Том 52, № 11 (2019)

Soils of the Pavlovsk Park–the largest landscape park in Europe—have been studied, and large-scale mapping of the soil cover of the main areas of the park has been performed. Limnoglacial and alluvial deposits are the predominant soil forming materials in the park. Iron-illuvial soddy podzols (Umbric Podzols) predominate among the natural soils of the park, and gray-humus stratozems (Hortic Anthrosols) underlain by the limnoglacial deposits and/or by the buried soils are the main human-transformed soils of the park. The areas of urbostratozems are mainly confined to the Slavyanka River valley. The thickness of human-created stratified layer of stratozems and urbostratozems varied from 40 to 120 cm. Soils with an acid reaction predominate in the park, except for the Slavyanka River valley, where most of the soils have a neutral or an alkaline reaction. The organic carbon content in topsoils ranges from 0.9 to 4.4%. The majority of the park soils are characterized by the low content of available potassium and by the considerable variability in the content of available phosphorus. The results of the soil survey may serve as the basis for further monitoring studies and be helpful in the development of measures for the conservation and restoration of the tree stands in the park.

To characterize the native component of the hydrocarbon status of soils in different bioclimatic zones, representative soils were studied in the East European Plain within the middle and southern taiga, forest-steppe, and semidesert zones. The samples were analyzed for the contents of hexane-soluble bitumens (bitumoids), normal and iso-alkanes (C₁₄–C₃₅), individual polycyclic aromatic hydrocarbons (PAHs, polyarenes), and soil hydrocarbon gases. It was found that the parameters of the native hydrocarbon status of soils are rather similar in different bioclimatic zones. For the background (uncontaminated) soils forming on interfluves, the following concentrations of native hydrocarbons were determined: up to 25 ppm (often, less than 5 ppm) of hexane bitumoid, no more than 60 ppb of the sum of 11 PAHs, and no more than 1 ppb of individual n-alkanes. Polyarenes were represented mainly by the lightest two- and three-ring compounds. The content of hydrocarbon gases retained by the soils varied widely. In 100% of cases, methane was the most common gas (from 1.8 to 3994 ppmv, 5.14 ppmv on average). Ethylene was less common (0.04–54.5 ppmv, 4.1 ppmv on average). Heavier alkane gases were less common and were present in amounts ranging from 0.02 to 4.09 ppmv (on average, 0.53 ppmv).

The temperature regime and the dependence of thermal diffusivity on the volumetric water content in high-ash drained peat soils (Sapric Drainic Histosols (Lignic)) on woody peat underlain by grass, sedge, and woody peat layer in the Yakhroma River valley (Moscow oblast) were studied in terrain and laboratory on undisturbed samples. In the laboratory, the dependences of thermal diffusivity were determined in the course of sample drying by the Kondrat’ev method (a steady-state radial heat flow); whereas the terrain dynamic data on the daily temperature variations were used to solve the inverse problem by the heat wave method. The dependences obtained by laboratory and field methods showed a dome-like shape, the maxima of which were close (at the volumetric water content equal to 57–60%), but the thermal diffusivity obtained from the terrain data was 1.2 times lower at the maximum point. Considering the further use of dependences in predictive mathematical models, approximation of the curves by the method of Chang and Horton made it possible to evaluate the accuracy of the approximation parameters and to compare them. According to the laboratory method, the approximation errors grew reliably with an increase in the measured thermal diffusivity, which points to a systematic error in the laboratory measurement of the latter as dependent on the water content; this effect was not registered in the field method. The systematic errors in laboratory studies must be associated with shrinkage and vapor transfer.

Crop abandonment is a factor responsible for soil degradation in semi-arid regions. The effects of crop abandonment on soil restoration may depend on soil properties and climatic conditions of an area. In particular, soil hydraulic properties affect the vegetation recovery process. The objective of this study was to investigate the succession changes in water flow as a result of changes in soil hydraulic properties after crop abandonment under drought and non-drought conditions, and under water uptake by co-occurring perennial plants to clarify the observation that typical perennial grass species are seldom observed in abandoned fields. Soil hydraulic properties were measured in croplands which had been abandoned for different periods (2, 9, and 18 years ago) and in a grazed grassland site (control site). Hydrological processes in the soil profiles were simulated with soil hydraulic properties under drought and non-drought summer conditions with water uptake from perennial grass species. Suctioning the surface soils increased with the period of abandonment, with this trend being particularly obvious in a drought year. Soil water appears to be restricted in the later succession stage of abandoned fields and in grazed grassland for drought-tolerant plants. Dry soil and climate conditions are important factors determining the intrusion of the typical perennial grass, Stipa krylovii, into degraded abandoned fields. A water availability with low pressure (plant can use with low pressure) made difficult the intrusion of typical perennial grasses to abandoned cropland. This abiotic relation between soil hydraulic properties and climate conditions may play an important role for plant succession in abandoned cropland.

The unsaturated zone in the soil generally plays an important role in the transfer of water and pollutants in the underground environment. To simulate the water flow in this area, the relationships that express the variations of the water content and the hydraulic conductivity of the soil as a function of the pressure must be defined. In this context, determination of the hydrodynamic parameters constitutes an essential step for any study of the water and solutes transfers in the unsaturated zone. The purpose of this article is to identify the soil hydrodynamic parameters by direct method and inverse method, from the infiltration data by using the disc infiltrometer. These two methods of the characterization were applied on two plots: a plot of R’mel, sandy soil, and a M’risa plot, clay-loamy soil in northern Morocco. The results of the analytical and numerical modeling reproduced correctly the experimental measurements. A performance analysis of the models used was implemented to study the reliability of the estimated parameters. The values of RMSE ≈ 0.20 and R² ≈ 0.90 show that the inverse method remains a robust and accurate method for determining the soil hydrodynamic parameters compared to other conventional methods.

