Since Chernozems are among the most fertile soils in the world, the study of their degradation is of great interest. However, the microstructure and composition of the soil organic matter (SOM) in eroded Chernozems have not yet been sufficiently studied. We studied the SOM and aggregate states of eroded Chernozems using the example of two catenas with arable Haplic Chernozems in the Kursk region of Russia. In the plow horizons (the part of the soil most susceptible to water erosion), we determined the mean-weighted aggregate diameter (MWD), structure and water stability coefficients (SC and WS; dry and wet sieving, respectively), soil organic carbon (SOC) content, and SOM composition and content (qualitative and quantitative micromorphological analyses, respectively). It was shown that with an increase in the degree of erosion, the content of SOC decreased significantly, according to both chemical and micromorphological methods of evaluation. No significant relationships were found between the degree of erosion and the indicators of the structure (except for WS, which was significantly lower in non-eroded Chernozem than in slightly and moderately eroded soils). With the increasing degree of erosion, the humus state of these soils deteriorates at the microlevel, the intensity of humification decreases, the depth of the appearance of assimilated biogenic aggregates with finely dispersed calcite in the profile increases, the structure is destroyed, lumpy aggregates form, and the proportion of planar voids increases. The downslope transport of the soil solid phase under the impact of erosion is accompanied by the accumulation of the transformation products of carbohydrates in the Chernozems in the lower part of the catena. In the Chernozems located in the transit position of the slope, the composition of SOM is characterized by the predominance of lipids and nitrogen-containing compounds. Our unique results contribute to a deeper understanding of the formation of structure and water resistance in eroded soils.

Ручейковая эрозия вносит существенный вклад в процессы деградации пахотных почв, поэтому целью работы было продолжение разработки гидравлических и статистических методов для оценки транспорта мелководными потоками почвенного материала. Для этого на примере черноземов типичных среднемощных легкосуглинистых на лёссовидных суглинках глубокопахотных несмытого, слабосмытого и среднесмытого проведена верификация уравнения транспортирующей способности водных потоков малой глубины. Образцы для исследования были отобраны в Курской области. Сопоставление полученных экспериментально и рассчитанных по уравнению значений мутности показало удовлетворительное соответствие. Средняя относительная ошибка расчетов составила по модулю 18.0%, а коэффициент корреляции - 0.89. В модельном эксперименте на большом эрозионном лотке было установлено, что средневзвешенный диаметр влекомых потоком агрегатов увеличивается с возрастанием скорости потока, а диаметр отложившихся в русле агрегатов уменьшается. Данная закономерность выявлена как при воздушно-сухом, так и при капиллярно-увлажненном исходном состоянии образцов. Установлено, что водный поток при низкой скорости (0.3915 м/с) выносит прежде всего многопорядковые и наиболее плотные прогумусированные агрегаты (в том числе копролиты), в то время как в русле откладываются обломки менее гумусированных агрегатов и отдельные минеральные зерна. Выяснено, что такие особенности характерны для обоих вариантов исходного состояния образцов. При этом отмечено, что размеры фракций вынесенных потоком агрегатов при обоих исходных состояниях образцов совпадают, то же характерно и для отложившихся в русле агрегатов.

The soils of arid regions are sensitive to short-term climate changes, which are most quickly manifested in the saline state of alkaline and saline soils. Long-term climate changes are reflected in more stable soil characteristics, such as grain size distribution and microstructure. These properties can be used as indicators to assess the direction and degree of soil transformation under the influence of climate change in the longer term. This article presents data collected on the territory of the Caspian Depression near the Dzhanybek Research Station of the Institute of Forest Science RAS. The studied object is represented by microcatena of light chestnut soils with varying degrees of severity of the saline process which is located in the saline complex between the I and II belts of the Chapaevsk-Vladimirovka State Forest Wind Belt. The height range between the studied pits is 3.6 cm. The dataset includes data on soil grain size distribution, organic carbon content, the composition of exchangeable cations, the salt composition of soil-water extract and microphotographs of the state of the light chestnut soils in 1968. This year is the starting point for modelling soil properties and assessing soil changes in this area due to climatic changes. The weather data are collected at the Janybek weather station between May 1951 and December 1992. It includes daily, monthly and annual data on air and soil temperature, wind speed and direction, air moisture, precipitation, depth of soil freezing, snow density and thickness. Using the data presented in the article, it is possible to assess the nuances of global warming in the Caspian lowland and reconstruct changes in soil properties associated with it. In the future, such reconstructions will become a tool for making forecasts of both climatic and soil changes in this territory.

The aim of this study was to develop an approach to assessing the impact of rill erosion on aggregates of typical chernozem aggregates in a laboratory experiment with flume. Aggregates from...

The purpose of this study was to investigate the applicability of semiautomatic segmentation methods for obtaining and evaluating morphometric parameters of soil aggregates in artificially prepared loose samples in soil thin sections. The object of the research is typical arable Chernozem. The aggregates were separated by wet sieving method from loose sample of upper 10 cm of the plowing horizon after erosion by a model shallow water flow on a large erosion tray. The aggregates, loosely scattered on the glass and fixed with polyester resin, were used to produce the thin sections. Images of the thin sections were taken under a polarizing microscope and then were processed using two methods compared: Adobe Photoshop + CTan and Thixomet Pro. Data on morphometric parameters of aggregates were obtained: the shape factor, the degree of roundness and the coefficient of aggregate surface roughness. The convergence of the results obtained using Photoshop + CTan by three researchers was evaluated by comparing samples using the Student's test and the Mann-Whitney test. The convergence of the averaged results obtained using Photoshop + CTan and the results obtained using Thixomet Pro was evaluated using the Mann - Whitney test. No significant differences were found between the parameters of the same aggregates obtained using a combination of Adobe Photoshop and CTan programs by different researchers. No significant differences were found between the parameters of the same aggregates obtained by the compared methods. So, one can conclude that the reliability of determining the morphometric parameters of soil aggregates using Thixomet Pro is comparable to the reliability of results when working with images of sectionsin CTan after binarization in Adobe Photoshop. The method of obtaining data on morphometric parameters of soil aggregates using Thixomet Pro completely eliminates the possibility of subjective error, shows a high degree of automation, reproducibility and reliability of the results obtained, and is faster.

