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Gunina A.,University of Gottingen | Gunina A.,Dokuchaev Soil Science Institute | Kuzyakov Y.,University of Gottingen
Soil Biology and Biochemistry | Year: 2015

Sugars are the most abundant organic compounds in the biosphere because they are monomers of all polysaccharides. We summarize the results of the last 40 years on the sources, content, composition and fate of sugars in soil and discuss their main functions. We especially focus on sugar uptake, utilization and recycling by microorganisms as this is by far the dominating process of sugar transformation in soil compared to sorption, leaching or plant uptake. Moreover, sugars are the most important carbon (C) and energy source for soil microorganisms.Two databases have been created. The 1st database focused on the contents of cellulose, non-cellulose, hot-water and cold-water extractable sugars in soils (348 data, 32 studies). This enabled determining the primary (plant-derived) and secondary (microbially and soil organic matter (SOM) derived) sources of carbohydrates in soil based on the galactose + mannose/arabinose + xylose (GM/AX) ratio. The 2nd database focused on the fate of sugar C in soils (734 data pairs, 32 studies using 13C or 14C labeled sugars). 13C and 14C dynamics enabled calculating the: 1) initial rate of sugar mineralization, 2) mean residence time (MRT) of C of the applied sugars, and 3) MRT of sugar C incorporated into 3a) microbial biomass and 3b) SOM.The content of hexoses was 3-4 times higher than pentoses, because hexoses originate from plants and microorganisms. The GM/AX ratio of non-cellulose sugars revealed a lower contribution of hexoses in cropland and grassland (ratio 0.7-1) compare to forest (ratio 1.5) soils.13C and 14C studies showed very high initial rate of glucose mineralization (1.1% min-1) and much higher rate of sugars uptake by microorganisms from the soil solution. Considering this rate along with the glucose input from plants and its content in soil solution, we estimate that only about 20% of all sugars in soil originate from the primary source - decomposition of plant litter and rhizodeposits. The remaining 80% originates from the secondary source - microorganisms and their residues. The estimated MRT of sugar C in microbial biomass was about 230 days, showing intense and efficient internal recycling within microorganisms. The assessed MRT of sugar C in SOM was about 360 days, reflecting the considerable accumulation of sugar C in microbial residues and its comparatively slow external recycling.The very rapid uptake of sugars by microorganisms and intensive recycling clearly demonstrate the importance of sugars for microbes in soil. We speculate that the most important functions of sugars in soil are to maintain and stimulate microbial activities in the rhizosphere and detritusphere leading to mobilization of nutrients by accelerated SOM decomposition - priming effects. We conclude that the actual contribution of sugar C (not only whole sugar molecules, which are usually determined) to SOM is much higher than the 10 ± 5% commonly measured based on their content. © 2015 Elsevier Ltd.

Molchanov E.N.,Dokuchaev Soil Science Institute
Eurasian Soil Science | Year: 2010

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. © 2010 Pleiades Publishing, Ltd.

Gerasimova M.I.,Moscow State University | Khitrov N.B.,Dokuchaev Soil Science Institute
Eurasian Soil Science | Year: 2012

Three soil classification systems-the World Reference Base for Soil Resources (WRB), Soil Taxonomy, and the recent Russian system-were used for the identification of 17 soil profiles in southwestern Poland; all the systems put emphasis on the soil properties as diagnostic criteria. Different soils developed on glaciofluvial plains, loessic uplands, and in the Sudetes Mountains were classified. The best correlation between the classification decisions in the different systems was obtained for the most widespread soils owing to the similarity of the diagnostic criteria, which were essentially close although not coinciding. The most prominent divergence between the systems in both the names and the taxonomic categories of the soils was found for the polygenetic soils and for the soils developing from the lithologically discontinuous parent materials. It was also found that the diagnostic elements differ in terms of their taxonomic importance among the classification systems. © 2012 Pleiades Publishing, Ltd.

