Armenia is a South Caucasian republic, bordering Georgia, Azerbaijan, Turkey, and Iran. It is a landlocked country with a total area of 29,740 km², at about 145 km from the Black Sea and 175 km from the Caspian Sea. It lies between 38°50' and 41°18' northern latitude and between 43°27' and 46°37' eastern longitude, and measures 400 km along its main axis (north-west to south-east). Armenia is generally a mountainous country, having its lowest point at 375 m a.s.l. and culminating at 4,095 m a.s.l. in the Aragats, with an average elevation of 1,850 m a.s.l.

The location of Armenia at the intersection of two phytogeographical subkingdoms (Boreal and Ancient Mediterranean), together with the diversity in climatic conditions and the active geological processes, have resulted in the formation of diverse ecosystems and high biodiversity with a high level of endemism (Fayvush and Aleksanyan 2016). On the small territory of the country, there are about 3,800 species of vascular plants, 497 species of soil and water algae, 433 species of bryophytes, 4,577 species of non-lichenized fungi, 619 species of lichens, 567 species of vertebrates and about 17,000 species of invertebrates (Fayvush 2023).

A wide range of climatic zones are distinguished within Armenia, which experiences large climatic contrasts because of its intricate terrain and the big climatic gradients (Ministry of Nature Protection of the Republic of Armenia 2015). The basic climate types mainly follow the elevational gradient, from dry subtropical up to severe alpine. The average annual temperature ranges from -8°C in high-altitude mountainous regions (2,500 m a.s.l. and higher) to 12–14°C in low-traced valleys. The overall climate is best characterised as dry continental, in some areas with an annual rhythm like the Mediterranean climate regime. The average annual precipitation in Armenia is 592 mm. The most arid regions are the Ararat valley and the region of Meghri with annual precipitation of 200–250 mm. The highest annual precipitation of 800–1000 mm is observed in high-altitude mountain regions.

From the orographical and physico-geographical points of view, Armenia forms the northern edge of the system of folded-block mountains of the Armenian Highland. Unlike the Greater Caucasus, Armenia and the Lesser Caucasus are not a single, distinct watershed ridge. It is a system of coulisse-spaced ridges that merge with the mountain formations of the inner parts of the Armenian Highland and adjacent high areas (Aslanyan 1958, 1985). Four main geomorphological regions can be recognized within Armenia. (1) Mountain ridges and valleys in the north-east of the country which bear witness of extensive erosion. (2) Areas covered by lava of relatively recent (upper Pliocene) origin within Asia Minor are characterised by gentle slopes with little evidence of erosion but, in which larger rivers have carved out deep gorges and canyons. (3) A series of ridged mountains in the south of Armenia, which constitute the Lesser Caucasus system and show intense erosion. (4) The Ararat Valley represents the lowest part of the Ararat depression covered with alluvial and proluvial sediments (Aslanyan 1958; Gabrielyan 1962; Dumitrashko 1979).

In our study we tried to cover as much of the country’s dry grassland diversity as possible within 11 days, with a focus on the northwestern and central parts (Figure 1). In total, we sampled in five of the 11 administrative provinces of the country (Aragatsotn, Ararat, Gegharkunik, Shirak, Vayots Dzor) and seven of the 12 floristic regions. We covered an elevational gradient from 1,338 to 2,350 m a.s.l.

So far, the syntaxonomy of grassland or thorn-cushion vegetation of Armenia hasn’t been developed yet. The only existing vegetation typologies are based on the dominance approach. The first overview of the Armenian vegetation types was performed by Grossgeim (1928). He distinguished eight main types of vegetation: (1) aquatic and bog vegetation; (2) forest vegetation; (3) semi-deserts; (4) mountain-xerophilous vegetation (mountain semi-desert); (5) mountain steppes; (6) meadow-like vegetation; (7) solonetzs and solonchaks; (8) weeds. In the semi-desert type, he selected three subtypes: (a) alkaline-loamy semi-desert on the alluvium of the Aras River; (b) wormwood semi-desert on eruptive rocks; (c) sandy semi-desert.

Takhtajan (1941) explored the phytogeographic patterns of Armenia, including the division of the region into phytogeographic provinces and districts, the historical development of its vegetation, and the classification of vegetation into broad types. Among these types, subalpine vegetation, mountain-steppes, xerophilous vegetation of skeleton mountains, and wormwood semi-deserts could be considered as the scope of our study.

Makagian (1941) developed the vegetation typology of Armenia in more detail. The steppe and steppe-like vegetation included in his scheme was classified as:

• Stony semi-deserts (wormwood semi-desert, wormwood-ephemeral semi-desert, wormwood semi-desert with perennial grasses, etc.)
• Steppes (grass-forb and dry forb-grass steppe, feather-grass steppe, beardgrass steppe, fescue and fescue-junegrass steppe, mixed-grass steppe, forb and legume steppe)
• Meadow-steppes (grass meadow-steppe, forb and forb-grass meadow-steppe, legume meadow-steppe, dwarf-sedge meadow-steppe)
• Highland xerophytic vegetation (Minor-Asian thorn-cushion shrubs of Astracantha, Acantholimon etc., xeromorphic vegetation of screes and rocks)

Afterwards, the classification of natural grasslands of Armenia was done by Ziroyan (1989) on the principles of the dominant approach. The author distinguished five vegetation types of desert and steppe vegetation which have strong zonal character and mainly are characteristic to a particular altitudinal belt: deserts (two classes of formations, 16 formations) in the lowest elevations up to 1,000 m a.s.l.; semi-deserts (two classes of formations, 12 formations) at the elevations 1,000–1,300 m a.s.l.; highland xerophytic vegetation (one class of formations, 12 formations), 1,200–1,600 m a.s.l.; mountain steppes (two classes of formations, 12 formations), 1,600–2,000 m a.s.l.; mountain meadow steppes (two classes of formations, 12 formations), 2,000–2,400 (occasionally up to 2,800) m a.s.l.

Fayvush (1992) presents a detailed classification of the types of mountain steppes of Armenia based on the dominance approach. The author distinguishes four subtypes (true steppe, thorny-cushion steppe, shrubby steppe and meadow steppe) and 12 classes of formations within it.

