The influence of gleyzation and sulfate reduction in different rocks on the lysimetric water from them: A model experiment

The model experiments showed that, under the influence of gleyzation and sulfate reduction, deep changes occurred both in the solid and liquid phases of the soil-forming rocks (soils). The results of an experiment with three widespread soil-forming rocks—river clayey alluvium, loess-like clayey alluvium, and lacustrine calcareous loamy-clayey alluvium—demonstrated that, under the stagnant-percolative water regime and periodic gleyzation, the liquid phase was drastically acidified (by 2–4 pH units) and the redox potential of the lysimetric water was significantly lowered. A significant increase in the input of iron (by 80 to 100 times compared to the control), calcium (10 times), and silicon (1.5–2.0 times) to the lysimetric waters was observed. The sulfate reduction retarded the removal of iron from the substrates to the lysimetric runoff.     

Lessivage and its relation to the hydrological regime of soils

By the examples of four typical catenas in the East European Plain, the role of lessivage in the development of automorphic and hydromorphic loamy and clayey soils with light-colored acid eluvial horizons and with different degrees of gleyzation has been studied. It is found that characteristic features of lessivage are often observed in the soils without hydrological barriers hampering or preventing the vertical migration of soil water and mass transfer processes. The hydrological barriers may be represented by the shallow horizons of temporarily perched water, or by the ascending capillary fringe of the ground water, or by the water-saturated horizons, in which the volume of free pores does not exceed 2–4%. It is shown that light-colored acid eluvial horizons may be formed in the profiles of loamy and clayey soils without any signs of lessivage. The development of strongly gleyed soils (gleyed soddy-podzolic soils and pseudogley soils (Stagnosols)) is not related to colmatage (silting of their illuvial horizons through lessivage); it is conditioned by the actual hydrological regime of these soils. The role of lessivage, podzolization, and gleyzation in the development of clay-differentiated soils is discussed.     

Forms of acid hydrolysis and gley formation and their role in the development of light-colored acid eluvial (Podzolic) horizons

Nowadays, three processes, namely lessivage, acid hydrolysis, and gleying, are considered as responsible for the development of loamy and clayey podzolic soils. However, as was shown earlier, lessivage is not obligatory for their origin. In view of assessing the reasons for the formation of light-colored acid eluvial horizons, this article deals with the role of acid hydrolysis under aerobic conditions against the background of a percolative water regime and of two forms of gleying in the development of the horizons mentioned above. One form of gleying occurs under permanent anaerobic conditions against the background of a stagnant water regime; the other one is formed under pulsating anaerobic-aerobic conditions against the background of a stagnant-percolative water regime. As a result, three large genetically individual groups of soils are formed: nondifferentiated brown and gley, and differentiated podzolic soils on different parent rocks. The two latter forms of gleying are identical in their effects on the mineral substrates. They cause the iron removal from the soils. Among the three processes considered, the last one (gleying under a stagnant-percolative water regime) is the single reason for the leaching of most of the metals, the formation of light-colored acid eluvial horizons and their clay depletion, and for the differentiation of the soil profile.     

Iron minerals in soils on red-earth deposits in the Cis-Ural region

In soils developed from the red-earth deposits in the Cis-Ural region (Perm oblast), hematite does not ensure the theoretically possible redness due to the concealing effect of rivaling pigments, i.e., humus in the upper horizons and Fe(II) in the gleyed horizons. The soil color depends on the minimal (spring) values of the hydrogen partial pressure index rH_min rather than on the average value of this index rHav. The hematite content decreases in the gleyed and humus horizons (despite the absence of the morphological features of gley in the latter due to the concealing effect of humus). The gley horizons are heterogeneous with respect to the state of iron. Upon the maximum wetting in the gley horizons of the mucky-humus gley soil, hematite is being reduced to Fe(II), which is proved by the low values of rH_min (<19). In a less humified dark humus gley soil, the values of rH_min exceed 19, which points to the inherited gley features in this soil. In the mucky-humus gley soil, an inverse dependence between the magnetic susceptibility χ and E_Hmin is observed upon E_Hmin <320 mV. In this case, the degree of reduction of the highly magnetic iron oxides rises from 0.3 to 1.0 due to a decreasing portion of maghemite γFe₂O₃ and an increasing portion of magnetite Fe₃O₄.     

