In the north of Eurasia, until the mid-twentieth century, the Barn Owl (Tyto alba) was sporadically distributed only in the Baltic states, in the west of Belarus and Ukraine, and in Moldova. Once, in 1942, a vagrant bird was caught in Turkmenistan also. At the end of the 20^th century, reports appeared of rare recordings of barn owls in Eastern Europe, and since the beginning of the 21^st century, pronounced expansion of these birds has been noted, observed in the south of Ukraine, Crimea, Ciscaucasia, and Transcaucasia. Different subspecies living in Central and Southern Europe and the Middle East are simultaneously expanding their nesting areas, namely: a. guttata, T. a. alba, and T. a. erlangeri. However, visual identification of subspecies and clarification of the direction of their expansion are complicated by the similarity of various forms and their significant individual variability associated with age, sex, intergradation with neighboring subspecies and other factors. The appearance of sedentary barn owls in new places is usually preceded by their post-nesting dispersion, directed in all directions and in some cases reaching 1–2 thousand km from the place of birth. Owing to the expansion of its range, barn owl populations have increased many times in a number of regions over the past decades, but accurate estimates of their numbers there are missing due to the rarity and sporadical nature of new finds, the very secretive lifestyle of these birds and insufficient knowledge of their ecology and ethology in the north of Eurasia. The article examines the taxonomy of various barn owl populations in Northern Eurasia and main diagnostic characteristics of some subspecies living in the north of Eurasia, as well as analyzes features of their historical and current distribution and expansion in Eurasia. The author also discusses possible causes and mechanisms of the barn owl dispersion and touches on information on the dynamics of their numbers in few regions.

   The different-year structure of two coenopopulations (CP 1 and CP 2) of Draco- cephalum ruyschiana L. located in different ecological and cenotic conditions of the Altai Mountains is considered. The monomodality of the ontogenetic spectra with the predominance of mature generative individuals has been established. In the ontogenetic spectra, there is an accumulation of young plants and a reduction in the proportion of old individuals. A density drop in CP 1 from 2004 till 2022 and an increase in CP 2 from 2008 till 2022 were revealed. The calculated demographic indicators and those of the development rate confirm the rejuvenation of the studied CP. According to the delta–omega classification, CP 1 develops from aging to mature, while the type of CP 2 has not changed, it remains mature. Our CP analysis shows a significant vulnerability of demographic indicators from non-simultaneous germination of seeds due to their different dormancy and the amount of precipitation. Also, the changes in the ontogenetic structure and demographic indicators in 2022 are caused by overgrowth of the communities with shrubs, namelt: Caragana arborescens Lam., Spiraea trilobata L., Cotoneaster niger (Ehrh.) Fr. in CP 1, and the presence of plant debris in CP 2.

   The paper presents an assessment of the ranges of ecological conditions in which Globularia bisnagarica L. and G. trichosantha Fisch. & С. A. Mey species exist in communities growing in European Russia. Studies were carried out in 25 communities with G. bisnagarica and 4 ones with G. trichosantha, respectively. Our assessment of the ecological regimes of phytocenoses according to D. N. Tsyganov’s scales has shown that both species live in very narrow ranges of climatic, soil factors and lighting, being stenovalent. For G. bisnagarica, the thermoclimatic and light factors were the most limiting ones. Few soil characteristics such as salinity and nitrogen richness were the limiting factors for G. trichosantha. According to the spectrum of ecomorphs, the communities of the two species were similar. The vast majority of species are classified as steppe ones. Hemicryptophytes were the predominant type of biomorphs. In relation to trophicity, more than half of the species was mesotrophic. According to the temperature regime, the meso- therms were the predominant group. The range of moisture regimes in the habitats of communities contributes to the growth of xerophytes and meso-xerophyte species to a greater extent. Due to certain specificity of the habitats of communities with Globularia on open slopes, most species were heliophytes. Our analysis of regularities of changes in the species composition of the com- munities in relation to environmental factors at global scale has shown that temperature factors make the greatest contribution.

   The direction of adaptive reactions of healthy and Hepatozoon spp.-infected green frogs from water bodies of the Nizhni Novgorod region with various hydrochemical conditions was studied. During the observation period, infection of pool frogs and an increase in the total population indicators of infection of male and female marsh frogs with Hepatozoon spp. were revealed. Hypertrophy of the morphometric parameters of infected blood erythrocytes compared with healthy cells was revealed in marsh frogs. The content of neutrophil granulocytes in the blood of infected marsh frogs was higher compared to healthy individuals, while the level of immune complexes did not differ. In infected pool frogs, an increase in the level of large immune complexes in the blood serum and the enlargement index was revealed compared to healthy ones against the background of a general decrease in the body’s resistance in conditions of severe pollution of their habitat with heavy metals and sulfates. For marsh frogs, a correlation was established between the proportion of infected erythrocytes and the content of myelocytes and young forms of neutrophils in the blood; while for pool frogs – with the content of neutrophils and the enlargement index of immune complexes. The method of multifactorial dispersion analysis revealed a significant influence of such factors as gender and the interaction of gender/infection with hemoparasites on the immune status of amphibians.

