Ivan Alekseev

High-Arctic soils are extreme ecosystems where microbial and viral roles remain poorly studied. Climate-driven vegetation expansion may alter these environments, but its impact is unknown. We generate a shotgun metagenomic database from four High-Arctic islands, comparing vegetated and unvegetated sites at two depths (0–2 cm and 30–50 cm). We analyse the functional gene potential, including biosynthetic gene clusters (BGCs) and antibiotic resistance genes (ARGs) in metagenome-assembled genomes (MAGs), and assess viral diversity. Vegetated soils at 30–50 cm were enriched in genes for carbon/nitrogen cycling, energy production, and carbohydrate metabolism, indicating enhanced nutrient inputs. Conversely, unvegetated soils show higher BGC and ARG richness, reflecting microbial competition under nutrient limitation. Viral richness decreases in surface vegetated soils, while diversity and giant virus (Nucleocytoviricota) abundance increase with depth. These findings reveal how vegetation and soil depth modulate microbiomes and viromes, critical for predicting ecosystem trajectories in a warming world.

Understanding the spatial variability of soil organic carbon (SOC) content and its functional pools under current farming practices is crucial for developing targeted C management. This study quantified and predicted the farm-scale variability of SOC pools across conventional tillage (CT) and no-tillage (NT; 8–14 years) practices at two sites (Rostov and Krasnodar) in Russia. The soil types at Rostov and Krasnodar farms were Calcic Chernozem (sunflower–wheat rotation) and Stagnic Chernozem (maize–wheat rotation), respectively. The average SOC content at the Rostov site was higher than the Krasnodar site by 41% and 28% in 0–10 and 10–30 cm, respectively. For both sites, there was no clear trend in SOC variability between NT and CT practices. However, topsoil microbial-available C pool (mineralized for 180 days) was most sensitive to tillage systems, unlike unchanged particle-size C pools. Specifically, it increased from CT to NT at the Rostov site (by 7–16%), but it showed a decreased trend at the Krasnodar site (by 11–29%). Gradient boosting machines statistical models with remote sensing data based explanatory variables (spectral, topography) accurately predicted the spatial distributions of topsoil C content (R² = 0.99) and its microbial-available pool (R² = 0.78) across the farmland areas. The main explanatory variables included topography, vegetation distribution, moisture and thermal regimes. For both sites, DNDC modeling showed that applying NT versus CT for 30 years could potentially increase SOC in the topsoil by 27–28% and decrease it in the subsoil by 6–9% (sunflower–wheat–maize–wheat rotation; annual N and P rates of 41–80 and 0–52 kg ha⁻¹). This study provides insights into current agricultural challenges and the developing site-specific strategies for managing soil C accrual in the Chernozem region.

In East Antarctica, ice-free areas (oases) exhibit a wide range of environmental conditions that influence soil development. Exploring the interactions between biological and abiotic factors, along with the composition and behavior of soil organic matter, offers valuable insights into how Antarctic ecosystems react to environmental stresses. This study examined the biogeochemical characteristics and molecular composition of soil organic matter in Cryosols of the Thala Hills oasis, Enderby Land, East Antarctica. The soils studied are generally shallow, with mostly coarse textures, slightly acidic to near-neutral pH levels (from 5.40 to 6.87), and very low organic carbon content in most of the samples (TOC

Adapting agriculture to long-term accrual of organic carbon (С) is beneficial both for ensuring food security and for mitigating climate change. This study quantified the responses of total soil C content and its constituent pools to implementing no-tillage (NT) versus conventional tillage (CT) on farms with contrasting water regimes. The farms were chosen at two sites in the Russian steppe zone: Rostov with non-waterlogged Calcic Chernozem (CCH; sunflower-wheat rotation) and Krasnodar with periodic waterlogged Stagnic Chernozem (SCH; maize-wheat rotation). At each site, we surveyed the 0–10 cm and 10–30 cm soil layers in one continuous CT field and two short-term NT fields (8–14 years). The average C content in CCH was higher than in SCH (22.5 vs 17.7 g kg^–1). For both sites, NT showed the potential for an increase in C content (by 12–16%) relative to CT only in the 0–10 cm topsoil. Microbial-available C pool (mineralized for 180 days of soil incubation) was most sensitive to tillage systems, unlike unchanged particle-size pools. Specifically, it increased from CT to NT for CCH (by 7–16%), but it showed a decreased trend for SCH (by 11–29%), possibly due to the worsening of soil aeration in the periodically flooded regime. Gradient boosting machine models accurately predicted the spatial distribution of topsoil C content (R² = 0.99) and its microbial-available pool (R² = 0.78%) across the farmland area. The mutual drivers of both parameters were topography (elevation) and vegetation distribution (near-infrared surface reflectance). These outcomes are useful for developing site-specific management strategies to effectively restore C stocks in Chernozem soils.

In view of the continuing human expansion in Antarctica, it is crucial to implement a wide range of measures to effectively protect the natural environment and uphold the fundamental principles of the Antarctic Treaty system. Soil is the most important component of all terrestrial ecosystems, which plays a crucial role as the spatial basis of ecosystems. Despite the considerable research performed in different sectors of Antarctica, soils and soil-like bodies of Antarctica remain poorly investigated. The aim of this study is to investigate the processes of biogenic accumulation of substances and biogenic-abiogenic interactions in the soils of the Pravda Coast and the Haswell Archipelago, East Antarctica — vicinities of the Antarctic station Mirny. Field observations and laboratory analyses were conducted, focusing on determining the chemical composition and levels of organic matter in the soils. It was found that the soils exhibit a moderately acidic to near-neutral pH. High levels of organic carbon accumulation were recorded on Haswell Island, influenced by ornithogenic factors. Unlike most soils in East Antarctica, these soils display a presence of humus-like plasma. The soils studied are characterized by low (or moderate) levels of contamination, according to Igeo (geoaccumulation index); however, an increase in pollutant accumulation rates is observed in ornithogenic habitats and on the surfaces of peat horizons.

