Humus Profiles Research Articles

Sorption of humus and its distribution in the profile of chernozems depending on the granulometric composition

Particle-size composition is a fundamental characteristic that has a significant impact on many properties and regimes of soils, including sorption and fixation of humus by elementary soil particles (ESP). The main role in increasing the humus content of soils belongs to ESP with sizes <0.01 mm. We examined the structural features of humus profiles of leached chernozems formed on soil-forming rocks of different granulometric compositions. For this purpose, a large sample of data on the quantitative content of humus in chernozems of different granulometric compositions was analysed. The goal of the research was to identify the dependence of humus sorption on the granulometric composition of chernozems, and also to reveal the features of the profile distribution of humus in them. Objectives: conduct field research of chernozems of different granulometric composition; select soil samples and conduct a series of laboratory studies of these samples for the identification of the sorption properties of ESP in relation to humus; identify the features of humus distribution in soils of different granulometric compositions. It has been shown that with an increase in the granulometric composition of the content of ESP related to physical clay (<0.01 mm), the sorption capacity of the soil for humus increased. Thus, from sandy loam (ESP <0.01 mm=14-20%) to clayey varieties (ESP <0.01 mm = 61-64%) of chernozems, the humus content increased, respectively, from 3.88 to 7.09%. The thickness of the humus layer increased in the same direction from 22 to 100 cm. Therefore, soils of different granulometric compositions have their own structural features of the organoprofile, consisting in the nature of the humus distribution.

Distribution patterns and driving mechanism of soil protozoan community at the different depths of Larix principis-chinensis forest in the Luya Mountain, China.

To reveal the assembly mechanisms of soil protozoan community in subalpine forest ecosystems, we analyzed the composition and diversity of protozoan communities and their drivers at the six strata (the litter profile, humus profile, 0-10 cm, 10-20 cm, 20-40 cm and 40-80 cm) of soil profiles in subalpine Larix principis-rupprechtii forest in Luya Mountain using Illumina Miseq high-throughput sequencing technology. The results showed that protozoa in the soil profiles belonged to 335 genera, 206 families, 114 orders, 57 classes, 21 phyla, and 8 kingdoms. There were five dominant phyla (relative abundance >1%) and 10 dominant families (relative abundance >5%). The α diversity decreased significantly with increasing soil depth. Results of PCoA analysis showed that the spatial composition and structure of protozoan community differed significantly across soil depths. The results of RDA analysis showed that soil pH and soil water content were important factors driving protozoan community structure across soil profile. Null model analysis suggested that the heterogeneous selection dominated the processes of protozoan community assemblage. Molecular ecological network analysis revealed that the complexity of soil proto-zoan communities decreased continuously with increasing depth. These results elucidate the assembly mechanism of soil microbial community in subalpine forest ecosystem.

Short–Range Variation of Humus and Carbonate Profiles of Arable Chernozems (Key Site in Belgorod Region)

The short-range variation of soil properties is a particular expression of the spatial soil variability; it is non-directional short-periodic (in the range of a few meters) changes in soil-profile features. The short-range variation of soil properties is aimed to characterize the continuum nature of soil cover instead of the discrete (as in the soil cover pattern theory), thus the soil cover is presented by a continuum field of various soil properties, and the boundaries of the selected soil properties ranges may or may not coincide with the soil taxonomic boundaries. The study is based on soil data of three parallel transects (length 240 m) in the watershed, perpendicularly crossing the 60-year-old shelterbelt in their central part. The sampling step was 10 m on agricultural fields, 6 – under the shelterbelt; In total, the features of the humus (the content of organic carbon in the 0–20 cm layer, the thickness of the humus horizon and profile) and carbonate (the effervescence depth, the carbonate content in the effervescence layer and the horizon of maximum accumulation of carbonates) profiles were studied at 75 points. It was revealed that the parameters of the humus and carbonate profiles of soils have periodic changes with a step of 6–10 meters. The parameters of the humus profile are characterized by lower coefficients of variation (less than 30%) than the parameters of the carbonate profile of soils (more than 50%). The growth of trees on agrochernozems (Haplic Chernozem (Aric)) for 60 years led to the formation of new taxonomic components (postagrogenic agrochernozems (Haplic Chernozem)), characterized by a smaller lateral variation in soil properties compared to arable soils. In total, 3 types of soils are found within the studied area: agrochernozem (64 points; Haplic Chernozem (Aric, Loamic, Pachic)), clay-illuvial agrochernozem (7 points; Luvic Chernozem (Aric, Loamic, Pachic) and Luvic Chernic Phaeozem (Aric, Loamic, Pachic, Loamic, Pachic)) and agrochernozems, clay-illuvial quasigley (4 points; Luvic Stagnic Chernic Phaeozem (Aric, Loamic, Pachic)), including 8 subtypes.

