The article discusses the current level of species diversity of the flora of the city of Bryansk, on the base of the iNaturalist platform. In the project «Flora of Bryansk» 942 species of vascular plants are registered. A critical analysis of the list of species was carried out, thr conclusions about the dynamics of the flora of the city were made. As a result, the studies flora of Bryansk discovered previously unknown locations of rare species of vascular plants, included in the Red Data Book of the Bryansk Region (Krasnaia..., 2016), and a list of species requiring additional observation and monitoring.

An overview of Russian literature sources of urban flora studies. The authors analyze the history of urban floral research in Russia and provide definitions of terms – urban flora, native, indigenous, apophytic, alien, synanthropic species. The overview provides a description of methods and approaches used in different studies of urban flora. Special attention is paid to the analysis of the biological diversity of native and alien plants and the features of their spatial distribution in urban habitats. The authors raise problems of protection of biodiversity in cities and show the role of urban protected natural areas. The conclusion of the work outlines the prospects for further study of urban flora. The authors highlight an importance and necessity of creation of a unified database of vascular plants in the urbanized territories of Russia. Further usage of the database will allow to conduct a comparative analysis of the species composition of urban flora and to identify the degree of their homogenization and originality.

Thladiantha dubia Bunge is an East Asian species, a perennial herbaceous climbing vine, which naturally grows in the Russian Far East, in Northeast China, and on the Korean Peninsula. It is a secondary species in Central Europe, North America, South America (Ecuador), and Japan. Th. dubia is not an invasive plant for the majority of European countries. Th. dubia is bred in the European part of Russia as an ornamental plant, and it is found in a variety of disturbed habitats. In some regions of Russia, it has an invasive status. The distribution of Th. dubia in Bryansk Region was studied using grid mapping. The species was observed in 69 out of 223 examined squares (30.94%). Th. dubia occurs in disturbed habitats, wastelands, and homes. We have discovered and studied communities dominated by Th. dubia. The species forms monodominant resistant communities in anthropogenic habitats. On the basis of the analysis of geobotanical descriptions of the communities, we established the association Thladianthetum dubiae ass. nov. The formation of a monodominant community is possible owing to vegetative propagation and decrease in the illumination of the soil cover. Th. dubia secretes growth inhibitors, colins. Presumably, an invasion vector of Th. dubia is anthropochoria. Th. dubia is a potentially invasive species for Bryansk Region. The biomass of the plant is characterized by a good absorption capacity of some heavy metals, and it can be used as a soil remediator.