Introduction. The study of natural levels of hydrocarbons (HCs) content in soils is an urgent task, the solution of which will help to objectively assess the level of anthropogenic contamination of soils and timely limit the processes of extraction, processing, and transport of petroleum HCs. The analysis of HCs content in background soils will make it possible to reveal the regularities of their accumulation in the Arctic and Subarctic regions, taking into account the landscape and geochemistry of the areas. Materials and methods. Representative samples of the main soil types were selected using the route method, taking into account the peculiarities of soil cover formation in different landscapes. The concentration of HCs in the samples was determined in hexane extracts based on their fluorescence intensity. Results. The studies have shown that HCs accumulation and distribution in soil profiles are influenced by various factors such as soil genesis, relief, organic matter content, and physical clay. The highest HCs concentrations were observed in soils of accumulation landscapes on loamy sediments (Retisols), and the lowest in soils of eluvial landscapes on sands (Podzols). HCs profile differentiation is also more pronounced on loamy soils and less so on sandy soils. The results obtained allowed updating the existing database and mapping the HCs distribution in the background soils of the European Arctic and Subarctic. Limitations. The limitation of the study is related to the fact that only background soils at a distance of at least 1 km from railways and motorways, 5 km from settlements and 10 km from industrial plants were sampled. In this paper, only natural HCs were analysed, without considering other classes of organic and inorganic compounds. Conclusion. The data on the concentration of natural HCs in different background soils of the European North-East of Russia with respect to landscape-geochemical peculiarities have been obtained. The results provide an opportunity to assess the possible level of contamination of soils of the European Arctic and Subarctic. The HC content in organogenic horizons is shown to be characterised by a high accumulation capacity and act as an integral indicator of the aerotechnogenic load on the soil cover. Threshold values of HCs concentration are proposed for the studied soils, which are in a wide range from 3.4 to 40 mg/kg and can be used for ecological and hygienic assessment of high latitude soils.

The importance of research to assess the impact of potentially toxic trace elements (PTEs) on the environment and the importance of environmental monitoring, taking into account the natural variability of soil properties, shaped the aim of our study: to determine the background concentrations of PTEs in different soil profiles in the European Northeast, specifically in the Republic of Komi in Russia, taking into account the landscape and geochemical characteristics of the area. We analysed 173 soil samples from five main soil subtypes. The acid soluble forms of PTEs (Cu, Pb, Zn, Ni, Cd and Mn) were measured using an atomic emission spectrometer. We developed a database of PTE contents and created distribution maps for the Komi Republic using GIS technologies. The study found that PTE levels in soils from accumulative landscapes (such as depressions and floodplains) were generally higher than those in soils from eluvial landscapes (interfluves). We identified correlations between the levels of different PTEs and certain soil properties, providing insights into the biogeochemical migration patterns of these elements. The differentiation of PTEs in soil profiles was more pronounced in loamy automorphic soils and less so in sandy semi-hydromorphic and hydromorphic soils. Most soils, except floodplain soils, showed a clear eluvial–illuvial pattern of PTE distribution within the mineral soil profile, whereas floodplain soils showed a more uniform PTE distribution. The results of this study are useful for assessing the contamination levels of these soil types in high-latitude regions.

Various research issues related to soil organic matter in permafrost soils are still poorly investigated. At the same time, numerous investigations have shown the importance of permafrost soils, as they serve as a huge reservoir of organic matter. This work is aimed at the investigation of permafrost-affected soils in the southern part of the Yamal region, namely at the assessment of composition (fractional, elemental and molecular) of soil organic matter in topsoils formed under different biogeoclimatogenic conditions in tundra and forest tundra. Special attention was given to assessment of potential vulnerability of soil organic matter in the context of Arctic warming. Results showed the predominance of fulvic acids in the humus of the studied soils, which indicates mineralization risks in the humic substances system of Arctic soils under conditions of further warming. The ¹³C-NMR analysis of humic acids revealed that all the studied soils are characterized by higher portions of aliphatic groups of carbon and decreased portions of aromatic groups and revealed early stages of the humification process in studied soils. These results contribute to scarcely distributed research of soil organic matter in permafrost soils of the Arctic. Moreover, our research provided new data on the vulnerability of soil organic matter and its possible mineralization risks under pronounced climate change in the Arctic using the modern instrumental technique.

SOM stabilization rates were estimated in the soils of Antarctic region in case of influence of ornithogenic factor. Soils in large penguin clusters, near nests of Stercorarius sp., as well as soils located in geochemically subordinate positions (also often are visited by birds) were found to be characterized by an increased content of carbon and nitrogen with a rather narrow ratio of C/N. The pH values decreased in ornithogenic soils due to the organic acids that produced plants (mosses, Deschampsia antarctica) inhabit these soils and the decomposition products of the organic matter guano. The amount of CO2, in general, released over the entire experiment period is quite large for both ornithogenic and non-ornithogenic soils. CO2 emission rates were the highest in ornithogenic soils. Ornithogenic soils of the studied area are characterized by the most stabilized organic matter. Thus, the avifauna favors and increases the rate of the mineralization process by several times. An acceleration in the organic matter mineralization rate leads to an increase in nutrients amount available to plants, as in the case of the studied soils. The quality of initial SOM is of a great importance in post-ornithogenic environments. Therefore, further researches of CO2 emissions rates are needed to characterize post-ornithogenic dynamics and develop an approach to model this process.