Diagnostics of gleyzation upon a low content of iron oxides (Using the example of tundra soils in the Kolyma Lowland)

The matrix of iron (hydr)oxides exerts a decisive influence on the character of gleyzation. Upon a high content of iron (hydr)oxides, their reduction radically changes the horizon color from warm to cold hues, which is typical of soils on the Russian Plain. Upon the low content of iron (hydr)oxides, iron reduction takes place in phyllosilicates with minimal changes in the soil color. The cold hue of cryohydromorphic soils in the Kolyma Lowland is controlled by the color of the lithogenic matrix with a low content of iron (hydr)oxides. In this case, the soil color characteristics expressed in the Munsell notation or in the CIE-L*a*b* system are ineffective for diagnostic purposes. The colorimetric methods appear to be more efficient after the soil pretreatment with hydrogen peroxide, as the gleyed horizons turn green, while the nongleyed (and not overmoistened) horizons turn red. Physical methods (Mössbauer spectroscopy and magnetic susceptibility measurements) are more efficient for characterizing the properties of iron compounds in cryohydromorphic soils as compared with the methods of chemical extraction. Mössbauer spectroscopy proved to be highly efficient, as the iron oxidation index Fe³⁺/(Fe²⁺+Fe³⁺) decreases in the gleyed horizons. Chemical reagents (Tamm’s and Mehra-Jackson’s reagents) dissolve Fe-phyllosilicates and are not selective in soils with a low content of iron (hydr)oxides.     

Genesis of light-colored acid eluvial horizons in soil profiles

General ideas concerning the formation of light-colored acid eluvial horizons in soil profiles are considered. In Russia, the current concept is related to the polygenetic origin of these horizons due to processes of acid hydrolysis, lessivage, and gley. Based on the original and literature data summarized by the author, the conclusion was drawn that the acid hydrolysis cannot provide the reduction of Fe (III) to Fe (II) under aerobic conditions or its further transfer to the soil solution. Lessivage, which governs the formation of light-colored acid eluvial horizons, is not an obligatory factor, as its features are often absent in the profile of these soils. Under conditions of a stagnant-percolative water regime, gley may be considered to be the only process responsible for the eluviation of Fe, Mn, and Al and removal of iron hydroxide and iron oxide coatings from mineral grains, resulting in an increase in the relative Si content and the appearance of a whitish color. This factor is the only cause for the formation of light-colored eluvial (podzolic) horizons. Therefore, they are monogenetic in origin.     

Acid-base buffering of soils in transitional and transitional-accumulative positions of undisturbed southern-taiga landscapes

The method of continuous potentiometric titration (CPT) of soil water suspensions was used to evaluate the acid-base buffering of samples from the major genetic horizons of podzolic soils on a slope and soddy gley soils on the adjacent floodplain of a rivulet. In the soils of the slope, the buffering to acid upon titration from the pH of the initial titration point (ITP) to pH 3 in all the horizons was 1.5?C2.0 times lower than that in the podzolic soils of the leveled interfluve, which could be due to the active leaching of exchangeable bases and oxalate-soluble aluminum and iron compounds with the later soil flows. In the soddy gley soils, the buffering to acid in the mineral horizons was 2?C10 times higher than that in the podzolic soils. A direct dependence of the soil buffering to acid on the total content of exchangeable bases and on the content of oxalate-soluble aluminum compounds was found. A direct dependence of the buffering to basic upon titration from the ITP to pH 10 on the contents of the oxalate-soluble aluminum and organic matter was observed in the mineral horizons of all the studied soils. The soil treatment with Tamm??s reagent resulted in the decrease of the buffering to acid in the soddy gley soils of the floodplain, as well as in the decrease of the buffering to basic in the soils on the slopes and in the soddy gley soils. It was also found that the redistribution of the mobile aluminum compounds between the eluvial, transitional, and transitional-accumulative positions in the undisturbed southern taiga landscapes leads to significant spatial differentiation of the acid-base buffering of the mineral soil horizons with a considerable increase in the buffer capacity of the soils within the transitional-accumulative terrain positions.     

A concept of Gleyization and its role in the pedogenesis

Three simple factors ‐ excessive moistening, anaerobic microflora and organic matter, are indispensable and sufficient conditions for gley formation. This process is always characterised by a non‐silicate iron loss from the soil fine earth or soil plasma. Gley formation takes place under conditions of stagnant or stagnant‐percolative water regimes.

