Genesis,hydrology, and properties of soils in mesodepressions waterlogged by surface water in the northern Ryazan forest-steppe

On the interfluves and in small depressions of the Ryazan forest-steppe, under periodic stagnation of surface water, acid chernozem-like soils with a relatively thick humus horizon, podzolic horizons, and marble-colored gleyed B1 and B2 horizons are formed. The eluvial horizons of these soils contain Mn-Fe nodules, and dark humus coatings occur in the illuvial horizons. In the spring, the eluvial horizons of these soils are excessively moistened and gravitational water stagnates on the soil surface for 3–4 weeks. The formation of the acid light-colored eluvial horizons of the soils on leached rocks is related to gleying under the conditions of the stagnant-percolative regime. Their total thickness is 15–25 cm and more. According to the properties of their solid phase, these horizons are similar to the podzolic horizons of soddy-podzolic gleyed soils. These soils have not been represented in the classification systems of soils of the USSR and Russia. Based on the principles of the substantial-genetic classification, one of the authors of this article [9] referred this soil to gleyed podzolic chernozem-like soils, thus, considering it as an individual genetic soil type. The gleyed podzolic chernozem-like soils differ from the leached chernozems by their low productivity and difficulty of tillage. In humid and moderately moist years, the death of crops or a reduction in yield are probable because of the excess of moisture.     

Concretions in typical chernozem,gleyed chernozem-like,and solonetzic chernozem-like soils of the southern Tambov Lowland

A system for the diagnostics of chernozemic soils of the Tambov Lowland based on concretions is proposed for agricultural and reclamation purposes. The relationships between the structure and composition of the carbonate concretions, the long-term water regime of the soils, and the productivity of the crops have been established. The dense concretions in the typical chernozem testify to the depth of the seasonal wetting; the angular-rounded concretions in the deeply gleyed chernozem-like soil, to the upper boundary of the capillary fringe; and the angular concretions with sharp edges and cavities in the gleyic chernozem-like soils, to the groundwater table. In the chernozem-like soils that were waterlogged with bicarbonate-sodium water, the black angular concretions were formed in the solonetzic horizons, while the weakly compacted light-colored ones, in the zone of the capillary fringe. Humic acids were responsible for the color of the dark neoformations, and fulvic acids predominated in the light-colored ones. The appearance of black fine nodules indicated periodic surface water stagnation. Manganese predominantly accumulates in these nodules. The structure of the Mn-Fe concretions in the plow horizon observed at a magnification of 40–50 times has a diagnostic importance. The short-term (2–3 weeks) water stagnation leads to the formation of fine-stratified concretions, and the long-term (up to 1.5 months) stagnation promotes the formation of uniform porous ones. The solonetzic process induced by the bicarbonate-sodium water results in the appearance of mottled concretions.     

Solonetzic process in postagrogenic and postameliorative conditions of the Kamennaya Steppe area

The physicochemical conditions and morphological features of solonetzic process in soils of chernozemic solonetzic complexes were studied in the area of solonetzic experimental station no. 1 in the Kamennaya Steppe area in 55 years after a single application of ameliorative measures (earthening, gypsuming, and manuring) and cessation of the annual plowing. It was found that the modern soil-forming factors favor the development of soil processes inherent in native chernozems and solonetzes prior to their plowing and amelioration. They cause the restoration of the humus horizon in chernozems and the morphological differentiation of solonetzes after the cessation of plowing. Active postameliorative and postagrogenic restoration of solonetzic features is related to the preservation of the physicochemical conditions (the low concentration of salts and the presence of exchangeable sodium) in the soil profile. The humus horizon of chernozems applied over the surface of solonetzes is characterized by the appearance of solonetzic features under hydromorphic conditions.     

