The properties of soils, C-biomass, and the structure of humic acids of arable chestnut soils of Western Transbaikalia were studied. The objects of this study were arable chestnut soils of the southern basins of Western Transbaikalia (Tugnuyskaya basin, Selenginskaya basin, Ivolginskaya basin). For comparison, arable soils were studied in pairs with virgin soil analogues. Arable chestnut soils are characterized by low fertility: low humus content of 0.98 ± 0.07%, low total nitrogen content of 0.08 ± 0.01%, arable horizon thickness of 21.33 ± 2.31 cm, and a light loamy granulometric composition. During the growing seasons, the average biomass carbon accumulation rates in chestnut soils were 35.77 ± 3.09 mg C/100 g of soil. The share of C-biomass in the total stock of soil organic carbon for the studied soils is up to 2.5%. The content of aliphatic carbon in arable chestnut soil is also lower than in virgin soil. The content of the amino group and methoxyl group carbon in virgin soil is 7.9 ± 0.14%; in arable soils this indicator is almost two times lower. The amount of carbon in carboxyl groups is 15.5 ± 0.42% in arable chestnut soils; in virgin soils the indicator was 12.55 ± 0.92%. Spectrum analysis of 13C-nuclear magnetic resonance (NMR) spectroscopy of humic acids (HAs) in soils can provide important information on the chemical composition and structural features of organic matter in soils. For arable and virgin chestnut soils of Transbaikalia, such an analysis can reveal differences associated with the use of land in agriculture. Aliphatic carbon in the HA of arable soil is expressed less strongly, which indicates a greater role of aromatic carbon in its macromolecular structure. A pattern is observed: in arable lands the content of aliphatic compounds is lower than in virgin lands. It has been found that agricultural tillage leads to a change in the molecular structure of humic acids, which is expressed in an increase in the proportion of aromatic carbon in arable soil. In the elemental composition of HA in cultivated chestnut soils of Transbaikalia, the carbon content is higher and the hydrogen content is lower compared to virgin analogues. The high hydrogen content in virgin soils leads to relatively developed lateral carbon chains in HAs. In cultivated chestnut soil, the HA macromolecule contains more nitrogen (2.9 at %) than in virgin soil (2.7 at %). The atomic ratio H : C in cultivated chestnut soil was 1.0, while in virgin soil it was 1.1. In cultivated variants, the degree of benzenoid content (BC) is 22.5, while in virgin soil the indicator is lower at 16.4. It was established that the elemental composition of cultivated chestnut soils is characterized by a more condensed structure compared to virgin soils.

The interannual structure of four coenopopulations (CPs) of Dracocephalum peregrinum L. located in the steppe communities of Siberia is considered. A range of ontogenetic spectra has been established: left-sided, centered, and bimodal. During the period studied, the ontogenetic spectra of all CPs show an accumulation of individuals of the pregenerative period; the proportion of the generative fraction in the CPs of Tuva increases (CP2, CP3), and those of Gornyi Altai (CP1) and Khakassia (CP4) decrease. Changes in the structure of the spectra occur for various reasons: a decrease in anthropogenic load (CP1–CP4), an increase in the amount of precipitation (CP2, CP3), the growth of shrubs in the cenosis (CP3), and microconditions of the local area (CP4). Demographic and development rate indicators confirmed the rejuvenation and stability of the studied CPs.

The application of camera traps to study the fauna and population of terrestrial vertebrates of the mountain wastelands of the Zeiskii State Nature Reserve, which occupies the eastern part of the Tukuringra Ridge, is described. An original method of counting mammals using camera traps was used, where the final indicator is the load on the area of the photo–video recording zone per unit of time, expressed as the number of individuals per unit area (Podolsky et al., 2020). Extreme habitat conditions (lack of moisture during the growing season, frequent storm winds, etc.), along with seasonal migrations and periodic food concentrations, determine the characteristics of the animal population of mountain wastelands and the difficulties of studying it; the use of standard observation methods is insufficient. Nine cameras were installed: eight in mountain tundra with clumps of dwarf pine, and one in the subalpine Ayan spruce forest, at the intersection of animal trails. For mammals, population densities estimated from camera trap data were compared with multi-day censuses and other standard methods to assess the feasibility of using the method for censuses of different species. It has been shown that, in mountain wasteland conditions, it is optimal for recording the main parameters (population density, timing) of summer–autumn food concentrations of brown bears (Ursus arctos) and is also applicable for recording several other species of animals: the white hare (Lepus timidus), lynxes, and probably wolverines. The proposed method of accounting on bare mountains is not applicable to sable (Martes zibellina), the red squirrel (Sciurus vulgaris), and the Asian chipmunk (Eutamias sibiricus). The population density of the mentioned species, calculated using camera trap data, turned out to be several orders of magnitude lower than that obtained using standard methods. The described method is also not suitable for determining the number of birds. At the same time, the analysis of the footage from the installed cameras allowed us to expand the list of bird species regularly visiting the mountain wastelands, as well as to supplement the list of the avifauna of the Zeiskii Reserve: the Eurasian whimbrel (Numenius phaeopus) and the Asian rosy finch (Leucosticte arctoa) were noted for the first time. The natural features of the upper altitude zones of the Tukringra ridge, the specifics of organizing research in extreme conditions, the technical capabilities of modern automatic cameras, and the developed census methodology determine the significant prospects for using camera traps to study the fauna and population of animals and birds of the mountain wastelands of the Zeiskii State Nature Reserve.

