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.
