The syntaxonomy of the grasslands and meadows in mountain tundra of Murmansk Region

Grasslandsandmeadowsoccur on seasonally moist and fresh soils, nearsnowfields, temporaryand permanent streams, springs and brooks, in the low and middle mountain ranges in Murmansk Region (Fig. 1). They occupy relatively small areas, but support high diversity of species and represent “lieblichsten Erscheinungen“, as R. Nordhagen (1928: 353) wrote. Syntaxonomy of this vegetation is still not clear and far from unambiguous explanation. From literature, these communities in Fennoscandiаn mountain tundra are related to several classes: Juncetea trifidi, Saliceteaherbaceae, Thlaspietea rotundifolii and Molinio-Arrhenatheretea, which differ greatly both to habitats and vegetation. In Russian phytocoenology, some researchers include tundra grasslands with dominance of Nardus stricta and Avenella flexuosa in general typology (Ramenskaya, 1958), along with floodplain and dry grasslands and meadows, but other consider such vegetation in mountain tundra as independent type, related to grasslands and meadows in alpine belt (Gorodkov, 1938; Aleksandrova, 1977).

Classification of mountain tundra grasslands and meadows in Murmansk Region based on 103 field descriptions and published relevés, with Braun-Blanquet approach applied. Prodromus of syntaxa is provided. Six vegetation associations were related to 4 alliances and 2 classes, three associations were described as new (Table 1).

Ass. Carici bigelowii–Nardetum strictae (Zlatník 1928) Jeník 1961 (Table 2), withdiagnostic species Diphasiastrum alpinum and Nardus stricta, includes early snow-bed, poor of species vegetation with dominance of matgrass N. stricta.

Аss. Anthoxantho alpini–Deschampsietum flexuosae Nordh. 1943 (Table 3; Fig. 2), with diagnostic species Anthoxanthum alpinum, Avenella flexuosa, includes early snow-bed grasslands, with dominance of Carex bigelowii, Avenella flexuosa, Anthoxanthum alpinum, and presence of diagnostic species of alliance Phyllodoco–Vaccinion myrtilli (Phyllodoce caerulea, Vaccinium myrtillus).

Ass. Salici herbaceae–Caricetum bigelowii Koroleva et Kopeina ass. nov. hoc loco (Table 4, holotypus — relevé 8 (84/93)), with diagnostic species Alchemilla alpina, Cardaminebellidifolia, Carex bigelowii (dominant), Diplophyllum taxifolium, Lophozia wenzelii, represents rich of species early snow-bed, with dwarf-shrub- and-grass and moss layers.

Ass. Hieracio alpini–Caricetum bigelowii Koroleva et Kopeina ass. nov. hoc loco (Table 5, holotypus — relevé 10 (46/01)), with diagnostic species Antennaria dioica, Carex bigelowii (dominant), Hieracium alpinum,includes communities rich of grasses and herbs on south-exposed gentle slopes, near springs and brooks.

Аss. Potentillo crantzii–Polygonetum vivipari Nordh. 1928 (Nordhagen, 1928: 356–357: «Potentilla crantzii–Polygonum viviparum Ass.»; Kalliola, 1939: 132–135: «Polygonum viviparum–Thalictrum alpinum-Soz.». Table 6, lectotypus hoc loco — relevé 16), diagnostic species Carex atrata, Cerastium alpinum, Erigeron uniflorus, Festuca vivipara, Polytrichastrum alpinum, Potentilla crantzii, Rhodiola rosea, Saussurea alpina, Thalictrum alpinum, Viola biflora.The association is the holotype of the alliance Potentillo–Polygonion vivipari Nordh. 1937 and includes rich of species low-herb meadows in mountain tundra. Association includes three variants: Oxyria digyna (Table 6, № 1–10; Nordhagen, 1928: 356–357, Table, Bestanden I, II), typica (Table 6, № 11–20; Nordhagen, 1928: 356–357, Table, Bestanden III, IV) and Agrostis borealis (Table 6, № 21–29; Kalliola, 1939: 132–135, Table 19, № 3–11).