In the Transcaucasus region, the first work with a description of syntaxa following the Braun-Blanquet approach was done by M. Guinochet in Azerbaijan and Georgia. Guinochet (1984) described two associations of steppe-like communities without an assignment to higher syntaxonomic units. The association Ziziphoro serpyllaceae-Scutellarietum orientalis Guinochet 1984 is characterized by the presence of many therophytes and is described from the lower elevations in Azerbaijan. Guinochet concludes that this vegetation type could be like the class Thero-Brachypodietea and emphasizes that a unique class and order should be described to include this association. The other association is described from higher elevations in the Pirqulu State Reserve (Azerbaijan), from the subalpine belt: Onobrychieto cyri-Festucetum sulcatae Guinochet 1984 nom. inval. (Article 2b ICPN, Theurillat et al. 2021). This association comprises mountain steppes and is similar, according to M. Guinochet, to the concept of the subalpine steppe of Gadzhiev (1962) from the national typology of Azerbaijan. Additionally, Guinochet (1984) described in Georgia another association from the alpine belt not belonging to the steppic vegetation and assigned to the class Carici rupestris-Kobresietea bellardii: Alchemillo caucasicae-Festucetum supinae, together with the new order Campanulo-tridentatae-Caricetalia tristis and the new alliance Alchemillo-Festucion supinae, all three being invalidly published due to insufficient original diagnosis (Article 2b ICPN, Theurillat et al. 2021). Lately, there was an attempt to classify the phryganoid vegetation of the Nakhchivan region of Azerbaijan (Jabbarov et al. 2020). The authors outlined several association-level units without a formal description (“Thymeto-Acantholimonetum bracteatae”, “Thymeto-Onobrychetum cornutae”), and assigned them to the order Astragalo-Brometalia Quézel 1973 and the class Astragalo-Brometea Quézel 1973. Recently, a new study on the syntaxonomy of alpine and subalpine grasslands has been conducted in Georgia (Nakhutsrishvili et al. 2022). The authors proposed a new class Bromopsio variegatae-Festucetea ovinae to unite subalpine meso-xeric and mesic grasslands, including one new order, three alliances and seven associations. None of the suggested units were published validly due to insufficient original diagnoses.

For the Northern Caucasus, Tsepkova (1987) proposed a new class of high-mountain arid grasslands with the provisional name Bothryochloo-Salvietea, which according to Vynokurov et al. (2021) is a syntaxonomic synonym of the Festuco-Brometea. Other steppic grasslands of the Northern Caucasus have been traditionally assigned to the class Festuco-Brometea (Tsepkova 2005; Demina et al. 2017; Vynokurov et al. 2021).

In Turkey, several high-level syntaxonomic units have been established for dry grasslands and thorn-cushion vegetation. Zohary (1973) united semi-desert and wormwood steppe grasslands into the class “Artemisietea fragrantis anatolica” Zohary 1973 nom. inv. (Art. 2b ICPN), and proposed the class “Astragaletea armeno-turcica” Zohary 1973 nom. inv. (Art. 2b ICPN) for subalpine tragacanthic vegetation in this region. Simultaneously, Quézel (1973) described another unit for hedgehog plant communities in the subalpine zone of the Taurus Mountains in Turkey, occurring at elevations 2000–2500 m a.s.l., beyond the tree line – Astragalo-Brometea Quézel 1973. In the same publication, Quézel (1973) also published another class of xero-mesophytic and mesophytic subalpine grasslands, occupying higher altitudes than tragacanth vegetation communities: Trifolio anatolici-Polygonetea arenastri Quézel 1973. In the eastern part of Turkey, in Eastern Anatolia, there were some syntaxonomic investigations of steppe vegetation (Çetik and Tatlı 1975; Tatlı 1991; Ocakverdi 1992; Hamzaoğlu 2006; Öztürk et al. 2015). Ocakverdi (1992) surveyed the vegetation (including steppe vegetation) in the region of Turkey bordering with Armenia. He distinguished two physiognomic types of steppe vegetation (grass steppe and tragacanth steppe) and three altitudinal variants: “plain” steppe (1,675–1,725 m a.s.l., mainly grass steppe vegetation), lower mountain steppe (1,750–1,850 m a.s.l., both grass steppe and tragacanth steppe) and high-mountain steppe (1,950–2,696 m a.s.l., grass steppe). He proposed four associations, none of them published validly (Art. 1 ICPN). Later, Ocakverdi et al. (2009) described 10 new associations from the same region (Kısır Mountain). Hamzaoğlu (2006) studied steppe communities of East Anatolia. He united the studied vegetation to a new order Festuco oreophilae-Veronicetalia orientalis Hamzaoğlu 2006, subordinated to the class Astragalo-Brometea Quézel 1973.

In another bordering region, Iran, xerophilous grassland and scrub communities were first delineated by Zohary (1973), who proposed several vegetation classes: “Artemisietea fragrantis anatolica” Zohary 1973 nom. inv. (Art. 2b ICPN) for wormwood steppe grasslands in Northwestern Iran and Anatolia, “Artemisietea herbae-albae iranica” Zohary 1973 nom. inv. (Art. 2b ICPN) grouping wormwood semideserts in the Central Plateu of Iran, and “Astragaletea iranica” Zohary 1973 nom. inv. (Art. 2b ICPN) for tragacanth communities in Iran and Iraq. Later, the vegetation of the subalpine and alpine belts of the Alborz Mountains have been studied by Klein (1982, 1987). He described several new classes: Onobrychidetea cornutae Klein 1987 nom. inval. (Art. 2b ICPN) from the lower alpine belt of Alborz (3,200–3,500 m a.s.l.) and Prangetea ulopterae Klein 1987 nom. inval. (Art. 2b ICPN) from the subalpine belt of Alborz (2,500–3,200 m a.s.l.), aimed to unite high-mountain hedgehog communities and xeric tall-herb vegetation respectively. Also, from the subalpine belt of the northern macroslope of Alborz Mountains, Klein and Lacoste (1994) described one association subordinated to the Festuco-Brometea, Alchemilletum plicatissimae Klein et Lacoste 1994, but did not assign it to an alliance or order.

In general, the class Astragalo-Brometea is the most widely used name to unite the dry grasslands and thorn-cushion vegetation in the western part of the Irano-Turanian region. However, its conceptual boundaries have undergone significant changes over time, both geographically and physiognomically. Many researchers now extend its scope to include tragacanth vegetation not only from the subalpine belt but also from the lower elevations, as well as chamaephyte-dominated phryganoid vegetation, non-tragacanth dry grasslands at lower elevations, saline steppes, and gypsophilous rocky grasslands (Ketenoğlu et al. 1983; Akman et al. 1984; Aydoğdu et al. 1994; Aydoğdu et a. 2004; Hamzaoğlu et al. 2004; Kaya 2011). Additionally, xero-mesophytic and mesophytic grasslands at higher elevations, which were classified by Quézel (1973) as a separate class Trifolio-Polygonetea, are sometimes included within the Astragalo-Brometea (Eren et al. 2004; Parolly 2004). Some authors have proposed extending the concept of the class also to the northern part of Iran, synonymizing the Onobrychidetea cornutae and Prangetea ulopterae described there (Parolly 2004). Recently, the dry feather-grass steppes of Tajikistan also were provisionally included into the Astragalo-Brometea (Nowak et al. 2016, 2018).

