Articles

In hydromorphic soils are important not only sustainable Fe-minerals, defined traditionally in dried soil, but also unstable Fe-minerals, changing the colors of the clay after extracting the sample fr om the soil, as well as — weakening gley signs in the dry season. New indicators are offered for the additional characteristic of Fe-minerals. The first is that it characterizes the interaction of active Fe-minerals with colloids, it is index I: I = CEC/Fe (free), wh ere CEC is the cation exchange capacity. The second indicator is the change in the gley color after drying, assessed by the change in the redness Да*. In Fe-enriched, reduced gley Gr with a low index value (/0,1) and a strong increase Aa* ~ 9 after drying, the green rust is transformed into a brown lepidocrocite. During the humidity decrease, the transition of the reduction gley to the oxidized gley is accompanied by a change in the composition of the green rust: the transformation of fougerite into a trebeurdendite: Fe-ephemera with a higher degree of Fe oxidation and the growth of Да* ~ 3. When oxidized gley Go with the index I = 2—8 is dried, the slow Да* growth is caused by the inhibition of Fe-hydroxide crystallization by colloids. In the “de-ironed” gley Gdf with a high value the index 1= 6—27, the lack of red growth (a* « 0) on drying, is probably due to the Fe clay minerals inertia.

The paper presents a comparative analysis of the structural and functional characteristics of the microbial communities of the gray forest soil of fallow and intensively cultivated areas. Long-term anthropogenic impact with massive annual mineral fertilization when growing a monoculture of potatoes has led to the degradation of the soil microbial system. A catastrophic decrease in the functional potential of the microbial system (environmental services) is shown using eco-exergy as a thermodynamic indicator of the “health” of the soil.

The texture of bottom sediments of the Simmy River and its tributaries in the area of the “Bolon'sky” reserve (Khabarovskiy region, Far East) was studied with methods of laser diffractometry, sedimentation and electron microscopic analysis. It was found out that the texture of Simmy sediments in downstream is characterized by the accumulation of fine sand, which corresponds to alluvial-lake genesis of the studied area. In the wellhead part of river sediments are formed mainly by suspended sediments with a predominance of the clay fraction. This is due to the impact of the floodplain Bolon Lake, which level fluctuations correspond to changes in the level of water in the Amur River. It is shown that coagulation and deposition of suspended particles with low content of organic matter (< 1%) leads to the formation of volumetric aggregated, dense and viscous sediments. The high content of organic matter in sediments (> 6%, the Kirpy River, the tributary of the Simmy River) leads to the “nodal” differentiation of spatial structures and to the formation of porous microaggregates.

The taxonomy of peat soils is not currently given more attention, especially with regard to taxonomic units in the species rank. The procedure of diagnostics of 51 soil profiles in the various oligotrophic mire types in the Numto nature Park (north taiga subzone of West Siberia) allows to make some proposals to improve the existing soil classification. These ones are: 1) to limit the peat horizon thickness in the peat-gleyzem type to 30 cm; 2) to divide the peat-gleyzem type by the trophic status into oligotropic and eutrophic subtypes; 3) to expand the list of taxa, determined by the botanical composition of peat, by means of the division of soil species into subspecies on the basis of classifications of peat and peat deposits; 4) to use current vegetation as one of the main diagnostic (indicative) criteria in determining the soil type in mires; 5) in order to determine the variety of peat soil it is suggested to use the degree of decomposition of the peat layer underlying the peat soil. The article draws attention to the difficulties in determining the classification position of soils of frozen large mounds in palsa bogs and proposes alternative solutions to this problem.

We discuss the dynamics of the snow cover and its composition for the period 2013-2018 is shown that the annual dynamics of the snow cover is characterized by the alternation of high and low values. Thus, the highest values were typical for the winter of 2012/2013, followed by a decrease in 2013/2014. The leading role in the distribution of snow cover belongs to the position of the elementary landscape within the geochemical landscape. In all years of research, the water equivalent of snow cover is characterized by bicarbonate-calcium composition. The content of micro components in General is in the same order with the results given for the South taiga landscapes. Some excess of individual components in the composition of snow water in comparison with Meshchersk and Baikal landscapes, taken as a background, due to the proximity of the studied geochemical landscape and the main road M-10 (Moscow-St. Petersburg). It is assumed that the relatively high content of calcium in the snow water of the superaqueous landscape is associated with its possible arrival from the surface of meadowmarsh carbonate soils, boiling from the surface. Sulfate ion has been found to play a leading role in the diagnosis of atmogeochemical pollution, which is partially established for the studied landscapes.

