The checklist of the syntaxa within the Russian Arctic: current state with vegetation classification
Authors: Matveyeva N. V. , Lavrinenko O. V. 
Published: January 2022

Introduction. A revision of syntaxa was carried out within the framework of the classification of the Brown-Blanquet school identified in the Russian Arctic. A geodatabase (GDB) and GIS, which include several interconnected main modules (see: Matveyeva et al., 2019a, b), with information on species composition, structure, ecology, and geography of syntaxa of all levels, integrated in these databases, became the basis of the presented checklist. This is the first result of compiling information on the vegetation classification, performed with the prospect to produce Prodromus of syntaxa, identified in this territory, with detailed information (character/differential/diagnostic species, ecology, zonal position, geography, bibliography), available in the GDB. It will be in time included in the Prodromus and later will become the basis for a volume in multivolume series on the vegetation of the Russian Federation (see: Plugatar et al., 2020).
Territory. The checklist contains information on syntaxa established in the Russian Arctic within the boundaries of the Circumpolar Arctic Vegetation Map (hereafter CAVM) (CAVM Team, et al., 2003; Walker et al., 2005; Raynolds et al., 2019), as well as on the Barents Sea coast of the Kola Peninsula, which is referred to the tundra zone in accordance with the zonation of the Russian Arctic flat territory (see: Matveyeva, 1998). The list includes syntaxa found north of the treeline — in the tundra zone (subzones of the southern, typical, and arctic tundra) and polar deserts.1 Hence, it follows that there are no syntaxa from the forest-tundra as well as those above the treeline in the mountains adjacent to the tundra zone (Putorana and Anabarskoe plateaus). The syntaxa from the territory of the «Russian Arctic» (Barentsburg, Pyramida) on the West Spitsbergen Island (Spitsbergen archipelago) are also not taken into account (their positioning is logical in Spitzbergern syntaxonomy).
History. The study of the Russian Arctic plant cover began in the second third of the XIXth century in the north-east of the European Russia (Schrenk, 1855) and in Siberia on the Taymyr Peninsula (Middendorf, 1860–1867). After a significant break, it continued in the USSR in the pre-war time and intensified after the end of the Great Patriotic War. The most intense (both in the size of the studied areas and the numbers and duration of the field works) was the period from the mid-1960s to the early 1990s. Researchers working both in other zones and in the Arctic processed the obtained data in accordance with the approaches of the dominant classification, and the relevés were either not published or presented in a small (4–5) number for association. Despite the obvious limitations of this approach, there were published (both in the form of text with listing of few dominants and with relevé tables) both general (Gorodkov, 1935) and regional (Andreev, 1932; Bogdanovskaya-Giyenef, 1938; Smirnova, 1938; Dedov, 2006 [1940]; Aleksandrova, 1956, 1983; Gorodkov, 1956, 1958 a, b; Katenin, 1972) classifications, and checklists — a draft classification of vegetation of the whole Arctic (Aleksandrova, 1979) and classification of Taymyr vegetation (Matveyeva, 1985). In the late 1980s, Russian phytosociologists turned to the Brown-Blanquet floristic (= floristic-sociological (Theurillat et al., 2021), or ecological-floristic (Mirkin, Naumova, 2014)), classification system as the most conceptually substantiated, with generally accepted rules for describing communities in the field and the technique of relevé tabular processing, and also with clear rules for the formation of syntaxon names. In this system, the obligatory publication of the original data and the requirements for its validity when describing the basic syntaxon are strictly postulated, which provides an objective comparison and classification of any plant community types, in whatever system these data are not submitted. Just as it is impossible to imagine the development of taxonomy without the existence of herbarium collections, so it should be an axiom for phytosociologists that since the relevé is the only documentary reflection of a natural phenomenon named «plant community» (Matveyeva, 2008), it should be available for analysis to all syntaxonomists.
