Nitrophilous grassy communities of the class Epilobietea angustifolii Tx. et Preising ex von Rochow 1951 in the Sozh-Desna interfluve

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.