Soil types and their distribution table. Russian soil types

Soils

The Russian Federation is characterized by a wide variety of bioclimatic conditions, which determine the diversity of soils on its territory. In addition to differences in the specifics of the climate and modern ecosystems, the diversity of Russian soils is determined by the complexity of the geological structure and history of the upper sediment cover on the earth's surface. As a rule, each type of natural biogeocenoses corresponds to a certain type or group of soil types. Together with climatic parameters, soils determine the nature of land use in agriculture. The geographic distribution of soils is regulated by the laws of soil geography, primarily by latitudinal zonality and vertical zonality. Below is a description of the soils of the main natural zones of Russia.

Soils of the Arctic zone. The Arctic zone occupies a relatively small area in Russia: it is distributed on the islands of the Arctic Ocean, such as Franz Josef Land, Novaya Zemlya, Severnaya Zemlya, the northern part of the Novosibirsk Islands, as well as on the northern tip of the Taimyr Peninsula (Cape Chelyuskin). In the Arctic zone, soils occupy only ice-free places where lichens and mosses grow, and in some places - clumps of cereals. They thaw for 2–3 months a year to a depth of 20–30 cm. The granulometric composition of these soils is dominated by rubbly and coarse sand fractions. The content of organic carbon in soils does not exceed 1.0–1.5% in the surface horizon, the reaction of the environment is close to neutral. Soils formed on the coasts of the ocean are characterized by the accumulation of salts, in some places salt efflorescences on the surface.

Soils of the tundra and forest tundra. The tundra zone stretches along the coast of the Arctic Ocean throughout the Russian North. It is characterized by milder than the Arctic zone, climatic conditions and a relatively continuous soil and vegetation cover, which is absent only on rock outcrops (so-called rock formations) and on glaciers.

The tundra is subdivided into three subzones: arctic tundra, typical (lichen-moss) tundra, and southern (shrub) tundra.

The Arctic tundra occupies a narrow strip along the ocean coast immediately south of the Arctic zone. Spotted fissure-polygonal tundras are typical landscapes, where patches devoid of soil and vegetation cover can occupy up to 40–80% of the total area. The main areas are occupied by the so-called. arctic tundra soils. They form under shrub-herb-lichen-moss vegetation on loamy and clayey deposits of different genesis and have a thin (3–6 cm) humus-accumulative horizon, under which lies a brown-colored median horizon with bluish spots. Such coloration diagnoses gleying - the process of reduction of iron and manganese under conditions of oxygen deficiency due to prolonged saturation of the soil with moisture. For many soils of this zone, cryoturbation is typical in their profile - signs of soil mixing as a result of its freezing and thawing. The soils are characterized by a relatively high content of organic carbon in the surface horizon (2.0–3.5%) and its deep penetration into the soil, the reaction of the environment is neutral or close to neutral, and a high content of exchangeable bases, among which calcium predominates.

Typical tundra occupies vast areas in the north of the country, especially in its Asian part, and is characterized by more diverse and developed soils than the arctic tundra. A significant part of the soil cover is made up of tundra gley soils (see Gleezems), which differ from arctotundra soils in a deeper profile, thawing up to 40–100 cm, and in a more pronounced manifestation of gleying, which indicates prolonged waterlogging. The tundra soils of the European part of Russia are characterized by surface gleying, while the soils of Eastern Siberia are suprapermafrost. In contrast to the soils of the arctic tundra, the tundra gley soils of the typical tundra are characterized by an acid reaction of the medium in the upper horizon, which is replaced by a slightly acid one with depth. In addition to tundra gley soils, large areas in this zone are occupied by tundra bog soils and podburs. Tundra bog soils form on low, poorly drained relief elements. They are characterized by a constant stagnant water regime and slow decomposition of plant residues, which leads to the formation of peat on the soil surface; The thickness of the peat deposit in the tundra is, as a rule, insignificant due to the low biological productivity of tundra ecosystems. On gravelly and sandy rocks with good water permeability, podburs are formed - acidic, without signs of soil gleying with a rusty-brown horizon under moss-shrub vegetation. common feature The soil cover of the tundra is its variegation and complexity, i.e., the frequent alternation of small spots of various soils and bare areas devoid of vegetation, which is associated with harsh climatic conditions. The fertility of tundra soils is low, but mosses and lichens growing on them serve as food for reindeer.

The southern shrub tundra, turning into forest tundra to the south, is characterized by a wide distribution of shrub thickets in river valleys. In the European part of Russia, these thickets consist of polar willow, bushy alder, and in the Far East they are represented mainly by dwarf pine. The soils of the southern tundra are generally similar to the soils of the typical tundra, but the thickness of the active layer and, accordingly, the thickness of the soil profile is greater here.

The forest-tundra, which receives more heat than the more northern zones, is characterized by the intrusion of sparse and oppressed forest stands into the treeless tundra. This leads to the formation of gley-podzolic soils under these conditions, which predominate in the soil cover of the northern taiga. In these soils, against the background of gleying, the removal of fine clay particles from the upper soil horizons down the profile also occurs. Podburs and dwarf podzols predominate on rocks of light granulometric composition.

Soils of the taiga-forest zone. Traditionally in Russia, the taiga zone is divided into northern, middle and southern taiga.

This is true for most of the territory of Russia, except for Western Siberia, where there is no clear boundary between the northern and middle taiga, both in geobotanical and soil terms. The soil cover varies greatly in the European and Asian parts of the country.

The taiga of the European territory of Russia is characterized by the formation of soils of the podzolic series, in which the removal of silty material from the upper horizons to the middle horizons of the soil occurs. Due to this process, a bleached horizon with a lighter granulometric composition is formed in the upper part of the profile. The middle horizon (horizon B) is enriched in clayey material, which forms films and streaks on soil aggregates and in pores. The clay-enriched (textural) horizon is characterized by yellowish-brown or reddish-brown colors, compactness, and a well-defined prismatic structure.

In the northern taiga, with a low amount of solar heat and excessive moisture, gleying is observed in the profiles of the gley-podzolic soils formed here, associated with moisture stagnation in the upper horizons. Peat bog and gleyed soils are also present in the soil cover. Taiga gleyozems are represented by rather diverse soils, the common feature of which is either gleying of the entire profile or the presence of a pronounced gley horizon lying directly under the peaty forest litter or peat surface horizon. Mineral horizons of gleyzems on loamy rocks are usually structureless, waterlogged, with clear signs of permafrost deformations of the soil profile. Illuvial-humus and humus-ferruginous podzols are common on sandy and gravelly rocks. Their feature is the presence of a clearly defined bleached podzolic horizon and a dark or rusty-brown humus-ferruginous horizon underlying it. Although podzolic soils and podzols have similarities and therefore were previously included in the same type, these two groups of soils differ significantly both in the processes that form them, and in properties and use.

For vast areas of the middle taiga, podzolic soils are most typical. They form here under spruce, spruce-fir and mixed spruce-birch forests on loamy deposits. Due to the insignificant participation of herbaceous vegetation in the ground cover of the middle taiga forests, in typical podzolic soils there is no sod and humus horizon. Directly under the forest floor lies a light, slightly colored so-called. acidic podzolic horizon with dripping humus.

In the soil cover of the southern taiga mixed coniferous-deciduous forests, soddy-podzolic soils predominate, in the profile of which there is both a humus-accumulative and a clarified podzolic horizon (see the article Podzolic soils). On loamy rocks, they contain 3–5% humus(its content decreases rapidly with depth). These soils are characterized by an acid reaction of the soil solution, while the acidity is maximum in the forest litter and in the upper mineral soil horizons.

Soddy-podzolic soils form the main fund of arable lands in non-chernozem regions and, with an appropriate fertilizer system, are successfully used in agriculture for growing a variety of grain, vegetable, fruit and berry and fodder crops.

Podzolic soils are also common in a number of regions of Siberia, but on the whole these soils are not predominant in the taiga of the Asian part of Russia. In Central and Eastern Siberia, taiga permafrost soils (cryozems) are widespread, the profile of which consists of peaty forest litter, a thin humus or coarse-humus horizon, turning into a grayish-brown horizon mixed as a result of freezing and thawing; the lower part of the soil profile is saturated with moisture, thixotropic when wet, i.e., liquefies under mechanical action, structureless. The depth of summer thawing does not exceed 1 m. The permafrost-taiga pale soils of the Central Yakut lowland in Yakutia are peculiar. Here they occupy large areas under larch forests and are characterized by a poorly differentiated soil profile. Under the upper humus horizon there is a light, yellowish-brown horizon, gradually turning into a loess-like carbonate loam. Soil reaction is neutral or slightly acidic in the upper horizons and slightly alkaline in the lower ones. With proper reclamation and fertilization, they are suitable for growing cereals, vegetables and herbs.

On mineralogically rich sandy rocks in well-drained conditions, taiga podburs are formed without signs of gleying and podzolization. They are distinguished by the presence of peaty forest litter, directly under which lies a brown illuvial-ferruginous-humus horizon, gradually turning into a parent rock. There is no lightened podzolic horizon in their profile.

In the Middle Urals, in the foothills of the Altai and Sayan Mountains, in the Far East, under the southern taiga, partially and middle taiga forests, peculiar brown taiga soils are common. The profile of these soils is weakly differentiated into genetic horizons. They are distinguished by a high content of humus (up to 7–15%) and mobile iron compounds in the upper horizon, and an acidic reaction of the soil solution. In landscapes with difficult drainage, which contributes to the stagnation of surface waters and the development of the eluvial-gley process, gleyed brown taiga soils are formed.

The volcanic ocher layered ash soils of Kamchatka are even more distinctive. characteristic feature their genesis is the periodic interruption of soil formation by the fallout of new portions of volcanic ash. As a result, their profile consists of elementary profiles superimposed on each other, in each of which organogenic and median horizons are distinguished; the latter can be dyed with humus into coffee tones or iron hydroxides into ocher. Volcanic soils are distinguished by a light granulometric composition, high water permeability, and the predominance of weakly crystallized aluminosilicate and ferruginous minerals. The reaction of volcanic ocher soils is acidic, the cation uptake capacity is low. The use of these soils in forestry is effective.

Huge areas in the northern regions of Russia, especially in Western Siberia and the Far East, are occupied by marsh soils. They are excessively wet throughout the year and therefore are characterized by slow decomposition of plant residues, which leads to the formation of a peat layer.

Peat soils are subdivided according to the thickness of the peat deposit, according to the botanical composition of peat, according to the content of the mineral part (ash part) and according to the degree of decomposition of organic residues. The bog lowland and highland peat soils are fundamentally different. Lowland peatlands are formed when flooded with mineralized groundwater, they have a high ash content, peat is composed mainly of sedges and wood, the degree of decomposition of organic residues is high, and the reaction of the medium is slightly acidic or neutral. Raised peat soils are formed when saturated with low-mineralized rainwater: the ash content of peat is low, it is composed mainly of weakly decomposed sphagnum mosses, and the reaction of the medium is acidic.

Bog lowland soils can be used in agriculture only after drainage reclamation, bog highland soils are suitable only for forestry. Although the soil types prevailing in the northern and middle taiga zones are practically unsuitable for agricultural use, their importance is extremely high, since they serve as the basis for the growth and development of forests. Peat-bog soils and peat deposits in these natural zones largely determine the hydrological regime of the northern territories, store huge amounts of carbon and nitrogen stored in the form of organic matter.