In the second case gley formation induces a drastic acidification of the mineral soil part, lessivage, removal of iron, aluminium, calcium, magnesium, bleaching of the soil fine earth, and it appears the features of soil with eluvial, acid, bleached horizons. Therefore soils with such horizons should be regarded as manifestations of gley formation in conditions stagnant ‐percolative water regime on acid, neutral or leached parent material. Under influence of stagnant water regimes Fe of mineral substrat is removed and unconsiderable eluviation of Ca and Mg takes place. pH of parent material does not change or has the trend to increase. In this case does not arise a soil with bleached horizons.     

Oxygen Isotopic and Chemical Characterization of Soils with Surface Gleyzation from Central and Northeastern Japan

Four soils with surface gleyzation (Humi-stagnic Gleysols; provisional) from central and northeastern Japan are characterized by a combination of oxygen isotopic, chemical dissolution (pyrophosphate and acid oxalate) and X-ray diffraction analyses. Oxygen isotopic composition of quartz indicates residuum of volcanic materials and eolian dust from interior China as major parent materials of the clayey surficial horizons.     

Bodenformen und Bodenabtrag in den Hochlagen der axialen Pyrenäen

Soil types and erosion phenomena at high elevations of the axial Pyrenees Two soil toposequences are described for the high altitude valley of Benasque (axial Pyrenees, Northern Spain, elevation 1800–2400 m a.s.1.). Deeply weathered cambisols (mostly dystric and eutric) are developed from quaternary deposits of paleozoic sedimentary and metamorphic rocks. These soils are mostly under grass cover and strongly grazed. The physical and chemical properties of these cambisols and the corresponding erosion phenomena are described. In one toposequence (Ampriú) a specific form of soil erosion called “regressive topsoil denudation” is common and correlated with soils developed from stratified substrates with sandy top soil overlying clayey and silty horizons.     

Spatial variation of peat soil properties in the oil-producing region of northeastern Sakhalin

Morphology and properties of medium-deep oligotrophic peat, oligotrophic peat gley, pyrogenic oligotrophic peat gley, and peat gley soils on subshrub-cotton grass-sphagnum bogs and in swampy larch forests of northeastern Sakhalin have been studied. Variation in the thickness and reserves of litters in the studied bog and forest biogeocenoses has been analyzed. The profile distribution and spatial variability of moisture, density, ash, and pH_KCl in separate groups of peat soils have been described. The content and spatial variability of petroleum hydrocarbons have been considered in relation to the accumulation of natural bitumoids by peat soils and the technogenic pressing in the oil-producing region. Variation of each parameter at different distances (10, 50, and 1000 m) has been estimated using a hierarchical sampling scheme. The spatial conjugation of soil parameters has been studied by factor analysis using the principal components method and Spearman correlation coefficients. Regression equations have been proposed to describe relationships of ash content with soil density and content of petroleum hydrocarbons in peat horizons.     

Buried late holocene paleosols of the nienshants cultural-historical monument in St. Petersburg

Buried Late Holocene paleosols of the Nienshants historical monument at the junction of the Neva and Okhta rivers (St. Petersburg) have been studied. These soils developed from estuary deposits of the Littorina basin with abundant artifacts of the Neolithic and Early Iron ages (7–2 ka BP). The soil cover of the area consists of the mature dark-humus profile-gleyed soils on elevated elements of the mesotopography (3.0–3.5 a.s.l.) and dark-humus gley soils in the local depressions (2.0–2.6 m a.s.l.). The soils are characterized by the low to moderate content of humus of the fulvate-humate type. The beginning of humus formation in the dark-humus gley soil on the slope facing the Neva River is estimated at about 2600 yrs ago; for the darkhumus profile-gleyed soils of the studied paleocatena, at about 2000 and 1780 yrs ago; and for the darkhumus gley soil, at about 1440 years ago. Judging from the spore-pollen spectra, the development of these soils took place in the Subatlantic period under birch and pine-birch forests with the admixture of spruce and alder trees. The gleyed horizons of the buried soil at the depth of 1.6–1.2 m on the Neva-facing slope date back to the Late Subboreal period (2500–2600 yrs ago), when pine-birch-spruce forests were widespread in the area. The new data contribute to our knowledge of the environmental conditions during the Neolithic and Iron ages.     

