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.     

Assessing the humus status and CO<Subscript>2</Subscript> production in soils of anthropogenic and agrogenic landscapes in southern regions of the Russian Far East

The humus status and CO₂ production have been assessed in soils of natural and anthropogenic landscapes in southern regions of the Far East with different types of redox conditions. A higher production of CO₂ is typical of burozems and soddy-eluvial-metamorphic soils with oxidative and contrast redox conditions. These are soils with medium or high humus content, high potential humification capacity, and medium enrichment with catalase. A decrease in the content of humus in the plow horizons of soils in agrogenic landscapes is revealed compared to their natural analogues. The studied soils mainly have humus of the fulvate–humate type. The fractions strongly bound to the mineral soil component prevail in humic acids. In waterlogged mucky-humus gley soils, the anaerobic conditions hamper the biological activity and transformation of organic matter, which favors its accumulation. A low production of CO₂ is observed in soils with reducing conditions. To determine the differences between the CO₂ emission parameters in soils of agrogenic and natural landscapes, monitoring studies should be extended.     

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.     

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.     

The humus status of modern and buried volcanic soils in Mexico and its role in the paleogeographic interpretation of tephra-paleosol sequences

Chemical and optical characteristics of soil humus have been analyzed as “memory” components of the Pleistocene volcanic paleosols in Mexico. We have studied the A1 horizons of buried Andosols of the Nevado de Toluca series and of the modern Andosols formed under different bioclimatic conditions. Data on the organic matter of buried paleosols suggest that Andosols of the Nevado de Toluca series were formed in humid forest ecosystems. Optical characteristics of the humic acids and data on the molecular-mass distribution of the humus make it possible to assume that these soils were formed under pine forests rather than under fir forests.     

Specific features of the humus status in soils of Buryatia

The humus content in soils of Buryatia varies significantly in dependence on the local hydrothermic conditions. All the studied soils are characterized by a relatively short humus profile, a sharp drop in the humus content down the soil profile, considerable amounts of the humin fraction and the fraction of humic acids bound with sesquioxides, and a moderate humus enrichment with nitrogen.     

Light Gray Surface-Gleyed Loamy Sandy Soils of the Northern Part of Tambov Plain: Agroecology,Properties, and Diagnostics

Light gray soils of Tambov oblast mainly develop from sandy and loamy sandy parent materials; these are the least studied soils in this region. Despite their coarse texture, these soils are subjected to surface waterlogging. They are stronger affected by the agrogenic degradation in comparison with chernozems and dark gray soils. Morphology, major elements of water regime, physical properties, and productivity of loamy sandy light gray soils with different degrees of gleyzation have been studied in the northern part of Tambov Plain in order to substantiate the appropriate methods of their management. The texture of these soils changes at the depth of 70–100 cm. The upper part is enriched in silt particles (16–30%); in the lower part, the sand content reaches 80–85%. In the nongleyed variants, middle-profile horizons contain thin iron-cemented lamellae (pseudofibers); in surface-gleyed variants, iron nodules are present in the humus horizon. The removal of clay from the humus horizon and its accumulation at the lithological contact and in pseudofibers promote surface subsidence and formation of microlows in the years with moderate and intense winter precipitation. The low range of active moisture favors desiccation of the upper horizons to the wilting point in dry years. The yield of cereal crops reaches 3.5–4.5 t/ha in the years with high and moderate summer precipitation on nongleyed and slightly gleyed light gray soils and decreases by 20–50% on strongly gleyed light gray soils. On light gray soils without irrigation, crop yields are unstable, and productivity of pastures is low. High yields of cereals and vegetables can be obtained on irrigated soils. In this case, local drainage measures should be applied to microlows; liming can be recommended to improve soil productivity.     

Special features of humus acids extraction from soils by sodium pyrophosphate solutions of different alkalinity

The regularities of extracting humus acids from soils of different types with solutions of sodium pyrophosphate at the equilibrium pH values of 5–13 were studied. The increase in the humus acids yield from the soils with the increasing alkalinity of the solution applied is directly related to the capability of acid functional groups (carboxyl and phenol hydroxyl) for dissociation at definite pH values. The regularities of the changes in the chemical nature and degree of humification of humus acids extracted from the soils related to the pH of the solution were revealed. A sodium pyrophosphate solution (pH 10) was suggested for extracting the humus acids most active in the given soil.     

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.     

