№ 3 (2023)

In the well-known conceptual model SCORPAN, given soil property is considered as dependent on the following environmental factors: soil, climate, organisms, topography, time and space. Predictive mapping of soils in digital soil mapping is based on similar ideas, but environmental factors may include not only factors of soils formation, but also, for example, remote sensing data, and have found a wide distribution not only in soil science, but also in ecology, agriculture and geomorphology. This paper provides a review of environmental factors that are used in predictive mapping with a special attention to situations when wide sets of environmental factors may be used and a part of them is not quantitative, such as vegetation types. Most developed are systems of quantitative variables for topography and climate description, so that a special attention is paid to them. Land surface description is performed using both local and non-local variables that need integration. In climate description variables are essential that estimate dry or wet terrain features, such as moisture ratio or water deficit. They need evaluation of potential evapotranspiration that is not measured by meteo-stations, but may be calculated. Possibilities of accounting these and other environmental factors including non-quantitative ones in quantitative statistical models of predictive mapping are described together with principles of their construction, verification, comparison, choice of appropriate models. Examples of soil predictive mapping applications are given for various scales, their specifics for different scales is outlined. Some aspects of remote sensing data usage are discussed.

For the territory of the Smolensk Lakeland with a complex and understudied soil cover and considerable influence of the anthropogenic factor, it is relevant to create soil maps using the comparative geographic method. For an area of 8.8 km² in the southwestern part of the Smolenskoye Lakeland National Park, soil maps (scale 1 : 25 000) were created using the methods of traditional and digital soil mapping (DSM). And a comparison of the results obtained was made. The territory under consideration is dominated by gray-humus soils (Umbric Cambisol (Loamic) and Arenosols (Ochric)) on two maps. These soils are associated with past agricultural use and regeneration of old arable soils. Smaller areas are occupied by alpha-humus and texture-differentiated soils (Podzols (Arenic) and Retisols (Loamic), respectively). In addition, isolated areas of psammozems (Arenosols) have been found and identified on the map using traditional approach. The overall accuracy of the map compiled by the DSM methods was 55%. The leading factors were identified: the position in the relief, the nature of the substrate and vegetation. The distribution of texturally differentiated soils associated with loamic parent materials and humus-peat soils formed in local depressions and on the floodplain of Lake Baklanovskoye is predicted with an accuracy of 87% and 60%, respectively. The location of podzol soils (Entic Rustic Podzols (Ochric)) is predicted with an accuracy of only 29%. The traditional mapping method was able to better reflect the diversity of the soil cover on a large scale compared to the digital method.

Modern research proves the need to include waterbodies in regional and global models of carbon exchange. The concentration of carbon dioxide in surface waters is generally higher than equilibrium with a partial atmospheric pressure of 400 µatm allows. The study of the functioning and regional role of aquatic systems, especially regard to inorganic carbon dynamics, is insufficient, especially in circumboreal regions. The review highlights the theoretical foundations and relevance of studies of dissolved carbon dioxide; methodological approaches in assessing this indicator, as well as the role of dissolved CO₂ in natural waters of boreal and arctic regions. Soil organic matter and dissolved carbon dioxide are the main sources of CO₂ in surface waters, but this contribution has not yet been quantified. This is due to the underestimation of the abiotic aspects of soil gas exchange, the absolute predominance of studies of gas exchange at the soil-atmosphere interface without taking into account the interaction with groundwater, as well as methodological difficulties in measuring gas concentrations in soil-ground and surface waters. Instrumental measurement methods are not standardized, and the calculated ones have very high systematic and analytical errors. The conclusion points to the need to study the hydrological continuum: from source (terrestrial ecosystems) to large rivers and lakes, with particular attention to the incorporation of CO₂ from groundwater into the carbon budget of the entire watershed.

