In the green areas where broad-leaved species grow, gray forest soils are formed. The natural zone of their location is the territory of a temperate continental climate. These are areas where there is an increased number of sunny days and there is no heavy rainfall.
Spread
Gray forest soils are located in vast territories of Russia. They occupy vast territories in Canada and the USA. These are forest-steppe zones bordering taiga regions in the north and the steppe region in the south.
Gray forest soils located in Russia represent a continuous strip in the European part of the country. They are found in a vast area from the Ukrainian border to the Ural Mountains. They capture gray forest soils and the territory located a little east, to the very Altai. This is a zone of the West Siberian Lowland. The territory of gray soils is 3.5% of the total area of the Russian Federation. Below we consider what gray forest soils are. The characteristics in Russia of these land lands and their main use in the agro-industrial complex will also be highlighted in this article.
Relief
In general, the landscape landscape of the gray soils is flat. In the European part of forest-steppes this plain is undulating and undulating. In Asian, in addition, also with flat zones. In the forest-steppes there is a whole network of ravines and gullies. Such a relief also affects the characterization of gray soils, since thanks to it there is a natural drainage of the territory.
Formation Conditions
How do gray forest soils develop? Education conditions for them are optimal only with a continental climate. This is the average annual temperature from plus seven degrees in the western regions to minus four and a half in the east. Also, a certain amount of precipitation falls during the year affects the formation of lands. In the territories west of the Ural Mountains it is 500-600 mm, and east of these ridges - 300 mm. In this case, an equal ratio of precipitation and their evaporation is observed. Throughout the territory where gray forest soils are formed, the same average July temperatures are observed. They are 19-20 degrees.
Gray forest soils form under vegetation represented by grassy deciduous forests. To the west of the Dnieper, they have an oak-hornbeam composition. To the east, right up to the Urals, lindens and oaks grow in the forests. Ash is sometimes found. To the east of the Ural ranges, aspen and birch forests predominate. Further, to Transbaikalia, larch appears.
Due to the high mass of deciduous deciduous trees, gray forest soils have certain properties. The characteristic of their composition indicates a high content of ash elements and calcium. All these substances enter the soil with litter, the mass of which, according to scientists, ranges from 70 to 90 centners per hectare.
On the territory of forest-steppes there are parent rocks represented by loams. These are carbonate deposits.
In the conditions of grassy broad-leaved forests, two main processes occur in the earth. Without them, gray forest soils could not have formed. The characteristic of the forming layer is directly related to these processes. The first of them proceeds under the influence of a downward flow of water from precipitation falling to the ground. The result of this process is the removal of soil formation products and their weathering in the lower horizons of the rocks. Sometimes all these substances pass into the layers of loam.
The second, no less important process, is associated with the fact that gray forest soils form 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 organo-minerals associated with calcium. To a small extent, a podzol-forming process also takes place in the forest-steppes. It enriches the upper layers of the soil with one and a half oxides 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 unredeemed dead grass and decay. Next 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 hue. In this layer, where organomineral glandular compounds accumulate, glossy inclusions are often found. The following is a yellow-brown mother breed.
The following subtypes are distinguished from the type of gray soils:
- light gray;
- gray
- dark gray.
This classification depends on the nature of the processes of podzolization occurring in the earth.
Chemical characteristics of gray soils
The composition and quantity of micro- and macrocells depends on the conditions of formation of all layers of the horizon. What chemical properties do gray forest soils have? The characteristic obtained in the study of their aqueous solution allows us to talk about the existing slightly acidic and acidic reactions. In addition, the results of laboratory analysis indicate a low saturation of such soils with bases and a reduced amount of silty particles in the first two horizons.
Conducted chemical studies can fairly accurately indicate to which subtype these or other gray forest soils belong. Their characteristic is different. So, dark gray forest soils are distinguished by a large amount of accumulated humus. They found the predominance of humic acids over sulfonic acids. What is the difference between dark gray forest soil? The characteristic given as a result of chemical analyzes confirms the accumulation of calcium in it. This item is in the upper horizon.
A characteristic of gray forest soil obtained as a result of a chemical study indicates the poverty of its upper horizons by one and a half oxides and significant enrichment with silicic acid. This composition confirms the course of the podzolization process. This is most pronounced in the light gray subtype of soils. Less in dark gray. Depending on the subtype of the soil, they also have different chemical properties. For example, light gray have an acid reaction. However, 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, there is some unsaturation with bases. However, this is less pronounced than that of the light gray subtype.
The third type of soil has the most favorable chemical properties. Dark gray soils have a weakly acid reaction and a high saturation with bases. In addition, they contain a high content of humus, phosphorus, calcium and nitrogen.
An important role is played for those who study gray forest soils, characteristic.
A 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
The properties of land plots of the forest-steppe zone largely depend on the content of humus in them. The physical characteristics of gray soils are also affected by the mechanical composition of the initial parent rocks.
The upper horizons of these areas are characterized by high porosity, reaching 60%. As you move down the profile, soil density increases. This is due to a decrease in the concentration of humus. Moreover, these physical properties have some differences depending on the subtype of the soil in question. So, in dark gray rocks, the density of even the lower horizons is the smallest. This is due to the large humus content and more pronounced structuredness.