Iron Compounds and the Color of Soils in the Sakhalin Island

Numerical parameters of soil color were studied according to the CIE-L*a*b color system before and after the Tamm’s and Mehra-Jackson’s treatments; we also determined the total Fe content in the samples from the main genetic horizons of the alluvial gray-humus soil, two profiles of burozems, and two profiles of podzols in the Sakhalin Island. In the analyzed samples, the numerical color parameters L* (lightness), a* (redness) and b* (yellowness) are found to vary within 46–73, 3–11, and 8–28, respectively. A linear relationship is revealed between the numerical values of a* parameters and Fe content in the Mehra-Jackson extracts; the regression equations are derived with the determination coefficients (R²): 0.49 (typical burozem), 0.79 (podzolized burozem), 0.96 (shallow-podzolic mucky podzol), 0.98 (gray-humus gley alluvial soil). For the surface-podzolic mucky podzol contaminated with petroleum hydrocarbons, R² was equal to only 0.03. In the gray humus (AY) and structural-metamorphic (BM) horizons of the studied soils, a* and b* parameters decrease after their treatment with the Tamm’s reagent by 2 points on average. After the Mehra-Jackson treatment, the a* parameter decreased by 6 (AY) and 8 (BM) points; whereas b* parameter, by 10 and 15 points, respectively. In the E horizons of podzols, the Tamm’s treatment increased a* and b* parameters by 1 point; whereas the Mehra-Jackson’s treatment decreased these parameters by only 1 and 3 points, respectively. The redness (a*) decreased maximally in the lower gley horizon of the alluvial gray humus soil, i.e., by 6 (in the Tamm’s extract) and 10 points (in the Mehra-Jackson’s) extract. Yellowness (b*) decreased by 12 and 17 points, respectively. The revealed color specifics in the untreated samples and the color transformation under the impact of reagents in the studied soils and horizons may serve as an additional parameter that characterizes quantitatively the object of investigation in the reference databases.     

Transformation of forest soils in Iowa (United States) under the impact of long-term agricultural development

The evolution of automorphic cultivated soils of the Fayette series (the order of Alfisols)—close analogues of gray forest soils in the European part of Russia—was studied by the method of agrosoil chronosequences in the lower reaches of the Iowa River. It was found that the old-arable soils are characterized by an increase in the thickness of humus horizons and better aggregation; they are subjected to active biogenic turbation by rodents; some alkalization of the soil reaction and an increase in the sum of exchangeable bases also take place. These features are developed against the background of active eluvial-illuvial differentiation and gleyzation of the soil profiles under conditions of a relatively wet climate typical of the ecotone between the zones of prairies and broadleaved forests in the northeast Central Plains of the United States.     

Soils with complex organic profiles on the Vasyugan Plain

Soils with intricate patterns of their humus profiles developing in the neutral-calcium landscapes of the southern taiga of Western Siberia under highly dynamic paleogeographic, climatic, and weather conditions are characterized. The specific features of these soils comprise the diverse modern humus horizons along with the relic ones of different preservation rates, shallow leaching of carbonates, and a weak development of the middle-profile soil horizons. Specifying these organo-accumulative soils is substantiated by their high humus content against the geochemical background of the clayey calcareous parent rocks. The conjugated series of soils reflect different stages of the soil evolution (the humus profile degradation, the development of eluvial process, and the increase of contrasts in the acid-base conditions) and the hydromorphic transformation accompanied by the formation of organic horizons making the humus profile more complicated. In accordance with the diagnostic horizons, the position of the soils studied was determined in the Classification and Diagnostics of Soils of Russia. The relic enrichment of the humus horizon is proposed to be used as a specific feature of these soils.     