On carbonate rocks in Central and Eastern Siberia, soddy-calcareous soils are common (see Rendziny) with a slightly acidic or slightly alkaline reaction, a high humus content (up to 5–12%); they are rich in plant nutrients, but, as a rule, have a small thickness and are leached or podzolized to varying degrees. Under conditions of a humid cool climate in the subzones of the northern and middle taiga, humus-calcareous soils are formed on carbonate rocks, which differ from soddy-calcareous soils by an even higher content of humus (up to 20% or more).

In floodplains and river deltas under water meadows, alluvial soils, formed under conditions of periodic flooding and accumulation of river sediments (alluvium). Vast areas are occupied by alluvial soils along the great rivers of Siberia and the Far East: the Ob, Yenisei, Lena and Amur. They are diverse in regime, structure and properties, depending on the composition of alluvium, location in one or another area of ​​the river floodplain, as well as on the geographical location of the floodplain itself. In the forest zone, the soils of the river floodplains are characterized by an acid reaction, a relatively high content of organic matter, gleying in the soil profile of the low floodplain, and swamping in the near-terrace floodplain.

Broad-leaved and coniferous-broad-leaved forests of the south of the Far East, as well as the mountain slopes of the Caucasus, Altai and Sikhote-Alin, are characterized by brown soils with a weak differentiation of the soil profile and brown color, which is created due to the accumulation of iron oxides and hydroxides. The reaction is slightly acidic to neutral. The humus content in the upper, usually well-structured horizon is up to 10% or more. The moderately warm and humid climate determines the richness and diversity of soil biota. Under different conditions of relief and composition of parent rocks, brown soils show signs of podzolization or surface gleying. On leveled, poorly drained areas, there are podbels, characterized by a sharp differentiation of the soil profile: under the humus horizon there is a white or light gray horizon with a lumpy-platy structure and an abundance of ferruginous-manganese nodules.

Almost all soils of the taiga-forest zone are characterized by low natural fertility and require the application of organic and mineral fertilizers, including liming to reduce soil acidity. In the northern and middle taiga, the main direction in agriculture is dairy and meat animal husbandry, so the soils are used for growing perennial grasses and for pastures. Vegetable growing is successfully developing in some places. In the southern taiga, the use of soils in agriculture is expanding significantly: crops such as rye, oats, barley, and buckwheat are cultivated. The main problems in the development and use of soils in the taiga zone are their acidification in the absence of regular liming, depletion with insufficient fertilization, flooding in violation of the hydrology of groundwater, and water erosion. Drained peat soils are characterized by accelerated depletion of peat.

Gray forest soils are traditionally subdivided according to an increase in humus content and a decrease in podzolization into light gray, gray and dark gray forest soils. The entire type of gray forest soils is characterized by a higher humus content compared to soddy-podzolic soils, from 2–3% in light gray to 8% or more in dark gray soils, and a nutty structure, for which they were previously called walnut lands. Grey, especially dark grey, forest soils are fertile. They grow winter and spring wheat, sugar beets, corn, potatoes, flax, etc. To preserve and increase the fertility of gray forest soils, it is necessary to combat water erosion, grass planting, and the systematic use of organic and mineral fertilizers, taking into account significant differences in the bioclimatic conditions of different provinces and regions of the forest-steppe zone.

In the forest-steppe and steppe natural zones, large areas fall on chernozems, deep dark-colored humus soils. Chernozems are characterized by a neutral reaction, a high absorption capacity, and favorable agrophysical properties, due to a large extent to the water-resistant cloddy-granular structure of the humus part of the profile. They are very diverse and are divided according to the zonal principle into forest-steppe (podzolized, leached, typical) and steppe (ordinary and southern). Typical chernozems are characterized by a dark, almost black color, a high content of humus (up to 10–12%), a large thickness of the humus horizon, reaching 80–100 cm or more, a gradual decrease in the amount of humus down the profile, and the presence of a horizon with various forms of newly formed calcium carbonates. Podzolized and leached chernozems form large areas north of typical ones and are distinguished by weak eluvial-illuvial differentiation of the profile in terms of clay content and a decrease in the level of occurrence of the carbonate horizon. The loamy and clayey plains of the steppe zone are dominated by ordinary and southern chernozems, which have a humus horizon 40–80 cm thick; carbonate neoplasms are represented by white-eyed, weakly cemented carbonate concretions in the form of rounded white spots - eyes 1–2 cm in diameter. The humus content is 5–8% in ordinary and 3–6% in southern chernozems. According to provincial features, i.e., according to the forms of release of carbonates, reflecting the water regime, chernozems are divided into mycelial-carbonate, cryogenic-mycelial, farinaceous-carbonate, etc.

In Ciscaucasia, on the Azov-Kuban Plain, ordinary and southern micelle-carbonate chernozems are common. They are characterized by a large thickness of the humus horizon (up to 120 cm or more), carbonates appear in the upper part of the humus horizon or from the surface. In the steppe Crimea on loess, southern chernozems and micellar-carbonate chernozems are developed; in the west of the peninsula and at the foot of the northern slopes of the Crimean mountains, residual-carbonate chernozems are widely represented on dense carbonate rocks, and on the Kerch Peninsula, on saline clays, merged chernozems are widespread.

Among the chernozem soils, along low relief elements and with a close occurrence of groundwater (2–5 m), meadow-chernozem and chernozem-meadow soils are located. Meadow-chernozem soils are even darker than chernozems; they differ more power humus layer and gleying of the lower horizons. In contrast to them, chernozem-meadow soils are characterized by more intense gleying, a higher level of groundwater, and a lower thickness of the humus layer. Meadow-chernozem soils are highly fertile, with the exception of saline and solonetzic soils.

The dry steppe zone is dominated by chestnut soils, which contain less humus than chernozems: from 2 to 5%. In addition, their humus horizon is less thick (from 15 to 50 cm) and the carbonate horizon lies more highly; gypsum appears at the bottom of the profile. They are often solonetzic and compacted.

Chestnut soils are subdivided into subtypes according to the content of humus and a number of other properties into dark chestnut, chestnut, and light chestnut soils, the latter occurring mainly in semi-deserts. Dark chestnut and chestnut soils have been plowed over a large area and used for growing grain crops.

Among chestnut soils along relief depressions there are meadow-chestnut soils, which differ from chestnut soils only in greater humus content and better moisture supply. Meadow-chestnut soils most often form complexes with chestnut soils, salt licks and salt marshes.

In the steppe and dry-steppe zones, and to a lesser extent in the forest-steppe, significant areas are occupied by saline soils containing easily soluble salts in the surface horizon or throughout the profile; to an even greater extent, salinization processes are manifested in semi-deserts.

The processes of salt accumulation in soils are most pronounced in solonchaks. These soils contain more than 1–2% of easily soluble salts in the surface horizon. According to the composition of salts, solonchaks are chloride, sulfate, soda and mixed (chloride-sulfate, sulfate-chloride, etc.), and according to the composition of cations - sodium, magnesium, calcium.

The agricultural use of solonchaks is possible only if radical reclamation is carried out, and the most effective is reclamation leaching with the removal of salts from the soil and their removal to the drainage system.

Solonchak soils differ from solonchaks in their lower content of easily soluble salts. They are divided into strongly, medium and slightly saline. Salt soils are adjacent to solonetzes - alkaline soils that do not contain easily soluble salts or contain them not in the upper horizons, but at a certain depth. The alkaline reaction is due to the high content of exchangeable sodium in soils. Their upper humus-accumulative horizon is replaced by a columnar, very dense solonetzic horizon enriched in clay with an alkaline reaction; at the bottom, it passes into a subsolonetzic nutty horizon with carbonates and gypsum. Salt licks are distributed mainly in dry semi-desert steppes, as well as in the steppe and even forest-steppe zones. Most often they are found in the composition of the so-called. solonetzic complexes, including solonchak, solonchak, meadow, chestnut soils or chernozems.

Solonets and solonetsous soils are genetically related to solods. They are formed under the influence of moisture stagnation and leaching of salts from the soil profile. Malts are common under birch pegs in the forest-steppe of Western Siberia; they are also found in saucer-shaped depressions in the steppes and forest-steppes. A characteristic feature of malt is a sharp differentiation of the soil profile into genetic horizons with the obligatory inclusion of a light horizon with iron-manganese nodules and the presence of a dense brown-brown illuvial horizon under it. Light solodized horizons are characterized by a weakly acidic reaction, and residual accumulation of silica is also noted in it.

The soils of the forest-steppe, steppe and dry-steppe zones are the basis of the country's soil fund for the needs Agriculture, which is associated with both optimal climatic conditions and high natural soil fertility. The soils are used for winter and spring wheat, corn, sunflower, soybeans, vegetable and horticultural crops. The development of chernozems is maximum: almost all soils of the chernozem zone, with the exception of settlements, inconveniences and specially protected areas, are plowed up and used in agriculture. Chestnut soils are also predominantly plowed; partially chestnut soils are used for grazing. In the steppe and dry steppe zones, both chernozems and chestnut soils require drip irrigation in places. The development and agricultural use of solonetzes is possible, but it requires a whole system of reclamation and agrotechnical measures, including gypsuming, special deep plowing, followed by grass sowing.

Semi-desert soils. In Russia, semi-deserts occupy a relatively small area, mainly within the Caspian lowland. There, on ancient alluvial sands and loamy loess-like deposits, brown desert-steppe soils(semi-desert) - low-humus, thin, dense and often solonetzic. The amount of humus in them rarely exceeds 1.5–2.0%, the thickness of the humus horizon is no more than 10–15 cm, below there is a dense brownish-brown horizon, which in turn is replaced by an illuvial carbonate one; at a depth of 80–100 cm there are accumulations of gypsum, under which readily soluble salts are found. In relief depressions, under forb-grass vegetation, meadow-brown soils are found, which are more humus-rich. The soil cover of the semi-desert zone is characterized by variegation with frequent alternation of soils - light chestnut, brown desert-steppe, solonetzes and solonchaks.

The soil cover of the semi-desert zone is favorable for the development of grazing livestock, and along the depressions with meadow-chestnut and meadow-brown soils - melon growing. When irrigating them, careful monitoring of the state of the soil is necessary due to possible development their secondary salinity. Overgrazing leads to rapid degradation of pastures, desertification and overconsolidation of the upper soil horizons.

subtropical soils. Subtropical soils are represented in Russia by yellow soils and brown soils. Zheltozems occupy a narrow strip of land along the Black Sea coast in the Tuapse-Sochi region; they are characterized by an increased content of mobile oxides of iron, aluminum and manganese. Their profile includes a leached yellow horizon with an acid reaction of the medium, turning downwards into an illuvial light yellow horizon with a large amount of ferruginous-manganese nodules.

Zheltozems are used for growing tea, citrus, fruit and vegetable crops, but they need organic and mineral fertilizers, as well as protection from water erosion.

Brown soils are common in mountainous Dagestan and in the south of the Crimean Peninsula under dry sparse forests and thickets of shrubs with grassy cover in a warm and dry subtropical climate. They distinguish between a humus horizon (brownish-gray in color with a lumpy-granular structure, contains 4–6% humus), a transitional brown-brown lumpy-nutty clayey horizon, and a lighter horizon with calcium carbonate release in pores.

