The soil cover on a gentle watershed slope under conditions of the recent seasonal soil overwetting in the Kamennaya Steppe area

The soil cover pattern on a gentle watershed slope at the Kamennaya Steppe Experimental Farm consists of the areas of typical chernozems, zooturbated chernozems, and leached chernozems evolving into chernozemic-meadow soils; they are oriented along the slope. This soil combination is complicated by the presence of slightly eroded and slightly saline soils. The seasonal overwetting and inundation of the soils are favored by the discharge of the groundwater above the local aquiclude represented by the layer of dark brown calcareous clay at the depth of 1.0–2.2 m from the soil surface and by the concentration of snowmelt runoff in the concave parts of the slope. Seasonal overwetting of the soils leads to the appearance of olive tints and small iron concretions (quasigley features) in the lower horizons; in some cases, proper gley features (bluish coatings) appear in the chernozems. The veinlets of powdery gypsum are formed in the middle-profile horizons of some soils. Salt efflorescence on the surface in some places is also the result of the seasonal overwetting of the soils followed by their intense drying upon the hot and droughty weather conditions.     

Changes in acidity parameters of chernozems in the Kamennaya Steppe

The analysis of long-term data on the acidity parameters of chernozems in the Kamennaya Steppe indicated a tendency for some alkalization of the soils.     

Spatial distribution of exchangeable bases in chernozem of Kamennaya Steppe

The high degree of base saturation and high cation exchange capacity with an appreciable dominance of calcium are related to the high carbonate content in parent rocks, high content of humus in chernozems, and abundant fine material in their profiles. These are characteristic features of prevalent soils in the Kamennaya Steppe. Almost all soils of monitoring and experimental plots have an appreciable spatial variation in exchangeable bases. The obtained data indicate that the content of adsorbed calcium in the exchangeable complex of the soil decreases with increasing shares of adsorbed magnesium and partially sodium.     

Carbonates in some soils of the Kamennaya Steppe

A comparative analysis of the conditions of formation and distribution of carbonates in the profiles of ordinary chernozems and meadow-chernozemic soils within the Kamennaya Steppe (Voronezh oblast) is given. On this basis, the approximate duration of the meadow stage of soil development is estimated. It is shown that the upper boundary of soil carbonates changes under the impact of forest shelterbelts.     

Biological activity in the profiles of chernozems as dependent on the character of their agricultural use and microtopography

The biological activity of soil samples taken from genetic horizons of plowed and virgin chernozems in the Kamennaya Steppe Reserve was determined as the amount evolved from the soil upon its incubation in laboratory conditions. In the top humus horizons, the biological activity of virgin chernozem was two to three times higher as compared with that in the plowed chernozem. The intensity of biological processes and the microbial biomass in the soil profile was mainly controlled by the quantity and quality of soil organic matter. Long-term agricultural use exerted a weaker effect on the biological properties of chernozems developed on microelevations (blocks) of the paleocryogenic microtopography in comparison with chernozems developed in the microdepressions between the blocks. The factor analysis showed that soil characteristics related to the biological processes comprise more than 50% of the total variance of factor loads and are distinctly differentiated in the soil profile.     

Simulation of water permeability processes in chernozems of the Kamennaya Steppe

The physical and hydrophysical properties of ordinary chernozems from the Kamennaya Steppe were studied for the experimental support of a soil water infiltration model. Increased fissuring and density of the plow horizon were noted because of the dry weather conditions, which caused high infiltration values. The soil water retention curve parameters were calculated from the experimentally determined particle-size distribution, the bulk density of the soil, the solid phase density, the organic matter content, and the physicomechanical and soil-hydrological constants using the known pedotransfer functions and the Voronin secant method. A model experiment with different input parameters was performed. It was shown that the best experimental support of the model included parameters calculated by the Voronin method with the following approximation by the van Genuchten function.     

Soil cover in the southern forest-steppe of the Central Russian Upland against the background of centennial climate fluctuations

Special approaches and algorithms for studying the response of zonal soils and the soil cover of the forest-steppe zone to climate fluctuations were developed on the basis of data of repeated soil surveys. They made it possible to analyze the particular transformations of the soil cover as indicators of short-term climate fluctuations in the southern forest-steppe of the Central Russian Upland. Vector soil maps and related databases on soil polygons were developed using GIS technologies. Changes in the climatic conditions between two rounds of large-scale soil surveys in 1971 and 1991 reflecting the so-called Brückner cycles were identified. A characteristic feature of climate change during that period was the rise in the mean annual air temperature by 0.2°C and an increase in the mean annual precipitation by 83 mm. In response to this change, the area of leached chernozems (Luvic Chernozems) on the interfluves somewhat increased, whereas the area of typical chernozems (Haplic Chernozems) decreased.     