The water movement in soils contributes to the formation of a number of specific soil properties; their interpretation allows for to characterization of the features of both individual hydrological processes and the soil water regime, which is especially important due to the limited possibilities of soil wetness monitoring. The review considers the diagnostic indicators of mineral soils, determined in the field and laboratory conditions, characterized by different formation times and resistance to changes in environmental factors. Field methods for diagnosing soil moisture regime parameters make it possible to formulate hypotheses about the features of water behavior within the soil profile, which can later be confirmed or refuted as a result of laboratory diagnostic methods, regime observations, and physical and mathematiqcal modeling. In particular, on the basis of a standard field description of soils, it is possible to identify the zone of the greatest moisture turnover, areas of the soil profile, which are characterized by constant and periodic moisture stagnation, as well as determining the level of occurrence of the capillary fringe. Clay coats, root burrows, and soil animals paths mark the preferental flows. Laboratory diagnostic methods are aimed at assessing the quantitative ratio of hydrological processes in the soil; basically, they allow to characterize the source, duration and intensity of the period of soil overmoistering. The Schwertman criterion is the most commonly used analytical indicator for diagnosing soil overmoistering, the possibility and effectiveness of which has been shown for a wide range of soils. Verification of the results of hydrological modeling by soil properties is potentially possible for the processes of downward and lateral runoff, physical evaporation of moisture, transpiration, evapotranspiration and capillary rise.

The activity of CO₂ efflux, N₂ fixation, and denitrification, as well as the physiological state of the community of microorganisms-destructors were assessed depending on the decay stage of the coarse woody debris (CWD) in the incubation experiments with the coarse woody debris of Norway spruce (Picea abies L.) and podzolic soil (Retisol). The coarse woody debris and soil were sampled at the experimental sites of the Central Forest State Reserve (Tver Region, Russia). Maximal CO₂ emissions caused by CWD decomposition was associated with the decay stages III and IV. Also, the latter two showed maximal values of such sound indices of microbial activity as substrate induced respiration (SIR, 50 μg С–СО₂/(g h)), percentage of easily decomposable С in organic matter (А₁, 66%) and metabolic quotient qCO₂ (0.78). Unlike the СО₂ emission, maximal activity of N₂ fixation was at the earlier decay stage II. The values of N₂ fixation and denitrification activities indicate a gradual and complicatedly regulated transition process from the properties of bacterial and fungal communities of CDW to those in the soil during stages II, III and IV. The dramatic, more than 3-fold decrease was found only for C : N in CWD during the stages III–IV transition. СО₂ emission at the stage V increased dramatically. Nevertheless, the CWD organic matter even at this latest decay stage had lower sustainability than organic matter of podzolic soil.

A comparative analysis of physico-chemical and micromorphological properties in samples of 1968 sampling from virgin soils of the dry-steppe saline complex as the starting point of the 1968-2022 chronosequence was carried out. The study of climatic parameters for the period 1914–1968 showed that in the 54 years preceding the sampling, soils developed in relatively stable climatic conditions. Analysis of soil properties showed that on an almost flat area with a height difference of only 3.6 cm at a distance of 229 cm, soils differ significantly in depth and degree of salinity, degree of solonetzization, set of humus microforms and organic matter content, presence and size of clay coatings, degree of mobility of micromass. This confirms the patterns of moisture redistribution described in numerous studies in this area, even with very small elevation differences. Based on the set of available indicators, it can be concluded that soils of the microcatena are belong to different taxonomic units. The soil of the lower part of the microslope according to the USSR Soil Classification (1977) can be attributed to light chestnut soil, according to the international classification WRB (2015) it can be attributed to Haplic Kastanozem (Loamic). Soils with a high content of exchangeable sodium and the presence of clay coatings, located in the middle and upper parts of the microslope, according to both classifications belong to Solonetz.

In a multifactorial vegetation experiment, the effect of the composition and properties of soils and soil-sandy substrates contaminated with various doses of copper acetate on the morphometric parameters of spring barley seedlings was studied. It has been shown that the germination and vigor of seed germination, as well as the length of roots, aboveground parts, and dry biomass of plants depend in a complex way on the concentration of Cu in soils and substrates, as well as their buffering capacity to heavy metals. The presence of two mechanisms of Cu influence on plant development was established: metabolic at С_Cu < 500 mg/kg of soil and diffusion at С_Cu > 500 mg/kg. Using methods of regression analysis on experimental data, a multiple regression equation was obtained that combines morphometric parameters of plants, concentration of Cu in the substrates, and the buffering capacity of soils to heavy metals. On its basis, in the coordinates of soil buffering capacity – Cu concentration, a curve of values f the maximum permissible concentration of Cu in soils in the concentration range from 17 to 2047 mg/kg. It makes the possibility to separate the zone of permissible development of barley plants (reduction of morphometric parameters by no more than 15%) from the zone of exceeding the accepted value of maximum permissible concentration of Cu. Thus, maximum permissible concentration of Cu is considered not as a fixed value, but as a function of Cu concentration, soil buffering capacity, and plant species.