Humus pedorelicts in soddy calcareous soils of the Vyatka-Kama interfluve

A plowed soddy-calcareous soil with relict features developed from Permian clayey calcareous soil was described for the first time in the area of soddy-podzolic and gray forest soils of mixed forests in the middle and lower riches of the Vyatka River. This soil was thoroughly examined by physical, chemical, biochemical, radioisotope, and physicochemical methods. A second humus horizon enriched in calcium humates was described in this soil. Its age was determined at about 7200 yrs. This horizon attests to the presence of in situ postcarbonate pedorelicts in the soil cover of the eastern Russian Plain. The studied soil was formed during the Atlantic optimum of the Holocene under conditions more favorable to humus-accumulative processes as compared with those during the subsequent period. The soil evolution in the second part of the Holocene was characterized by the partial preservation of the previously formed features with the development of eluviation features under colder and wetter climatic conditions. This intrazonal soil is genetically close to gray forest and soddy-podzolic soils with residual second humus horizons that are widespread on the Vyatka-Kama interfluve. The evolution of the latter soils in the second part of the Holocene has been driven by eluviation processes that gradually eliminate the features of the second humus horizon from the soil profiles.     

Water budget items and temperature regime of postagrogenic soddy-podzolic soils of Moscow region and their effect on the soil properties

The postagrogenic transformation of the plow horizon of soddy-podzolic soils under a mown meadow and an artificially planted dense spruce stand has been studied in relation to the microclimatic specificity, water budgets, and soil temperature regimes in the compared cenoses. Over 20 years, a considerable part of precipitation reaching the soil surface under the meadow cenosis has been discharged with the surface runoff and subsurface lateral water flows. The soil warming in summer has been considerable, and the soil freezing in winter has been relatively weak. As a result, a gray humus horizon with well-shaped fine granular and coprolitic structure has been formed within the body of the former plow layer. Under the spruce stand, a larger part of atmospheric moisture has been infiltrated into the soil. The microclimatic conditions under the spruce stand have been more humid and colder. As a result, a thinner humus horizon with a considerable admixture of weakly decomposed plant debris has been formed in the upper part of the former plow layer. Below, a newly formed horizon with a specific thin platy (schlieren) structure ha been developed. The morphology of this horizon resembles the morphology of the eluvial horizon in virgin soddy-podzolic soils.     

Natural and Anthropogenic Changes in the Soils and Environment of the Moskva River Floodplain in the Holocene: Pedogenic,Palynological, and Anthracological Evidences

Several series of well-developed paleosols of different ages have been examined on the Moskva River floodplain. In the beginning of the Holocene, forest-steppe biomes were widespread in this area, and dark-humus (Black) soils with stable humate humus and without features of textural differentiation predominated on the floodplain. The presence of meadow-steppe vegetation communities during this period is confirmed by the results of palynological and anthracological analyses. The lower paleosol in section RANIS 2 is represented by the deep humus horizon with ¹⁴C dates from 5500 to 8400 BP and the carbonate-accumulative horizon; it also contains large and deep tunnels of burrowing animals typical of chernozems. Wood charcoal is absent, and pollen of Artemisia and Chenopodium species predominates. Paleosols of the second half of the Holocene are represented by gray-humus and soddy-podzolic soils (Luvisols). In these soils and in the alluvial sediments, beginning from the Subboreal period, pollen of trees predominates; there are abundant charcoal of spruce and burnt spruce needles. In that time, forest-steppe and broadleaved forest biomes on the floodplain were replaced by southern taiga biomes. The second half of the Holocene is also specified by the human impacts on the local landscapes. Palynological and anthracological data attest to the large-scale burning of forests for pastures in the Bronze Age and, later, for cropland. The paleosol of the Iron Age is enriched in humus. It contains tunnels of burrowing animals related to the stage of anthropogenic meadows. It also contains pyrogenic calcite. The recent centuries have been characterized by extremely high floods triggered by the human activity; they have been accompanied by the fast accumulation of coarse-textured alluvial sediments and the formation of weakly developed alluvial soils.     