Humus profile specificity of chernozems of the Ob river left bank within the Priob Plateau

Purpose of the study: to identify the features of chernozem humus profiles of the river Ob left bank within the Priob plateau (south of West Siberia) and the reasons that determined their diversity. Place and time. The south of West Siberia (Topchikhinsky district of the Altai Territory), the north-eastern part of the Priobsky plateau, the steppe zone of the Pre-Altai province of the Kulundinsky-Aleysky district, the key site "Volodarka" on the eastern edge of the Porozikhinsky-Aleysky ridge (52°41-42' N and 83°38'E). Sampling was carried out annually in August. Methodology. The collection and interpretation of materials are based on the principles and rules of the systems approach and soil ecology. The objects of study were southern and ordinary chernozems confined to different parts of the Volodarka key site (according to the soil classification of 1977; these classification names of soils are used in the text; according to the new Classification of Russian Soils (2004), the soils belong to the subtype of migratory-mycelial and textural-carbonate; according to WRB-2015 they are in the reference soil group Chernozems with the qualifiers calcic and siltic). The characteristics of humus profiles were obtained using traditional methods. All methods of analytical and instrumental study of humus and its individual components were identical. Methodological features of the research include detailed sampling (every 5–10 cm or less within the visual boundaries of the horizons) in late summer and the absence of strict methods for purifying preparations from mineral impurities. In this work, the concepts of “humus” and “system of humus substances” in soils are used as synonyms. Main results. The humus profiles of the chernozems of the studied territory, currently functioning under the same conditions, have a significant variation in characteristics, representing a range of options typical for such soils (when, based on the combination of characteristics of elementary humus-forming processes - EHP - the upper part with the humification-transformation type of their structure and the lower one - with a transformation-migration type of combination of EHP), to varying degrees of structural complexity (when several parts are distinguished with different quantitative ratios of humus substances parameters with the predominance of their self-healing processes against the background of other EHP). The main characteristics of the studied buried paleosols lie within the limits peculiar to soils formed in temperature conditions optimal for humus formation, but different moisture conditions. Conclusion. A significant difference in the qualitative and quantitative characteristics of chernozem humus profiles of the Ob river left bank within the Priob Plateau is due to both the complex history of the territory development, and different levels of self-healing capabilities of the natural open self-regulating humus substance system, depending on environmental conditions during the period of its formation. During complex history of the territory development different horizons of Middle Pleistocene soils came to the surface in different places, and therefore are found within the thickness usual for mature full-profile modern soils. The advantage of using humus profiles when analyzing the state of soils and the natural environment that forms them is the possibility of conducting a more detailed analysis of the variability of properties, the use of sediments and soils of different preservation, and identifying variations in environmental parameters even in the case of very short episodes of change in one or more soil formation factors or their individual characteristics, which are shorter in duration than the characteristic time required for the formation of the trait morphological expression. The materials presented in the work and their interpretation show that the information obtained about the soil state and the environment based on the study of soil humus profiles (the characteristics of which can be the results of studying the composition and properties of humus) has not lost its significance and can be used in solving a wide range of soil science problems including monitoring soil conditions, as well as substantiating forecasts of their behavior when changing environmental operating conditions.