Relationships between parameters of the humus status of forest and meadow soils and their altitudinal position on the main Crimean range

The influence of bioclimatic conditions related to the elevation above sea level on the quantitative and qualitative parameters of humus in mountain soils has been studied. It is shown that changes in the water and temperature conditions with the altitude do not exert significant effect on the humus content in mountain- forest soils, because the total amount of soil organic matter mainly depends on the composition and state of the vegetation cover. The humus content is the highest in meadow soils formed on mountain plateau with excessive moistening, which determines the formation of dense grass cover and the temperature regime favorable for humification. The percentage of Cha in the composition of Corg and the optical density of humic acids (HAs) are the qualitative parameters of the soil humus status changing with the altitude. The intensity of humus coloring of the soil depends on the content and optical density of HAs. A comparison of color intensity in the mountainous meadow chernozemlike soils and plain chernozems has shown its significant dependence on the hydrothermic conditions.     

Transformation of an agrogray soil on a slope complicated by hollows in the Zusha River basin

Changes in the profile of gray forest soils on a tilled slope with manifestations of active erosion and a known duration of the plowing were analyzed. Factors determining the transformation of the composition and properties of individual parts of the soil profile were considered. Specific changes in the soil profile were revealed depending on the age of the plowland and its position in the relief. Tendencies of the agrogenic transformation of the lower horizons were found to depend on changes in the humus profile and the time of the soil existence in a relatively stable state.     

Composition and structure of aggregates from compacted soil horizons in the southern steppe zone of European Russia

The composition and structure of aggregates from different agrogenic soils in the southern steppe zone of European Russia have been studied. It is shown that the multi-level study (from the macro- to microlevel) of these horizons makes it possible to identify soil compaction caused by different elementary soil processes: solonetz-forming, vertisol-forming, and mechanical (wheel) compaction in the rainfed and irrigated soils. The understanding of the genesis of the compaction of soil horizons (natural or anthropogenic) is important for the economic evaluation of soil degradation. It should enable us to make more exact predictions of the rates of degradation processes and undertake adequate mitigation measures. The combined tomographic and micromorphological studies of aggregates of 1–2 and 3–5 mm in diameter from compacted horizons of different soils have been performed for the first time. Additional diagnostic features of negative solonetz- forming processes (low open porosity of aggregates seen on tomograms and filling of a considerable part of the intraped pores with mobile substance) and the vertisol-forming processes (large amount of fine intraaggregate pores seen on tomograms and a virtual absence of humus–clay plasma in the intraped zone)—have been identified. It is shown that the combination of microtomographic and micromorphological methods is helpful for studying the pore space of compacted horizons in cultivated soils.     

Extraction of active aluminum from acid soils in Japan with different reagents

The paper deals with methods of determining active aluminum in acid soils. Extraction reagents examined were 4 acids, 4 salts, and 11 compounds of chelating agents. The effects of different conditions, such as pH, temperature, shaking time and the ratio of solution to soil were observed. Barium salicylate solutions, in which the normal concentration of barium and the molar concentration of salicylate were 1.0 and 0.1 respectively, were found promising as extractants. Initial pH of the solution, shaking time and the ratio of solution to soil were set at 7.0, 2 hours and 50:1, respectively. Ammonium salicylate and ammonium EDTA also extracted active aluminum but amounts varied according to different conditions. The most promising procedure was applied to a few kinds of soils and to soil treated with either lime or phosphate. The amounts of aluminum extracted from soils high in humus were larger than those from soils low in humus. Liming or phosphate application decreased the amounts of aluminum extracted.     

A comparative characterization of postagrogenic soils under different lithological conditions in the Southern Taiga

The soils under two meadows overgrown by a small-leaved forest that are no longer used for agricultural purposes were studied. The changes in the plant cover resulted in an increase in the soil acidity, a decrease in the humus content, and a transformation of its composition; the content of fulvic acids increased. The most essential modifications to the soils were related to alterations in the density of the birch forest. The degree and rate of these changes depended on the local environmental conditions, such as the soil texture, the depth of the moraine layer, and the dynamics of vegetation. The dynamics of acidity were displayed to a greater degree in the sandy soils, while the dynamics of the humus content and its reserves were evidenced in the heavy-textured soils.     

