Specific features of the humus status in soils of Buryatia

The humus content in soils of Buryatia varies significantly in dependence on the local hydrothermic conditions. All the studied soils are characterized by a relatively short humus profile, a sharp drop in the humus content down the soil profile, considerable amounts of the humin fraction and the fraction of humic acids bound with sesquioxides, and a moderate humus enrichment with nitrogen.     

Monitoring of the humus status of soils of the Ingulets irrigation system

The results of long-term studies (1957–2007) of the changes in the morphology of soil profiles and in the reserves and fractional composition of the humus in the soils of the Ingulets irrigation system are discussed. After 50 years of irrigation, the boundaries of the genetic horizons shifted downward by 15–30 cm. The redistribution of the humus took place: its content decreased to a low level in the plow layer of the irrigated and rainfed soils and significantly increased in the layer of 60–100 cm so that the reserves of humus in the layer of 0–100 cm somewhat increased and corresponded to a moderate level. The distribution of humus in the soil profiles was characterized by the gradual lowering down the soil profile. The concentration of nitrogen in the humus of the irrigated southern chernozems was very low. The degree of humification of the soil organic matter was high. The humus was of the humate type in the upper horizons and of the fulvate-humate type in the lower horizons.     

Zonal features of humus formation in Al-Fe-humus podzols of the Kola Peninsula

Natural zonality manifests itself clearly in the territory of the Kola Peninsula: subzones of southern tundra, forest-tundra (sparse birch forest), and northern taiga replace one other from the north, to the Barents Sea coast, and to the south. Sandy and sandy loamy sediments of glacial, marine, and glaciofluvial origin are parent rocks all over the territory. Al-Fe-humus podzols, the profile of which is characterized by clear differentiation of the chemical composition and organic matter content, were formed on these rocks. There is almost no difference in the particle-size and total chemical composition of the podzols, whereas the content and composition of the humus in the soils of different zones differ significantly, and this is especially obvious in the illuvial horizon. As the climatic severity increases, the humus content in the mineral profile and the organic matter enrichment with nitrogen increase.     

Specific features of organic matter in urban soils of Rostov-on-Don

Data on the fractional and group composition of humus in urban soils of Rostov-on-Don are discussed. We have compared the humus profiles of chernozems under tree plantations and those buried under anthropogenic deposits (including sealed chernozems under asphalt). It is shown that the type of humus in these soils remains stable despite a decrease in its total content after the long-term burial under asphalt. Under the impact of the trees, the organic matter of the chernozems acquired some features typical of gray forest soils, i.e., the humate-fulvate type of humus in the humus horizon and the sharp drop in the humus content down the soil profile.     

Spatial distribution of mineral components in microcombinations of agrogrey soils with the second humus horizon in the Vladimir opolie area

Mineralogical composition of silt and clay fractions (<1.1–5 and 5–10 µm) in heavy loamy agrogrey soils (Luvic Retic Phaeozems) considerably changes both in the vertical (along the soil profile) and horizontal (along soil microcatenas) directions. The eluvial–illuvial distribution pattern of the clay fraction in the podzolized agrogrey soils with the second humus horizon is replaced by the homogeneous distribution in the agrogrey soils with residual carbonates. The distribution of silt fractions in the soil profiles is relatively homogeneous. The clay (<1 µm) fraction of the parent material is represented by the poorly ordered micasmectite interstratifications minerals, the proportion between which changes in the soil profiles in dependence on the particular pedogenetic processes. Hydromicas represent the second important component of the clay fraction. They consist of di- and trioctahedral varieties, the proportion between which changes in the soil profiles. Kaolinite and iron–magnesium chlorite are present in smaller amounts. The second humus horizon is characterized by the lowest content of mica-smectite interstratifications minerals with the high content of smectitic layers and by the lowest content of the clay fraction. Silt fractions are composed of quartz, micas, potassium feldspars, and plagioclases.     