The state of the invasive species Dreissena polymorpha (Pallas) was studied in Ivan’kovskoe (Ivan’kovo) Water Reservoir in 2018–2022 to obtain the quantitative parameters of the mollusk development at the larval and definitive stages in all pleses (moderately wide stretches of a water body that is deeper compared to the surrounding waters) of the water reservoir during different seasons, as well as to show the interannual dynamics of their population size and spatial distribution. In the Ivan’kovo Water Reservoir, the southern invasive species Dreissena polymorpha (Pallas) has adapted rather successfully and has occurred continuously in the subsaline water conditions with a persistent lack of dissolved oxygen in summer in the near-bottom waters, which caused a shift in the mollusk niche down to a depth of 4 m; the mussel did not occur in silty biotopes. Range expansion of the southern immigrant D. polymorpha to the northern regional water bodies is influenced by climate warming, which prolongs the reproductive process of this mollusk. Currently, the end dates of mussel spawning in the Upper Volga water reservoirs approach those in southern water bodies. Eutrophication enhancement due to climate changes may pose a serious threat to Ivan’kovo Water Reservoir. Overall, the mussel population (adult mollusks + veligers) play a significant role in the process of self-purification of the water reservoir.

The steppe marmot (baibak) is one of the typical rodents of the Eastern European forest–steppe and steppe. In the mid-twentieth century, European populations of the species were on the verge of extinction, but then, thanks to conservation measures and reintroductions, the population of boibak and range were largely restored. This work collects and presents data on two restored marmot colonies in the forest–steppe of European Russia. The research was carried out in the Central Black Earth Nature Reserve (Streletskaya steppe, two sections) and in the Volga Forest–Steppe Nature Reserve (Ostrovtsovskaya forest–steppe, three sections). The number and age composition of marmots are described. Maps of settlements with burrows and trails of marmots have been compiled; for each burrow the coordinates and type (temporary or permanent) are indicated. The population density and the number of burrows per marmot were calculated. In total, 12 marmots live in the Streletskaya steppe: ten on the "Pasture" site and two on the "Restored Steppe" site. In the first area, seven adult and three young marmots were noted, in the second, two adult marmots. Here, the reintroduction of the boibak was not entirely successful. From 2015 to 2023 the number of marmots decreased sharply, from 38 to 12 individuals, and the area of the inhabited territory fell from 10 to 3.7 hectares. In the Ostrovtsovskaya forest–steppe, 48 marmots (eight families) were recorded, of which 40 were in the first area (six families), two were in the second area (one family), and six were in the third area (one family). Of the 48 individuals, 29 (61%) are underyearlings. The reintroduction of the bobak into the Ostrovtsovskaya forest–steppe was relatively successful: the total number of animals is comparable to the number of marmots initially released (48 and 64).

The use of background indicators for monitoring the content of nutrients in surface and groundwater in the steppe and forest–steppe zones of the Russian Plain is substantiated. Approaches to determining the background content of nutrients are proposed. The peculiarities of the formation of the runoff of nutrients during the flood period and summer–autumn and autumn–winter periods are revealed. It is advisable to use the results obtained to assess anthropogenic changes in the content of ammonium nitrogen, nitrate and nitrite nitrogen, and mineral phosphorus in the surface water and groundwater, as well as in wastewater. It is shown that it is advisable to adjust the standards for the content of nitrates and ammonium nitrogen in river and waste waters taking into account the level of the regional natural and anthropogenic background.

