Types and properties of soils in different natural zones. Selection of optimal crops for planting, depending on the type and type of soil

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, therefore, 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 the soils formed under the most favorable conditions, only the plant-peaty horizon (А 0) is well expressed and the thin humus horizon (А 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 ° 33º N), however, in the north-east of the continent, tundra landscapes spread much further south, reaching the north-eastern part of the coast of Okhotsk sea ​​(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, her swamping. 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. Vegetables are grown around large industrial centers: potatoes, cabbage, onions, and many other crops in greenhouses.

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 ° С) and the predominance of the amount of 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 the effective use of taiga soils, large doses of mineral and organic fertilizers, neutralization of high soil acidity, and in some places the removal of boulders are required.

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 duration of the frost-free period is 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, east of the Urals within the West Siberian Lowland, birch and aspen forests predominate, and larch appears even further east.

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 is not close to the sea coast. comes out.

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 January temperature 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. The annual amount of 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.

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 forest biomass is more than 10 times higher than steppe biomass . 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. A distinctive feature of chernozems is the content of humus in the entire soil profile, and it decreases very gradually down the profile. 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 chestnut soils and about 2% in brown.

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.

A characteristic feature of the soil cover of dry steppes is its extreme diversity, 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-washing - 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 when groundwater is close to the ground and the water regime is effused. 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 rapidly decreases.

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. Thus, rice and cotton are cultivated on irrigated gray soils in Central Asia. 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 Hindustan Peninsula, 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, so 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, there is a change in the 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) throughout the year. 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 an important natural resource for numerous island nations in 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 formation factors is basically repeated as on 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, the same type the soils formed in the plains and mountainous areas are clearly different. 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 zones 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



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

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

Relationship between soil and natural areas

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

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

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

Soil types

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

Tundra

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

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

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

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

Podzolic

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

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

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

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

gray forest

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

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

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

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

Chernozem

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

By composition, chernozem is divided into subtypes:

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

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

Bolotnaya

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

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

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

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

Lugovaya

Meadow soils are formed in places where meadow vegetation grows.

This type of soil is divided into two subtypes:

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

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

comparison table

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

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

Economic importance

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

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

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

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

Features of soils and vegetation of different natural zones

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

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

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

Animals

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

Arctic

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

Tundra

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

forest zone

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

Steppe

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

Desert

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

Tropics

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

The richest belt in terms of vegetation

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

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

Video

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

The warmth of the sun, clean air and water are the main criteria for life on Earth. Numerous climatic zones led to the division of the territory of all continents and water space into certain natural zones. Some of them, even separated by vast distances, are very similar, others are unique.

Natural areas of the world: what is it?

This definition should be understood as very large natural complexes (in other words, parts of the geographic belt of the Earth), which have similar, uniform climatic conditions. The main characteristic of natural zones is the flora and fauna that inhabits this territory. They are formed as a result of uneven distribution of moisture and heat on the planet.

Table "Natural zones of the world"

natural area	climate zone	Average temperature (winter/summer)
Antarctic and Arctic deserts	Antarctic, arctic	24-70°С /0-32°С
Tundra and forest tundra	Subarctic and Subantarctic	8-40°С/+8+16°С
	Moderate	8-48°C /+8+24°C
mixed forests	Moderate	16-8°С /+16+24°С
broadleaf forests	Moderate	8+8°С /+16+24°С
Steppes and forest-steppes	subtropical and temperate	16+8 °С /+16+24°С
temperate deserts and semi-deserts	Moderate	8-24 °С /+20+24 °С
hardwood forests	Subtropical	8+16 °С/ +20+24 °С
Tropical deserts and semi-deserts	Tropical	8+16 °С/ +20+32 °С
Savannahs and woodlands		20+24°C and above
Variable rainforests	subequatorial, tropical	20+24°C and above
Permanently wet forests	Equatorial	above +24°C

This characteristic of the natural areas of the world is only introductory, because you can talk about each of them for a very long time, all the information will not fit in the framework of one table.

Natural zones of the temperate climate zone

1. Taiga. Surpasses all other natural zones of the world in terms of the area occupied on land (27% of the territory of all forests on the planet). It is characterized by very low winter temperatures. Deciduous trees do not withstand them, so the taiga is dense coniferous forests (mainly pine, spruce, fir, larch). Very large areas of the taiga in Canada and Russia are occupied by permafrost.

2. Mixed forests. Characteristic to a greater extent for the Northern Hemisphere of the Earth. It is a kind of border between the taiga and the broad-leaved forest. They are more resistant to cold and long winters. Tree species: oak, maple, poplar, linden, as well as mountain ash, alder, birch, pine, spruce. As the table "Natural areas of the world" shows, the soils in the zone of mixed forests are gray, not very fertile, but still suitable for growing plants.

3. Broad-leaved forests. They are not adapted to harsh winters and are deciduous. They occupy most of Western Europe, the south of the Far East, the north of China and Japan. Suitable for them is a maritime or temperate continental climate with hot summers and fairly warm winters. As the table "Natural zones of the world" shows, the temperature in them does not fall below -8 ° C even in the cold season. The soil is fertile, rich in humus. The following types of trees are characteristic: ash, chestnut, oak, hornbeam, beech, maple, elm. The forests are very rich in mammals (ungulates, rodents, predators), birds, including commercial ones.

