The paper examines the stable oxygen isotope values for six most abundant ostracod taxa in present-day Caspian Sea bottom sediments from 33 sampling sites. The oxygen isotopic composition of Caspian ostracod shells was found to reflect metabolic effects related to their life cycle. The average δ18Oost value (± standard deviation) for each species is as follows: −0,11‰ (±0,7) for Euxinocythere virgata, –0,25‰ (±1,14) for Tyrrhenocythere amnicola donetziensis, +2,94‰ (±0,16) for Candona schweyeri, +1,55‰ (±1,12) for Paracyprideis sp., +1,77‰ (±0,22) for Bakunella dorsoarcuata and +2,45‰ (±0,95) for Camptocypria sp. The results obtained confirmed that Caspian ostracods do not secrete their carapace in equilibrium with the surrounding water. Rather, the studied species showed a positive vital offset – the observed effect averaged about 1‰ (±0,5). The desired isotopic shift for the mixed ostracod assemblage turned out to be equivalent to the average isotopic shift for the studied sample and amounted to +1‰ (±0,5). The work demonstrates that ostracod metabolic processes cause shifts in the expected fractionation of oxygen isotopes between CaCO3 and water. The resulting isotope offsets must be taken into account in paleogeographic studies for correct interpretation of paleoclimatic changes in the Caspian Sea region using the stable oxygen isotope record.

The relationship between climate change in the Late Holocene and evolution of Korean pine forests in the mid-mountain zone of the Sikhote-Alin Biosphere Reserve has been studied. Under moderately warm climate about 2640 cal BP Korean pine-oak formations, with admixture of Ayan spruce (Picea ajanensis (Lindl. et Gord.)), Khingam fir (Abies nephrolepis (Trautv.) Maxim.), and broad-leaved species, birches, alder and larch, developed in place of the modern Korean pine forests. With maximum warming around 2280 cal BP, maximum watering of the Nizhnee Lake occurred; its area increased and the aquatic and coastal-aquatic vegetation developed actively. Rising average annual and average summer temperatures contributed to a decrease in the position of Korean pine (Pinus koraiensis Sieb. Et Zucc.) as a dominant in phytocenoses and stronger presence of Mongolian oak (Quercus mongolica Fisch. ex Ledeb). Climate breakdown around 2050 cal BP have led to the replacement of coniferous-broad-leaved forest by the Korean pine forests formation, which turned out to be a completely stable system within the Sikhote-Alin Nature Reserve and existed until the middle of the 17th century, when the coldest conditions for the last 2640 cal BP (the Maunder minimum of solar activity) occurred. At that time the limit of dark coniferous forests on the slopes surrounding the Nizhnee Lake became lower and spruce forest with Korean pine and small admixture of birch and broad-leaved trees got wider spread. Under more comfort climate conditions the spruce forest was replaced first by spruce-fir forests with Korean pine and an admixture of broad-leaved trees, and then, under modern warming conditions, by the Korean pine forest with some dark conifers and a rare admixture of broad-leaved trees. The driest period during the time interval under study occurred at approximately 2330 cal BP. The lake level decreased significantly at that time, and it was overgrown with sedge-grass family communities. Active overgrowing began when the groundwater level decreased during cooling and a significant reduction in the amount of atmospheric precipitation at about 1500 cal BP. Climate-induced successions of Korean pine forests of the Sikhote-Alin Nature Reserve reflect regional patterns of development of such forest communities and could be correlated with global paleoclimatic events.

The gas-aerosol composition of the atmosphere determines specific features of the radiative net irradiance in the atmosphere and the associated climatic changes. The study discusses the anthropogenic variations in the content of the most important greenhouse gases, such as carbon dioxide (CO2) and ozone (O3), as well as the atmospheric aerosol. The estimates of their radiative effects (forcing, RF) in various geophysical conditions are given. Based on the modern ECRAD radiation model, the RF values of considered anthropogenic trace gases and aerosols over the past 20 years were estimated for different seasons of the year relative to their preindustrial level for the Moscow region. We determined specific features of the vertical profiles of RF in the shortwave and longwave spectral ranges and their values at the bottom (BOA) and the top of the atmosphere (TOA) depending on solar elevation and surface albedo, both taking seasonal variations into account and without them. The total RF Total for the warm period with a low surface albedo is negative (–8,33 W/m2 at BOA and –1,35 W/m2 at TOA) if seasonal variations of all considering trace gases and aerosols are taken into account. A weakly absorbing aerosol typical of mid-latitudes plays a significant role in the negative RF. The RF Total for the cold season is –0,08 W/m2 at BOA and +0,38 W/m2 at TOA. The positive value of the total RF at the TOA is due to the positive RF of the aerosol with its absorbing properties and the influence of the high albedo of snow surface, as well as due to the positive RF of carbon dioxide. A nonlinear RF dependence of the trace gases and aerosol on the solar elevation and surface albedo was found. The radiative heating rate due to greenhouse gases at TOA is negative in all seasons of the year. At the same time, it is positive at BOA (about 0,45 K/day in the warm season and 0,25 K/day in the cold season), mainly due to the absorption by aerosol in the lower layers of the troposphere. The radiative heating rate due to CO2 is slightly positive.

