Том 51, № 7 (2018)

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.

Data on soddy-podzolic soils with the second humus horizon in the southwestern part of Kirov oblast are discussed. These soils were first studied by the authors on mantle calcareous loams of the Yarano- Kokshagskaya Plain in the eastern part of the Central Russian southern-taiga province of medium-humus soddy-podzolic soils of European Russia. The aim of this study is to reconstruct the history of the development of soil properties and soil cover in automorphic landscapes of this region. Morphology, substantive properties of mineral and organic components, soil genesis and evolution are analyzed using a set of physical, chemical, physicochemical, biochemical, and geochronological methods. The results of our study attest to the relict character of second the humus horizon and polygenetic nature of the studied soils. These soils have passed through two essentially different evolutionary stages in the Holocene: the accumulative stage in the first half of the Holocene and the accumulative-eluvial stage of erasing evolution with preservation of some inherited features in the second half of the Holocene. According to their properties, the studied soils are analogous to the earlier studied southern-taiga Vyatka–Kama province of high-humus soddy-podzolic soils of the northeast. At present, plowing of these soils leads to a partial or complete destruction of the second humus horizon; thus, spontaneous degradation processes are complemented by the human-induced soil degradation. A tendency for a gradual disappearance of these soils from the soil cover under the influence of natural and anthropogenic factors has been noted. The materials presented in this paper may be useful for organization of specially protected soil areas in the southwestern part of the Vyatka River basin.

On the basis of thermodynamic concept on competitive interphase interactions, the idea is forwarded about the ionic-electrostatic mechanism of water retention capacity and aggregative stability of fine solid particles in soil physical systems. The author applies modern data on the nanostructure of colloidal disperse complex of soil physical systems in the gel form, i.e., in the form of noncapillary two-phase system of resistant to aggregation particles separated by solvate layers. Disputable questions are discussed about the role of surface energy and hydration of cations in water retention as well as about the relationship between the matrix (disjoining) and the osmotic water pressures. The fundamental ionic-electrostatic model of water retention capacity is analyzed for the colloidal-disperse bodies in the areas of sorptive and film water on the water retention curve (WRC) in the form of interaction between thermodynamic potential (disjoining pressure), water content, and dispersity (effective specific surface area) of the solid phase. On the basis of this model, the potential dependence is shown between the dispersity and the mobile thermodynamic factors (i.e., temperature, charge, and concentration of ions in the electrical double layer), and the method of estimating the effective specific surface area from the WRC is proposed as an alternative to the commonly adopted BET method. For standard conditions, under which the dispersed system with monomolecular liquid layer maintains its aggregative stability, the specific surface area is calculated according to the WRC slope (the angle coefficient in semi-logarithmic coordinates) and the value of the effective size of water molecules. Simultaneously with the dispersity assessment from the WRC, the energy indices of interphase interactions— the generalized Hamaker constant and the surface tension at the solid–liquid interphase—are determined.

Land use and soil cover patterns of arable lands in Balakhna district of Nizhny Novgorod gubernia in the last quarter of the 18th century and in the middle of the 19th century were studied with the use of the General Land Survey plan of Balakhna district (scale 1 : 84000), the map of Nizhny Novgorod gubernia by Mende (scale 1 : 42000), and the State Soil Map (scale 1 : 1 M). The data obtained attested to a steady and considerable decrease in the plowed area during that period. According to the historical materials, at the end of the 18th century, plowland occupied about 1290 km², or 32% of the entire district (4200 km²). In the middle of the 19th century, the plowed area decreased to about 990 km² (25%). According to the modern statistical data on land use in Balakhna district (within its boundaries of the 18th–19th centuries), the area of plowed fields is less than 700 km² (18%). This means that at least 14% of the study area is occupied by the postagrogenic soils. If we take the plowed area of the district in the 18th century for 100%, we can conclude that more than 40% of formerly plowed lands have been transformed into long-term fallows. The absolute predomination of soddy-podzolic soils (Retisols) is typical of the soil cover of Balakhna district. In the course of the reduction of the plowland area from the end of the 18th century to the middle of the 19th century, the percent of different soils composing this area did not change much. In general, the impact of soil quality on the decrease in the plowland area in that period is not observed.