Estimation of the areas of salt-affected soils in the European part of Russia on the basis of a digital map of soil salinization on a scale of 1 : 2.5 M

A digital version of the map of salt-affected soils on a scale of 1 : 2.5 M has been used to calculate the areas of these soils in the four federal okrugs (the Southern, Central, Volga, and Northwestern) of European Russia. The total area of soils with soluble salts in the upper meter reaches 23.3 million ha. More than half of them are solonchakous soils (with soluble salts in the layer deeper than 30 cm), and about 25% are saline from the surface. Soils of sulfate and chloride-sulfate salinization predominate (>50% of the area of salt-affected soils). Alkaline soda-saline soils and soils with the participation of soda comprise about 6%. We consider this value to be underestimated and requiring refinement, because soils of solonetzic complexes with neutral salts in the upper horizons may also contain soda in the solonetzic and subsolonetzic horizons, which was not always taken into consideration upon assessing the chemical composition of the salts. Solonetzes proper and solonetzic soils predominate among the salt-affected soils in the European part of Russia. The area of solonetzes is up to 9.4 million ha. The area of solonetzic soils (including solonetzic soils with salts in the layers of 0–100 and/or 100–200 cm) is 15.5 million ha. The highest percentage (32.2%) of salt-affected soils is in the Southern federal okrug.     

Properties of solonetzes on terraces of salt lakes Bulukhta and Khaki in the Caspian Lowland

A comparative assessment of pedogenetic processes in solonetzes (Calcic Gypsic Salic Solonetzes (Siltic, Albic, Cutanic, Differentic)) developing on terraces of lake depressions within the Volga–Ural interfluve of the Caspian Lowland has been performed on the basis of data on their macro- and micromorphological features and chemical, physicochemical, and physical properties. The studied soils have number of common characteristics shaped by the humus-accumulative, solonetzic, eluvial–illuvial, calcification, and gypsification processes. However, it is shown that macro- and micromorphological indicators of solonetzic processes (the development of clay–humus coatings and the character of structural units in the solonetzic (B) horizon) do not always agree with the modern physicochemical conditions of the development of this process. This is explained by differences in the degree and chemistry of the soil salinization and the depth and salinity of the groundwater. Solonetzes developing on the second terrace of Playa Khaki are distinguished by the highest water content and maximum thickness of the horizons depleted of soluble salts. They are characterized by the well-pronounced humus-accumulative process leading to the development of the light-humus (AJ) horizon. In other solonetzes, the accumulation of humus is weaker, and their topsoil part can be diagnosed as the solonetzic-eluvial (SEL) horizon. Active solodic process and illuviation of organomineral substances with the development of thick coatings and infillings in the B horizon are also typical of solonetzes on the second terrace of Playa Khaki. Micromorphological data indicate that, at present, layered clayey coatings in these soils are subjected to destruction and in situ humification owing to the active penetration of plant roots into the coatings with their further biogenic processing by the soil microfauna. The process of gleyzation (as judged from the number of Fe–Mn concentrations) is most active in solonetzes developing on the first terrace of Playa Khaki. These soils are also characterized by the highest degree of salinization with participation of toxic salts. The maximum accumulation of gypsum is typical of the heavy-textured horizons.     

Soil Cover of the Svetloyarsk Irrigation System after 50 Years of Reclamation Practices

The state of irrigated soils of the Svetloyarsk irrigation system (Volgograd oblast) after 50 years or irrigation and ameliorative impacts has been assessed with the use of published and new field data, cadastral materials, and remote sensing materials. In the recent two decades, the area of regular irrigation and the volume of irrigation water have decreased, which has led to the lowering of the groundwater level to the depth of 5 m and more. The pattern of sown areas is characterized by a rise in the portion of winter cereals. Surface planing during the construction of the irrigation system led to a considerable transformation of the soil cover. On convex elements, solonetzic and other topsoil horizons were almost completely cut off. In many areas, they were replaced by a mixture of different horizons, including carbonaceous material. There are now significant areas of soils of different geneses with carbonates from the surface. Former solonchakous and slightly solonchakous soils are now at the stage of deep desalinization: soluble salts in them have been washed to the second meter, where slightly or moderately saline horizons with a predominance of sulfates have been formed. Irrigated areas on satellite images are specified by spotty patterns differing from those of natural solonetzic soil complexes because of the significant transformation of the soil cover during the construction and operation of irrigation system. The anthropogenically transformed soils can be mapped. Soil maps reflecting the modern state of the of soil cover of irrigated areas are given.     

