%). 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 in the entire range (humic acids precipitate in an acidic medium). The carbon ratio of humic and fulvic acids (C gc / C fc) is an important indicator of the humus state of soils.

In the molecule of humic acids, a nucleus is isolated, consisting of aromatic rings, including nitrogen-containing heterocycles. The rings are connected by "bridges" with double bonds, which create extended conjugation chains that cause the dark color of the substance. The nucleus 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 (MM Kononova, AG Trusov), these substances are synthesized from low molecular weight organic compounds. According to the hypothesis of L. N. Aleksandrova, humic acids are formed by the interaction of high-molecular compounds (proteins, biopolymers), then they are gradually oxidized and decomposed. According to both hypotheses, these processes involve enzymes produced mainly by microorganisms. There is an assumption about the 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, the development of the microbial community. Depending only on the size of the aggregates, the yield can vary by an order of magnitude. The structure is optimal for the development of plants, in which aggregates with a size of 0.25 to 7-10 mm prevail (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. Allocate rounded-cuboid (granular, lumpy, lumpy, silty), prismatic (pillar, prismatic, prismatic) and platy (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 the illuvial, metamorphic horizons, the third - for the eluvial.

Neoplasms and inclusions

Main article: Soil neoplasms

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

Neoplasms of iron and manganese are widespread, whose migratory capacity depends on the redox potential and is controlled by organisms, especially bacteria. They are represented by nodules, tubes along the paths of roots, crusts, etc. In some cases, cementation of the soil mass with ferruginous material occurs. In soils, especially in arid and semi-arid regions, calcareous neoplasms are widespread: deposits, efflorescence, pseudomycelium, nodules, and crust formations. Gypsum neoplasms, also characteristic of arid regions, are represented by raids, druses, gypsum roses, and crusts. There are new formations of readily soluble salts, silica (dusting in eluvial-illuvially differentiated soils, opal and chalcedony interlayers and bark, tubes), clay minerals (cutans - incrustations and crusts formed during the illuvial process), often together with humus.

TO inclusions include any objects 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 to inclusions or neoplasms of coprolites, wormholes, wormholes and other biogenic formations is ambiguous.

Liquid phase of soils

State of water in soil

In soil, there is a distinction between 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 be removed only by heating, and some forms (constitutional water) by calcining the minerals. As a result of the release of chemically bound water, the properties of the body change so much that we can talk about a transition to a new mineral.

The soil retains physically bound water by surface energy. Since the value 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 composing 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 indicated. In particles with a diameter of 2 to 0.01 mm, the ability to retain physically bound water is weak. It increases on going to particles less than 0.01 mm and is most pronounced in credcolloidal and especially colloidal particles. The ability to hold physically bound water depends not only on particle size. The shape of the particles and their chemical and mineralogical composition have a certain effect. 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, its attraction of water molecules 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. 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. The soil holds loosely bound water with less force, its properties are not so sharply different from free water. Nevertheless, the force of gravity is still so great that this water does not obey the force of gravity and differs from free water in a number of physical properties.

Capillary duty cycle determines the absorption and retention in a suspended state of moisture brought by atmospheric precipitation. The penetration of moisture through the capillary pores deep into the soil is extremely slow. The permeability of the soil is mainly due to the non-capillary porosity. The diameter of these pores is so large that moisture cannot be kept suspended in them and seeps into the depths of 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, through the layers saturated with water, filtration through non-capillary wells occurs. Through cracks, shrews' passages and other large wells, water can penetrate deep into the soil, ahead of saturation with water to the value of the field moisture capacity.

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

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

Interaction with the solid phase

Main article: Soil absorbing complex

The soil can retain the substances entered into it by various mechanisms (mechanical filtration, adsorption of small particles, the formation of insoluble compounds, biological absorption), the most important of which is ion exchange between the soil solution and the surface of the solid phase of the soil. The solid phase, due to the cleavage 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, is charged predominantly negatively, therefore, the cation exchange capacity of the soil is most pronounced. Nevertheless, positive charges, which cause anion exchange, are also present in the soil.

