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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. [ABSTRACT FROM AUTHOR]

Although Antarctic soils are usually described as weakly developed, recent studies indicated the significant variability in soil forming conditions across the sixth continent as well as considerable diversity of soils. The identification of pedogenetic processes in Antarctica is crucial for understanding not only the current state of its environment, but also for better understanding of soil development on Earth through time. Our study provides a detailed investigation of micromorphological features and molecular composition of organic matter of soil and soil-like bodies of remote areas of East Antarctica - Larsemann Hills and Bunger Hills, which are characterized by harsh environmental conditions. Studied soils showed predominantly coarse structure and low organic carbon content, alkaline to almost neutral pH range. Thin sections of studied soils were characterized by predominance of grains of quartz, feldspars, and other primary minerals with angular shapes indicating relatively weak degree of their alteration. All studied humic substances are characterized by the predominance of aliphatic structures. Moreover, it was observed that studied humic acids contains significant amounts of carbohydrates, polysaccharides, esters and amino acids and hydrophilic fragments predominate. Organo-mineral interactions were mostly connected with development of biofilms in the topsoil horizons with the maximal biological activity among studied soils. [ABSTRACT FROM AUTHOR]

Although Antarctica is considered one of the most pristine areas on Earth, an accelerating human presence in this remote continent, such as scientific operations and functioning of numerous scientific stations, logistics, and tourism activities, has increased the risks of environmental impacts in recent decades. During the 63rd Russian Antarctic expedition, 42 samples from topsoil horizons were collected from Larsemann Hills, Mirny station, and Fulmar Island, Eastern Antarctica. The purpose of this work was to analyze the accumulation levels 8 trace elements and to assess possible environmental risks associated with contamination of Antarctic soils. Various human activities have been found to be responsible for increase of metal levels in studied Antarctic environments. Our study also revealed a specific role of ornithogenic factor and moss cover in distribution of contaminants in severe conditions of Eastern Antarctica soils. Ornithogenic soils were characterized by higher rates of accumulation of some trace metals and metalloids (especially zinc and copper) compared with other investigated "pristine" sites without significantly visible traces of guano inputs. In general term, obtained geoaccumulation index for trace elements in all samples were under or slightly above the 0 level, indicating low to moderate pollution of the studied soils. Results of principal component analysis revealed the necessity for further detailed research on interactions of trace metals with soil organic matter for better understanding of their biogeochemistry in the Antarctic environment. Although most of contaminated sites were found in anthropogenically affected areas, accumulation of some elements in guano-derived and moss materials were associated with higher values for soil pollution indices in natural soils, as well. [ABSTRACT FROM AUTHOR]

Permafrost soils differ significantly from other soils because they serve as a huge reservoir for organic carbon accumulated during the Quaternary Period, which is at risk of being released as the Arctic warms. This study aimed to characterize existing carbon pools, delineate possible mineralization risks of soil organic matter and assess microbial communities in the tundra and forest-tundra permafrost soils of the southern Yamal region of Russia. The profile distribution of carbon, nitrogen and the C:N ratio showed non-gradual changes with depth due to the manifestation of cryopedogenesis in soil profiles, which lead to cryogenic mass transfer. Mean carbon stocks for the study area were 7.85 ± 2.24 kg m-2 (0-10 cm layer), 14.97 ± 5.53 kg m-2 (0-30 cm) and 23.99 ± 8.00 kg m-2 (0-100 cm). The analysis of the humus type revealed a predominance of fulvic type and low-molecular-weight fragments in the fulvic acid fraction, which indicates high mineralization risk of humic substances under Arctic warming conditions. The taxonomic analysis of soil microbiomes revealed 48 bacterial and archaeal phyla, among which proteobacteria (27%) and actinobacteria (20%) were predominant. The pH range and nitrogen accumulation were the main environmental determinants of microbial community diversity and composition in the studied soils. [ABSTRACT FROM AUTHOR]