We sampled 111 plots of 10 m²- size (Suppl. materials 1, 2) during the 13^th Field Workshop of the Eurasian Dry Grassland Group (EDGG) in Armenia, from 26 June to 6 July 2019 (Aleksanyan et al. 2020; for distribution of sites, see Figure 1). Within each plot, we recorded vascular plants and terricolous bryophytes and lichens with the shoot presence method (Dengler 2008). Besides, we estimated their percentage cover on a continuous scale (for discussion of advantages of this method compared to ordinal scales, see Dengler and Dembicz 2023). Specimens that could not be determined in the field were dried and taken to the lab for further determination.

Other environmental and structural parameters that were recorded in situ following the EDGG sampling methodology (Dengler et al. 2016), included: geographical position (latitude, longitude), elevation (m), slope aspect (°), slope inclination (°), maximum microrelief (cm), soil depth (cm, mean and SD of five measurements per plot), vegetation covers (%; total vegetation, shrub layer, herb layer, cryptogam layer), cover of litter (%), covers of stones and rocks, gravel, and fine soil (all three fractions summing up to 100%), maximum height of shrubs (m), maximum height of herbs (cm), height of herb layer (cm, mean and SD of five measurements with a falling disc per plot), and land use details (grazing, mowing, burning, abandonment).

Soil was collected as mixed samples from the uppermost 15 cm of the soil in five random points inside each plot. After air drying and sieving to the fine-soil fraction, the following parameters were measured in the lab: pH (in H₂O), electrical conductivity (μS cm^-1), organic C content (%), humus content (%), N content (%), and C/N ratio. Southing was calculated from aspect as -cos (aspect).

The nomenclature of vascular plants was standardised to Euro+Med (2023) for vascular plants, Hodgetts et al. (2020) for bryophytes, Nimis et al. (2018) for lichens. For some groups of closely related species that could not always be distinguished, we defined additional species aggregates (“aggr.”; see Suppl. material 3). The value distribution of all recorded and analysed numerical environmental, structural and biodiversity variables is given in Suppl. material 4. The complete data are stored in and available from the GrassPlot database (Dengler et al. 2018; Biurrun et al. 2019; https://edgg.org/databases/GrassPlot) as dataset “AM_B”.

We selected a TWINSPAN resolution where the terminal clusters were floristically still well-characterised and not too small. These clusters were then assigned to the rank of association. Alliance, order and class levels were assigned to higher cut levels of the dendrogram, with the double aim to have floristically well differentiated and ecologically and chorologically interpretable units on a comparable level as these hierarchies have in Mucina et al. (2016).

After defining the hierarchical units, we carefully checked the syntaxonomic literature of the neighbouring countries to determine whether syntaxa with this content already existed. If this was the case, we took the established name. If not, we formally described new syntaxa according to the ICPN (Theurillat et al. 2021). Following Recommendation 7A of the ICPN, we refrained from establishing new associations when we had fewer than 10 relevés and instead treated the respective cluster as an informal community at association rank. Likewise, we refrained from a formal description of the new class that was supported by our analyses, suggesting that this should first be “validated” in a broader-scale analysis involving the neighbouring countries of Armenia.

Modified TWINSPAN resulted into 16 clusters with five main groups of clusters: A (clusters 1–3), B (4–6), C (7), D (8–10) and E (11–16) (Figure 2). The synoptic table built with these five main groups is shown in Suppl. material 7.

The group A (clusters 1–3) completely consisted of the relevés originally assigned to the class Astragalo-Brometea, including the type order Astragalo-Brometalia Quézel 1973 (in the cluster 2), described from the Taurus Mountains in South-Western Turkey (Quézel 1973). The plots assigned to the other orders of this class with their corresponding types were also included in this group of clusters: Drabo-Androsacetalia Quézel 1973 (cluster 2) from the same Taurus Mountain range; Hyperico linarioidis-Thymetalia scorpilii Akman et al. 1987 (cluster 1) from the Ilgaz Mountains in North-Western Turkey; Onobrychido armenae-Thymetalia leucostomi Akman et al. 1985 (cluster 3) described from Central Anatolia. Plots from Armenia did not fit into this group.

The second group B (clusters 4–6) comprised plots from the high-mountain steppe vegetation. Cluster 4 consisted mainly of relevés from the northern slope of the Alborz Mountains in Iran, assigned to the association Alchemilletum plicatissimae Klein et Lacoste 1994. Plots from the Northern Caucasus region assigned to the alliance Artemisio chamaemelifoliae-Bromopsion variegatae Vynokurov in Vynokurov et al. 2021 were classified into cluster 5, together with some plots from Armenia. Cluster 6 comprised plots sampled near the Kısır Mountain in Turkey, in Eastern Anatolia. They were originally assigned to several associations of the class Astragalo-Brometea but without placement in alliances and orders (Ocakverdi et al. 2009).

Thorn-cushion communities from Eastern Anatolia are combined in the group C (cluster 7). They were originally assigned to the order Festuco oreophilae-Veronicetalia orientalis Hamzaoğlu 2006 of the class Astragalo-Brometea, together with its type alliance Festuco oreophilae-Veronicion orientalis Hamzaoğlu 2006 and the respective association Astragalo-Onobrychidetum cornutae Gümüs 1992. Even though this cluster was not placed in the corresponding group A in the dendrogram (Figure 2), they seem closely related according to the ordination (Figure 3).

Clusters 8–10 formed group D. It consisted exclusively of plots from Armenia. Among them, cluster 8 contained the most xeric communities sampled in the driest parts of Armenia, followed by cluster 10. Cluster 9 was transitional between the groups D and E.

The group E (clusters 11–16) was formed by plots containing the more ‘typical’ Festuco-Brometea species, mostly from the region of the Northern Caucasus. Cluster 11 was comprised mainly of rocky grasslands belonging to the order Asphodelino tauricae-Euphorbietalia petrophilae Vynokurov in Vynokurov et al. 2021; cluster 12 contained grass steppes mostly of the Festucetalia valesiacae. Cluster 13 combined mountain steppes exclusively from Armenia. Clusters 14–16 comprised mostly meso-xeric communities of the order Brachypodietalia pinnati from the Northern Caucasus. A synoptic table with the five distinguished groups of clusters (A–E) is provided in Suppl. material 7.