Brown soils are used for orchards and vineyards and need protection from water erosion.

Mountain soils. Mountain soils occupy more than 1/3 of the total area of ​​the country. These include the soils of the mountainous territories of the Crimea, the Caucasus, the Urals, Altai, Eastern Siberia and the Far East. The soil cover of the mountains is characterized by high complexity. Compared to the flat mountainous soils, the vertical profile is thinner, well drained, high gravelly and stony. For the soil cover of mountains, an abundance of soils disturbed as a result of slope processes, such as landslides, landslides, mudflows, surface and gully erosion, is typical. Most mountain soils can be assigned to the corresponding soil types formed on the plains. Some types can be considered as specifically mountainous: for example, mountain-meadow and mountain meadow-steppe soils have no analogues on the plains. Mountain-meadow soils are formed in a humid climate under a well-developed herbaceous cover. They have developed soddy and humus horizons (humus content is up to 20%) with a lumpy-granular structure; these soils are characterized by an acidic reaction throughout the profile. Mountain meadow-steppe soils are drier, they have less humus, they are neutral.

Mountain forest soils are of great importance in the country's forestry, as well as in environmental protection. When mountain forests are cut down, their soil cover is rapidly eroded, which entails drifts and pollution of rivers, floods in adjacent territories, and violation of the hydrological regime in large areas of river basins. Mountain-meadow and mountain meadow-steppe soils are used in pasture animal husbandry. They need anti-erosion protection.

Anthropogenically transformed and anthropogenic soils. The natural diversity and condition of soils are significantly affected by industrial, mainly agricultural, human activities. The structure, properties, regimes of soils change and are transformed to varying degrees, artificial soils are created, etc. Specialists of the Soil Institute. VV Dokuchaeva developed a new classification of soils in Russia (2004) taking into account the degree of their anthropogenic transformation. In this classification, those soils that have been significantly altered by man, but have not lost the features of the original natural soils, are distinguished as anthropogenically transformed. The name of such soils is formed by adding the component "agro-" to the names of types of natural soils; for example, agropodzolic, agrochernozems, etc. If the natural soils are so changed that they do not retain typical features or they are completely created artificially, then they are classified as anthropogenic. This agrozems(soils completely changed in the process of cultivation), stratozems (bulk soils), etc.

Patterns of soil distribution. In the distribution of soils on the territory of Russia, there are geographical patterns associated with the combined effect of bioclimatic and geological and geomorphological factors of soil formation. These patterns are reflected in the system of soil-geographical zoning Russian Federation(Dobrovolsky, Urusevskaya, 2006). In accordance with this system, polar, boreal, subboreal and subtropical soil-bioclimatic zones are distinguished on the territory of the country, and within them - soil-bioclimatic regions and facies, soil zones, subzones and provinces. In the direction from north to south, zones of arctic and tundra soils, podzolic taiga, gray forest, forest-steppe and steppe chernozems, chestnut dry steppe, brown semi-desert, subtropical brown and yellow soils are distinguished.

On the territory of Russia, according to the degree of climate continentality, 4 soil-bioclimatic facies are clearly distinguished: European temperate continental, West Siberian continental, East Siberian extracontinental and Far Eastern monsoon. The territories of these facies are also so different in other natural features, such as relief, parent rocks, and geological history, that they can be considered not only as special bioclimatic facies, but also as special soil-geological countries.

The totality of the influence of bioclimatic and geological-geomorphological factors in each of the identified facies, including segments of latitudinal soil zones, determines the characteristics of the soils and soil cover structures common in them.

The European temperate continental facies is characterized by a clearly defined latitudinal zonal structure of the soil cover; The West Siberian continental facies differs from it in a much wider distribution of gley, bog, peat and peat-gley soils in the taiga zones, meadow, meadow-chernozem, solonetsous, solodized and solonchak soils in the forest-steppe and steppe zones. The East Siberian extracontinental facies is characterized by the ubiquitous distribution of permanently frozen soils and related cryogenic processes in soils. The latitudinal zonality of the soil cover is weakly expressed in it. Under conditions of mountainous relief, various thin gravelly tundra and taiga permafrost soils predominate on dense sedimentary and massively crystalline rocks. On the weathering products of traps and on carbonate rocks, non-podzolized soils such as soddy-calcareous, taiga podburs, granulozems with a structure in the form of rounded granules, soils humus and enriched with mobile iron compounds without signs of podzolization are formed. The Far Eastern monsoon soil-bioclimatic facies is characterized by a great variety of soils formed under the conditions of plain and mountain soil formation. Due to the meridional elongation of the territory of this facies along the Pacific coast from Chukotka to the south of Primorsky Krai, the latitudinal zonality of soils is clearly expressed, but in the form of relatively small segments of the soil-geographic zones of the tundra, northern, middle, and southern taiga, and coniferous-deciduous forests. A common feature of the soils of the Far Eastern monsoon facies, both in the north and in the south, is their high humidity; therefore, tundra-bog, peat-bog, soddy-gley, brown-taiga gley, podbel, meadow-bog, meadow-chernozem-like ("chernozems of the Amur prairies") soils are widespread here.

A unique soil province is the Kamchatka Peninsula, where soil formation is carried out under conditions of active volcanic activity.

Latitudinal bioclimatic zonality is manifested in the geography of the soil cover not only in the form of flat soil zones, but also in the different structure of the vertical zonality of mountainous countries, depending on their geographical location. For example, the vertical zoning system of the Northern Urals is represented by only three altitudinal belts: the lower northern taiga dark coniferous zone with gley-podzolic soils and taiga podburs, the middle belt of tundra-gley and tundra podburs, and the upper bald belt of primitive mountain soils and stony placers. In the structure of the vertical zonality of the Middle Urals in the lower zone under the middle taiga spruce and spruce-fir forests, podzolic soils predominate, on average - brown taiga; higher up, they give way to mountain-meadow soils, and then to tundra podburs. The vertical zonality of the Southern Urals is represented by six vertical belts. The lower belt at the southern end of the mountain range is formed by forest-steppe with gray forest soils, among which leached chernozems appear along intermountain depressions and slopes of southern exposure. Above is a belt of broad-leaved forests with gray forest soils, which, as the absolute height increases and humidity increases, is replaced by a coniferous-broad-leaved belt with brown soils, and then a belt of dark coniferous forests with brown-taiga mountain soils; even higher is the belt of mountain meadows with mountain meadow soils. At a height of approx. At 1500 m, mountain meadows turn into mountain tundra with tundra podburs and tundra peaty-gley soils (see Fig. 1).

The specifics of the vertical zonality of soils in mountains depends not only on the latitude of the area, but also on the location of the mountain range in relation to the prevailing direction of atmospheric circulation, slope exposure, and other factors. So, on the western Black Sea slope of the Greater Caucasus in the Sochi-Tuapse region, the lower mountain belt is represented by a humid subtropical landscape with yellow earth soils, passing higher into the belt of broad-leaved and coniferous-broad-leaved forests on brown soils. On the eastern part of the slope of the Greater Caucasus to the Caspian Sea, the lower belt is represented by various dry forests and shrubs of the Mediterranean type on mountain-brown soils, even higher - mountain-meadow and mountain-steppe soils. Rice. 2 illustrates the influence of exposure on the structure of the vertical zonality of the Tannu-Ola Ridge (Republic of Tyva).

Along with the geographical patterns of soil distribution, which are mainly determined by bioclimatic factors, the geological and geomorphological conditions of soil formation are no less significant. They determine the quantitative relationships and spatial arrangement of plain and mountain soils, the separation of mineralogical and geochemical soil provinces and geological and geomorphological soil districts and regions, the granulometric composition of parent rocks and soils, and the formation of special lithogenic soil types. The latter are formed in those cases when parent rocks have a decisive influence on the genesis and properties of soils. These are sod-calcareous soils (rendzins) found in different bioclimatic zones, ocher volcanic soils formed under the direct influence of volcanic ash.

The characteristics of Russian soils are given in accordance with the legend of the new Soil Map of Russia (2017, scale 1:15,000,000).

Climatic conditions in different regions of the world vary considerably. As a result of these differences, various different types soils, each of which has its own agrotechnical characteristics.

Soil structure, fertility and origin determine the main characteristics that allow organizing soil classification.

In the classification of soils, it is customary to distinguish several nested structural units: type, subtype, genus, species, variety, and category.

Soil types and their characteristics.

The main soil types are represented by the following variations:

• Soils of the tundra zone.
• Soils of the taiga-forest zone.
• Soils of the forest-steppe zone.
• Soils of the steppe zone.
• Soils of the dry steppe zone.
• Soils of the semi-desert zone.
• Soils of dry subtropics.
• Soils of humid subtropics.
• intrazonal soils.
• Soils of river floodplains.

What are the characteristics and features of the main soil types?

1) Soils of the tundra zone.

The main soil type in this climatic zone is tundra-gley. Formed at low temperatures, with a small amount of precipitation. Evaporation of moisture is negligible due to low temperatures. Because of this, there is an excess of water on the soil surface.

The depth of soil heating is low, as a result, soil formation processes take place only in the upper layers of the soil, and permafrost is located at a greater depth.

Vegetation is poorly developed on tundra-gley soils. These are mainly dwarf shrubs and trees, lichens, mosses. There are some types of cereals. There are no forests in the tundra zone, which is hidden in the very word "tundra" - in translation "forestlessness".

Excessive moisture content in tundra-gley soils in combination with low temperatures has a depressing effect on the vital activity of microorganisms. The humus layer is thin, peat accumulates over time.

2) Soils of the taiga-forest zone.

There are podzolic, soddy-podzolic and gley-podzolic soils.

The climate is moderately humid and moderately cold. A large number of forests and swamps. Soils are mostly acidic, with high humidity. Humus content is low.

3) Soils of the forest-steppe zone.

They are subdivided into gray forest, brown forest, podzolized and leached chernozems.

The climate is moderately humid and moderately warm. The amount of precipitation is negligible. Forests alternate with steppe expanses. The humus content is quite high, the soils have good fertility.

4) Soils of the steppe zone.

The traditional soils for this zone are chernozems.

The climate is characterized by warm summers and not very cold winters. Precipitation is average. Most of the territory is flat.

The humus horizon has an impressive depth, but a good supply of soil moisture is required to achieve high yields.

5) Soils of the zone of dry steppes.

The main soils of the dry steppes are chestnut.

The climate is arid, with low rainfall. The relief structure is flat.

6) Soils of the semi-desert zone.

Represented by brown arid soils.

The climate is very arid, with low rainfall. The relief consists mainly of plains, there are mountains.

7) Soils of dry subtropics.

Traditional soils are serozems.

The climate is dry and hot. The relief is represented by plains and foothills.

8) Soils of humid subtropics.

For this zone, the most common soils are krasnozems. The climate is warm, with high humidity and high level rainfall, the temperature is stable throughout the year.

The relief is low mountains and foothills.

The amount of humus is not very large. Often there is a deficiency of phosphorus and nitrogen in the soil.

9) Intrazonal soils.