Classification of processes that cause land degradation

It is highlighted that the current state of agricultural landscapes is characterized by a significant increase in the area of eroded arable land, which amounts to about 11 million hectares, and eroded agricultural lands — more than 13 million hectares (32.0% of their total area). Modern land-tenancy relations do not contribute to the implementation of measures to protect and increase soil fertility and have a negative effect on their fertility. In the process of using the soil cover, the needs and requirements of the ecobalance are ignored, as a result of which agricultural land is exhaustingly exploited. Soils lose a significant part of humus and such trends continue. Degradation processes are most observed in soils where agricultural techniques were violated, unfounded changes in the hydrological regime of the territory were carried out by irrigation and drainage meliorations, pollution by agrochemicals and industrial emissions occurred, which led to the removal of significant areas of productive land from active agricultural use. It has been established that the process of pollution manifests itself differently and depends on the types of harmful substances, their concentration in the soil environment and toxicity, on the natural properties and characteristics of the soil cover. It is proposed that the suitability of the soils of the contaminated lands should reflect the natural and acquired over time properties of their quality state. The combination of these properties is possible on the basis of establishing the boundaries of contaminated land on soil maps. This will make it possible to determine the area, composition of agricultural production groups and characteristics of the natural state of contaminated soils, humus content, depth of humus profiles, granulometric composition, etc. The established processes that cause various types of degradation require further processing of the parameters of indicators of crisis phenomena. It is emphasized that in the classification of processes leading to the degradation of agricultural lands, it is necessary to pay attention to the economic activity that leads to soil degradation and which is reflected in the dynamics of the structure of cultivated areas; spread of phytoviruses of different taxonomic groups in agricultural plants, weeds, wild plants and soil of different ecological regions of Ukraine; handling of waste of I–IV hazard classes.

Антропогенная трансформация некоторых свойств и состава гажевых серо-коричневых почв Гянджа-Казахской равнины

Gay gray-brown soils are distributed mainly in the foothills of the Lesser Caucasus, on the Ganja-Gazakh plain and in the lower reaches of the Araz basin. They are formed by changing volcanic rocks in hot and dry climates. In the process of erosion and soil formation, pyrite, alunitized and other sulfur-containing rocks turn into gazh, on which gray-brown gazh soils are formed. As a result of human activity, i. e. deep plowing and irrigation, these lands are being converted. It turned out that the transformation of these soils is clearly felt in the thickness of the humus layer, its distribution along the profile, quantity and composition. The thickness of the humus layer increases from 40–45 cm to 100 cm. As a result of the transformation, the length of the humus profile is constantly decreasing. Changes in the composition of humus led to an increase in the content of humic acids. Although the coefficient in the uncultivated area decreased from 1.36 to 0.80, in the irrigated area it changed from 1.70 to 0.93.

Methodological bases for studying erosion processes in the conditions of the Kabardino-Balkarian Republic

The assessment of the ecological state of the soil involves determining the correspondence between the processes in the studied soils and their natural counterparts, which makes it possible to identify the permissible value of a particular factor, incl. agrotechnical, established according to the criterion of compliance with the normal functioning of the natural ecosystem. It is shown that the study of erosion processes in areas with an area that in modern land use is similar to the areas of agricultural land of large farms requires taking into account the quantities (factors) that predetermine both the wash itself and its intensity. It has been established that the rate of increase in the humus profile during the formation of various soils is not the same. The characteristics of the erosion threat of soils are given in accordance with the level of their manifestation for the conditions of Kabardino-Balkaria. As a result of the studies, it was found that the determination of the effect of steepness on soil erosion from slopes in its pure form cannot be performed, since such a process is due to the individual characteristics of an additional set of factors that can only be obtained by studying the relief using different approaches. Therefore, it is necessary to analyze the regional features of the experimental area, which will reduce the errors that arise when using existing mathematical models of water erosion, and at the same time correct them, adapting them to regional conditions.

PHASING FEATURES OF THE SOIL-FORMING PROCESS IN AGROCHERNOZEMS OF WATERSHED PLATEU IN THE CENTRAL PART OF PODILLIA

The development of the paleosoils during the warm stages (thermochrons) of the Pliocene and Pleistocene, being reflected in the structure of soil-loess and red-brown formations of Ukraine, is characterized by a clear regularity. This is manifested in the formation of complex soil layered constructions (pedocomplexes) reflecting the chronological stages of pedogenesis. Agrochernozems of watershed plateu in the central part of Podillia, formed on the loess rocks of the Late Pleistocene age, also show this general regularity of Pliocene-Pleistocene soil formation. Contrasting changes in the physic-geographical conditions of pedolitogenesis in the ancient Holocene (late glacial) and evolutionary trend of soil formation during the following Holocene periods lasting for 10–8 thousand years led to the formation of a two-stage Holocene soil layering on the plakor lands of the region, represented by chernozem-type soils. Morphological signs of staged soil formation are concentrated in one genetic profile, which, along with the sign of anthropization of landscapes and soil formation significantly complicates the detailed identification of soils and their historical and genetic analysis. The early stage of the local soil formation history is recorded in these soils in the form of solid-phase products of soil-forming processes (puppets, soil wormholes, coprolites, moles drains). These relict pedogenic formations are located in the lower part of the soil profile of agrochernozems. In general, in the soil profile of agrochernozems on the watershed plateu in the central part of Podillia the morphologically hidden stages of soil formation are noticeable, which is typical of the first half of the Holocene thermochron. The soil of the initial stage of pedogenesis correlates with the horizon of the mole loess P(h)k and the lower part of the transitional brown-colour horizon Phk or PhI. The humus profile of the plakor agrochernozems has soil characteristics of the early optimal stage, which lasted for 7–8 thousand years from the preboreal to the late subatlantic. There are no pedogenic signs of other stages of development of the pedocomplex. So, modern day soils of this region (agrochernozems) are polygenetic two-stage formations that have not reached the status of full-fledged pedocomplex. Key words: evolution; pedogenesis; agrochernozem; Holocene; stages of soil formation; pedocomplex; Podillіa.