The entire set of soil components with ion-exchange capacity is called the soil absorbing complex (AUC). The ions included in the PPK are called exchanged or absorbed. The characteristic of the AUC is the capacity of cation exchange (CEC) - the total amount of exchangeable cations of one kind held by the soil in the standard state - as well as the sum of exchangeable cations, which characterizes the natural state of the soil and does not always coincide with 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. Cations with a higher charge are preferentially 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 AUC is reflected in the formation of organomineral compounds, the structure of the soil and its acidity.

Soil acidity

Soil air.

Soil air consists of a mixture of different gases:

1. oxygen that enters the soil from atmospheric air; its content can vary depending on the properties of the soil itself (its looseness, 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 conditions of soil weathering, etc.

Living organisms in the soil

Soil is the habitat of many organisms. The creatures that live in the soil are called pedobionts. The smallest of these are bacteria, algae, fungi and unicellular organisms that live in soil water. Up to 10¹⁴ organisms can live in one m³. Invertebrates such as ticks, spiders, beetles, springtails and earthworms inhabit the soil air. They feed on plant debris, mycelium and other organisms. Vertebrates also live in the soil, one of them is a mole. He is very well adapted to living in absolutely dark soil, therefore he is deaf and practically 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 nanofauna (protozoa, rotifers, tardigrades, nematodes, etc.), the soil is a system of micro-reservoirs.
• For the somewhat larger animals breathing air, the soil appears as a system of small caves. These animals are called microfauna. The sizes of the representatives of the soil microfauna are from tenths to 2-3 mm. This group mainly includes arthropods: numerous groups of mites, primary wingless insects (collembolans, protora, two-tails), small species of winged insects, symphila centipedes, etc. They have no special tools for digging. They crawl along the walls of the soil cavities with the help of their limbs or worm-like writhing. The soil air saturated with water vapor allows breathing through the integument. Many species lack a tracheal system. Such animals are very sensitive to drying out.
• Larger soil animals, with body sizes from 2 to 20 mm, are called representatives of the mesofauna. These are insect larvae, centipedes, enchitreids, 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 the soil particles apart, or by digging new passages.
• Megafauna or soil macrofauna are large diggers, mainly mammals. A number of species spend their entire life in the soil (mole rats, mole voles, zokors, moles of Eurasia, golden moles of Africa, marsupial moles of Australia, etc.). They lay whole systems of tunnels and holes in the soil. The external appearance and anatomical features of these animals reflect their adaptability to the burrowing underground lifestyle.
• In addition to the permanent inhabitants of the soil, among the large animals one can distinguish a large ecological group of burrow inhabitants (ground squirrels, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but multiply, 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 way of life.

Spatial organization

In nature, there are practically no situations such that any one soil with properties unchanged in space extends for many kilometers. In this case, the differences in soils are due to differences in the factors of soil formation.

The natural spatial distribution of soils in small areas is called the soil cover structure (TSS). The initial unit of the SPP is the elementary soil area (EPA) - a soil formation, within which there are no soil-geographical boundaries. Genetically related EPAs alternating in space and to one degree or another 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 presented 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 Dokuchaev's principle of historicity, which implies a certain maturity of soils and the division of the profile into genetic horizons, but it is useful in understanding the general concept of soil development.

The embryonic 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 "along Veski" until the time when a noticeable differentiation of the profile on the horizons appears, and it will be possible to predict the classification status of the soil. The term “young soils” was proposed to be assigned 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 will be sufficiently pronounced for diagnosis and classification from the general point of view of soil science.

Genetic characteristics can be given even before the profile reaches maturity, with an understandable share of predictive risk, for example, “initial soddy soils”; "Young podzolic soils", "young calcareous soils". With this approach, nomenclature difficulties are naturally resolved on the basis of general principles of soil-ecological forecasting in accordance with the Dokuchaev-Jenny formula (representation of soil as a function of soil formation factors: S \u003d 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" was fixed, and the study of soil formation in these landscapes took shape in "soil reclamation". The term “technozems” was also proposed, which in fact represents an attempt to combine the Dokuchaev tradition of “-zones” with technogenic 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 filling in 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 "-zill", but a zonal soil, for example, sod-podzolic or sod-gley soil.