The seasonal dynamics of the structure of microbial biomass in a soddy-podzolic soil under fallow was assessed using luminescent microscopy. Samples from three soil horizons (P, 5‒15 cm, BEL, 30‒40 cm, and BT2, 50‒60 cm) were sampled monthly from March, 2017 to February, 2018, in the territory of Eldigino experimental station (Moscow oblast). In addition to microbial biomass measurement, soil temperature and moisture were recorded. The microbial biomass at all sampling times was dominated by fungi (up to 93%). Minimal microbial population and biomass were observed in the period from November to March. The biomass of prokaryotes increased twofold in May, the maximal values were observed in August and September. The length of actinomycete mycelium was maximal in July and August, when the soil water content was the lowest. Maximal fungal biomass was observed in July and September. Seasonal changes of microbial biomass were most pronounced in the upper soil horizon P, while they were more even in the BEL and BT horizons. Using regression analysis, we revealed a significant effect of temperature and sampling depth on the fungal and prokaryotic biomass. The results indicate substantial seasonal variations in biomass of soil microbiota, which should be taken into account when comparing soils sampled at different seasons.

The effect of long-term application of organic and mineral fertilizers on the organic carbon content and nitrogen regime of soddy-podzolic heavy loamy soils (Umbric Albeluvisols Abruptic) was studied in a long-term stationary experiment established in Perm region in 1976. Long-term crop growing (for about 40 years) resulted in the decrease of organic carbon content from 1.28 to 1.13%. The application of cattle manure at the rate of 40 t/ha and mineral fertilizers NRK (I rotation—N₁₂₀P₁₂₀K₁₂₀, II rotation—N₉₀P₉₀K₉₀, III–V rotations—N₆₀P₆₀K₆₀) slowed down the process of organic matter mineralization but did not completely compensate for the organic carbon loss. The application of sewage sludge at the rate of 40 t/ha once in the seven-field crop rotation allowed maintaining the organic carbon content in the soil at the initial level. To assess the composition of soil nitrogen, acid hydrolysis was used. The application of manure reliably increased the contents of difficultly hydrolyzable, hydrolyzable, and mineral fractions of nitrogen in the soil by 1.1–1.4 times Prolonged use of sewage sludge significantly increased (by 1.1–1.6 times) the content of total nitrogen and all its fractions in the soil. The application of mineral fertilizers contributed to an increase in the contents of total, easily hydrolyzable, and mineral nitrogen by 1.1–1.4 times. The maximum positive effect on the organic carbon content and the nitrogen regime was observed in the case of prolonged use of organic fertilizers against the background application of mineral fertilizers. The relative content of nitrogen fractions in the soil remained fairly stable and indicated the stability of nitrogen pool in the soil over time.

The studies were performed at the long-term stationary experiment on crusty hydromorphic solonetzes of the Baraba Plain during 1986–2017. In the humid year of 2013, the ground water level drastically rose from a depth of 250 cm to 50 cm, and secondary salinization was recorded. The content of soluble salts increased, their composition changed, the soil pH shifted to higher values, and the exchangeable sodium percentage increased. After lowering of the ground water table, salts were gradually washed out from the soil profile in the reclaimed solonetzes, and the positive effect of gypsum was partially restored. The soil adsorption complex was dominated by Mg²⁺ in the control variant and by Ca²⁺ in the reclaimed solonetzes. This phenomenon should be taken into consideration when reclaiming solonetzes, because the positive effect of gypsum application is preserved after secondary salinization.

The results of mapping and assessing the sealing rate of soils in the city of Volgograd (Russian Federation) are presented. Soil mapping is based on the interpretation of satellite photographs with further control of its results by field surveys at 35 plots within different functional zones of the city. According to the results of the interpretation of satellite images, the portion of sealed areas determined for the functional zones ranged from 0 to 99%, including soils under buildings and roads. The MapInfoProfessional 10.0 software was used to process the obtained data. Based on the results of this assessment, which was performed for the first time within the new boundaries of the city, we quantified the areas of particular soil types and associations of both natural and anthropogenic origin, as well as the sealing rate of soils. The natural soils in Volgograd are dominated (25.86%) by chestnut soils of various texture and alkalinity [23] (Cambisols and Cambisols (Sodic)), and there are 18.67% of natural surface-transformed textural-carbonate agrozems (Cambisols (Aric, Protocalcic)). The range of anthropogenically transformed soils is wide, including the sealed soils (Ekranic Technosols), urbostratozems (Urbic Technosols), chemically contaminated urbostratozems (Technosols (Toxic)), and quasizems (Urbic Technosols). Anthropogenically transformed soils mostly occur in the eastern part of the city, and natural soils dominate its western part. The total portion of sealed surfaces is 18% of the Volgograd area. The calculation is based on the assessment for particular functional zones of the city. The results can be used to solve problems of spatial planning within the modern functional zones and implementation of works on gardening and landscaping of the urban area.

According to the results of land assessment, the cadastral value of agricultural land in Tyumen oblast varies from 2900 rubles per hectare for peat-podzolic soils to 69 300 rubles per hectare for ordinary chernozems. The development of solodic and solonetzic processes decreases the cadastral value of chernozems by 50 to 90%. The cadastral values of podzolic, soddy-podzolic, and gray forest soils do not exceed 10 000 rubles per hectare. The cadastral value of meadow-chernozemic and meadow soils is 41 200 and 25 700 rubles per hectare, respectively. A sensitivity of the cadastral value estimation approaches to different soil-geographical conditions is demonstrated.