Desert soil: types and characteristics, formation conditions and fertility

A desert is a natural area with a completely or partially flat surface, with sparse vegetation or its absence, with a fauna characteristic only of it. Desert soils are also different from all others. Consider where deserts are located, how they are formed, their climatic conditions, classification. What plants grow in desert and semi-desert lands and their economic use.

Features and location

Deserts cover 14% of the land surface. Sahara - the largest and most famous of them, is located in Africa. But not only on this continent there are desert lands, the geographical position of the deserts is the temperate zone of the Northern Hemisphere, the subtropics and tropics of both hemispheres.

Soils are extremely poorly developed, water-soluble s alts predominate in the soil solution, s alt crusts are common, there is little organic matter. The humus content is 1-2%, which is why the fertility of these soils is low. Without improvement measures, it is impossible to grow anything on desert land.

Educational conditions

The geographical distribution, emergence and gradual development of deserts were influenced by such factors: intense solar radiation, low rainfall throughout the year. The volume of precipitation is determined by the latitude of the area, the conditions for the circulation of air masses, the features of the relief, the location of the area inside the mainland or close to the oceans.

Due to the arid climate and sparse vegetation, the soil-forming process is discontinuous, humus is formed slowly. There are few green plant residues, mainly root mass. Organic matter undergoes mineralization during the season, and is not converted into humic substances.In summer, when it is dry and hot, there is a cessation of biological processes. Desert soils are thin and structureless. Due to insignificant precipitation and strong evaporation, carbonates accumulate in the upper horizons, and soluble s alts and gypsum accumulate below.

Climate

Warm and dry climate is determined by geographical location. Air with low humidity does not protect the surface from sunlight. The normal temperature can reach +50 °C, and the maximum - +58 °C. At night, the air cools quickly, as the hot earth cools quickly, there may be frost. Daily fluctuations can be 30-40 ° C in tropical deserts, in the temperate zone - 20 ° C.

Summers in such temperate deserts are hot, winters are very severe, there can be frosts down to -50 ° C, while little snow falls. A feature of deserts of all types are constant strong winds at a speed of 15-20 m/s.Desert winds lift and carry loose surface material, producing the famous sand and dust storms.

Relief and soil-forming rocks

The formation of the relief of desert territories occurs under the constant action of erosion from water and wind. Watercourses in this natural area are permanent and temporary. The permanent ones are large rivers such as the Nile, Colorado, whose sources are outside the deserts they flow through, which is why they do not dry up.

Temporary streams of water are formed after heavy rains, not being fed with moisture, they quickly dry up. Many streams carry sand, silt, gravel with them, which then create the relief of the desert.

Wind is another factor in soil formation. He, like water, can create different relief forms. The wind carries the sand, both across the desert and beyond its borders.Sand acts on rocks, creating bizarre shapes that resemble towers, spiers, windows, arches. Such forms can be found in the North American deserts.

Often the wind blows fine earth from the top layer of the soil profile, leaving pebbles in place. Elsewhere in the desert, sand and dust settle and sand dunes form.

Vegetation

The species composition of desert plants is often represented by species characteristic of this ecosystem. For the continental desert lands of the temperate zone, plants of the sclerophilic type are characteristic, that is, leafless shrubs and shrubs. Herbaceous species are ephemera and ephemeroids. Vegetation is sparse, plants can grow from each other at a distance of several meters, in general, the territory of desert zones is covered with plants by no more than half, in the most severe conditions it may not be at all.

In the deserts of Africa and Arabia, located inland, xerophilic shrubs and drought-resistant perennial grasses predominate, as well as succulents. There is no vegetation at all on the dunes and areas covered with a crust of s alt deposits.

In the deserts of Australia, Central Asia and North America, the vegetation is richer, there are not so many areas without plants. Between the sandy ridges in the depressions, acacia of a low-growing species, eucalyptus, grows, on the soil with a predominance of pebbles and crushed stone, half-shrub s altwort grows.

Succulent plants dominate the oceanic deserts of Africa and America. In saline areas of all the deserts of the world, similar species are found - succulent perennial shrubs and annual s altworts.

In oases, river deltas and valleys, the species composition of plants is different. Asian deserts are characterized by deciduous tree species (elm, willow, turanga poplar), tropical and subtropical evergreens grow, such as oleander and palm.

Classification

Desert soils differ in composition, structure and morphological features.

Brown semi-desert

The main characteristic of brown semi-desert soils is a thin humus layer, which is formed under the influence of an arid climate and low plant productivity. Plant litter quickly decomposes and mineralizes, and ash elements are formed from it. Among them, most of all are alkali metal s alts, which make the earth alkaline. The humus content is 1-2.5%, the reaction is slightly alkaline.

Gray-brown

Distributed only in Asia - in China, Afghanistan, Mongolia, countries of Central Asia, Iran. According to the mechanical composition, they are sandy, with a porous soil crust, a layered horizon located under it. The next lower layers contain carbonates and gypsum.

Takyrs

Dry clay saline soils covered with large cracks with a characteristic pattern. The dimensions of the takyr can be several square meters. meters or several square meters. kilometers.

Takyrs are found in hollows, in which water remains after rains, and then completely dries up, and the silty soil cracks. Salinization is formed due to closely located groundwater - 1.5 m, which carry minerals to the surface.

Meadow-brown semi-desert

Soils are formed in areas with pronounced surface waterlogging or with a close occurrence of soil water (2-6 m). The formation of these soils under periodic moistening causes an increased (2.5-4%) humus content, some gleying, alkalinity or salinity.

Meadow semi-desert and desert

This type of soil is found in estuaries, in terraces of lakes and rivers. The profile is formed under the influence of soil or irregular flood moisture, runoff after snowmelt. Water accumulates in relief depressions and feeds plants for some time. Meadow semi-desert soils contain 1.5-3% humus, saline to varying degrees, contain carbonates.

Brown desert steppe

These are carbonate, low-humus (1.5-2.5%) soils, formed under the influence of a dry, cold climate, mainly on sandy-loamy sandy deposits. The vegetation is represented by grasses and wormwood. Poor in humus (only 0.7-1.4%), the reaction in the upper layer is slightly alkaline, in the lower horizons it is alkaline.

Takyr desert

Formated from meadow soils under the influence of desertification as a result of subsidence of groundwater. Takyr-like soils are currently moistened not by ground moisture, but by atmospheric moisture. The profile is not fully developed, elevated s alt levels. The vegetation is s altwort and wormwood.

Sand desert

They consist of winnowed sands and ancient alluvial deposits rich in mineralogical composition. They are covered with shrubs, near which sedges and cereal herbaceous plants grow.

Use of semi-desert and desert soils

Desert lands are used for animal husbandry as year-round pastures for camels and sheep. In the clay deserts, where conditions are not so favorable because the soil waters are deeper, there are also pastures, they are fed by temporary streams and rivers that fill with water in spring. In the valleys of large rivers, agriculture is practiced with the use of irrigation; in such places, soil fertility increases. They grow vegetables, rice, cotton, grapes.

The economic use of deserts is also possible due to another important characteristic - the presence of minerals - gas and oil.

Climatic conditions of deserts - high air temperature, little moisture, dry air, intense insolation, sparse vegetation - form soils of a special type. They are not fertile, but give life to adapted plant and animal species. Can be used in agriculture, subject to cultivation and constant irrigation.

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