The problem of changes, and especially deterioration of the quality of water in functioning reservoirs, is extremely relevant at the present time. In arid regions, the possibility of using reservoirs is limited by the increase in mineralization, but this issue has been practically unstudied and not covered in the scientific literature. The results presented in this article are original and for the first time characterize the features of quantitative changes in the spatial and seasonal transformation of water mineralization in reservoirs in arid regions over a long period of operation. The data were obtained as a result of long-term observations for the spring–autumn period from 2001 to 2023 at five reservoirs with different purposes and water regimes and located in the southern part of the steppe zone and in the northern part of the desert zone in the Republic of Kalmykia. In all reservoirs, the water mineralization was higher than the waters that feed them. In the Krasinskoye and Chograyskoye reservoirs, used for drinking water supply and filled with river waters from large rivers of other regions (Volga, Terek, and Kuma), the average value of water mineralization in the spring and autumn seasons was minimal (0.5 and 0.8 g/dm3; 1.6 and 2.0 g/dm3, respectively) in comparison with other reservoirs. The highest water mineralization was in the Tsagan-Nur and Deed-Khulsun reservoirs (5.8 and 32.0 g/dm3; 9.1 and 12.9 g/dm3, respectively), serving as reservoirs for the drainage and discharge waters of the Sarpinskaya and Chernozemelskaya irrigation and water supply systems. At the Arshan-Zelmen reservoir, created for irrigation and formed by the waters of local river runoff (2.9 g/dm3) and springs (0.4 g/dm3), the average mineralization value for the entire observation period was 5.3 and 19 g/dm3 in the spring and autumn seasons. It has been established that the mineralization of water in reservoirs with attracted runoff is not geographically determined. In reservoirs located in the desert zone (Krasinskoye and Deed-Khulsun), the mineralization value turned out to be lower than in reservoirs located in the steppe zone and having a similar purpose (Chograyskoye and Tsagan-Nur). The seasonal variability of the mineralization of water in all reservoirs is similar in that in the autumn period the values are higher than in the spring. Minimal changes were noted in drinking water reservoirs (Krasinskoye and Chograyskoye). The spatial variability of the difference in mineralization in different parts of the reservoirs is due to the fact that newly incoming waters have a lower mineralization than in the reservoir. The differences in water mineralization values between different sections of the same reservoir and between seasons are smaller than the lower mineralization value of its waters. At Krasinskii and Chograiskii, it does not exceed 0.3 g/dm3; on Tsagan-Nur, the reservoir with the highest mineralization, in the spring it is 7.9–8.7 g/dm3, and in autumn, 24.9–26.2 g/dm3. For drinking water supply and irrigation, based on the average long-term values of water mineralization, only water from the Krasinskii Reservoir can be used. Water from the Chograi reservoir, intended for drinking water supply and irrigation, based on the current mineralization value of about 2 g/dm3, can only be used for fishing and watering livestock of different categories.

The article examines the environmental consequences of the construction and operation of reservoirs – the responses of aquatic and terrestrial ecosystems and their components to changes in the water regime. Such reactions depend on the surrounding landscape and are zonally specific. They are especially pronounced in the steppe zone. The authors systematized the consequences, natural and anthropogenic factors determining their evolution, measures to minimize negative environmental consequences that can be traced from the upper reaches of the reservoir to the reservoir – receiver of the river flow, where it is built. In particular, the decrease in bioproductivity and biodiversity caused the problem of reservoir drainage. As a result of lengthy discussions, an opinion has been formed that the descent of small reservoirs, which have lost their importance, as well as orphan ones, is currently environmentally justified. At the same time, it is necessary to carry out special hydro-reclamation and phytomeliorative measures aimed at stabilizing the hydrological and ecological situation.

