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The state of the microbial community is an essential factor determining the processes of soil restoration of disturbed soils. Quarrying and mining complexes are valuable sites for studying soil formation processes. Four different quarries (gypsum, sand–gravel mixture, sand, and clay) of the Republic of Bashkortostan were surveyed to determine the status of the microbial community of post-technogenic soils. Amplicon libraries of the 16s rDNA gene were analyzed. It was shown that the microbial communities of different soil horizons of quarries differ significantly. According to the results of the analysis, quarry communities demonstrate differences in the microbial composition of different horizons, while in some cases, the upper horizon is richer.

Understanding the dynamics of SOM in different land use types is critical for effective land management and climate mitigation strategies. In this study, we investigated the differences in soil organic matter (SOM) content between forest and grassland landscapes in the mountainous zone of Republic of Bashkortostan, Russia. We collected soil samples from multiple locations under both land use types and analysed them for SOM content using standard laboratory techniques. The results showed that the SOM content varied from 2.2 to 15.3% under forest landscape with an average of 6.7% and was characterized by high variability (51.8%). The SOM concentrations under grassland ranged from 2.1 to 6.5% with an average of 3.2%, while the coefficient of variation was 31.8%. According to the classification, the average SOM value in forest soils was classified as “high”, while in grassland soils it was classified as “low”. Overall, the variability in SOM content within forested landscapes can be influenced by a range of factors, including topography, erosion, and redeposition of soil. These factors contributed to the complex patterns of SOM accumulation and decomposition observed in forest soils, and should be considered when evaluating the potential impacts of land use change on SOM. Our study highlights the importance of understanding the factors that influence SOM content in soils, and the need for careful management of land use systems to maintain or enhance soil fertility and productivity.

There is growing recognition that forest ecosystems are a key component in the global carbon cycle, and there is a clear demand for their study. This research is a comparative analysis of forest growing stock volume (GSV) and determination of annual growth in Bashkiriya Nature Reserve (Russia) for 1979 and 2015 using 8395 and 8405 observation plots, respectively. Also, we evaluated the spatial distribution and produced digital maps of the species and their GSV for each year. The results showed that pine and birch were the dominant species (60.5 and 24.8% of the area in 2015, respectively) and there were no significant changes in the area of stands during the 36-year period. We found that the GSV in the reserve had increased by an average of 23.2% over the 36-year period. Specifically, the total forest GSV increased from 7,678,960 in 1979 to 10,003,890 m3 in 2015, representing an annual gain of 0–1.5 m3/ha. The increase in GSV was mainly associated with an increase in birch and pine trees. The annual growth of GSV was determined as 1.8–2.1 and 1.4 m3/ha per year for pine and birch forests, respectively. However, these types of trees belong to the age categories of mature and overmature stands, i.e., with reduced intensity of GSV gain. Digital maps produced as part of this study provide a visual representation of the changes in forest spatial patterns and GSV over time, highlighting areas of the reserve where the stock has increased or decreased. This study leveraged a substantial dataset, which provided valuable retrospective insights into the dynamics of pristine forest ecosystems, allowing for the assessment of changes over a 36-year period. Overall, this study highlights the importance of the ongoing monitoring and assessment of GSV levels, especially in the context of rapidly changing environments and climates. [ABSTRACT FROM AUTHOR]

Land salinization is an up-to-date issue being broadly studied all over the world. In Russia, salinization processes are predominantly observed in the southern regions, where the main areas of arable land are situated. This research is devoted to mapping of saline lands with the help of satellite data. The study was performed on a 100-hectare plot in the Trans-Ural steppe zone (Republic of Bashkortostan, Russia). A correlation was determined between the level of soil salinity and the main spectral indices associated with Sentinel-2A satellite data. Regression models used 5 salinity indices, vegetation index NDVI, and values of soil conductivity. Linear, quadratic, and logarithmic functions were used. By calculation, the salinity index 5 (G×R)/B demonstrated the best correlation values with the salinity level of (R=0.88, R2=0.77) while using the quadratic function. The vegetation index NDVI revealed no correlation, owing to the poor development or dried-up condition of vegetation. On the basis of the developed regression models, salinity maps are drawn, in which the areas of solonchak complexes are defined.