Particle-size distribution patterns in Vertisols and vertic soils of Russia

Five variants of the distribution of clay (<0.001 mm) and physical clay (<0.01 mm) fractions along the vertical profiles of Vertisols (slitozems) and vertic soils (slitic subtypes of different soil types) from the European part of Russia are distinguished: (1) accumulative, (2) even, (3) regressive, (4) with a maximum in the middle-profile horizon and with their approximately equal contents in the upper and the lower horizons, and (5) eluvial–illuvial. These distribution patterns are related to the lithological specificity of sedimentation and formation of parent materials composed of swelling clays of different geneses and ages. Solonetzic, eluvial- gley, and solodic processes contribute to the development of the eluvial–illuvial and, partly, regressive variants of clay distribution. All the five variants with a predominance of the even distribution pattern can be found in Vertisols. Most of Vertisols in the European part of Russia have a medium clayey or a heavy clayey texture in the entire profile. The regressive distribution pattern is typical of the group of vertic soils. In the upper horizons of Vertisols, where slickensides do not form, the texture is usually heavier than that in the analogous horizons of vertic soils. The middle-profile and lower horizons with slickensides have similar statistical distributions of particle-size fractions in Vertisols proper and in vertic soils. However, in Vertisols, a tendency for a more frequent occurrence of the soils with a higher content of the clay fraction and with a higher portion of this fraction in the physical clay fraction is observed (as compared with the vertic soils).     

Nutrient deficiency and physiological disease of lowland rice in Ceylon

In Ceylon, rice crop is grown chiefly on alluvial as well as low-humic gley soils which are distributed throughout the island. Parent materials of these soils are derived mainly from the weathered products of Khondalite and Charnackite groups of rocks among which acidic schists and gneisses dominate (1). The lateritic weathering of rocks, the most typical lOil formation under tropical climates, results in a general supply of soil materials rich in iron and alumina but lacking in nutrient bases and silica. This is one of the possible reasons for the low fertility of tropical rice soils compared to those of temperate zones.     

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.     

Zu Eigenschaften,Horizontaufbau und Gliederung der „Haftnässepseudogleye”︁

Properties, horizons and classification of the “Haftnässepseudogleye” (Stagnosols periodically waterlogged with capillary water) The term “Haftnässe” (soil wetness due to capillary moisture) can be used in describing soils with Sg-horizons in which long-term waterlogging and anaerobic conditions occur in the absence of gravitational water. “Haftnässe” is caused by water held in pores with an equivalent diameter of 0.2–50 μm by soil-water tension (pF) between 1.8 and 4.2, when the air capacity of the horizons is very low. “Haftnässe” moves primarily by capillary forces and is available to plants (available water). In some soils, the horizon below the Sg-horizon contains large pores, is well aerated and tends to impede the movement of capillary water. This type of horizon is often wetter than the overlying and underlying horizons, due to the presence of capillary water in the immediately overlying Sg-horizon. The symbol “So” is proposed for such horizons. In these soils, in the Sg-horizon reduced iron compounds are oxidized and precipitated, forming rusty mottles. The sequence of horizons developed in the “Haft(nässepseudo)-gleye” (Stagnosols periodically waterlogged with capillary water) typically affects the continuity of the pathways along which capillary water normally moves. The “Haft(nässepseudo)gleye” are divided into two subtypes on the basis of the sequence of horizons in the soil profile:

• Typical “Haft(nässepseudo)gley” (Shn) exhibits a sequence Ah/Sg/(II)So and shows transitions to Luvisol and Glossisol,
• Thick “Haft(nässepseudo)gley” (Shm) exhibits a sequence Ah/Sg and shows transitions to “Stau(wasserpseudo)gley” (Gleysol periodically waterlogged due to perched water), Gleysol, Fluvisol and tidal marsh soil.

     

Genesis and classification position of automorphic soils developed from mantle loams in the northern taiga of European Russia

Automorphic loamy soils of the northern taiga and forest-tundra zones in the northeastern part of European Russia are characterized. These soils are diagnosed by the presence of a paragenetic system of the podzolic (often, with gley features) and iron-illuvial horizons combined with a specific cryometamorphic CRM horizon. The podzolic horizon is considerably impoverished in the total and oxalate-extractable iron and slightly impoverished in aluminum and clay in comparison with the iron-illuvial horizon. A distinctive feature of the cryometamorphic horizon is its fine angular blocky, ooidal, or granulated structure in the dry state and curdled cryogenic structure in the wet state. The soil profile is relatively weakly differentiated with respect to the contents of clay and sesquioxides. The genesis of these soils is related to a combination of the gley-Al-Fe-humus mobilization, migration, and illuvial accumulation of substances and the cryogenic structuring. According to the new Classification and Diagnostic System of Russian Soils, these soils fit the criteria of iron-illuvial svetlozems in the order of cryometamorphic soils. In the studied area, these soils are found together with texture-differentiated gley-podzolic soils having the Bt horizon and belonging to the order of texture-differentiated soils.