Abstract. Nitrous oxide (N2O) emissions from permafrost-affected terrestrial ecosystems have received little attention, largely because they have been thought to be negligible. Recent studies, however, have shown that there are habitats in the subarctic tundra emitting N2O at high rates, such as bare peat (BP) surfaces on permafrost peatlands. Nevertheless, the processes behind N2O production in these high-emission habitats are poorly understood. In this study, we established an in situ 15N-labeling experiment with two main objectives: (1) to partition the microbial sources of N2O emitted from BP surfaces on permafrost peatlands and (2) to study the fate of ammonium and nitrate in these soils and in adjacent vegetated peat (VP) surfaces showing low N2O emissions. Our results confirm the hypothesis that denitrification is mostly responsible for the high N2O emissions from BP. During the study period, denitrification contributed ∼ 79 % of the total N2O emissions from BP, whereas the contribution from ammonia oxidation was less (about 19 %). Both gross N mineralization and gross nitrification rates were higher in BP than in VP, with high C/N ratios and a low water content likely limiting N transformation processes and, consequently, N2O production in the latter soil type. Our results show that multiple factors contribute to high N2O production in BP surfaces on permafrost peatlands, with the most important factors being the absence of plants, an intermediate to high water content and a low C/N ratio, which all affect the mineral-N availability for soil microbes, including those producing N2O. The process understanding produced here is important for the development of process models that can be used to evaluate future permafrost–N feedbacks to the climate system.

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.

Abstract. Nitrous oxide (N2O) emissions from permafrost-affected terrestrial ecosystems have received little attention, largely because they have been thought to be negligible. Recent studies, however, have shown that there are habitats in subarctic tundra emitting N2O at high rates, such as bare peat surfaces on permafrost peatlands. The processes behind N2O production in these high-emitting habitats are, however, poorly understood. In this study, we established an in situ 15N-labelling experiment with the main objectives to partition the microbial sources of N2O emitted from bare peat surfaces (BP) on permafrost peatlands and to study the fate of ammonium and nitrate in these soils and in adjacent vegetated peat surfaces (VP) showing low N2O emissions. Our results confirm the hypothesis that denitrification is mostly responsible for the high N2O emissions from BP surfaces. During the study period denitrification contributed with ~79 % of the total N2O emission in BP, while the contribution of ammonia oxidation was less, about 19 %. However, nitrification is a key process for the overall N2O production in these soils with negligible external nitrogen (N) load because it is responsible for nitrite/nitrate supply for denitrification, as also supported by relatively high gross nitrification rates in BP. Generally, both gross N mineralization and gross nitrification rates were much higher in BP with high N2O emissions than in VP, where the high C / N ratio together with low water content was likely limiting N mineralization and nitrification and, consequently, N2O production. Also, competition for mineral N between plants and microbes was additionally limiting N availability for N2O production in VP. Our results show that multiple factors control N2O production in permafrost peatlands, the absence of plants being a key factor together with inter-mediate to high water content and low C / N ratio, all factors which also impact on gross N turnover rates. The intermediate to high soil water content which creates anaerobic microsites in BP is a key N2O emission driver for the prevalence of denitrification to occur. This knowledge is important for evaluating future permafrost –N feedback loops from the Arctic.

The fjell field belt is located in mountains of temperate, boreal and arctic zones above the belts with closed vegetation. The environment of the fjell fields is formed due to severe microclimate and short ­growing season, thin soil layer and snow-free conditions in winter (Tolmachev, 1948). The main feature of fjell field landscape is the sparse plant cover dominated by mosses and lichens. The vegetation of fjell fields is still poorly investigated: some geobotanical relevés are available for Scandinavian Mountains (Nordhagen, 1928, 1943; Gjaerevoll, 1950, 1956), West Greenland (Sieg, Daniëls, 2005; Sieg et al., 2006, 2009; Sieg, Drees, 2007), Spitsbergen (Hadač, 1946, 1989; Eurola, 1968; Möller, 2000), and Putorana Plateau (Matveyeva, 2002). The Khibiny and Lovozero Mountains rise up to 1200 m. The vegetation of higher elevations from 840 to 1200 m was classified according to Braun-Blanquet approach in 2013–2021. Based on 90 relevés, 8 associations (5 as new ones), 2 variants and 1 community type were described (Tables 1–8) which belong to 6 alliances, 6 orders, and 6 classes. To arrange the syntaxa described in Khibiny and Lovozero Mountains in higher classification units correctly, we used the first descriptions of alliances in Fennoscandia (62 relevés) and published data of sparse vegetation in fjell fields in Spitsbergen (57 relevés). Among the Spitsbergen data there are 17 relevés of the ass. Sphaerophoro–Racomietum lanuginosi (Hadač 1946) Hofmann 1968 (Hadač, 1989: 159, Table 16; Möller, 2000: 103, Table 30), 19 relevés of the ass. Anthelio–Luzuletum arcuatae Nordh. 1928 (Möller, 2000: 100, Table 29), 21 relevés of vegetation of the fjell fields, not attributed by the author to any syntaxon (Eurola, 1968: 16, 22). Fennoscandian data (62 relevés) include 15 relevés of the ass. Oxyrie­tum digynae Gjaerevoll 1950 of the Saxifrago stellaris–Oxyrion digynae Gjaerevoll 1950 (Gjaerevoll, 1950: 405, Table VI, rel. 1–15), 10 relevés of the ass. Oppositifolietum (Saxifragetum opposifoliae Gjaerevoll 1950) of the Saxifrago oppositifoliae–Oxyrion digynae Gjaerevoll 1950 (Gjaerevoll, 1950: 422–425, Table XIV, rel. 1–10), 10 relevés of Diapensia–Loiseleuria–Empetrum-Soz. (ass. Loi­seleurio-Diapensietum Nordh. 1943) of the alliance Loiseleurio-Arctostaphylion Kalliola ex Nordh. 1943 (Kalliola, 1939: 175–179, Table 26, rel. 1–10), 12 relevés of Anthelia–Cesia reiche–Luzula arcua­ta-Ass. (ass. Anthelio–Luzuletum arcuatae Nordh. 1928) (Nordhagen, 1928: 311, Table, rel. 1–12), 15 relevés of the ass. Salicetum herbaceae borealis (Cassiopo–Salicion herbaceae) (Nordhagen, 1928: 266–267, Table 42, rel. 1–15). In total 209 relevés were analyzed with use the ExStatR program (Novakovskiy, 2016) based on the Non-metric Multidimensional Scaling (NMS), the Sjørensen-Chekanovsky coefficient was used as a measure of similarity/distance. Plant communities of the class Thlaspietea rotundifolii Br.-Bl. et al. 1947, the alliance Luzulion arcuatae Elvebakk 1985 ex Danilova et Koroleva 2022 are most widely distributed in fjell fields in Khibiny and Lovozero Mountains. The alliance was proposed as provisional in Spitsbergen (Elvebakk, 1985). Here we validate the alliance and propose the ass. Saxifrago oppositifoliae–Flavocerarietum nivalis ass. nov. hoc loco as a neotypus (this paper, Table 2, type relevé (neotypus) of association rel. 5 (2D/20)). The alliance Luzulion arcuatae in Khibiny and Lovozero Mountains includes sparse cover stands dominated by lichens and Racomitrium lanuginosum. It is diffe­rent from snowbed vegetation (Salicetea herbaceae Br.-Bl. 1948) due to the high number of chionophobous lichens, and from lichen–dwarf shrub communities of the alliance Loi­seleurio-Arctostaphylion due to the absence or low number of its diagnostic species (Arctous alpina, Diapensia lapponica, Loiseleuria procumbens). Its communities occur in fjell fields in Spitsbergen, Scandinavian Mountains and in Khibiny and Lovozero Mountains, where two below association were described. Ass. Saxifrago oppositifoliae–Flavocetrarie­tum nivalis ass. nov. (Fig. 2, Table 2 and 8), nomenclature type (holotypus) — rel. 5 (2D/20); 67.6081° N, 33.7783° E, 08.07.2020; 1010 m. Diagnostic species: Alectoria ochroleuca (d), Flavocetraria nivalis (d), F. cucullata, Racomitrium lanuginosum (d), Saxifraga oppositifolia. Two variants are described — ty­pica (Table 2, rel. 1–9) and Carex bigelowii (Table 2, rel. 10–16). Ass. Сetrariello delisei–Racomitrietum lanuginosi ass. nov. (Table 3 and 8), nomenclature type (holotypus) — rel. 2 (83a/19); 67.6116° N, 33.7610°E; 1010 m. Diagnostic species: Cetraria ericetorum, Pseudephebe pubescens, Racomitrium lanuginosum (д), Rhizocarpon geographicum, Umbilicaria cylindrica, U. hyperborea, U. proboscidea. Class Salicetea herbaceae (the alliance Cassiopo–Salicion herbaceae) includes two associations, which are very similar with associations of the alliance Luzulion arcuatae. Ass. Anthelio–Luzuletum arcuatae Nordh. 