One of the physical characteristics is the density of the illuvial horizons. For all subtypes of gray soils, it is quite high. Its value reaches from 1.5 to 1.65 grams per cubic centimeter. As for the total porosity, it ranges from 50 to 60%. And in the upper horizons - from 40 to 45%. The porosity characteristic in the light gray subtype is inclined to the capillary type. This feature leads to a decrease in the permeability of the soil.
As for the dark gray subtype, its physical properties are most favorable. This soil layer is characterized by high moisture capacity, which allows the entire plant world to obtain much-needed water for it. The gray and light gray subtypes of land of the forest-steppe zone have poor physical characteristics. This is a low humus content, and a small percentage of silt, and the presence of a large number of dusty fractions. All these qualities contribute to the destructuring of the upper layers of the horizon after their plowing. Such lands quickly swim, and crusts form on their surface.
The microstructures of various subtypes of gray soils are unlike each other in terms of water resistance. For example, a light gray look after plowing quickly condenses. This is due to the fact that in this subtype of soil the presence of water-resistant aggregates is observed whose dimensions exceed 0.25 mm.
Biological characteristics
The 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 main organic substance of the very first layer of the profile. It has a lot of phosphorus, nitrogen and other elements. Humus formation occurs from deciduous and plant decay, as well as from dead plant roots with the active participation of microorganisms.
Thermal mode
According to this indicator, gray forest soils have quite favorable properties. Over a long period, lasting from April to December, a positive temperature is observed throughout their profile. Freezing occurs with the beginning of winter, and sometimes from January. By April, a layer with a depth of 50 to 70 cm is already completely thawing.
In the central and western zones of forest-steppes, soils are classified as a facies subtype in terms of heat supply. Here you can observe periodic freezing and thawing of the upper layer throughout the winter period.
A different thermal regime of soils is characteristic of Western Siberia. Here, a prolonged freezing of the layers of the horizon occurs. In addition, with the onset of spring, soils thaw more slowly. This is due to severe frosts, as well as with small snow cover. Field work in these territories begins to be carried out only in May. However, even at this time negative temperatures still remain on the lower horizons.
Air mode
This characteristic is a combination of a large number of phenomena. Moreover, they are all associated with the entry of air into the soil, its further movement along it, as well as the flow rate. This also includes the phenomena of gas exchange occurring 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. Moreover, in the upper layers this process is much more intensive.
Water mode
Gray forest soils are characterized by periodically flushing type of this indicator. As a rule, heavy rainfall in the fall moistens the earth only by 50 cm. The moisture penetrates deeper at the time of spring snowmelt. In this regard, the thickness of soil wetting depends on the thickness of the winter cover and the volume of melt water runoff.
A certain characteristic of the water regime is observed in areas with a rugged topography. Here, the maximum moisture consumption in the summer period can be 20% and cover a soil layer having a meter thickness.
A completely different water regime has soils located in forests. Here in winter there is a large accumulation of snow. In this regard, in the spring, the soil is moistened much more intensively. However, later it is used by the deep root system of trees. This drains the soil to a depth of 4 to 5 meters.
Nutritional mode
The most favorable properties for this indicator are dark gray forest soils. They are characterized by high natural fertility due to the large volume of humus, phosphorus and nitrogen located in them.
The nutritional regime of the soil also depends on its cultivation and the use of fertilizers. In such cases, the upper layers of the horizon will contain more nutrients.
The nutrient regime of soils is affected by the content of hydrolyzable nitrogen in them. Light gray soils are especially poor in this element. One of the indicators of land fertility is the presence of mobile phosphorus in them. The maximum amount of this element is in residual carbonate soils.
The summer period contributes to the activation of chemical, biological and other processes that occur in arable soils. In the middle of the warm season, an increase in hydrolytic and metabolic acidity occurs. In this regard, the saturation of soils with bases decreases.
Use in economic activities
In the country's agro-industrial complex, the zone in which gray forest soils are located is widely involved. The fertility of these lands allows people to successfully grow various crops on them. In addition, gray forest soils occupy 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, corn and sugar beets, flax, potatoes, etc. are grown . Gardening has become widespread in the European part of forest-steppes.
All subtypes of gray soils are included in the economic turnover. At the same time, a person seeks to increase their fertility by applying a range of measures. A powerful fertile arable layer is created by fertilizing and grass planting. This improves the physical characteristics and nutrition of the soil, and also reduces the ability to form crusts on the surface layer. In addition, land with high acidity is subjected to liming to improve their characteristics.
The process of cultivation of forest gray, as well as light gray soils is possible with the deepening of the arable layer. This event is accompanied by fertilizer application. If necessary, and liming the land.
The fertility of dark gray soils is increased by the systematic application of fertilizers. And to eliminate their increased hydrolytic acidity, phosphorite flour is used.
Agricultural use of gray soils should be accompanied by erosion control measures. This is especially true of the European territory of the forest-steppe zone. To take such measures, they cultivate the soil across the slope, arrange earthen ridges, etc.