This article aims to explore the use of machine learning (ML) methods for mapping the distribution of mercury (Hg) content in topsoil, using the city of Ufa (Russia) and adjacent areas as an example. For this purpose, a soil dataset of 250 points sampled from a 0–20 cm depth on different land uses, including residential, industrial and undisturbed (forests and parks), was used. Random Forest (RF), Extreme Gradient Boosting (XGboost), Cubist and k-Nearest Neighbor (kNN) ML techniques were employed to model and map the Hg concentrations. We used remote sensing data (RSD) and topographic attributes as explanatory variables. ML models were calibrated and validated using the leave-one-out cross-validation approach. The Hg content varied from 0.005 to 0.58 mg/kg and was characterized by very high variability. According to the MAE and RMSE metrics, the RF method resulted in the most accurate spatial prediction for the Hg content (0.029 and 0.065 mg/kg, respectively), while the XGBoost approach showed the lowest prediction efficiency (0.032 and 0.073 mg/kg, respectively). The results showed that the slope map, spectral index MSI and Sentinel-2A band B11 were the key variables in explaining the variability of Hg content. We found that higher uncertainty values of soil Hg were found in croplands, urban residential and industrial areas, which supports the view that spatial modelling of HM in urban landscapes is challenging. The present study provides insights into the potential of digital soil mapping techniques in combination with RSD and terrain variables for identifying areas at risk of Hg contamination in urban areas, which can inform land-use planning and management strategies to protect human health and the environment. [ABSTRACT FROM AUTHOR]

The problem of salinization/spreading of saline soils is becoming more urgent in many regions of the world, especially in context of climate change. The monitoring of salt-affected soils' properties is a necessary procedure in land management and irrigation planning and is aimed to obtain high crop harvest and reduce degradation processes. In this work, a machine learning method was applied for modeling of the spatial distribution of topsoil (0–20 cm) properties—in particular: soil organic carbon (SOC), pH, and salt content (dry residue). A random forest (RF) machine learning approach was used in combination with environmental variables to predict soil properties in a semi-arid area (Trans-Ural steppe zone). Soil, salinity, and texture maps; topography attributes; and remote sensing data (RSD) were used as predictors. The coefficient of determination (R2) and the root mean square error (RMSE) were used to estimate the performance of the RF model. The cross-validation result showed that the RF model achieved an R2 of 0.59 and an RMSE of 0.68 for SOM; 0.36 and 0.65, respectively, for soil pH; and 0.78 and 1.21, respectively for dry residue prediction. The SOC content ranged from 0.8 to 2.8%, with an average value of 1.9%; soil pH ranged from 5.9 to 8.4, with an average of 7.2; dry residue varied greatly from 0.04 to 16.8%, with an average value of 1.3%. A variable importance analysis indicated that remote sensing variables (salinity indices and NDVI) were dominant in the spatial prediction of soil parameters. The importance of RSD for evaluating saline soils and their properties is explained by their absorption characteristics/reflectivity in the visible and near-infrared spectra. Solonchak soils are distinguished by a salt crust on the land surface and, as a result, reduced SOC contents and vegetation biomass. However, the change in saline and non-saline soils over a short distance with mosaic structure of soil cover requires high-resolution RSD or aerial images obtained from unmanned aerial vehicle/drones for successful digital mapping of soil parameters. The presented results provide an effective method to estimate soil properties in saline landscapes for further land management/reclamation planning of degraded soils in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

In this study, we examined the influence of long-term conventional tillage on the water-physical, chemical properties, and composition of the organic matter of chernozems. The study has been conducted on an arable plot subjected to water and wind erosion in the Pre-Ural steppe zone (Republic of Bashkortostan, Russia). Soil samples were collected from non-eroded and eroded arable plots as well as from an adjacent pristine forest windbreak. Key structural fragments of soil organic matter under different land use types were identified and quantified using 13C-NMR spectroscopy. The results showed that the water-physical properties deteriorated in agrochernozems: the number of valuable soil aggregates decreased and the soil bulk density increased, which may limit the growth of crops. The soil organic matter content for the different samples varied in the following direction: arable non-eroded > forest windbreak > arable eroded. It has been found that long-term plowing by conventional methods decreases aliphatic and increases aromatic structures in soils. As a result of the reduced inputs of plant residues, the processes of humification slowed down compared to unplowed soils. To increase soil fertility and carbon sequestration potential, it is necessary to stop degradation processes and implement conservation tillage practices. [ABSTRACT FROM AUTHOR]