Structural state of migrational-mycelial (typical) agrochernozems of the Kamennaya Steppe on plowed fields of different ages

Changes in the structural state of migrational-mycelial (typical) chernozems (Haplic Chernozems (Clayic, Aric, Pachic)) as dependent on the duration of their cultivation (from 20 to 120 years) are considered. Field studies were performed in 2013 on the fields of the Dokuchaev Research Institute of Agriculture in the Central Chernozemic Region of Russia (the Kamennaya Steppe area) used for growing cereals and row crops in rotation. The study showed that the most intensive degradation of the structure of chernozems takes place during the first two decades of their agricultural use. The maximum transformation of the soil structure is observed in the upper 10 cm, as this layer is subjected to the most frequent and intense mechanical impacts. The rate of structural degradation decreases with time until the equilibrium between disaggregation and aggregation processes is reached. The time required for this largely depends on the applied crop rotation systems and agrotechnologies. In this context, flexible assessment scales for the structural state of agrochernozems under conditions of different farming systems should be developed in order to perform monitoring of the physical properties of cultivated chernozems for their long-term efficient and ecologically sustainable use. Despite general disintegration and destruction of granular aggregates, the structural state of agrochernozems in the Kamennaya Steppe area remains sufficiently good even on the old-cultivated (120 yrs.) fields.     

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.     

An approach for a retrospective assessment of soil changes

An approach for experimental solution of the problem of retrospective monitoring of changes in soil properties via comparative analysis of the results of soil studies performed in approximately the same place at different times is suggested. In essence, it is aimed at the step-by-step reduction of data uncertainty. First, the inaccuracy in georeferencing of an earlier studied soil pit is determined. Then, a key plot is thoroughly studied in order to determine the soil cover pattern in the area of the earlier studied soil pit. After this, the sampling pattern for the new study is chosen with due account for random and regular (predetermined) spatial variability in soil properties. We discuss the example of retrospective estimation of changes in the bulk density characteristics of a chernozem subjected to zoogenic turbation by earth burrowers in the Kamennaya Steppe area. After about 50 years, two parts of the soil profile have been subjected to compaction: the middle part of the plow horizon (10–20 cm), which has acquired a coarse blocky (cloddy) structure, and the soil layer disturbed by earth burrowers at a depth of 30–45 cm. In other parts of the modern soil profile, the bulk density characteristics remain in the same range as those determined 50 years ago.     

Trends of climatic changes in the Kamennaya Steppe

The main trends of local climatic changes in the Kamennaya Steppe area are described on the basis of a great pool of data. The global climatic changes have resulted in the increase of the mean annual temperature and annual precipitation, especially during the last 15–20 years     

Clay minerals in a denudation-accumulative soil catena

Chernozems and agrochernozems of the Kamennaya Steppe agroforest landscape have a silty clay or clay texture and similar associations of clay minerals. The plow horizons of the agrochernozems on a slope of 2°–3° to the Talovaya Balka have an increased content of the smectite phase (50–70%) compared to the upper horizons of the chernozems on flat watersheds (30–50%) due to the lithological discontinuity of the soil-forming material and the possible total removal of material on the slope by denudation. On slightly eroded areas, the clay minerals display a more intense disturbance of their crystal lattice structures by pedogenetic processes, which increase the degree of disorder in their layers and the accumulation of fine quartz in the clay fraction. In the areas with more significant erosion of the humus horizon, the clay minerals are characterized by their perfect structure and clean reflections, which are indicative of the outcropping of less weathered material from the middle part of the chernozem profile less transformed by pedogenesis.     

Trends of the natural evolution of chernozems on the East European Plain

A generalized chronosequence of changes in the morphometric parameters of chernozems in the past 5100 years is analyzed. It is shown that the development of chernozems in the center of the East European Plain is characterized by both long-term (interglacial, encompassing the entire Holocene) and short-term (within separate climatic periods of the Holocene) trends. The long-term trend of the evolution of ordinary chernozems developed from the loess-like calcareous loam consists of a continuous increase in the thickness of the soil humus profile and an oscillating increase in the depth of the carbonate accumulations. The Late-Holocene short-term trends of the natural evolution of chernozems are characterized by the high spatial heterogeneity related to the patterns of climatic fluctuations and to the lithological composition of parent materials. In that period, the thickness of genetic horizons in the forest-steppe chernozems was increasing faster than that in the steppe chernozems.     

Evolution of forest pedogenesis in the south of the forest-steppe of the Central Russian Upland in the Late Holocene

The Late Holocene stage of forest pedogenesis has been studied on the interfluves along river valleys in the forest-steppe zone of the Central Russian Upland. The development of gray forest soils from the former chernozems as a result of the Late Holocene advance of forest vegetation over steppes is discussed. It is argued that the climatic conditions of the Subatlantic period were unstable, so that multiple alternation of forest and steppe vegetation communities took place. This specified a complex character of soil evolution upon contrasting substitution of forest pedogenesis for steppe pedogenesis. On the interfluves near the natural drainage network (balkas, ravines, and steep slopes of river valleys), the climate-driven dynamics of forest and steppe vegetation with corresponding changes in the character of pedogenesis could take place during the entire Holocene, which is reflected in a lower thickness of humus profiles and deeper leaching of carbonates from chernozems of the Early Iron Age in comparison with their analogues formed under steppe cenoses in central parts of the interfluves. Two variants of the evolution of gray forest soils can be suggested: the pulsating evolution typical of balkas and interfluves near river valleys and the continuous progressive evolution typical of automorphic (plakor) positions in central parts of the interfluves.     