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

Soil classification

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

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

One of the distinctive features of the new classification is the refusal to use factor-ecological and regime parameters for diagnostics, which are difficult to diagnose and are 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 a soil to a certain taxon, using the concept of a diagnostic horizon, adopted 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. An indisputably important innovation in the 2004 classification was the inclusion of anthropogenically transformed soils in it.

The American School of Soil Science uses the Soil Taxonomy classification, which is also common in other countries. Its characteristic feature is a deep elaboration of formal criteria for assigning soils to one or another taxon. Soil names are used, constructed from Latin and Greek roots. 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 soil bureau mapped the territory of the United States at the beginning of the 20th century.

Soil classification is a system for separating soils by origin and / or properties.

• Soil type is the main classification unit, characterized by the generality of properties determined by the regimes and processes of soil formation, and by a single system of basic genetic horizons.
  • Soil subtype is a classification unit within a type, characterized by qualitative differences in the system of genetic horizons and by the manifestation of overlapping processes that characterize the transition to another type.
    • Soil genus is 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 is a classification unit within a genus, which quantitatively differs in the degree of severity 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 is a classification unit that groups soils according to the nature of the parent 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 the geographical distribution of soils - is largely determined by cosmic reasons (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, determining the energy level and hydrothermal regime of soils, and indirectly, by influencing other factors of soil formation (vegetation, vital activity of organisms, parent rocks, etc.).

The direct influence of climate on soil geography is manifested in different types of hydrothermal soil formation conditions. 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 different thermal regimes, 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 zoning and vertical zoning.

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 turnover, moisture turnover 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 things - microorganisms, animals and plants. It is also significant that in terms of their biomass, the soil (land of the Earth) is almost 700 times larger than the ocean, although land accounts for less than 1/3 of the earth's surface.

Geochemical functions

The property of different soils to accumulate differently various chemical elements and compounds, some of which are necessary for living things (biophilic elements and trace elements, various physiologically active substances), while others are harmful or toxic (heavy metals, halogens, toxins, etc.) , manifests itself on all plants and animals living on them, including humans. In agronomy, veterinary medicine and medicine, this 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, groundwater and the entire hydrosphere of the Earth. By filtering through the soil layers, water extracts from them a special set of chemical elements characteristic of soils in 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 on a huge scale produce a variety of gases -

Zone of arctic deserts. In this zone lie Franz Josef Land, Novaya Zemlya, Severnaya Zemlya, Novosibirsk Islands. The zone is characterized by a huge amount of ice and snow in all seasons. They are the main element of the landscape.

All year round, the Arctic air prevails here, the radiation balance for the year is less than 400 mJ / m 2, the average July temperatures are 4-2 ° C. The relative humidity is very high - 85%. Precipitation falls 400-200 mm, and almost all of them fall in solid form, which contributes to the emergence 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 strong winds, a large lack of moisture 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 polygonal drained plains and polar desert solonchaks in saline coastal areas. They are characterized by a low humus content (up to 1.5%), poorly expressed genetic horizons and a very low thickness. In the arctic deserts there are almost no swamps, few lakes, salt spots form on the soil surface in dry weather with strong winds.

The vegetation cover is extremely sparse and patchy; it is characterized by a poor species composition and extremely 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 crustose lichens. Hypnum mosses are common, sphagnum mosses appear only in the south of the zone in very limited quantities. Higher plants are characterized by saxifrage, polar poppy, crumbs, stellate, arctic pike, bluegrass and some others. Cereals thrive, forming hemispherical cushions up to 10 cm in diameter on a fertilized substrate near nesting gulls and burrow lemmings. At the spots of snow, an ice buttercup and a polar willow grow, reaching only 3-5 cm in height. Fauna, like flora, is poor in species; there are lemming, arctic fox, reindeer, polar bear, and ptarmigan and snowy owl are ubiquitous among birds. On the rocky shores there are numerous bird colonies - massive nesting sites of seabirds (guillemots, luriks, ivory 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: type of vegetation, fauna, climatic conditions, etc. The type and composition of the soil also directly depends on the listed factors. In addition, moisture, evaporation, and relief features affect the fertility of the land.