Soil evolution on the low terraces of Lake Nero

The soil evolution in the depression of Lake Nero was driven by climate changes in the Holocene and by the history of the relief’s development in this region. In the Alleröd period, dark-colored soils were formed; in the Late Dryas period, they were cryoturbated and covered by colluvial deposits from the adjacent slopes. These specific paleosols are found on relatively high ancient surfaces. In the Early and Middle Holocene (10000–3700 BP), dark-colored horizons of soils with high stability of the organic matter were formed. The properties of humus in these soils are close to the properties of humus in forest-steppe soils. In the past 3500–3700 years, under conditions of some cooling and humidization of the climate with the development of taiga pedogenesis, these soils have evolved into soddy-podzolic soils. Their dark-colored horizons have degraded, though their lower parts are partly preserved in many places as the second humus horizons, the most distinctive feature of the soil polygenesis in the studied region. The soils of the low terrace (100–103 m a.s.l.) are younger than the soils of the higher and more ancient surfaces. Their evolution followed the same stages, though the Alleröd paleosols have not been found on this surface. In the coastal zone, at the heights below 97 m a.s.l., the soil formation began later, about 7000 years ago. Afterwards, the soils of this surface were subjected to the influence of fluctuations in the lake’s level. During the regression phase (7000–3500 BP), which corresponded to the dark-colored pedogenesis, these soils and the habitation deposits of the Bronze Age were formed on the dried bottom of the lake below its modern lake level of 93.2 m a.s.l. In the Late Holocene, these soils in the coastal zone were subjected to waterlogging rather than to podzolization due to the rise in the lake’s level; they have evolved into the soddy gley soils.     

Specific features of soil formation in the taiga zone of Western Siberia

Specific features of soil formation in the taiga zone of Western Siberia are considered. The polygenetic nature of podzolic and gley-podzolic soils in the middle taiga zone, soddy-podzolic and soddy gley soils in the southern taiga zone, and meadow soils in the subtaiga zone is related to the pre-Holocene transformation of the lithogenic matrix upon activation of denudation and accumulation processes and the complicated Holocene evolution of these soils. A soil profile can be subdivided into separate layers according to the geomorphic features of the cryogenesis, the indices of interruption of soil formation, and the differences in the composition of the organic matter in the relict and modern humus horizons.     

Transformation of humic substances in soddy-podzolic soils under agrogenic impacts

The transformation of humic substances in soddy-podzolic soils under agrogenic impacts of different intensities and durations was studied. Indices of the initial stages of degradation and regradation of soil humus were revealed, and the humus status of soils under different fertilizing conditions was estimated.     

Assessment of agronomic homogeneity and compatibility of soils in the Vladimir Opolie region

Complexes of gray forest soils of different podzolization degrees with the participation of gray forest podzolized soils with the second humus horizon play a noticeable role in the soil cover patterns of Vladimir Opolie. The agronomic homogeneity and agronomic compatibility of gray forest soils in automorphic positions (“plakor” sites) were assessed on the test field of the Vladimir Agricultural Research Institute. The term “soil homogeneity” implies in our study the closeness of crop yield estimates (scores) for the soil polygons; the term “soil compatibility” implies the possibility to apply the same technologies in the same dates for different soil polygons within a field. To assess the agronomic homogeneity and compatibility of soils, the statistical analysis of the yields of test crop (oats) was performed, and the spatial distribution of the particular parameters of soil hydrothermic regime was studied. The analysis of crop yields showed their high variability: the gray forest soils on microhighs showed the minimal potential fertility, and the maximal fertility was typical of the soils with the second humus horizon in microlows. Soils also differed significantly in their hydrothermic regime, as the gray forest soils with the second humus horizon were heated and cooled slower than the background gray forest soils; their temperature had a stronger lag effect and displayed a narrower amplitude in seasonal fluctuations; and these soils were wetter during the first weeks (40 days) of the growing season. Being colder and wetter, the soils with the second humus horizons reached their physical ripeness later than the gray forest soils. Thus, the soil cover of the test plot in the automorphic position is heterogeneous; from the agronomic standpoint, its components are incompatible.     

