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According to the scheme of age periodization of plant ontogenesis proposed by T. A. Rabotnov and A. A. Uranov, about a dozen of main age (ontogenetic) states are distinguished. Each population sample represents an ordered series of frequencies of occurrence of plants at these states - the so-called ontogenetic spectrum (OS). Various OS statistics are available according to the form of the OS, reflecting a greater or lesser representation of young, mature or old plants in the population and allowing to represent the temporal dynamics of the population. The Excel Ontogenetic Spectrum (ExOS) package presented allows their automatic computation and analysis. The input data are the numbers or frequencies of ontogenetic states in the sample. Output data: classifications of OS and cenopopulation types according to various criteria, population-ontogenetic indices; for multiple population samples - similarity (distances) between them and their ordination on "delta-omega" axes; the corresponding diagrams are captured authomatically.

Presented is a description of the distribution of terrestrial vertebrates in the northeastern part of the Kanin Peninsula (67°50′47′′ N, 46°20′40′′ E) based on the results of their counts conducted in July 2021. In total, 1 amphibian species, 1 species of reptiles, 57 species of birds and 6 species of mammals were recorded. The vertebrate fauna of this region, located in the dwarf birch tundra zone, is characterized by the presence of boreal species such as the viviparous lizard Zootoca vivipara Lichtenstein, tufted duck Aythya fuligula (L.), common goldeneye Bucephala clangula (L.), common crane Grus grus (L.), common sandpiper Actitis hypoleucos (L.), brown bear Ursus arctos L. and European elk Alces alces L. For the viviparous lizard, this is the northernmost known locality so far. Favorable factors for the distribution of boreal species in this area, in our opinion, are its location on the southern slope of the plateau-like ridge Kanin Kamen, the ruggedness of the relief, primarily deep river valleys with wind-protected and well-heated sides. A tenfold decrease in the density of placement of brood burrows of the Arctic fox Alopex lagopus L. was established in comparison with the 40-50s of the last century, due to the activation of cryogenic processes in permafrost, as a result of which the burrows of this predator, arranged in loose soils, are destroyed.

Despite more and more data on the Arctic biotic communities even the principal course of their transformation remains unclear. In this concern the profound interest is related to differences in population dynamics of geese, lemmings and ruminants covering more than 98 percent of the Arctic terrestrial ecosystem recycling and competing on the specialization ground for the same food resources. Comparing 15 species of the taxa we showed that grades of their morphophysiological adaptation to phytophagy are matched to empirical estimates of their food selectivity, thereby describing their trophic specialization distribution. Thus in the Arctic herbivore communities the selectivity distribution is so stable as specialization. The trophic specialists include muskox and snow goose in the first place, while the generalists are lemmings and smallest black geese. The specialist populations have mainly higher size and/or growth rate than the generalist populations have. It may be concluded that interspecific competition influence contemporary transformation of the Arctic herbivore communities much stronger than such environmental factor as global warming and human activity do.

The 45-year-long observations of variations in the musk deer abundance in the Ussurisky Nature Reserve are summarized. An analysis of winter route censuses has made it possible to assume these variations to be related with the emergence of a “new predator”, sable. The decrease in the musk deer abundance in the reserve occurred simultaneously with an increase in the sable abundance and a decrease in abundance of alternative food supplies for medium- and small-sized predators. From the early 2000s until the present time, the musk deer abundance in the reserve has remained at a level of only “presence” of the species in the fauna.

