Among the four structural levels of branching, floodplain-channel branching and bifurcated channels are the most morphologically complex and at the same time quite common. The independent development of branches in such channels leads to a great diversity of their forms and parameters, as well as the specific hydrological and channel regimes of these sections of the channel. Unlike of the lower structural levels, the detailed hydrological and morphological analysis and assessment of the reorganization of branches of bifurcated channels are poorly covered in the scientific literature. The parameters of branched channels, the ratio of branch water content and the rate of bank erosion, the set and parameters of morphodynamic types of branches, and the characteristics of interbranching are discussed. The characteristics of an incised forked channel and its difference from a similar one formed under free development of channel deformations are shown on particular examples. The conditions of formation are shown and the characteristics of floodplain-channel branches formed in a wide floodplain and, less often, incised channel are presented, as well as the influence of hydrological and geological-geomorphologic (protrusions and capes of the native banks) factors on the deformation of branches and the long-term redistribution of flow.
Thus, the paper provides an analysis of morphodynamics and hydromorphology of the arms of floodplainchannel branches and forked channels taking into account their features on rivers of different size (orders), water content, sediment flow and other natural conditions and factors of their formation.

Based on the results of in-situ measurements of methane concentrations in water and specific fluxes from the water surface, methane emission from the Kolyma reservoir in the warm period of the year was estimated for the first time. The catchment area of the reservoir is completely located in the permafrost zone. The specific flux was measured by the floating chamber method, and the methane content in samples was determined by the headspace method [Goldenfum et al., 2010]. The LAKE 3.2 model [Lomov, Stepanenko et al., 2024] was chosen as a main tool for numerical simulation of specific methane fluxes from the Kolyma reservoir. The paper integrates the materials of seasonal observations in September 2021, April and August 2022, and August 2023. The spatial and seasonal variability of both methane content and methane emission was revealed. The low amount of organic matter in sediments (no more than 10% for the predominant part of the reservoir), low methane content in the water mass (on average no more than 4 μlCH4/L in summer and 12 μlCH4/L in winter), and low organic carbon content in the water (4–5 mgC/L) favor the formation of a low specific flux (SF) of methane from the surface (1–3 mgCH4/m2/day). Based on observations, the methane emission from the entire reservoir surface was 0,4–0,5 tonnes of CH4/day in the summer period 2022–2023 and 1,56 tonnes of CH4/day in 2021.
Using the model it was possible to obtain an adequate simulation of daily methane emission from the Kolyma reservoir, which corresponds to the data obtained in the course of field measurements of methane SF from the reservoir. The model calculations provide a representative estimate of methane emission from the studied reservoir, which takes into account the variability of methane flow during the year. The latter doesn’t seem possible because of the limited number of field surveys for the Kolyma reservoir, which is difficult to access for research. The average annual methane emission from the Kolyma reservoir for the period from 2021 to 2023 is 958 tonnes per year. The interannual variability of methane emission is quite significant, and could be explained by the dynamics of the temperature regime, which determines the rate of methane generation in bottom sediments, as well as by the difference in its spring release, which occurs as a bubble component of the flow during the ice cover breakup in spring.

The purpose of the work is to identify and assess the degree of impact of natural and economic factors on water quality in the Angrapa River basin of the Kaliningrad Region. Four hydrochemical and hydrological monitoring sites have been identified for each of Angrapa, Pissa, Krasnaya and Russkaya watercourses, from their upper reaches to the estuary parts. The Angrapa River was an exception because the first monitoring site is located at a distance from the upper reaches near the state border. River studies were carried out seasonally over two hydrological years, starting from autumn 2022 and ending in summer 2024. The results of chemical analyses of water samples were used to calculate the WPI and, which were extrapolated to certain areas. The results obtained were then compared with the differentiated natural and economic conditions of the basin. The natural and economic conditions prevailing in the Angrapa River basin are territorially expressed as follows: agriculture 40%, forest cover 36%, urbanization 3%, lake area 5% and other 16%. According to the SCWPI for 2022–2024 water quality varies from 3b – very polluted to 4v – very dirty. The pollution increases from the source to the mouth, which is accompanied by a decrease in forest and growth of agricultural lands, as well as the accumulation of chemicals downstream watercourses. The main pollutants that do not meet the MAC standards are oil products, iron, dissolved oxygen, COD, BOD5, phosphates, ammonium and nitrites. Based on this, we have identified the following potential sources of pollution: agriculture, urbanized areas, groundwater with a high iron content, natural cycles of aquatic and coastal vegetation. Correlations were found between the SCWPI and the percentage of agricultural lands (corr = 0,70) and forests (corr = –0,81), but the nature of these relationships needs to be studied more in detail. The impact of water volume on water quality varies depending on the rivers and hydrological seasons, which requires additional research and data from hydrographic posts.