Morphological and chemical properties of the meadow-semidesert soil complexes of the Khaki playa (the Caspian Lowland) and the influence of the biogenic factor on them

The initial stage of the development of the complex soil cover pattern in the Caspian Lowland was studied. The obtained data made it possible to reveal the specific features of the morphological and chemical properties of the soils on terraces of the Khaki playa and the role of burrowing animals in the formation of the microtopography and complex soil cover patterns on the youngest surfaces. The soil cover of the studied area consists of three-component complexes: light-humus quasi-gley solonetzes on relatively flat background surfaces, zooturbated solonetzes on microhighs, and humus quasi-gley soils in microlows. The layered deposits of the Khaki playa terraces and the shallow depth of the saline groundwater are responsible for the specificity of the modern salinization of the studied solonetzes. The distribution of the salts in their profiles has a sawshaped patter, which is related to the nonuniform texture of the deposits. On the microhighs composed of the earth extracted from 5- to 7-year-old suslik burrows, specific zooturbated solonetzes are formed. The known age of these formations makes it possible to determine the rate of the desalinization of the gypsum- and salt-bearing material extracted onto the soil surface and the rate of the salt accumulation in the lower part of the solonetzic horizon and in the subsolonetzic horizons in comparison with the data on the solonetzes of the background flat surfaces. The specific features of the soils in the closed microlows suggest that these soils have a polygenetic origin. The features of the recent hydromorphism predetermine the specificity of their morphology.     

Chemical properties of soils in closed depressions of the northern Tambov Plain

Chemical properties of chernozem-like soils in closed depressions on different relief elements in the northern part of the Tambov Plain differ significantly. The soils with podzolic features in depressions on the watershed have a high acidity and a low degree of base saturation. The soils on the above-floodplain terrace are neutral and saturated with bases. When the degree of moistening increases, the share of magnesium in the total exchangeable bases increases to 30–35%. In the soils of surface flooding under gleyzation conditions, iron is leached from the fine earth, and iron nodules are formed. In the soils formed under the impact of groundwater, iron diffusion is observed in the surface layers. In the podzolic horizons of soils on the watershed, humus acquires a fulvic-humic character. In the soils formed under the impact of groundwater and water stagnation conditions typical for gleyed soils, the Cha: Cfa ratio is higher than 1.     

Characterization of the microbial communities in the modern and buried under kurgans soils of solonetzic complexes in the dry steppes of the Lower Volga region

The microbial communities were studied in the modern and buried under kurgans (1st century AD) soils of solonetzic complexes on the dry steppes of the northern part of the Yergeni Upland. It was found that the changes in the numbers of microorganisms from different trophic groups and in the biomass of the fungal mycelium along the profiles of the modern and buried solonetzic chestnut soils and solonetzes do not differ significantly. The quantitative estimate of the impact of the solonetzic process on the spatial variability of the microbiological parameters of the soils was given on the basis of the ANOVA. As a rule, the values of the microbiological parameters in all the horizons of the modern and buried chestnut soils were 1.2–2.8 times higher than those in the modern and buried solonetzes. The influence of the degree of solonetzicity of the buried paleosols on the microbiological parameters manifested itself in the entire profile, though in each particular horizon it was only seen in the numbers of some particular trophic groups of microorganisms. The comparison between the mean weighted values of the microbiological parameters in the entire soil profiles (the A1 + B1 + B2 horizons) demonstrated an inverse relationship between the population density of the microorganisms utilizing easily available organic matter and the degree of solonetzicity of the buried paleosols. The maximum biomass of the fungal mycelium was found in the solonetzic chestnut paleosol; it exceeded the biomass of the fungal mycelium in the other paleosols (which did not differ significantly in that parameter from one another) by 1.5–1.6 times.     

Anthropogenic transformation of soils in the northern Ergeni Upland (studies at the first experimental plot of the Arshan’-Zelmen Research Station)

The results of soil studies performed in 2005–2009 at the first experimental plot of the Arshan’-Zelmen Research Station of the Institute of Forest Science of the Russian Academy of Sciences are discussed. The post-reclamation state (about 55 years after reclamation) of the soils under forest shelterbelts and adjacent croplands in the rainfed agriculture was studied. The long-term efficiency of forest reclamation and crop-growing technologies developed in the 1950s by the Dokuchaev Soil Science Institute and the Institute of Forest to reclaim strongly saline solonetzic soils was proved. In 55 years, strongly saline sodic solonetzes with sulfate-chloride and chloride-sulfate composition of salts were replaced by agrogenic soils with new properties. Under forest shelterbelts, where deep (40–60 cm) plowing was performed, the soils were transformed into slightly saline solonetzic agrozems with slight soda salinization in the upper meter and with dealkalized plowed and turbated horizons (0–20(40) cm). Under the adjacent cropland subjected to the influence of the shelterbelts on the soil water regime, strongly saline solonetzes were transformed into solonchakous agrosolonetzes with slight soda salinization in the upper 50 cm. In the plow layer, the content of exchangeable sodium decreased to 4–12% of the sum of exchangeable cations. An increased alkalinity and the presence of soda were found in the middle-profile horizons of the anthropogenically transformed soils.     