Since the second decade of the XXth century, the followers of the Braun-Blanquet system have published thousands of relevés from different regions of the globe, which made it possible to produce a unified classification of vegetation from the Arctic to the tropics and its constant replenishment. Currently, the process of creating electronic databases (archives) of relevés, including the Arctic Vegetation Archive, which accumulates information on circumpolar vegetation is accumulated, is actively underway (Walker et al., 2018).
The starting point when Russian tundra experts began to work consistently, following the principles of this classification, is the first International Meeting on the Classification and Mapping of Arctic Vegetation, which took place in 1992 in Boulder, CO (USA). For the publication of its data, a special issue of the Journal of Vegetation Science (1994, Vol. 5, N 6) named «Circumpolar arctic vegetation» (where 4 papers by Russian syntaxonomists were published) was provided. After 1992, when the intensity of field works decreased sharply, the number of publications with complete characteristics of the communities of the Russian Arctic increased rapidly.The proposed checklist of syntaxa is the result of this almost 30-year acti­vity.
The checklist structure. The arrangement of syntaxa of class rank is mainly the same as in the EuroVegChecklist — hereafter EVC (Mucina et al., 2016): zonal and intrazonal communities of the polar desert zone (one class); zonal (one class) and landscape-forming intrazonal (five classes) communities of the tundra zone; intrazonal communities (13 classes), united into groups according to the gradients of moisture, snow depth and soil mechanical composition.
A syntaxon is represented as follows:
— higher units of the rank Class/Order/Allian­ce (Suballiance): number (for Class), abbreviated rank in English (Cl., Ord., All. (Suball.)), in square brackets — code (if any) from EVC (Mucina et al., 2016); full name, author(s) and year; below is a brief description in two languages: English — in general as in the cited paper with some corrections due to the specificity in syntaxon geography and ecology in the Asian part; Russian — partly in accordance with the English version and/or to Prodromus of higher vegetation units of Russia (Ermakov, 2012), sometimes with minor corrections or clarifications. For new orders and alliances within the zonal tundra class differential taxon combinations are listed;
— syntaxa of the rank Association, Community Type, Community, established on the territory of the Russian Arctic: abbreviated rank in English (Ass., Com. Type, Com.), name, author(s) and year (besides association, the cited papers are included in the Refe­rences). If syntaxon was previously described by European/American authors outside the Russian Fede­ration, the link to the publication, where it was found in the Russian Arctic, is placed in brackets. The ­arrangement of associations is alphabetical;
— syntaxa of units of a lower (within association) rank (subassociation and vicariant, variant, subvariant, facies): abbreviated rank in English (subass. and vicar., var., subvar., fac.), name, in brackets author, year (besides subassociation, the cited papers are included in the References). The arrangement of the syntaxa is as follows: typicum(-cal, -ca), inops, then alphabetically. For subass. typicum authors are not listed (Theurillat et al., 2021), but if it was described by another author and/or in another paper, then the link to it is given in brackets and the paper is included in the References.
All names of syntaxa are given in the author’s edition (as it was published), including the endings of a typical syntaxon within an association (subassociation, vicariant, variant, facia) — typicum, typical, typica.
In different papers, there are two English spellings of Russian surnames: Aleksandrova/Alexandrova, Andreev/Andreyev, Bogdanovskaya-Giyenef/Bogdanovskaya-Gienef, Pristyazhnyuk/Prystyazhnyuk, Savich/Savič. A uniform (the first one) spelling of the surname is used here.
If there was something that caused a disagreement with the author’s decision (including the assignment of an association to a syntaxon of a higher rank), there is a superscript number before the syntaxon name, or before the author’s surname (when it is in brackets), referring to critical comments.

Critical comments.
