No 5 (2024)

Meadow podbels (dark-humus gleyic and gleypodbels in the Classification of soils of Russia) are subject to deep and prolonged freezing in the western part of their area. It is manifested in cryogenic deformations of genetic horizons as well as in thin sections. Micromorphological features of soils on permafrost are well known. and the purpose of this research was to reveal them in three profiles of meadow podbels as related to soil cryological and hydrological regimes. Unlike northern cryogenic soils. the meadow podbels have dark-humus horizons with weak cryogenic manifestations; in eluvial horizons. there are frost-created platy microstructures and numerous iron-organic nodules of any size. Specific microstructures are common in textural BT horizons: these are rounded or ellipsoidal peds with iron-organic nodules in their nuclei. and ooids: rounded aggregates with iron impregnation/segregations in their centres and circular striated b-fabric of the micromass on aggregate peripheries. Typical gley mirofeatures in the lowermost clayey horizons are well expressed. along with illuviation clay coatings. part of them being deformed. The skeleton grains and micromass re-arrangement. as well as concentric orientation of skeleton grains in the groundmass. are weak as compared to cryogenic soils with permafrost.

Adaptation of the farming systems that aim to store carbon in agricultural soils may be one of the ways to address global climate change. Current study aims were at estimating organic carbon sequestration in the Russian cropland at a soil depth of 0-30 cm by creating a series of maps. Data from global and national databases were used as the input data. Maps were generated in the framework of the FAO Global Soil Carbon Sequestration Map (GSOCseq) project according to the unified methodology using the RothC model to predict the rate of carbon sequestration in the period 2020–2040 under the business-as-usual scenario, as well as under sustainable soil management scenarios with a different increase in organic matter intake (+5, +10 and +20%) due to the use of carbon-saving practices. The total potential rate of sequestration by cropland of the Russian Federation in a layer of 0–30 cm under business-as-usual scenario can be estimated as 8.5 Mt/year, the estimate under sustainable soil management scenarios can reach up to 25.5 Mt/year. It is shown that the carbon sequestration by cropland of each zone of soil-ecological zoning (except for the light chestnut and brown semi-desert soils, where it around zero) and on a national scale are positive. The following regions have the greatest potential for sequestration: Altai Krai, Omsk Oblast, Novosibirsk Oblast, Krasnoyarsk Krai. In a number of subjects of the Russian Federation: the Krasnodar Territory, the Republic of Crimea, the Rostov Region, the Primorsky Territory, the Republic of Adygea and the Kaliningrad Region, measures should be taken to introduce the practice of sustainable management of soil resources.

The small steppe plots (steppoids) occur at southern slopes among open larch forests of the Lower Kolyma area (northeast Siberia). Depending on a soil parent material they are divided into petrophytic (on a bedrock eluvo-diluvium) and thermophytic (on a silty loam of the Yedoma formation (Ice Complex)) steppoids. A xeromorphic deep thawing soils with diverse humus accumulative horizons, high roots content and considerable water stable powder-like structure develop under steppoids. Soils of steppoids are zooturbated, especially thermophytic ones. They differ from those of the surrounding taiga landscape in the following features: decreased actual and potential acidity; higher content of exchange bases, water-soluble salts, carbonates and organic nitrogen; smaller ratio between concentrations of oxalate- and dithionite-extractable iron. Dark mulle-like forms of humus on the surface of mineral grains are widely represented among the microaccumulations of organic matter in taiga-steppe soils. The cryoxerozem soil formation trait shows better in the event of petrophytic steppoids. Despite the similarity of the soils of thermophytic steppoids with steppe cryoarid ones, they differ in the absence of carbonate accumulative and criohumic horizons as well as the relatively high acidity. Flow-carbonaceous grey-humus lithozem and flow-carbonaceous grey-humus or duff dark-humus soils are distinguished within the petrophytic steppoids just as surface-turbated (zooturbated) grey-humus or duff dark-humus soils are distinguished within the thermophytic steppoids.