In our 111 plots of 10 m², we recorded a total of 739 vascular plant, 40 bryophyte and 13 lichen taxa (subspecies, species, aggregates and sections, further as ‘species’). The species richness per plot ranged from 21 to 85, with a mean of 47.3. On average there were 46.8 vascular plant, 0.4 bryophyte and 0.1 lichen species per plot. The most frequent vascular plant was Galium verum (in 72% of all plots), followed by Thymus kotschyanus (59%), Teucrium capitatum (58%), Poa bulbosa (55%), Dactylis glomerata (54%), Scutellaria orientalis aggr. (53%), Koeleria macrantha (51%), Stachys recta (50%) and Potentilla recta aggr. (50%). The most frequent bryophytes were Syntrichia ruralis (27%), Ptychostomum imbricatulum (19%) and Syntrichia montana (14%). Lichens were absent in most plots, with the most frequent one (Cladonia foliacea) reaching just 4%.

The most meaningful modified TWINSPAN classification of the plots from Armenia resulted in the 12-cluster solution (Figure 4). The first cluster (X) had only a single relevé of scree vegetation recorded in the Vayots Dzor Province near Hermon. The rest of the clusters are interpreted at the community or association level. Clusters 1.1.1.1–1.1.3.2 consisted of the most xeric plots of the semi-desert, rocky and thorn-cushion vegetation in the lower elevations. Clusters 2.1.1.1 and 2.1.1.2 represent plots of mountain meadow steppes from the highest elevations. Clusters 2.2.1.1–2.2.1.4 consisted of plots of thorn-cushion and steppic grasslands of so-called mountain steppes.

Ordination of the plots with the assignment to one of these clusters revealed that the first axis of the DCA graph (Figure 5) corresponds to a gradient of moisture and temperature connected with the elevation range. The most mesic plots occupied higher altitudes (cluster 2.1.1.1), while the most xeric ones were distributed in the lower elevations (clusters 1.1.2.1–1.1.3.2). The climatic-elevation gradient and community parameters correlated with the differentiation of two higher classification units – Ziziphora tenuior-Stipa arabica grasslands and the class Festuco-Brometea.

Resulting from our analyses of the Armenian data and the comparison with the syntaxa of neighbouring territories, we propose the following syntaxonomic scheme for the dry grassland and thorn-cushion communities of Armenia, including a single plot with an unclear assignment (Table 1). According to our literature overview and the analysis of the West Asian and Caucasian dataset, we concluded that most of the syntaxa found are new to science. The formal descriptions of the new syntaxa (“Vynokurov et al. 2024”) are provided in Appendix 1.

The proposed classification of the Armenian dry grassland and thorn-cushion communities is shown in the synoptic table (abbreviated version: Table 2; full version: Suppl. material 2). The distribution of the alliances is shown in Figure 6, typical stands of the association-level units are visualised in two photo plates (Figures 7, 8), while the site conditions, structure and species richness of the syntaxa of the four hierarchical levels are compared in Figures 9–13. In the following, we provide brief descriptions of the diagnostic species and information on ecology and distribution for all syntaxonomic levels and additionally on the community structure for the association-level units. The diagnostic species are listed alphabetically, with the highly diagnostic ones highlighted in bold and bryophytes and lichens marked with B and L, respectively.

Euphorbia orientalis-Melilotus officinalis scree community (Figure 7A)

One cluster in our analysis consisted of only a single relevé of scree vegetation. For this instance, we assume that a corresponding vegetation type needs to be described in the future in the rank of an order or even a class when enough relevant data is available. The aforementioned relevé was sampled in the Vayots Dzor Province, near Hermon (39.8812°N, 45.43254°E), 1,739 m a.s.l., aspect 135°, inclination 46°, 2 July 2019, total vegetation cover: 50%:

Alyssum alyssoides: 0.5, Arenaria serpyllifolia aggr.: 0.1, Asperula arvensis: 0.2, Buglossoides arvensis: 0.1, Bupleurum commutatum: 0.01, Caucalis platycarpos: 0.1, Cerastium ruderale: 3, Chaerophyllum bulbosum: 0.5, Cleome ornithopodioides: 0.01, Convolvulus arvensis: 0.1, Coronilla coronata: 2, Crepis pulchra: 2, Euphorbia orientalis: 15, Galium spurium: 1, Galium tenuissimum: 0.3, Holosteum marginatum: 0.1, Lactuca viminea: 0.5, Lamium amplexicaule: 0.01, Medicago rigidula: 0.1, Melica taurica: 1, Melilotus officinalis: 5, Michauxia laevigata: 0.5, Nepeta trautvetteri: 0.3, Noccaea perfoliata: 0.01, Prangos ferulacea: 1, Reichardia dichotoma: 0.3, Salvia verticillata: 30, Sanguisorba minor: 2, Saponaria orientalis: 0.2, Secale vavilovii: 2, Stachys recta: 0.5, Valerianella uncinata: 0.1, Vicia sativa: 0.3, Zosima absinthiifolia: 4.

Potential class 1: Ziziphora tenuior-Stipa arabica grasslands – Western Asian dry grasslands and xeric thorn cushion communities

Diagnostic species: Achillea arabica, Aegilops cylindrica, Agropyron cristatum, Allium pseudoflavum, Alyssum turkestanicum, Androsace maxima, Anisantha tectorum, Arabis auriculata aggr., Arenaria serpyllifolia aggr., Artemisia fragrans, Asperula arvensis, Bromus danthoniae, B. japonicus, B. squarrosus, Centaurea aggregata, Chardinia orientalis, Crepis sancta, Crupina vulgaris, Dianthus orientalis, Helianthemum ledifolium, Helichrysum plicatum, Holosteum marginatum, H. umbellatum, Marrubium parviflorum, Meniocus linifolius, Minuartia hamata, Noaea mucronata, Poa bulbosa, Sideritis montana, Stachys inflata, S. lavandulifolia, Stipa arabica, S. capillata, S. holosericea, Taeniatherum caput-medusae subsp. crinitum, Tanacetum aureum, Teucrium capitatum, Thymelaea passerina, Xeranthemum squarrosum, Ziziphora tenuior.

Ecology and distribution. Communities of the potential new class occur in the lower elevations in dry conditions and include semi-desert vegetation, xeric thorn-cushion communities, and xeric grasslands. Within Armenia, it is represented by one order and three alliances.

Order 1.1: Cousinio brachypterae-Stipetalia arabicae – Western Asian dry grasslands and xeric thorn cushion communities

Diagnostic species: Identical with those of the monotypic class.

Ecology and distribution. Communities of this order are distributed in Transcaucasia and possibly even broader within Western Asia. We expect them to occur throughout Western Asia in dry conditions (semi-deserts, dry steppe-like communities, low-elevation thorn-cushion communities). Also, according to our analysis, communities of this order may occur even in higher elevations on rocky substrates.

Alliance 1.1.1: Onobrychido michauxii-Stipion capillatae – Transcaucasian rocky dry grasslands

Diagnostic species: Astracantha condensata, Onobrychis michauxii, Salvia aethiopis, Stachys lavandulifolia, Teucrium capitatum, Veronica multifida (mainly negatively differentiated central alliance).