Stages of the development of alluvial soils in the Bikin River valley (the Amur River basin) in the Middle and Late Holocene

The evolution of alluvial soils in the Bikin River basin in the Middle and the Late Holocene is discussed. On the basis of biostratigraphic data, four pollen zones have been identified in the soils: Pinus koraiensis-Picea, Pinus koraiensis-Quercus-Sphagnum, Betula-Alnus-Alnaster, and Quercus. A set of soil characteristics (texture, acid-base properties, and the organic matter content and group composition) have also been determined. These data allow us to distinguish between four stages of alluvial soil formation in the Bikin River basin. They characterize humus-forming conditions in the Middle and the Late Holocene. Reconstruction of ancient vegetation conditions makes it possible to conclude that climatic fluctuations were synchronous with changes in the soil characteristics. During the Holocene climatic optimum, humus was formed in a slightly acid medium, and humic acids predominated. In cold periods with increased precipitation, fulvic acids predominated in the composition of humus, and the portion of insoluble residue was high because of the more acid medium. The stages of alluvial pedogenesis in the Bikin River valley follow the sedimentation model of soil evolution. Alluvial gray humus soils evolved from typical gray humus soils under meadow communities during warm periods to gleyic and gleyed soils under birch shrubs and alder groves in colder and wetter periods.     

卧龙自然保护区森林土壤有机质的研究

研究了四川卧龙自然保护区不同海拔高度的五种植被(常绿阔叶林、落叶阔叶林、针阔混交林、暗针叶林和高山草甸)下的土壤中有机质的含量、组成和性质。主要结果如下。1.各土壤虽然生物气候条件差异悬殊,但其腐殖质均属于富里酸型。2.落叶阔叶林、针阔混交林和暗针叶林下的粗腐殖质也属于富里酸型;红外和紫外光谱说明,它们和“成熟的”腐殖酸有明显的不同。3.土壤有机质含量与土壤物理性质和速效性养分含量有密切的关系。     

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.     

Characteristics of dissolved organic matter and phenolic compounds in forest soils under silver birch (Betula pendula), Norway spruce (Picea abies) and Scots pine (Pinus sylvestris)

The aim was to characterize dissolved organic matter in soils under different tree species. Molecular size distribution and chemical composition of dissolved organic carbon and nitrogen were determined in water extracts from humus layers and mineral soils taken from silver birch ( Betula pendula Roth.), Norway spruce ( Picea abies (L.) Karst.) and Scots pine ( Pinus sylvestris L.) stands. Concentrations of tannins and 15 phenolic acids in the humus layers were measured. Per unit of organic matter, the concentrations of dissolved organic C and N were larger in birch and spruce humus layers than in the pine humus layer. In the underlying mineral soil, the concentrations of dissolved organic C were similar at all sites, but the concentration of dissolved organic N was greater in spruce and pine soils than in birch soil. In all soils, the 10–100 kDa fraction was the most abundant molecular size group and hydrophobic acids the most abundant chemical group of dissolved organic C. In all humus layers, hydrophobic acids and hydrophilic bases were the major components of dissolved organic N. There were only minor differences in the concentrations of total tannins in the humus layers under different tree species. Small-molecule tannins (about < 0.5 kDa) were most abundant in the birch humus, and large-molecule tannins in the pine humus. Coniferous humus contained more ferulic and p -coumaric acids than did the birch humus. The concentrations of 3,4 and 3,5-dihydroxybenzoic acid, vanillic acid and 4-hydroxybenzoic acid were similar in all soils.     

Floodplain soils in the lower reaches of the Khovd River in the Great Lakes Basin of Mongolia

The ecologic-geographic conditions of the pedogenesis and the diversity and classification position of the floodplain soils in the lower reaches of the Khovd River have been studied. The soil cover is composed of alluvial soils of the synlithogenic trunk and solonchaks of the postlithogenic trunk. The major properties of these soils are characterized. The dominant role in the soil genesis is played by gleyzation and salinization processes. Data on the contents of the macro- and microelements in the soils are given, and their agrochemical effect is assessed. Potential destructive agrogenic processes in the soils of floodplain ecosystems upon their use for haymaking and pasturing and upon their use for arable farming are discussed. A grouping of the major soil types in the studied area with respect to their use is proposed.     

Properties of soils in Southern Sikhote-Alin using the example of the Ussuri Reserve

The physical and physicochemical parameters of soils in the Ussuri Reserve presenting the typical soils of the Southern Sikhote-Alin were determined for the first time with consideration for the composition and structure of the soil cover. The soils in the surface horizons had loamy and clay loamy texture. It could vary depending on the overlain soil processes. All the soils were characterized by the minimum base saturation and an increase in the actual acidity down the profile. The organic matter was characterized by an abrupt decrease down the profile and the high mobility of the humus substances. The fractional-group humus composition was analyzed, and the humus status of the soils was characterized. The burozems were regarded as background soils, while a humus-illuvial podburs were referred to the rare ones. Recommendations were developed for the organization of soil monitoring with key test plots in different ecological conditions as examples.