For the first time, an assessment was given of the taxonomic and quantitative structure of the phytobenthos of seven saline rivers in the basin of the hypersaline lake Elton (Volgograd Region). Main types of algacenoses developing on substrates were revealed, namely: diatom phytobenthos, communities of diatoms with cyanoprokaryotes, cyanobacterial films and mats, and epiphyton. The phytobenthos consists of local, mosaic-distributed communities with a small similarity of their species composition. The algacenosis structure is determined by Bacillariophyta (with the predominance of species of the genus Navicula) and Cyanoprokaryota (of the genera Phormidium, Leptolyngbya, and Geitlerinema). The abundance and biomass values vary widely, reaching their highest values (109,834–417,472 mln cells/m2 and 523.6–567.6 g/m2 ) in cyanobacterial communities of mesohaline rivers with their salinity up to 16–19 g/L. Mineralization as a factor influencing the structure of communities, most rigidly acts in the estuarine sections of rivers, by controlling the composition of the dominant species. For critical salinity values (> 70 g/L), characteristic structural transformations of communities by the type of replacement of planktonic and benthic Bacillariophyta and Cyanoprokaryota by planktonic Chlorophyta (of the Dunaliella genus) and picoplankton were established.

The species composition of zooplankton in mineralized water bodies located in the Ulug-Khem basin (Republic of Tuva) was studied. These lakes have the status of natural monuments of regional significance. In total we recorded 53 species of microscopic Custaceans and Rotifers from 32 genera, 13 families, and 8 orders. Cladocera comprises 53% of the species. The dependence of the species diversity on the level of mineralization was revealed; 89% of the species were found in brackish water bodies. The zooplankton composition of the hyperhaline lakes Dus-Khol (Svatikovo) and Cheder has remained constant for many dozen years. The zooplankton includes some species known only from Republic of Tuva in Russia, namely, Microcyclops afganicus and Macrotrix tabrizensis. M. asiaticus and Alona irinae, rare for the fauna of Russia, live in the lake Haak-Hol. A decrease in the total numbers of zooplankton is observed in the lakes, namely: in the lake Dus-Khol, it has decreased by 4 times, in the lake Khadyn it has decreased by 10–19 times as compared to the middle of the last century. Despite the lack of intermediate information, we regard this as a consequence of anthropogenic impact. The emergence of an indicator of pollution (Brachionus nilsoni) in the lake Khadin confirms this version. At the same time, the stable finding of species rare for the fauna of Russia indicates the presence of favorable conditions for their development and life, which increases the value of the reservoirs themselves, which are already unique natural objects.

In previous studies it was shown that the coefficient of proportionality of the winter route count (WRC) of animals included in the formula of WRC in the form of a constant multiplier π/2, is actually a random variable – the same as the average number of intersections account route traces per unit length, and the average length of the diurnal animals. The value π/2 is the mathematical expectation value of the proportionality factor, provided that the count route equiprobably crosses the daily footprint at any place and at any angle from 0 to 2π during a winter route counting of animals. At the same time, both the nature of the distribution of the coefficient as a random variable and the values of its variance as its other statistical characteristics remained unknown. In this study, it was found that when the above-mentioned count conditions are met, the distribution of the proportionality coefficient of WRC as a random variable will be exponential or power-like. This allows calculating the values of its variance and relative statistical error in advance without collecting additional count data.

The paper presents the results of our study of ecosystem diversity and the state of split-forest areas located in the Shchuchansky district of the Kurgan region. The species composition of forest stands, the productivity of tree species, the composition of underwood, brushwood and ground cover in plantations were analyzed. Data on the distribution of forest stands of various ages, composition, types of underwood and brushwood, as well as the main dominants of the ground cover are presented. Our studies have shown that forest communities are quite distinctly different in the nature of all storeys. A preliminary assessment of the economic impact on the territory of the site made it possible to identify significant changes in all the components of forest ecosystems, namely, ground cover, the composition and productivity of forest stands. The diversity of forest ecosystems in the study area is due to the ability of many plant species to inhabit a wide range of ecological conditions, as well as the composition, age and crowncontact, which, in turn, determines the nature of the storey of shrubs and ground cover. The volume of the forest type was taken quite large, it combined plantations of all age stages of forest stands development. Features of forest vegetation, typical for split forests of the Southern Trans-Urals, were revealed, namely: mosaic vegetation cover, low crown-contact and the presence of open spaces species in the lower storeys. The materials obtained showed that, despite the significant anthropogenic transformation, the forest ecosystems of the study area retained the main features characteristic of the peculiar vegetation of the forest-steppe of southern Siberia. The research results will make it possible to assess the diversity of forest ecosystems, to give a preliminary forecast of the dynamics of the site's vegetation and can be used in the development of a scientifically grounded strategy for forest management in the region under the conditions of the joint action of many natural and anthropogenic factors.