In the current article, the authors study small mammal species composition and population structure of the northern taiga landscape of the Nadym Hills (Yamal Nenets Autonomous Okrug, Russia). Special attention is given to catenae regularities of the intralandscape differentiation. Five micromammal species (Cl. rutilus, S. caecutiens, S. araneus, A. oeconomus, E. sibiricus), typical for the Western Siberia northern taiga subzone, were caught in different north-western parts of the catena (at the flat interfluve (placor), saddle, slope, flood plain). Red-backed mice Cl. rutilus outnumbered other species in all catena locations and in the landscape on the whole. Other species codominate in certain locations with an exception of S. araneus being common only at the placor. On the whole, over the area under study and in the higher locations of the catena, Cl. rutilus and S. caecutiens make up the core of small mammal communities. Along the hill slope - from the placor to the flood plain - the overall micromammal abundance and dominating species abundance decline gradually. A settled breeding small mammal population is present in all catena locations. The micromammal community composition, structure, and characteristics change along the slope in accordance with the changes in the territory afforestation, moistening, plant species richness, vegetation structure, microtopography. Due to harsh climate, the small mammal communities of all catena locations and whole area under scrutiny show low indices of diversity, evenness, and sustainability, high dominance index, but on the whole their structure is undisturbed and characteristic of natural subarctic communities, being indicative of the communities’ stability.

An analysis of depth-profile and spatial variations of the stable carbon isotopic composition of soil organic matter is presented to identify the main factors that determine the dynamics of organic carbon in the mountain-depression environments of the Baikal region. Soil organic matter is characterized by δ¹³С values from -29,6 to -24,9 ‰. Changes in δ¹³C values in the altitudinal profile correlate well with changes in landscapes and reflect the influence of climatic factors on13C discrimination during photosynthesis of C3 plants. The heaviest stable carbon isotopic composition characterizes the soils of subalpine and steppe landscapes. In taiga soils, depletion of the isotopic composition by¹³C is observed. To compare the soil carbon turnover intensity δ¹³C values were regressed linearly against log-transformed carbon contents yielding absolute values of these slopes (β). The distribution of β values in the altitudinal profile suggests a reduced intensity of carbon turnover in the soils of the steppes and the subalpine belt due to the limitation of these soils in terms of moisture and temperature, respectively. Under the taiga conditions characterized by more favorable ratio of temperatures and humidity the dynamics of soil organic matter is controlled mainly by the litter quality and the nitrogen availability.

The work presents the results of studies of the emergence of amphibiotic insects from the old beaver pond on the Yuzhny stream of the “Privolzhskaya lesostep’” reserve in the Upper Khoper basin. For insects from 34 families and 8 orders, the indicators of abundance, biomass, frequency of occurrence are given, the timing of their emergence in different parts of the pond is indicated. The dominant and common species were identified - chironomids Paramerina cingulata (Walk.), Cricotopus silvestris (F.), biting midges (Bezzia bicolor (Mg.), chaoborids Chaoborus flavicans (Mg.) and mayflies Cloeon inscriptum (Bgtss.). The intensity of the emergence of insects was 12.10 ind./m² per day, the average daily transfer of biomass was 49.23 mg/m² per day. The analysis of the fatty acid composition and content of the main biogenic elements in adults of amphibiotic insects was carried out. The results of calculations of the removal of energy and matter, including biogenic elements (carbon, phosphorus, nitrogen) and polyunsaturated fatty acids during the emergence of insects from various orders (Ephemeroptera, Odonata, Trichoptera and Diptera) into adjacent terrestrial ecosystems. The transfer of raw biomass from water to land was 7.385 g/m² per year, in dry weight - 2.216 g/m² per year; transfer of the main nutrients - 1.21 g/m² per year - carbon, 0.25 g/m² per year - nitrogen, and 0.03 g/m² per year - phosphorus; PUFA transfer - 24.16 kg/km² per year.