PHYSIC-CHEMICAL PROPERTIES OF TYPICAL CHERNOZEMS OF PRYDNISTERSK PODILLYA

This article analyzes the physic-chemical properties of typical chernozems. According to the methods, a laboratory study was performed. Physic-chemical parameters that are typodiagnostic for subfacial classification division of typical chernozems of the Prydnistersk Podillya are determined. Typical chernozems of the Prydnistersk Podillya are low-humus (2.78–3.98%). With depth, the humus content decreases by an average of 0.2% for every 10 cm, which indicates a uniformly accumulative type of distribution of organic matter in the profile of chernozems. In the same direction, humus reserves are declining. There is a spatial correlation between the humus content and the amount of physical clay in the fine soil.
 Humic acids predominate in the humus to a depth of 90–100 cm (Sgk: Sfk is 1.12–1.78). The general tendency of relative “fulvatization” of the arable layer as a result of its agrotechnical depletion is noticed. In relation to SGC to total organic C, chernozems of the study area are characterized by a high and very high degree of humification of organic matter. It is highest (62–70%) in the soils of the key section “Humentsi”, decreasing to 52–62% and 43–63% in the western direction.
 The humic acids of typical chernozems are dominated by calcium humates (GK-2). The largest number of them (29–35%) is concentrated on the contact boundary of humus and carbonate profiles. The convex nature of the distribution curves of the fraction of 2 humic acids and a sharp decrease in its content deeper than 100 cm, indicates their high migration capacity and the possibility of significant deposition of only a significant excess of calcium carbonates. The intensity of migration processes of the GK-2 fraction decreases in the direction of increasing the stiffness of hydrothermal conditions, due to the pulling of carboxylic acid salts closer to the soil surface, supersaturation of the solution with calcium bicarbonate, and as a consequence, increasing the total alkalinity in the humus horizon.
 The capacity of cation exchange (ECO) of typical chernozems is quite high (29–32 mmol-eq / 100 g of soil) with the dominance of calcium and magnesium cations in the composition of the soil-absorbing complex (GVC). There is a general tendency to increase these indicators in chernozems with low values ​​of SCC of the territory.
 The pH of the aqueous extract of typical chernozems of the Prydnistersk Podillya increases with depth from weakly acidic in the arable horizon to weakly and medium-alkaline within the carbonate profile. The reasons for such changes in the increase with the depth of the concentration of Ca2 + bicarbonates, which in their dissociation leads to an increase in the amount of hydroxyl ion and increase the alkalinity of the soil.
 The carbonate profile of typical chernozems is dominated by migratory forms of carbonate neoplasms - mold, carbonate plaque, veins. The vertical curve of carbonate content has an eluvial-illuvial type of profile structure. The content and reserves of carbonates in the 1.5-meter layer of typical chernozems increase from the west (434–714 t / ha) to the east (979–1847 t / ha).
 Key words: physic-chemical properties, typical chernozems, humic horizon, humic acids, carbonate profile.