Ass. Salici reticulatae–Trollietum europaei Koroleva et Kopeina ass. nov. hoc loco (Table 7, holotypus — relevé 10 ( m1/16); Fig. 3) with diagnostic species Geranium sylvaticum, Juncus trifidus, Nardus stricta, Salix reticulata,represents species-rich meadows near springs and on gentle slopes, sometimes with patches of low willows and dwarf birch. The association is transitional to the tall-herb shrubs and forests of alliance Mulgedion alpini, class Mulgedio-Aconitetea.

To arrange the syntaxa described in Murmansk Region in higher units correctly, we used the first descriptions of following alliances in Fennoscandia: alliance Potentillo–Polygonion vivipari, incl. Potentilla crantzii–Polygonum viviparum Ass. (Nordhagen, 1928: 356–357, Table, Bestanden I–IV) and Polygonum vivparum–Thalictrum alpinum-Soz. (Kalliola, 1939: 132–133, Table 19, № 3–11); alliance Ranunculo–Poion alpinae, incl. Trollius europaeus-soc. (Gjaerevoll, 1950: 420–421, Table XIII, № 1–10); alliance Deschampsio-Anthoxanthion, incl. ass. Deschampsietum flexuosae and ass. Caricetum bigelowii (ibid.: 393–394, Table I, Stands I–V; 396–397, Table II, Stands I, II); alliance Saxifrago stellaris–Oxyrion digynae, incl. ass. Oxyrietum digynae (ibid.: 406–407, Table VI, Stands I–III); alliance Kobresio-Dryadion, incl. Carex rupestris–Encalypta rhabdocarpa sos. (Nordhagen, 1943: 576–577, Table 99, Serie I–III) and аss. Dryadetum octopetalae (Nordhagen, 1955: 76–81, Table III, no. 17–33), as well as descriptions of ass. Polygono vivpari–Thalictretum alpini (Kalliola 1939) Koroleva 2006 from the Barents Sea shore. In total 113 relevés were analyzed with use of Program ExStatR (Novakovskiy, 2016) based on the Non-metric Multidimensional Scaling (NMS), and hierarchical clustering with grouping by arithmetic means UPGMA. In both methods, the Sjørensen-Chekanovsky coefficient was used as a measure of similarity/distance.

All relevés represent rather distinctive groups in ordination space (Fig. 4), with few transitional ones. Two well-expressed gradients explain the variation in grasslands and meadows: (1) snow-depth and calcium-availability and (2) height above the sea level, together with steepness of the slope and coarseness of substrata.

On the one end of the axis 2 there are communities of the ass. Carici bigelowii–Nardetum strictae (Table 2; Fig. 4, group 3) with diagnostic species Nardus stricta and Diphasiastrum alpinum. They represent closed and species-poor (39 species in syntaxon, 11 species per relevé in average) mono-dominant vegetation in snow-bed depressions, which are water-inundated in the beginning of the growing season, but dry up quickly. Rather compact group of communities of Kobresio-Dryadion (Fig. 4, groups 14 and 15), described by Nordhagen in Ca-rich habitats in Scandinavian mountains, with constant species Dryas octopetala, Saxifraga oppositifolia, Carexrupestris, Alectoria nigricans, A. ochroleuca, Flavocetraria cucullata and F. nivalis occupies an opposite end.

Second gradient (axis 1) starts with meadows associated with the moderate snow and moisture conditions in zonal tundra in Murmansk Region (Fig. 4, group 4: Polygono vivpari–Thalictretum alpini; Koroleva, 2006). It finishes with relevés of Gjaerevoll’s (1950) ass. Oxyrietumdigynae (all. Saxifrago stellaris–Oxyrion digynae), which occurs on stony and moist substrata on steep slopes of high Scandinavian ranges (Fig. 4, group 13). Among constant species there are mosses and liverworts Andreaea rupestris, Anthelia juratzkana, Hymenoloma crispulum,hygro-, and mesophytic herbs Epilobium anagallidifolium and Saxifraga stellaris. In close position on the ordination diagram are early snow-beds in Murmansk Region, ass. Salici herbaceae–Caricetum bigelowii, with diagnostic species Alchemilla alpina, Carex bigelowii, Cardaminebellidifolia, Diplophyllum taxifolium, Lophozia wenzelii (Table 4; Fig. 4, group 1). Ass. Anthoxantho alpini–Deschampsietum flexuosae with diagnostic species Anthoxanthum alpinum, Avenella flexuosa (Table 3; Fig. 4, group 2) comprises vegetation in transitional habitats from late snow-beds to moss-blueberry tundra and has large portion of dwarf shrubs of Phyllodoco–Vaccinion myrtilli. On the ordination diagram, these communities differ from Gjaerevoll’s (1950) relevés of Deschampsio-Anthoxanthion (Fig. 4, group 12); they are ecologically similar with snow-bed communities.