Rozhkov V.A.,Dokuchaev Soil Science Institute
Eurasian Soil Science | Year: 2014

The dualism of notions is a common form of our perception of the world. Thus, the notion of a classification system actually includes two complementary parts: taxonomy and meronymy. Taxonomy describes the structure of taxonomic units (taxa) and their relationships, whereas meronymy deals with the structure of the archetypes and meronyms (parts of the whole) composing them and linked by associative relations. An archetype can be defined as a generalized image consisting of meronyms that can be definitely described by a set of characteristics. Each archetype in meronymy has a corresponding taxon in taxonomy. The notions of the object of classification and the particular objects (things) representing it are explained. The notions of soil objects are somewhat different and depend on the goals and kinds of classification (conceptual, physical, or imaginable). Substantive (natural) classifications that encompass the entire set of conceivable objects (entirety) can be referred to as intensional classifications. They should be distinguished from extensional classifications dealing with a particular group of objects (data) and aimed at their arrangement in a convenient way. Extensional soil classification systems are those systems that actually arrange the lists of known soils into some order according to the rules formulated by their authors. © 2014 Pleiades Publishing, Ltd.

Data on clayey swelling soils with gilgai microtopography are systematized. Classifications of gilgai microtopography representing regularly alternating microhighs and microlows are discussed, and its geometric parameters under different landscape conditions are considered. Gilgai microtopography is developed within flat or slightly inclined elements of the mesorelief composed of swelling clays of different geneses. These materials are characterized by the high swelling–shrinking capacity upon wetting–drying cycles owing to the predominance of clay minerals of smectitic group. These processes are especially pronounced under conditions of the impeded surface drainage and contrasting of the wet seasons with strong soil moistening by atmospheric precipitation or surface water and the seasons with deep soil drying under the impact of physical evaporation and transpiration. The areas with gilgai microtopography have complex soil cover patterns composed of Vertisols and vertic soils. Their formation is related to lateral movements of solid material in the soil profiles and along the curved soil surface. The morphological types of soil complexes in such area are systematized. © 2016, Pleiades Publishing, Ltd.

Khitrov N.B.,Dokuchaev Soil Science Institute
Eurasian Soil Science | Year: 2016

Data on the morphology and spatial distribution of slickensides and cracks, particle-size distribution, the organic carbon content, the content and forms of carbonate concentrations, and physical and physicochemical properties of Vertisols with the gilgai microtopography are systematized. Relatively scarce information on the functioning regimes of gilgai soil complexes (their temperature and moisture conditions, redox potential, vertical and horizontal deformations, and soil density changes) is discussed. Common properties of gilgai soils are the clayey texture of their profiles and the high portion of smectitic minerals specifying the high shrink–swell capacity of the soil material. The most important specificity of soils with the gilgai microtopography is a significant horizontal differentiation of the soil profiles with alternation of bowl-shaped morphostructures with a thick dark layer without carbonates in microlows and diapiric morphostructures composed of the rising material of the lower layers with diverse carbonate concentrations on microhighs. Data on the spatial distribution of soil properties within the gilgai microcatenas can be applied in the studies of the genesis and evolution stages of the gilgai soil complexes. © 2016, Pleiades Publishing, Ltd.

Khitrov N.B.,Dokuchaev Soil Science Institute
Eurasian Soil Science | Year: 2016

Different hypotheses about the genesis of gilgai microtopography and corresponding soil complexes with clayey swelling soils are considered in this review. Their diversity is stipulated by specificities of the objects themselves and by the history of studies of the composition, properties, regimes, and landscape conditions of the areas with Vertisols in different countries. Most of the hypotheses about the genesis of Vertisols with the gilgai microtopography suggest that strong swelling–shrinking processes take place in these soils in the course of moistening–drying cycles; the origin of shear stress in the soils, its spatial patterns, and the particular ways of translocation of the soil material are discussed. At the early stage of Vertisol studies, a hypothesis about the leading role of the process of “self-swallowing” of the soils as a result of filling of open cracks with the material from the upper soil horizons was popular. However, numerous facts suggest that the intensity of this process is relatively low, so that it cannot play the major role in the gilgai formation and cyclic changes in the thickness and properties of the soil horizons in Vertisols. Another important mechanism is the uneven moistening and drying of the whole soil volume resulting in the irregular distribution of inner tensions in the soil with the development of shear stress and plastic deformation of the soil mass. The hypotheses suggested in the recent decades are based on the models of soil mechanics. A number of hypotheses consider possible alternation and duration of evolutionary stages of the development of Vertisols with the gilgai microtopography. © 2016, Pleiades Publishing, Ltd.