Usually the climate is arid and very warm, and the relief is flat.

The fertility rate is very low.

10) Soils of river floodplains.

A feature of floodplain soils is that they are often flooded when nearby rivers flood. There are alluvial (floodplain) soddy, marsh and meadow soils.

The main types of soils in Russia.

In Russia, the most common soils are:

• Soils of the tundra zone.
• Soils of the taiga-forest zone.
• Soils of the forest-steppe zone.
• Soils of the steppe zone.
• Soils of the dry steppe zone.
• Soils of the semi-desert zone.

The Arctic land is the islands and narrow sections of the mainland coasts of Asia and North America.

The Arctic zone is characterized by harsh climatic conditions of the Arctic climatic zone, short cold summers and long winters with very low air temperatures. The average monthly temperature in January is -16 ... -32 ° С; July - below + 8 ° C. This is a permafrost zone, the soil thaws to a depth of 15–30 cm. There is little precipitation - from 40 to 400 mm per year, however, due to low temperatures, precipitation exceeds evaporation, so the plant communities of the Arctic tundra (mainly mosses and lichens with the addition of some flowering plants) are in conditions of balanced, and sometimes even excessive moisture. The phytomass of arctic tundra ranges from 30 to 70 c/ha, polar deserts – 1–2 c/ha.

The most common type of automorphic soils in the Arctic is arctic-tundra soils. The thickness of the soil profile of these soils is due to the depth of seasonal thawing of the soil-ground layer, which rarely exceeds 30 cm. The differentiation of the soil profile due to cryogenic processes is weakly expressed. In soils formed in the most favorable conditions, only the plant-peaty horizon (A 0) is well expressed and the thin humus horizon (A 1) is much worse ( cm. SOIL MORPHOLOGY).

In arctic-tundra soils, due to excessive atmospheric moisture and a high-lying permafrost surface, high humidity is maintained all the time during a short season of positive temperatures. Such soils are weakly acidic or neutral (pHot 5.5 to 6.6) and contain 2.5–3% humus. In relatively quickly drying areas with a large number of flowering plants, soils with a neutral reaction and a high content of humus (4–6%) are formed.

The landscapes of the Arctic deserts are characterized by salt accumulation. Salt efflorescence is frequent on the soil surface, and in summer, as a result of salt migration, small brackish lakes can form.

Tundra (subarctic) zone.

On the territory of Eurasia, this zone occupies a wide strip in the north of the continent, most of it is located beyond the Arctic Circle (66° 33° N), however, in the northeast of the continent, tundra landscapes extend much further south, reaching the northeastern part of the coast of the Sea of ​​Okhotsk (approximately 60° N). In the Western Hemisphere, the tundra zone occupies almost all of Alaska and a vast area of ​​northern Canada. Tundra landscapes are also common on the southern coast of Greenland, in Iceland, and on some islands in the Barents Sea. In places, tundra landscapes are found in the mountains above the forest line.

The tundra zone belongs mainly to the subarctic climatic zone. The climatic conditions of the tundra are characterized by a negative average annual temperature: from -2 to -12 ° C. The average July temperature does not rise above +10 ° C, and the average January temperature drops to -30 ° C. The duration of the frost-free period is about three months. Summertime is characterized by high relative air humidity (80–90%) and continuous sunlight. The annual amount of precipitation is small (from 150 to 450 mm), but due to low temperatures, their amount exceeds evaporation.

Somewhere on the islands, and somewhere everywhere - permafrost, the soil thaws to a depth of 0.2–1.6 m. The location of dense frozen soil close to the surface and excessive atmospheric moisture causes waterlogging of the soil during the frost-free period and, as a result, its waterlogging. The proximity of frozen soils greatly cools the soil layer, which hinders the development of the soil-forming process.

The composition of the tundra vegetation is dominated by shrubs, shrubs, herbaceous plants, mosses and lichens. There are no tree forms in the tundra. The soil microflora is quite diverse (bacteria, fungi, actinomycetes). There are more bacteria in tundra soils than in arctic soils - from 300 to 3800 thousand per 1 g of soil.

Among the soil-forming rocks, various types of glacial deposits predominate.

Above the surface of permafrost strata, tundra-gley soils are widespread; they are formed under conditions of difficult drainage of groundwater and oxygen deficiency. They, like other types of tundra soils, are characterized by the accumulation of weakly decomposed plant residues, due to which a well-defined peaty horizon (At) is located in the upper part of the profile, consisting mainly of organic matter. Below the peaty horizon there is a thin (1.5–2 cm) humus horizon (A 1) of brown-brown color. The humus content in this horizon is about 1–3%, and the reaction is close to neutral. Under the humus horizon lies a gley soil horizon of a specific bluish-gray color, which is formed as a result of restoration processes under conditions of water saturation of the soil stratum. The gley horizon extends to the upper surface of the permafrost. Sometimes, between the humus and gley horizons, a thin spotted horizon with alternating gray and rusty spots separates. The thickness of the soil profile corresponds to the depth of the seasonal thawing of the soil.

Agriculture is possible in some areas of the tundra. Around major industrial centers vegetables are grown: potatoes, cabbage, onions, in greenhouses - many other crops.

Now, in connection with the active development of the mineral wealth of the North, the problem of protecting the nature of the tundra, and, first of all, its soil cover, has arisen. The upper peaty horizon of tundra soils is easily disturbed and takes decades to recover. Traces of transport, drilling and construction machines cover the surface of the tundra, contributing to the development of erosion processes. Disturbance of the soil cover causes irreparable damage to the entire unique nature of the tundra. Strict control of economic activity in the tundra is a difficult but extremely necessary task.

Taiga zone.

Taiga-forest landscapes form a vast belt in the northern hemisphere, stretching from west to east in Eurasia and North America.

Taiga forests are located in the temperate climate zone. The climatic conditions of the vast territory of the taiga belt are different, but, in general, the climate is characterized by rather large seasonal temperature fluctuations, moderately cold or cold winters (with an average January temperature of -10 ... -30 ° C), relatively cool summers (with an average monthly temperature close to + 14 ... + 16 ° C) and the predominance of the amount of atmospheric precipitation over evaporation. In the coldest regions of the taiga belt (east of the Yenisei in Eurasia, in northern Canada and Alaska in North America) there is permafrost, but the soil thaws in summer to a depth of 50 to 250 cm, so the permafrost does not interfere with the growth of trees with a shallow root system. These climatic conditions determine the leaching type of water regime in areas not bound by permafrost. In areas with permafrost, the leaching regime is violated.

The predominant type of vegetation in the zone is coniferous forests, sometimes with an admixture of deciduous trees. In the very south of the taiga zone, pure deciduous forests are distributed in places. About 20% of the entire area of ​​the taiga zone is occupied by marsh vegetation, the areas under meadows are small. The biomass of coniferous forests is significant (1000–3000 c/ha), but the litter is only a few percent of the biomass (30–70 c/ha).

A significant part of the forests of Europe and North America has been destroyed, so the soils formed under the influence of forest vegetation have been in the conditions of treeless, human-modified landscapes for a long time.

The taiga zone is heterogeneous: the forest landscapes of different regions differ significantly in the conditions of soil formation.

In the absence of permafrost, various types of podzolic soils are formed on well-permeable sandy and sandy loam soils. The structure of the profile of these soils:

A 0 - forest litter, consisting of needle litter, remains of trees, shrubs and mosses that are at different stages of decomposition. At the bottom, this horizon gradually turns into a loose mass of coarse humus, at the very bottom, partially mixed with detrital minerals. The thickness of this horizon is from 2–4 to 6–8 cm. The reaction of the forest litter is strongly acidic (рН = 3.5–4.0). Further down the profile, the reaction becomes less acidic (pH increases to 5.5–6.0).

A 2 is the eluvial horizon (washout horizon), from which all more or less mobile compounds are removed to the lower horizons. In these soils, this horizon is called podzolic . Sandy, easily crumbling, due to washing out of a pale gray, almost white color. Despite its low thickness (from 2–4 cm in the north and center to 10–15 cm in the south of the taiga zone), this horizon stands out sharply in the soil profile due to its color.

B - bright brown, coffee or rusty-brown illuvial horizon, in which washout predominates, i.e. sedimentation of compounds of those chemical elements and small particles that were washed out of the upper part of the soil stratum (mainly from the podzolic horizon). With depth in this horizon, the rusty-brown hue decreases and gradually passes into the parent rock. Thickness 30–50 cm.

C - soil-forming rock, represented by gray sand, crushed stone and boulders.

The profile thickness of these soils gradually increases from north to south. The soils of the southern taiga have the same structure as the soils of the northern and middle taiga, but the thickness of all horizons is greater.

In Eurasia, podzolic soils are distributed only in a part of the taiga zone to the west of the Yenisei. In North America, podzolic soils are common in the southern part of the taiga zone. The territory east of the Yenisei in Eurasia (Central and Eastern Siberia) and the northern part of the taiga zone in North America (northern Canada and Alaska) are characterized by continuous permafrost, as well as vegetation cover features. Acid brown taiga soils (podburs) are formed here, sometimes called permafrost-taiga ferruginous soils.

These soils are characterized by a profile with an upper horizon composed of coarse humus and the absence of a clarified leaching horizon characteristic of podzolic soils. The profile is thin (60–100 cm) and poorly differentiated. Like podzolic, brown taiga soils are formed under conditions of a slow biological cycle and a small mass of annual plant litter, which almost completely comes to the surface. As a result of the slow transformation of plant residues and the leaching regime, a peaty dark brown litter is formed on the surface, from the organic matter of which readily soluble humus compounds are washed out. These substances are deposited throughout the soil profile in the form of humus-iron oxide compounds, as a result of which the soil acquires a brown, sometimes ocher-brown color. The humus content gradually decreases down the profile (under the litter, humus contains 8–10%; at a depth of 50 cm, about 5%; at a depth of 1 m, 2–3%).

The agricultural use of soils in the taiga zone is associated with great difficulties. In the Eastern European and Western Siberian taiga, arable lands occupy 0.1–2% of the total area. The development of agriculture is hampered by unfavorable climatic conditions, severe soil bouldering, widespread waterlogging of the territory, and permafrost to the east of the Yenisei. Agriculture is developing more actively in the southern regions of the East European taiga and in the meadow-steppe regions of Yakutia.

For effective use taiga soils require large doses of mineral and organic fertilizers, neutralization of high soil acidity, in some places - removal of boulders.

In medical and geographical terms, the zone of taiga forests is not very favorable, since as a result of intensive washing out of the soil, many chemical elements are lost, including those necessary for the normal development of humans and animals, therefore, in this zone, conditions are created for a partial deficiency of a number of chemical elements (iodine, copper, calcium, etc.)

Zone of mixed forests.

To the south of the taiga forest zone there are mixed coniferous-deciduous forests. In North America, these forests are common in the east of the mainland in the Great Lakes region. in Eurasia - on the territory of the East European Plain, where they form a wide zone. Beyond the Urals they continue far to the east, up to the Amur region, although they do not form a continuous zone.

