Gray forest soils: characteristics, conditions of formation, properties

In green massifs where broadleaf breeds grow, gray forest soils are formed. The natural zone of their location is the territory of the temperate continental climate. These are areas where there is an increased number of sunny days and there are no heavy rainfall.

Spread

Gray forest soils are located on vast territories of Russia. They occupy huge territories in Canada and the USA. These are forest-steppe zones bordering on the north with taiga areas, and in the south - with the steppe region.

Gray forest soils on the territory of Russia represent a continuous band in the European part of the country. They are found in a vast area from the Ukrainian border to the Ural Mountains. Seize the gray forest soils and the territory, located somewhat to the east, up to the Altai. This is the zone of the West Siberian lowland. The territory of gray soils is 3.5% of the total area of the Russian Federation. Below we will consider what gray forest soils are. Characteristics in Russia of these land areas and their main use in the agro-industrial complex will also be covered in this article.

Relief

In general, the character of the landscape of the territory of the presence of gray soils is flat. In the European part of the forest-steppe it is flat and wavy. In Asian, in addition, also with flat zones. In the forest-steppe there is a whole network of ravines and gullies. Such a relief also affects the characteristics of gray soils, because due to it, the natural drainage of the territory occurs.

Formation conditions

How do gray forest soils develop? The conditions of formation for them are optimal only under continental climate. This is the average annual air temperature from plus seven degrees in the western regions to minus four and a half in the east. Also, the formation of land is affected by a certain amount of precipitation during the year. In the territories west of the Ural Mountains it is 500-600 mm, and to the east of these ridges - 300 mm. At the same time, an equal ratio of precipitation to precipitation and their volatility is observed. On the whole territory where gray forest soils are formed, the same average temperatures for July are observed. They are 19-20 degrees.

Gray forest soils form under the vegetation represented by herbaceous deciduous forests. To the west of the Dnieper they have oak and hornbeam composition. To the east, up to the Urals, in the forests grow lindens and oaks. Sometimes there is ash. The east and east of the Ural ranges are dominated by aspen and birch forest tracts. Further, to Transbaikal, larch appears.

Due to the high mass of deciduous trees, certain properties have gray forest soils. The characteristic of their composition indicates a high content of ash elements and calcium. All these substances enter the soil with a litter, the mass of which, according to scientists, is from 70 to 90 quintals per hectare.

In the forest-steppe there are soil-forming rocks represented by loam. These are carbonate deposits.

In the conditions of grassy broad-leaved forests , two main processes occur in the earth. Without them, gray forest soils would not have formed. The characteristic of the forming layer is directly related to these processes. The first of them proceeds under the influence of the descending current of water from precipitation falling on the earth. The result of this process is the removal of the products of soil formation and their weathering in the lower horizons of rocks. Sometimes all these substances pass into layers of loam.

The second, no less important process, is connected with the fact that gray forest soils are formed under deciduous trees and grasses. Dead vegetation, rich in minerals, is deposited in the upper horizon in the form of organic residues. In this case humus is formed in the surface layers of the soil. This layer is rich in organomineral substances associated with calcium. To a small extent, the podzol formation process is also taking place in the forest-steppe. It enriches the upper layers of the soil with sesquioxides and oxides of magnesium, calcium and many other elements.

Structure

Gray forest soils (see photo below) are represented by five layers.

The uppermost of them has a thickness of 3 cm. This is a forest litter consisting of ungathered dead grass and fall. Further, there is a more powerful granular gray layer, whose thickness is 12 cm. It is formed from humus and has a loose structure. The depth of the third layer is 12 cm. Its soil is painted in walnut or light gray. In this layer there are inclusions of silica and humus. Further, the soil acquires a brown shade. In this layer, where organomineral ferruginous compounds accumulate, glossy inclusions are often found. Below follows the parent rock of yellow-brown color.

Of the type of gray soils, subtypes are distinguished:

• Light gray;
• Gray;
• Dark gray.