Chile is a well-developed agricultural country, which is faced with the problem of agricultural soil contamination with metals, such as Cu, Cd, Pb and Zn, and metalloids (As). These elements can be retained by soils through different mechanisms, i.e., complex-forming with organic matter or occlusion within organic matter. That is why studying soil contamination should also be accompanied by detailed investigations of the soil organic matter composition. Soil organic matter is crucial for plant growth since its decomposition releases nitrogen, phosphorus and other nutrients available for the plants. 13C nuclear magnetic resonance spectroscopy, providing crucial data on carbon functional structures diversity, can also be used to study changes in the soil organic matter (SOM) during decomposition and humification. This study is aimed at investigating the molecular composition of the soil organic matter in the agricultural soils of urbanised areas of central Chile using 13C nuclear magnetic resonance (NMR) spectroscopy. The studied soils were characterised by almost neutral pH values and organic carbon contents from 1.7% to 5.2%. The results showed that soils with an increased content of the total organic matter demonstrated an increased portion of aromaticity and a decreased portion of aliphaticity. Most of the investigated humic acids show the highest peaks centred at 125 ppm, which can be tentatively assigned to aromatic alkene structures. The relatively high stabilisation rate of the organic matter in the studied soils can be explained by the mineralisation of its peripheral part, which, in turn, is explained by the decreasing C/N ratio values. The humic substances of the studied agricultural soils of central Chile showed a high average content of aromatic carbon, which is also typical for subboreal soils. [ABSTRACT FROM AUTHOR]

Precision agriculture requires a wide sampling procedure to determine the spatial variability of soil properties for adequate assessment of soil state and appropriate recommendations. Electrical geophysical methods (i.e. vertical electrical resistivity sounding) allow performing rapid measurement of soil electrical properties directly from the soil surface to any depth without any mechanical disturbance of soil cover. Soil electrical properties are linked with many soil properties and could improve the quality and spatial coverage of soil surveys. The results obtained in our study using vertical electrical resistivity sounding confirmed the hypothesis of a high correlation between electrical resistivity and such soil properties as carbon and nitrogen content and silt content. The highest correlation (r > 0.9) was found for electrical resistivity and carbon content. It was also confirmed that significant correlations between electrical resistivity and soil properties are found mainly when soil properties are highly ranged. Perspectives for the applied method lie at the relationship between electrical resistivity and soil properties, such as texture class, clay content, carbon content, and cation exchange capacity. The results obtained in this work could be useful for complex precision agriculture, creating maps of agricultural soils, adequate methods of plant growth, and other issues of precision and conventional agriculture. [ABSTRACT FROM AUTHOR]

This study was aimed to investigate the electrical resistivity in soils and permafrost of various ice-free areas of Antarctica and Sub-Antarctica (from coastal Eastern Antarctica oases to Maritime Antarctica). Measurements of electrical resistivity of soil and permafrost strata were performed with a portable device LandMapper. It was found that the permafrost table depth ranged 82 to106 cm in Bunger Hills, 95 to 122 cm in Larsemann Hills, 27 to 106 in Thala Hills, and 89 to 100 cm on King George Island and Ardley Island. Presence (and thickness) of organic layer and influence of snow patches melting were found the main reasons for differentiation of permafrost table depth in the studied ice-free areas. Anthropogenic disturbance at waste disposal sites resulted in more pronounced soil profile heterogeneity and formation of scattered electrical resistivity profiles. Permafrost layer was found less homogenous in the upper part of permafrost strata compared to the lower part. An application of vertical electrical resistivity sounding (VERS) may be very useful for evaluation of active layer thickness in Antarctic environments, especially when they are facing severe anthropogenic influence due to maintaining of numerous Antarctic research stations and logistical operations. [ABSTRACT FROM AUTHOR]