The climate of mixed forests is characterized by warmer and longer summers (average July temperature from 16 to 24°C) and warmer winters (average January temperature from 0 to –16°C) compared to the taiga forest zone. The annual amount of precipitation is from 500 to 1000 mm. The amount of precipitation everywhere exceeds evaporation, which leads to a well-defined flushing water mode. Vegetation - mixed forests of coniferous (spruce, fir, pine), small-leaved (birch, aspen, alder, etc.) and broad-leaved (oak, maple, etc.) species. A characteristic feature of mixed forests is a more or less developed grass cover. The biomass of mixed forests is higher than in the taiga and amounts to 2000–3000 q/ha. The mass of litter also exceeds the biomass of taiga forests, but due to more intensive microbiological activity, the processes of destruction of dead organic matter proceed more vigorously, therefore, in mixed forests, the litter is less thick than in the taiga and is more decomposed.

The zone of mixed forests has a rather variegated soil cover. Soddy-podzolic soils are the most characteristic type of automorphic soils of mixed forests of the East European Plain. – southern variety of podzolic soils. Soils are formed only on loamy soil-forming rocks. Soddy-podzolic soils have the same structure of the soil profile as podzolic ones. They differ from the podzolic ones in the thinner forest litter (2–5 cm), in the greater thickness of all horizons, and in the more pronounced A1 humus horizon lying under the forest litter. The appearance of the humus horizon in soddy-podzolic soils also differs from the horizon in podzolic soils; in the upper part it contains numerous grass roots, which often form a well-defined sod. Color - gray of various shades, the addition is loose. The thickness of the humus horizon is from 5 to 20 cm, the humus content is 2–4%.

In the upper part of the profile, these soils are characterized by an acid reaction (pH = 4), with depth the reaction gradually becomes less acidic.

The use of soils of mixed forests in agriculture is higher than that of soils of taiga forests. In the southern regions of the European part of Russia, 30–45% of the area has been plowed up; to the north, the share of plowed land is much less. Farming is difficult due to the acidic reaction of these soils, their strong leaching, and in some places swampiness and boulders. To neutralize excess acidity of the soil, lime is applied. To obtain high yields, large doses of organic and mineral fertilizers are needed.

Deciduous forest zone.

In the temperate zone, in warmer conditions (compared to taiga and subtaiga mixed forests), broad-leaved forests with a rich grass cover are common. In North America, the broad-leaved forest zone extends south of the mixed forest zone in the east of the continent. In Eurasia, these forests do not form a continuous zone, but stretch in discontinuous stripes from Western Europe to the Primorsky Territory of Russia.

Landscapes of deciduous forests that are favorable for humans are exposed to human influence for a long time, so they are greatly changed: forest vegetation is either completely destroyed (in most of Western Europe and the USA) or replaced by secondary vegetation.

There are two types of soils formed in these landscapes:

1. Gray forest soils formed in inland regions (central regions of Eurasia and North America). In Eurasia, these soils stretch in islands from the western borders of Belarus to Transbaikalia. Gray forest soils form in continental climates. In Eurasia, the severity of the climate increases from west to east, average January temperatures vary from -6°C in the west of the zone to -28°C in the east, and the frost-free period lasts from 250 to 180 days. Summer conditions are relatively the same - the average July temperature ranges from 19 to 20 ° C. Annual precipitation varies from 500-600 mm in the west to 300 mm in the east. The soils are wetted by precipitation to a great depth, but since the groundwater in this zone lies deep, the leaching water regime is not typical here, only in the most humid areas there is a continuous wetting of the soil stratum to groundwater.

The vegetation under which gray forest soils have formed is represented mainly by broad-leaved forests with a rich grass cover. To the west of the Dnieper, these are hornbeam-oak forests; between the Dnieper and the Urals, linden-oak forests;

The mass of litter of these forests significantly exceeds the mass of litter of taiga forests and amounts to 70–90 q/ha. The litter is rich in ash elements, especially calcium.

The soil-forming rocks are mainly cover loess-like loams.

Favorable climatic conditions determine the development of soil fauna and microbial population. As a result of their activity, a more vigorous transformation of plant residues occurs than in soddy-podzolic soils. This causes a more powerful humus horizon. However, part of the litter is still not destroyed, but accumulates in the forest litter, the thickness of which is less than the thickness of the litter in soddy-podzolic soils.

Profile structure of gray forest soil ( cm. SOIL MORPHOLOGY):

A 0 - forest litter from the litter of trees and grasses, usually of small thickness (1–2 cm);

A 1 is a humus horizon of gray or dark gray color, fine or medium cloddy structure, containing a large amount of grass roots. In the lower part of the horizon there is often a coating of silica powder. The thickness of this horizon is 20–30 cm.

A 2 is a washout horizon, gray in color, with an indistinctly expressed sheet-lamellar structure and a thickness of about 20 cm. Small ferromanganese nodules are found in it.

B – intrusion horizon, brown-brown in color, with a clearly expressed nutty structure. Structural units and pore surfaces are covered with dark brown films, small ferromanganese concretions are found. The thickness of this horizon is 80–100 cm.

C - parent rock (covering loess-like yellowish-brown loam with a well-defined prismatic structure, often contains carbonate neoformations).

The type of gray forest soils is divided into three subtypes - light gray, gray and dark gray, the names of which are associated with the color intensity of the humus horizon. With the darkening of the humus horizon, the thickness of the humus horizon somewhat increases and the degree of leaching of these soils decreases. The eluvial horizon A 2 is present only in light gray and gray forest soils; dark gray soils do not have it, although the lower part of the humus horizon A 1 has a whitish tint. The formation of subtypes of gray forest soils is determined by bioclimatic conditions; therefore, light gray forest soils gravitate towards the northern regions of the gray soil belt, gray ones towards the middle ones, and dark gray ones towards the southern ones.

Gray forest soils are much more fertile than soddy-podzolic soils; they are favorable for growing grain, fodder, horticultural and some industrial crops. The main disadvantage is the greatly reduced fertility as a result of their centuries-old use and significant destruction as a result of erosion.

2. Brown forest soils were formed in areas with a mild and humid oceanic climate, in Eurasia - these are Western Europe, the Carpathians, the Mountainous Crimea, warm and humid regions of the Caucasus and the Primorsky Territory of Russia, In North America - the Atlantic part of the continent.

The annual amount of precipitation is significant (600–650 mm), but most of it falls in the summer, so the leaching regime operates for short periods of time. At the same time, mild climatic conditions and significant atmospheric moisture intensify the processes of transformation of organic matter. A significant amount of litter is processed and mixed by numerous invertebrates, contributing to the formation of a humus horizon. With the destruction of humic substances, the slow movement of clay particles into the intrusion horizon begins.

The profile of brown forest soils is characterized by a weakly differentiated and thin, not very dark humus horizon.

Profile structure:

A 1 is a gray-brown humus horizon, the humus shade gradually decreases at the bottom, the structure is lumpy. Power - 20-25 cm.

B is the washout horizon. At the top, bright brownish-brown, clayey, downwards the brown tint will decrease, and the color approaches the color of the parent rock. The thickness of the horizon is 50–60 cm.

C - soil-forming rock (loess-like loam of pale color, sometimes with carbonate neoplasms).

With a large amount of fertilizers applied and rational agricultural technology, these soils give very high yields of various agricultural crops, in particular, the highest yields of grain crops are obtained precisely on these soils. In the southern regions of Germany and France, brown soils are used mainly for vineyards.

Zone of meadow steppes, forest-steppes and meadow-forb steppes.

In Eurasia, to the south of the zone of deciduous forests, a zone of forest-steppes stretches, which is replaced even further south by a zone of steppes. Automorphic soils of landscapes of meadow steppes of the forest-steppe zone and meadow-forb steppes of the steppe zone are called chernozems .

In Eurasia, chernozems extend as a continuous strip through the East European Plain, the Southern Urals and Western Siberia to Altai, and to the east of Altai they form separate massifs. The most eastern massif is located in Transbaikalia.

In North America, there are also zones of forest-steppes and steppes, to the west of zones of mixed and broad-leaved forests. Submeridional strike - from the north they border on the taiga zone (about 53 ° N), and in the south they reach the coast of the Gulf of Mexico (24 ° N), however, the strip of chernozem soils is located only in the inland region and does not go to the sea coast.

In Eurasia, the climatic conditions of the zone of distribution of chernozems are characterized by an increase in continentality from west to east. In the Western regions, the winter is warm and mild (the average January temperature is -2 ... -4 ° C), and in the eastern regions it is severe and with little snow (the average January temperature is -25 ... -28 ° C). From west to east, the number of frost-free days decreases (from 300 in the west to 110 in the east) and the annual amount of precipitation (from 500–600 in the west to 250–350 in the east). During the warm period, differences in climate are smoothed out. In the west of the zone, the average July temperature is +19…+24°С, in the east – +17…+20°С.

In North America, the severity of the climate in the zone of distribution of chernozem soils increases from north to south: the average temperature in January varies from 0 ° C in the south to -16 ° C in the north, summer temperatures are the same: the average temperature in July is +16 - + 24 ° C. Annual precipitation also does not change - from 250 to 500 mm per year.

For the entire area of ​​distribution of chernozem soils, evaporation is equal to the annual amount of precipitation or less. Most of the precipitation falls in the summer, often in the form of showers - this contributes to the fact that a significant part of the precipitation is not absorbed into the soil, but is removed in the form of surface runoff, therefore, non-leaching water regime is characteristic of chernozems. The exception is the forest-steppe regions, where the soils are periodically washed out.

Soil-forming rocks of the territory of chernozems are represented mainly by loess-like deposits (loess is a fine-grained sedimentary rock of light yellow or pale yellow color).

The chernozems were formed under grassy vegetation, which is dominated by perennial grasses, but now most of the chernozem steppes have been plowed up and the natural vegetation has been destroyed.

The biomass in natural steppe communities reaches 100–300 c/ha, of which half dies off annually; as a result, much more organic matter enters the soil in the chernozem zone than in the forest zone of the temperate zone, although the forest biomass is more than 10 times higher than the biomass of the steppes. There are significantly more microorganisms in steppe soils than in forest soils (3–4 billion per 1 g, and even more in some areas). The intensive activity of microorganisms aimed at processing plant litter stops only during periods of winter freezing and summer drying of the soil. A significant amount of annually arriving plant residues ensures the accumulation of large amounts of humus in chernozem soils. The content of humus in chernozems varies from 3–4 to 14–16%, and sometimes even more. hallmark chernozems is the content of humus in the entire soil profile, and down the profile it decreases very gradually. The reaction of the soil solution in the upper part of the profile in these soils is neutral; in the lower part of the profile, starting from the illuvial horizon (B), the reaction becomes slightly alkaline.

The most characteristic feature of these soils, which determined their name, is a powerful, well-developed humus horizon of intensely black color.

Profile structure of typical chernozems:

And 0 - steppe felt. This horizon, 1–3 cm thick, consists of the remains of herbaceous vegetation and is found only on virgin lands.

A 1 - humus horizon. Its color when wet is intensely black, its thickness is 40–60 cm. The horizon is saturated with plant roots.

B - transitional horizon of blackish-brown uneven color, gradually turning into the color of the soil-forming rock. Humus streaks enter here from the humus horizon. The lower part of the horizon contains a significant amount of calcium carbonate. The thickness of this horizon is 40–60 cm.

C - soil-forming rock (loess-like deposits).