Ecology and distribution. Communities of this alliance are distributed in higher elevations than those of the other two alliances included in this order. This alliance is a transitional unit between this order and the order Onobrychido transcaucasicae-Stipetalia pulcherrimae, comprising Transcaucasian mountain steppes (see below).

1.1.1.1: Stachys lavandulifolia-Astracantha condensata community (Figure 7B)

Diagnostic species: Asperula arvensis, Astracantha condensata, Centaurea phrygia subsp. abbreviata, Crepis ciliata, Euphorbia orientalis, Gypsophila elegans, Herniaria hirsuta, Leptunis trichodes, Melica taurica, Nepeta racemosa, Onobrychis michauxii, Onosma setosa, Salvia aethiopis, Sempervivum transcaucasicum, Stachys lavandulifolia, Tanacetum aureum, Teucrium orientale, Tragopogon dubius, Viola occulta, Zosima absinthiifolia.

Structure, ecology and distribution. We sampled this vegetation type in the Gegharkunik (vicinity of the town of Sevan, Shorja) and Vayots Dzor (Hermon, vicinity of Gnishik and Khachik) provinces. These communities were located at the most south-facing rocky slopes with shallow soil and low humus content. The herb layer was sparse and with a high representation of Irano-Turanian species, e.g. Astracantha condensata, A. microcephala, Stachys lavandulifolia, Teucrium orientale.

1.1.1.2: Marrubio parviflorae-Stipetum capillatae (Figure 7C)

Diagnostic species: Allium cardiostemon, Centaurea ovina aggr., Euphorbia condylocarpa, Marrubium parviflorum, Stipa capillata.

Structure, ecology and distribution: These communities were sampled on slopes with shallow rocky substrates in Gegharkunik (Ardanish), Lori (near Shirakamut) and Vayots Dzor (vicinity of Gnishik and Khachik) provinces. The association differed by a higher herb layer cover compared to the previous community and the highest participation of hemicryptophytes among all associations of the class. The dominant species were Festuca valesiaca aggr., Onobrychis cornuta and Teucrium capitatum.

Alliance 1.1.2: Artemision fragrantis – Transcaucasian wormwood semi-deserts

Diagnostic species: Agropyron cristatum, Allium pseudoflavum, Alyssum turkestanicum, Androsace albana, Arenaria serpyllifolia aggr., Artemisia fragrans, Astragalus hyalolepis, Bromopsis riparia, Ceratocephala falcata, Cousinia brachyptera, Crupina vulgaris, Cuscuta araratica, Consolida hispanica, Didymodon tophaceus (B), Meniocus linifolius, Minuartia hamata, Noaea mucronata, Peganum harmala, Polygala hohenackeriana, Sclerocaryopsis spinocarpos, Syntrichia caninervis (B).

Ecology and distribution: Artemisia fragrans semi-deserts in Armenia are distributed in the lowest elevations in the country. We did not sample other semi-desert types, but we can expect that Armenian loamy and sandy semi-deserts will also be probably included in this unit. In our dataset, this alliance is represented by a single association.

1.1.2.1: Noaeo mucronatae-Artemisietum fragrantis (Figure 7D)

Diagnostic species: identical with those of the monotypic alliance.

Structure, ecology and distribution: This association is typical for the Aragatsotn province (vicinity of Dashtadem and Tatool). The sampled plots were distributed at the lowest elevations with the highest mean annual temperature and lowest mean annual precipitation compared to the other studied associations. The communities were dominated by Artemisia fragrans, Poa bulbosa, and Taeniatherum caput-medusae subsp. crinitum. The herb layer is relatively sparse and with a high representation of therophytes (e.g. Alyssum turkestanicum, Bromus squarrosus, Ceratocephala falcata, Crupina vulgaris, Sclerocaryopsis spinocarpos) and characteristic chamaephytes (Artemisia fragrans, Noaea mucronata).

Alliance 1.1.3: Acantholimono caryophyllacei-Stipion holosericeae – Transcaucasian dry grasslands and xeric thorn-cushion communities

Diagnostic species: Acantholimon vedicum, Aegilops cylindrica, Aethionema carneum, Arabis auriculata aggr., Bromus japonicus, Bunium microcarpum, Chardinia orientalis, Crepis sancta, Crupina vulgaris, Ephedra procera, Galium verticillatum, Gaudiniopsis macra, Helianthemum ledifolium, Noccaea perfoliata, Papaver minus, Roemeria hybrida, Stachys inflata, Stipa arabica, S. holosericea, Taeniatherum caput-medusae subsp. crinitum, Petrorhagia cretica, Ziziphora tenuior.

Ecology and distribution: This unit comprises vegetation traditionally known as ‘highland xerophytic vegetation’. It includes dry grasslands and xeric tragacanth communities distributed above the semi-desert belt and below the mountain steppe altitudinal belt. We distinguish one association and one community within this alliance.

1.1.3.1: Acantholimono caryophyllacei-Stipetum holosericeae (Figure 7E)

Diagnostic species: Acantholimon caryophyllaceum, Aegilops triuncialis, Carduus hamulosus, Crepis sancta, Geranium lucidum, Lomelosia rotata, Noccaea annua, Stipa zalesskii subsp. pontica, Torilis arvensis, Xeranthemum squarrosum.

Structure, ecology and distribution: We sampled this association mainly in the Vayots Dzor province (Hermon, vicinities of Areni, Gnishik and Khachik), and also in one locality in Aragatsotn province (near Tatool). The communities were distributed on shallow soils, but with higher humus content and lower gravel cover compared to the other associations of this class. Acantholimon caryophyllaceum, Stipa holosericea, and Taeniatherum caput-medusae subsp. crinitum are the dominant species in this association. Among other species, Irano-Turanian elements often occur, such as Achillea arabica, Eryngium billardierei, Hypericum scabrum, and Thymus kotschyanus.

1.1.3.2: Stachys inflata-Acantholimon vedicum community (Figure 7F)

Diagnostic species: Acantholimon vedicum, Aegilops biuncialis, A. cylindrica, Aethionema carneum, Androsace maxima, Arabis auriculata aggr., Artemisia fragrans, Aspicilia hispida (L), Astragalus ornithopodioides, Bunium microcarpum, Callipeltis cucullaria, Camelina laxa, Chardinia orientalis, Cousinia daralaghezica, Crossidium squamiferum (B), Crucianella exasperata, Crupina vulgaris, Cuscuta pedicellata, Ephedra procera, Galium verticillatum, Gaudiniopsis macra, Helianthemum ledifolium, Holosteum marginatum, Lactuca tuberosa, Lamium amplexicaule, Onobrychis atropatana, Papaver minus, Petrorhagia cretica, Stachys inflata, Stipa arabica, Tanacetum aureum, Trinia glauca, Valerianella coronata, Ziziphora tenuior.