The analysis of the spatial structure of landscapes of arid highlands was carried out by combinations of se veral morphometric characteristics based on the high-resolution remote sensing data. The choice of the Mongun Taiga Mountains located in the west of the Republic of Tyva (Russia), as a model site, is due to the possibility of verifying the results of morphometric analysis using the extensive material from long-term field studies of the massif. It is shown that the territory could be split into sections relatively homogeneous in terms of relief morphometric parameters in order to describe the locations with a sufficiently high accuracy. It has been established that the entropy of the distribution of plant community groups, averaged over altitudinal intervals, significantly decreases when locations are identified based on combinations of morphometric values for the entire altitudinal profile, regardless of the macroslope. Combining field trials, cartographic and remote sensing methods makes it possible to assert that proposed set of morphometric characteristics is able to output plant cover horizontal structure. It can be used for automatic interpretation of hardly accessible areas of Inner Asia as well as for the forecast of landscape structure transformation as a result of spontaneous or human-induced changes.

Along the perimeter of the Far East region of Russia, a formed closed transport and economic structure has been identified. It can be described as the Great Far Eastern Transport and Economic Ring (GFETER). Four large segments are identified and considered in its composition: the latitudinal Southern and Arctic marine, as well as the meridional Western and Pacific marine. They are large interacting parts of the general territorial and aqua-territorial transport and economic structure, which consists of linear links represented by communication routes, nodes - settlements that perform certain transport and other functions, territorial and water zones of gravity to these structural elements. The analysis of the current state of the spatial structure of GFETER was carried out. This formation serves the most important passenger and cargo transportation - from intra-regional to inter-regional and transit, provides various forms of spatial development of the Far East region.The transport specialization of the elements of this spatial structure of the GFETER is shown. The linear elements of the GFETER segments perform transport functions. Transport nodes in general perform more diverse functions determined by the action of a combination of factors: economic-geographical and transport-geographical position, geodemographic, scientific, technical and natural resource potentials, natural and climatic conditions. The main functions of the GFETER transport hubs are highlighted. The Vladivostok agglomeration hub occupies a special place among them. The significance of the GFETER for the Far East is due to the fact that its segments include territories and water areas where large natural resources are being developed. In the long term, various forms of spatial development of this structure are possible, including the construction of an Arctic railway line and a railway along the river. Lena. The construction of various transport links along the Pacific coast is also expedient. All this will initiate new forms of spatial development of the Far East region as a whole.The development of a transport perimeter in the form of a GFETER significantly expands the prospects for the long-term integrated development of the region, improves the coordination and interaction of various modes of transport, and increases the degree of its regularity and reliability. This is especially true in view of the vast distances and growing volumes of traffic. The logistics potential inherent in GFETER can significantly strengthen Russia’s position in international transportation and cooperation.

The article analyses landscape factors that determine the runoff of small Arctic and Subarctic rivers in the far northeast of Asia. The paper considers hydrography, structure of permafrost landscapes and their hydro-chemical characteristics, and the spatial dynamics of low-water runoff in the basins of the Ugolnaya-Dionisiya and Yanranayvaam rivers. It has been established that sustainable water intake depends on the ratio of land-scapes generating and depositing the permafrost runoff, namely Arctic char gravelly shrub tundra, lowland tussock tundra and hummock swamps. The low-water runoff of 20-50 l/km2·sec is typical for the sources of rivers, where seasonal char ice melts in the slope deposits and condensation waters are formed. Melt water of sea-sonal intra-surface soil ice on the gentle slopes of tundra hummocks provides specific runoff of 10-20 l/km2·sec. Upland and lowland marshes deposit above-frozen waters, and their runoff is less than 10 l/km2ˑsec. Using the example of two catchment basins, it is shown that the decrease in precipitation in the north of Chukotka is almost completely compensated by the formation of condensation waters. At the same time, inground seasonal infiltration soil ice is replaced in Arctic landscapes by infiltration-condensation char ice, and its melt water makes up for the loss of surface runoff.