The paper presents the results of a comparative analysis of the floristic and phytocoenotic diversity within widespread association of acute sedge meadows Caricetum gracilis Savich 1926 in the floodplain of the Desna River (Bryansk and Smolensk regions, Russia). Available geobotanical data on Desna floodplain, collected in the last 40 years, allowed identifying the main dynamic trends in the syntaxonomical space. Based on 36 relevés made by the authors in 1975–1990 previously (Bulokhov, 2001) 3 subassociations, which communities were prevalent in the Desna valley, were established: Caricetum gracilis typicum, С. g. oenanthetosum aquaticae, С. g. beckmannietosum eruciformis. As a survey of the Desna floodplain in 2015–2018 showed, both flow decrease and drop in the level of spring flood and groundwater in the XXI century have led to a change in the appearance, floristic composition, and structure of acute sedge meadows. Xerophytization of the floodplain resulted in the disappearance of the С. g. oenanthetosum aquaticae and С. g. beckmannietosum eruciformis communities. Drying of typical habitats of moist acute sedge meadows became the background of the formation of diverse communities of other types in their place. In the coenoflors of these communities changes occurred at the class level from Phragmito-Magnocaricetea Klika in Klika et Novák 1941 to Molinio-Arrhenatheretea Tx. 1937. Two groups of communities have been formed. The first group is represented by syntaxa of the alliance Magnocaricion gracilis (class Phragmito-Magnocaricetea): Caricetum gracilis typicum with variant Achillea salicifolia as well as by the communities Lythrum salicaria, Calystegia sepium, Calamagrostis canescens. The share of the alliance characteristic species in their coenofloras is 54–64%, and Carex acuta, as a rule, dominates. The second group represents the communities of wet meadows (order Molinietalia caeruleae) of the class Molinio-Arrhenatheretea. The alliance Deschampsion cespitosae is established with subass. Poo palustris–Alopecuretum pratensis typicum (with three variants: Veronica longifolia, Hierochloё odorata, Galium physocarpum) and three communities (Cirsium arvense, Lysimachia vulgaris, Stachys palustris) The share of characteristic species of the order in their coenofloras is 58–95%. All communities and variants form series along the moisture gradient in habitats of acute sedge meadows. Communities Lythrum salicaria, Calystegia sepium, Calamagrostis canescens are distributed in the wettest and richest in mineral nitrogen habitats in the Middle Desna area, in the former long-flooded low-level floodplain. The other ones occur, first of all, in the Upper and Middle Desna areas on a short- and long-flooded floodplain of an average level. These communities are forming on moist and fresh soils. The variants and communities on the gradients of moisture and the richness of mineral nitrogen of the soil were ordinated using the ecological scales of H. Ellenberg et al. (1992). Serial communities form an ecological-dynamic sere on a humidity gradient, showing the direction of their dynamics. The same localization of studies carried out both in 1975–1990 and in 2015–2018 identified changes in vascular plant coenoflora of the ass. Caricetum gracilis for this period: from 62 species in 1975–1990 to 143 species in 2015–2018. There are three groups of species, which reflects these changes. Besides species affine to the class Phragmito-Magnocaricetea, numerous meadow herbs of the class Molinio-Arrhenatheretea appeared: Agrimonia eupatoria, Agrostis tenuis, Bromopsis inermis, Carex praecox, Dactilys glomerata, Dianthus deltoides, Elytrigia repens, Equisetum arvense, Festuca pratensis, Galium mollugo, Geranium pratense, Galium physocarpum, Hieracium umbellatum, Hierochloё odorata, Lathyrus pratensis, Odontites vulgaris, Poa pratensis, Potentilla argentea, Potentilla erecta, Phleum pratense, Vicia cracca. A complex of ruderal explerent and nitrophilous species with numerous alien ones has been formed: Bidens frondosa, Chamaenerion angustifolium, Cirsium arvense, Echinocystis lobata, Epilobium adenocaulon, E. collinum, E. pseudorubescens, E. tetragonum, Erigeron annuus, E. canadensis, Lactuca serriola, Linaria vulgaris, Senecio jacobaea, Sonchus arvensis. Most of these species are anemoсhores, and their presence in the sedge communities is associated with open site formation due to the soil drying between hummocks, as well as the destruction of sedge tussocks under drying and fire. Over the past decade invasive species Bidens frondosa, Erigeron annuus subsp. septentrionalis, E. canadensis,and Lactuca serriola have become an ordinary component of the Desna’s river valley flora. Trees and shrubs (Acer negundo, Betula pendula, Frangula alnus, Quercus robur, Rosa majalis, Salix cinerea, S. pentandra, Swida alba) enter into meadow communities because the lack of haymowing. The following changes in the life form spectrum took place due to the floodplain xerophytization and acute sedge meadow transformation: the proportion of long-rhizome species decreased, while that of rod-root, short-rhizome, and annuals increased; trees and shrubs appeared. Obvious also are changes in the ecobiomorphspectrum: the proportion of mesomorphic species increased, that of hygromophic and mesogygromorphic ones decreased; xero-mesomorphic plants appeared.

The distribution and phytocenotic association of Parthenocissus vitacea and Vinca minor on the territory of the Bryansk oblast has been studied. An assessment of the distribution of invasive species is performed on a grid basis. Vinca minor is registered in 19 cells on the territory of the oblast, which is 4.9% of the total number of cells and 11.9% of the surveyed cells; Parthenocissus vitacea is registered in 50 cells, which is 12.8% of the total number of cells and 31.2% of the surveyed cells. The invasive status of Parthenocissus vitacea and Vinca minor is category 3: an adventive species whose invasions into natural and seminatural habitats in the region at the moment are rare and, as a rule, confined to the outskirts of populated areas, abandoned parks, and old plantings. The indices of successful invasion in forest communities is the formation of syntaxonomically valid variants of the communities of Corylo avellanae-Pinetum sylvestris Bulokhov et Solomeshch 2003 with depleted cenoflora. Invasive species change the phytosphere and reliably decrease the indices of α and β diversity, the structural indices of communities. The invasion of Parthenocissus vitacea and Vinca minor is successful due to active vegetative reproduction, allelopathic effects on native species, and decreasing illumination of the ground cover. The introduction of invasive species into complex pine forests blocks demutational changes of endogenous succession during the restoration of broad-leaved forests: they simplify the structure of communities and reduce the intensity of the mosaic. Parthenocissus vitacea and Vinca minor can exhibit signs of an edificator, a community builder, and a violent and transformer type. There has been only one case of a radical transformation of the natural community, registered on the territory of the Lyubin Khutor nature monument (Novozybkovskii district, Bryansk oblast).

