Fractional composition of humus in leached chernozems and gleyed podzolized chernozem-like soils of the northern forest-steppe zone

The composition of humus in leached chernozems differs from that in gleyed podzolized chernozem-like soils in the northern forest-steppe zone of European Russia. Leached chernozems have the fulvate-humate humus. Gleyed podzolized chernozem-like soils have the humate-fulvate humus. A more aggressive composition of humus in the latter soils is caused by their overwetting and the development of gley processes under conditions of a stagnant-percolative soil water regime.     

Specific features of organic matter in urban soils of Rostov-on-Don

Data on the fractional and group composition of humus in urban soils of Rostov-on-Don are discussed. We have compared the humus profiles of chernozems under tree plantations and those buried under anthropogenic deposits (including sealed chernozems under asphalt). It is shown that the type of humus in these soils remains stable despite a decrease in its total content after the long-term burial under asphalt. Under the impact of the trees, the organic matter of the chernozems acquired some features typical of gray forest soils, i.e., the humate-fulvate type of humus in the humus horizon and the sharp drop in the humus content down the soil profile.     

Comparative assessment of the biological tolerance of chernozems in the south of Russia towards contamination with Cr, Cu, Ni, and Pb in a model experiment

The biological properties of chernozems in the south of Russia worsen under the impact of contamination with Cr, Cu, Ni, and Pb compounds. The tolerance of chernozems towards contamination decreases in the following sequence: ordinary chernozems > typical chernozems > southern chernozems > leached vertic chernozems. This sequence is specified by the soil reaction and the organic matter content. The high humus content determines the high buffer capacity of chernozems towards contamination with chromium, whereas the high pH values ensure the soil tolerance towards contamination with copper, nickel, and lead. With respect to their adverse effect on the biological properties of the chernozems, the studied heavy metals can be arranged into the following sequence: CrO₃ > CuO > PbO ≥ NiO.     

The Impact of Artificial Forest Plantations on Mountain-Meadow Soils of Crimea

A significant change in the properties of mountainous meadow soils of the Ai-Petri Plateau has taken place under the impact of artificial plantations of pine, birch, and larch created in the Crimean highlands in the middle of the 20th century. In comparison with the soils under meadow vegetation, the soils under forest vegetation are characterized by an increased content of large aggregates, a decrease in the humus content, and an increase in the soil acidity and in the iron content of the organomineral compounds. The most dramatic changes in the structural state of the soils are observed under the plantations of pine. The changes in the acidity and the iron content are most pronounced under larch stands. The decrease in the humus content is observed under all tree species. Thus, in the soil layer of 0–10 cm under pine, birch, and larch stands, the content of C_org is 1.2, 1.3, and 1.4 times lower, respectively, than that in the soil under meadow vegetation.     

Changes in the content and quality of humus in leached chernozems of the Trans-Ural forest-steppe zone under the impact of their agricultural use

The results of long-term studies of changes in the content and fractional-group composition of humus in leached chernozems (Luvic Voronic Chernozems, WRB 2006) of the Trans-Ural forest-steppe since the beginning of their plowing are considered. These soils are characterized by the high humus pool (up to 500 t/ha in the virgin state and up to 430 t/ha in the plowed state) and the high degree of the organic matter humification. Humus is of the fulvate–humate type in the upper 30 cm and of the humate–fulvate type in the deeper layers. From 1968 to 2006, the total pool of humus in the 1-m-deep soil layer of the plowed chernozems decreased by 8.5% in comparison with the initial virgin soils. The rate of dehumification reached 1.0–1.4 t/ha per year. The long-term plowing of leached chernozems also led to a smaller content of nitrogen in the organic matter (the C/N ratio increased from 11.5 to 13.6). The relative content of free humic acids (HA-1) and humic acids bound to clay minerals (HA-3) increased, whereas the content of calcium humates (HA-2) decreased. The composition of fulvic acids in the plow horizon was characterized by the rise in the content of aggressive (FA-1a) and mobile (FA-1) fractions, while the amount of fulvates bound to calcium (FA-2) decreased.     

