The vegetation of the class Scheuchzerio–Caricetea fuscae Tx. 1937 in the Yanganape mountain massif area (Eastern macroslope of the Polar Urals)

There are very few publications on the classification of mountain mire vegetation in Russia. Several associations in the Southern Siberia mountains (Lapshina, 1996; Lashchinsky, 2009) and the Khibiny Mountains (Koroleva, 2001) are described. Mire vegetation in the Southern Urals is relatively well studied and described in the traditions of the ecological-phytocenotic dominant classification (Ivchenko, 2013; Ivchenko, Znamenskiy, 2015) while the knowledge on that of the Northern and Sub-Polar Urals is extremely limited. There is no information about the mires in the Polar Urals. The paper presents the results of classification of the class Scheuchzerio–Caricetea fuscae of the Yanganape mountain massif (67.68°—67.75° N, 67.72°—68.00° E) and adjacent plains in the Eastern macroslope of the Polar Urals, within the southern tundra subzone. The study area is mountain massif of about 250 m a. s. l., composed of limestone outcrops, with a wavy flat (60–90 m a. s. l.) plain around (Fig. 1–2). The classification is based on 138 relevés made in July 27–August 8, 2017 (Fig. 3). Relevés of similar syntaxa, established in the north of the Western Europe and the East European tundras (Ruuhijärvi, 1960; Dierssen, 1982; Lavrinenko et al., 2016), were included in analysis. DCA and t-SNE (t-distributed stochastic neighbor embedding) methods were used for ordination of syntaxa in multidimensional space (Maaten, Hinton, 2008). The calculations were made using the machine learning package for Python-Scikit-learn. In total, 13 associations, 11 subassociations, 12 variants from 6 alliances and 3 orders of the class Scheuchzerio–Caricetea fuscae were identified on the relatively small (about 70 km2) area. Within the order Caricion davallianae, syntaxa of the alliance Caricion atrofuscae-saxatilis, comprising low sedge-hypnum communities on carbonate mineral and organomineral soils in the mountains of the Western Europe, were identified and described for the first time on the territory of Russia. Three new associations (Ditricho flexicauli—Caricetum redowskianae, Tomentypno nitentis–Equisetetum palustre, Tomentypno nitentis–Eriophoretum vaginati) were described on the the Yanganape mountain massif (Table 1), which significantly expands the area of the alliance to the East. Alliance’ communities have some similarities with syntaxa of zonal dwarf shrub-grass-moss tundra vegetation (Lavrinenko, Lavrinenko, 2018), but are generally well differed by the species composition and community structure (Table 5). The order Caricetalia fuscae in the Eastern macroslope of the Polar Urals is represented by 4 alliances. In addition to Drepanocladion exannulati and Sphagno-Caricion canescentis, listed in the “Classification of Vegetation of Europe” (Mucina et al., 2016), we include into order the alliance Caricion stantis — moderately rich sedge-moss fen vegetation of the Subarctic and tundra zones, and the alliance Stygio–Caricion limosae, containing extremely waterlogged meso-oligotrophic and slightly acidic to neutral low sedge fens. There are 4 associations within the alliance Caricion stantis, including new ass. Scorpidio cossonii–Caricetum rariflorae (Table 2). Taking into account statistically significant differences in the species composition of sedge-moss communities dominated by various moss species (Fig. 15, 5-6), ass. Scorpidio scorpioidis–Caricetum chordorrhizae was taken out from ass. Drepanoclado revolventis–Caricetum chordorrhizae Osvald 1925 ex Dierssen 1982 broadly understood in the Western Europe. Its nomenclature type is the only relevé of Carex chordorrhizae-Amblistegium scorpioides-Ass. (Osvald 1925: 37), which sufficient for the original diagnosis, because it contains list of species with abundance and both name-giving taxa (ICPN, 2b, 7). The communities of both associations were identified in the Eastern macroslope of the Polar Urals, where they are represented by new subassociations, which significantly expands the distribution area of these associations to the East. Recently validly described in the Eastern European tundras (Lavrinenko et al., 1916) ass. Scorpidio revolventis–Caricetum rariflorae is also known for the North of the Western Europe (Dierssen, 1982). Its difference from western syntaxa is the absence of many boreal species, which are not able to exist in the severe climate in the North of Western Siberia, as well as the great number of plant communities with the diagnostic species of the alliance Caricion atrofuscae-saxatilis due to rich mineral nutrition, associated with the carbonate soils and calcium-rich groundwaters in the study area. New associations are established in two allian­ces: Carici aquatilis–Warnstorfietum tundrae in Drepanocladion exannulati and Sphagno squarrosi–Caricetum chordorrhizae in Sphagno–Caricion canescentis (Table 3). The floristic features of the latter alliance, whose communities on the northern limit of their distribution have a certain similarity to the arctic sedge-moss mire vegetation of the alliance Caricion stantis, are discussed. Oligotrophic communities of the alliance Scheuch­zerion palustris, occuring in acidic habitats, are placed in the order Scheuchzerietalia palustris that is in agreement with new interpretation of this alliance in the paper by Mucina et al. (2016). Two associations (Carici rotundatae–Sphagnetum baltici, Sphagno compaci–Caricetum rotundatae) are assigned to this alliance. There are few relevés for both Scheuchzerion palustris and Stygio–Caricion limosae alliances in the study area that is why their classification is preliminary, and it will be considered in the near future for the whole North of the Western Siberia on a larger data set. The classification results are confirmed by DCA-ordination of selected syntaxa (Fig.15, Б). However, the differentiation of communities is more clearly demonstrated by the t-SNE method, which allows displaying multidimensional hyperspaces on the plane (Fig.15, А).