Dynamics of Soil Properties and Plant Composition during Postagrogenic Evolution in Different Bioclimatic Zones

The postagrogenic dynamics of acidity and some parameters of humus status have been studied in relation to the restoration of zonal vegetation in southern taiga (podzolic and soddy-podzolic soils (Retisols)), coniferous-broadleaved (subtaiga) forest (gray forest soil (Luvic Phaeozem)), and forest-steppe (gray forest soil (Haplic Phaeozem)) subzones. The most significant transformation of the studied properties of soils under changing vegetation has been revealed for poor sandy soils of southern taiga. The degree of changes in the content and stocks of organic carbon, the enrichment of humus in nitrogen, and acidity in the 0- to 20-cm soil layer during the postagrogenic evolution decreases from north to south. The adequate reflection of soil physicochemical properties in changes of plant cover is determined by the climatic zone and the land use pattern. A correlation between the changes in the soil acidity and the portion of acidophilic species in the plant cover is revealed for the southern taiga subzone. A positive relationship is found between the content of organic carbon and the share of species preferring humus-rich soils in the forest-steppe zone.     

Solods of the Baraba Lowland and the Priobskoe Plateau: Their properties and genesis and the methods of their diagnostics

The properties, hydrological features, and genesis of the solods occurring in the Baraba Lowland and Priobskoe Plateau were studied. Methods for determining the hydromorphism degree are considered; the features of the similarity and differences between the solods and other soils with textural profile differentiation are shown. Depending on the reasons for the waterlogging, the solods should be divided into two groups: the solods of groundwater waterlogging and the solods of surface waterlogging. Criteria for their discrimination are suggested: the ratio between the contents of the clay fraction in the parent rock (or in the B2 horizon) and that in the A2 horizon, the changes in the pH values along the soil profiles, and the content of nonsilicate iron compounds. The solods studied are shown to be formed under the conditions of a stagnant-percolative regime and gleying. This circumstance is an obligatory and sufficient reason for the formation of the light-colored acid eluvial (A2) horizons. According to some basic properties of the soil solid phase (the acidity, the total chemical composition, and the clay pattern in the eluvial part), the gleyed solods are close or identical to the gleyed soddy-podzolic and gleyed chernozem-like podzolic soils. At the same time, the solods differ from the gleyed chernozem-like podzolic soils by their thicker A1 (or Ap) horizon and their higher humus content (5–7%).     

Transformation of humus substances in the long-drained surface-gleyed soddy-podzolic soils under conditions of pronounced microrelief and different agrogenic loads

The transformation of humus substances resulting from artificial drainage of the surface-gleyed soddy-podzolic soils under conditions of pronounced microtopography and different agrogenic loads was studied. The studied soil characteristics included acid–base conditions, the content and group composition of humus, the ratios between the fractions of humus acids, and optical density of humic acids. The features attesting to humus degradation were found in the soils of microdepressions periodically subjected to excessive surface moistening, in the soils of different landforms upon the construction of drainage trenches, and in the plowed non-fertilized soils. The response of humus characteristics to the changes in the ecological situation in the period of active application of agrochemicals for reclamation of the agrotechnogenically disturbed soils was traced. It was shown that the long-term dynamics of the particular parameters of the biological productivity of the soil depend on the hydrological and agrogenic factors, as well as on the weather conditions.     