The vertical and lateral distribution of iodine and selenium in the soils on different types of parent material, i. e. loesslike loams and fluvioglacial sands and sandy loams, was studied within associated landscape-geochemical systems of the Titovka River basin (Bryansk region, Russia). It was found that the content of both elements in particular genetic horizons of the studied soils under the contrasting environment varies widely, namely I: 0,22-7,93 mg/kg, n = 93, and Se: 0,001-0,668 mg/kg, n = 93, airdry mass. Gray forest loamy soil on loesslike loams contains 2 times more iodine and almost 4 times more selenium than sodpodzolic sandy loam soil on binary deposits (1,67 / 0,81 mg/kg for I (p < 0,05); 0,453 / 0,120 mg/kg for Se (p < 0,05), respectively).This may be due to both the type of parent material and higher content of organic matter, and the lighter texture of gray forest soils. The content of iodine and selenium in bottom sediments of the Titovka River (0,59 and 0,36 mg/kg of airdry mass) is most comparable with the upper horizon of sodcarbonategley soil sampled a few meters from the sampling site of bottom sediments (I - 0,57 mg/kg; Se - 0,35 mg/kg of airdry mass). At the same time, the elements showed dissimilar differentiation in soil horizons, due to their affinity to geochemical barriers. Iodine is actively fixed on the alkaline-carbonate barrier and is mobile under reducing conditions, while selenium concentrates on the gleyic barrier and is mobile in an oxidizing environment. This should be taken into account when assessing the availability of these biologically significant chemical elements in soils and local food products, particularly in the areas exposed to radioactive isotopes of iodine.

Based on the results of geomorphologic surveys carried out in 2021-2022 with the involvement of published materials, an original largescale (from 1:25 000 to 1:100 000) description of relief of urban areas of the Republic of Abkhazia (Gagra, Pitsunda, Gudauta, Noviy Afon and Sukhum) was compiled, and unprec-edented general geomorphologic maps were prepared, with morphogenesis-based legends. According to their morphostructure position and geomorphologic structure, the cities are grouped as follows: 1) completely lying in the area of the coastalmarine relief (Pitsunda and Gudauta); 2) located mainly within the sea terraces and erosion-denudation hills (Sukhum and Gagra); 3) completely located in the low mountains with a predominance of strongly dissected structural-denudation, fluvial and slope relief (Noviy Afon). A field survey revealed about 300 areas with unfavorable and dangerous geomorphologic processes within the urban areas, 44% of them are in Sukhum, 26% in Gudauta, 11% in Gagra, 10% in Pitsunda, 9% in Noviy Afon. The leading geo-morphologic hazards in all spectra are suffusion, erosion and biogenic processes. A list of other processes in a spectrum is predetermined by the geomorphologic position of cities. The widest range, which in addition to the abovementioned processes, includes also karst, mudflows and landslide processes (i.e. the most dangerous ones), is typical for urban areas with a complex relief structure, abundant in steep slopes and located within a narrow strip separating the spurs of the Main Caucasian Range from the sea (Gagra, Noviy Afon). The risk of destruction of street infrastructure (roadbed, communications, etc.) by dangerous geomorphologic processes was qualitatively estimated and its high dependence on the geomorphologic position of a particular section of the city has been established. In particular, the distribution patterns of recorded unfavorable and dangerous geomorphologic processes made it possible to state that the most favorable conditions for the construction and operation of urban infrastructure and buildings in general are within the leveled surfaces of the Late Pleistocene marine terraces, as well as the upper levels of floodplain terraces in the valleys of large rivers. Other levels of relief have certain disadvantages that impede the development of territories. Thus, the construction on the surface of the Holocene marine terrace is possible only if the foundations are waterproofed and soil is dumped in the lower areas. The development of high sea terraces, erosion-denudation and structural-denudation relief is difficult because of the high density of erosion dissection.