Агроэкологическая оценка выщелоченных черноземов разной степени смытости в условиях склоновой катены ЦЧР

Based on the complex investigation of agroecological parameters of leached chernozems with different erosion level in conditions of the slope catena at the Central Chernozemic Region (CChR), the features of agrogenic-erosive transformation of morphogenetic, chemical and physic-chemical properties of the investigated soils at the basic levels of their structural organization are shown – depending on the degree of their erosion. The influence of the processes of surface planar erosion and intra-soil lateral migration on the content and distribution of the most problematic heavy metals (HM) – Pb, Cd is considered. The analysis of the research results has shown that the development of erosion processes in conditions of the slope type of terrain characteristic for the CChR leads to a significant transformation of the main diagnostic indicators of the agroecological state of leached chernozems, primarily to the degradation of their morphogenetic and humus profile. The significant and slope-differentiated influence of erosion processes at the level of soil elementary particles, meso- and macro-levels of the soil structural organization has been established. The processes of erosion and lateral migration change the content and profile distribution of Cd and, especially, Pb in the studied leached chernozems. In the eroded soils, there is an increase in their mobility and accumulation in the subsoil. Keywords: LEACHED CHERNOZEMS, AGROECOLOGICAL STATE, EROSION, TRANSFORMATION AND DEGRADATION, HEAVY METALS, LEAD, CADMIUM

Экологоагрохимическая оценка почв каменной степи под лесным ценозом

A set of parameters of soils under forest belts was studied. The objects of research were old-growth (65–68 yrs) ravine and shelterbelt forest plantations of the Kamennaya Steppe. The results allow assessing the trends of changes in soil characteristics over a long period of time. Key plots of 100×100 m were laid out using a regular sampling grid. The sampling interval is 15–25 m. A positive effect of forest shelterbelts on the properties of chernozems was found. There is an increase in thickness of the humus horizon from 42.3 cm (arable land on the slope) to 72.6±5.1 cm (under forest). The maximum values are typical for chernozems of watershed areas: 59.6±2.4 cm (arable land) and 85.6±3.9 cm (forest belt). Chernozems leached due to the activation of migration processes of carbonates into the underlying soil horizons have the maximum depth of soil effervescence. Chernozems zooturbated due to mechanical transport and mixing of accumulative-carbonate horizon have the lowest depth of soil effervescence. A general trend to decrease the depth of soil effervescence under the forest cenosis was found. The highest humus content is observed in watershed areas: 7.14±0.24 % (arable land) and 8.56±0.18 % (forest belt). A ravine forest belt reduces the risk of erosion processes. A fairly strong humus profile with a high content of organic matter: 7.03±0.27% (under forest) and 6.10±0.10% (on arable land), was possible to preserve on arable lands in the zone of the belt’s influence. The planting of forest belts causes a change in the nature of vegetation. The influence of acidic products of litter decomposition formed soil horizons with a moderately acidic reaction of the environment in the humus layer. Despite the leading position of calcium, an increased content of magnesium was found in the composition of exchange-absorbed cations. Forest belts have become especially important in recent decades due to changing climatic conditions. In the steppe regions of Russia, such plantations are a powerful soil conservation factor that helps stabilize and increase soil fertility. It is necessary to intensify the planting of artificial forest stands in the steppe regions of Russia. For citation: Cheverdin Yu.I., Bespalov V.A., Sautkina M.Yu., Titova T.V. Ecological and Agrochemical Assessment of the Kamennaya Steppe Soils under Forest Cenosis. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 76–91. DOI: 10.37482/0536-1036-2021-5-76-91

Non-typical degraded and regraded humus forms in metal-contaminated areas, or there and back again

Chemically contaminated soils are not included in the European morpho-functional classification of humus systems and forms. However, they differ from the uncontaminated analogs in biological, chemical, and physical features. We investigated the topsoils contaminated by long-term sulfur dioxide and metal emissions from a copper smelter (southern taiga; conifer and deciduous forests; the Middle Urals, Russia). The smelter has been in operation for more than 80 years, but ten years ago, emissions almost ceased which initiated the recovery of adjacent ecosystems. We performed 1,155 humus profile descriptions on 231 sampling plots in highly contaminated, moderately contaminated, and background sites. In the contaminated sites, we found 21 non-typical humus forms that do not fit the European classification. Earthworms’ extinction caused by soil toxicity resulted in a Mull-to-Mor transformation of humus profiles. Recent recolonization of poorly decomposed litter by earthworms and other soil macrodetritivores after emission cessation triggered a Mor-to-Mull shift. Because different topsoil layers react to environmental changes with unequal rates, signs of several stages of humus evolution can be imprinted in one profile. More rapid degradation of organic horizons than organic-mineral ones results in non-typical Mor forms when the thick non-zoogenic OF combines with zoogenic A horizon. Zoogenic O horizons’ heterogeneity due to non-zoogenic inclusions, or inversion of the litter layers sequence, or lagging of A horizon recovery behind the O horizons, represents the discrepancies between non-typical regraded and typical humus forms. Mor-to-Mull recovery can occur with and without passing the Moder forms. In the first path, all intermediate stages at least fitted to one of the known humus systems. In the second path, intermediate humus forms are represented by non-zoogenic OF conjoining highly zoogenic OF and lacking OH horizon (we named such forms Mormull). In both paths, the recovery starts from the upper litter layer and spreads downward, i.e., the signs of the zoogenic activity change in the opposite direction than within the natural Mor profile. We consider the non-typical humus forms as non-equilibrium topsoil states that are ephemeral on the forest succession scale. We described non-typical humus forms in detail, proposed their evolutionary diagram, nomenclature, and preliminary typology, and extended the Humus Index with non-typical forms.