The results of classification of the nitrophite grass communities of the Sozh-Desna interfluve (Bryansk, Smolensk Regions of Russia and the adjacent regions of the Republic of Belarus), united in the class Epilobietea angustifolii Tx. et Preising ex von Rochow 1951 are given. Such vegetation within the European Russia is studied fragmentary, including the study area for which only some data on phytodiversity of this class were known (Bulokhov, Kharin, 2008; Semenishchenkov, Shapurko, 2009; Panasenko et al., 2014). Usually such communities are formed on crude fringes on watersheds and in floodplain forests, on wet and damp meadows in beams, river and stream valleys. As a rule, similar habitats in Europe are under various anthropogenic influence, therefore vegetation of this type is referred to categories of «semi-natural» or «ruderal» ones (Dengler et al., 2007; Mucina et al., 2016). For a long time fr om the standpoint of floristic classification nitrophite grass communities were assigned to the class Galio-Urticetea Passarge ex Kopecky 1969. The modern view (Mucina et al., 2016), this vegetation is integrated in the class Epilobietea angustifolii Tx. et Preising ex von Rochow 1951, representing tall-herb semi-natural perennial vegetation on disturbed forest edges, nutrient-rich riparian fringes and in forest clearings in the temperate and boreal zones of Eurasia. Thus, class Epilobietea angustifolii combines types of communities rather diverse on their ecology and successional status. However, we support this syntaxonomical decision, since combination of synanthropic, native and even often alien species is character for the majority of nitrophyte phytocoenoses. In the territory of the Sozh-Desna interfluve phytocoenoses of this class are partly formed with the participation of invasive species: Heracleum sosnowskyi, Echinocystis lobata, Impatiens glandulifera, Reynoutria japonica. Listed species are regarded as «transformers» due to their ability to intensely change the composition and structure of phytocoenoses, into which they are introduced. Usually such community are poor in species number, but for a long-term keep their stability in unchanging conditions. In our opinion, if invasive species forms a stable community for a long time, wh ere it defines phyto-enviroment and composition of coenofloras in localities with similar habitats, it can be considerd as character (for the associations and subassociations) or differential (for variants). This approach argues in favor of establishing units of association rank for vegetation with the invasive species, but not of non-rank units «derivative» communities. Monitoring of the nitrophyte grass communities in the Sozh-Desna interfluve for several years shows that their coenofloras and structure remained unchanged while occupied area became larger. Therefore, described phytocenoses formed by invasive species can be considered as stable, that allows us to combine them in the syntaxa of association and subassociation ranks. For the development of syntaxonomy of nitrophyte grass vegetation 165 authors’ relevés, including 62 made during the investigation of Sozh-Desna interfluve in 2016–2017, have been used. The classification has been performed according the J. Braun-Blanquet approach. The syntaxonomy includes 10 associations, 5 subassociations within 4 alliances. Nitrophite grass communities of the study region have some differences in species composition and habitat specificity that allows to put them into 3 orders within the class Epilobietea angustifolii: Convolvuletalia sepium Tx. ex Moor 1958 (semi-natural fringe vegetation on river and other water body banks in temperate Europe and the Mediterranean); Circaeo lutetianae–Stachyetalia sylvaticae Passarge 1967 nom. conserv. propos. (ruderal and semi-natural fringe mesic tall-herb vegetation on nutrient- and base-rich soils in cool-temperate and submediterranean Europe); Galio-Alliarietalia Oberd. in Gürs et T. Müller 1969 (ruderal vegetation dominated by short-lived perennials on mesic loamy soils in the low altitude cool-temperate Central Europe and at high altitudes of submediterranean Europe— some alliances of this order unite ruderal and semi-natural communities (Dengler et al., 2007; Mucina et al., 2016). 2 associations and 4 subassociations are described as new ones. Senecionetum fluviatilis rubetosum caesii subass. nov. hoc loco (Table 1, relevés 1–17; holotypus — relevé 2*: Bryansk Region, Vygonichi district, to the west from Poluzhye, riverbed right bank wloodplain of the Desna River, 7.08.2016, A.D. Bulokhov). Scirpo sylvatici–Galietum rivalis ass. nov. hoc loco, S. s.–G. r. typicum subass. nov hoc loco (Table 2; holotypus — relevé 16*: Bryansk Region, Bryansk, Bezhitsk district, near Staynoye settlement, 10.07.2016, A. D. Bulokhov). S. s.–G. r. echinocystie­tosum lobatae subass. nov. hoc loco (Table 2, relevés 1–7; holotypus — relevé 1*: Bryansk Region, Bryansk, near Svenskiy monastery, bottom of ravine, 10.07.2016, A. D. Bulokhov). S. s.–G. r. eupatorietosum cannabini subass. nov. hoc loco (Table 2, relevés 8–14; holotypus — relevé 10*: Bryansk Region, Mglinsk district, near Oskolkovo, floodplain of the Voylovka River, 17.08.2017, A. D. Bulokhov). Link of these syntaxa with river floodplains is reflected in their assignment to the alliance Senecionion fluviatilis, which combines high-grass border communities on rich soils of the river banks and beams in Central Europe (Mucina et al., 2016). Obviously, the distribution area of this unit may be expanded into the Central Europe. Chaerophylletum temuli ass. nov. hoc loco (Table 5, holotypus — relevé 2*: Bryansk region, Bryansk, Suponevo, near Svenskiy monastery, the lower part of the indigenous side of the Desna River valley, 14.08.2005, A. D. Bulokhov). Communities of this association are rare in the region and distributed in specific habitats in the lower parts of the indigenous slopes of river valleys and beams and nearby hollows, generally at the chalk outlets. The combination of typical nitrophilous species of the class with some weed and ruderal species makes possible the assignation of this association to alliance Geo urbani-Alliarion officinalis, which combines ruderal and semi-natural fringe thermophyte vegetation of short-lived low herbs on nutrient-rich soils of temperate Europe.

