The survey of the psammophylous grass vegetation syntaxa in the Southern Nechernozemye of Russia

The article provides a survey of grass psammophylous vegetation syntaxa in the Southern Nechernozemye of Russia and validation of syntaxa in accordance with the requirements of the International Code of Phytosociological Nomenclature (Theurillat et al., 2021); questions of syntaxonomy and diagnosis of units of different levels of the syntaxonomical hierarchy are discussed. The data for the analysis was the base obtained in 2018–2021, including 312 relevés of psammophylous grass vegetation in the Southern Nechernozemye of Russia (Bryansk, Kaluga, south-west of Moscow, north-west of Oryol, Smolensk Regions). Most of the relevés were made on the watershed of two large river systems: the Dnieper (the Sozh river basin) and the Volga (the Oka river basin) while some ones are in the northwestern part of the Smolensk region (Demidovsky district, Smolenskoye Poozerye National Park), which belongs to the Zapadnaya Dvina basin. Natural psammophytic habitats in this region are widespread on outwash plains, sandy river terraces dominated by pine forests of the alliance Dicrano–Pinion sylvestris (Libb. 1933) W. Mat. 1962 nom. conserv. propos. Open sands are formed in the place of such forests after clear felling of pine with the destruction of the living land cover. In addition, psammophylous grass vegetation forms on non-flooded or short-flooded sandy ridges in river floodplains, on plowed sands that were opened during construction, along sand pits, on clearings under power lines, along old abandoned roads on sand embankments and sandy roads fallow lands and pastures with sandy and sandy loam soils (Kupreev et al., 2020). The psammophylous grass vegetation of the studied region is represented by 12 associations comprising 4 alliances and 2 orders of the class Koelerio–Corynephoretea canescentis Klika in Klika et Novák 1941, which unites dry grasslands on sandy soils and on rocky outcrops of the temperate to boreal zones of Europe, the North Atlantic islands and Greenland (Mucina et al., 2016). On the basis of comparative analysis for alliances and orders we compiled regional combinations of diagnostic species with constancy in coenoflora above 20 % and values of the statistical φ-coefficient above 20 (at p <0.01): Armerion elongatae (Armeria maritima, Astragalus arenarius, Dianthus fisheri, Jovibarba globifera, Jurinea cyanoides, Koeleria glauca), Corynephorion canesentis (Corynephorus canescens), Hyperico perforati–Scleranthion perennis (Berteroa incana, Festuca ovina, Helichrysum arenarium, Hypericum perforatum, Jasione montana, Pilosella officinarum, Rumex acetosella, Scleranthus perennis, Trifolium arvense). The following species diagnose the orders of psammophylous vegetation: Corynephoretalia canescentis (Chamaecytisus ruthenicus, Cladonia arbuscula, Corynephorus canescens, Jurinea cyanoides, Koeleria glauca, Sedum acre) and Trifolio arvensis–Festucetalia ovinae (Abietinella abietina, Elytrigia repens, Hieracium umbellatum, Jasione montana, Festuca ovina, F. rubra, Galium mollugo, Pilosella officinarum, Plantago lanceolata, Poa angustifolia, Trifolium arvense, Viola tricolor). Diagnostic combinations of alliances partly duplicate those of orders, and some species are the diagnostic for two alliances, which does not contradict the logic of syntaxonomy. Analysis of the comparative table showed that all syntaxa of psammophylous vegetation taken for analysis can be fully assigned to the class Koelerio–Corynephoretea canescentis in accordance with its current diagnosis (Mucina et al., 2016). According to the ratio of the diagnostic species of the classes Koelerio–Corynephoretea canescentis and Sedo-Scleranthetea, it is not possible to divide syntaxa into two groups. In general, in the Southern Nechernozemye of Russia, typical natural habitats characteristic of the Central European communities of the class Sedo-Scleranthetea are virtually absent. They are imitated by anthropogenic ecotopes with washed out or trampled, usually heavily disturbed, rubble substrates. Probably, it is possible to classify some types of grass communities that form here on the slopes of railways and roads, on overgrown stony dumps, strongly compacted as a result of trampling or the passage of vehicles, to the class Sedo-Scleranthetea. However, the assigning of these communities to this class is debatable. A significant part of the studied phytocoenoses was assigned to 7 non-rank units — «communities» within the class Koelerio–Corynephoretea canescentis. These are, firstly, pioneer and, as a rule, sparse or floristically incomplete psammophylous communities at the initial stages of succession with the participation of widespread grass psammophilic oligotrophs. Secondly, these are monodominant phytocoenoses formed after anthropogenic disturbance of psammophylous vegetation, for example, on fallow lands and clearings in pine forests on sandy and sandy loam soils; after fires, trampling. The names of these syntaxa are given according to the dominant plant species.