This paper discusses the dynamics of ecosystems and their components in connection with the development of the Aral Sea environmental crisis. The theoretical basis of this study was the idea that the vegetation dynamics under the conditions of deltaic landscape desertification represents an anthropogenically-induced natural hologenetic process involving the replacement of vegetation typical for hydromorphic floodplain and reed-bed biotopes with vegetation of semihydromorphic meadow and solonchak biotopes resulting in the formation of zonal vegetation typical for automorphic biotopes. These endo–ecogenetic successions are determined by the directed reduction in moisture supply in biotopes and accompanying salinization and evolution of soils. The changes occur in both successional and catastrophic ways. In the northern, undeveloped part of the Amu Darya River delta, the reduction of the sea water surface and a sharp drop in water reserves resulted by the 1990s in the formation of environmental conditions typical for desert landscapes: the climate parameters and their regime became close to desert ones, while the groundwater level fell to a depth of 5–10 m, thus, making groundwaters inaccessible to plant roots. Reconstruction of the reservoir system and flooding of former marine bays contribute to the formation of hydromorphic conditions on local sites. Geobotanical studies commenced in the Amu Darya River delta in 1979 and involved route surveys and surveys of topo–ecological profiles passing through the main deltaic relief elements (levees, their slopes, and interchannel depressions) were repeated in the monitoring mode in 1985, 1993, and 1999. Route surveys performed in 2017 showed that the current vegetation dynamics stage involves the formation of desert plant communities. Black saxaul (Haloxylon aphyllum (Minkw.) Iljin) first discovered in the Muynak district in 1993 is actively spreading in the most part of the undeveloped delta that has turned into a wasteland after the extinction of common reed (Phragmites australis (Cav.) Trin. ex Steud.) communities in the 1970s–1980s. The desert species Krasheninnikovia ceratoides (L.) Gueldenst. that has invaded degrading tugai and sparse arborescent saltwort (Salsola dendroides Pall.) monocoenoses on takyr solonchak soils around the same years formed extensive thickets north of the city of Kungrad. Observations on topo–ecological profiles made it possible to examine individual changes and stages in more detail. On the right bank of the Akdar’ya River that feeds the Mezhdurechenskoe Reservoir, on the Porlytau topo–ecological profile located 3 km southwest of the upland of the same name, over the course of the 40-year observation period, the river washed away a section of the near-channel floodplain and levee 500 m wide and was incised 9 m into the ground following a drop in the erosion base level (i.e., water level in the eastern part of the Greater Sea) by 26 m. Plant communities successions develop slowly. They follow the path of successional replacement of an arboreal Рoplar tugai (Populus ariana + Populus pruinosa + Elaeagnus angustifolia–Mixteherbosa with a shrubby tugai with Tamarix ramosissima Ledeb. ending in a nearby section of the interchannel depression with a catastrophic change: the death of the Halostachys belangeriana (Moq.) Botsch. community. This community was formed in 1985 as a result of soil salinization in the area previously occupied by reeds. In 2017, a slow surface desalination process that began in 1993 due to the illuviation of salts from upper (0–10 cm) horizons to lower ones continued in the soil at all survey points on the profile. For the first time, the desert shrub species Krasheninnikovia ceratoides (L.) Gueldenst. was recorded on the tugai fringe in 2017; over time, this species will probably colonize this entire site characterized by the profile. In the northeastern part of the delta, on the Kunyadarya topo–ecological profile that begins on the right bank of the dry channel of the same name and descends in the southeastern direction to the coastal plain, a degrading Populus diversifolia-Halimodendron halodendron tugai on the levee is being replaced by a tamarisk tugai, which is indicated by the species composition of the community: Populus diversifolia-Tamarix laxa + Halimodendron halodendron + T. ramosissima–Atriplex tatarica. In 2017, black saxaul was first recorded in a community formed by tall well-developed tamarisks and succulent saltworts located further along the profile on the levee slope. The profile enters a coastal solonchak plain with a Halostachys belangeriana–Climacoptera aralensis community. The salinity profiles of soils under all plant communities have a similar feature: the salt content reaches its maximum in the upper part of the profile (0–10 cm); then it sharply decreases in the 10–20-cm horizon and does not change down the profile to a depth of 50 cm. Salinity profiles of soils on two sites occupied by the tugai have the maximum similarity. The uppermost (0–5 cm) horizon is less saline or somewhat washed out from salts compared to the deeper (5–10 cm) horizon featuring the maximum salt content. In the Halostachys belangeriana community, the salt content reaches its maximum (8.28

