Class Salicetea herbaceae Br.-Bl. 1948 in Altai-Sayan mountain region

The class Salicetea herbaceae Br.-Bl. 1948 includes arctic and alpine-subnival snow-bed communities of Eurasia and the Arctic Ocean islands (Mucina et al., 2016). The coenoflora of these communities is formed by psychrophilous and chionophilous mesophytic species. R. V. Kamelin (2005) who named these as alpine grass carpets (Kryonanocoryphion eurasiaticum), noted that this type of vegetation is characteristic of the Altai-Sayan mountain region, where alpine carpets are the highest floristic diversity in Asia. The snow-bed communities occupy macro- and megachionic ecotops (Kholod, 1993) in sites with excessive accumulation of snow in winter, which is preserved in the summer in the form of snow-beds. Usually snow-bed communities cover patches from several tens to several hundred square meters. The habitats of these communities are characterized by: 1) short ve­getation period due to the long period of the thick snow cover (up to 5 m) melting; 2) cold moistening during the most part of growing season because the melting of snow, and the inflow of water from nearby or underground springs; 3) no genesis of bog soils (Sedelnikov, 2017). Earlier syntaxa of the class Salicetea herbaceae were considered as a part of the alliance Salicion tur­czaninowii Ishbirdin in Ishbirdin et al. 1996, the order Salicetalia herbaceae Br.-Bl. in Br.-Bl. et Jenny 1926. 105 relevés were sampled in 1998–2015 (Fig. 1), also we used 28 relevés published earlier (Chytrý, et al., 1995; Danihelka, Chytrý, 1995; Korolyuk, 2001; Telyatnikov et Mamakhatova, 2011; Ermakov, Zibzeev, 2012; Telyatnikov, 2013). An analysis of the coenoflora of the alpine-subnival snow-bed communities revealed the dominance of high-altitude species with a South Siberian and ­Central Asian areal (Aquilegia glandulosa, Carex altaica, Dracocephalum grandiflorum, Festuca kryloviana, Gentiana grandiflora, Hedysarum austrosibiricum, Luzula sibirica, Solidago dahurica, Tripleurospermum ambiguum, Veronica densiflora, Viola altaica). High constancy and often domination by shrubs of the genus Salix (Salix berberifolia, S. rectijulis и S. turczaninowii) are common for these communities. The originality of species composition of the chionophilic meadows of the North Mongolia and East Kazakhstan allowed to suggest the new order Sibbaldio procumbentis–Ranunculetalia altaici ord. nov. hoc loco and two alliances: Ranunculion altaici all. nov. hoc loco and Salicion turczaninowii Ishbirdin in Ishbirdin et al. 1996. The snow-bed communities are included in five associations (three ones are new), two subassociations, and two variants. The order Sibbaldio procumbentis–Ranunculetalia altaici ord. nov. hoc loco (Table 2) includes the snow-bed communities of South Siberia, North Mongolia and East of Kazakhstan. They occupy the lower part of the mountain-tundra belt in habitats with thick snow cover in winter which does not completely melt in summer. The asian-alpine species dominate in the coenoflora of these meadows. Diagnostic species: Anthoxanthum alpinum, Aquilegia glandulosa, Gentiana grandiflora, Lescuraea saxicola, Luzula sibirica, Salix rectijulis, Schulzia crinita, Veronica alpina, V. densiflora, Viola altaica. There are two meadow types: on snow-beds with constant cold wetting, and close of snow-beds or in places with high snow cover depth and variable wetting. We propose to put the first group into the alliance Ranunculion altaici all. nov. hoc loco, the second one in Salicion turczaninowii Ishbirdin in Ishbirdin et al. 1996. The alliance Ranunculion altaici includes nival meadows dominated by Ranunculus altaicus and R. sulphureus (Table 2). It is widespread in the mountains of South Siberia, North Mongolia, and East Kazakhstan. At present, the alliance includes one ass. Polytricho sexangularis–Ranunculetum altaici (Fig. 4). They occupy site of snow-beds with constant high cold moisture during the whole vegetation period. Alliance Salicion turczaninowii Ishbirdin in Ishbirdin et al. 1996, based on the analysis of ass. Salici turczaninowii–Sibbaldietum procumbentis Danihelka et Chytrý 1995 from Barguzin Range (Danihelka, Chytrý, 1995), encompasses chionophilous communities of the South Siberian mountains (Ishbirdin et al., 1996). The diagnostic