Pankova E.I.,Dokuchaev Soil Science Institute
Eurasian Soil Science | Year: 2015

Data on salt-affected soils of Russia are analyzed. Three major problems of current research are outlined: (1) adequate diagnosis of soil salinization, (2) mapping and assessment of the areas of salt-affected soils, and (3) monitoring of the state of soil salinization. On the basis of recent publications, priority tasks and challenges for further research in this field are discussed. First, the notion of salt-affected soils should be specified with due respect for the diagnostic criteria of soil salinization. Second, in the assessment of these soils, not only the degree of salinization but also the chemistry of salts and the depth of the upper salt-bearing horizon should be taken into account. Third, to calculate the areas of salt-affected soils and to perform their monitoring, satellite images meeting specified requirements should be used. These requirements depend on the land use and cultivated crops. Modern technologies of the interpretation of satellite images should be applied for these purposes. Recent studies devoted to the monitoring of the salt status of irrigated and virgin soils of arid regions are discussed. © 2015, Pleiades Publishing, Ltd.

Korolyuk T.V.,Dokuchaev Soil Science Institute
Eurasian Soil Science | Year: 2015

Relationships between the salinization of agrochernozems, agrochestnut soils, and textural carbonate agrozems on the plains and factors of soil formation in the Central and Western Ciscaucasia are considered. Among the studied factors are the following: parent rock, climate, relief, depth of groundwater table, and human activity (irrigation in particular, which is considered as one of the strongest anthropogenic impacts). In the territory of the objects studied, saline parent rocks predominate. They determine the potential (in autonomic landscapes) or actual (in subordinate landscapes) salinity of the main soils and their instability under intense use. The influence of climatic conditions can be registered only in the soil salinity over vast loess plains, where the agrochernozems are replaced by the agrochestnut soils. The influence of the meso- and microrelief on soil salinization is manifested in the regular transformation of soil cover structures in catenas. In the northeast of the loess plains, this phenomenon was expressed in the appearance of agrosolonetzic complexes on slopes and, then, in their predominance in subordinate positions. The response of the soil cover pattern to changes in the salt regime of the soils in catenas and its reconstruction under irrigation may serve as an indicator of trends in the dynamics of the soil cover related to human activities and climate fluctuations. © 2015, Pleiades Publishing, Ltd.

Mikhailov I.S.,Dokuchaev Soil Science Institute
Eurasian Soil Science | Year: 2016

A new soil map of the Russian Arctic on a scale of 1 : 1 M shows the soil cover in the north of Eurasia and on the islands of the Arctic Ocean to the north of 68° N. This map has been developed in a geoinformation system in the vector format with the wide use of remote sensing data. The delineated soil polygons show dominant and accompanying soils and the structure of soil cover patterns with indication of soil associations and soil complexes, the character of parent materials, and the topographic conditions. The map of the soil-geographic zoning of the Russian Arctic developed on the basis of the soil map differs from its earlier analogues in a greater degree of detail. The soil map of the Russian Arctic on a scale of 1 : 1 M displays the most detailed information on the soil cover patterns and can be used for solving various problems related to the exploration and development of this territory. Soil names from the new classification system of Russian soils [10] have been introduced into the legend of the map. New soil information and the use of remote sensing data have made it possible to enlarge the number of soil polygons shown on the map and to correct their boundaries in comparison with previous soil maps of the Russian Arctic. © 2016, Pleiades Publishing, Ltd.

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