Floodplains are one of the most dynamic and youngest areas of the Earth's Quaternary surface. They are located in transitional conditions (land-ocean) of the permafrost zone of present and of particular interest for ongoing geochemical processes and soil/water balance. The soil thermal and water regimes of polar soils are crucial for the development of vegetation cover as well as production, accumulation and redistribution of organic matter. This work characterizes the hydrological properties of soils formed in Russian Arctic. The data showed differences in water holding capacity between soils formed in conditions of seasonal flooding (soil stratification, redistribution of organic and mineral matter through the soil profile) and those not influenced by flooding in Lena River Delta (gradual decreasing of water holding capacity as a function of depth). Both of the soil profiles from the Yamal Peninsula are characterized by a gradually decreasing water-holding capacity with depth. The hydrological regime characteristics were strongly related to the depth of the active layer. The intensity and rate of the thawing/freezing processes depends on the features of the hydrological regime. In this study, significant differences were noted in the soil characteristics of the two study areas. That is why the profile values of water-holding capacity differed among the study sites. The predicted global climate change and high sensitivity of Arctic ecosystems may lead to significant changes in permafrost-affected landscapes and may alter their water regime in a very prominent way, as permafrost degrades and lateral and vertical water flow in the basins of large arctic rivers changes. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine electrical resistivity peculiarities of tundra and forest tundra soils and soil-permafrost layers of the Yamal region. Measurements of electrical resistivity of soil and permafrost strata were performed with a portable device LandMapper (to a depth of 300-500 cm). These measurements allow determination of the values of apparent electrical resistivity of soils and permafrost at different depths and determination of the depths of the permafrost table on each key plot. It was found that there are several trends in vertical distribution of apparent electrical resistivity values. The first trend is a monotonous increase in electrical resistivity values to the depth. It may be explained by the increasing electrical resistivity within the soil depth in relation to the increase in permafrost density. The second trend is a sharp decrease replaced by a gradual increase in electrical resistivity values caused by changing of non-frozen friable debris to frozen massive crystalline rock. These differences were related to the type of landscape: lat lowlands composed of friable grounds underlain by permafrost or friable grounds with permafrost underlain by a rock crystalline layer. [ABSTRACT FROM AUTHOR]

The original version of the article unfortunately contained a mistake in Fig. 2, where numbers on the plot were not decoded. [ABSTRACT FROM AUTHOR]

Antarctic soils are known as very diverse in morphology, chemistry, texture and mineralogical composition. Differences in geographical locations and existence of so-called Antarctic oases, which are isolated from each other by ice sheets and snow masses causes significant pedodiversity of Antarctic continent. In severe climatic conditions of Antarctica birds play an important role in transportation of organic matter to the coastal landscapes. This study is aimed to investigation of ornithogenic factor in soil formation on King George and Ardley islands (South Shetland Islands). Our work revealed that redistribution of guano components affects significantly the speed of soil cover spatial development and formation of new polypedons of soils in environments of rookeries. Analysis of mesomorphological organization of soil aggregates showed different rates of association between guano remnants and mineral grains in humus horizons, which is caused by variability in both fine earth content and guano decomposition rate. In this study, 13C-NMR spectroscopy was performed to analyze soil organic matter of Ornithosols, Post-Ornithosols and Cryosols not affected by bird activity. We found that the humic acids (HAs) of the cryoturbated, buried areas had lower amounts of alkyl aromatic and protonized aromatic compounds. In contrast, the HAs from the surface layers contain less alkyl carbon components. Our data showed that the portion of aromatic compounds is little higher in soils under materials transported by birds compared to soils under mono species of bryophyta or lichens communities. This is probably caused by the fact that birds use mainly remnants of Deschampsia antarctica (which contains increased portion of phenyl-propanous organic precursors) for nest building. The free-radical content was higher in the surface layers than in the buried layers due to the presence of fresh organic remnants in superficial soil samples. Measurements of electrical resistivity of soil and permafrost layers were performed with a portable device LandMapper with vertical electrical resistivity sounding approach (VES). Permafrost table depth in studied soils ranged from 89 to 100 cm. Cryoturbation process and supra-permafrost accumulation of moisture which are widespread in the studied soils, lead to cryogenic mass transfer, heterogeneity of soil mass, and complication of the profile distribution of electrical resistivity values. The character of parent material determines temperature and water regime in soil, rate of cryopedogenesis, dynamics and thickness of active layer and permafrost table. This study was supported by RFBR, grant 18-04-00900 "Ornithogenic soils of Antarctica: formation, geography, biogeochemistry and bioindication". [ABSTRACT FROM AUTHOR]