Structure, ecology and distribution: We sampled this vegetation type in Ararat (vicinity of Tigranashen) and Vayots Dzor (vicinity of Gnishik) provinces. Communities were distributed at lower elevations with high mean annual temperature and low mean annual precipitation. The substrate differed by the most alkaline soil reaction (mean pH: 8). The herb layer was sparse and with a high representation of Irano-Turanian and Mediterranean therophyte species (Aegilops spp., Crupina vulgaris, Petrorhagia cretica, Ziziphora tenuior), while the cover of hemicryptophytes was the lowest among all studied communities. These communities did not have clear dominants, but Chardinia orientalis, Stachys inflata, Stipa arabica, and S. sareptana subsp. anisotricha occurred with higher cover than the other species. The species richness of vascular plants, bryophytes and lichens was higher compared to the other associations of the class.

Class 2: Festuco-Brometea – Mesoxeric and xeric basiphilous grasslands of temperate Europe and adjacent regions

Diagnostic species: Abietinella abietina (B), Achillea millefolium aggr., Artemisia absinthium, Bupleurum falcatum aggr., Campanula glomerata aggr., C. rapunculoides, C. stevenii, Cirsium leucocephalum, Dactylis glomerata, Galium verum, Koeleria albovii, Leontodon hispidus, Linum nervosum, L. tenuifolium, Lotus corniculatus, Onobrychis transcaucasica, Origanum vulgare, Phleum phleoides, Pimpinella saxifraga aggr., Plantago atrata, Poa pratensis aggr., Polygala anatolica, Polygonum cognatum, Potentilla recta aggr., Scabiosa bipinnata, Securigera varia, Stachys macrostachys, Taraxacum sect. Taraxacum, Thalictrum minus, Trifolium alpestre, T. ambiguum, T. trichocephalum, Trisetum flavescens.

Ecology and distribution: Within Armenia, this class comprises meso-xeric grasslands and mountain steppes at higher elevations. We distinguish two orders representing different altitudinal belts.

Order 2.1: Plantagini atratae-Bromopsietalia variegatae – High-mountain meso-xeric grasslands of the Caucasus

Diagnostic species: Achillea millefolium aggr., Ajuga orientalis, Alchemilla sericea, Arenaria blepharophylla aggr., A. gypsophiloides, Aster alpinus, Brachypodium pinnatum, Bromopsis variegata, Campanula collina, C. stevenii, Cirsium leucocephalum, Festuca ovina aggr., Schedonorus pratensis, Festuca rubra aggr., Filipendula vulgaris, Gagea glacialis, Galium cordatum, Gentiana septemfida, Huynhia pulchra, Koeleria albovii, Lathyrus digitatus, Lomelosia caucasica, Lotus corniculatus, Luzula multiflora, Medicago papillosa, Muscari armeniacum, Myosotis alpestris, Ornithogalum sigmoideum, Papaver orientale, Pedicularis condensata, Phleum alpinum, Pilosella officinarum aggr., Pimpinella saxifraga aggr., Plantago atrata, Poa pratensis aggr., Pohlia nutans (B), Polygonum cognatum, Potentilla argentea, Psephellus xanthocephalus, Pseudoleskella tectorum (B), Pulsatilla albana, Ranunculus caucasicus, Rumex acetosella, Senecio pseudo-orientalis, Stachys macrantha, Stipa tirsa, Taraxacum sect. Taraxacum, Thymus collinus, Tortula acaulon (B), Trifolium ambiguum, T. spadiceum, T. trichocephalum, Verbascum speciosum, Veronica denudata, V. gentianoides.

Ecology and distribution: Communities of this order occupy the highest sampled elevations in Armenia: upper subalpine and lower alpine belts. They form a particular unit recognized in the dominant approach typology: mountain meadow steppes. Beyond this elevation belt, they are replaced by the alpine grasslands which possibly belong to the class Juncetea trifidi Hadač in Klika et Hadač 1944 (Festucetalia woronowii Tsepkova 1987).

Alliance 2.1.1: Artemisio chamaemelifoliae-Bromopsion variegatae – Caucasian subalpine and lower-alpine meso-xeric grasslands

Diagnostic species: Achillea millefolium aggr., Alchemilla sericea, Arenaria gypsophiloides, Bromopsis variegata, Campanula collina, C. stevenii, Festuca ovina aggr., F. rubra aggr., Huynhia pulchra, Koeleria albovii, Lathyrus digitatus, Lomelosia caucasica, Lotus corniculatus, Myosotis alpestris, Plantago atrata, Polygonum cognatum, Potentilla argentea, Ranunculus caucasicus, Taraxacum sect. Taraxacum, Trifolium ambiguum, T. trichocephalum, Veronica denudata, V. gentianoides.

Ecology and distribution: This unit was described from the Main Range of the North Caucasus (Vynokurov et al. 2021) in the elevations of 1,800–2,200 m a.s.l. In Armenia, it occurs mainly higher than 2,000 m a.s.l., and shares multiple species with the Northern Caucasus unit. Thus, we are classifying mountain meadow steppes of Armenia within the same alliance. Here we distinguish one association and one informal community within it.

2.1.1.1: Ranunculo caucasici-Bromopsietum variegatae (Figure 8A)

Diagnostic species: Alchemilla sericea, Arenaria blepharophylla aggr., Artemisia chamaemelifolia, Aster alpinus, Avenula pubescens, Brachypodium pinnatum, Bromopsis variegata, Campanula collina, C. stevenii, Carex caryophyllea, Cirsium leucocephalum, Schedonorus pratensis, Galium cordatum, Huynhia pulchra, Lomelosia caucasica, Luzula multiflora, Medicago papillosa, Muscari armeniacum, Myosotis alpestris, Pedicularis condensata, Phascum cuspidatum (B), Phleum alpinum, Pilosella officinarum aggr., Pimpinella saxifraga aggr., Plantago atrata, Polygonum cognatum, Psephellus xanthocephalus, Pulsatilla albana, Ranunculus caucasicus, Rumex acetosella, Stachys macrantha, Stipa tirsa, Tragopogon graminifolius, Trifolium trichocephalum, Veronica gentianoides.

Structure, ecology and distribution: We sampled this vegetation type at the steep north-facing slopes at elevations around 2,100 m, mainly in the Shirak province (vicinities of Amasia and Zorakert), and also in Gegharkunik province (Ardanish). The localities were characterised by a high mean annual precipitation (around 700–900 mm). The soil reaction was slightly acidic (mean pH: 6.5). The association differed by high species richness and the highest participation of Caucasian species, e.g. Dianthus cretaceus, Lomelosia caucasica, Stachys macrantha, and Trifolium trichocephalum, among all studied communities. Graminoids were dominant, particularly Brachypodium pinnatum, Bromopsis variegata, Carex humilis, and Phleum alpinum.