Research on the Caspian region has been conducted for over 20 years under the auspices of the Framework Convention for the Protection of the Marine Environment of the Caspian Sea (Tehran Convention). It aims to protect not only the water area of the Caspian Sea, but also areas of land located directly adjacent to it from negative impacts. For the first time, based on the concept of Land Degradation Neutrality (LDN), this work presents the results of a comparative assessment of land conditions for the coastal areas of five states: the Republic of Azerbaijan, the Islamic Republic of Iran, the Republic of Kazakhstan, the Russian Federation, and Turkmenistan. The approach implemented made it possible to identify the main trends in land dynamics in the region under consideration, including for individual countries and regions for different periods of observation. The results are presented in cartographic form. It has been established that most regions of the Caspian region are characterized by a deterioration of the current situation associated with the intensification of degradation processes, and the main “hot spots” of desertification are described. At the same time, the dynamics of land degradation in the Caspian region are multidirectional in individual regions and observation periods. Selecting different comparison periods and baselines can help track changes in land conditions over time and identify peaks of improvement and deterioration.

This study is concerned with a conjugate analysis of the productivity of herbaceous and woody plants from various landscape communities, such as the typical steppe, salinized, woody, and agricultural, in arid conditions of southwestern Siberia performed using different methods; specifically, remote sensing (analysis of the vegetation indices NDVI) and dendrochronological (analysis of the stem growth increment in width in Scotch pine (Punus sylvestris L.) from extrazonal ribbon coniferous forests (bors)). Climate factors were established that govern the dynamics of NDVI and the radial growth increment in trees of the steppe zone, which include the limiting impact of summer temperature and the positive effect of atmospheric precipitation of the previous winter and current summer seasons. Analysis of the vegetation indices and the radial growth increment in trees showed the occurrence of a moderate relationship between them, in that NDVI of May and July of the herbaceous communities (Stipa spp.-Volga fescue and arable lands) correlate with a width of annual rings in trees. The width of the pine radial growth increment in the arid steppe was found to depend on the NDVI value of the crown of tree stands in May from two years before.

Over the past half century, global warming has become one of humanity’s serious problems, which is accompanied by ecosystem reactions, that is, climate aridization and subsequent desertification of landscapes. In southeastern Transbaikalia (Dauria) and the bordering regions of Mongolia and China, the problem is intensified by regionally occurring cyclical (approximately 30-year) humid (transgressive) and arid (regressive) climate phases. In these territories there are more than 500 drainless salt and brackish lakes of various chemical compositions and varying degrees of mineralization. Naturally, all the ongoing climate changes are clearly reflected in the hydrology and chemical composition of these reservoirs and in the landscapes of lake depressions, including the soil cover. During the regressive climate phase, we conducted studies of the main types of soils in the lakeside depression of the pulsating chloride Lake Bab’e. Their morphology, particle size distribution, physicochemical and other properties, composition, and salinity chemistry were studied for the first time. It has been established that these soils form a genetically related series of saline soils: quasi-gley solonchaks of the chloride type of salinity–humus-quasi-gley saline soils–light humus saline soils. It was revealed that the formation of salt marshes is directly influenced by highly mineralized lake waters. Humus-quasi-gley saline soils formed in superaquatic positions are periodically affected by lake waters and are active only in the humid climate phase. Also, the research results indicated that in humus-quasi-gley and light humus soils, chloride–soda and soda-chloride salinization of the lower horizons was noted. The obtained materials will be necessary for monitoring saline soils and ecosystems of lakeside depressions of cyclically pulsating highly mineralized drainless reservoirs in the transboundary territories of Transbaikalia (Russia), Mongolia, and China during global and regional climate changes.

Using biogeographic approaches, the mapping of protected species of terrestrial vertebrates in the Republic of Kazakhstan was analyzed and carried out to identify places of high faunal diversity and assess the effectiveness of their protection by a network of specially protected natural areas. An analysis was made of the spatial distribution of protected species of terrestrial vertebrates by taxonomic groups (mammals, birds, amphibians and reptiles, 109 species in total) and their totality, as well as by protection status; places of concentration of protected species of vertebrate animals were established as priority for the protection of territories in the Republic of Kazakhstan and an assessment was made of the effectiveness of locating the existing network of specially protected natural areas. The maps were made using the grid mapping method, which makes it possible to compare the results obtained with other arid macroregions. The role of a number of reserves, national parks, and large reserves in the protection of biological diversity is shown. Recommendations for the development of a network of specially protected natural areas in order to preserve areas of high biodiversity, as well as the tasks of further research in this direction have been formulated and substantiated.