Soil gives life to plants, which are the beginning of ecosystem food webs. Therefore, this or that type of natural complex and climate plays a decisive role in the formation of the soil cover.

Relationship between soil and natural zones

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

Zone name	Soil type		Soil properties	Conditions of soil formation
Arctic deserts	Arctic	Very little	Infertile	Lack of heat and vegetation
	Tundra-gley		Low-power, gley layer	Permafrost, little heat, waterlogging
Taiga of the European part	Podzolic	Insignificantly	Wash, sour	Fallen needles strongly oxidize the soil, permafrost
Taiga of Eastern Siberia	Taiga-permafrost	Insignificantly	Infertile, cold	Eternal Frost
Mixed forests	Sod-podzolic	More than podzolic	More fertile	Flushing in spring, more plant residues
Broadleaf forests	Forest gray		More fertile	Mild climate, fallen leaves of trees are rich in ash elements
Steppe and forest-steppe	Chernozems, chestnut		The most fertile	Lots of plant residues, warm climate
Semi-desert	Brown, gray-brown	Less humus	Salinization of soils	Dry climate, thin vegetation
	Desert yellowish gray		Due to rare rains, salts are hardly washed out	Lack of moisture and poverty in organic matter
Stiff-leaved evergreen forests and shrubs	Brown		High fertility with sufficient moisture	The growing season lasts all year round
Rainforest	Red-yellow ferralite and red-brown	The share of humus is 3-10%	Good soil cover washing, high iron hydroxide content	High humidity, year-round high temperatures, huge plant biomass

The variety of surrounding landscapes and climates 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 under 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 soil types are arranged according to geographic zoning.

Tundra

The tundra zone, occupying about 3%, is located in the conditions of the subarctic climatic zone. The ecosystem covers 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 modest vegetation cover.

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

• sour 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 under 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 the typical tundra;
• tundra-boggy - occur in relief depressions, can form tundra salt marshes;
• soddy acidic - located in the floodplains of rivers, grasses and cereals grow on them, as a result of which these soils are relatively rich in nutrients;
• polygonal peat bogs - common in some areas of the tundra, formed during the Holocene, when there was a forest zone in these places.

The entire territory of the tundra is covered by a layer of permafrost. It is located close to the surface, as a result of which the land is highly moistened and waterlogged. Strong cooling of the soil negatively affects the processes of soil formation and vegetation development.

Podzolic

To the south of the tundra there is a huge ecosystem - taiga. The podzolic soil type is characteristic of these northern coniferous forests. Its distinctive feature is high humidity and high oxidation state due to fallen pine needles.

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

• gley-podzolic - common in the northern taiga, shrubs, dwarf trees, northern conifers grow on them;
• actually podzolic - typical for a typical taiga, where spruce, cedar, fir, pine, etc; grow on a cover of moss and lichen;
• sod-podzolic - southern taiga zone, where deciduous trees begin to mix with conifers.

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

Gray forest

This type of soil lies beneath 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 subdivided:

• light gray - the humus content is insignificant (up to 5%), according to their characteristics they are close to the soddy-podzolic soils of the southern taiga;
• gray - the share 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. 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 have a characteristic whitish bloom;
• leached - unlike the podzolized subtype, they have no 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 the chernozem processes are expressed as much as possible, the thickness of humus can take more than 120 cm;
• southern ones are widespread in the south of the steppes, in them there is 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 entirely plowed up. Only small areas in ravines, gullies, virgin fields, and also in reserves remained untouched.

Swamp

The main area of \u200b\u200bdistribution is the plains covered with tundra and taiga. Swampy areas are formed as a result of excessive moisture, as well as processes such as gleying and peat formation. The term "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 decomposition of plant residues.

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

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

Peat of lowland bogs has the most advantageous properties: it is characterized by a low degree of acidity and is saturated with minerals. Swampy soils are best formed in small bodies of water and lakes with stagnant water.

Lugovaya

Meadow soils are formed in places where meadow vegetation grows.

