Classification of coastal vegetation from the standpoint of the ecological-phytocoenotic approach at the estuary of the Indiga River, flowing into the southeastern part of the Barents Sea, is presented. On the base of 131 relevés of coastal vegetation, 23 associations in 18 formations were identified. The coastal vegetation in different biotopes differs in the structure and features of the phytocoenoses floristic composition. Based on the signs of vegetation cover, mesorelief, and hydrological features of the shores, the following biotopes were identified: saline and brackish marshes, beaches and dunes, tidal flats at the mouths of estuaries, saline and brackish lagoon lakes on marshes. The marches with 14 described associations have the highest phytocoenotic diversity. A phytocoenotic diversity of the beaches is noticeably less, 4 associations are described there. The vegetation background of the beaches is formed by the communities of the Leymeta arenarii formation, the vegetation background of the salty marshes is formed by the communities of the Cariceta subspathaceae, Cariceta glareosae, and Cariceta mackenziei formations. In saline lakes, large areas are occupied by communities of the Hippurideta tetraphyllae formation, and the communities of the Triglochineta maritimi and Plantagineta subpolaris formations are rare, the northern limit of their range runs approximately along the Indiga mouth. The vegetation of brackish marshes is mainly formed by the Cariceta salinae herbosum, Junceta gerardii, and Cariceta rariflorae communities. At the mouth of Indiga estuary, large areas are occupied by communities of the Magnocariceta formation. In the mouth of the Indiga, a little north of the range limit, communities of Eleocharis uniglumis, a rare species in the Nenets Autonomous Okrug, are described for the first time at the rank of association Eleocharitetum uniglumis. The aquatic vegetation of desalinated lagoon lakes is represented by the Myriophylleta sibirici formation. The halophyte vegetation of the Indiga River estuary is compared with the estuaries of the rivers of the Kanin Peninsula and the Pechora Bay. The ordination of geobotanical relevés shows a greater similarity of the coastal vegetation of the Indiga estuary with the estuaries of the rivers flowing on the Kanin Peninsula of the White and Barents Seas basins and with the vegetation of the rivers estuaries of the Pechora Bay coast. The article has an electronic appendix (https://journals.rcsi.science/0006-8136/issue/archive).

The article analyzes distribution of 94 species of aquatic plants in 18 lakes, different in size, origin, trophic status, hydrological and hydrochemical conditions. Macrophytes and their communities were studied in 11 large and small lakes in the Kenozersky National Park, in 2 large lakes in the Onezhskoye Pomorye National Park, and in 5 small lakes in the Pinezhsky State Nature Reserve. The eutrophic lake Porzhenskoye in the Kenozersky National Park stands out with the greatest species number, 52 species. Fewer species of macrophytes were identified in oligotrophic lakes. It is shown that the majority of aquatic plants of the Arkhangelsk Region inhabit narrow range from low to medium total dissolved solids – 54 species. Eurybiont species, occurring in a large range of total dissolved solids from 1 to 1020 mg/l, show a great species diversity – 24 species. Only 11 species tend to grow in karst lakes with elevated level of total dissolved solids from 500 to 1020 mg/l – vascular plants: Ranunculus kauffmannii, Eleocharis acicularis, E. quinqueflora, Myriophyllum verticillatum, Potamogeton obtusifolius, Stuckenia pectinata, Sparganium hyperboreum; mosses: Calliergon cordifolium, Scorpidium scorpioides; algae: Chara aspera, C. subspinosa. The majority of species in the lakes of specially protected natural areas of the Arkhangelsk Region, growing in a narrow water pH range, are neutrophytes – 31 and neutro-alkalophytes – 27. Thirteen protected species of macrophytes were discovered in the flora of lakes in the Arkhangelsk Region – Chara aspera, C. strigosa, C. subspinosa, C. virgata, Fissidens fontanus, Fontinalis dalecarlica, F. hypnoides, Isoëtes echinospora, I. lacustris, Lobelia dortmanna, Nymphaea candida, N. tetragona, Sparganium gramineum.