1 – The name is invalid or needs change because:
1a – no reference to the nomenclature type;
1b – published ineffectively (names published as ‘manuscript’ or ‘unpublished’);
1c – not accompanied by a sufficient diagnosis, no tables with original relevés;
1d – suggested by the author as preliminary;
1e – not obvious from what species syntaxon epithet is formed and it cannot be extracted from the diagnosis and/or tables);
1f – syntaxon with the same name was described earlier (including the case of inversion);
1g – the form of the syntaxon name does not correspond to Art. 10 of «International Code of Phytosociological Nomenclature» — hereafter ICPN (Theurillat et al., 2021);
1h – the given nomenclature type belongs to a different syntaxon, validation does not correspond to ICPN;
1i – the relevé chosen as an association or subassociation nomenclature type does not contain the name-giving taxon of this syntaxon;
1j – there is a subspecies in the original diagnosis and in the tables, while in the syntaxon name the species name is used;
1k – the nomenclature type is given for 2 variants of the vicariant, among which there is no tyicum one;
1l – published or validated in 2002 or later with no indication of novelty (like, Ass. nov.).
2 – the author(s) did not place the syntaxon among the higher units.
3 – the author(s) placed the syntaxon in other higher units than suggested in this list.
4 – the syntaxon was renamed due to a change in its rank; in this checklist it is also given under a new name.
5 – the syntaxon is described by the author(s) in the Community rank but is assigned within the known association as a unit of it internal division.
6 – the author(s) assigned the syntaxon to this class with a question.
7 – the author(s) unreasonably (noted in literature) placed the communities in given syntaxon that needs revision.
8 – in the EVC there is only one author, while in the original source there are two.
9 – it is written that the title proposed by the first author was valid, but according to Principle II of the ICPN it is not.
10 – the author(s) of the syntaxon is(are) incorrect: the syntaxonomic units originally described in the framework of the ecological-physiognomic classification are invalid in accordance with Principle II (Art. 3d ICPN), and have been validated by subsequent authors.
11 – the author(s) assigned the syntaxon to this class/order, but did not refer to an alliance or placed in the alliance other than that proposed in this checklist.
12 – the author(s) attributed the syntaxon to this alliance, but as part of a different class/order, or not attributed to the class/order.
13 – the author(s) changed the rank of the syntaxon in comparison with the original description.
14 – the spelling of the syntaxon name does not correspond to the rules of the ICPN; the correct name [recte[ is given in square brackets.
15 – in the EVC the alliance is placed in another order.
16 – the author(s) of the syntaxon are incorrect, the first author (in brackets) did not give such a name, or incorrect year.
17 – the author(s) of the syntaxon incorrectly cited, priority belongs to other author(s) who published the name earlier and/or effectively.
18 – in the EVC the alliance is placed in synonyms for another alliance, which name was changed but not yet approved (nom. mut. propos).

THE CHECKLIST — see the main text.

Brief analysis of the composition. The checklist is based upon analysis of more than 70 papers, professionally reviewed and published, which contain more than 6,000 geobotanical relevés, that make available information on the composition and structure of 734 syntaxa ranging from association/community type/community to facies. At the mid-2021, the checklist includes 241 associations (152 subassociations and 25 vicariants, 190 variants and 61 subvariants, 13 facies), 35 types of communities and 17 communities from 62 alliances (6 suballiances), 33 orders and 20 classes. Most of the higher rank units — Class/Order/Alliance — are taken from the classification of vegetation in Europe (Mucina et al., 2016)
Class. Of the 20 classes, 19 are in EVC (Mucina et al., 2016), to which we have assigned 207 associations, although we do not consider this decision final. A new class for zonal tundra vegetation Carici arctisibiricae–Hylocomietea alaskani class. prov.2 so far is left in the provisional status. Conventionally is used the class Betulo carpaticae–Alnetea viridis which contains willow scrubs in the valleys and on the interfluves.