This soil type is divided into two subtypes:

• typical meadow - formed in the area of \u200b\u200boccurrence of groundwater at 1.5-2.5 m, under the plants of meadow zones;
• wet meadow (swampy meadow) - located in low 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%), therefore they are intensively used for agriculture.

comparison table

It contains a brief description of the natural complexes, as well as their geographic location, soil 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 value

Soil is an essential element in the formation of all living organisms on Earth. In this case, the composition of the soil is formed due to the life processes of plants and animals. But not every type of soil can give a good harvest.

What kind of soil is best for growing certain crops is written below:

1. Clay. With the addition of peat, sand and ash, it is great for growing fruit trees, shrubs, potatoes, peas, 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 loam. To increase fertility, fertilizers are applied, mulched, and green manure plants are planted. Almost all types of vegetables and fruits can also grow on it.
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, which does not require fertilization 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 on it.
6. Peat boggy. It is recommended to apply fertilizers from sand, clay, phosphorus and organic matter into it. It is good to grow berry bushes on such soil.
7. Limestone. Requires a lot of fertilizers 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 the cultivation of 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 type of soil.

1. Arctic deserts. 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 land is covered with mosses, lichens, grasses. In the south of the zone, shrubs and dwarf trees begin to appear. The soil is thin, there is permafrost.
3. Taiga. The largest ecosystem by area. Occupies most of the temperate forests. Conifers dominate: pines, spruces, fir, larch, cedar. The soil is acidic, cold and of little use 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. Broadleaved forests. Located in Europe, the Russian Plain, Asia, and in some places in South America. Oaks, ash trees, lindens, maples grow here. The soil is fertile thanks to fallen leaves and a warm climate.
6. Steppe and forest-steppe. The Russian steppes occupy a wide strip in the south of the country. On other continents, in climatic and natural conditions, African savannas, North American prairies and South American pampas are similar to steppes. Grassy plains mixed with 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, Africa, Australia. Occasionally there are plants - shrubs, cacti, cereals and herbs. The land is saline, the hot and dry climate prevents most of the plants from growing.
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, bamboos and palms coexist at the same time. A huge number of heat-loving plants grow in tropical forests.

Thus, vegetation and soil composition are interrelated: the more plants, the warmer the climate, the richer and more saturated the land 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, snowy owls, walruses, seals.

Tundra

There is already a greater variety of living organisms. Many animals move south to the forests for the winter, 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, white and brown bears, lemmings, and polar owls. There are a lot of mosquitoes and midges in the tundra due to the large accumulation of swamps.

Forest zone

Forests of a temperate climate stretch in a wide strip from the northern forest-tundra to the southern forest-steppe. The diversity of fauna also varies from north to south. Thus, in the taiga, the species composition of animals is not as diverse as in mixed and deciduous forests. But in general, the animal composition of the forest zone is approximately the same: brown bears, wolves, foxes, lynxes, elks, red deer, hares.

Steppe

Large animals have nowhere to hide in the wide and open spaces of the steppes, 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 are: leopards, tigers, elephants, antelopes, okapis, gorillas, chimpanzees, parrots, toucans, as well as a huge number of butterflies and insects.

The richest belt in vegetation

The regions with the most diverse and abundant flora and fauna are the equatorial and subequatorial climatic zones of the Earth. On ferralite red-yellow soils, multi-tiered tropical forests grow and develop. Tall trunks of palms, ficuses, chocolate, banana, iron and coffee trees are entwined with vines, mosses, ferns and orchids grow on their surface.

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

Video

This video describes the soil and plants of various natural areas.

 

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• Presentation "Strong and weak electrolytes" presentation of a lesson for an interactive whiteboard in chemistry (grade 9) on the topic Presentation on the use of electrolytes in medicine;
• Presentation on the topic: "Acids - as electrolytes" Presentation on the use of electrolytes in medicine;
• Presentation vladimir dal presentation for a reading lesson on the topic Literary presentation for grade 4;
• More about telephoto lenses;
• Creativity of Korney Ivanovich Chukovsky presentation for a reading lesson (grade 2) on the topic;
• Presentation on the topic "Biography of Paustovsky. Presentation on the topic of Paustovsky biography;
• Migratory and wintering birds presentation Migratory and wintering birds presentation for children;
• Traumatic brain injury Presentation on the topic of closed traumatic brain injury;