In rural areas, research on the environment in native (untaught) soils is important to understand the rate of pedogenesis and to prevent the problems associated with hidden huger. In this article, original data on vegetation, chemical properties and elemental and mineralogical composition of Kastanozems (Protosalic, Siltic) and Hypersalic Solonetz (Siltic) of the small gully catchment (2 ha in total) located at the NE Ergeni Upland (Western Kalmykia, Russia) were presented. Vegetation was described and cut off (to characterize an aboveground biomass) at 13 key plots of 1 × 1 m. The list of species of the small gully catchment area amounts to 23 species (predominantly, perennial herbs) belonging to 13 families and 11 orders. The main dominants are Artemisia lerchiana, A. austriaca, Festuca valesiaca and Poa bulbosa. Soils were described and sampled in 11 cross-sections and two key plots (0 – 10 cm topsoil sampling). In soil water extracts (79 samples in total), electrical conductivity (EC) and pH were measured. In soil samples, particle size distribution, soil organic carbon and CaCO3 contents, total concentration of all the macro elements, some trace (Cl, Nb, Rb, Th, Y, Zr) and potentially toxic elements (As, Co, Cr, Cu, Ni, Pb, Sr, V, and Zn) were described. Moreover, the concentration of three mobile fractions of elements (Li, Be, B, Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba, Cd, Pb) measured using Inductively Coupled Plasma Atomic Emission Spectrometry (AES-ICP) was presented. Geochemical indexes of weathering (R – Silica/Alumina, CIW – Chemical Index of Weathering, CIA - Chemical Index of Alteration, WIP – Weathering Index of Parker, PWI –Product of Weathering Index, Vogt Ratio, PIA – Plagioclase Index of Alteration, STI – Silica-Titanium Index, B/A – Bases/Alumina, B/R – Bases/R2O3, Si/R - Silica/R2O3, Weathering indexes WI-1 and WI-2, Si/Ses – Silica/Sesquioxides, Si/Fe – Silica/Iron, a – Potassium/Sodium, ba-1 – (Potassium-Sodium)/Alumina, ba-2 – (Calcium-Magnesium)/Alumina, Ba – (Potassium-Sodium-Calcium)/Alumina) were calculated. In 12 bulk soil samples from Kastanozems and Solonetz, mineralogy (X-Ray diffractometry, the Rietveld full-pattern fitting method for quantitative analysis) was described. Data obtained can be used for more confident identification of pollution sources and pollutants’ migration routes, as well as for more effective land-use management, calculating the required doses of nutrients and for adaptation of land use.

