The structure and distribution of zooplankton of the Tsimlyansk Reservoir were studied in August–September 2018. It was found that the zooplankton abundance was halved in the upstream part of the reservoir (2.4 ± 0.8 g/m3) as compared to the zone near the dam of the Tsimlyansk hydroelectric power plant (1.2 ± 0.6 g/m3). Copepoda constituted 70% of the biomass. The Ponto-Caspian Heterocope caspia and the invasive species Calanipeda aquaedulcis, Thermocyclops taihokuensis, and Acanthocyclops americanus were abundant copepods. The dynamics of zooplankton abundance in the reservoir is analyzed for more than 65 years since its creation (1952–2018) based on the published data. A more than twofold (up to 2.1 ± 0.5 g/m3) increase in the community biomass was revealed in 2015–2018 as compared with the 40-year period up to 2013 (0.8 ± 0.1 g/m3). The trends in the dynamics of the zooplankton abundance in the Tsimlyansk Reservoir, including the importance of the Ponto-Caspian crustaceans and invaders from other regions, are discussed.

Today, population growth and demand for agricultural production have resulted in the significant damage to the natural ecosystem, including forests and rangelands, and have turned them into farmlands. Territorial land use changes can result in changes in chemical and physical features of soils, which in turn, may ultimately lead to land degradation. Understanding the effects of land use changes on soil features is very important as it helps with assessing the sustainability of natural ecosystems. Therefore, in the current study, we sought to compare changes in soil physico-chemical properties, soil deterioration index (SDI), soil erodibility factor (K factor) and the soil organic carbon (SOC) stock in three types of land use, namely: protected forest (PF), natural forest (NF) with common exploitation (overgrazing and fuel wood) and cultivated land (CL) in semi-arid regions in western Iran. Soil samples were randomly collected from 0–30 cm depths (16 + 18 + 18 at each land use, respectively; 52 samples in total). The soil texture, pH, exchangeable K, available P, total N, soil organic carbon and SOC stock were measured in soil samples. The findings indicated that in general, overgrazing with the exploitation of trees in the NF and changing the NF to CL caused a significant increase in sand (by 22.3–90.5%) and bulk density (6.1–9.16%) and a significant decrease in silt (4.34–13.56%), clay (2.36–13.5%) exchangeable K (37.68–50.63%), available P (15.58–27.42%), total N (22.2–55.5%), soil organic carbon (22.3–52.4%) and SOC stock (22.87–52.3%) (P < 0.01). The outcomes of multivariate analysis (RDA) indicated that CL correlated with sand, pH and bulk density, and EF correlated with most soil properties. The outcomes of SDI were indicative of a significant reduction in quality of soil (-5.5%) under CL, compared with NF (–21.5%) and EF (0.1%). The highest value of soil erodibility factor (K factor) was observed in the CL (0.260), and the lowest was at the PF (0.214). In general, the findings of this study showed that the exploitation of trees for fuel wood with overgrazing in the NF and after transformation of the NF to the CL caused a significant deterioration in the soil properties in the semi-arid region in western Iran.

The phytocoenotic characteristics of leymus-chinensis cenoses growing in soils of different types in the meadow–steppe, the floodplain–steppe, and the halophytic grasslands in the western Trans-Baikal region are considered. The botanical composition is found to consist of 28 glicophyte species, 17 halotolerant glicophytes, and 6 halophytes. It is determined that the genus Leymus contains three species: Leymus chinensis, L. buriaticus, and L. littoralis. The botanical composition of leymus stands in the westerm Trans-Baikal region includes 51 species, 20 families, and 40 genera. The species are predominantly assigned to the steppe complex based on different types of xerophytes belonging to the Asian type of distribution. Rhizome species are a major biomorph component; in addition, a significant proportion is composed of species with short life cycles. The variation in similarity between the leymus species compositions is weak to moderate due to the significant involvement of families and genera with low species richness. The primary production of leymus cenoses comprises 1029—2370 g/m2 per year. The aboveground phytomass is almost completely formed by Leymus chinensis. The biochemical composition, feed value, and protein ratio of edificator dry matter are influenced by the environmental opportunities for growth, while they generally correspond to the standard indicators.

The article discusses methods to assess the reliability of salt-transfer parameters that were previously calculated with models of the microdispersion, macrodispersion, and dissolution of salts, with a view to their further use in predictive assessments of the development of salt-transfer processes in irrigation systems. The evaluation included statistical methods with the Fisher and Student criteria with the subsequent determination of the systematic error. The most adequate models for objects of the eastern Ciscaucasia and the Saratov Trans-Volga regions are established. To use the salt-transfer parameters in forecast estimates based on their linear and nonlinear statistical dependences on the lithological structure of the aeration zone and its filtration properties, the corresponding multidimensional statistical equations are obtained.

The distribution pattern of the characteristics of spring–summer droughts during periods of increased and decreased annual wetting in 12 administrative entities of the south of European Russia in 1901–2018 are studied. During this time, four periods of different humidification conditions (alternating wetter, dry, wet and again dry periods) of different durations are well traced according to anomalies in the aridity index in seven regions: Kursk, Belgorod, Voronezh, Saratov, Volgograd, and Rostov oblasts and the Republic of Kalmykia. A desiccation period was noted in Samara and Astrakhan oblasts from the beginning to the middle of the 20th century. The desiccation period then gave way to a wetter one. The most frequent change of periods with different moisture conditions was observed in Stavropol krai, where five alternating periods were identified. It has been established that the frequency of spring–summer droughts is consistent with the long-term humidification conditions. According to the standardized precipitation index, it increases on average by 1.5 times in the dry period with a slight increase in drought intensity. The conditions of increased humidification observed in all of the examined administrative subjects in the second half of the 20th century were replaced by drier conditions at the beginning of the 21st century. The spread of more arid conditions began in the eastern oblasts. The development of the dry period in the 21st century is confirmed by the distribution of the NDVI vegetation index in the negative trend. In the absence of statistically significant aridization trends for more than a century, all of the considered oblasts of the south of European Russia undergo long, intracentury periods of aridization strengthening and weakening, which are characterized by significant differences in the frequency and intensity of spring–summer droughts.