Bacteria perform important and diverse functions in the ecosystems of large rivers. The abundance, biomass and spatial distribution of heterotrophic bacterioplankton and its size-morphological groups were studied in the middle and lower reaches of the Ob River in the areas impacted by cities. The river water was characterized by a high content of suspended particles (on average (2.22 ± 0.21) × 10⁶ ml^-1), to which a significant part of bacteria was attached: on average, 41.5 % of their total number and 35.7 % of their biomass. The concentration of suspended particles and water conductivity were found to be among the main factors affecting the abundance and structure of bacterioplankton. A significant increase in bacterial abundance, mainly due to small free-living bacteria, was recorded below the mouth of the largest tributary, the Irtysh River, and the city of Khanty-Mansiysk. On this section of the Ob River, the average values of bacterioplankton abundance and biomass were (6.87 ± 4.99) × 10⁶ cells/mL and 142 ± 13 mg C/m³, respectively, which were 1.6-1.7 times higher than in the other sections. The spatial distribution of heterotrophic bacterioplankton in the Ob River is mainly determined by the dynamics of water masses and the influence of tributaries and cities.

The results of an eight-year study of the Platanthera bifolia (L.) Rich. (Orchidaceae) population on the northern border of its range (the Komi Republic, north-east of the European part of Russia) are presented. A negative correlation was found between the size of the leaves of this species and precipitation at the beginning of the current growing season. The number of flowers and their sizes are influenced by the weather conditions of August of the previous growing season. There were no significant differences in plant height and inflorescence length over the years. The number of the studied population is high for this species (400 plants); it is negatively affected by the lack of moisture in the previous year. Observations of mapped individuals revealed the duration of the presence of plants in different phases of ontogenesis. The ontogenetic spectra of the studied population correspond to the basic spectrum of the species, in some years the dominance of juvenile individuals is observed, which is associated with the renewal waves characteristic of the species. The pollination efficiency is not affected by the number of flowers in the inflorescence or their size; it is related to the level of moisture availability of the territory. Seeds of P. bifolia (0.60 × 0.13 mm) in the studied area are smaller than in the southern parts of the range of this species. Significant differences in the size of seeds in different years of the study were revealed, the main influence on them is the weather conditions of July. A tendency to increase the volume of air space in the seed in wetter years has been found, which contributes to their better distribution under adverse weather conditions. Real seed productivity of P. bifolia varies by year from 25.4 thousand to 40.8 thousand seeds; this indicator is associated with the level of moisture availability of the current growing season. The presence of juvenile individuals (18.3-51.8 %) in all the years of study indicates successful seed renewal in this population. The number of juvenile individuals correlates with the moisture level of the previous growing season.

The facts of an increase in the proportion of phytopathogenic forms of micromycetes in soils contaminated with heavy metals (HM) make it relevant to study the mechanisms of their resistance, which is important to choose effective phytopathogen control methods. The issues of interaction between metal-resistant phytopathogens and non-pathogenic species against the background of pollution remain no less relevant and need to be studied. In laboratory experiments with pure cultures of four fungal species (phytopathogenic strains Alternaria alternata and Fusarium oxysporum and non-pathogenic strains Trichoderma harzianum and Clonostachys rosea), the resistance to Cu, Zn, Pb cations, separately added to nutrient medium with different content of available carbon (sucrose), was studied. Colony growth, sporulation activity, and biomass accumulation were measured. The effective concentrations, resulting in 50 % inhibition of growth parameters (EC₅₀), were calculated. The studied fungi showed different resistance to HM. T . harzianum and C. rosea were more resistant to Zn and Pb at any available carbon content. The pairs A. alternata-C. rosea and T. harzianum-C. rosea were the most resistant to Cu on media with lower and higher carbon contents, respectively. At the same time, Zn and Pb turned out to be less toxic than Cu for all fungi. The antagonistic activity, assessed by the dual culture method on media supplemented with HM cations, depended both on the growth characteristics and on the revealed resistance to HM. The activity of fast growing T. harzianum as a territorial antagonist was stimulated by the addition of Zn and Pb. The slow-growing C. rosea showed competitiveness due to its high resistance to HM. It is concluded that it is necessary to take into account species resistance to HM in order to predict the development of relationships between pathogenic and non-pathogenic species in fungal communities against the background of soil pollution.