Gold deposits in Transbaikalia are characterized by an abnormally high content of a number of elements, especially As, which leads to soil and plant pollution and affects the health of people living there. Studies conducted in the area of the Lyubavinsky gold deposit were aimed to determine the concentrations of a number of toxic elements (As, Ba, Be, Bi, Cd, Hg, Pb, Sb and Tl) in soil and plants. The test areas were located at a tailings dump and within natural plant communities. To determine the concentrations of trace elements in soil and plant samples, the procedures from “Methodology for measuring the metal content in solid objects by inductively coupled plasma spectrometry” (1998) were applied. The gross content of As, Bi, Hg, and Sb in soils of the tailings dump and the surrounding area was found to be abnormally high relative to their clarks of the Earth’s crust (Rudnick and Gao, 2014). The hygienic standard of as was exceeded in the soil at all test areas, that of Hg and Sb – in the soil of the tailings dump. Herbaceous plants in the area of the tailing dump (Thermopsis lanceolata, Artemisia gmelinii) were characterized by a significant excess of the established standards for medicinal raw materials in terms of as content in the underground and aboveground parts of plants. Outside the tailing dump as concentration was slightly higher the standards, with the exception of Phlojodicarpus sibiricus, in which the as concentration in the underground part significantly exceeded the maximum permissible concentration. The concentration of the studied elements in the aboveground and underground parts of the plants depends on the biological characteristics of plants and the environmental parameters. P. sibiricus and A.gmelinii were characterized by a relatively high concentration of elements in the underground part of the plant, while T. lanceolata showed a higher concentration in the aboveground part, especially the inflorescences. The available forms of Cd, Sb, Ba, Hg, Tl, and Bi were most actively extracted by plants. It is not recommended to collect and use medicinal and forage plants near the Lyubavinsky deposit without monitoring the content of toxic elements in them.

Study of the environmental impact of water reservoirs became a key research direction in the 1960s‒70s in connection with the design of the Nizhneobskaya hydroelectric power station, as well as the transfer of the Pechora and Vychegda rivers into the designed Verkhne-Kamskoye reservoir to regulate the Caspian Sea level. The knowledge of plain reservoirs clearly exceeded that of mountain and foothill reservoirs, such as, for example, the Zeya reservoir. Based on the dendrochronologic analysis of about 1000 cores, mainly of Gmelin larch, collected in the altitudinal belts of the Tukuringra and Soktakhan ranges, the chronologies were constructed. Climatic data from the Zeya city meteorological station (at 230 m above sea level) were used, as well as the ERA5 climatic data – the global reanalysis of the fifth generation of the European Centre for Medium-Range Weather Forecasts (ECMWF). Against the background warming in the region of about 3°C over the past 65 years, the territory near the reservoir is excessively heating up. Average monthly air temperatures before and after the construction of the reservoir are given. In July-October they became 0,5‒0,9°C higher. The increase in air temperature in the coastal zone is due to the very low water exchange coefficient of the reservoir (0,3). Landscape profiles within the presumed influence zone of the reservoir have recorded an increase in the phytoproduction process at the altitude of 310 m above sea level for northwestern slopes (Tukuringra range) and southeastern slopes (Soktakhan range), a slight increase at the altitude of 420 m a. s. l. and no increase at the altitude of 570 m a. s. l. Outside the influence zone, in the valley of the Alenga River, the phytoproductivity after the creation of the reservoir is synchronous on different slopes, but without a pronounced influence of the reservoir. Due to the slow water exchange in the Zeya Reservoir in the period from July to mid-September the upper water layer warmed up to +21°C, thus affecting the climate of the coastal zone up to 420 m a. s. l. Against the global climate change, the air temperature in the summer and autumn periods is higher in the influence zone of the artificial water reservoir. Mountain reservoirs have a local, but more intense influence compared with plain ones.