2.1.1.2: Tragopogon reticulatus-Astracantha aurea community (Figure 8B)

Diagnostic species: Arenaria dianthoides, A. gypsophiloides, Astracantha aurea, Campanula stevenii, Elytrigia repens, Gagea glacialis, Koeleria albovii, Lathyrus digitatus, Papaver orientale, Plantago atrata, Senecio pseudo-orientalis, Tragopogon reticulatus, Trifolium ambiguum, T. spadiceum, Trisetum flavescens, Verbascum speciosum.

Structure, ecology and distribution: We sampled this community mainly in the Gegharkunik province (Selim pass), and also in the Aragatsotn province (near the fortress of Amberd). Most of the localities were situated at 2,300–2,400 m a.s.l. and represented the highest elevations among all studied sites. The soil reaction was slightly acidic. These communities are characterised by low species richness with a high participation of Transcaucasian and Caucasian species, e.g. Arenaria dianthoides, Astracantha aurea, Koeleria albovii. Festuca ovina aggr. and Plantago atrata were the dominant species.

Order 2.2: Onobrychido transcaucasicae-Stipetalia pulcherrimae – Transcaucasian mountain steppes

Diagnostic species: Artemisia absinthium, Bupleurum falcatum aggr., Campanula glomerata aggr., C. rapunculoides, Cerinthe minor, Dactylis glomerata, Euphrasia pectinata, Galium verum, Globularia trichosantha, Helictochloa armeniaca, Hypericum perforatum, Klasea radiata, Linum nervosum, L. tenuifolium, Lotus corniculatus, Nepeta nuda, Onobrychis transcaucasica, Origanum vulgare, Phlomis tuberosa, Polygala anatolica, Rosa spinosissima, Salvia verticillata, Scabiosa bipinnata, Securigera varia, Stachys macrostachys, S. recta, Stipa pennata, S. pulcherrima, Teucrium chamaedrys, Thalictrum minus, Vicia canescens subsp. variegata, Viola ambigua.

Ecology and distribution: Mountain steppes in the Transcaucasus form a distinct altitudinal belt above highland xerophyte vegetation (Cousinio brachypterae-Stipetalia arabicae) and below mountain meadow steppes (Plantagini atratae-Bromopsietalia variegatae). In our dataset, the order is represented by one alliance.

Alliance 2.2.1: Onobrychido transcaucasicae-Stipion pulcherrimae – Transcaucasian mountain steppes

Diagnostic species: Campanula rapunculoides, Cerinthe minor, Dactylis glomerata, Linum nervosum, L. tenuifolium, Onobrychis transcaucasica, Origanum vulgare, Scabiosa bipinnata, Securigera varia, Stachys macrostachys, S. recta.

Ecology and distribution: Despite its high floristic heterogeneity, we unite all mountain steppes into one alliance. We distinguish two informal communities and two associations.

2.2.1.1: Trisetum flavescens-Stachys macrostachys community (Figure 8C)

Diagnostic species: Arenaria graminea, Artemisia absinthium, Chaerophyllum roseum, Gagea caroli-kochii, Silene cephalantha, Stachys macrostachys, Trisetum flavescens, Verbascum cheiranthifolium.

Structure, ecology and distribution: We sampled this vegetation type at the elevations 1,950–2,300 m a.s.l. in Aragatsotn (near Amberd fortress), Gegharkunik (Selim pass, Shorja) and Shirak (vicinity of Amasia) provinces. These communities develop on soils with high humus content. The herb layer is relatively dense with dominance of grasses (Elytrigia intermedia aggr., Phleum nodosum, Poa pratensis aggr., Trisetum flavescens) and legumes (Securigera varia, Trifolium alpestre, Vicia tenuifolia subsp. variabilis, V. canescens subsp. variegata).

2.2.1.2: Onobrychis transcaucasica-Vicia canescens subsp. variegata community (Figure 8D)

Diagnostic species: Arabis hirsuta, Campanula bononiensis, Campyliadelphus chrysophyllus (B), Chaerophyllum aureum, Daphne oleoides subsp. kurdica, Helictochloa armeniaca, Klasea radiata, Lathyrus latifolius, Linum nervosum, Nepeta nuda, Onobrychis transcaucasica, Origanum vulgare, Phlomis tuberosa, Primula veris subsp. macrocalyx, Rhinanthus subulatus, Salvia nemorosa, Securigera varia, Seseli libanotis, Stachys macrostachys, Stipa zalesskii subsp. canescens, Thalictrum minus, Valeriana officinalis aggr., Vicia canescens subsp. variegata, Viola ambigua.

Structure, ecology and distribution: We recorded relevés of this community only in the Vayots Dzor province, at north-facing slopes (inclination 10–40°) in the vicinity of Gnishik and between Khachik and Areni. Communities differed by closed herb layer and high litter cover. The species composition is characterised by a high participation of forbs with European distribution, such as Campanula bononiensis, Klasea radiata, and Securigera varia. The dominant species is Vicia canescens subsp. variegata.

2.2.1.3: Globulario trichosanthae-Stipetum pulcherrimae (Figure 8E)

Diagnostic species: central association (no diagnostic species)

Structure, ecology and distribution: We sampled this vegetation type at elevations around 1,900–2,200 m a.s.l. in the provinces of Gegharkunik (Ardanish and vicinity of the town of Sevan), Shirak (Jajur pass) and Vayots Dzor (vicinities of Gnishik, Khachik and Areni). In the species composition, prevailing groups of species were European (Potentilla recta aggr., Stachys recta, Stipa pulcherrima) and Irano-Turanian (Eryngium billardierei, Onobrychis michauxii, Thymus kotschyanus, Ziziphora clinopodioides), followed by Caucasian endemics (Astragalus cancellatus, Centaurea pseudoscabiosa, Scabiosa bipinnata). The dominant species of the association was Stipa pulcherrima.

2.2.1.4: Seslerio phleoidis-Onobrychidetum cornutae (Figure 8F)

Diagnostic species: Abietinella abietina (B), Adonis volgensis, Androsace chamaejasme, Asperula affinis, Asphodeline taurica, Briza media, Campanula rapunculoides, C. sibirica, Coronilla coronata, Euphorbia esula aggr., Euphrasia pectinata, Fritillaria caucasica, Homalothecium lutescens (B), Hypnum cupressiforme (B), Leucanthemum vulgare, Linum tenuifolium, Pimpinella saxifraga aggr., Pinus sylvestris, Pontechium maculatum, Psephellus karabaghensis, Sesleria phleoides, Spiraea crenata, Thalictrum foetidum, Viola alba.