species are widespread in the Altai-Sayan mountain region and Transbaikalia: Carex aterrima, Ranunculus altaicus, Salix turczaninowii,and Viola altaica. The alliance includes 3 new associations (Bistorto viviparae–Salicetum turczaninowii, Doronico altaici–Sibbaldietum procumbentis, Vaccinio myrtilli–Sibbaldietum procumbentis). Ass. Bistorto viviparae–Salicetum turczanino­wii ass. nov. hoc loco (Table 2; Table 3, N 1–5, holotypus — N 5) — snow-bed communities with Salix turczaninowii and Sibbaldia procumbens dominance. Its area encompasses the humid part of Altai-Sayan mountain region. Diagnostic species: Antennaria dioica, Bistorta vivipara, Carex tristis, Festuca kryloviana, Hedysarum austrosibiricum, Minuartia biflora, Saxifraga sibirica. Communities occur on leveled or convex parts of the slopes, small terraces at the altitudes from 2230 to 2500 m. Rocks and rubbles cover up to 30 % of the surface. Асс. Doronico altaici–Sibbaldietum procumbentis ass. nov. hoc loco (Table 2; Table 3, N 6–16, holotypus — N 12, Fig. 5) includes snow-bed communities with alpine (Anemonastrum narcissiflorum, Aquilegia glandulosa, Callianthemum sajanense, Doronicum altaicum, Dracocephalum grandiflorum, Swertia obtusa, Tripleurospermum ambiguum, Veronica densiflora) and subalpine (Geranium albiflorum, Trollius asiaticus) species. These species are common in the class Mulgedio-Aconitetea Hadač et Klika in Klika et Hadač 1944. Diagnostic species: Bergenia crassifolia, Callianthemum sajanense, Doronicum altaicum, Dracocephalum grandiflorum, Geranium albiflorum, Tripleurospermum ambiguum, Trollius asiaticus, Veronica densiflora. Асс. Vaccinio myrtilli–Sibbaldietum procumbentis ass. nov. hoc loco (Table 2; Table 4, N 1–41, holotypus — N 5; Fig. 6) includes snow-bed communities dominated by Sibbaldia procumbens and Vaccinium myrtillus. We met these communities in the upper part of subalpine and the lower part of alpine belt in the West and East Sayans, Kuznetsk Alatau, West and Central Altai. The diagnostic group of species is represented by Omalotheca norvegica, Polytrichastrum sexangulare, Sibbaldia procumbens, Solidago dahurica, Vaccinium myrtillus. We proposed 2 subassociations within this syntaxon: V. m.–S. p. typicum (Table 2; Table 4, N 1–15, 31–41, holotypus — N 5) and V. m.–S. p. diphasiastretosum alpini (Table 2; Table 4, N 16–30, holotypus — N 24). The ass. Swertio obtusae–Caricetum tristis Telyatnikov et Mamakhatova 2011 was described in the South-East Altai (Telyatnikov, Mamakhatova, 2011). It includes grass-sedge-forb and willow-lichen-forb alpine meadows dominated by Gentiana algida, Bistorta vivipara, B. major, Carex tristis, Swertia obtusa, Lagotis integrifolia. Ass. Swertio obtusae–Caricetum tristis differs in species richness and floristic composition from other alliance associations. The cluster analysis (Fig. 3) verified this fact: there are 2 specific groups, corresponding to 2 classes. The core of coenoflora of the class Salicetea herbaceae are species of nival and hemichionophilous habitats (Aquilegia glandulosa, Carex altaica, Carex aterrima, Diphasiastrum alpinum, Gentiana grandiflora, Kiaeria starkei, Lescuraea saxicola, Omalotheca norvegica, Salix turczaninowii, Sibbaldia procumbens, Ranunculus altaicus, Veronica densiflora, Viola ­altaica). Arctic-alpine tundra species of the Сarici rupestris–Kobresietea bellardii Ohba 1974 class(Comastoma tenellum, Gentiana algida, Kobresia myosuroides, Potentilla nivea, etc.) as well as its common species (Erigeron eriocalyx, Eritrichium villosum, Festuca sphagnicola, Gastrolychnis apetala, Leontopodium ochroleucum, Potentilla gelida, Thalictrum alpinum) forms communities of the ass. Swertio obtusae–Caricetum tristis. That is why it should not be attributed to the class Salicetea herbaceae. The analysis of nival meadow coenofloras (Fig. 3a) showed the codominance of the North Asian (30 %), Holarctic (22 %) and South Siberian (22 %) species groups. Alpine (36 %) and arcto-alpine (20 %) belt-zonal ones (Fig. 3б) dominate in coenoflora of chionophilous meadows. Three floristic complexes proved to form the base of the coenoflora of nival meadows: arctic-alpine types of Holarctic distribution; alpine species both from the North Asian ranges and South Siberia, North Mongolia and East Kazakhstan (Sedelnikov, 2017).