This classification depends on the nature of the podzolization processes occurring in the earth.

Chemical characteristics of gray soils

The composition and quantity of micro-, and also macro-elements, depends on the conditions for the formation of all layers of the horizon. What are the chemical properties of gray forest soils? The characteristic obtained in the study of their aqueous solution allows one to speak of the weakly acidic and acidic reaction present. In addition, the results of laboratory analysis indicate a low saturation of such soils with bases and a reduced amount in the first two horizons of muddy particles.

Conducted chemical studies can sufficiently accurately indicate which subtype belong to which gray forest soils. Their characteristics are different. Thus, dark gray forest soils are distinguished by a large amount of accumulated humus. They found a predominance of humic acids over fulphonic acids. What is the difference between dark gray forest soil? The characteristic given as a result of the conducted chemical analyzes confirms the accumulation of calcium in it. This element is in the upper horizon.

The characteristics of gray forest soil, obtained as a result of the chemical study, indicate the poverty of its upper horizons by sesquioxides and a significant enrichment with silicic acid. Such a composition confirms the course of the podzolization process. This is most clearly expressed in the light gray subtype of soils. Less - in dark gray. Depending on the subtype of the soil, there are also different chemical properties. For example, light gray has an acidic reaction. In this case, they do not differ in the saturation of the base.

The characteristic of gray forest soil indicates that this subtype also has an acid reaction. In this case, some unsaturation with bases is observed. However, this is less apparent than in the light gray subtype.

The third type of soil has the most favorable chemical properties. Dark gray soils have a weak acid reaction and a high saturation with bases. In addition, they contain a high content of humus, phosphorus, calcium and nitrogen.

An important role plays for those who study gray forest soils, characteristics.

The table, in which all the properties of the various subtypes are presented, will make it possible to better remember all the data obtained by the researchers.

physical characteristics

Properties of land plots of the forest-steppe zone largely depend on the content of humus in them. The physical composition of the primary soils influences the physical characteristics of gray soils.

The upper horizons of these sections are characterized by high porosity, reaching 60%. As you move down the profile, the soil density increases. This is due to a decrease in the concentration of humus. However, these physical properties have some differences, depending on the subtype of the soil in question. Thus, in dark gray rocks the density of even the lower horizons is the smallest. This is due to the great humus content and more pronounced structuring.

One of the physical characteristics is the density of illuvial horizons. In all subtypes of gray soils, it is quite high. Its value reaches from 1.5 to 1.65 grams per cubic centimeter. With regard to the total porosity, it is in the range of 50 to 60%. And in the upper horizons - from 40 to 45%. The porosity characteristic in the light gray subtype tends to the capillary type. This feature leads to a decrease in water permeability of the soil.

As for the dark gray subtype, its physical properties are most favorable. This soil layer is characterized by a large water capacity, which allows the entire plant world to obtain much-needed water for it. Gray and light gray subtypes of the forest land of the forest-steppe zone have low-favorable physical characteristics. This is a low content of humus, and a small percentage of silt, and the presence of a large amount of dusty fractions. All these qualities contribute to the de-structuring of the upper layers of the horizon after their plowing. Such lands quickly swim, and on their surface is the formation of a crust.

The microstructures of different subtypes of gray soils are not similar to one another and are waterproof. For example, a light gray appearance after plowing is quickly compacted. This is due to the fact that this soil subtype has a presence of water-resistant aggregates, the dimensions of which exceed 0.25 mm.

Biological characteristics

Humus of gray soils accumulates in its upper horizons and represents a whole group of high molecular weight related compounds. This biological component is the basic organic matter of the very first layer of the profile. It contains a lot of phosphorus, nitrogen and other elements. The formation of humus occurs from deciduous and vegetative decays, as well as from dead roots of plants with the active participation of microorganisms.

