New associations and higher syntaxa of willow scrubs in the East European sector of the Arctic

Relevés of communities (94 in total) with shrub willows — Salix glauca, S. lanata, S. phylicifolia, and tree-like willows — S. viminalis, S. dasyclados were made in the Bolshezemelskaya tundra (11 sites, Fig. 1). Six new associations and one community type are described in 2 alliances — Polemonio acutiflorum–Salicion glaucae Lavrinenko et Lavrinenko 2021 and Galio borealis–Salicion viminalis all. nov. (Tables 1–4). The alliance Polemonio acutiflorum–Salicion glaucae unites herb and herb-moss willow scrubs (predominantly with Salix glauca, S. lanata) in lakeside depressions, runoff troughs, the slopes of hills on watersheds, slopes of bedrock terraces, above-floodplain terraces and occasionally flooded floodplains in river valleys. The range of this alliance is the plain tundra in the East European and Siberian sectors of the Arctic. Associations Polemonio acutiflorum–Salicetum lanatae Zanokha ex Lavrinenko et Lavrinenko 2021, Triseto sibirici–Salicetum glaucae Lavrinenko et Lavrinenko 2021 and Climacio dendroidis–Salicetum lanatae Lavrinenko et Lavrinenko 2021 were earlier described on Taymyr Peninsula, Kolguev and Vaygach Islands (Lavrinenko, Lavrinenko, 2021). New associations Chamaepericlymeno suecici–Salicetum glaucae, Geo rivalis–Salicetum glaucae, Hylocomio splendentis–Salicetum glaucae are described in the Bolshezemelskaya tundra (Table 1). Some communities of the associations Dicrano majoris–Salicetum lanatae Khitun in Telyatnikov et al. 2021 and Calliergono cordifolii–Salicetum lanatae Khitun in Telyatnikov et al. 2021, described on the Tazovskiy and Gydanskiy Peninsulas (Telyatnikov et al., 2021a and b) can be attributed to this alliance. However, the decisions for both these associations need to be revision (see Table 5). The characteristic species of the alliance Polemonio acutiflorum–Salicion glaucae were confirmed and clarifed. The phi-coefficient values for them are in the range 84.7–42.3 (Table 6). A new order of the same name is proposed for the willow scrubs of this alliance. Order Polemonio acutiflorum–Salicetalia glaucae ord. nov. Herb and herb-moss willow scrubs with Salix glauca and S. lanata in the plain tundra in the East European and Siberian sectors of the Arctic. Nomenclature type (holotypus): alliance Polemonio acutiflorum–Salicion glaucae Lavrinenko et Lavrinenko 2021 (Lavrinenko, Lavrinenko, 2021: 99). Differentiating species combination: Salix glauca, S. lanata; Bistorta vivipara, Petasites frigidus, Poa arctica, Polemonium acutiflorum, Ranunculus propinquus, Rubus chamaemorus, Valeriana capitata; Hylocomium splendens. Constant taxa: Achillea millefolium, Cardamine pratensis subsp. angustifolia, Chrysosplenium alternifolium subsp. sibiricum, Equisetum arvense s. l., Poa pratensis s. l., Rubus arcticus, Veratrum lobelianum, Viola biflora; Bryum pseudotriquetrum, Rhizomnium pseudopunctatum, Sanionia uncinata. Habitats. Intrazonal biotopes on watersheds (lakeside depressions, runoff troughs, hillsides), slopes of high river terraces, above-floodplain terraces and rarely flooded parts of floodplains in river and stream valleys. Willow scrubs from tree-like (Salix dasyclados, S. viminalis) and shrub (Salix lanata, S. phylicifolia) species, occupying the near-channel part of the floodplains of large and small rivers, channels and oxbows and experiencing regular flooding, are described in the southern tundra, northern forest-tundra and in the Pechora River delta. For such willow scrubs we have described a new alliance Galio borealis–Salicion viminalis in order Salicetalia purpureae Moor 1958 and class Salicetea purpureae Moor 1958. Alliance Galio borealis–Salicion viminalis all. nov. Tall grass-herb willow scrubs (Salix dasyclados, S. lanata, S. phylicifolia, S. viminalis) in riparian habitats in the southern tundra, forest-tundra and northern taiga in the European North of Russia. Nomenclature