Russian Journal of Ecosystem Ecology

The North Caucasus steppe vegetation is one of the "blank spots" in vegetation classification survey of Russia. Its syntaxonomy is in the early stages of elaboration and represents a new area of research in modern vegetation science. Geobotanical data on the steppes of the North Caucasus are important for analyzing the differences between the steppe vegetation of Europe and Asia and they are necessary for development any comprehensive syntaxonomic and phytogeographical generalizations on the grasslands of Eurasia. This article continues publication of the results of the North Caucasus steppe vegetation research. Geobotanical studies were conducted in June 2022 and May-June 2023 on the Borgustan, Dzhinal and Skalisty Ranges. Geobotanical relevès were based on standard methods. The relevès were placed to the database elaborated using the TURBOVEG program and processed
by the Juice program. Syntaxonomical analysis was carried out using the J. Braun-Blanquet approach; the names of the new syntaxa were given in accordance with the "International Code of Phytosociological Nomenclature." The system of higher syntaxa was given according to the synthesis "Vegetation of Europe..." with additions.
Geobotanical studies of the North Caucasus steppe vegetation carried out on the Borgustan, Dzhinal, and Skalisty ranges, and the subsequent syntaxonomic analysis based on the J. Braun-Blanquet approach allowed to reveal a new association Helianthemo nummularii-Caricetum humilis ass. nov. and two new subassociations Helianthemo nummularii-Caricetum humilis typicum subass. nov. and Helianthemo nummularii-Caricetum humilis centauretosum holophyllae subass. nov. Conclusion. The new syntaxa were attributed to the alliance Helianthemo buschii-Elytrigion stipifoliae Lysenko, Shchukina, Neshataeva, Shilnikov et Dutova 2021, the Order Galio biebersteinii-Bilacunarietalia microcarpae Lysenko, Shchukina, Neshataeva, Shilnikov et Dutova 2021, the Class Festuco-Brometea Br.-Bl. et Tx. ex Soó 1947. 

The shrub expansion of the tundra is one of the key processes transforming Arctic ecosystems under climate warming. Alder thickets play a significant role in this process. However, their phytocenotic structure and associated soil changes in the southern tundra of Western Siberia remain poorly understood. The aim of this study was to identify the spatial patterns of vegetation distribution within an isolated alder thicket in the typical tundra and to quantitatively assess its phytocenotic diversity in comparison with the surrounding tundra communities. The study was performed in August 2021 in the Pur-Taz interfluve. We made 37 geobotanical relevés and 32 soil pits were dug, along 8 transects from the tundra to the center of the alder thicket. The structure of the vegetation cover was analyzed using multivariate methods, including clustering and Principal Coordinates Analysis. The relationship between vegetation and soil-topographic factors was assessed using Redundancy Analysis (RDA). Cluster analysis revealed 7 distinct phytocenotic clusters. These clusters form a gradient: from dwarf shrub-moss-lichen tundra to the formed core of the alder thicket, through an ecotonal peripheral zone. Phytocenotic diversity was highest within the ecotone. In the core area, dominate a Calamagrostis lapponica (or Carex globularis), while the moss-lichen cover is almost absent. RDA revealed a statistically significant relationship between vegetation and key environmental factors, including projective cover of lichens and tall shrubs, as well as soil thixotropy. The shrubification process is accompanied by soil transformation: a reduction in the thickness of the peat horizon, but an increase in the humus horizon and the depth of root penetration into the soil. For the first time for alder thickets in the southern tundra of Western Siberia, the spatial phytocenotic structure has been quantitatively described and its close relationship with a complex of soil-topographic factors has been proven. The RDA results showed that the vegetation change from the tundra to the alder thicket core is associated with a shift in ecological parameters. The first gradient (RDA1) separates tundra plots with lichens and thixotropic soils from the central alder zone with a more pronounced humus horizon. The second gradient (RDA2) separates clusters within the thicket based on microrelief: in depressions, sedges and Betula nana dominate, while on convex areas with a sparser shrub layer, Calamagrostis lapponica dominates, accompanied by deep penetration of fine roots.

Fish reproduction is an important part of their life cycle, ensuring the reproduction of populations and the preservation of species diversity. The quality and volume of population replenishment directly depend on the characteristics of the spawning population and the reproductive potential of individuals. Therefore, the aim of the article was to study the features of the variability of the life cycle of an invasive species of sunfish (Lepomis gibbosus L., 1758) in the reservoirs of the Lugansk People's Republic. The research was conducted in the spring and summer periods from May to September 2016-2023 in the basins of the Seversky Donets and Mius rivers. 410 sexually mature individuals were studied: There are 213 males and 198 females. In fish, we studied body length according to Smith, body weight, gonadal mass, and age according to generally accepted methods. The gonadosomatic index, individual absolute fertility, individual relative fertility, and the diameter of the eggs were determined. Histological sections of the calf joints were used to determine the type of spawning. All data was statistically processed using the MS Excel and Statistica 10 software packages. The appearance of gonads in fish was noted at the age of 1+ and puberty occurred by 2+. The ratio of males to females varies from 2:1 at the age of 1+ to 1:1 at the age of 2+ – 4+ and 1.5:1 at the age of 5+. The life expectancy of sunfish in recipient reservoirs is decreasing: in the native environment – 10 years, in other reservoirs – 8, in reservoirs of the Lugansk People's Republic – is reduced to 5+. The fertility of females increases with age and body weight from 830 eggs in 2+ to 1550 eggs in 5+. Fish spawning lasts from May to August at water temperature +17 – +28 °C. The gonadosomatic index of fish is maximal before spawning (23.3 %). 75–80 % of the females spawn annually. Thus, the sunfish species (Lepomis gibbosus L., 1758), having undergone some transformation of biological and morphological features in comparison with native reservoirs, successfully adapted to the ecological conditions of the reservoirs of the Lugansk People's Republic. This resulted in earlier puberty (1+ – 2+) and shorter life spans up to the age of 5+, reducing the number of spawning from 3 in native reservoirs to 2 in recipient reservoirs. The studied species retained a number of biological features peculiar to individuals in native reservoirs: weakly expressed sexual dimorphism in length and body weight, portioned and asynchronous spawning with 3 periods of spawning.