Cryometamorphic gleyzems in the taiga of Western Siberia: Chemical and mineralogical properties,ecology, and genesis

Earlier studies showed considerable differences in the properties of automorphic loamy soils developing under middle-taiga vegetation in Western Siberia and on the Russian Plain. It was found that the soils without clear features of textural differentiation are common in Western Siberia. In particular, they are represented by cryometamorphic gleyzems. In this study, we analyze the properties of a cryometamorphic gleyzem in the Vakh area (the Khanty-Mansi Autonomous Okrug). The distribution pattern of clay minerals in the soil profile is analyzed in relation to the specific features of the soil hydrothermic regime. In the upper mineral horizons, the clay fraction is enriched in minerals of the group of soil chlorites and somewhat depleted of labile phyllosilicates. In the cryometamorphic horizon and in the underlying permafrost, the degree of crystallization of the clay minerals somewhat decreases. An even distribution pattern of aluminum oxide in the soil profile is explained by the increased content of Al in the clay fraction from the upper horizons combined with the loss of Al from the coarse fractions (as judged from data on the bulk elemental composition of clay-free samples). These features can be explained by the specificity of the hydrothermic regime of the cryometamorphic gleyzems with late thawing of the soil profile and frequent phase transitions of soil water in the upper humus and middle-profile cryometamorphic horizons.     

Water-soluble phenolic substances in soils under several coniferous and deciduous tree species

The humus layer of soils under Betula pendula, Quercus robur, Fagus sylvatica, Pinus nigra and Picea abies was analyzed for water-soluble phenolic substances. Highest concentrations of total water-soluble phenols were found in soils supporting oak trees. Highest polyphenol concentrations occurred under spruce-fir and beech trees, whereas highest monomeric phenols were found in soils under spruce-fir and pine. The polyphenol content was positively correlated with total carbon content of the soil. The phenolic acid composition of the soils under trees was partly dependent on the tree species. Among the monomeric compounds, ferulic, p-coumaric, vanillic, protocatechuic, syringic and benzoic acid dominated the phenol spectra.Seasonal variations were observed in the concentrations of water-soluble and mild alkaline-soluble phenols in the humus layer under F. sylvatica in two contrasting soil types. The water-soluble phenols in a sandy soil accounted for a larger proportion of the mild-alkaline extractable amounts compared to a loamy soil.     

Changes in the solid and liquid phases of different soils in model experiments with monoliths

In long-term (20-year-long) experiments, the behavior of different soils under natural conditions different from their usual functioning conditions were analyzed. From soils under natural conditions, organic and mineral substances were partly leached or accumulated under the influence of introduced mixed fir, cedar, and birch falloff. During the time of the experiment, the humus composition distinctly changed. The leached chernozem turned out to be the most stable object; the loamy rock was the least stable one. In the latter, humus was notably accumulated. The intensity of the substance flux through the soils already began to change in 3–5 years, but only after 15 years did some quantitative changes take place. At the same time, the trends of the changes depended on the genesis and initial properties of the soils. The composition of the organic substances in the lysimetric water was related to the soil nature, and, during 20 years, it essentially did not change.     

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.     

Mountain-meadow soils of the highlands in the Western Caucasus

The published and author’s data on soil-forming conditions, morphology, substance composition and physicochemical properties, total chemical and mineralogical composition, and micromorphology of mountain-meadow soils of the Western Caucasus Range are analyzed. On the basis of the analytical data obtained, the transformation of minerals and features of chemical element profile patterns developed in the course of soil formation are characterized. The main processes accompanying the transformation of mineral and organic parts of the soil mass and migration of soil-formation products are described. Soil formation is shown to be accompanied by two major elementary soil processes developing with participation of soil biota: humus accumulation and clay formation. Ways to improve the classification of mountain-meadow soils are proposed.     

Temperature field of complex soilscapes (by the example of the Vladimir opolie region)

Problems of the assessment of soil temperature regime at the polypedon level have yet to be solved. An approach suggested by the authors consists of three stages: (1) the characterization and prediction of the soil water regime as a factor influencing the soil temperature regime, (2) the obtaining of thermophysical functions for the particular elements of complex soilscapes, and (3) the calculation and assessment of the temperature regime of complex soilscapes in the form of the functional fields of soil temperature isopleths. This approach has been applied to predict the soil temperature regime of an arable field in the Vladimir opolie region. The complex soilscape of the field consists of medium loamy agrogray soils, agrogray soils with the second humus horizon, and podzolized agrogray soils. At the beginning of the growing season, minimum temperatures are observed in the areas of agrogray soils with the second humus horizon; the difference in soil temperatures at a depth of 20 cm reaches 1°C, and the difference in the sum of active soil temperatures reaches 20°C. Then, this difference changes considerably, so that the agrogray soils with the second humus horizon become warmer than the agrogray soils. In general, the functional field of soil temperatures within the complex soilscape is highly dynamic and diverse, which is specified by the variability in the water-physical and thermophysical properties of particular soils.     