Changes in the properties of leached chernozems of the northern forest-steppe in the middle Ob River basin caused by different agricultural uses

The trends of the soil-forming process and the changes in the main physicochemical properties of leached chernozems under different phytocenoses (virgin land, cereal-row crop rotation, and sown perennial grasses (Galega + Bromopsis)) were studied. In the cereal-row crop agrocenoses, as compared to the virgin land, the thickness of the humus horizon increased, and the depth of effervescence remained the same. The reaction of the leached chernozems in the phytocenoses did not change, and the sum of exchangeable bases increased in the following sequence: sown perennial grasses < cropland = virgin land. The humus content and its reserves in the 0- to 20-cm soil layer of all the agrophytocenoses were almost the same, and the total nitrogen content decreased in the following sequence: virgin land = cropland > perennial grasses. On the contrary, the total phosphorus content, its mobility, the phosphorus capacity and reserves, and the sum of the mineral phosphates increased in the same order. The highest content of exchangeable potassium was found in the soils of the virgin land and the lowest one, in the soils of the cereal-row crop agrocenosis. The perennial grasses consumed the greatest amounts of potassium and nitrogen and the spring wheat of the cereal-row crop rotation, those of nitrogen. The removal of nitrogen was 1.6–1.8 and 2.3 times greater than the losses of phosphorus and potassium, respectively.     

Multiple assessment of the soil cover in the area of natural monuments Tra-Tau and Yurak-Tau monadnocks under conditions of technogenic loads

The soil cover of Tra-Tau and Yurak-Tau shikhans (monadnocks) has been examined. Leached and typical medium-deep chernozems are developed on colluvial fans on the footslopes and on the lower parts of slopes, whereas typical calcareous thin slightly and moderately gravelly chernozems are developed on the upper and medium parts of slopes. The leached and typical chernozems of the footslopes correspond to zonal soils of the adjacent plain areas, though they have some specific features related to the local topographic conditions. These soils are somewhat thinner than plain chernozems and are characterized by the perfect granular water-stable structure, the high content of humus of the humate type, the high content of exchangeable cations, strong acid-base buffering, and high enzymatic activity. These features predetermine their high tolerance towards technogenic impacts. The concentrations of highly hazardous substances of the first toxicity class (mercury, arsenic, lead, and cadmium) and of moderately hazardous substances of the second toxicity class (copper, zinc, and nickel), as well as the concentrations of low-hazardous elements (manganese and iron) in these soils do not exceed provisional maximum permissible concentrations of these substances in soils irrespectively of the slope aspect. No changes in the physicochemical and biological properties of the soils under the impact of technogenic loads from Sterlitamak industrial center have been identified.     

Transformation of soil organic matter in leached chernozems under minimized treatment in the forest-steppe of West Siberia

Changes in the contents of total organic carbon and the carbon of easily mineralizable fractions of organic matter (labile humus, detritus, and mortmass) in the layers of 0–10, 10–25, and 0–25 cm were studied in leached chernozems ((Luvic Chernozems (Loamic, Aric)) subjected to deep plowing and surface tillage for nine years. In the layer of 0–25 cm, the content of Corg did not show significant difference between these two treatments and comprised 3.68–3.92% in the case of deep plowing and 3.63–4.08% in the case of surface tillage. Tillage practices greatly affected the distribution of easily mineralizable fractions of organic matter in the layers of 0–10 and 10–25 cm, though the difference between two treatments for the entire layer (0–25 cm) was insignificant. Surface tillage resulted in the increase in the contents of mortmass (by 59%), detritus (by 32%), and labile humus (by 8%) in the layer of 0–10 cm in comparison with deep plowing. At the same time, the contents of these fractions in the layer of 10–25 cm in the surface tillage treatment decreased by 67, 46, and 3%, respectively. The estimate of the nitrogen-mineralizing capacity made according to the data on the uptake of soil nitrogen by oat plants in a special greenhouse experiment confirmed the observed regularities of the redistribution of easily mineralizable organic matter fractions by the soil layers. In case of surface tillage, it increased by 23% in the layer of 0–10 cm; for the layer of 0–25 cm, no significant differences in the uptake of nitrogen by oat plants were found for the two studied treatments.     

The impact of Buzuluk pine stand on the surrounding landscapes and soil properties

The impact of Buzuluk pine stand on the soil formation and soil properties within the surrounding territory has been studied. It is shown that this pine stand located in the typical steppe within the subzone of ordinary chernozems creates a specific forest-controlled mesoclimate and affects the soil forming conditions on the surrounding territories. As a result, areas of typical chernozems have formed around the stand; the width of this zone extends up to 20 km. Thus, a local ecologically driven inversion of soil zones is developed in the study area: forest-steppe landscapes with typical chernozems border the zone of dry steppes with southern chernozems.     