Expeditionary research during 52 and 56 cruises of the R/V “Akademik Nikolaj Strakhov” in 2021‒2023, was aimed at surveying a part of the Kara Sea water area northwest of the Bely Island. Based on seismoacoustic data, signs of degassing were identified in the relief, sedimentary cover and water column at several sites covering fragments of relict fluvial forms, i. e. paleovalleys. Three sites with different mesorelief and structure of the upper part of the loose sediment section were studied, covering fragments of paleovalleys at depths from 40 to 250 m. It was established that there are special degassing conditions in the paleovalleys of the southwestern part of the Kara Sea shelf, which are predetermined by the relief and geocryological structure of the bottom. Vertical migration of fluids from deep horizons leads to their accumulation at the bottom surface, where their uneven unloading occurs, depending on the combination of geomorphologic and geocryological conditions. Permafrost layer, which are a powerful fluid seal, are developed fragmentarily in the valleys. The concentration of gas shows increases in areas of their wedging out. Based on seismoacoustic and bathymetric data, pockmarks, pingo-like forms, dome-shaped uplifts, and mud volcanic formations were identified resulting from the fluidogenic discharge. The spectrum of fluidogenic forms developed in paleovalleys is determined by the morphology of the relief and their depth: pockmarks and mud volcanic structures are more typical for valley bottoms, where frozen rocks are distributed fragmentarily or are completely absent. Pingo-like forms (PLF) are found on the slopes of valleys where the thickness and cohesion of permafrost decreases. Mud diapirsdome-shaped uplifts are developed in the areas with almost complete absence of permafrost. Outside the valleys, gas shows and fluidogenic forms are isolated, which is associated with the presence of a fluid seal in the form of a permafrost layer. The results of the study allowed to establish that paleovalleys are the main fluid discharge zones on the shelf of the Kara Sea, and the permafrost degradation, including under the influence of fluid migration, determines the modern microrelief and dynamics of the processes. The data obtained are consistent with studies in other Arctic regions (the Beaufort Sea shelf, the Mackenzie River delta), thus confirming the universality of the mechanisms of interaction between permafrost and fluid flow within the shelf zone of the Arctic.

The active development of the western macroslope of the Susunai range (deforestation, construction of a gas pipeline, ski slopes, slopes grading for various linear and permanent structures), as well the fact that the woody vegetation in the river basins rising in the Susunai range was partly damaged by windstorms, have led to the increase in dangerous exogenous geodynamic processes, including the debris flows. Thereby the susceptibility of the territory of the Yuzhno-Sakhalinsk urban district to debris flow processes was studied comprehensively.
For the area, a reconnaissance survey of the debris flow basins formed on the western macroslope of the Susunai range after a period of mass debris flows of 31.08–01.092023, was performed; signs and traces of debris flows were recorded, as well as individual parameters of debris flows based on direct signs. The initial data on the debris flow processes and forming factors within the studied area were collected and analyzed, such as archival and file materials, scientific publications, engineering survey materials, and field work results. During the field work on the studied territory a complex of natural and territorial conditions promoting the debris flows formation was identified, including geomorphologic, geological, hydrometeorologic, geobotanical and anthropogenic factors. The debris flow regime of the territory was revealed as a main scientific result of the work. Application of an instrumental method (measurements of a network of automatic precipitation meters) and analysis of the data obtained showed the absence of a pronounced altitudinal gradient of daily precipitation maxima. At the same time, the archival data confirm the dependence of precipitation amounts on the hypsometric levels for the longer observation periods, i.e. monthly and annual ones.
After completing a complex of field work, including instrumental measurements, and determining the natural and territorial conditions of debris flow formation and the debris flow regime of the territory, the data were processed in the laboratory and the main scientific and practical results were obtained. The parameters of the debris flow and the main dynamic characteristics of emerging debris flows were calculated based on the current technical standards. The debris flow-prone zones were identified and the address list of objects located in debris flow-prone zones was compiled.