The functioning of the main components of ecosystems that are recovering after reclamation at eight plots of the Arshan’-Zel’men experimental station, where reclamation works that lasted for 20 years were terminated almost 50 years ago, was monitored in the 2021 vegetation period in early May, at the end of June, and in early September. The soils belong to one type of highly transformed soils: deeply saline agrozems. The soil profile has preserved the ploughed (0–45 cm) and subsurface (50–60 cm) horizons. In 2018, the content of salts, in particular, chlorine ion, increased in the subsurface horizon at most of the plots. These changes did not affect the vegetation; the typical plant communities for the final stages of secondary succession for light-chestnut soils, rather than for solonetz soils, continued to form. The 2021 hydrothermal conditions during the observation period (May–September) can be regarded as arid. The monthly mean temperature was recorded to increase twice as much each month. Precipitation fell each month except for July. The past precipitation (176 mm) in this period exceeded the long-term mean annual precipitation over these months in 2011–2021 by a factor of 1.3, while the sum of temperatures exceeded the long-term mean annual temperature only by 2°С. Therefore, the hydrothermal conditions of the 2021 vegetation period can be rated as more favorable for the functioning of the ecosystem components than in the past years. The comparison of the data that characterizes the soil salt profile in the vegetation period showed that the content of water-soluble salts (in % per 100 g of soil) varied in the horizons from September to May in the range from –1.42 to +0.36. In different observation periods, the same soil horizons were recorded to have both unidirectional changes (only an increase) in salt content and oppositely directed changes. In May, the upper horizons of all soils, including the virgin soils, were nonsaline to a depth of 30 cm and remained in such a state until September. In the profile of virgin soils, salinization began from a depth of 30–40 cm and intensified downward, reaching the values of high salinity in the horizon of 70–100 cm (1.1–2%). At the end of the vegetation period, the salt content in these horizons decreased to the moderate level (0.5–1%). In the soils that underwent afforestation earlier, the lower horizons (80–100 cm), which were weakly saline in May, passed to the category of nonsaline soil in the fall season. In the soils that were previously reclaimed beneath the former plowed field, on the contrary, the lower horizons that were nonsaline passed to the category of weakly saline. The value of the change in salinity of soil horizons has a highly reliable correlation ratio (r = 0.89) with the chlorine ion. The vegetation cover is relatively sparse, the total projective cover (TPC) varies from 35 to 73%. The average values varied from 43 to 52% in May–June and decreased to 47% by September. The communities were dominated by bulbous bluegrass (Poa bulbosa) and Lerch’s wormwood (Artemisia lerchiana) during the entire year. Pyrethrum (Tanacetum achelliefolium) was present at all plots and at some plots, including the virgin soil, it acted as a codominant. Wild rye (Leymus ramosus) aspected in May; annuals Anisantha tectorum and Atriplex tatarica aspected in June and September, respectively. The aboveground phytomass of most phytocenoses increased from the spring to the fall, from 4–5 c/ha to 10–25 c/ha. At some plots that underwent afforestation earlier and in some virgin segments, its maximum values were reached at the end of June and decreased by the fall due to a significant decrease in phytomass of perennial grasses. In terms of species composition and domination during the entire vegetation period, Artemisia lerchiana and Poa bulbosa were referred to a pasture variant of zonal dwarf-semishrub-fаeather grass (Stipa sareptana) phytocenoses, which are typical of a semidesert steppe on chestnut nonsaline and weakly saline soils. The novelty of this study is related to the recent quantitative information on the change in the characteristics of the main components in the ecosystems of the semidesert steppes during the entire vegetation period.

Soil and geobotanical studies were carried out in a landscape district within the Northern Sarpa lowland of the Caspian Depression in a zone of light-chestnut soil. The collected data made it possible to assess the variation of soil-salinity values typical for dry-steppe plant species and communities in the Republic of Kalmykia and to produce digital models for a geobotanical indication of soil salinity. Geobotanical plots, soil test pits, and boreholes up to 2 m deep were established along a 64-m transect at 1 m intervals. The pNa salinity index was measured in aqueous suspensions of soil samples (1 : 5). As a result, it became possible to determine the salinity at depths of 0–30, 0–50, and 0–100 cm for 12 plant species and 7 plant communities registered on the transect and to distinguish three plant groups based on their tolerance to soil salinity. The first group includes species confined to nonsaline soils (salt concentrations vary within a narrow range). Plants belonging to the second group tolerate a broad range of salinity values and prefer nonsaline soils. The third group consists of salt loving species (halophytes) confined to saline and highly saline soils. Of the seven plant communities registered on the transect, two occur on nonsaline (down to a depth of 2 m) soils (Stipa lessingiana + Festuca valesiaca + Artemisia lerchiana and Stipa lessingiana + Festuca valesiaca + Tanacetum achilleifolium); two others tend to occur in soils that are not saline to a depth of 50 cm (Festuca valesiaca + Artemisia lerchiana + Tanacetum achilleifolium and Artemisia lerchiana + Tanacetum achilleifolium + Artemisia pauciflora); and three communities occur only on soils that are saline from a depth of  25–50 cm (Kochia prostrata + Artemisia pauciflora, Artemisia pauciflora, and Poa bulbosa + Anabasis aphylla). The Classification and Regression Tree (CART) method makes it possible to predict the soil salinity based on the occurrence of plant species identified as predictors. The prediction accuracy is 80% for the 0- to 30-cm layer, 81% for the 0- to 50-cm layer, and 64% for the 0- to 100-cm layer. The following plants have been identified as important (rank > 60) predictors: Kochia prostrata, Tanacetum achilleifolium, Artemisia austriaca, and Festuca valesiaca. Other species feature low prediction importance (validity) values and therefore cannot be used as predictors.