Changes in the Content,Composition, and Properties of Humic Substances in Particle-Size Fractions of Soddy-Podzolic Soils under the Impact of Long-Term Drainage

Specific features of the transformation of humic substances in particle-size fractions of drained soddy-podzolic soils were studied on a field (12 ha) of the Experimental and Educational Center of Lomonosov Moscow State University in Moscow oblast. The field had a clearly pronounced microtopography. Surface-gleyed soddy-podzolic soils (Albic Stagnic Glossic Retisols (Loamic, Aric, Ochric)) of microdepressions with excessive surface moistening and nongleyed soddy-podzolic soils (Albic Glossic Retisols (Loamic, Aric, Ochric)) of elevated positions were examined. These soils were studied before the field drainage and during 25 years after drainage works in the periods differing in conditions of humification and with due account for not only drainage works but also other factors, such as topography and agrotechnology and their joint action. The specificity of transformation of humic substances in the soils and their particle-size fractions was analyzed in the basis of data on the organic carbon content, group and fractional composition of humus, the intensity of individual stages of humification (the neoformation of humic acids and the formation of humates), and the optical density of the fractions of humic acids. The results of the study of these properties in the fine soil fractions (<50 μm) made it possible to assess the response of the clay (<1 μm) and silt (1–5, 5–10, 10–50 μm) fractions to changes in the ecological situation and the role of separate particle-size fractions in the degradation of humus under adverse impacts. Overall, a clear tendency toward worsening of the humus quality was observed in both soils during the 25-year-long period, which is related to the long-term (20 years) agricultural use of the reclaimed field without application of agrochemicals. The features of humus degradation were mainly manifested in the finest (<10 μm) fractions with a general decrease in the humus content, slowing down of the formation of humic acids and humates, and considerable loss of humic acids, including their agronomically valuable fractions HA1 and HA2. The degradation of humus quality in the clay fraction was largely due to the impact of the reclamation (drainage) factor; the degradation of humus quality in the fine and medium silt fractions was mainly due to the negative changes in the agricultural background. Among negative consequences of the worsening humus quality, the lowering of soil fertility, ecological sustainability, and productivity of agrocenoses should be noted.     

Genesis,evolution, and catastrophic burying of the Ryshkovo paleosol of the Mikulino Interglacial (MIS 5e)

The results of a hierarchical morphogenetic, physicochemical, and mineralogical study of the Ryshkovo full-profile texture-differentiated paleosol of the Mikulino Interglacial from the section at Aleksandrov quarry in Kursk oblast are discussed. The correlation analysis of the stratigraphy of this section with global geological records made it possible to determine the position of the Ryshkovo paleosol in the chronostratigraphic system of the Late Pleistocene and to attribute it to stage MIS 5e; the duration of pedogenesis for this paleosol was no more than 12–15 ka. The results of the study indicate that the Ryshkovo paleosol is close in its properties to the Holocene soddy-podzolic soils of the East European Plain. No direct evidences in favor of the former interpretation of this paleosol as a lessivated soil genetically close to Luvisols of nemoral broadleaved forest of Central Europe have been found. The difference between the paleosol of the Mikulino Interglacial and the modern soddy-podzolic soils is mainly related to the distribution of clay coatings. In the upper part of the illuvial horizon of Mikulino paleosol, clay coatings are few in number, and typical tongues of podzolized (albic) material are absent in the profile. At the same time, silty coatings (skeletans) are abundant even in the lower part of the illuvial horizon. In general, the Mikulino paleosol is characterized by a smaller diversity of clay pedofeatures. These differences might be related to less contrasting fluctuations of the environmental conditions in the second half of the Mikulino Interglacial, to the periodical renewal of the eluvial part of Mikulino paleosol by erosional and accumulative processes, and to the absence of anthropogenic impacts on the soil during the Mikulino Interglacial. The burying of the Ryshkovo paleosol took place due to the intense development of erosional processes induced by the contrasting climatic events at the end of the interglacial period accompanied by catastrophic forest fires and sharp cooling of the climate upon the transition to the Valdai glaciation.     