1928 (Fig. 3, Table 4 and 8). Diagnostic species: Anthelia juratzkana, Harrimanella hypnoides, Gymnomitrion concinnatum (d), G. corallioides, Marsupella apiculata, Micarea incrassata, Ochrolechia frigida, Pseudolophozia sudetica. Аss. Cetrariello delisei–Harrimanelletum hypnoidis ass. nov. (Table 5 and 8), nomenclature type (holotypus) — rel. 2 (11/14), 67.6644° N, 33.5433° E, 1000 m. Diagnostic species: Andreaea rupestris, Carex bigelowii, Cetrariella delisei, Gymnomitrion concinnatum, Harrimanella hypnoides, Huperzia arctica, Hymenoloma crispulum, Marsupella apiculata. Cryptogamic vegetation in fjell fields is classified into two classes: Rhizocarpetea geographici Wirth 1972 (the alliance Rhizocarpion alpicolae Frey ex Klement 1955) and Racomitrietea heterostichi Neumayr 1971 (the alliance Andreaeion petrophilae Smarda 1944). In the first class, the community type Rhizocarpon geographicum includes combination of epilithic lichen synusia (Rhizocarpon geographicum, Umbilicaria cylindrica, U. hyperborea, U. proboscidea, Pseudephebe pubescens, P. minuscula, Stereocaulon vesuvianum). Within the class Racomitrietea heterostichi Neumayr 1971 ass. Andreaeo rupestris–Racomitrietum microcarpi ass. nov. (Fig. 1, Table 1 and 8) is described. Nomenclature type (holotypus) — rel. 6 (83d/19); 67.6116° N, 33.7610° E, 1000 m. Diagnostic species: Andreaea rupestris, Bucklandiella microcarpa (d). Class Loiseleurio procumbentis–Vaccinietea (the alliance Loiseleurio-Arctostaphylion) includes two associations. Ass. Racomitrio lanuginosi–Dryadetum octopetalae Telyatnikov 2010 (Table 6 and 8). Diagnostic species: Antennaria dioica, Dryas octopetala, Festuсa ovina, Vaccinium vitis-idaea subsp. minus. Ass. Flavocetrario nivalis–Caricetum bigelowii ass. nov. (Fig. 5, Table 7 and 8), nomenclature type (holotypus) — rel. 5 (15b/14), 67.7403° N, 34.7260° E, 900 m. Diagnostic species: Carex bigelowii, Juncus trifidus, Salix polaris, Sphenolobus minutus. There are no conditions for mires in Khibiny and Lovozero Mountains. The only minerotrophic mire described in the narrow damp hollow belongs to the ass. Drepanoclado–Ranunculetum hyperborei Hadač 1989, the class Scheuchzerio palustris–Caricetea fuscae Tx. 1937, the alliance Drepanocladion exannulati Krajina 1933. Diagnostic species: Ranunculus hyperboreus, Warnstorfia exannulata, W. sarmentosa. There are 70 species in vascular plant flora of fjell fields. The ratio of biogeographic elements (Koroleva et al., 2021) is as follows: arctic fraction — 63 %, hypoarctic one — 23 %, boreal one — 4 % and polyzonal one — 10 %, that corresponds to the flora of the arctic type. The ordination shows syntaxonomical continuum due to the absence of boundaries between associations (Fig. 5, 6). The main variation of vegetation is associated with species richness, which is connected with snow cover thickness and duration of the gro­wing ­season. Community proximity of the alliance Luzulion arcuatae in the Kola Peninsula and Spitsbergen is confirmed on the ordination diagram (Fig. 6), as well as the isolated position of this alliance from Saxifrago stellaris–Oxyrion digynae, and Saxifrago oppositifoliae–Oxyrion digynae. The alliance Luzulion arcuatae is not a synonym of Saxifrago stellaris–Oxyrion digynae. The proximity of Luzulion arcuatae and Loiseleurio-Arctostaphylion is due to synusiae of lichens (Alectoria nigricans, A. ochroleuca, Flavocetraria cucullata, F. nivalis, and Thamnolia vermicularis) dominated in communities of both alliances. The proximityity of Luzulion arcuatae and Cassiopo–Salicion herbaceae is due to the dominance of liverwort (Gymnomitrion concinnatum, Marsupella apiculata, Pseudolophozia sudetica, etc.) synusiae and moss Harrimanella hypnoides.

The plant cover of the western macroslope of the Urals was studied by the researchers from the Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences since 1989. Investigations, that were carried out in the basin of the Unya river, Pechoro-Ilychsky biosphere reserve and national park «Yugyd va», allowed to obtain information on the structure, dynamics and species diversity for so far poorly studied fir (Abies sibirica) forests within the foothills and mountain zone of Northern and Subpolar Urals (Degteva, Dubrovskiy, 2014). Standard methods adopted in geobotany and forest typology (Ipatov, Mirin, 2008) were used, including Ipatov’s abundance scale for species in herb-dwarf shrub layer assess, at 79 sample plots of 400 m2 size. The data of 32 relevés kept in the phytocenarium of the Institute of Biology were taken into consideration. The level of α-diversity of vascular plants was assessed as a mean value of species number per plot. Ellenberg’s ecological scales (Degteva, Novakovskiy, 2012) adopted to the study area were used in assessing the relations of vegetation and main environmental factors (humidity, soil nutrition, soil acidity and illumination). Data processing was performed using the statistical packages SPSS and PC-ORD (McCune et. al., 2002). Coenoflora of fir forests of area in question includes 169 vascular plant species from 102 genera and 43 families. The leading families are Asteraceae and Poaceae. Species from 16 eco-coenotical groups are present in the coenoflora with 47.1 % belonging to "valley" eco-coenotical group and 29.7 % to taiga-forest one; 8 species are included into the Red Data Book of the Komi Republic.