In Eurasia, south of typical chernozems, ordinary , and further south - southern black soil. To the south, the annual amount of precipitation, the total biomass and, accordingly, the mass of the annual plant litter decreases. This causes a decrease in the thickness of the humus horizon (in ordinary chernozems, its thickness is about 40 cm, in the southern - 25 cm). The properties of chernozem soils also change as the continentality of the climate increases, i.e. from west to east (in Eurasia).

Chernozems are famous for their fertility, the areas of their distribution are the main base for the production of many grains, primarily wheat, as well as a number of valuable industrial crops (sugar beet, sunflower, corn). The yield on chernozems depends mainly on the water content in a form available to the plant. In our country, the black earth regions were characterized by crop failures caused by droughts.

The second equally important problem of chernozems is the destruction of soils caused by erosion. Chernozem soils used for agriculture require special anti-erosion measures.

The medical and geographical characteristics of chernozems are favorable. Chernozems are the standard for the optimal ratio of chemical elements necessary for humans. Endemic diseases associated with a deficiency of chemical elements are not characteristic of the areas where these soils are distributed.

Zone of dry steppes and semi-deserts of the temperate zone.

To the south of the steppe zone stretches the zone of semi-deserts. The southern steppes (they are called dry steppes), bordering on semi-deserts, differ significantly in vegetation cover and soils from the northern steppes. In terms of their vegetation cover and soils, the southern steppes are closer to semi-deserts than to steppes.

In arid and extracontinental conditions of dry steppes and semi-deserts, chestnut and brown desert-steppe soils are formed, respectively.

In Eurasia, chestnut soils occupy a small area in Romania and are more widely represented in the arid central regions of Spain. They stretch in a narrow strip along the coast of the Black and Azov Seas. To the east (in the Lower Volga region, Western Caspian) the area of ​​these soils increases. Chestnut soils are very widespread in the territory of Kazakhstan, from where a continuous strip of these soils goes to Mongolia, and then to East China, occupying most of the territory of Mongolia and the central provinces of China. In Central and Eastern Siberia, chestnut soils are found only in islands. The easternmost region of chestnut soils is the steppes of South-Eastern Transbaikalia.

The distribution of brown desert-steppe soils is more limited - these are mainly semi-desert regions of Kazakhstan.

In North America, chestnut and brown soils are located in the central part of the continent, bordering the black earth zone from the east, and the Rocky Mountains from the west. In the south, the area of ​​distribution of these soils is limited by the Mexican plateau.

The climate of the dry and desert steppes is sharply continental, continentality intensifies as you move from west to east (in Eurasia). The average annual temperature varies from 5–9°C in the west to 3–4°C in the east. Annual precipitation decreases from north to south (in Eurasia) from 300–350 to 200 mm. Precipitation is evenly distributed throughout the year. Evaporation (a conditional value that characterizes the maximum possible evaporation in a given area with an unlimited supply of water) significantly exceeds the amount of precipitation, therefore, a non-leaching water regime prevails here (soils are soaked to a depth of 10 to 180 cm). Strong winds further dry out the soil and promote erosion.

The vegetation of this area is dominated by steppe grasses and wormwood, the content of which increases from north to south. The biomass of the vegetation of dry steppes is about 100 c/ha, and its main part (80% or more) falls on the underground organs of plants. The annual litter is 40 c/ha.

Soil-forming rocks are loess-like loams occurring on rocks of different composition, age and origin.

Profile structure of chestnut and brown soils:

A - humus horizon. In chestnut soils, it is grayish-chestnut in color, saturated with plant roots, has a cloddy structure, and has a thickness of 15–25 cm. In brown soils, it is brown in color, has a cloddy, fragile structure, and is about 10–15 cm thick. The humus content in this horizon is from 2 to 5% in chestnut soils and about 2% in brown soils.

B - brown-brown transitional horizon, compacted, carbonate neoformations are found below. Thickness 20–30 cm.

C is a soil-forming rock, represented by loess-like loam of yellowish-brown color in chestnut soils and brownish-pale in brown ones. In the upper part there are carbonate neoformations. Below 50 cm in brown soils and 1 m in chestnut soils, new formations of gypsum are found.

The change in the amount of humus down the profile occurs gradually, as in chernozems. The reaction of the soil solution in the upper part of the profile is slightly alkaline (pH = 7.5), below the reaction becomes more alkaline.

Among the chestnut soils, three subtypes are distinguished, replacing each other from north to south:

Dark chestnut , having a humus horizon thickness of about 25 cm or more, chestnut with a humus horizon thickness of about 20 cm and light chestnut, with a humus horizon thickness of about 15 cm.

Feature The soil cover of dry steppes is extremely diverse, this is due to the redistribution of heat and especially moisture, and with it water-soluble compounds, according to the forms of meso- and microrelief. The lack of moisture is the cause of a very sensitive reaction of vegetation and soil formation even to a slight change in moisture. Zonal automorphic soils (i.e. chestnut and brown desert-steppe) occupy only 70% of the territory, the rest falls on saline hydromorphic soils (salt licks, solonchaks, etc.).

The difficulty of using the soils of dry steppes for agriculture is explained both by the low content of humus and by the unfavorable physical properties of the soils themselves. In agriculture, mainly dark chestnut soils are used in the most humid areas and which have a fairly high degree of fertility. With proper agricultural practices and the necessary reclamation, these soils can produce sustainable crops. Since the main cause of crop failures is the lack of water, the problem of irrigation becomes especially acute.

In medical and geographical terms, chestnut and especially brown soils are sometimes overloaded with easily soluble compounds and have an increased content of some trace chemical elements, primarily fluorine, which can have negative consequences for humans.

Desert zone.

In Eurasia, south of the semi-desert zone, the desert zone stretches. It is located in the inland part of the continent - on the vast plains of Kazakhstan, Central and Central Asia. The zonal automorphic soils of deserts are gray-brown desert soils.

The climate of the deserts of Eurasia is characterized by hot summers (the average July temperature is 26–30°C) and cold winters (the average January temperature varies from 0–16°C in the north of the zone to 0 +16°C in the south of the zone). The average annual temperature varies from +16°C in the northern part to +20°C in the southern part of the zone. The amount of precipitation is usually not more than 100–200 mm per year. The distribution of precipitation by months is uneven: the maximum falls on the winter-spring time. Water regime non-leaching - soils are soaked to a depth of about 50 cm.

The vegetation cover of deserts is mainly saltwort-shrub with ephemeral plants (annual herbaceous plants, the entire development of which takes place in a very short time, usually in early spring). There are many algae in desert soils, especially on takyrs (a type of hydromorphic desert soil). Desert vegetation vegetates vigorously in spring with lush development of ephemera. In the dry season, life in the desert freezes. The biomass of semi-shrub deserts is very low - about 43 q/ha. A small mass of annual litter (10–20 c/ha) and energetic activity of microorganisms contribute to the rapid destruction of organic residues (there is no undecomposed litter on the surface) and a low content of humus in gray-brown soils (up to 1%).

Among the soil-forming rocks, loess-like and ancient alluvial deposits, processed by the wind, predominate.

Gray-brown soils are formed on elevated flat areas of the relief. A characteristic feature of these soils is the accumulation of carbonates in the upper part of the soil profile, which has the form of a surface porous crust.

Profile structure of gray-brown soils:

And k - carbonate horizon, this is a surface crust with characteristic rounded pores, cracked into polygonal elements. Power - 3-6 cm.

A - a weakly expressed gray-brown humus horizon, weakly fastened by roots in the upper part, loose from top to bottom, easily blown by the wind. Thickness 10–15 cm.

B - transitional compacted horizon of brown color, prismatic-blocky structure, containing rare and poorly expressed carbonate formations. Thickness from 10 to 15 cm.

C - parent rock - loose loess-like loam, overflowing with small gypsum crystals. At a depth of 1.5 m and below, a peculiar gypsum horizon often occurs, represented by accumulations of vertically arranged acicular gypsum crystals. The thickness of the gypsum horizon is from 10 cm to 2 m.

Salt marshes are characteristic hydromorphic soils of deserts. , those. soils containing 1% or more water-soluble salts in the upper horizon. The bulk of solonchaks is distributed in the desert zone, where they occupy about 10% of the area. In addition to the desert zone, solonchaks are quite widespread in the zone of semi-deserts and steppes; they are formed with close occurrence of groundwater and effluent water regime. Salt-containing groundwater reaches the soil surface and evaporates, as a result, salts are deposited in the upper soil horizon, and its salinization occurs.

Soil salinization can occur in any zone under fairly dry conditions and close proximity to groundwater; this is confirmed by solonchaks in arid regions of the taiga, tundra and arctic zones.

The vegetation of solonchaks is peculiar, highly specialized in relation to the conditions of a significant content of salts in the soil.

The use of desert soils in the national economy is associated with difficulties. Due to the lack of water, agriculture in desert landscapes is selective; most of the deserts are used for transhumance. Cotton and rice are cultivated on irrigated areas of gray soils. The oases of Central Asia have been famous for their fruit and vegetable crops for many centuries.

The increased content of some trace chemical elements (fluorine, strontium, boron) in the soils of certain areas can cause endemic diseases, for example, tooth decay as a result of exposure to high concentrations of fluorine.

Subtropical zone.

In this climatic zone, the following main groups of soils are distinguished: soils of moist forests, dry forests and shrubs, dry subtropical steppes and low-grass semi-savannahs, as well as subtropical deserts.

1. Krasnozems and zheltozems of landscapes of humid subtropical forests

These soils are widespread in subtropical East Asia (China and Japan) and the southeastern United States (Florida and neighboring southern states). They are also in the Caucasus - on the coast of the Black (Adzharia) and Caspian (Lenkoran) seas.

The climatic conditions of the humid subtropics are characterized by a large amount of precipitation (1-3 thousand mm per year), mild winters and moderately hot summers. Precipitation is unevenly distributed throughout the year: in some areas, most of the precipitation falls in the summer, in others - in the autumn-winter period. The leaching water regime prevails.

The composition of the forests of the humid subtropics varies depending on the floristic region to which this or that region belongs. The biomass of subtropical forests exceeds 4000 c/ha, the weight of litter is about 210 c/ha.

A characteristic type of soil in the humid subtropics is krasnozem, which got its name due to its color, due to the composition of parent rocks. The main soil-forming rock on which krasnozems develop is a thickness of redeposited weathering products of a specific brick-red or orange color. This color is due to the presence of strongly bound Fe (III) hydroxides on the surface of clay particles. Krasnozems have inherited from the parent rocks not only color, but also many other properties.

Soil profile structure:

A 0 - slightly decomposed forest litter, consisting of leaf litter and thin branches. Power - 1-2 cm.

A 1 is a gray-brown humus horizon with a reddish tint, with a large number of roots, a lumpy structure and a thickness of 10–15 cm. The humus content in this horizon is up to 8%. Down the profile, the humus content decreases rapidly.

B - brownish-red transitional horizon, the red hue intensifies downwards. Dense, lumpy structure, clay streaks are visible along the paths of dead roots. Power - 50-60 cm.

C - parent rock of red color with whitish spots, clay pellets are found, there are small ferromanganese nodules. In the upper part, films and streaks of clay are noticeable.