Impact of weather anomalies in recent decades on the water regime of typical chernozems of the reserved steppe area in Kursk oblast

The analysis of long-term weather records and data on the water budget in a 3-m-deep layer of typical chernozems in the reserved steppe area has shown considerable changes in the soil hydrological regime under the impact of climatic fluctuations. In the past 34 years, the warm season has become more humid and the cold season has become warmer in comparison with the climatic norm. These changes have been accompanied by the settling of trees and shrubs on the reserved steppe territory; more frequent cases of water percolation throughout the entire profile of chernozems owing to the increased accumulation of water reserves in the fall, winter, and spring seasons; less active evapotranspiration of soil water during the growing season; and the smaller deficit of soil water in the fall. In general, the chernozems have become better moistened, which has led to certain changes in their genetic features.     

Systems of solutions,minerals, and humic substances in soils

The equilibrium composition of solutions, minerals, and humic substances of the humus-clay plasma from the humus horizon of a leached chernozem was calculated using the method of computerized physicochemical simulation based on Gibbs’ principle of minimum free energy in the equilibrium state of the system. It was shown that the plasma from the humus horizons of chernozems and soddy-deeply podzolic soil mainly consists of oxides, hydroxides, humic substances, kaolinite, and 2: 1 illite-smectite minerals. The stoichiometry of the humic substances corresponds to calcium-saturated humus acids with appreciable contents of iron and aluminum. The crystallochemical composition of the 2: 1 layered minerals classifies them among ferruginated mixed-layered illite-montmorillonites. Simulation at an increased concentration of carbon dioxide indicated the degradation of the humus-clay plasma in a leached chernozem under extensive soil use, which can be restored by application of potassium at rates 1-to ?1.5-fold its removal.     

Genesis,hydrology, and properties of soils in mesodepressions waterlogged by surface water in the northern Ryazan forest-steppe

On the interfluves and in small depressions of the Ryazan forest-steppe, under periodic stagnation of surface water, acid chernozem-like soils with a relatively thick humus horizon, podzolic horizons, and marble-colored gleyed B1 and B2 horizons are formed. The eluvial horizons of these soils contain Mn-Fe nodules, and dark humus coatings occur in the illuvial horizons. In the spring, the eluvial horizons of these soils are excessively moistened and gravitational water stagnates on the soil surface for 3–4 weeks. The formation of the acid light-colored eluvial horizons of the soils on leached rocks is related to gleying under the conditions of the stagnant-percolative regime. Their total thickness is 15–25 cm and more. According to the properties of their solid phase, these horizons are similar to the podzolic horizons of soddy-podzolic gleyed soils. These soils have not been represented in the classification systems of soils of the USSR and Russia. Based on the principles of the substantial-genetic classification, one of the authors of this article [9] referred this soil to gleyed podzolic chernozem-like soils, thus, considering it as an individual genetic soil type. The gleyed podzolic chernozem-like soils differ from the leached chernozems by their low productivity and difficulty of tillage. In humid and moderately moist years, the death of crops or a reduction in yield are probable because of the excess of moisture.     

