No 12 (2023)

An aim of analytical review is to systematize information about quantitative characteristics of changeability in the content and storage of organic carbon (C_org) in soils. The review considers evaluations of validity and reproducibility of C_org determination, spatial variability and heterogeneity of C_org at different hierarchic levels of soil cover pattern and change them in time. The most powerful factor of C_org changeability in soils is spatial variability. Ascending trend of absolute standard deviation and coefficient of variation for C_org content and storage in soil with the increase in the logarithm of site area has been revealed. However, the values of the indicators of spatial variation of C_org have a wide spread in each narrow range of variation of the plot area, which leads to high uncertainty of the estimates as the area coverage increases. Direct dry combustion method is considered preferable among used methods for determination of C_org content. It allows obtaining valid (i.e. with the least systematic deviations) and well reproducible data. Indirect Turin’s and Walkley-Black’s methods systematically underestimate the C_org content and have reproducibility comparable with amplitude of seasonal dynamics and with minimal values of spatial variability indices within elementary soil area. Obtaining estimates of long-term trend of C_org content strict adherence to stringent monitoring conditions over time intervals of more than 15 years. Spatial variation of C_org storage is stronger than C_org content, which further increases the monitoring requirements.

The features of the structure, properties, and temperature regimes of soils functioning in two different drained lake basins of the Bolshezemelskaya tundra are characterized. The basins differ significantly in the features of landscape development, the composition of bottom (soil-forming) sediments, and the patterns of the soil and vegetation cover. In a naturally drained basin composed of mineral (sandy and clayey) bottom sediments, soils belonging to the departments Gley, and Poorly developed are formed, which are typical for the watershed landscapes of the region. Soils function as ecosystem-modified permafrost-affected profiles, partially protected from thaw. The soil profile is acidic, not saturated with bases, with moderate carbon content in the mineral horizons. In the artificially drained basin, covered with a layer of silted peat, predominantly peaty permafrost-affected soils were formed, including peat soils of tundra meadows, which are unique for the landscapes of the Bolshezemelskaya tundra. Peaty soils of the basin appear to be as ecosystem-protected, i.e. protected from thawing, and they are characterized by high ash content and slightly acidic reaction. A significant differentiation of the studied soil parameters are determined by different basins, which are different according to the composition of parent sediments, the specifics of landscape development, and manifestations of present-day cryogenic processes.

The results of soil-genetic studies conducted on sod-podzolic soils in the Gryazovetsky district of the Vologda region are presented. The modern soils of the study area are represented by sod-podzolic soils of different variations (Albic Retisols) formed on loamy paleocryogenically transformed soil-forming rocks. The concept of the role of paleocryolithogenic processes that determined the formation and evolution of modern sod-podzolic soils of the north-east of the East European Plain is proposed. The considered set of paleocryolithopedogenic processes in modern zonal sod-podzolic soils allowed us to reconstruct the conditions for the formation of soils located in the periglacial region of the Valdai glaciation. The results obtained have expanded the understanding of the influence of the processes of Late Pleistocene cryogenesis and lithogenesis on the evolution of modern sod-podzolic soils of the northeast of the East European Plain. The obtained data show the processes forming the soils under consideration and for the first time it is proposed to isolate paleocryolithogenic soil combinations in the structure of the soil cover as a result of the combined natural process – paleocryolithopedogenesis.

The ongoing climatic changes have the greatest impact on natural ecosystems in high-latitude areas, as warming climate, as well as increasing anthropogenic load associated with the development of Arctic zone, contribute to the degradation of frozen peatlands and an increase in the thickness of seasonally thawed layer of soil. The relevance of studying peat oligotrophic soils (Cryic Histosols) of the northern territories of Western Siberia is associated with the fact that their degradation enriches natural waters by organomineral substances, which containing a large number of chemical elements, including heavy metals, contributing to changes in the hydrogeochemical properties of natural waters of the North. The article describes the main properties of peats sampled from different horizons of soil profiles laid down at key areas covering the territory of YNAO from north to south and from west to east. The chemical composition of soils was analyzed at the IPA SB RAS using standard methods. The concentrations of gross and mobile forms of metals (Fe, Ca, K, Na, Mg, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn) were investigated by optical atomic emission spectrometry and flame atomic absorption spectrometry, respectively. It has been determined that a characteristic feature of the distribution of concentrations of chemical elements in peat oligotrophic soils of the northern part of Western Siberia is the presence of two maxima within the soil profile. The first is confined to the upper horizons showing signs of degradation, while the second is confined to the upper part of the permafrost. Statistical analysis using principal component method showed that low ash content, pH and C/N ratio are associated with high mobility of K, Cu, Zn and Mg. The mobility of Fe, Mn, Pb, Cd, and Cr is associated with an increase in ash content, pH, and N_total in the upper part of permafrost organogenic rocks.