The morphological, water-physical and chemical properties, basal respiration of the southern chernozem (Chernozem Haplic Endosalic) and erosional sediment in the Trans-Ural steppe zone (Republic of Bashkortostan, Russia) were studied. The surface soil horizon significantly differs from the sediment by the better structure and water aggregate stability. The particle size distribution of the sediments, due to erosion, contains more silt and clay fractions compared to the slope soil. It indicates a great potential for the carbon saturation of the soil which is limited by degradation. The slope soil is slightly saline, the type of the salinisation is sulfate with the participation of hydrocarbonates. The СО2 emissions, the organic carbon and alkaline-hydrolysable nitrogen content is low; and significantly lower than in the erosional sediment, but the content of exchangeable cations and water-soluble salts is higher. The structural composition of the humic acid (HA) extracted from the soil and erosional sediments was determined by 13C NMR spectroscopy. Aliphatic structural fragments predominate (65%) with a maximum signal level in the area of C, H-alkyls in the HA of the surface horizon. In the HA of the erosional sediment, the proportion of aromatic structural fragments is higher (up to 59%), which is associated with the processes of hydrolysis and condensation. In the HA of the slope soil, the formation of predominantly C, H-alkyls, oxygen-containing groups, including carboxyl ones, takes place. Differences in the composition of the structural fragments and functional groups of the soil and sediment HA are due to the different stability of the organic matter under conditions of the development of the soil erosion processes. [ABSTRACT FROM AUTHOR]

Global climate change is a fact that affects all components of the environment. The main aim of this research was to conduct the retrospective monitoring of soils in the Trans-Ural Steppe Zone (Russia) and the analysis in changing of key climatic parameters for the periods 1937-1982 and 1982-2019. We investigated average temperatures and precipitation (monthly and annual) using archived data from a nearby weather station, as well as data from NASA and weather forecast websites. We identified a decrease of soil fertility and an increase in alkalinisation processes over the past 37 years for the studied area. Comparison of these periods showed an increasing the average monthly and annual air temperatures (on 1.4°C) and a decrease in the amount of precipitation in the summer (on 4.4 mm) period. We found that a more arid climate accelerates the rate of soil salinization due to the active evaporation of groundwater. Nevertheless, in some areas there were found the soil desalinization due to the change in the hydrologic regime and lowering of the groundwater level. In general, the climate changing in the studied region is consistent with global warming trend. Increased average annual temperature and reduced precipitation in summer period contribute to aridization of the region. Such conditions will more restrict soil fertility due to development of salinization and desertification processes. [ABSTRACT FROM AUTHOR]

The article discusses the valuation of ecosystem services in connection with the economic activity of the Russian Federation in the Arctic zone. It also considers the categories of ecosystem services in general and the assessment of ecosystem services in the Arctic in particular. The article also considers types of negative impacts on the Arctic ecosystems, their assessment, and investment risks existing in ecosystem services. It is shown that the application of the methodology and ecosystem services contributes to the adequate assessment and creation of a hierarchical classification of "usefulness" and "benefits" for society derived from the existence, use, and non-use of ecosystems. The concept of Arctic ecosystem services consists of three components: identification, monetisation, and ecological risk assessment. Identification, classification, and initial assessment, mainly at the qualitative level, allow us to determine and classify services for further improvement of life quality and regulation of socio-economic effects of environmental changes. Quantitative assessment is related to the identification of the degree of ecosystem service amenability. The example of the Arctic ecosystems shows that the possibility to assess and the accuracy of the assessment can be quite different and largely depends on the type of service. The analysis of possible ecosystem services and their relationship with the quality of life in the Russian Arctic indicates significant investment risks. [ABSTRACT FROM AUTHOR]

In the present study, we evaluated the effects of surface application and plowing of phosphogypsum and turkey litter to a depth of 20 cm on the erodibility of clay-illuvial agrochernozem (Luvic Chernozems (Aric, Pachic)) in the Southern Cis-Urals (Republic of Bashkortostan, Russia). Under laboratory conditions, 1°, 3°, and 7° slopes were modeled. Soil loss, runoff onset time, and turbidity were measured with a rainfall simulator. Particle size distribution and total organic carbon were measured. Under simulated heavy rainfall (360-420 mm h-1) for 30 min, the untreated control had the highest soil loss (28.9 t ha-1). Separate and combined introductions of phosphogypsum and turkey litter significantly increased soil resistance to water erosion. Co-introduction of the amendments strengthened this effect especially when the phosphogypsum to turkey litter ratio increased from 1:10 to 1:2 at the higher dose (60 t ha-1). The turbidity of the runoff from a 1° slope reached a small peak within the first 3 min then gradually decreased thereafter. At 3°, the turbidity remained nearly constant over time and was uniformly distributed. At 7°, the turbidity sharply increased then gradually decreased and its distribution was a deformed bell. Washed-out (trapped) sediments from all treatments and slopes had relatively more very fine sand, silt, and clay and a slightly higher total organic carbon content than the original soil. Phosphogypsum and turkey litter wastes may be effective anti-erosion amendments and potential fertilizers because they increase flocculation, improve the structure, and enrich the organic matter and nutrient content of the soil. [ABSTRACT FROM AUTHOR]