Study of power of humus profile of soil catens of central forest-steppe

The article presents the result of a field study to study the power of humus profiles of gray forest soils and black soils of landowned different terms of agricultural use of soil catens of broad-leaved forest (background) and meadow-steppe sections of the Belgorod region. The work was carried out in the spring-summer period 2018-2019. The object of the study was different-age arable areas with an age of agricultural development of 100 and 160 years, respectively. The surface slope in the sections did not exceed 5-60. It was established that the power of the humus profile under the influence of agricultural processing over a 60-year period decreased by 49 cm, moreover, on the slopes of the northern exposition, this indicator is more pronounced (33 cm) than on the slopes of the southern exposition (16 cm). It can be noted that with an increase in the age of agricultural use on the slopes of the northern and southern expositions, the largest thickness of the humus horizon is observed on abnormal soils (72 and 65 cm, respectively). Within the background catens, the soil cover is homogeneous; a second humus horizon was observed in each of the studied sections.

The Evolution of the Chernozems in the Central Part of Russia and their Complex Analysis in Modern Conditions

An increasing anthropogenic impact on soils leads to qualitative and quantitative changes in chernozems, the richest soils on Earth. In this regard, the understanding of modern soil-forming processes is undoubtedly relevant because it will allow predicting the future state of not only soils, but also nature as a whole. The methodology for studying the evolution of chernozems is based on a process-factor analysis of genetically conjugated and agrogenic series of chernozems of different taxonomic levels. The objects of the study were system complexes of soil series, including subtypes of virgin, arable, and irrigated chernozems in the central regions of Russia. The data obtained made it possible to identify patterns of variation in the composition and properties of virgin chernozems in a genetically conjugated series at a subtype level and in the series virgin land – arable land – irrigated arable land; we also detected the processes and factors that determine the nature and direction of changes in the composition and properties of chernozems in the studied series and determined the direction of anthropogenic evolution of chernozems. The main provisions of the work conceptually develop the theory of the chernozem-forming process and serve as a theoretical basis for the development of models for the formation of the chernozem profile. Established quantitative and qualitative indicators of humus profiles of chernozems are important diagnostic features in the classification of these soils. The nature and direction of the chernozem evolution disclosed in the work can serve as the basis for long-term forecasting of the state of these soils and the development of a set of measures for their rational use and protection.’’

Dynamics of humus forms and soil characteristics along a forest altitudinal gradient in Hyrcanian forest

Humus forms are good indicators of environmental conditions and thus important in forest ecological processes. Altitudinal gradients are considered as natural laboratory for evaluating soil ecological processes and humus form distribution. The objective of this study was to evaluate the macromorphology of humus forms along an altitudinal gradient (0-2000 m a.s.l.) covered with plain forest, mixed and pure forests and forest-grassland ecotone, in Alborz Mountains in northern Iran. In total, 225 humus profiles were evaluated. Forest stand variables including tree density, basal area, crown density, and height, forest floor and soil physico-chemical properties along with biological features were measured. We found that altitudinal gradients influence both humus forms distribution and soil properties but with different mechanisms. While soil properties (i.e., temperature, pH, CaCO3, soil N content, soil C/N and microbial biomass N) were significantly correlated with altitude, the forest floor properties were more influenced by tree species composition. Particularly, the abundance of Mull was decreased in plain mixed forests compared to mountain pure forests, whereas the frequency of Amphi was increased. Moreover, Oligomull and Leptoamphi were abundant in mixed beech forests, while Eumacroamphi, Eumesoamphi and Pachyamphi were only observed in pure beech forests. Such a distribution influenced soil fertility where higher values of nitrogen (N), microbial biomass nitrogen (MBN) and pH were observed at lower altitudes under mixed forests compared to pure forests at higher altitudes.