Saline-alkali soils of Russia

Diagnostics, methods of evaluation, and geography of saline-alkali (soda) soils are discussed. The saline-alkali soils include soils of different genetic types with the following chemical properties: the pH of the water suspensions equal to or higher than 8.5; the total alkalinity exceeding 1.4 meq/100 g of soil and the sum of water-soluble calcium and magnesium; and the presence of soluble “alkaline” salts in the soil profiles, the hydrolysis of which results in the alkaline reaction of the soils. The chemical properties of the saline-alkali soils are largely related to the presence of soda (Na₂CO₃, NaHCO₃) in the soils. According to their morphological properties, saline-alkali soils are divided into two groups: alkaline soils with an undiferentiated profile and without a morphologically pronounced solonetzic (natric) horizon, and alkaline soils with a pronounced natric horizon (solonetzes). Solonetzes, in turn, are divided into (a) alkaline solonetzes (with soda or with soda and neutral salts), (b) solonetzes salinized with neutral salts (saline soils) with increased alkalinity in the solonetzic and lower lying horizons, (c) saline solonetzes throughout the profile, and (d) leached solonetzes containing no soluble salts in the profile and almost no exchangeable sodium in the soil exchange complex (SEC) (“dead” solonetzes). The latter two groups of solonetzes cannot be ranked among the alkaline soils. The alkalinity of the saline-alkali soils under study is due to carbonate and bicarbonate ions (carbonate alkalinity), organic acid anions (organic alkalinity), and borate ions (borate alkalinity). The carbonate alkalinity is due to both soda (Na₂CO₃, NaHCO₃) and CaCO₃.     

Vertigenesis in soils of the central chernozemic region of Russia

On the basis of soil studies along routes and on key plots, 35 new areas of soils with definite features of vertigenesis have been identified in Belgorod and Voronezh oblasts and in the northern part of Volgograd oblast (in the Don River basin). Earlier, vertic soils were not noted for these areas. In the studied region, their portion in the soil cover is much less than 1%. All the delineated areas of vertic soils are confined to the outcrops of swelling clay materials of different origins (marine, lacustrine, glacial, and colluvial sediments) and ages (Quaternary or Tertiary) that may be found in four landscape positions: (1) in the deep closed depressions within vast flat watersheds; (2) in the bottoms of wide hollows on interfluvial slopes and, sometimes, on steeper slopes of local ravines; (3) in the hydromorphic solonetzic soil complexes, and (4) on step-like interfluvial surfaces with the outcrops of Tertiary clays. Within the studied areas, soils with different degrees of expression (six grades) of vertic properties are present. These soils belong to the type of dark vertic soils proper and to vertic subtypes of different soil types according to the Russian soil classification system; according to the WRB system, they belong to Vertisols proper and to reference soil units with a Vertic prefix in the groups of Chernozems, Phaeozems, and Solonetzes. Statistical data on the morphometric indices of the vertic properties (the depth and thickness of the soil horizons with slickensides, a wedge-shaped structure, and cracks filled with material from the upper horizons) and the depth and thickness of the Vertic horizon are analyzed.     

On the manifestation of solonetzic properties in soils of the steppe and dry steppe zones in the south of Ukraine

Solonetzic soils are widespread in the south of Ukraine; some of them are represented by low-sodium solonetzes whose diagnostics is complicated by the absence of correspondence between the low content of exchangeable sodium and the clearly pronounced features of the illuvial solonetzic horizon. The statistical treatment of available literature, personal materials, and the materials of soil surveys in the south of Ukraine demonstrated that the diagnostics of low-sodium solonetzes should be based on the assessment of the degree of illuviation in the soil profile. It was shown that the degree of correlation between the content of exchangeable sodium and the degree of illuviation of the soil profile varies in dependence on the size of the statistical sample and differs for the low-sodium and medium-sodium solonetzes. Two scales characterizing the degree of soil illuviation were developed for these soil groups. It is suggested that these scales should be applied during soil surveys in the areas with solonetzic soils.     