Humusveränderungen nach Einbringung von Buche und Eiche in Kiefernreinbestände

Humus changes after introduction of beech and oak into Scots‐pine monocultures Medium‐ and long‐term (16 to 83 years) effects of an introduction of broadleaf‐tree species (Common beech [Fagus sylvatica] and European‐Sessile Oak [Quercus robur/petraea]) into mature Scots‐pine (Pinus sylvestris) stands on humus type and chemical properties of the Oh layer (pH value, base saturation, C : N ratio) were studied on 16 sites in Bavaria/Germany. The sites investigated covered a large range with respect to elevation, climate, parent material, and soil type. At most sites, the introduction of beech resulted in a significant change of the soil humus type from biologically inactive humus types to more active ones. The strongest changes occurred on the poorest sites, where forest floors under pure pine were particularly biologically inactive. In most cases, the changes in humus type were accompanied by significant increases in the pH value and the base saturation and significant decreases in the C : N ratio of the Oh layer. However, the latter effect was not noticed at most sites with initial C : N ratios higher than 30. In contrast to beech, the introduction of oak did not result in a systematic change of the humus type, the pH value, or the base saturation of the Oh layer. In spite of the considerable change of humus type under beech to biologically more active types, the introduction of broadleaf trees did not result in a systematic change of the thickness or the mass of the forest floor. A decrease in the mass of the Of layer was compensated by an increase of the Oh‐layer mass. All studied sites considered, the introduction of broadleaf trees into Scots‐pine monocultures resulted on average in an 8% decrease of the total amount of organic carbon (C_org) in the forest floor; the C_org amount in the uppermost 10 cm mineral soil increased by 9%. At 35% of all investigated sites, broadleaf tree introduction resulted in increased (+5% to +18%) topsoil (forest floor and uppermost 10 cm mineral soil) C_org stocks. At 30% of the sites, the stock changes were less than ±5%, and on 35% of all sites, soil C_org stocks decreased by –5% to –36%. The average change in the topsoil C_org stock for all studied sites was –5%. The introduction of beech into Scots‐pine monocultures resulted in an ecologically desired translocation of soil organic matter from the forest floor into the mineral topsoil. It is an effective and sustainable silvicultural measure to restore and revitalize acidified, nutrient‐depleted topsoils with biologically inactive humus types.     

Soils of paleocryogenic hummocky-hollow landscapes in the southern Baikal region

The features of ancient periglacial phenomena are widespread in landscapes lying beyond the modern permafrost zone. The specificity of the paleogeographic conditions in the south of the Baikal region resulted in the formation of paleocryogenic landscapes with hummocky-hollow landforms. The paleocryogenic mounds (hummocks) are of rounded or elongated shape, their height is up to 2–3 m, and their width is up to 20–25 m. They are separated by microlows (hollows). This paleocryogenic microtopography favors the differentiation of the pedogenesis on the mounds and in the hollows, so the soil cover pattern becomes more complicated. It is composed of polychronous soils organized in complexes with cyclic patterns. Light gray and gray forest soils and leached and ordinary chernozems are developed on the mounds; gray and dark gray forest soils and chernozems with buried horizons are developed in the hollows. The soils of the paleocryogenic complexes differ from one another in their morphology, physical and chemical properties, elemental composition, and humus composition. For the first time, radiocarbon dates have been obtained for the surface and buried humus horizons in the hollows. The results prove the heterochronous nature of the soils of the paleocryogenic landscapes in the south of the Baikal region.     

Monitoring of the humus status of soils of the Ingulets irrigation system

The results of long-term studies (1957–2007) of the changes in the morphology of soil profiles and in the reserves and fractional composition of the humus in the soils of the Ingulets irrigation system are discussed. After 50 years of irrigation, the boundaries of the genetic horizons shifted downward by 15–30 cm. The redistribution of the humus took place: its content decreased to a low level in the plow layer of the irrigated and rainfed soils and significantly increased in the layer of 60–100 cm so that the reserves of humus in the layer of 0–100 cm somewhat increased and corresponded to a moderate level. The distribution of humus in the soil profiles was characterized by the gradual lowering down the soil profile. The concentration of nitrogen in the humus of the irrigated southern chernozems was very low. The degree of humification of the soil organic matter was high. The humus was of the humate type in the upper horizons and of the fulvate-humate type in the lower horizons.     

Effect of crop residues on the organic matter composition of a leached chernozem in the Western Siberian forest-steppe

In leached chernozems used in crop rotations with different amounts of plant residues for nine years, the following parameters have been determined: the changes in the contents of the total carbon and carbon and nitrogen from the readily hydrolyzable components of the soil organic matter: the labile humus, detritus, and mortmass. No significant differences in the content of C_org in the soil among the crop rotations have been found. The different inputs of plant residues have significantly affected the contents of carbon and nitrogen in the readily mineralizable soil organic matter. The decrease in the mean annual input of the aboveground plant residues to the soil from 1.5 to 0.2 t C/ha resulted in the reduction of the carbon and nitrogen contents in the soil by 19–25% for the labile humus, 24–28% for the detritus, and 33–36% for the mortmass. The labile humus formed the largest fraction (3890 mg of C/kg soil or 10.3% of C_org on the average for the crop rotations); the fractions of the detritus (1546 mg C/kg soil or 10.3%) and mortmass (627 mg C/kg soil or 1.7% of C_org) were the next.     