Features of natural stability and agrogenic transformation of soil humus

The stabilities of the humus in different soil types (a soddy-podzolic soil from Moscow oblast, a deep typical chernozem from Kursk oblast, and a typical sierozem) have been compared on the basis of long-term studies of the composition, structural features, and properties of the humus acids formed under contrasting climatic conditions. The transformation features of the humic substances under agrogenic impacts of different intensities and durations have been studied by the example of a soddy-podzolic soil as a soil susceptible to environmental changes. The features of degradation of the humus quality and their manifestation at different levels of the structural organization of the humus system have been characterized.     

Soil development on the Crimean Peninsula in the Late Holocene

The study of soils of different ages in different physiographic regions of the Crimean Peninsula made it possible to reveal the main regularities of pedogenesis in the Late Holocene (in the past 2800 years). With respect to the average rate of the development of soil humus horizons, the main types of soils in the studied region were arranged into the following sequence: southern chernozems and dark chestnut soils > mountainous forest brown soils > gravelly cinnamonic soils. In the newly formed soils, the accumulation of humus developed at a higher rate than the increase in the thickness of humus horizons. A sharp decrease in the rates of development of soil humus profiles and humus accumulation took place in the soils with the age of 1100-1200 years. The possibility for assessing the impact of climate changes on the pedogenetic process on the basis of instrumental meteorological data was shown. The potential centennial fluctuations of the climate in the Holocene determined the possibility of pulsating shifts of soil-geographic subzones within the steppe part of the Crimea with considerable changes in the rates of the development of soil humus horizons in comparison with those in the Late Holocene.     

Changes in the chemical properties and characteristics of humus in soddy-podzolic soil due to main pipeline construction

The multiyear dynamics of the acid–base parameters and humus characteristics of soddy-podzolic soil affected by main pipeline (MP) construction was studied. Distinctions between the properties of technogenically disturbed soil and soil unaffected by MP construction observed 1, 10, 15, and 30 years after construction have been characterized. The deterioration of physical and chemical properties and clearly displayed features of technogenic degradation of humus have been identified throughout the entire observation period.     

Soils with complex organic profiles on the Vasyugan Plain

Soils with intricate patterns of their humus profiles developing in the neutral-calcium landscapes of the southern taiga of Western Siberia under highly dynamic paleogeographic, climatic, and weather conditions are characterized. The specific features of these soils comprise the diverse modern humus horizons along with the relic ones of different preservation rates, shallow leaching of carbonates, and a weak development of the middle-profile soil horizons. Specifying these organo-accumulative soils is substantiated by their high humus content against the geochemical background of the clayey calcareous parent rocks. The conjugated series of soils reflect different stages of the soil evolution (the humus profile degradation, the development of eluvial process, and the increase of contrasts in the acid-base conditions) and the hydromorphic transformation accompanied by the formation of organic horizons making the humus profile more complicated. In accordance with the diagnostic horizons, the position of the soils studied was determined in the Classification and Diagnostics of Soils of Russia. The relic enrichment of the humus horizon is proposed to be used as a specific feature of these soils.     

Assessment of the postagrogenic transformation of soddy-podzolic soils: Cartographic and analytic support

The results of experimental studies of the postagrogenic transformation of loamy soddy-podzolic soils on the southern slope of the Klin-Dmitrov Moraine Ridge are discussed. A chronosequence of soils (arable soils (cropland)-soils under fallow with meadow vegetation-soils under secondary forests of different ages-soils under a conventionally initial native forest) was examined, and the stages of the postagrogenic transformation of the automorphic soddy-podzolic soils were identified. The differentiation of the former plow horizon into the A1 and A1A2 horizons (according to the differences in the humus content, texture, and acidity) served as the major criterion of the soil transformation. A stage of textural differentiation with clay depletion from the uppermost layer was identified in the soils of the 20- to 60-year-old fallows. The specificity of the postagrogenic transformation of the soils on the slopes was demonstrated. From the methodological point of view, it was important to differentiate between the chronosequences of automorphic and semihydromorphic soils of the leveled interfluves and the soils of the slopes. For this purpose, a series of maps reflecting the history of the land use and the soil cover pattern was analyzed. The cartographic model included the attribute data of the soil surveys, the cartographic sources (a series of historical maps of the land use, topographic maps, remote sensing data, and a digital elevation model), and two base maps: (a) the integral map of the land use and (b) the map of the soil combinations with the separation of the zonal automorphic, semihydromorphic, and erosional soil combinations. This scheme served as a matrix for the organization and analysis of the already available and new materials.     