A new method of instrumental measurement of the intensity of rill and linear erosion on slopes by the method of terrestrial laser scanning is proposed. This method was tested on four plots in 2012–2016 with the use of Trimble™ GX, Trimble™ VX, and Trimble™ TX8 laser scanners. The terrestrial laser scanning is characterized by a high precision and rapidity, which could not be previously achieved by other devices. It has a number of advantages: registration of various types of erosion of temporary water streams; measurements from a distance without the disturbance of the studied surface and providing the safety of works; and calculations of morphometric parameters of slope using a high-precision digital model of topography. The given examples show that this approach may be applied to assess the denudation-accumulative balance of the moved soil material on slopes, to determine the dynamics of amount of deposits on different parts of a slope as a result of different kinds of surface runoff, and to identify spatial regularities of the formation of the network of rills and gullies. In addition, laser scanning makes it possible to perform an integral assessment of the combined impact of the entire combination of exogenous processes developed on slopes and affecting the soil cover. The observations on test plots showed a rather great role of autumn rains in the total soil loss from erosion. The data obtained were used as the basis for the elaboration of practical recommendations concerning the survey organization and monitoring of erosion with the use of laser scanning.

An experiment on transformation of biotite (fraction <1 μm) particles placed into containers with different permeability in the AEL horizon of podzolic soil was performed in order to estimate the contribution of different factors to the transformation of biotite in the modern soil. After two-year-long incubation in the AEL horizon, biotite was transformed into vermiculite, mixed-layer biotite–vermiculite, and pedogenic chlorite. The most intense vermiculitization of the biotite took place under the impact of fungal hyphae and, to a lower degree, fine plant roots and components of the soil solution. The formation of labile structures from biotite was accompanied by thinning of the mica crystallites, the disturbance of the homogeneity of layers, the removal of interlayer K, the removal and oxidation of octahedral Fe, the increase in the sum of exchangeable cations, and the appearance of exchangeable Al. The process of chloritization was definitely diagnosed upon the action of plant roots and fungal hyphae on the biotite. Strong complexing anions released by fungal hyphae partly inhibited chloritization. Chloritization led to a decrease in the cation exchange capacity of vermiculitic structures.

Forty streptomycete strains have been isolated into pure culture from two eroded zheltozems (yellow soils) of the Fujian province. Their antagonistic activities and contributions to the formation of soil resistome have been characterized. The estimation of the antimicrobial effect of natural isolates allowed revealing 6 strains simultaneously inhibiting the growth of the fungi Fusarium oxisporum, Alternaria alternata, Paecilomyces sp., Trichoderma sp., and Candida albicans. One strain (Streptomyces aburaviensis F2-6) with a wide range of antifungal actions was also active against the bacteria Pseudomonas putuda, P. fluorescens, P. sepacia, Streptococcus sp., and Escherichia coli. It has been shown that the share of isolates with a wide range of antimicrobial effects (44%) and a high antagonistic activity (77%) in zheltozem of the urban Zhangzhou district is significantly higher than in the soil of the village of Hongkeng (22 and 39%, respectively). According to the resistome concept, determinants of resistance to antibiotics first appeared in their producers; they can be transmitted to other bacteria in the soil due to horizontal drift. Tests of streptomycetes for resistance to antibiotics with different acting mechanisms (inhibitors of the synthesis of cytoderm, protein, and metabolic pathways) has shown that the share of cultures with multiple resistance in zheltozems does not exceed 25–31%. No resistance to all of the studied antibiotics is characteristic of 15–16% of the strains isolated from zheltozems. The obtained data can be used for assessing the risks related to the transfer of antibiotic resistance genes from the environment to clinically valuable pathogenic species.