Radiocarbon ages of humic substances in chernozems

Data on radiocarbon ages of different fractions of humus (humic acids, fulvic acids, and humin) in the profiles of chernozems are analyzed. A chronoecological grouping of humus in modern and buried (fossil) soils is suggested. An increase in the radiocarbon age of humic substances down the soil profile has a stepwise character. It is shown that the ¹⁴C content in chernozems decreases down the soil profile more somewhat slower than the ¹²C content. The dependence of a decrease in the humus content of buried soils on the age of burying is traced for a time span of 800 ka.     

Mobility of heavy metals in polluted soils near zinc smelters

The distribution and the availability of Cd, Zn, Cu, and Pb along the entire profile of two highly polluted soils located near Zn smelters have been related to the chemical and mineralogical composition of the soil. Lead and Cu deposits always remain in the surface layers and their availability measured by neutral ammonium acetate extraction was very weak. The behavior of Cd and Zn appears different in sandy acidic podzolic soils and in neutral loamy soils. These metals are associated with the organic matter migration in podzolic soils, while they remain in the upper layers in loamy soils provided that the pH is higher than 6. When the pH drops below 6, the mobility of Cd increases while that of Zn increases only below pH 5. The availability of heavy metals is lower in neutral loamy soils than in sandy acidic soils due to precipitation of carbonates and phosphates. With increasing depth, Cd and Zn are more available if the soil is acid; but, if the soil is neutral and loamy the availability is kept low by adsorption on clays and free oxides. The results of the complex trace metals interactions with the soil components show a higher accumulation capacity for loamy soils than for sandy soils notwithstanding the fact that their CEC is similar.     

Stable and labile components of humus in soddy-podzolic soils

A mathematical model was proposed to characterize the seasonal dynamics of the humus composition in loamy soddy-podzolic soils. The results of determining the composition of the organic matter during two successive seasons revealed the presence of labile and stable components in almost all the groups and fractions of the humic substances. The seasonal changes in the content of the humic substances, the exchangeable Ca, and the pH value at the equilibrium state of the soil were found to be identical during the successive years.     

Changes in the content and composition of humus in the sandy loamy soddy-podzolic soil in a long-term liming experiment

The effect of liming on organic matter in sandy loamy soddy-podzolic soil was studied. The study was performed on samples taken from the 50-year-long experiment established by Prof. Kornilov in 1957. It was shown that liming had almost no effect on the total humus content in the soil. The humus composition was studied using two fractionation methods of the humus substances by the Ponomareva-Plotnikova procedure. The regrouping of the humus fractions occurred due to the changes in the mobility of soil mineral components, which involved a regular increase in the content of the Ca-bound fraction of humic acids (HA-2) at the expense of the HA-1 fraction bound to the mobile forms of R₂O₃ reliable at the lime rates equivalent to the total acidity and higher. The levels of the stabilization of the different HA fractions were considered, as well as the stability of the changes in the humus composition during 50 years.     

Morphology and physical properties of soil material in cryogenic cracks of permafrost-affected meadow-chernozemic soils of the Trans-Baikal Region

Meadow-chernozemic soils (Turbic Chernozems Molliglossic) in the western Trans-Baikal Region are dissected by large cryogenic cracks penetrating to the depth of 100–120 cm and filled with humified material. The depth of humus pockets is 50–80 cm, and their width in the upper part is 50–90 cm. The lower boundary of most of the humus pockets lies at the depth of 60–70 cm. The development of cryogenic cracks proceeded due to their penetration into the frozen ground, which is evidenced by their sharply narrowing lower part. The fraction of physical clay (<0.01 mm) constitutes a considerable part of the material filling the cracks, which explains the significant humus content in this material. The contents of humus and adsorbed bases sharply decrease down through the soil profile in the soil mass between the cracks and remain relatively stable in the material filling the cracks. The soil mass in humus pockets is less compact that that in the background soil mass at the same depth, which is explained by the higher humus content in the pockets. Humified soil material in the pockets is also characterized by a higher porosity and, hence, higher water permeability than the surrounding soil mass.     