The resistance to mineralization of water soluble organic matter (WSOM) extracted from a litter of Podzol is increased upon the interaction with the mineral horizons. Both the fraction of WSOM susceptible to mineralization and the average rate of decomposition decrease after the passage through E-horizon, by 2-3 times respectively, in comparison with the values obtained for the initial WSOM. Sorption in the BF horizon gives extra stability to the incoming organic matter. The relative content of mineralized carbon is reduced to 2% (by 8 times). In natural soils sorbed organic matter can be even more resistant to the mineralization, due to lower temperatures and less biological activity, so it can be considered as the basis for the formation of a humus storage. Taking into account the calculated rate of mineralization, the accumulation of the organic carbon in the BF horizon due to WSOM sorption, may range up to 13,5/100 g per year, but this value depends on the concentration of organic substances in soil solutions, hydrological regime and other factors.

The influence of anthropogenic activity on the quality of urban alluvial soils, the conditions of growth and the state of tree plantations is estimated. The level of negative consequences for natural components correlates with the degree of human exposure. In the profile of soils moisture decreases, humus content varies in different directions, pH of waters and electrical conductivity increase. Densification of soils and inhibition of biological activity are noted in the surface horizons. The coefficient of the ecological state of soils decreases by 6-24% compared to the optimum conditions. The correlation analysis showed the presence of a significant weak matching between vegetation state and soil quality (Spearman's coefficient is -0,53).

A comparative description of the structural and functional organization of plant litter and forest floor in the course of natural postagrogenic reforestation in the chronory series of ecosystems for 12, 40 and 100 years is given. As the age of the stand increases, an increase in the total reserves and diversity of litter types, a decrease in the proportion of easily decomposable components, and a decrease in their pH and ash content are found. The change of ground cover is accompanied by the replacement of grass cover with grass-shrub, which indicates a decrease in the trophicity of ecosystems. The characteristics of the litter are adequately reflected by the composition of the ground cover. As the stand is restored, a regular decrease in the decomposition intensity of the ground detritus and the speed of the biological cycle occurs. Spatial differentiation of litter types serves as a trigger for the subsequent divergence of soil organic profiles.

Speciation of ²²⁶Ra and ²³²Th in sod-podzolic-gley concretionary soil are studied. It has been shown that with periodic overmoistening by surface waters and alternation of reducing and oxidizing conditions, the mobility and availability to plants of ²²⁶Ra is substantially higher than ²³²Th. The sum of fractions available to plants (water-soluble and exchangeable) and mobile (water-soluble, exchangeable and mobile) of ²²⁶Ra is 2-10 times higher than ²³²Th. Segregated ferruginous nodules formed in the eluvial horizons of this soil have a weak effect on the mobility of ²²⁶Ra, but significantly reduce the mobility of ²³²Th, much of which is substantially fixed inside the crystal lattices of newly formed minerals.

The ²²⁶Ra, ²³²Th, ⁴⁰K vertical profiles were studied in relation with the soil properties: pH_H2O, the sum of exchangeable Ca²⁺ and Mg²⁺, the degree of saturation with bases, the content of humus, mobile forms of phosphorus and potassium. An increase in the specific activity of ²²⁶Ra, ²³²Th, ⁴⁰K associated with the accumulation of humus and the biogenic accumulation of mobile forms of potassium and phosphorus in the upper 0-10 cm layer of horizon A in the soil of the oak forest was detected. The removal of ²²⁶Ra from the middle part of the profile of dark gray forest deep-carbonate soil was recorded. A positive correlation between the specific activity of ²²⁶Ra and the sum of the exchange bases Ca²⁺ and Mg²⁺ indicating the conjugate behavior of these elements-analogues in the horizons A, A(AE), AB and the lower horizons B1, B2, B3 was revealed. Removal of ²³²Th from horizon A(AE) and accumulation in horizon AB under conditions of local podzolization of dark gray forest soil in birch forest was observed.