The current climate change in the Arctic has a significant impact on permafrost situation of the region, which, in its turn, determines the growth conditions of aboveground vegetation cover. The work is devoted to identifying spatial patterns in environmental conditions of tundra vegetation growth, topography, surface deposits and permafrost conditions for a study area within the Chukotka Peninsula. The results of field survey, supplemented by the analysis of long-term trends of the NDVI vegetation index and correlated with long-term monitoring data on the active layer thickness and projective cover of vegetation, made it possible to reveal the current evolution of the vegetation cover as a result of climate change and anthropogenic impact. A spatial sequence of plant communities was lined up, reflecting the range of NDVI values within the study area. A weak (up to 0,3 for 20 years) but stable increase in NDVI values was revealed for the entire study area. Within plains the increase in vegetation growth intensity over the past 20 years is generally confined to the topographic depressions formed both under the influence of natural conditions and the anthropogenic impact. In the long-term the latter could become a driver of bioproductivity, since it increases the roughness of the surface. The results show that under climate warming in the Arctic the dynamics of permafrost conditions in the cryolithic zone is the leading factor determining the change in the growing conditions of tundra vegetation in the Chukotka Peninsula.

Climate change in the Arctic intensifies cryogenic relief-forming processes. Thermal denudation in northern Eurasia and North America, where wedge and tabular ground ice are widespread, occurs as a process that combines the melting of ice and frozen ground thawing accompanied by the downslope movement of thawed material. The result of the process is the formation of thermocirques and thermoterraces. Using remote sensing data with interactive interpretation and machine learning techniques, global databases of these landformsʼ distribution are being developed. The published databases provide new opportunities of further analyzing the spatial manifestations of the phenomena. The authors propose an explanation of the natural conditions and causes that determine the uneven distribution of thermocirques and thermoterraces on the Yamal Peninsula, as well as their future development under the changing conditions. The source data include the DARTS database of thermal denudation landforms in the Arctic, as well as information on the ice content in the upper layers of deposits, the distribution of ice wedges and tabular ground ice, and the relief dissection. To assess how changing permafrost conditions amplify thermal denudation, we used data on the changes of ground temperature at a depth of 2 m and the thickness of the active (seasonally thawed) layer from 1997 to 2021. We found that the presence of near-surface ground ice is a necessary but insufficient condition for the formation of thermocirques and thermoterraces. A key factor of their emergence and long-term activity is the vertical relief dissection, which enables the removal of thawed material from retreating headwalls to the local base of erosion. The authors have subdivided the Yamal Peninsula into zones based on the current intensity of thermal denudation. Four zones were identified, differing in the spatial density of thermal denudation landforms and in their predicted future development. These differences are determined by the cryogenic structure of the deposits, relief parameters and changes in the permafrost conditions.

The paper presents the results of studying the invasive diatom species in the sediments’ surface layer of the Norwegian, Greenland and Barents seas. The Redundancy Analysis (RDA) method helped to identify the main environmental factors influencing the distribution of invasive diatoms. The duration of sea-ice cover and the position of the marginal ice zone within the study area are the principal ones. The geographic distribution of invasive diatom species was established. The North Pacific species Neodenticula seminae was found only in the North Atlantic, its distribution is limited to 12–15° EL. The presence of relatively warm-water diatom species Shionodiscus oestrupii, Coscinodiscus radiatus and C. asteromphalus is associated with the penetration of warm Atlantic currents. The distribution of sea-ice and ice-neritic species directly depends on the location of the seasonal sea-ice cover. High contents of sea-ice (up to 30%) and ice-neritic (more than 45%) diatom species in sediments may indicate the proximity of the sea ice boundary in the recent geological past, while low contents (about 2 and 15%, respectively) indicate their invasion by currents or as a result of iceberg transport. The results show that invasive diatom species could be used as paleomarkers of the paleoceanological changes, affecting the intensity of warm Atlantic water influx into the Arctic, and the boundaries of seasonal sea-ice cover and the marginal ice zone.