Observations of the course of natural restoration of vegetation were repeated at nine sites of the Arshan–Zelmensky Scientific Station with the same methodology after 10 years on similar dates in May. The land-reclamation works lasted 20 years and was stopped almost 50 years ago. Comparison of the data from field work in the two observation periods (2008 and 2018) showed that the changes made by land reclamation to the soil salt profiles are preserved. All of these soils belong to the same type of highly transformed soils—deeply saline agrozems. The arable (0–45 cm) and sub-arable (50–60 cm) horizons highlighted in the 2008 descriptions were preserved in the soil profile; however, in samples from 2018, the salt content increased in most plots in the subsurface horizon, in particular, the ion chlorine. These changes were not reflected in the vegetation; the formation of plant communities characteristic of the final stages of secondary succession, not for solonetzic but for light chestnut soils, continues. The total number of species recorded at geobotanical sites decreased from 70 to 62. Almost half (35 species) fell from the list of species of 2008, and, by 2018, 27 species had been added. This occurred mainly in groups of perennial and annual herbaceous plant species. The drying and loss of tree and shrub species continues (Populus album, Quercus robur, Ulmus pumila, Acer tatrica, Cotinus coggygria); and only the pear (Pyrus communis) and golden currants (Ribes aureum) showed renewal. Despite the decrease in the total number of recorded species, the species richness of communities at all geobotanical sites increased by 1.5–2.5 times. In 10 years, the characteristic species of zonal communities have spread widely: Artemisia lerchiana, Tanacetum achilleifolium, Poa bulbosa, Stipa lessingiana, Leymus ramosus, A. austriaca. This contributed to the alignment of the species composition of plant communities at all observation points and caused an increase in the similarity of the species composition between them to 56–77%, as compared with 37–57% in 2008. A similar change was also found in the aboveground phytomass: there was not only an increase (the average values in 2008 and 2018 were 734 and 849 kg/ha, respectively) but also some leveling of its values between the plots. In virgin solonetz, which shows the “background” processes, the highly saline, top 20 cm in 1950 was leached of salts by 2008 and remained nonsaline in 2018. In 2018, the aboveground phytomass here more than two times higher than that in 2008.

Artificial water bodies in Kalmykia, which is known to have limited water resources, have been constructed for drinking water supply to the population, cattle-breeding, and irrigation. Nowadays, they are heavily polluted by nutrients. The authors’ estimates support the assumption that cattle-breeding (cattle drinking and wastes from cattle-breeding sites) in the drainage basins results in the input of 1–2 t or 20 to 700 g of phosphorus per 1 m2 water surface per year in the absence of other pollutants, thus being the main cause of the fact that phosphorus concentration in all examined water bodies is tens of thousands times greater than the maximal allowable concentration for water bodies used for fishery (MACf). The share of cattle stock in the total phosphorus input is maximal (80%). Phosphorus load is 1–3 orders of magnitude greater than the allowable and critical values for aquatic ecosystem functioning, creating the conditions for eutrophication and making the water of these reservoirs undrinkable even for cattle.

Artificial water reservoirs in Kalmykiya, which has limited water resources, were developed for a potable water supply for the local population, cattle breeding, and irrigation. Currently, they are strongly contaminated by biogenic substances. Calculations are provided in this study that confirm the hypothesis that cattle breeding (watering points of cattle and run-off from cattle breeding areas) developed in the water catchment area suppl 12 tons or from 20 to 700 g of phosphorus per 1 m2 of water surface per year in the absence of other contaminants; this is the main reason that phosphorus content in all water reservoirs exceeds the maximum allowable concentration established for fishery water reservoirs (MACf) by tens of thousands of times. The highest proportion (80%) of the overall volume of incoming phosphorus originates from the bovine cattle. Phosphorus loads exceed the allowed and critical values for functioning of the water ecosystem by from 1 to 3 orders of magnitude, forming conditions for eutrophication and rendering water of these reservoirs unsuitable for potable water supply, including for cattle watering points.