Order. Of the 33 orders 29 are in EVC. Among the known ones there is formally described Salicetalia glauco-lanatae so far located in Betulo carpaticae–Alnetea viridis. Three orders (Arctophiletalia fulvae; Chamerio–Betuletalia nanae; Schulzio crini­tae–Aquilegietalia glandulosae) were described by Russian authors. Three new orders (Salici polaris–Hylocomietalia alaskani ord. nov. prov., Caricetalia arctisibiricae-lugentis ord. nov. prov., Eriophoretalia vaginati ord. nov. prov.) are suggested here in the provisional status, for establishing within the tund­ra zonal class Carici arctisibiricae–Hylocomietea alaskani class. prov. Nameless order is proposed for communities dominated by mesophytic arctic and/or arcto­alpine herbs often with dwarf shrubs (Salix arctica/polaris/reticulata, Dryas octopetala/punctata) and few mosses on the southern slopes of hills and high river banks in the tundra zone of Eurasia; conventionally it is placed in the Mulgedio–Aconitetea. According to both species composition and habitat the order Arabidetalia caeruleae is moved from Thlaspietea rotundifolii (as in EVC) into Salicetea herbaceae.
Alliance. Of the 62 alliances 36 are in EVC, 5 of which (Arctophilion fulvae; Caricion stantis, Chamerio angustifolii–Matricarion hookeri; Dryado octopetalae–Caricion arctisibiricae, Polemonio acutiflorum–Veratrion lobeliani) are described by Russian authors. Alliance Oxytropidion nigrescentis, validated in 1998 (Matveyeva 1998, p. 81), is given as valid. The following 8 alliances are valid: Aulacomnio palustris–Caricion rariflorae, Polemonio acutiflorum–Salicion glaucae and Rubo chamaemori–Dicranion elongati on the European North, Carici concoloris–Aulacomnion turgidi, Oxytropido sordidae–Tanacetion bipinnati in Siberia, Androsaco arctisibiricae–Aconogonion laxmannii, Aulacomnio turgidi–Salicion glaucae, Salici pulchrae–Caricion lugentis on Chukotka. Another 7 alliances have invalid names (suggested as preliminary, no nomenclature type was chosen, etc.). For 6 of these validation is necessary and quite simple. An exeption is the alliance Luzulo–Festucion rubrae (Ektova, Ermokhina, 2012), with all invalid associations (no both relevés and diagnoses); after the later are validated they logically could be placed in Loiseleurio-Arctostaphylion. Within the tundra zonal class the alliance Salici polaris–Hylocomion alaskani all. nov. is formally described and the alliances Cassiopo tetragonae–Eriophorion vaginati all. nov. prov. and Poo arcticae–Calamagrostion holmii all. nov. prov. are proposed provisionally. It is recommended to establish 6 alliances (in the checklist with no name) in classes Drabo corymbosae–Papaveretea dahliani (3), Betulo carpaticae–Alnetea viridis (1), Thlaspietea rotundifolii (1) and Mulgedio-Aconitetea (1). Syntaxonomic decisions, other than those derived from the EVC, are made on the positions of 4 alliances within the higher-rank units: Caricion stantis was moved from Sphagno warnstorfii–Tomentypnetalia to Caricetalia fuscae; Dryado octopetalae–Caricion arctisibiricae — from Carici rupestris–Kobresietea bellardii to Carici arctisibiricae–Hylocomietea alaskani class. prov. (see: Lavrinenko, Lavrinenko, 2018a); Potentillo–Polygonion vivipari is recognized (Koroleva et al., 2019) as different from Kobresio-Dryadion, synonym with which it is given in the EVC; the Honckenyo–Leymion arenarii is used compare to the EVC where it is the synonym of Agropyro–Honckenyion peploidis nom. mut. propos. Compared to the author’s decision, the alliance Carici concoloris–Aulacomnion turgidi from Loiseleurio procumbentis–Vaccinietea is moved to Carici arctisibiricae–Hylocomietea alaskani class. prov.
Suballiance. Of the 6 suballiances 4 (Androsaco arctisibiricae–Aconogonenion laxmannii; Astragalo pseudadsurgentis–Calamagrostienion purpurascentis; Caricenion rariflorae; Oxytropido vassilczenkoi–Dryadenion punctatae) are valid, and two (Anemono parviflorae–Salicenion and Pediculari lapponicae–Salicenion) require validation. The suballiance Caricenion rariflorae placed in the checklist in Scheuchzerion palustris was originally established within the Sphagnion baltici, which in the EVC is synonymous with the first name.