Study of thickness of humus profiles of gray forest and chernozem soils of different terms of agricultural use in landscape shrubs of the central forest-steppe

The article presents the results of a field study of the thickness of the humus profiles of gray forest soils and podzolized chernozems of dif-ferent terms of agricultural use of soil catens of broad-leaved-forest (background) and meadow-steppe areas of the Belgorod region. The work was carried out in the spring and summer period 2018-2019. The objects of the study were different-aged arable plots with the age of agricultural development of 100 and 160 years, respectively. The steepness of the surface on the plots did not exceed 5-60. It is established that the thickness of humus profile under the influence of agricultural cultivation during 60 years has decreased by 49 cm, at that on the slopes of northern exposition this index is more expressed (33 cm) than on the slopes of southern exposition (16 cm). It is possible, to note, that with increase of age of agricultural use on slopes of northern and southern expositions the greatest thickness of humus horizon is observed on anomalous soils (72 and 65 sm accordingly). Within the background catens the soil cover is homogeneous, the second humus horizon was observed in each of the studied transects.

Variations in the Properties of Chernozems and Paleoenvironmental Conditions in the North Caucasus in the 4th Millennium BC according to the Results of the Study of Essentuksky 1 Kurgan

A short-term chronosequence of paleosols buried under different structures in the big Essentuksky 1 kurgan (North Caucasus) was studied. The kurgan was constructed in the second quarter of the 4th millennium BC (the Maikop culture). According to archaeological data, the kurgan construction continued for several decades. During this time, the morphological pattern and physicochemical properties of soils changed: the thickness of the humus profile and the content of organic carbon decreased, the contents of gypsum and carbonates increased, the zone of their accumulation shifted upwards the soil profile, and the transformation of carbonate pedofeatures took place. The most “arid” properties were found in the soil buried last in the studied chronosequence: the humus horizon of this soil is the lightest in color and has the lowest organic carbon content; the soil profile is most enriched in carbonates, which is manifested both at the macro- and microlevels of observation; the highest content of exchangeable sodium and magnesium is noted in the composition of exchangeable bases; a decrease in the magnetic susceptibility and a maximum in the gypsum content are observed in the second meter of the soil profile. During the construction of the kurgan, Calcic Chernozems (Loamic, Pachic) evolved into Haplic Calcisols (Loamic). A palynological analysis revealed a decrease in the area of forest vegetation and an increase in the share of herbaceous vegetation in the spectrum, including the appearance of steppe species and xerophytes in the region over the studied time. The climate of the studied time interval (the early stage of the Maikop culture in the North Caucasus) was arid and warmer than that at present.

SOILS OF CHERNEVAYA TAIGA OF WESTERN SIBERIA — MORPHOLOGY, AGROCHEMICAL FEATURES, MICROBIOME

The soils of Chernevaya taiga are unique in terms of high fertility that was formed not as a result of agricultural practices, but due to the combination of a huge volume of biotic and abiotic resources. This area was able to preserve its “pre-agricultural” level of fertility overtime by avoiding the negative consequences of long-standing agricultural usage. Comprehensive analysis of all related properties within the framework of a metagenomic study and identification of microbial drivers of fertility can become the basis for innovative technologies aimed to increase the productivity of soils and crops. In this work, for the first time were obtained data on the taxonomic structure and features of the of the microbiota of soils in the Chernevaya taiga and identified taxa, the number of which significantly increases with the transition from the background zonal soil to the soil of Chernevaya taiga. Analysis of soil samples collected during expeditionary surveys in 2019 showed that the soils in the Western Siberia (Novosibirsk, Tomsk, Kemerovo, and Altai regions) portion of the Chernevaya taiga are texture-differentiated dark gray soils (clay loam and silt clay varieties confined to the deluvial cover of the Holocene and Late Pleistocene) that were formed as a result of a unique combination of geogenic and bioclimatic conditions. These soils are not affected by the permafrost in winter timers and are supplied with enough moisture to precipitate rapid mineralization of litter material and the fixation of mineral nutrients in the upper humus layer of the soil profile. The accumulation of nutrients is an essential property of the soils of the Chernevaya taiga associated with the phenomenon of gigantism and extremely high levels of plant productivity. The soils of Chernevaya taiga contain the maximum amount of carbon in organic compounds compared with soils of oligotrophic habitats (9.85% versus 2.74%). The levels of actual soil fertility in the soils of the Chernevaya taiga are several times higher than in the soils of adjacent biotopes (the maximum content of the exchange forms of phosphorus and potassium is 702 and 470 mg/kg), which, when compared to oligotrophic forests, are poor in terms of agrochemical fertility (the maximum content of the exchange forms of phosphorus and potassium is 113 and 18 mg/kg), do not have a pronounced humus profile and are either gray-humus (Umbrisol) or Podzol types according to substantive-profile classification of Russian soils. The diversity of microorganisms in the studied soils varies depending on the trophic regime of the ecosystem. The soils of the Chernevaya taiga are characterized by an increased diversity of the microbial community (estimated by the Shannon index), as well as by presence of phyla Nitrospirae and Thaumarchaeota, that, however, are not dominant. Phyla Proteobacteria, Verrucomicrobia, Actinobacteria, Acidobacteria, Planctomycetes, Firmicutes appeared to be common for all studied soils.