The proposed concept concerns determination of the parts of the coast differently affected by the water reservoir. Some parts (blocks) of any shore are directly affected by the flooding: aquatic block part of the water object never exposed from the water, located on the depths more than 2.5 m; amphibian block part of the reservoir bottom exposed periodically; dynamic block periodically flooded coast territory. By contrast, the next ecological belt - distant block - is affected by flooding indirectly. It includes territories of coast with ground waters no deeper than 3 m. The marginal block is located on the coast with ground water level below 3 m. There the impact of the reservoir is biological and has passed through the chain of biological relations. This methodology was developed to study the influence of water objects on the lands adjacent to the reservoirs. It allows to connect elevation of the land surface with fluctuations of the water object level and with groundwater level and also to determine the boundaries of allocated blocks afield. Thus, the proposed method allows to optimize the number of field observations.

The modern state of vegetation and soils on the Peri-Yergenian plain (northwest Peri-Caspian lowland, the Republic of Kalmykia) have been studied. This area was subjected to deep ameliorative plowing, irrigation, and agroforestry in the 1950–1960s (irrigation ceased in 1971; periodical plowing ceased in 1984). A homogenous soil cover has formed under the conserved tree plantations and on the former irrigated arable lands; however, the morphological and physical and chemical properties of the initial solonetzic soil complex (solonetz and solonetzic light-chestnut soils) have practically been transformed there. The plough layer (0–45 cm) and subsurface layer (50–60 cm) can still be determined there. They are free of salts, and the exchangeable sodium content decreased there. All of these soils belong to one type of deeply saline solonetzic agrozems. The apple orchard died without irrigation 6–7 years after planting. Other trees were only partially preserved in irrigated areas; seed regeneration has been observed only for Elaeagnus angustifolia , Ulmus pumila , and Ribes aureum , and sprouting regeneration has been seen for Pyrus communis . At sites of degraded trees, species of shrubs that were cultivated in the forest belts, as well as local flora, appeared in this area. These communities have greater species richness and larger aboveground phytomass in comparison with the surrounding virgin vegetation. The present species composition and the structure of herbaceous plant communities allow us to conclude that there is a restoration plant succession and that communities typical for virgin chestnut soils with a predominance of Artemisia lerchiana , Tanacetum achilleifolium , and representatives of the family Gramineae ( Festuca valesiaca and Stipa lessingiana ) have formed. At reclaimed sites without irrigation, the restoration of vegetation leads to the formation of plant communities similar to those observed on virgin solonetz soils.

Thorough soil–geobotanical studies have been performed on a key plot located in the deserted steppe subzone of the light-chestnut–soil zone within the physicogeographical region of the Northern Sarpinskaya Lowland, Kalmykia, along a 64-m-long profile with coupled analysis of microrelief, vegetation, soils, and remote data (detailed Quickbird image). Geobotanical plots, soil trenches, and holes 1–2 m deep have been established along the profile at 1-m intervals. Analysis of the data has showed a close correlation of soils with plants communities (r = 0.72) and loose correlations of these parameters with microrelief (r = 0.42 and r = 0.36, respectively). Some species―Falcaria vulgaris, Limonium caspium, Agropyron desertorum, Stipa lessingiana, Artemisia lerchiana, Festuca valesiaca, and Tanacetum achilleifolium―are never seen on crust solonetzes; the first four species are also never found on shallow solonetzes, and the first two species are never encountered on solonetzic soils. Other species―Kochia prostrata, Artemisia pauciflora, Anabasis aphylla, and Bassia sedoides―are mainly confined to shallow and crust solonetzes and are rarely found on other soil types. The mowing data are well correlated with the normalized difference vegetation index (NDVI) (r = 0.77). The status of vegetation reflected by the NDVI value on the image is clearly determined by edaphic conditions, primarily the soil variety.