Thermal conditions

According to this indicator, gray forest soil properties are quite favorable. Over a long period, lasting from April to December, a positive temperature is observed throughout their profile. Freezing begins with the onset of winter, and sometimes even in January. By April, a layer of depth from 50 to 70 cm already completely melts.

In the central as well as in the western zone of the forest-steppe, the soils are referred to the facies subtype for heat supply. Here one can observe the periodic freezing and thawing of the upper layer throughout the winter period.

A different thermal regime of soils is typical for Western Siberia. Here there is a long freezing of the layers of the horizon. In addition, with the onset of spring, the soil is thawed more slowly. This is due to severe frosts, and also with a small snow cover. Field work in these territories begins to be conducted only in May. However, at this time, negative temperatures still remain on the lower horizons.

Air mode

This characteristic is a collection of a large number of phenomena. And all of them are related to the entry of air into the soil, its further movement along it, and also the flow. This includes the phenomenon of gas exchange, which occurs between the layers of the horizon and the surrounding atmosphere.

Soil air with the advent of the next season undergoes some changes in its composition. And in the upper layers of this process is much more intense.

Water regime

Gray forest soils are characterized periodically by the washing type of this indicator. As a rule, the heavy rainfall falling in the autumn moistens the earth only by 50 cm. Deeper moisture penetrates at the moment of spring melting of the snow. In this regard, the thickness of soaking of soils depends on the thickness of the winter cover and the volume of runoff of thawed waters.

A certain characteristic of the water regime is observed in zones with a rugged terrain. Here, the maximum moisture consumption in summer can be 20% and cover a layer of soil that is a meter thick.

A completely different water regime has soils in the forest. Here in the winter there is a large accumulation of snow. In connection with this, the soil is moistened much more intensively in spring. However, later it is used by the deep root system of trees. This drains the soil to a depth of 4 to 5 meters.

Feeding mode

The most favorable properties for this indicator are dark gray forest soils. They are distinguished by high natural fertility due to the large volume of humus, phosphorus and nitrogen in them.

The nutrient regime of the soil depends on its cultivation and the application of fertilizers. In such cases, the upper layers of the horizon will contain more useful substances.

The nutrient regime of soils is affected by the content of hydrolyzable nitrogen in them. Particularly poor in this element are light gray soils. One of the indicators of the fertility of the earth is the presence of mobile phosphorus in them. The maximum amount of this element is found in residual-carbonate soils.

The summer period promotes the activation of chemical, biological and other processes that occur in arable soils. In the middle of the warm season, hydrolytic and exchange acidity increase. In this connection, the saturation of soils with bases is reduced.

Use in economic activities

In the agro-industrial complex of the country, a zone in which gray forest soils are located is widely used. The fertility of these lands allows people to successfully grow various agricultural crops on them. In addition, gray forest soils take their place in the structure of pastures and pastures, as well as hayfields.

In the forest-steppe zones developed for agriculture, spring and winter wheat, maize and sugar beets, flax, potatoes, etc. are grown . In the European part of the forest-steppe, horticulture has become widespread.

All subtypes of gray soils are included in the economic circulation. At the same time, a person seeks to increase their fertility by applying a whole range of measures. A powerful fertile arable layer is created by applying fertilizers and grass seeding. This improves the physical characteristics and diet of soils, and also reduces the ability to form crusts on the surface layer. In addition, the lands with high acidity are subjected to liming to improve their characteristics.

The process of acculturation of forest gray, as well as light gray soils is possible even with the deepening of the arable layer. This event is accompanied by the introduction of fertilizers. If necessary, liming is also carried out.

The fertility of dark gray soils is increased by the systematic introduction of fertilizers. And to eliminate their increased hydrolytic acidity, phosphate flour is used.

Agricultural use of gray soils must be accompanied by erosion control measures. Especially it concerns the European territory of the forest-steppe zone. For the adoption of such measures, the soil is processed across the slope, earth ridges are arranged, and so on.