   The paper presents the results of our studies of inter-annual changes in the structure of summer zooplankton in the kultuk zone of the Volga delta depending on hydrological and meteorological conditions. The study shows the main trends in zooplankton differences in a series of low-water years. It was found that in low-water years in the kultuk zone with low runoff, short floods and weak watering of floodplain territories, zooplankton was characterized by low species richness, reduced average individual mass of crustaceans and the number of Rotifera, but a high proportion of the number of juvenile Copepoda. In the year when the water level decreased before the flood during the period of temperature increase, and then a rapid rise with the inflow of cold waters and the removal of fish larvae, zooplankton was characterized by a minimum species richness and quantitative values of Rotifera, but increased biomass of Cladocera and the Shannon index. In every low-water year, with a stable and relatively high water level before the flood, fish spawning in the kultuk zone, biomass of zooplankton reduced due to Cladocera, and the number of species in the sample. In every mid-water year, the flood had the largest runoff and prolonged, increased flooding of the floodplain, zooplankton was characterized by the maximum total and specific species richness, abundance of Rotifera, total biomass on account of Cladocera, and the individual mass of crustaceans, the Shannon index, but the minimum proportion of juvenile Copepoda.

   The results of biotesting of decabromodiphenyl oxide using a multicomponent test sys- tem are presented. It has been demonstrated that its aqueous solutions exhibit a reverse dose- dependent effect in stimulating the growth of colonies of the green algae Chlorella vulgaris and show no signs of toxic effects on Daphnia magna. During the thermal decomposition of decabro- modiphenyl oxide at a temperature of 400°C, a mixture of products is formed, one of which is bromine. The decomposition product is released into the air and possesses toxic properties, as evi- denced by stimulation of the growth of colonies of the green algae Chlorella vulgaris, as well as the death and growth abnormalities of Planorbis mollusk embryos. Therefore, water samples con- taining decabromodiphenyl oxide can be assessed for toxicity by biotesting methods, using cul- tures of green algae Chlorella vulgaris and 24-hour-old Planorbis embryos as test subjects. It is noteworthy that in the context of the prevailing perception of the safety of decabromodiphenyl ox- ide, based on its poor water solubility and low toxicity to biological organisms, there arises a need to study embryotoxic effects of the thermal decomposition products on both animals and humans. 

   The article presents the results of age structure studying in a population of the Japanese treefrog (Dryophytes japonicus) by skeletochronology. Animals were caught in the vicinity of Fokino town and Dunay settlement (Primorsky Krai, Russian Federation) in the third decade of July, 2022–2023. Cross sections of a finger’s phalanges were used as a registering structure. To es- timate age, preparations from 59 individuals (12 females and 47 males) were used. The body length of females and males was in a range of 29.40–44.80 mm (on average 38.50 ± 5.69) and 34.16–44.16 mm (on average 38.30 ± 2.36), respectively. The age of females and males varied in a range of 1–4 years (on average 2.7 ± 1.3) and 1–5 years (on average 2.2 ± 1.1), respectively. The modal age in females and males was 4 years (41.6 % of all studied individuals) and 1–2 years (63.8 %), respectively. The average age of males and females did not differ statistically significant- ly. Body length depended on age, in both females (r = 0.82, p < 0.05) and males (r = 0.54, p < 0.05). The expectancy longevity in females and males was 4.41 years (S = 0.744) and 3.76 years (S = 0.693), respectively. The growth of males stops after reaching puberty. Females continue to grow after maturation; that is why the most adult individuals are the largest ones. The growth rate coefficient (k) was higher in males (2.22) than in females (0.89). The authors note that in the south of the Primorsky Krai, D. japonicus is characterized by the minimum age of puberty and life longevity among all studied populations.

   The dependence of carbon assimilation in mixed plantings of the Penza city on the influence factors used in the ROBUL algorithm was studied. Specific carbon assimilation in the city by 99 % depends on the forest cover of the residential area, assimilation age rank and average conversion coefficient. The first factor has the greatest influence, while the conversion coefficient has the least one. The average carbon assimilation by the tree stand of the residential zone was 0.199 t/year/ha (43.6 kg/year/person). The highest indicators were in districts with forest park zones, the lowest ones were in districts with development not earlier than 2000. A positive carbon balance is observed relative to respiration of the population, but this balance is negative within the administrative borders of districts. A comparison of specific carbon assimilation at the Penza agglomeration sites calculated using the ROBUL algorithm and the obtained general regression assimilation model (RMA) showed no significant differences between them with a significant difference in the labor intensity of obtaining results in favor of the RMA model. The PMA model can be used to determine the temporal dynamics of carbon assimilation based on the planned area and composition of plantations. For the maximum possible share (42.6 %) of the green residential area of the Penza city, the potential carbon assimilation according to the RMA model for mixed species is 0.44 t/year/ha and is achieved in 40 years from tree planting, after which there is a decrease due to self-cutting.