Association. Of 241 associations only 34 are known outside the Russian Arctic, and the remaining 207 are new. The known ones are mainly on coastal bio­topes — marshes (15) and dunes (3) — and extremely wet habitats (9). There are 4 associations described earlier in Europe within the large landscape-forming classes (Dryadetum octopetalae, Empetro–Betuletum nanae, Loiseleurio-Diapensietum, Phyllodoco–Vaccinietum myrtilli) which distribution ranges are extended to the European North of Russia, and 3 within small intrazonal classes (Geranietum sylvatici, Potentillo crantzii–Polygonetum vivipari, and Rumici–Salicetum lapponi) found on Kola Peninsula. Only 2 associations, described by European (Dryado–Cassiopetum tetragonae) and American syntaxonomists (Sphagno–Eriophoretum vaginati), occur in the Asian part of the Russian Arctic (with new subunits within both).
The most association-rich are 8 main classes. The two zonal classes include Drabo corymbosae–Papaveretea dahliani (20 associations) in the polar desert zone and Carici arctisibiricae–Hylocomietea alaskani class. prov. (34 associations) in the tundra zone  — 54 in total. 129 associations are identified in the 6 main classes of intrazonal vegetation: Be­tulo carpaticae–Alnetea viridis (29 associations) Loiseleurio procumbentis–Vaccinietea 1960 (22 associations), Carici rupestris–Kobresietea (21 associations), Salicetea herbaceae (16), Scheuchzerio palustris–Caricetea fuscae (25 associations); Juncetea maritimi (16 associations) — 187 in total. The vegetation of other 12 classes is described locally geographically and selectively syntaxonomically.
37 associations were not assigned to any of the known classes. This, in particular, was the case with the vegetation of the polar desert zone (Matveyeva, 2006) before Drabo corymbosae–Papaveretea dahliani class was described in 2016. But it also happened when deciding to assign an association to some well-known class, authors stressed that they did this forcibly in the absence of an adequate unit. For example, before the proposal, albeit provisionally, of the class Carici arctisibiricae–Hylocomietea alaskanii class. prov., even zonal communities from the Arctic tundra subzone were placed in the Loiseleurio procumbentis–Vaccinietea class accentuating that they do not contain a single characteristic species of this class (Kholod, 2007).
Community type is distinguished when author does not establish new association due to the small number (less than 10) relevés in one location, leaving this for the future There are 35 such units, most of which (9) are in the Drabo corymbosae–Papaveretea dahliani in the polar desert zone. It is worth noting two points: 1) almost never Community types reach the association status; 2) not all authors are stopped by a small number of relevés, when naming syntaxa, and many associations are based upon on less than not 10, but even 5 relevés. As a result, units of different status often contain equally little information about their composition.
Community. This rank exists when there is only one relevé, due to both the type rarity and the lack of time. There are 17 such units, with 7 in the polar desert zone.
Two main subordinate levels are used within the association: the first — subassociation and vicariant (not protected by the ICPN), the second — variant. Both reflect small but obvious differences in composition, abundance, constancy of species from the type of association (typicum), conditioned edaphically, locally-climatically, chorologically (Ellenberg, 1956; Braun-Blanquet, 1964) or indicate different stages of succession (Westhoff, van der Maarel, 1978). Differences in the listed characteristics from the type group (typicum) due to ecology are an undoubted reason for identifying several subassociations even in a landscape. To reflect similar differences due to the object location in several areas on latitudinal (in different tundra subzones) or longitudinal (in different sectors of the same zone/subzone) gradients in similar habitats (on the same landscape elements, with the same soil type), subassociation (a unit protected by the ICPN) is used as well. However, the desire to distinguish the reasons that caused such differences is also understandable. Hence, understandable is the interest to the concept of geographic vicariant, perceived by some Russian syntaxonomists working in the Arctic, which is reflected in the checklist (since the unit is not protected by ICPN, after the name in brackets there is a link to References). Leading European phytosociologists E. van der Maarel and W. Westhoff, who in 1993 reviewed an article by N. Matveyeva on the vegetation of Taymyr (Matveyeva, 1994), recalling the concept of geographical races (Becking, 1957), or vicariants (Barkman, 1958), recommended to use the status of a geographic vicariant to reflect changes in the composition of communities of one association related with a geographic location, leaving ecologically determined differences for subassociations.The need for such a division is reflected in the famous paper of F. Daniëls (1982) on Greenland, where the author distinguishes ecologically (habitat-differential) and geographically (area-differential) determined syntaxa, although uses only the name of subassociations.