The impact of industrial logging on the carbon cycle of boreal forests is characterized by significant uncertainties, which is largely due to the lack of information on carbon fluxes (in particular, soil respiration) in felling sites. The aim of study is to assess the effect of clear felling on CO₂ emission from the soil surface of a coniferous-deciduous forest on a typical podzolic soil (Albic Retisol). The investigation was executed during the snowless periods (May-October) of 2020–2022 in a coniferous-deciduous forest and its felling site carried out in the winter of 2020. The carbon dioxide emission was measured by a LI COR 8100 gas analyzer. A brief description of the weather conditions during the years of research and the dynamics of soil temperature at a depth of 10 cm is given. A positive, statistically significant relationship between soil respiration and soil temperature at a depth of 10 cm (R² = 0.17–0.75; p < 0.001) was detected for the analyzed objects. The correlation with soil moisture was both positive and negative and statistically insignificant except data obtained in 2022 in the undisturbed control forest. The high values of CO₂ flux during the snowless period were observed in July–August and was 3.90–5.62 gC/ m²/ day and 2.3–2.5 gC/m²/day in undisturbed forests and felled areas, respectively. In 2021, the peak of CO₂ release shifted to June. Clear felling has a negative effect on the soil respiration of Albic Retisol that decreased by 1.2–1.9 times in the conditions of the middle taiga of the Komi Republic. The most (55–66%) of the C–CO₂ efflux during the snowless period was emitted during the summertime, and the vegetation period (May–September) contribution was 84–88%. The obtained data will serve to determine the role of industrial logging in the carbon cycle of taiga forests.

First time comprehensive studies of soil erosion were carried out in a 42-hectare catchment area (near the Lomovets, Orel region) in the zone of Luvic Phaeozems with erosion resistance is significantly lower than that of Chernozems. Analysis of archival and historical cartographic materials showed that the duration of plowing of the catchment is 200 ± 10 years. The rates of soil erosion and accumulation over the entire plowing period, post Chernobyl period, last 50 ± 25 years and single erosion event (which occurred on May 31, 2022) were determined based on the use of field methods (soil-morphological, radiocesium, rain rills method, detailed survey using drone) and WaTEM/SEDEM erosion model calculation. The estimates of soil losses and accumulation indicate significant fluctuations in the rates of erosion-accumulative processes over the past 200 years, which are mainly due to the conditions of the formation of melt runoff, the repeatability and distribution of runoff-forming heavy rain within the warm season, the set of crops sown, the frequency and methods of tillage, changes in field boundaries. The average annual estimates of soil erosion for the agricultural period are higher than those for the post-Chernobyl period, since the rates of soil erosion have decreased in the last three decades. Estimates of soil losses using the WaTEM/SEDEM model are generally comparable with the results of determining soil losses based on the soil-morphological method, provided that the redistribution of sediment to the lower boundaries of arable land is taken into account. The spatial structure of a single erosive event turned out to be largely close to the spatial structure of the location of the areas of eroded and aggradational soils formed during the entire agricultural period.

Fire induced changes in the content and composition of polycyclic aromatic hydrocarbons (PAHs) in organic horizons of the boreal zone soils are considered. Experiment of combustion under oxygen deficient conditions were conducted. The organic horizons of soils as peat (sphagnum oligotrophic) and two types of forests (lichen pine and green-moss spruce) were selected. The PAHs content was determined by high-performance liquid chromatography. It was found that combustion conditions, composition of organic horizons and combustibility significantly affect the content and composition of PAHs. The formation of PAHs occurs to a greater extent at 300°C. Compared with the original samples, the content increases from 2.7 to 9.7 times. Compared with the peak PAHs content (in 300°C) samples, a decrease from 5.8 to 33.0 times is found at 500°C. It is likely that the significant decrease in the content of polycyclic aromatic hydrocarbons is due to the decomposition of substances to simpler ones. The ratio of low molecular to high molecular weight PAHs is indicated. The obtained ratio greater than 1.0 can serve as an indicator of pyrogenic origin of polyarenes.