Krasnozems are characterized by an acid reaction of the entire soil profile (рН = 4.7–4.9).

Zheltozems are formed on clay shales and clays with poor water permeability, as a result of which gleying processes develop in the surface part of the profile of these soils, which cause the formation of iron oxide nodules in the soils.

The soils of moist subtropical forests are poor in nitrogen and some ash elements. To increase fertility, organic and mineral fertilizers are needed, primarily phosphates. The development of soils in the humid subtropics is complicated by severe erosion that develops after deforestation, so the agricultural use of these soils requires anti-erosion measures.

2. Brown soils of landscapes of dry subtropical forests and shrubs

Soils called brown, formed under dry forests and shrubs, are widespread in southern Europe and northwest Africa (Mediterranean region), in southern Africa, the Middle East, and in a number of regions of Central Asia. Such soils are found in warm and relatively dry regions of the Caucasus, on the southern coast of Crimea, in the Tien Shan mountains. In North America, soils of this type are common in Mexico; they are known under dry eucalyptus forests in Australia.

The climate of these landscapes is characterized by positive average annual temperatures. Winters are warm (temperatures above 0°C) and humid, summers are hot and dry. The annual amount of precipitation is significant - about 600-700 mm, but their distribution throughout the year is uneven - most of the precipitation falls from November to March, and there is little precipitation in the hot summer months. As a result, soil formation occurs under conditions of two successive periods: wet and warm, dry and hot.

Brown soils formed under dry forests of various species composition. In the Mediterranean, for example, these are forests of evergreen oak, laurel, maritime pine, tree-like juniper, as well as dry shrubs such as shilyak and maquis, hawthorn, hold-tree, fluffy oak, etc.

Profile structure of brown soils:

A 1 is a humus horizon of brown or dark brown color, lumpy structure, si 20–30 cm thick. The humus content in this horizon is 2.0–2.4%. Down the profile, its content gradually decreases.

B - compacted transitional horizon of bright brown color, sometimes with a reddish tint. This horizon often contains new carbonate formations, in relatively humid areas they are located at a depth of 1–1.5 m, in arid areas they can already be in the humus horizon.

C - soil-forming rock.

D - with a small thickness of the parent rock, below the transitional horizon, the underlying rock (limestone, shale, etc.) is located.

The soil reaction in the upper part of the profile is close to neutral (pH = 6.3), in the lower part it becomes slightly alkaline.

The soils of subtropical dry forests and shrubs are highly fertile and have been used for agriculture for a long time, including viticulture, cultivation of olive and fruit trees. Deforestation to expand cultivated land, combined with mountainous terrain, has contributed to soil erosion. Thus, in many countries of the Mediterranean, the soil cover was destroyed and many areas that once served as the granaries of the Roman Empire are now covered with desert steppes (Syria, Algeria, etc.).

3. Serozems of dry subtropics

Serozems are formed in arid landscapes of semi-deserts of the subtropical belt. , they are widely represented in the foothills of the ridges of Central Asia. They are distributed in northern Africa, in the continental part of the south of North and South America.

The climatic conditions of the serozem zone are characterized by warm winters (the average monthly temperature in January is about –2°C) and hot summers (the average monthly temperature in July is 27–28°C). Annual rainfall ranges from 300 mm in the low foothills to 600 mm in the foothills above 500 m above sea level. During the year, precipitation is distributed very unevenly throughout the year - most of it falls in winter and spring, and very little falls in summer.

The vegetation of gray soils is defined as subtropical steppes or low-grass semi-savannahs. Grasses predominate in the vegetation cover, giant umbrella plants are typical. During the period of spring moistening, ephemera and ephemeroids grow rapidly - bluegrass, tulips, poppies, etc.

Soil-forming rocks are predominantly loess.

Serozem profile structure:

A - light gray humus horizon, noticeably soddy, of an unclear lumpy structure, 15–20 cm thick. The amount of humus in this horizon is about 1.5–3%; down the profile, the humus content gradually decreases.

А/В is an intermediate horizon between the humus and transitional horizons. More loose than humus, thickness - 10–15 cm.

B - transitional horizon of brownish-yellow color, slightly compacted, contains carbonate neoformations. Gypsum new formations begin at a depth of 60–90 cm. Gradually passes to the soil-forming rock. Thickness is about 80 cm.

C - parent rock

The entire profile of serozems bears traces of intense activity of earth-moving worms, insects, and lizards.

The gray soils of the semi-deserts of the subtropical zone border on the gray-brown soils of the deserts of the temperate zone and are connected with them by gradual transitions. However, typical serozems differ from gray-brown soils in the absence of a surface porous crust, a lower content of carbonates in the upper part of the profile, a significantly higher content of humus, and a lower location of gypsum neoformations.

Serozems have a sufficient amount of chemical elements necessary for plant nutrition, with the exception of nitrogen. The main difficulty in their agricultural use is associated with a lack of water, so irrigation is important for the development of these soils. So, on irrigated gray soils in Central Asia, rice and cotton are cultivated. Agriculture without special irrigation is possible mainly in the elevated areas of the foothills.

Tropical zone.

The tropics here mean the territory between the northern and southern tropics, i.e. parallels with latitudes 23° 07º north and south latitude. This territory includes tropical, subequatorial and equatorial climatic zones.

Tropical soils occupy more than 1/4 of the world's land surface. The conditions of soil formation in the tropics and countries of high latitudes are sharply different. The most noticeable distinguishing features of tropical landscapes are the climate, flora and fauna, but the differences are not limited to these. Most of the tropical territory (South America, Africa, the Indian subcontinent, Australia) is the remains of the most ancient land (Gondwana), on which weathering processes have been going on for a long time - starting from the Lower Paleozoic, and in some places even from the Precambrian. Therefore, some important properties of modern tropical soils are inherited from ancient weathering products, and individual processes of modern soil formation are complexly related to the processes of ancient stages of hypergenesis (weathering).

Traces of the most ancient stage of hypergenesis, the formations of which are widespread in many areas of the ancient land, are represented by a thick weathering crust with a differentiated profile. These ancient crusts of the tropical area do not generally serve as soil-forming rocks, they are usually buried under more recent formations. In areas of deep faults, which cut through areas of ancient land in the Cenozoic and were accompanied by powerful volcanic eruptions, these crusts are overlain by powerful covers of lavas. However, over an immeasurably larger area, the surface of the ancient weathering crusts is covered with peculiar red cover deposits. These red-colored deposits, covering a huge area of ​​tropical land like a mantle, are a very special supergene formation that arose under different conditions and at a much later time than the ancient weathering crusts underlying them.

Red-colored deposits have a sandy-loamy composition, their thickness varies from a few decimeters to 10 m or more. These deposits were formed under sufficiently humid conditions favoring the high geochemical activity of iron. These deposits contain iron oxide, which gives the deposits their red color.

These red-colored deposits are the most typical soil-forming rocks of the tropics, so many tropical soils are red or close to it, as reflected in their names. These colors are inherited by soils, which can be formed under various modern bioclimatic conditions. Along with red-colored deposits, gray lacustrine loams, light yellow sandy loamy alluvial deposits, brown volcanic ash, etc. can act as soil-forming rocks; therefore, soils formed under the same bioclimatic conditions are not always the same color.

The most important feature of the tropical zone is a stable high air temperature, therefore, the nature of atmospheric humidification is of particular importance. Since evaporation in the tropics is high, the annual amount of precipitation does not give an idea of ​​the degree of atmospheric moisture. Even with a significant annual amount of precipitation in tropical soils, during the year there is a change between a dry period (with a total precipitation of less than 60 mm per month) and a wet period (with a total precipitation of more than 100 mm per month). In accordance with moisture in soils, there is a change of non-leaching and leaching regimes.

1. Soils of landscapes of rain (permanently wet) tropical forests

Permanent rainforests are distributed over a large area in South America, Africa, Madagascar, Southeast Asia, Indonesia, the Philippines, New Guinea and Australia. Soils are formed under these forests, for which different names were proposed at different times - red-yellow laterite, ferralite and etc.

The climate of these forests is hot and humid, with average monthly temperatures over 20°C. Annual precipitation is 1800–2000 mm, although in some places it reaches 5000–8000 mm. The duration of the dry period does not exceed 1–2 months. Significant moisture is not accompanied by oversaturation of the soil with water and there is no waterlogging.

The abundance of heat and moisture determines the largest biomass among the biocenoses of the world - about 5000 centners per hectare and the mass of annual litter - 250 centners per hectare. There is almost no forest litter, since almost all the litter is destroyed throughout the year due to the intensive activity of soil animals and microorganisms. Most of the elements released as a result of the decomposition of the litter are immediately captured by the complex root system of the rainforest and are again involved in the biological cycle.

As a result of these processes, there is almost no humus accumulation in these soils. The humus horizon of the rainforest soil is gray, very thin (5–7 cm) and contains only a few percent of humus. It is replaced by a transitional A/B horizon (10–20 cm), during which the humus shade completely disappears.

The peculiarity of these biocenoses is that almost the entire mass of chemical elements necessary for plant nutrition is contained in the plants themselves and only because of this is not washed out by heavy precipitation. When rainforest is cut down, precipitation very quickly erodes the upper thin fertile soil layer and barren lands remain under the reduced forest.

2. Soils of tropical landscapes with seasonal atmospheric moisture

Within the limits of tropical land, the largest area is occupied not by constantly moist forests, but by various landscapes, where atmospheric moisture is uneven throughout the year, and temperature conditions change slightly (average monthly temperatures are close to 20 ° C).

With the duration of the dry period from 3 to 6 months a year, with an annual amount of precipitation from 900 to 1500 mm, landscapes of seasonally moist light tropical forests and tall grass savannas develop.

Light tropical forests are characterized by a free arrangement of trees, an abundance of light and, as a result, a lush cover of cereal grasses. Tall grass savannas are various combinations of grassy vegetation with forest islands or individual tree specimens. The soils that form beneath these landscapes are referred to as red or ferrallitic soils of seasonal rainforests and tall grass savannahs.

The structure of the profile of these soils:

Above is a humus horizon (A), more or less soddy in the upper part, 10–15 cm thick, dark gray in color. Below is a transitional horizon (B), during which the gray tint gradually disappears and the red color of the parent rock intensifies. The thickness of this horizon is 30–50 cm. The total content of humus in the soil is from 1 to 4%, sometimes more. Soil reaction is slightly acidic, often almost neutral.

These soils are widely used in tropical agriculture. The main problem with their use is the easy destruction of soils under the influence of erosion.

With a dry period of 7 to 10 months a year and an annual rainfall of 400–600 mm, xerophytic biocenoses develop, which are a combination of dry tree and shrub thickets and low grasses. The soils that form under these landscapes are called the red-brown soils of the dry savannas.

The structure of these soils:

Under the humus horizon A, about 10 cm thick, of a slightly gray tint, there is a transitional horizon B, 25–35 cm thick. Carbonate nodules are sometimes found in the lower part of this horizon. Next comes the parent rock. The humus content in these soils is usually low. Soil reaction is slightly alkaline (рН = 7.0–7.5).

These soils are widespread in the central and western regions of Australia, in some areas of tropical Africa. For agriculture, they are of little use and are used mainly for pastures.