It is a great pity that the concept of a geographical vicariant, which was formed in the minds of the classics of phytosociology almost 60 years ago, did not find formal support: this unit was not included nor in the 3rd edition of the ICPN (Weber et al., 2000), neither in the 4th (Theurillat et al., 2021). The question of whether such a unit should be covered by the ICPN regulations «... can be resolved with the accumulation of experience in its application» (Weber et al., 2000, p. 6); the results of such experience are reflected in this checklist.
Subassociation. There are 152 subassociations within 71 associations: most of all in the Carici arctisibiricae–Hylocomietea alaskani (24), slightly less in Loiseleurio procumbentis–Vaccinietea (21) and Betulo carpaticae–Alnetea viridis (23), more than 11 in Carici rupestris–Kobresietea bellardii (16), Scheuchzerio palustris–Caricetea fuscae (17), Juncetea maritimi (12) and Thlaspietea rotundifolii (12). Usually there are 2–3 subassociations in one association.
Vicariant. There are 25 vicarians in the 14 associations. 19 of these are latitudinal in associations of zonal, mire, snowbed (Matveyeva, 1994, 1998, 2006) and herb meadow (Zanokha, 1993, 1995a, b) communities within 3 tundra subzones and syntaxa, replacing them in the polar deserts on Severnaya Zemlya (Zanokha, 2001; Matveyeva, 2006. The appeal to the concept of vicariant on Taymyr, where in the only place on the Earth on the mainland at about 900 km a full latitudinal gradient from the tree line to the polar deserts is expressed (Matveyeva, 1998), is quite understandable and logical. The other 6 vicariants are longitudinal: 1 in the European North of Russia (Matveyeva, Lavrinenko, 2011) and 5 on Wrangel Isl. (Kholod, 2007).
Variant. There are 190 variants within 66 associations. There are no clearly formulated rules regarding their fundamental difference from subassociations. It is also not obvious whether the level of variant is the next after subassociation in association subdivision, or these are units of the same rank: in 31 associations, variants are allocated within subassociations or vicariants, in 34 — directly in the association. There is no clear logic behind why even one and the same author follows the first way in some cases, and the second in others.
Subvariant. This unit was used for the division of variants of technogenically disturbed vegetation (Sumina, 2012, 2018), where 54 subvariants (2–5 in each) were identified in 20 variants of 6 associations, as well as of the baydzharakh vegetation in the arctic tundra subzone in Siberia (7 subvariants).
Facies. The unit without differentiaal taxa, recognized by the predominance (with a high abundance) of a species of the «normal» floristic complex of the association, due to particular or sometimes ­extreme abiotic factors, or under anthropogenic impact (Westhoff, van der Maarel, 1978). There are 14 facies in 2 associations of 2 classes on Wrangel Isl. (Kholod, 2007) and in 3 syntaxa of 3 classes in the Bolshezemelskaya tundra (Neshataev, Lavrinenko, 2020).

Conclusion. One of the purposes of publishing this checklist is to draw the attention of northern phytosociologists to assessing the validity of syntaxa and the legality of their position in the Braun-Blanquet system. Our task was to bring together all available information, which is done in this article. Even a simple list of syntaxa makes it possible to assess the completeness of the geographical and syntaxonomic knowledge of vegetation.