The issues of soil-hydrophysical support of mathematical models of moisture movement, taking into account the heterogeneity of the soil, due to the spatial change in texture, are considered. The processes of vertical movement of moisture on large-sized lysimeters of the Federal Scientific Center of Agroecology of the Russian Academy of Sciences (Volgograd) were studied. The influence of statistical heterogeneity of hydrophysical parameters of lysimeter substrates was studied on models of moisture transfer dynamics and formation of gravity flow developed in the environment of the HYDRUS-1D software package. The change in texture along the vertical profile of the lysimeters and the related variability of the main hydrophysical characteristic (WRC) were taken into account. The granulometric heterogeneity of the substrates was estimated by the scaling method, according to the scale factors of the WRC parameters, assuming a normal probability distribution of the logarithms of the pore space capillary radii between soil particles. The effect of texture on water-holding capacity, boundary and initial conditions, intensity of gravity runoff and cumulative accumulation of moisture was studied.

The paper analyzes the results of eleven survey cycles of arable soils conducted from 1964 to 2022 in the southwestern part of the Central Chernozem region in the Belgorod region. In the steppe zone of the region, ordinary chernozems predominate, in the forest-steppe zone – typical and leached chernozems. During the eleventh survey cycle (2019–2022), the average level of application of mineral fertilizers was 114.4 kg a.i./ha, organic – 9.6 t/ha, liming of acidic soils – 43.8 thousand hectares per year. As a result, the average yield of winter wheat increased to 5.09, sugar beet – up to 45.6, corn for grain – up to 7.15 t/ha. At the same time, the maximum value of the weighted average content of organic matter (5.3%) was recorded in the soils of arable land for the entire observation period. The proportion of acidic soils decreased to 28.6%, including moderately acidic soils, to 3.0%. The value of hydrolytic acidity decreased to 2.7 cmol_c/kg. The weighted average content of mobile forms of phosphorus (139 mg/kg) and potassium (161 mg/kg) is the highest in the Central Black Earth region. 85.7% of the surveyed soils belong to the category of low content of mobile forms of sulfur, zinc – 97.2, copper – 92.5, cobalt – 98.8, manganese – 40.1, molybdenum – 21.3%. In terms of the content of mobile forms of boron, 98.2% of the soils are classified as highly rich.

The eluvozems and soddy eluvozems on two-layer deposits dominating in the soil cover of the Zvenigorod biostation of Moscow State University contain, on average, 65–83 t/ha of organic carbon in the litter and a meter-deep layer of mineral strata. Carbon stocks are minimal in the soddy eluvozem of the complex spruce forest (59–68 t/ha), which is characterized by a lighter granulometric composition, and reach 76–92 t/ha in the soils of the birch–spruce and complex pine–spruce forests. At the same time, 3.3–5.8 t C/ha or 4–9% of the total organic carbon reserves are concentrated in the litter, and 64–69% in the upper mineral layer (0–20 cm). Different levels and profile distribution of organic carbon reserves in soils are determined by lithological and granulometric features and the nature of vegetation. The contribution of water-extractable organic carbon compounds to their total content in the upper mineral horizons of soils does not exceed 1.3–1.8%, microbial carbon, 1.7–2.4%. In acidic light loamy soils, the enrichment in calcium and potassium, the cation exchange capacity, the content of exchangeable bases, and the degree of saturation can serve as indicators of the content and reserves of organic carbon at the ecosystem level. The relationship with the content of finely dispersed fractions and oxalate-extractable Al and Fe is manifested to a lesser extent due to the similar origin and properties of soils. The variability of organic carbon stocks in soils is determined to the greatest extent by its content, the influence of which decreases with depth. Accounting for spatial heterogeneity, field measurements of the density and proportion of fine earth, and correct analytical determinations are essential components of the assessment of carbon stocks in soils of forest ecosystems as part of a national monitoring system for carbon pools and greenhouse gas fluxes under development.