Salt regime of post-irrigated soils at the Kislovsk irrigation system

The study of post-irrigated and virgin soils at the Kislovsk irrigation system has shown that the salt regime of the post-irrigated soils is determined by the (1) depth and salinity of the groundwater, (2) the litho-logical structure of the soil and subsoil, (3) the local microtopography, (4) the presence or absence of a solonetzic horizon in the post-irrigated solonetzes, and (5) the portion of solonetzes in the soil cover. The post-irrigated soil complexes on the Privolzhsk sand ridge with a groundwater depth of more than 4 m do not undergo secondary salinization. At the groundwater depth of 2.0–2.6 m, post-irrigated meadow-chestnut soils remain nonsaline, chestnut soils and solonetzes with an artificially destroyed (due to deep tillage) solonetzic horizon undergo desalinization, and solonetzes with a preserved solonetzic horizon undergo salinization in the subsolonetzic layers. The post-irrigated soils of the Khvalyn undrained sea plain used for rainfed farming have become saline in the deep part of the profile, and their plow layers remain nonsaline.     

Manganese, iron, and phosphorus in nodules of chernozem-like soils on the northern Tambov Plain and their importance for the diagnostics of gley intensity

Nodules (nodules) forming in the chernozem-like soils of flat-bottomed closed depressions on the northern part of the Tambov Plain differ in their morphology and chemical composition as related to the degree of hydromorphism of these soils. The highest are the coefficients of Mn, P, and Fe accumulation in the nodules from these soils. The Fe to Mn ratio grows with the increasing degree of hydromorphism. Under surface moistening, the maximal amounts of mobile Mn and Fe compounds were extracted from the nodules of the most hydromorphic podzolic chernozem-like soils; under the ground moistening, their greatest amounts were extracted from the least hydromorphic soil—the weakly gley soil. In the first case, the content of organic phosphates in concretions amounted to 30–50%; in the second one, 2–3% of their total content. Under surface moistening, the proportion of active mineral phosphates becomes higher with the increasing hydromorphism: from 30 (podzolized soil) to 70% (gleyic podzolic soil). Under ground moistening, on the contrary, their proportion decreases from 70–89% in the weakly gley soil to 40–50% in the gley chernozem-like soil. The possibility to determine the degree of hydromorphism of chernozem-like soils based on the coefficients of bogging is shown. The expediency of using Schvertmann’s criterion in these studies is assessed.     

Soils of cryogenic subarid steppe landscapes in the Terekhol intermontane Depression of the Sangilen Upland

The soil cover of the Terekhol intermontane Depression in the Tyva Region is poorly studied. The data obtained in the 1950s do not reflect the real genetic diversity of soils and their specific character. According to these data, the soil cover was dominated by meadow-chernozemic soils under virgin steppe-like meadows. The investigations of 2007–2009 show that the disperse-carbonate chernozems, which are often solonetzic and weakly saline; the specific polygenetic dark soda solonchaks-solonetzes; and the postagrogenic chernozems, solonetzes, and agrozems are the main components of the soil cover of the depression at the present time. The described chernozems correspond mainly to the central image of southern Siberia chernozems. The investigated solonetzes are characterized by a number of evolution-genetic features that distinguish them from previously described solonetzes of Tyva and from all the solonetzic soils in the current interpretation. The chernozems and solonetzes have cryogenic features due to the cold extremely continental climate and relatively shallow continuous permafrost.     

Alkalinity of virgin solonetzes in northern Kalmykia (the Arshan-Zel’men Experimental Station)