Geographically, sytaxonomic information is available for 12 of the 13 Russian floristic provinces (according to CAVM), in which about 130 districts have been investigated. The most studied provinces (from west to east) are Kanino-Pechora, Yamalo-Gydan, Taymyr, East Chukotka, Wrangel Island (the number of published relevés in each more than 600. There are no published data for the Kharaulakh province.
It is not possible to say for sure to what extent the number of associations reflects the presence and distribution communities of 20 classes in different regions of the Russian Arctic. The completeness of the vegetation study depended on the tasks and on the possibility of their implementation. High attention to zonal vegetation is natural, since it is used for subdivision of the territory, for zonal division, and for maps of various scales. Both snowless (Carici rupestris–Kobresietea bellardii) and snowbed (Salicetea herbaceae) communities, as specific for the Arctic, are also always in the sphere of interests. Polygonal mires and bog-hollow vegetation (Scheuchzerio palustris–Caricetea) certainly require much more research, due to their vast areas in the eastern regions of the Siberian Arctic, where these types are not described. For the relatively well-studied shrub communities in the Asian part (conditionally assigned to the Betulo carpaticae–Alnetea viridis), validation of many syntaxa are required; the gap in the description of this object in the northern European regions has just begun to be filled. For 12 associations of grass-forbs communities on the well heated slopes conditionally positioned in the Mulgedio-Aconitetea, new orders and allian­ces, and, potentially, the class are necessary to be established. Unreasonably little data are available for raised bogs (Oxycocco-Sphagnetea), if even these are ­rather common of the southern regions of the tundra zone. Very scattered geographically and sparse syntaxonomic data are on the vegetation of naturally eroded mobile substrates (sand screes, gravel debris, landslides). In the Arctic, as in other regions of the globe, communities are placed in this class not by their species composition, but by habitat (unstable substrate), and the fact of the sparse cover. Only recently the zonal vegetation of polar deserts on horizontal surfaces with quite stable loamy substrates has been classified as a distinct class (Daniëls et al., 2016).
In the list of habitat types with associated described Brown-Blanquet syntaxa from Arctic regions of Europe, Greenland, western North America, and Alaska, there are 5 classes (Walker et al., 2018) which are absent in our checklist: Juncetea trifidi Hadač in Klika et Hadač 1994, Saxifrago cernuae–Cochlearietea groenlandica Micuna et Daniëls in Mucina et al. 2016, Vaccinio-Piceetea Br.-Bl. in Br.-Bl. et al. 1939, Asplenietea trichomanis (Br.-Bl. in Meier et Br.-Bl. 1934) Oberd. 1977, Salicetea purpureae Moor 1958. Communities of these classes either exist in the Russian Arctic, but were not described (e. g. forest «islets» in tundra landscapes — Vaccinio-Piceetea, and the vegetation of rocks and rubble talus — Asplenietea trichomanis), or they exist, but are positioned in the other classes. An open question remains with Junce­tea trifidi on acidic substrates. Final conclusions on these classes will become possible after the thorough analysis of syntaxa throughout the entire circumpolar space.
Even a very brief analysis of the available data revealed numerous cases of invalid names of syntaxa (no indication of the nomenclature type) or inconsistency names with ICPN rules (correct [recte] names are given for 43 ones); leaving the association outside of higher-level units or assigning one basic unit to ­several higher ones, etc. There are more such cases than we have noted now, especially taking into ­account the new edition of the ICPN (for example, the obligatory Latin or English terminology for denoting ranks and new units (ICPN 4th, Art. 3d, 3i, 3o, 5), mutation ­cases (Lat. mutatum, ICPN. 4th, Art. 45), inversions (Lat. inversum, ICPN. 4th, Art. 42) of names and autonym (Lat. autonym, ICPN 4th, Art. 13b, 4d).
Now it becomes possible for each author to take measures to eliminate errors of various kinds to validate their syntaxa. Consolidated participation in joint publication is also possible. This is a necessary step for the next action — preparing the Prodromus of the vegetation syntaxa of the Russian Arctic with the expanded characteristics for all levels.