4. Temperate deserts and semi-deserts. Their main distinguishing feature is the almost complete absence of vegetation and sparse wildlife. There are a lot of natural areas of this nature, they are located mainly in the tropics. There are temperate deserts in Eurasia, and they are characterized by sharp temperature changes during the seasons. Animals are represented mainly by reptiles.

Arctic deserts and semi-deserts

They are huge areas of land covered with snow and ice. The map of natural zones of the world clearly shows that they are located on the territory of North America, Antarctica, Greenland and the northern tip of the Eurasian continent. In fact, these are lifeless places, and polar bears, walruses and seals, arctic foxes and lemmings, penguins (in Antarctica) live only along the coast. Where the land is free of ice, lichens and mosses can be seen.

Moist equatorial forests

Their second name is rainforests. They are located mainly in South America, as well as in Africa, Australia and the Greater Sunda Islands. The main condition for their formation is a constant and very high humidity (more than 2000 mm of precipitation per year) and a hot climate (20 ° C and above). They are very rich in vegetation, the forest consists of several tiers and is an impenetrable, dense jungle that has become home to more than 2/3 of all types of creatures that now live on our planet. These rainforests are superior to all other natural areas of the world. Trees remain evergreen, changing foliage gradually and partially. Surprisingly, the soils of moist forests contain little humus.

Natural zones of the equatorial and subtropical climatic zone

1. Variably humid forests, they differ from rainforests in that precipitation falls there only during the rainy season, and during the period of drought that follows it, the trees are forced to shed their leaves. The animal and plant world is also very diverse and rich in species.

2. Savannas and woodlands. They appear where moisture, as a rule, is no longer enough for the growth of variable-humid forests. Their development occurs in the depths of the mainland, where tropical and equatorial air masses dominate, and the rainy season lasts less than six months. They occupy a significant part of the territory of subequatorial Africa, the interior of South America, partly Hindustan and Australia. More detailed information about the location is reflected in the map of natural areas of the world (photo).

hardwood forests

This climate zone is considered the most suitable for human habitation. Hardwood and evergreen forests are located along sea and ocean coasts. Precipitation is not so abundant, but the leaves retain moisture due to a dense leathery shell (oaks, eucalyptus), which prevents them from falling off. In some trees and plants, they are modernized into thorns.

Steppes and forest-steppes

They are characterized by the almost complete absence of woody vegetation, this is due to the meager level of precipitation. But the soils are the most fertile (chernozems), and therefore are actively used by man for agriculture. Steppes occupy large areas in North America and Eurasia. The predominant number of inhabitants are reptiles, rodents and birds. Plants have adapted to the lack of moisture and most often manage to complete their life cycle in a short spring period, when the steppe is covered with a thick carpet of greenery.

Tundra and forest tundra

In this zone, the breath of the Arctic and Antarctic begins to be felt, the climate becomes more severe, and even coniferous trees cannot withstand it. Moisture is in excess, but there is no heat, which leads to swamping of very large areas. There are no trees at all in the tundra, the flora is mainly represented by mosses and lichens. It is believed that this is the most unstable and fragile ecosystem. Due to the active development of gas and oil fields, it is on the verge of an ecological disaster.

All natural areas of the world are very interesting, whether it is a desert that seems completely lifeless at first glance, boundless Arctic ice or thousand-year-old rainforests with boiling life inside.

The content of the article

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

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

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

Soil science: history, relationship with other sciences.

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

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

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

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

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

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

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

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

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

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

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

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

Soil study methods.

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

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

Soil formation.

The process of soil formation.

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

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

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

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

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

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

Soil formation factors.

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

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

Soil-forming rocks.

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

Climate.

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

Vegetation, animals and microorganisms.

Vegetation.

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

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

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

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

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

Microorganisms.

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

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

Animal world.

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

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

Relief

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

Soil age.

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

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

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

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

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

Soil and groundwater.

Water is the medium in which numerous chemical and biological processes take place in the soil. Where groundwater is shallow, it has a strong effect on soil formation. Under their influence, the water and air regimes of soils change. Groundwater enriches the soil with the chemical compounds it contains, sometimes causing salinization. Waterlogged soils contain an insufficient amount of oxygen, which causes the suppression of the activity of certain groups of microorganisms.

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

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

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

Soil composition.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Sometimes the composition of the soil air may contain some gases penetrating through the strata of rocks from their places of accumulation; special gas geochemical methods for prospecting for mineral deposits are based on this.

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

Water and thermal regimes of the soil.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Morphological features of soils.

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

Soil classification.

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

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

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

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

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

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

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

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

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

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

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

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

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

Basic regularities of soil geography.

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

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

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

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

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

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

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

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

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

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

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

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

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

Natalia Novoselova

Literature:

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



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

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

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

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

For example, in the temperate latitudes of North America, natural zones are located in the meridional direction, which is associated with the influence of the Cordilleras, which prevent the passage of moist winds from the Pacific Ocean into the interior of the mainland. In Eurasia, there are almost all zones of the Northern Hemisphere, but their width is not the same. For example, the zone of mixed forests gradually narrows from west to east as the distance from the ocean increases and the continentality of the climate increases. In the mountains, natural zones change with height - high-risezonation . 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). The animal world 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 its thin layer, as a result of washing the soil, a whitish layer is formed, which in appearance looks like ash. Therefore, such soils are called podzolic. The vegetation is represented by various types of coniferous forests in combination with small-leaved ones.

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

Tundra and forest tundra

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

polar deserts

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

Altitude zones

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

Table "Natural areas"

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