type (holotypus): ass. Senecioni nemorensis–Saliсetum viminalis ass. nov. (Table 2, rel. 19–25; Table 4, syntaxon 19). Characteristic species: Salix viminalis and Veronica longifolia (the same species of class Salicetea purpureae and order Salicetalia purpureae), Aconitum septentrionale, Adoxa moschatellina, Calamagrostis purpurea s. l., Filipendula ulmaria, Galium boreale, Lamium album, Myosotis palustris, Ranunculus repens and Vicia cracca (phi-coefficient varies from 77.7 to 47.6) (Table 6). Apparently, Salix dasyclados, with which one syntaxon has been described, can also be attributed to these. Constant species: Equisetum arvense s. l. (often dominant or codominant), Poa pratensis s. l., Veratrum lobelianum, Viola biflora. Habitats. Near the riverbed and central parts of the floodplain of large and small rivers, alluvial soils under conditions of regular flooding. Those willow scrubs are classified as 3 new associations and one community type: Vicio sepium–Salicetum lanatae, Senecioni nemorensis–Saliсetum viminalis, Bromopsio inermis–Salicetum viminalis, Calamagrostis purpurea–Salix dasyclados (Table 2). Floristically close communities are described in the floodplain of the Pechora River in the northern taiga (Shushpannikova, 1996), so we expanded the Galio borealis–Salicion viminalis range to this subzone. Further south the alliance Salicion triandrae T. Müller et Görs 1958 from the same order and class is widespread. Communities of Salicion triandrae occupy riparian habitats in the middle and southern taiga subzones (Taran, 1999; Vasilevich, 2009) and in the nemoral zone of Europe (Neuhäuslová et al., 2013; Mucina et al., 2016). The results of DCA-ordination confirm the correctness of the alliances Polemonio acutiflorum–Salicion glaucae and Galio borealis–Salicion viminalis establishment (Fig. 14). Ass. Carici stantis–Salicetum phylicifoliae ass. nov. (Table 3) unites willow scrubs (Salix glauca, S. lanata и S. phylicifolia) swamp-herb (Comarum palustre, Epilobium palustre, Equisetum fluviatile, Eriophorum angustifolium, Menyanthes trifoliata)–sedge (Carex aquatilis subsp. stans). If focusing on the composition of the lower layers, the place of association will undoubtedly be in the class Scheuchzerio palustris–Caricetea nigrae Tx. 1937, since most of the listed species are characteristic for it or for the order Caricetalia nigrae Koch 1926. However, the presence of rather tall and highly closed shrub layer, which determines the structure and physiognomy of communities, calls into question their attribution to mire. For the time being, we leave such communities outside the higher units. Differences in the floristic composition of the syntaxa in the East European tundras, in the mountainous Fennoscandia (Salicion phylicifoliae Dierssen 1992) and Chukotka (Aulacomnio turgidi–Salicion glaucae Sinelnikova 2001 (2009) and Saussureo oxyodontae–Salicion Sekretareva 2001 all. prov.) are significant (Table 4), which is clearly demonstrated be the results of cluster analysis (Fig. 15). Syntaxa of another northern alliance — Geranio albiflorum–Salicion Sekretareva 2011, described in Polar Ural, are joined in one cluster with the willow scrubs of the alliance Galio borealis–Salicion viminalis (Fig. 15). We have not assigned to any class the new order Polemonio acutiflorum–Salicetalia glaucae ord. nov., as opposed to Salicetalia glauco-lanatae Bœuf et al. ex Mucina et Daniёls in Mucina et al. 2016 (subarctic and boreal herbrich willow scrubs and birch krummholz of the Holarctic), placed in the class Betulo carpaticae–Alnetea viridis Rejmánek ex Bœuf, Theurillat, Willner, Mucina et Simler in Bœuf et al. 2014 (subalpine and subarctic herb-rich alder and willow scrubs and krummholz of the Alps, the Carpathians, the Balkans, the Caucasus, Northern Europe and Greenland). We believe that for the willow scrubs of the tundra zone a revision of all the accumulated data and description of a new class are required.