In a laboratory pot experiment, two mutant cultivars of sunflower (Helianthus annuus cv. r2p2 and Helianthus annuus cv. r5n1) were grown on soils with anthropogenic polyelemental anomalies and on a background control soil, and a comparative analysis of their rhizospheric microflora was carried out. The numbers of soil bacteria, actinomycetes and micromycetes, as well as the numbers of rhizospheric microorganisms resistant to Zn2+, Pb2+, and Cu2+ ions were estimated in the rhizosphere of sunflower cultivars. Quantitative changes in the sunflower rhizospheric microboceno-ses, formed under the influence of both the plant genotype and technogenic soil pollution, were revealed. A pronounced stimulation of the rhizospheric microorganisms of all groups studied was found when plants were cultivated on the technogenically contaminated soil from PJSC Kosogorsk Metallurgical Plant. In this case, cultivar differences were observed, namely: the maximal number of bacteria and actinomycetes was revealed in the rhizosphere of H. annuus cv. r2p2, whilst the maximal number of micromycetes was revealed in the rhizosphere of H. annuus cv. r5n1. An increased number of microorganisms resistant to lead ions was revealed in the rhizosphere of H. annuus cv. r2p2. The observed changes in the structure of rhizospheric microbial communities of the sunflower cultivars manifested in the stimulation of the growth and activity of soil microflora can be in demand for phytoremediation of technogenically contaminated soil.

The paper discusses changes in forest-forming species in the nemoral spruce forests of the Central Forest Reserve (Tver Region, the Russian Federation). A comparison is made of the characterization of vegetation in the reserve spruce forests, carried out during the first survey of the reserve by Ya. Ya. Alekseev in 1931 (Alekseev, 1935) with the descriptions of vegetation made by the author from 2011 to 2019. It is shown that the coverage of nemoral herbs in the spruce forests of the reserve has increased over the past 90 years. In addition, three types of broadleaf trees (Tilia cordata Mill., Acer platanoides L. and Ulmus scabra Mill.) have greatly increased their abundance in the stand, most notably the linden. In recent decades, the decay of nemoral spruce forests has been taking place in the Central Forest Reserve. The birch-aspenspruce stand is not replenished with spruce renewal but is replaced by linden-maple forests. The vitality of spruce undergrowth is deteriorating. After the decay of a spruce forest, a change of the tree dominants occurs on 74% of the trial plots and the stand continues with a spruce forest on 26%. The largest part of the reserve's nemoral spruce forests arose after major disturbances 100–150 years ago (on the site of burned-out areas, hurricane windblows and cuttings). Old nemoral spruce forests were formed during the period when severe frosts prevented linden and maple from entering the stand. Currently, the coincidence of climate warming with the aging of the spruce stand and the removal of anthropogenic influence contributed to the release of maple and linden from the undergrowth into the stand and change to a spruce-deciduous forest. Under the prevailing climatic conditions, a return to the spruce forest is possible in the event of a burning out or when the climate becomes cold. The nemoral spruce forest is an ecotone type and, depending on conditions, becomes a spruce or broad-leaved forest.

The moss cover of forests in an 50×36 km area around the Middle-Ural Copper Smelter was analyzed after almost complete reduction of its emissions. It has been shown that the moss communities in the low and high pollution zones differ significantly in composition, number and frequency of species, but are characterized by a similar cover of ground mosses. The frequency of most species in the high pollution zones, compared to the low pollution zones, was decreased. A significant increase of the frequency in the pollution gradient was found for Pohlia nutans only. Species loss was expressed more strongly on the mesoscale (species richness within a community) than on the macroscale (the total number of species in a pollution zone). The elimination of species under increasing pollution was revealed for species with a low (up to 40%) initial frequency. Despite of the almost complete cessation of emissions from the smelter, the moss cover in the high pollution zones remains severely damaged and is formed by a single species (Pohlia nutans) over a significant area. However, localities with high species richness and high similarity of composition with the background communities occur even under high pollution conditions. The presence of such localities, in combination with a considerable time lag before the extinction of species from the study area as a whole, may have major significance for recolonization of degraded areas after emission reduction.

We studied the variability and phytocenotic plasticity of the morphological characters of individuals, and the numbers, density, ontogenetic structure and vitality of 11 coenopopulations of Gymnadenia conopsea (L.) R. Br. within the Kabardino-Balkar Republic in 2015–2019. The variability and plasticity of plants features provide their adaptation to various growing conditions and improve the morphological heterogeneity of coenopopulations. The dynamics of abundance, density, age structure and vitality of coenopopulations in the changing conditions of the environment provides information about life strategies of the species. Age conditions, the variability and plasticity of plants were studied on the basis of morphological parameters of the aboveground organs without digging the plants. The studies were conducted in meadow plant communities under various conditions of anthropogenic load (recreation and grazing). The species is characterized by medium-high phytocenotic plasticity of morphological characters (Ip = 38–68%) and high variability of morphological characters (CVх¯ср = 17.10– 33.63%) under changeable growth conditions. Intensification of growth processes in the individuals with the maximum increase of the coenopopulation vitality (IVC = 0.98– 1.16) was observed in the composition of undisturbed highly wet meadows; the portion of generative individuals increased in their ontogenetic spectra (48.6–56.5%). Under the anthropogenic load intensification, the vitality of coenopopulations (IVC = 0.82– 0.95) and the density of individuals decreased; the portion of virginal individuals increased in their ontogenetic spectra (rubbly meadows) or coenopopulations were clearly aging. The rate of the seed reproduction of coenopopulations, where the density of individuals accounted for 16 ind./m2 , was high on rubbly substrata with low total projective cover (60%). Our studies have identified the mixed type of life strategy for Gymnadenia conopsea with stress-tolerant and ruderal components. The ruderal-stress-tolerant life strategy allows the species to grow for a long time in conditions of high interspecific competition and anthropogenic load, spreading quickly to unoccupied territories.