With an annual precipitation of less than 300 mm, soils of arid tropical (semi-desert and desert) landscapes are formed. , having common features with gray-brown soils and gray soils. They have a thin and carbonate weakly differentiated profile. Since the soil-forming rocks in many areas are red-colored products of [Neogene] weathering, these soils have a reddish color.

Tropical island zone.

A special group is formed by the soils of the oceanic islands of the tropical belt of the World Ocean, among them the most peculiar are the soils of coral islands - atolls.

The soil-forming rocks on such islands are snow-white coral sands and reef limestones. The vegetation is represented by thickets of shrubs and forests of coconut palms with a discontinuous cover of low grasses. Here, atoll humus-carbonate sandy soils with a thin humus horizon (5–10 cm) characterized by a humus content of 1–2% and a pH of about 7.5 are most common.

Avifauna is often an important factor in soil formation on islands. Bird colonies deposit huge amounts of droppings, which enrich the soil with organic matter and promote the development of special woody vegetation, thickets of tall grasses and ferns. A powerful peat-humus horizon with an acidic reaction is formed in the soil profile. Such soils are called atoll melano-humus-carbonate.

Humus-calcareous soils are important natural resource numerous island states of the Pacific and Indian Oceans, being the main plantation for the coconut palm.

Mountain area.

Mountain soils occupy more than 20% of the entire land surface. In mountainous countries, the same combination of soil-forming factors is basically repeated as in the plains; therefore, many soils such as automorphic soils of plain territories are common in the mountains: podzolic, chernozem, etc. However, the formation of soils in mountainous and lowland areas has certain differences, therefore, soils of the same type formed in plains and mountainous areas clearly differ. There are mountain podzolic, mountain chernozems, etc. In addition, conditions are formed in mountainous areas in which specific mountain soils are formed that have no analogues on the plains (for example, mountain meadow soils).

One of the distinguishing features of the structure of mountain soils is the thinness of the genetic horizons and the entire soil profile. The thickness of the mountain soil profile can be 10 or more times less than the thickness of the profile of a similar flat soil, while maintaining the structure of the profile of the flat soil and its features.

Mountain areas are characterized by vertical zonality (or explanation) soil cover, which is understood as the regular change of some soils by others as they rise from the foot to the tops of high mountains. This phenomenon is due to a regular change in hydrothermal conditions and vegetation composition with height. The lower belt of mountain soils belongs to the natural zone, on the area of ​​which there are mountains. For example, if a mountain system is located in a desert zone, then gray-brown desert soils will form on its lower belt, but as they rise up the slope, they will alternately be replaced by mountain-chestnut, mountain-chernozem, mountain-forest and mountain-meadow soils. However, under the influence of local bioclimatic features, some natural areas may fall out of the structure of the vertical zonality of the soil cover. An inversion of soil zones can also be observed, when one zone turns out to be higher than it should be by analogy with horizontal ones.

Natalia Novoselova

Literature:

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



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

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

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

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

For example, in the temperate latitudes of North America, natural zones are located in the meridional direction, which is associated with the influence of the Cordilleras, which prevent the passage of moist winds from the Pacific Ocean into the interior of the mainland. In Eurasia, there are almost all zones of the Northern Hemisphere, but their width is not the same. For example, the zone of mixed forests gradually narrows from west to east as the distance from the ocean increases and the continentality of the climate increases. In the mountains, natural zones change with height - high-altitudezonation . The altitudinal zonality is due to climate change with uplift. The set of altitudinal belts in the mountains depends on the geographical position of the mountains themselves, which determines the nature of the nature of the lower belt, and the height of the mountains, which determines the nature of the highest altitudinal 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 belts is also affected by the direction of the ridges relative to the sides of the horizon and the prevailing winds. Thus, the southern and northern slopes of the mountains may differ in the number of altitudinal zones. As a rule, there are more of them on the southern slopes than on the northern ones. On slopes exposed to moist winds, the nature of the vegetation will differ from that of the opposite slope.

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

Natural land areas

Evergreen tropical and equatorial forests

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

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

Savannahs and woodlands

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

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

Deserts and semi-deserts

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

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

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

Many animals are nocturnal.

Hard-leaved evergreen forests and shrubs

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

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

Steppes and forest-steppes

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

broad-leaved and mixed forests

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

Taiga

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

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

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

Tundra and forest tundra

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

polar deserts

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

Altitude zones

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

Table "Natural areas"

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

Due to its fertility, it gives life to plants. Most of the soil is organomineral compounds. Other constituents are liquid and gaseous elements. Macro- and microelements influence the growth and development of plants.

Continuous land use is negative. Since the 1980s, 10 million hectares of arable land have become unusable. Most of the soils of Russia were acidified, saline, waterlogged, and also subjected to chemical and radioactive contamination. Soil fertility is adversely affected by wind and water erosion.

Soil types and map of Russia

The vast extent, variety of climate, relief and water regime formed a motley soil cover. Each region has its own type of soil. The most important indicator fertility is the thickness of the humus horizon. Humus is the top fertile layer of the soil. It is formed due to the activity of microorganisms that process the remains of plant and animal origin.

The following types of soils are most common in Russia:

arctic soils

Arctic soils are found in the Arctic. They practically do not contain humus, soil-forming processes are at a low level due to. The Arctic regions are used as hunting grounds or for the conservation of populations of unique animal species.

tundra soils

Tundra soils are located in and along the coast of the seas of the Arctic Ocean. These areas are dominated by permafrost. Lichens and mosses formed during the summer period are not good source to form humus. Due to permafrost, the soil thaws only 40 cm deep in a short summer. The lands are often saline. The content of humus in the soil of the tundra zone is insignificant due to weak microbiological activity. The land is used by the locals as pasture for deer.

Podzolic soils

Podzolic soils are common in mixed forests. The territories occupy 75% of the total area of ​​Russia. The abundance of water and the cool climate create an acidic environment. Because of it, organic matter goes to the depths. The humus horizon does not exceed ten centimeters. The soil has few nutrients, but a lot of moisture. When properly processed, it is suitable for agriculture. On podzolic soils enriched with fertilizers, cereals, potatoes and cereals give a good harvest.

gray forest soils

Gray forest soils are located in Eastern Siberia, its forest-steppes and broad-leaved forests. The formation of the flora of the region is influenced by the temperate climate and relief. The lands are a combination of podzolic and chernozem soils. The abundance of plant residues, summer rains and their complete evaporation contribute to the accumulation of humus. Forests are rich in lands with calcium carbonate. Due to high fertility, 40% of gray forest soils are actively used for agriculture. A tenth part falls on pastures and hayfields. On the remaining lands, corn, beets, buckwheat and winter crops are grown.

Chernozem soils

Chernozem soils are located in the south of the country, near the borders with Ukraine and Kazakhstan. The thick humus layer was influenced by the flat topography, warm climate and low rainfall. This type of soil is considered the most fertile in the world. Russia owns about 50% of the world's chernozem reserves. A large amount of calcium prevents the leaching of nutrients. In the southern regions there is a lack of moisture. The lands have been cultivated for hundreds of years, but they still remain fertile. More than other crops, chernozems are sown with wheat. Sugar beet, corn and sunflower give a high yield.

chestnut soils

Chestnut soils prevail in the Astrakhan region, the Minusinsk and Amur steppes. There is a shortage of humus due to high temperatures and lack of moisture. The earth is dense, swells when wet. Salts are poorly washed out by water, the soil has a slightly acidic reaction. It is suitable for agriculture if regular irrigation is maintained. Alfalfa, cotton, wheat and sunflower are grown here.

Brown and gray-brown soils

Brown and gray-brown soils are found in the Caspian lowland. Their characteristic feature is a porous crust on the surface. It is formed due to high temperatures and low humidity. There is a small amount of humus here. Carbonates, salts and gypsum accumulate in the soil. Land fertility is low, most of the territories are used for pastures. Rice, cotton and melons are grown on irrigated plots.

Soils of natural zones of Russia

Map of natural areas of Russia

Natural complexes replace each other from north to south of the country, there are eight of them in total. Each natural zone of Russia is characterized by its unique soil cover.

Soils of the arctic desert

The soil cover is practically not expressed. Mosses and lichens grow in small areas. In warm weather, grass appears above the ground. All this looks like small oases. Plant residues cannot form humus. The thawed layer of the earth in summer does not exceed 40 cm. Waterlogging, as well as summer drying, leads to cracking of the earth's surface. There is a lot of iron in the soil, which is why it has a brown color. IN arctic wilderness there are practically no swamps, lakes; in dry weather, salt spots form on the surface.

Tundra soils

The soils are waterlogged. This is due to the close occurrence of permafrost and insufficient evaporation of moisture. The pace of humification is very slow. Plant residues cannot rot and remain on the surface in the form of peat. The amount of nutrients is minimal. The earth has a bluish or rusty color.

Soils of the forest-tundra

The forest-tundra is characterized by a transition from tundra to taiga soils. Woodlands already resemble a forest, they have a superficial root system. Permafrost begins at the level of 20 cm. The upper layer warms up well in summer, which contributes to the formation of lush vegetation. Moisture does not evaporate well due to low temperatures, so the surface is swampy. Forest-tundra areas are a combination of podzolic and peat-gley soils. There is little humus here, the lands are acidified.

Taiga soils

There is practically no permafrost zone, so the soils are podzolic. Iron is destroyed under the action of acids and washed out into the deep layers of the soil. Silica is formed in the upper layers. Undergrowth is poorly developed in the taiga. Fallen needles and moss take a long time to decompose. The humus content is minimal.

Soils of deciduous and mixed forests

Soddy-podzolic and brown soils predominate in broad-leaved and mixed forests. This natural area is home to oaks, larches, maples, birches and lindens. Tree litter forms a lot of humus. The sod layer reduces the power of the earth, so the soddy-podzolic soil is poor in phosphorus and nitrogen. Brown soils are rich in nutrients. Humus gives them a dark color.

Soils of the forest-steppe

Forest-steppes are characterized by high evaporation of moisture; in summer, drought and dry winds are observed. Chernozem and gray forest soils are formed in this natural zone. The humus layer is large, while mineralization is slow. Due to the special fertility of the forest-steppe land, it has been actively cultivated for many years in a row. Plowed areas are subject to weathering and drying.

steppe soils

Represented by dark chestnut, ordinary and low-humus chernozems. The soil has enough nutrients. There is less humus in chestnut soils, so they are lighter than the rest.

Soils of deserts and semi-deserts

Chestnut soils predominate. Due to insufficient moisture, salts accumulate. Vegetation does not form a continuous cover. Plants have deep roots that can extract moisture far from the surface. Salt marshes occur in places. There is little humus; gypsum can be found in the lower layers.

Which region of Russia has the most fertile soils?

Chernozem is the most fertile type of soil. It cannot be created artificially. Chernozem occupies only 10% of the total territory of the country, but its productivity is much higher than other soils. This type is rich in humus and calcium. The structure of the soil is heavy, loose, porous, so water and air easily penetrate to the roots of plants. Chernozem is found in the Central Black Earth economic region, which includes the Voronezh, Kursk, Belgorod, Lipetsk and Tambov regions. Podzolic soils with proper agricultural practices also give a high yield. They are common in the European part of Russia, the Far East and Eastern Siberia.