The structure of taxa, biomorphology, ecology and ecological–cenotics groups present in the coastal flora of Krasnodar, Tsymlyansk, Veselovsky, and Proletarsky reservoirs, located in the south of the European part of Russia are characterized. Field data were obtained during the field work of the authors in 2004–2013, and a botanical database was formed on this basis. In light of the location of the investigated artificial lakes in different subzones of the steppe zone, the characteristics of the coastal flora can be considered as an ecological–geographical (zonal–regional).

This paper gives the substantiation and characteristics of the methodology for studying and assessing the impact of large reservoirs on natural shore complexes. An algorithm is proposed for the work; it includes a stage for the identification of shore areas exposed to direct (flooding) and indirect (waterlogging) reservoir impacts and a stage for the assessment of the transformation of natural complexes in each of these areas. The impact assessment is based on a system of the biological and environmental parameters and criteria that are indicators of the hydrogenic transformation of the environment and biota in shore areas (groundwater, soils, and vegetation). Their combination makes it possible to estimate the extent and depth of changes in natural wetland complexes, both by comparison with initial landscape components and by the developed scales for each of the parameters. The use of this method is considered based on the example of lowland reservoirs in the steppe area of European Russia.

The unique files of oak woods extended at tops of manes in northern part by Volgo-Akhtuba flood-plain, represent the relic wood communities which have reached of final stages succession developments, characteristic for the flood-plain southern rivers. Absence of seed renewal, copies of 1st generation and strong defeat of leaves testifies to their adverse condition. Direct anthropogenous influence, the raised mineralization of ground waters – is the major factors menacing to their existence. It is recommended to include the given oak large forests in system SGNT of water-marsh grounds of theLower Volga Valley.

The paper describes changes in environmental factors (reservoir water level, depths of groundwaters and their mineralization) of the “water-terrestrial” ecotone system and the ecosystem components (soils and vegetation) at various types of Tsimlyansk reservoir coastal areas. The study is based on field monitoring surveys conducted from 2004–2013. It was revealed that maximal levels of the reservoir water exhibit trended toward a decrease, while the minimal and medium trended toward an increase. The amplitude of the water level fluctuations over the last few years seldom exceeded 2 m and showed a tendency to decrease. The aforementioned dynamics facilitate continuation of the abrasion processes and a decrease in the areas of shortterm flooded territories outside the coastline. This endangers the belt forest formed at the shores at the height of 35.5 m above the sea level. No statistically significant dependence of the groundwater level on atmospheric precipitation was revealed, but the resevoir level of the did not expand past the coastline over the last few years, with below-average annual precipitation values. Multiannual and seasonal fluctuations in the depths of groundwaters relate to the reservoir water level. Areas situated at a distance of not more than 200 m from the coastline are subject to flooding. In total, 157 species of vascular plants (11 species are trees and shrubs) were recorded at the reservoir shore area. Maximal species richness (110 species) was found at shore areas subject to short-term flooding (the dynamic block). Maximal values of primary production were registered in the amphibial block, within the belt of reed marshes.

Recent data (2006–2008) on characteristics of the vegetation and soils of the solonetzic complex in areas with tree failures within the Volgograd-Elista-Cherkessk forest shelterbelt have been compared with those obtained prior to afforestation (1950). The results show that the vegetation and soils have changed profoundly. Solonetzic agrozems in tree failure sites have been occupied by herbaceous plant communities similar in composition to natural communities. Anthropogenically altered soils formed under forest plantations have no natural analogs. The initial strongly saline shallow (crusty) solonetz soils with a chloride-sulfate or sulfate-chloride composition of salts have transformed into slightly saline solonetzic and solonchakous agrozems with sodium sulfate salinity or with increased alkalinity in the middle of the soil profile and a dealkalized arable horizon.

The consideration of the zone of interaction of water basins and adjoining territories as water-terrestrial ecotone systems and the use of indicators of the hydrogenic dynamics of natural complexes has allowed us to identify the ecological-geographical peculiarities of their transformation in different zonal-landscape conditions and connect the direct and indirect influences of the water factors. The features of the structurally functional organization of the ecotone systems of coasts are established, the degree and character of transformation of components of the ecosystems in different blocks of ecotone are appreciated, and the development of dangerous processes is determined.