The alkalinity of virgin solonetzes of the Ergeni Upland, Ergeni Plain, and Sarpinsk Lowland has been studied. These soils are characterized by the neutral salinization and the high alkalinity of the solonetzic and subsolonetzic horizons. The analysis of the soil water extracts demonstrated that the highest alkalinity is typical of the subsolonetzic horizons containing calcium carbonates (the B2 and BCca horizons). In the solonetzic horizons without CaCO₃, the alkalinity is lower despite the high exchangeable sodium percentage (up to 42%). The alkalinity of the solonetzic and subsolonetzic horizons may be conditioned by two processes: (a) the hydrolysis of the exchange complex (EC) containing sodium (EC-Na + H₂O ↔ EC-H + Na⁺ + OH⁻) and (b) the reaction of the ion exchange with the substitution of calcium for sodium in the exchange complex (EC-2Na + CaCO₃ ↔ EC-Ca + 2Na⁺ + CO₃²⁻). Calculations performed on the basis of the thermodynamic equations of the physicochemical equilibria according to the LIBRA program indicate that soda is absent in the solonetzic horizons, whose alkalinity is related to the carbonatecalcium equilibria. The high alkalinity of the calcareous subsolonetzic horizons is related to the presence of soda in combination with CaCO₃. The formation of soda in these horizons is due to the reaction of ion exchange described by Gedroits.     

Changes in some properties of solonetzes of the Baraba Lowland 20–25 years after gypsum application

It is shown that a single gypsum application to crusty hydromorphic low- and high-sodium solonetzes of the Baraba Lowland exerts a positive ameliorative effect for a period of 25 years and more. A plow layer with a crumb-granular structure is formed in the ameliorated solonetzes, and positive changes in the particle-size distribution are also observed. The ameliorated crusty solonetzes are transformed into meadow and chernozemic-meadow soils with different degrees of alkalinity and salinity.     

Modern state of soil salinity in solonetzic soil complexes at the Dzhanybek Research Station in the North Caspian Region

Variations in the salinity of virgin soils of solonetzic soil complexes at the Dzhanybek Research Station are characterized on the basis of field materials obtained by the author in 2002–2004. The soil salinity is characterized with respect to the depth of the upper boundary of salt-bearing horizons, the total amount of salts, the content of toxic salts, and the chemical composition of salts. Changes in the soil salinity under dry farming conditions are estimated for the following soil management practices: (1) agroforest amelioration with additional moistening of virgin soils owing to snow retention by the adjacent shelterbelts and forest plantations, (2) intense grazing, (3) soil fallowing after normal tillage to a depth of 20–25 cm, and (4) soil fallowing after deep tillage to a depth of 40–50 cm. It is shown that normal tillage and considerable grazing pressure do not affect the salinity of the studied soils. No definite effect of the shelterbelts on the salt status of the adjacent virgin soils of the solonetzic complex has been revealed. Deep soil tillage strongly affects the salt status of solonetzes: the content of toxic salts in the upper meter considerably decreases. Virgin solonetzes are usually moderately or strongly saline soils, whereas deeply tilled solonetzes are slightly or moderately saline soils.     

Diversity of clay minerals in soils of solonetzic complexes in the southeast of Western Siberia

Data on the mineralogical composition of clay in soils of solonetzic complexes of the Priobskoe Plateau and the Kulunda and Baraba lowlands have been generalized. The parent materials predominating in these regions have loamy and clayey textures and are characterized by the association of clay minerals represented by dioctahedral and trioctahedral mica–hydromica, chlorite, kaolinite, and a number of irregular interstratifications. They differ in the proportions between the major mineral phases and in the qualitative composition of the minerals. Mica–hydromica and chlorites with a small amount of smectitic phase predominate on the Priobskoe Plateau and in the Kulunda Lowland; in the Baraba Lowland, the portion of mica–smectite interstratifications is higher. An eluvial–illuvial distribution of clay fraction in solonetzes is accompanied by the acid–alkaline destruction and lessivage of clay minerals, including the smectitic phase in the superdispersed state. This results in the strong transformation of the mineralogical composition of the upper (suprasolonetzic) horizons and in the enrichment of the solonetzic horizons with the products of mineral destruction; superdispersed smectite; and undestroyed particles of hydromica, kaolinite, and chlorite from the suprasolonetzic horizons. A significant decrease in the content of smectitic phase in the surface solodic horizons of solonetzic complexes has different consequences in the studied regions. In the soils of the Priobskoe Plateau and Kulunda Lowland with a relatively low content (10–30%) of smectitic phase represented by chlorite–smectite interstratifications, this phase virtually disappears from the soils (there are only rare cases of its preservation). In the soils of the Baraba Lowland developed from the parent materials with the high content (30–50%) of smectitic phase represented by mica–smectite interstratifications, the similar decrease (by 10–20%) in the content of smectitic phase does not result in its complete disappearance. However, the smectitic phase acquires the superdispersed state and the capacity for migration.