The development of detailed soil maps on the basis of interpolation of data on soil properties

A methodology for creating detailed soil maps on the basis of a dense grid of soil testing points and the numerical interpolation of experimental data on the soil properties is discussed. The study of the soil cover patterns combines regular sampling grids with equal spacing and additional sampling points chosen with due account for the soil cover specificity in particular areas. Soil diagnostics are performed at each of the points, and the diagnostic features of the soils are recorded in the field. In a laboratory, these data are arranged into a database, and a legend to the soil map is created. The necessary and sufficient set of the quantitative soil characteristics is selected, and quantitative criteria of the boundaries between the separate soil polygons are determined on the basis of numerical interpolation. Algorithms to delineate soil polygons on the basis of the selected indices are developed. Separate thematic map layers are produced for each of the selected soil characteristics. An integral soil map for the investigated area is obtained via the superposition of these layers. The thickness and/or the depths of the upper/lower boundaries of the soil layer with definite diagnostic characteristics making it possible to distinguish the given soil from its neighbors are used as the criteria for delineating the boundaries between soil polygons. Special criteria based on the proportions between the thicknesses or depths of several layers can also be applied for this purpose. The creation of a detailed soil map of a plot on the Kamennaya Steppe is discussed as an example of the practical application of this methodology.     

Multiple assessment of the soil cover in the area of natural monuments Tra-Tau and Yurak-Tau monadnocks under conditions of technogenic loads

The soil cover of Tra-Tau and Yurak-Tau shikhans (monadnocks) has been examined. Leached and typical medium-deep chernozems are developed on colluvial fans on the footslopes and on the lower parts of slopes, whereas typical calcareous thin slightly and moderately gravelly chernozems are developed on the upper and medium parts of slopes. The leached and typical chernozems of the footslopes correspond to zonal soils of the adjacent plain areas, though they have some specific features related to the local topographic conditions. These soils are somewhat thinner than plain chernozems and are characterized by the perfect granular water-stable structure, the high content of humus of the humate type, the high content of exchangeable cations, strong acid-base buffering, and high enzymatic activity. These features predetermine their high tolerance towards technogenic impacts. The concentrations of highly hazardous substances of the first toxicity class (mercury, arsenic, lead, and cadmium) and of moderately hazardous substances of the second toxicity class (copper, zinc, and nickel), as well as the concentrations of low-hazardous elements (manganese and iron) in these soils do not exceed provisional maximum permissible concentrations of these substances in soils irrespectively of the slope aspect. No changes in the physicochemical and biological properties of the soils under the impact of technogenic loads from Sterlitamak industrial center have been identified.     

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.     

Theoretical basis and practical significance of investigations into soil cover patterns

Principles and methods of studying the soil cover pattern for the inventory, assessment, and rational use of the natural resource potential are outlined. It is suggested that the soil cover patterns should be studied for typified natural systems (territorial units). The latter are different from one another in the composition and pattern of the soil combinations. The typology and hierarchical grouping of soil combinations are developed, and their nomenclature is suggested. The methodology for assessing the soil cover heterogeneity on the basis of a monofactor scale of the degree of the soil contrasts and a modified evaluation of the soil cover compartmentalization with the application of an automated cartographic analysis is described. This procedure has made it possible to gain an integral holistic perception of the geosystems in Belarus. The application of a corresponding database developed in the ArcInfo format for creating maps with information on the morphometric, geomorphic, hypsometric, lithological, and other characteristics of geosystems is illustrated. Special surveys of the soil cover patterns in Belarus were performed on an area of 10000000 ha. Their results are taken into account upon planning the rational nature management.     

Radioecological aspects of recent soil pollution in small catchments of Kursk oblast

A small catchment with an area of 1.98 km² was chosen for detailed studies. The soils of the catchment area are dominated by leached and weakly leached chernozems on loess deposits. The ¹³⁷Cs activity in the soils on a relatively flat area was about 26.7 ± 1.2 Bq/kg. In 20 years after the Chernobyl accident, a contrasting pattern of the ¹³⁷Cs pollution density characterized the small catchment Gracheva Loshchina.     

Snowmelt-induced soil erosion on gentle slopes in the southern Cis-Ural region

It has been revealed that, in the years when the freezing depth of leached chernozems on slopes in the southern Cis-Ural region is in the range of 30–38 cm, no surface runoff is observed in the spring regardless of the snow cover, soil wetting, or vegetation; the critical freezing depth under forest is half that on the open surfaces. When the freezing depth is deeper, the critical volume of the spring runoff is mainly determined by the meteorological conditions, the water permeability of the soil, and its protection by plants.