Anthropogenic evolution of dark gray forest-steppe soils in the southern part of the Central Russian Upland

A sequence of dark gray forest soils developing under a virgin broadleaved forest and under croplands used for 100 and 150 years was studied in the southern part of the forest-steppe zone on the Central Russian Upland. The application of multiple study methods for these objects made it possible to trace the evolutionary changes in the soil properties during the 150-year-long period of regular plowing. Several important trends in the soil development under the impact of the cultivation were revealed: (a) an increase in the thickness of the humus layer (according to the measurements at 20 points for each of the objects), (b) an increase in the amount of mole tunnels, (c) a decrease in the coefficient of the textural differentiation of the soil profile (with respect to the clay content), (d) an increase in the contents and reserves of the major nutrients upon a stable pool of humus in the upper meter, and (e) some alkalization and carbonization of the profile. Powdery accumulations of carbonates and whitish calcareous coatings on the faces of prismatic peds appeared at a depth of more than 130 cm. The plowed soils contained thin deep fissures, the surface of which was covered by dark-colored clayey-humus coatings at the depth of 50–110 cm. The radiocarbon age of the humus in these coatings was 500–1000 years younger than the age of the humus in the soil mass between the fissures. This set of features attests to the evolution of the plowed dark gray forest soils into chernozems under the impact of plowing.     

Changes in the physical properties of soils in the Kamennaya Steppe under the impact of shelterbelts

The physical properties of ordinary chernozems and meadow-chernozemic soils under different land management practices (maple, larch, birch, and pine sections of the shelterbelts; continuous (since 1959) fallow; and arable field (since 1952)) were studied in the Kamennaya Steppe. The soils had favorable physicochemical properties, light clayey texture, and high microaggregation independently from the type of land management. The long-term impact of the shelterbelts improved the soil structure in the upper part of the humus horizon: the content of agronomically valuable aggregates increased, the content of coarse aggregates (>10 mm) decreased, the aggregation coefficient increased by 3.7–4.3 times, and the water stability of the aggregates became by 8–12% higher. The soils under the shelterbelts were characterized by minimum values of the bulk density and solid phase density and by maximum values of the total, active, and air porosities. At the same time, no considerable differences between water reserves in the studied range of soils were detected. The ratio of the optimum productive water range to the active (productive) water range (OPWR/AWR) within the upper soil meter varied from 0.42–0.44 to 0.45–0.54. This points to changes in the character of perched water: the content of intra-aggregate capillary-perched water decreases, and content of film perched water increases down the soil profile.     

Humus status and distribution of the underground phytomass in eroded chernozems of the Cis-Salair region

It is shown that humus loss may reach 1.7 t/ha per year as a result of plowing of leached chernozems and erosion development. Distribution of underground phytomass in uneroded and eroded chernozems and slightly aggraded meadow-chernozemic soils of dissected areas in the Cis-Salair region is analyzed. It is shown that an increase in the degree of soil erosion is accompanied by a decrease in the total phytomass reserves, whereas the average depth of the root zone increases.     

Assessment of biological activity in agrogenic and natural chernozems of Kabardino-Balkaria

Parameters of biological activity (humus and microbial biomass reserves, potential intensity of the CO₂ emission, and enzyme activity) have been determined in arable and natural chernozems on the plains of Kabardino-Balkaria as a part of the system for the ecological assessment of the state of the soil cover. Integral parameters of the eco-biological state of studied soils have been calculated on the basis of obtained data, and the level of changes in their total biological activity has been determined. A statistically significant decrease of the values of all the considered biological properties under the impact of tillage has been found. The data of two-way ANOVA suggest a stronger influence of agricultural management in comparison with genetic features of chernozems at the level of subtype. Differential approach is insufficient for evaluating the total level of soil biological activity, because there are many biological properties of soil, and the degrees of their changes in agrogenic soils are different. An integral approach has been used; it integrates the obtained data into a single integral assessment parameter. In arable soils, this integral parameter decreases by 39–46% and makes it possible to assess the degree of disturbance of the ecological functions of soils and their capacity for self-restoration.