In the closed depressions of the forest-steppe, unique soils form that differ significantly in their properties from the zonal Chernozems. These soils have a light-colored, acidic Albic horizon and the complete absence of carbonates. They resemble podbels, which are formed in the southern Far East of Russia, with their different soil-forming processes, regimes, and genesis. The aim of this study is to interpret the genesis of the soils in the center of the closed depression by analyzing their morphological, micromorphological, chemical, physical, and physico-chemical properties. This will help to determine the main diagnostic criteria for their classification. The depression is located in the Oka-Don Lowland, in Tambov Oblast (52.0398°N, 41.1839°E, See Fig. 1a). We collected a total of 39 samples, from three walls of soil pit, at 10-centimeter intervals, to a depth of 130 centimeters. For micromorphology, we took samples from all genetic horizons, in triplicate (12 samples). In the pre-dried and homogenized samples, we determined pH values, total dissolved salts and soluble salt content (conductivity), particle size distribution (laser granulometry, with preliminary ultrasonic treatment at an energy level of 450 joules per milliliter), total carbon (by dry combustion), cation exchange capacity, exchangeable cation composition (using Pfeffer's method), and iron content in oxalate extracts (Tamm's method) and dithionite-citrate extracts (Mehra-Jackson method). We also calculated the Schwertmann ratio and and the degree of hydromorphism were calculated as indicators of soil overmoisture. The diagnostic properties of the studied soil (See Fig. 1b) include: (1) a thick (30 cm) mollic horizon, rich in organic carbon, with a loosely aggregated structure and varying degrees of organic matter decomposition; this horizon is overlain by a (2) light-colored albic horizon, which has signs of humus leaching and contains up to 5% of small-sized iron-rich concretions, and (3) an illuvial horizon that has a weaker structure and a higher concentration of concretions than the overlying horizon. This horizon also has cutans along the edges of ped. The soil demonstrates a sharp decrease in carbon and a gradual increase in pH from slightly acidic to neutral values with depth (See Fig. 2). The middle part of the profile has a slightly higher clay content compared to the mollic horizon. The top 10 cm of the soil contains soluble salts at a concentration of 106 mg/ L (0.14% of soil dry mass), classifying this layer as slightly saline and chloride-magnesium. However, at the lower boundary of the soil surface (20-30 cm), the salt content drops sharply to 27 mg/L (0.04% of the dry soil mass) and does not exceed 50 mg/L in deeper layers, indicating that the soil is not saline. The anion-cation composition of the soil in the depression remains consistent throughout the profile. There are two peaks in the cation exchange capacity, one in the humus layer and another at a depth of 100-130 centimeters. This latter peak is likely due to an increase in exchangeable Ca2+, which is probably caused by its influx from solutions in the underlying carbonate parent material. The relatively high content of soluble salts and exchangeable sodium in the topsoil can be attributed to lateral water flow from surrounding depressions with solonetz and meadow-chernozem soils. Based on the Schwertmann's and hydromorphic criteria, the upper part of the soil profile, particularly the mollic and albic horizons, experience prolonged surface overmoisture. These coefficients decrease sharply in the gleic horizon. Based on a comprehensive study of soil properties, we can conclude that the light-colored horizon of the depression soil we studied is predominantly eluvio-gleyic in nature, with concretions (See Fig. 3 d, f) and cutans (See Fig. 3 c, e). In the underlying horizon, Schwertmann and hydromorphic criteria indicate seasonal surface overmoistening and periods of drying. The additional factor contributing to the formation of the light-colored horizon may be the presence of sodium in the upper horizons of the soil-absorbing complex, ranging from 4 to 14%. The soil profile formula of the studied depression soil is AH- AHel-ELhi,g-BTg (according to WRB, Ah-Eg-Btg); in terms of the genetic horizons it is absent in the Russian Soil Classification, partially corresponding to darkhumus pseudo-gleyic (AH-EL-BTg-BCA-Q; Calcic Albic Mollic Planosol, A-Eg-BtBk-Bgk), dark-humus podbel gleyic (AU-ELg-BTg; Mollic Albic Stagnosol, A-EgBtg). Unlike the dark-humus pseudo-gleyic soil, the studied soil does not contain carbonates, which are leached from the soil due to its large catchment area (55 hectares). Different from dark-humus podbel gleyic, the studied soil differs in the nature of the upper horizon and less pronounced processes of iron segregation in the lightened horizon (a lower quantity of concretions). We hypothesize that the water regime of the depression soils is less contrasting, with a smoother alternation of periods of overmoistening and drying compared to the podbels of the Far East, which may explain the lower quantity of concretions in the depression soil. Following the classical tradition of Russian soil science – reflection of the major soil-forming processes in the soil name – the studied depression soil can be termed as dark-humus elluvial gleyeic. With the expansion of soil studies in depressions and the identification of soils with a similar profile structure, introduction of an independent type of peat-dark-humus gleic soils into the Russian Soil Classification may be proposed.