During the Early Khvalynian stage, fluctuations of the Caspian Sea level formed a number of marine terraces, which are well pronounced in the relief of the northern part of the Caspian Lowland. The paper presents the results of studies of the lithological structure and radiocarbon age of the sediments that correspond to the maximum Early Khvalynian terrace at the northern edge of the Caspian Lowland (north-east of the Volgograd Region). The results obtained from studying the sediments in NP-1 and NP-2 boreholes within the Eeruslan River valley showed that the upper layers of sediments that correspond to the maximum Early Khvalynian terrace accumulated in subaerial conditions during the period of 26,7–19,5 ka cal BP. The composition of the sediments formed during that time interval is almost uniform. These features suggest stable conditions of their accumulation with a permanent supply of silt-sand material. During the last glacial maximum, the Early Khvalynian basin was probably located at elevations significantly lower than 40 m a.s.l. The subsequent rise in the Caspian Sea level and erosion of the upper part of subaerial deposits resulted in the isolation of the maximum Early Khvalynian terrace as a relief form.

The study presents a comparative analysis of the morphological and physical properties of never-ploughed automorphic chernozem profiles from the long-term pastures and hayfields, as well as virgin chernozems from protected meadow-steppe landscapes (nature reserves) in the forest-steppe zone of the Central Russian Upland. The similarities in key characteristics, including the thickness of chernic and chernic+mollic horizons, the intensity of zoogenic turbations, the vertical distribution of mole rat burrows, the particle-size distribution and bulk density were revealed. The differences were observed in the upper soil layers: chernozems from pastures and hayfields show higher compaction and lower total porosity compared to their protected counterparts. The Central Russian Upland’s forest-steppe region has very few undisturbed, high-quality chernozems left due to agricultural use, so we suggest considering unploughed pasture and hayfield chernozems as a close-to-natural reference or benchmark ones to compare them with anthropogenically transformed soils located nearby.

The plant-animal interactions are among the most important problems to analyze in biogeography and ecology. A key research area is endozoochory, the study of which allows identifying the local dynamics of plant communities, as well as revealing and modelling long-distance dispersal pathways, enabling plants to colonize new areas and migrate in response to environmental changes. The subfamily Coryphoideae (Arecaceae, или Palmae), the most widespread subfamily of palms, was chosen as an object of study. Palms are an extensively studied group, but despite the increasing number of detailed investigations, data on Coryphoideae fruits and their dispersal processes remain incomplete. Therefore, there is a significant need for a detailed study of the dispersal modes of coryphoid palms and their adaptations to dissemination. The aim of our study is to identify and analyze the fruit structure traits in Coryphoideae species distributed across different regions of the world and adapted to dissemination by various dispersal agents. The morphological and anatomical structure traits of 25 model coryphoid palm species were studied using standard comparative carpological and carpobiological methods. We revealed that fruits of the studied species demonstrated significant morphological and anatomical adaptations to endozoochorous dissemination attracting various dissemination agents (fruit colour and size, nutrients supply in the pericarp cells) and ensuring seed protection (sclerified structures and raphides in the mesocarp). We presume that among the studied taxa, species forming small or medium-sized, contrast-coloured fruits with protective structures in the pericarp are the most adapted to endozoochory. Adaptations to endozoochorous dispersal are less effective in Coryphoideae species with large, dull-coloured fruits and just an outer belt of sclereids in the mesocarp.