Physicochemical Features of Soil-Forming Processes in Conditions of Technogenic Load

The investigations were made in the zone of influence of the Irkutsk UC RUSAL aluminum smelter. Soil cover on this territory is represented by gray medium and light loamy soils, with a small thickness of the humus profile. The stoichiometric formulas of solid mineral solutions, humic substances and components of soil solutions formed under the influence of technogenic load are calculated by thermodynamic modeling methods using the Selector software package. The readily soluble forms of existence of the components of gas and dust emissions and solid phases accumulating in soils were determined. The most common condensed components are fluorapatite and fluorite (CaF2 and A1F3). Complex ions (Al(OH)2F0, A1F2+ and A1F4–) are dominant in the aqueous solution, a high concentration of which is due to the presence of readily soluble compounds (NaF, KF and NH4F) in emissions. In terms of physicochemical models it was determined that 70–90% of the total amount of F and Na arriving at the day surface can be fixed in soils exposed to the Irkutsk aluminum smelter. Therefore, in spite of high solubility, these pollutants are sorbed by soil. Technogenic transformation is accompanied by a slight increase in pH (from 5.6 to 5.75), an increase of the amount of mixed-layer aluminosilicates: smectites and chlorites (from 43 to 51%), and by a decrease in muscovite content (from 14 to 12%) and humus (from 3.42 to 3.32%). Simulation modeling was used to assess changes in the phase-component composition of soils under the influence of gas and dust emissions from aluminum production. It was found that in gray soils experiencing the anthropogenic impact, the composition of the soil mineral matrix as well as of organic matter changes. A dominant main role is played by the process of acid hydrolysis of alumosilicates whose agents are represented by decomposition products of amorphized fluorine-containing pollutants. The most important feature of this process is a change in composition of clay minerals and humus. An increase in fluorine and chlorine contents in soils leads to an increase of the amount of methane in the gas phase, rather than increasing solubility of organic substances.

Organic matter transformation in post-agrogenic soils of the Middle Taiga zone

Objective. The purpose is to study the organic matter transformation in Podzols from the middle taiga zone.Methods. The study materials are arable lands from the central regions of the Komi Republic. These lands are not agriculturally used since the early 90-ies of the former century. The soil analyses are done according to the common methods.Results. The study allows for the humus profile structure of Podzols along with the following successive stages as meadow idle land young forest dwarf shrub-green moss spruce forest. It also describes the mechanisms of post-agrogenic humus transformation in agricultural sod Podzols due to the self­ restoring succession.Conclusion. Initially, the post-agrogenic soils normally repeat agrozems by characteristics. The upper soil part forms a thin grey-humus (sod) horizon. It contains large amounts of humus, exchangeable cations, and nutrition elements. The specific synthesis and destruction processes of humic substances at the meadow idle land stage change the qualitative humus composition. In contrast with arable lands, the humus composition is dominated with fulvic acids as being best appropriate to the concerned bioclimatic zone. The humuc-fulvic humus composition holds only in the upper old-arable soil part of the meadow idle land. The appearance of pioneer tree species increases the dominating position of FAs and the Cha/Cfa ratio resembles that for forest soil. The organic matter is poor in nitrogen compounds, especially at the young forest stage. By the C/N ratio, the post-agrogenic soils also gradually get close to naturally formed soils under virgin forest.