Morphology,properties, and regimes of migrational–mycelial agrochernozems with different ground moistening (Belgorod oblast)

Agrochernozems of a catena (local divide, backslope, and footslope positions on a gentle slope of southern aspect) on the fields of Belgorodskoe farm were studied. The soils are developed from lithologically heterogeneous sediments with temporal accumulation of precipitation water above the lithological contact. A close correlation between the morphology and properties of the soils and the character of their water regime in different positions of the catena was found. Agrochernozems of the divide belong to the migrational–mycelial type of forest-steppe chernozems according to their humus profile, water regime, and slightly differentiated distribution of carbonates. Agrochernozems on the backslope with a higher ground moistening have a more contrasting water regime with the topsoil drying in the summer, a sharper decrease in the humus content down the soil profile, and a distinct carbonate-accumulative horizon with a smooth upper boundary, which makes them closer to the type of steppe agrochernozems. The soils of the footslope are characterized by alternation of the percolative and exudative water regimes; these soils are classified as quasigley agrochernozems with a shortened humus horizon and with dispersed and pendant forms of pedogenic carbonates. The character of moistening, morphology, and properties of the studied soils allow us to state that their genesis is controlled by the local ecological conditions with minimal influence of erosional processes on the slope.     

水稻土的腐殖质组成

土壤的有机质状况与成土条件之间有着紧密的联系。借助于腐殖质形成分析法,ТюРин确定了腐殖质形成过程的地带性规律。他指出,不同发生学土类,其腐殖质形成有着明显的不同^[1]。Кононова把土壤腐殖质看作为一个高分子物质体系,她证明成土条件对腐殖质的影响,不仅表现在分祖形成方面,而且也表现在胡敏酸的本性方面^[2]。另一方面,一些工作表明,有机厦状况的不同又将对土壤形成过程和土壤性质产生不同的影响^[3]。因此,研究土壤的腐殖质状况,不仅有助于对土壤性质的了解,而且可为成土过程,从而为土壤分类提供有益的资料。     

Morphology,Radiocarbon Age,and Genesis of Vertisols of the Eisk Peninsula (the Kuban–Azov Lowland)

Data on the morphology and radiocarbon ages of humus of dark vertic quasigley nonsaline clayey soils with alternating bowl-shaped (Pellic Vertisols (Humic, Stagnic)) and diapiric (Haplic Vertisols (Stagnic, Protocalcic)) structures are discussed, and the genetic concept for these soils is suggested. The studied soils develop on loesslike medium clay in the bottom of a large closed depression on the Eisk Peninsula in the lowest western part of the Kuban–Azov Lowland. The lateral and vertical distribution of humus in the studied gilgai catena displays a lateral transition of a relatively short humus profile of the accumulative type with a maximum near the surface and with a sharp increase in ¹⁴C dates of humus in the deeper layers within the diapiric structure to the extremely deep humus profile with a maximum at the depth of 40–80 cm, with similar mean residence time of carbon within this maximum, and with a three times slower increase in ¹⁴C dates of humus down the profile within the bowl-shaped structure. The development of the gilgai soil combination is specified by the joint action of the lateral–upward squeezing of the material of the lower horizons from the nodes with an increased horizontal stress toward the zones a decreased horizontal stress, local erosional loss of soil material from the microhighs and its accumulation in the adjacent microlows, leaching of carbonates from the humus horizons in the microlows, and the vertical and lateral ascending capillary migration of the soil solutions with precipitation of calcium carbonates in the soils of microhighs.     

Humus status of soils of overgrown quarries in Leningrad oblast

The humus status of young different-aged soils developed on tailings of different quarries of Quaternary and pre-Quaternary raw materials in Leningrad oblast was studied. Organic profiles were characterized; the humus accumulation rates, the organic matter reserves, the humus enrichment with nitrogen, the degree of humification of the organic matter, and the contents of separate fractions of humus acid in soils on different tailing rocks were estimated. The composition of humic acids was also studied. It was shown that the lithological features of the tailings determining the chemical processes of the profile differentiation of humic substances and the ecogenetic successions of vegetation also determine the rate and direction of the humus accumulation in the soils during similar periods of biological activity in the southern taiga.