The abundance of the saiga antelope (Saiga tatarica tatarica L., 1766) in the Northwest Pre-Caspian region has remained at an extremely low level over the past 20 years. Comparison of some biological parameters of the population for periods with different numbers of animals made it possible to reveal a number of low-population features. Thus, along with a decrease in the number of saigas (from 800 000 heads in 1958 to 4500 in 2016), its habitat area also decreased (from 60 000–70 000 to 2000–3000 km2, respectively), and a significant part of the population transitioned to a sedentary lifestyle in the protected areas of the Chernye Zemli ecoregion. A long-time deficiency of sexually mature males in the population (less than 10%) led to a decrease in its growth and, consequently, to a decrease in its number. At the same time, the total fecundity of females decreased (from 1.27 ± 0.25 calves in years of high abundance to 0.92 ± 0.39 recently) due to an increase in barrenness in different age groups caused by the lack of males in the population. Males prevail over females in newborns (51.9 and 48.1%, respectively). The increased weight of newborn saiga calves (100 g on average for both males and females) and their decreased mortality in the first days after birth (under favorable weather conditions) indirectly indicate the normal course of embryogenesis and a sufficient quantity and quality of feed. An increase in the proportion of sexually mature stags will lead to an increase in the population number, as the reproductive functions of the population practically did not change during the period of its depression.

Work on the study and adaption of the concept and methodological basis of land degradation neutrality (LDN) in the Kyrgyz Republic was launched in 2016 as part of a corresponding project. The Secretariat of the United Nations Convention to Combat Desertification (UNCCD) provided the country with a comprehensive set of indicators and information derived from an analysis of global satellite data reflecting key indicators of land degradation in the Kyrgyz Republic. This data set was analyzed at the national level via comparison with data from studies and a series of meetings and consultations with relevant state and nonstate institutions. As a result of the research, a team of national experts was able to compare international (UNCCD data) and national land-use indicators. In particular, a comparative analysis was carried out based on categories of land resources. Nevertheless, the work requires further detailed verification of international and national land use indicators with alternative satellite data, as well as special field studies.

The Aral disaster led to the almost complete loss of the Aral Sea. After the construction of the Kokaral dam in 2005, it became possible to rescue the northern part of the Aral Sea (the Little Aral). Due to natural (climatic) and anthropogenic causes, the flow of the Syr Darya River increased in the beginning of the 21st century, its hydrological regime changed dramatically, spring-summer floods decreased, and winter discharges significantly increased. All of these changes strongly affected the dynamics of floodplain ecosystems and landscapes. A comprehensive assessment of current trends in the dynamics of ecosystems and landscapes under changing environmental conditions was attempted in the study. The study was carried out based on field material with data from remote sensing of the Sentinel 2 satellite, as well as climatic and hydrological materials. The office and field data were analyzed according to the developed methodology developed by Zh.V. Kuzmina and S.E. Treshkin for the assessment of transformations in ecosystems and landscapes from natural and hydrotechnical disturbances. The main trends were established as follows: hydromorphic saline formation for the second floodplain level of the river valley; a gradual decrease in the groundwater level, accompanied by a gradual increase in soil salinization with depth and the absence of strong salinization at the top for interstream delta depressions; the withdrawal of the territories from the flood regime without increased soil salinization for the third floodplain level and floodplain terrace; the substitution of a typical perennial grass stand due to its freezing and damping on an annual small weed grass due to winter discharges for the depressions of the first and second levels of the floodplain.

The spatial structure of Prunus armeniaca L. populations was studied at three altitudinal levels in the mountainous Dagestan with respect to the slope steepness. The greatest density of apricot massifs is on the flat slopes of northern exposures and in areas adjacent to river valleys. On the southern slopes, due to their erosion and steepness in comparison with the northern slopes, both the density of apricot trees (r = –0.45) and the diversity of other tree species (r = –0.91) are decreased, which leads to the formation of monodominant apricot woodlands. With increasing density and joint growth with other tree species, the crown of apricot acquires a pyramidal shape; at a low density, it has a hemispherical shape.

In long-term studies (21–30 years in the floodplain ecotype and 12 years in the ecotype of sandy terraces), the duration of the main phenological phases of the development of black alder (Alnus glutinosa Gaertn.) plants was determined. The influence of the edaphic factor is manifested in the dates of the termination and duration of individual phenophases. In the sandy-terrace ecotype, growth buds are laid 8 days earlier, the leaves fall 2 weeks earlier, and the period of shoot development is longer than 7 days. Statistically significant differences between the ecotypes (tf = 2.12–7.16 > t95 = 2.01–2.03) were revealed in the duration of flowering periods and leaf development. In each ecotype, the strongest dependence of the phenological phase duration was revealed under the combined influence of the heat and moisture conditions of the corresponding period (rx (yz) = 0.55–0.99). An identical phenological spectrum in the two studied ecotypes is observed in years with a 1.5- to 2.0-fold excess of the mean multiyear value of the hydrothermal coefficient.