Central parts of the both gradients are occupied by the meadows of following associations: Hieracio alpini–Caricetum bigelowii (Table 5; Fig. 4, group 8), Potentillo crantzii–Polygonetum vivipari (Fig. 4, group 6) and Salici reticulatae–Trollietum europaei (Table 7; Fig. 4, group 7). All of them belong to alliance Potentillo–Polygonion vivipari (diagnostic species: Anthoxanthum alpinum, Bartsia alpina, Bistorta vivipara, Distichium capillaceum, Luzula spicata, Poa alpina, Potentilla crantzii, Ranunculus acris, Salix reticulata, Sanionia uncinata, Saussurea alpina, Selaginella selaginoides, Silene acaulis, Taraxacum croceum, Trollius europaeus, Veronica alpina, Viola biflora). They represent the richest tundra meadows (to 134 species in association and 41 species in community), with dominance of mesophytic herbs, high number of dwarf-shrubs, presence of mosses and liverworts. The alliance is well presented on the cluster dendrogram (Fig. 5).

The first reference to alliance Potentillo–Polygonion vivipari was published by Nordhagen (1937: 37–43) and contained synoptical table and direct reference to Potentilla crantzii–Polygonum viviparum Ass. (Nordhagen, 1928: 356–357) as the most characteristic type of the alliance. So the alliance could be considered effectively and validly published (ICPN: Art. 1, 2b). Since Potentilla crantzii–Polygonum viviparum Ass. represents the only element published with the valid name with direct reference in the original diagnosis of the alliance, it must therefore be accepted as the holotype (ICPN: Art. 18a), and the name should be corrected to Potentillo crantzii–Polygonetum vivipari Nordh. 1928 (ICPN: Art. 41b).

Later on, R. Kalliola (1939) and N. Koroleva (2006) also published one syntaxon in this alliance: publication of holotype by Koroleva (2006) is superfluous, because original diagnoses of Nordhagen (1937) is accompanied by clear reference to type association in the paper by Nordhagen (1928) (ICPN: Art. 21).

The original diagnosis of Gjaerevoll’s (1950) alliance Ranunculo–Poion alpinae, ass. Ranunculo acris–Poetum alpinae Daniёls 2016 (based on Trollius europaeus-soc., Gjaerevoll, 1950: 420–421, Table XIII) (Fig. 4, groups 9, 10) coincides with the original diagnosis of Nordhagen’s alliance (Table 1), so Nordhagen’s name would have the priority over the Ranunculo–Poion alpinae which is a syntaxonomic synonym (ICPN: Art. 29с).

T. Ohba (1974) considered Potentillo–Polygonion vivipari as synonym of Kobresio-Dryadion (Fig. 4, groups 14 and 15). Both alliances share some of the species pool, and ecologically and floristically are separated from each other (Fig. 4 and 5; Table 1). Kobresio-Dryadion comprises mainly xero-, mesophytic dwarf shrubs- and sedges-dominated communities on calcium-rich substrata. Potentillo–Polygonion vivipari includes species-rich tundra meadows with prevalence of mesophytic herbs. Alliances are clearly distinguished from each other in species composition, in habitats and in geographic distribution: Potentillo–Polygonion vivipari is likely restricted to Fennoscandia, whilst Kobresio-Dryadion has Eurasian distribution (Koroleva, 2015). Original diagnoses and nomenclatural types of alliances are different, so they cannot be considered as synonyms. Alliance Potentillo–Polygonion vivipari is not yet disposed in some higher units — order and class.