The distribution of Heracleum sosnowskyi in Bryansk oblast is assessed. Characteristic features of flowering and seed-based reproduction are considered, and a list of insects found on hogweed inflorescences is given. The mechanism of hogweed invasion into natural communities is addressed. Penetration into natural communities is related to anthropochorous dispersal and damage to the vegetative cover. High seed productivity, the formation of a large seed pool, the presence of dormant plants, and rapid development during the spring period enable the rapid dispersal of Heracleum sosnowskyi in the secondary range. Communities of the association Urtico dioicae–Heracleetum sosnowskyi Panasenko et al., 2014 are common in the region. Tree communities that include Heracleum sosnowskyi (Heracleum sosnowskyi–Salix fragilis, Heracleum sosnowskyi–Betula pendula) are scarce in Bryansk oblast.

In the article the data on 137Cs accumulation in meadow ecosystems plants of radioactive contaminated areas of Bryansk, Gomel and Chernigov regions are provided. The researches were conducted in 2013 within landscapes of Iput, Desna, Snov, Dnieper river valleys. It is proved that meadow plants of various species and ecological groups from communities of various syntaxons show different abilities to accumulate radionuclides. High 137Cs specific activity is noted for plants of genus Carex. Plants of ass. Festucetum arundinaceae are characterized by low intensity of 137Cs accumulation. Practical value of researches is connected with the necessity to solve the problem of pure forages production for needs of animal breeding. The comparative analysis of the radionuclide content in dry phytomass on each of investigated areas is made. It is found out that in Bryansk region radionuclide specific activity exceeds the control level of the radionuclide content in hay for the Russian Federation (600 Bq/kg). In Gomel region the hay made on floodplain meadows meets acceptable level of 137Cs in hay in Belarus (1300 Bq/kg). 137Cs pollution density of soils of investigated communities in Chernigov region of Ukraine is low, and the radionuclide content in dry phytomass does not exceed permissible levels.

The blacklist of Bryansk oblast flora including 100 adventive species is compiled. Plants from this blacklist are divided into four groups based on the classification recommended for keeping Black Books.

Examine the contents of the elements of the group of heavy metals in samples 18 meadow plant species and soil basal space. In soils root space is determined by significant fluctuations of total concentrations of heavy metals. Identified accumulative opportunities meadow species relative to the TM in natural meadows in the conditions of high technogenic load. Based on the coefficients of accumulation established types of «indicators» and «exclusive», which can be recommended as effective phytoremediation. For grassland species confirmed the species specificity of accumulative opportunities plants relative to the TM: Filipendula ulmaria, Scirpus sylvaticus (гигрофитные виды), Agrostis tenuis и Helichrysum arenarium. Hygrophytic species of floodplain meadows, xerophytic species in dry accumulate chemical elements the same, regardless of the geographical location of meadow ecosystems. For these plants is characterized by the accumulation of mobile essential elements strontium, copper, manganese.