The specific features of the soil–vegetation heterogeneity at the early stages of restorative succession have been studied. These features are determined by biotic and bioinert conditions that were influenced by anthropogenic factors during long-term plowing on azonal carbonated soils in the middle taiga subzone (Kargopol district, Arkhangelsk Oblast, Russia). In total, 25 full-profile soil sections, 500 soil samples, 125 sites for counting tree and shrub species, 25 standard geobotanical plots, and 250 plots for counting herbaceous species have been studied and analyzed. During the first 15 years of restorative succession on fallow agricultural land, herbaceous vegetation has the highest phytocenotic significance. On the residual calcareous soils of the forest zone, the specialization of ecological properties, i.e., the confinement of species to certain factors is weakly pronounced only in some herbaceous species. The mosaic structure of vegetation cover on a 15-year-old fallow is determined not by the variability of soil properties and the influence of growing tree and shrub species, but by the biological properties of herbaceous plants and their specific requirements for environmental factors. Soil fertility and soil moisture are the main factors that determine the variations of vegetation at this stage.

Geobotanical studies of the coastal halophilous vegetation are carried out on the southern coast of the Pechora Bay (the Barents Sea region). The ecological-phytocenotic approach is applied for classification; in total, 11 plant associations (including 2 subassociations) belonging to 10 formations are described. The syntaxa are identified considering 94 original geobotanical descriptions. In the article, the classification is limited to two leading syntaxonomic units: (1) formation, distinguished by the type of phytocenosis edificator species and (2) association, distinguished by the dominant species of the upper and lower tiers, which are defined as the diagnostic category. The vegetation cover differed in composition and structure in the habitats with different ecological conditions, such as beaches and foredunes, salt and brackish marshes, brackish water bodies on the marshes, ecotone zones between marshes, and shrub tundra. On the beach sands, there were communities of two associations: Leymetum arenarii honckenyosum diffusae and Leymetum arenarii latirosum japonici. The salt marshes were covered with the halophilous vegetation of the four associations: Caricetum subspathaceae potentillosum egedii, Caricetum glareosae potentillosum egedii, Festucetum rubrae potentillosum egedii, and Caricetum mackenziei. In the brackish marshes, there were communities of associations of Rumexetum aquaticus, Glycerietum fluitantis subpurum, and Arctophiletum fulvae. The small brackish lakes were occupied by the communities of Hippuridetum tetraphyllae. The communities of Salicetum reptantis parnassiosum palustris association are described in the ecotone zones between the marshes and shrub tundra. The original data on the marshe syntaxa described by the ecological-phytocenotic approach are compared with the previously published data on those from the Bolshezemelskaya tundra, but identified using the ecological-floristic approach. For the first time, the vegetation of marshes and beaches at the mouth of the Dresvyanka River is described. The article expands the information about the distribution of beach communities of the Leymeta arenaria formation, and the communities of marshes of the Caricetum subspathaceae, Caricetum glareosae, Festucetum rubrae potentillosum egedae, Hippuridetum tetraphyllae, Rumexetum aquaticus, and Arctophiletum fulvae associations. New information about the composition and structure of the Glycerietum fluitantis subpurum association is presented; these communities are first described earlier by the authors outside the northern border of the range of the coenose-forming plant Glyceria fluitans, in the south of the Pechora Bay, at the mouth of the Khylchuyu River. These communities together with the coenose-forming plant Glyceria fluitans require protection in the Nenets Autonomous Okrug.

This article provides a quantitative evaluation of aspects of the spatial heterogeneity of soil and vegetation cover of floodplains in relation to the microrelief using the example of floodplains of the Northern Dvina River delta. It is detected that the soil and vegetation cover of the floodplain meadows in the Northern Dvina Delta is a feature of a relief on a microlandscape level. This dependence displays itself in the specific structural features of some ingredients of the soil and vegetation cover. Due to the intrazonal localization of floodplain ecosystems, the results of a local survey, for example, in Arkhangelsk oblast of Russia, can be extrapolated to other regions of the country and the world. The relevance of the study of heterogeneity of soil and vegetation cover is based not only on fundamental aspects, but also on the needs of agricultural management.