Spatial-temporal dynamics of organic carbon in soddy-podzolic soils of postagrogenic biogeocenoses

The organic carbon content in developed soddy-podzolic soils increased during the overgrowing of abandoned plowland with meadow and forest vegetation. The highest carbon content was recorded at the stage of 40–50-year-old forest, which was related to the largest input of organic matter into the soil and the intense litter decomposition during this period. A decrease in the soil carbon content was observed during the development of forest vegetation on the long-term hayfields in place of the former croplands, because the humus content in the lower part of the old-arable horizon decreased significantly. The spatial variability in the distribution of organic carbon in the soils increased with the development of forest biogeocenoses.     

Temperature field of complex soilscapes (by the example of the Vladimir opolie region)

Problems of the assessment of soil temperature regime at the polypedon level have yet to be solved. An approach suggested by the authors consists of three stages: (1) the characterization and prediction of the soil water regime as a factor influencing the soil temperature regime, (2) the obtaining of thermophysical functions for the particular elements of complex soilscapes, and (3) the calculation and assessment of the temperature regime of complex soilscapes in the form of the functional fields of soil temperature isopleths. This approach has been applied to predict the soil temperature regime of an arable field in the Vladimir opolie region. The complex soilscape of the field consists of medium loamy agrogray soils, agrogray soils with the second humus horizon, and podzolized agrogray soils. At the beginning of the growing season, minimum temperatures are observed in the areas of agrogray soils with the second humus horizon; the difference in soil temperatures at a depth of 20 cm reaches 1°C, and the difference in the sum of active soil temperatures reaches 20°C. Then, this difference changes considerably, so that the agrogray soils with the second humus horizon become warmer than the agrogray soils. In general, the functional field of soil temperatures within the complex soilscape is highly dynamic and diverse, which is specified by the variability in the water-physical and thermophysical properties of particular soils.     

Complex pedogenesis related to differential aeolian sedimentation in microenvironments of the southern part of the semiarid region of Argentina

The aim of this paper is to explain soil genesis and spatial variability in the soil cover of a flat landscape in the southern part of Argentina's semiarid region. Soil survey data indicate random differences in the properties of soils lying within a few hundred meters of one another, as reflected in an intricate distribution pattern which cannot be explained by the climatic theory of soil genesis in a single pedogenetic cycle. This pattern is unrelated to the actual vegetation cover. The soil parent materials consist of a <2-m mantle of aeolian Holocene sediments overlying a thick plio-Pleistocene “tosca” layer (calcrete, caliche). The undulations in the tosca layer are indicative of a paleomicrorelief levelled up to the present surface after the deposition of the Holocene sediments. Soils with fine-textured sandy loess and strong development (Meridiano soil: A–Bw–Ck–2Ckm) occupied a higher position within paleomicrorelief of the tosca layer. Adjacent soils on border or intermediate positions of the petrocalcic paleosurface have more complex profiles with a relict calcic horizon (Vizcachera soil: A–C–2Ck–3Ckm) and coarser texture (silty clayey sand) in the topsoil. In the lower positions of the paleomicrorelief of the tosca layer, the silty clayey sand directly overlie the petrocalcic horizon (El Khazen soil: A–C–2Ckm). The intricate distribution pattern is due to the coexistence of older polypedon (Meridiano soil), remnants of an earlier erosion cycle complexed with two younger soils, one from partial erosion (Vizcachera soil) and the other where total erosion of earlier soils was followed by successive pulses of aeolian deposition (El Khazen soil). The distribution pattern of the three soils thus reflects a complex history involving at least three stages of landscape evolution.