Structure, ecology and distribution: We sampled this association at elevations 1,940–2,070 m a.s.l. in Gegharkunik (Ardanish, Shorja, vicinity of the town of Sevan) and Shirak (Jajur pass) provinces. The association differed by the highest mean total species richness and richness of bryophytes across all studied communities. The species composition is represented by a high participation of European species of grasses and forbs, such as Briza media, Campanula rapunculoides, Galium verum, Pimpinella saxifraga aggr., and Stachys recta. Carex humilis, Onobrychis cornuta and Teucrium chamaedrys are the dominant species.

The type of the class Astragalo-Brometea, namely the order Astragalo-Brometalia, along with other orders traditionally associated with it (Drabo-Androsacetalia, Hyperico linarioidis-Thymetalia scorpilii, Onobrychido armenae-Thymetalia leucostomi), were grouped together as “group A” in the Twinspan analysis (Figure 2). This suggests that these clusters collectively represent the vegetation of the class Astragalo-Brometea. Furthermore, although cluster 7 forms a separate group C, it is positioned closer to group A on the DCA ordination. Hence, the order Festuco oreophilae-Veronicetalia orientalis may also be considered part of the class Astragalo-Brometea, as originally described (Hamzaoğlu 2006). However, more comprehensive data analysis would be needed to clarify if Festuco oreophilae-Veronicetalia orientalis belongs to Astragalo-Brometea or should form a distinct class uniting Eastern Anatolian tragacanth communities.

Groups B and E comprised plots from meso-xeric, xeric, and rocky grasslands that can be categorised as belonging to the class Festuco-Brometea. Whereas plots within group E were previously assigned to order-level units (Asphodelino tauricae-Euphorbietalia petrophilae, Festucetalia valesiacae, Brachypodietalia pinnati), group B did not have any assignments to any syntaxonomic order. Considering the clear separation between group B and group E at the very basis of the dendrogram, and the fact that group B is, in contrast to group E, positioned above the Y-axis in the DCA ordination (Figure 3), we propose establishing a distinct order-level unit for group B. This unit would encompass high-mountain xero-mesic meadow-steppe grassland communities found in the Caucasus, Eastern Anatolia, and Northern Iran, and we suggest naming it “Plantagini atratae-Bromopsietalia variegatae” (see below).

Group D encompasses the driest communities sampled in Armenia, particularly cluster 8. The species present in this group are predominantly distributed in the Irano-Turanian region, such as Artemisia fragrans, Eryngium billardierei, Noaea mucronata, Stipa arabica, S. holosericea, and others. This species composition suggests that similar vegetation types may also exist in other regions of Western Asia. Since there is no suitable class-level unit available, we propose that in the future, a new class should be established. To do so a comprehensive comparison involving more data from the surrounding regions would be needed. For now, in this paper, we refer to this unit as “Ziziphora tenuior-Stipa arabica grasslands”, combining the dry grassland, semi-desert and xeric thorn-cushion vegetation of Western Asia.

To summarise, we can classify all the vegetation plots of the bigger dataset into three classes: Astragalo-Brometea (groups A and C), Festuco-Brometea (groups B and E), and a tentative new class, “Ziziphora tenuior-Stipa arabica grasslands”. This was well supported by the DCA ordination (Figure 3), in which the plots categorised as Festuco-Brometea were positioned to the right of the Y-axis, while Astragalo-Brometea was positioned on the bottom-left corner of the plot, and “Ziziphora tenuior-Stipa arabica grasslands” on the upper-right corner. The chorological analysis (Figure 12) suggests that the “Ziziphora tenuior-Stipa arabica grasslands” are an Irano-Turanian vegetation type and may be found in other parts of this region, especially in Western Asia.

We can identify two distinct vegetation classes in Armenia: Festuco-Brometea and a novel class meant to encompass drier grasslands and thorn-cushion communities found at lower elevations. This finding aligns well with the outcomes of the TWINSPAN analysis of the Armenian plots (Figure 4).

Cluster X in the TWINSPAN dendrogram corresponds to scree vegetation that currently cannot be assigned to any existing vegetation class. It appears to be similar to the Thlaspietea rotundifolii Br.-Bl. 1948 from temperate Europe or Drypidetea spinosae Quézel 1964 from the Mediterranean. In the North Caucasus, a class of high-altitude scree vegetation on siliceous outcrops, Lamio tomentosi-Chaerophylletea humilis Belonovskaya et al. 2014, exists. However, the latter mainly consists of subnival belt vegetation with a completely different floristic composition. Therefore, we cannot currently assign the aforementioned Armenian scree community to any existing class and leave it unassigned.

The remaining clusters in the left part of the dendrogram (clusters 1.1.1.1–1.1.3.2 in Figure 4) can be linked to the proposed new class, informally named ‘Ziziphora tenuior-Stipa arabica grasslands’. The clusters on the right side of the dendrogram (clusters 2.1.1.1–2.2.1.4) are clearly associated with the class Festuco-Brometea.

Further examination of the drier part of Armenian plots (clusters 1.1.1.1–1.1.3.2 on the dendrogram, Figure 4) revealed three distinct units corresponding to alliance-level syntaxa. Cluster 1.1.1.1 represented rocky grasslands, cluster 1.1.1.2 consisted of dry grasslands at higher elevations with Irano-Turanian influences, and cluster 1.1.2.1 was related to stony semi-deserts. Clusters 1.1.3.1 and 1.1.3.2 correspond to ‘highland xerophytic vegetation’ or Minor-Asian thorny-cushion shrubs (as per Makagian 1941). We propose interpreting these units as five associations and communities within three different alliances and one order.

Relevés from clusters 2.1.1.1–2.1.1.2 were previously categorized under group B in the earlier section (broad-scale comparison), together with plots from the North Caucasus belonging to the alliance Artemisio chamaemelifoliae-Bromopsion variegatae. Given their separation from the other clusters at a high level (Figure 2), we suggest uniting clusters 2.1.1.1–2.1.1.2 into a new order-level unit named Plantagini atratae-Bromopsietalia variegatae (see below). This new order is ecologically similar to the Brachypodietalia pinnati Korneck 1974 nom. cons. propos. (Willner et al. 2019; Dengler and Willner 2023). Both unite meso-xeric grasslands and share several common diagnostic species, such as Brachypodium pinnatum, Filipendula vulgaris, Pimpinella saxifraga aggr., Stipa tirsa, as well as several mesophilic species, including Achillea millefolium aggr., Schedonorus pratensis, Festuca rubra aggr., Lotus corniculatus, and Potentilla argentea. However, the new order is clearly distinguished by the presence of numerous Caucasian endemics and species of Irano-Turanian distribution among the diagnostic species, such as Bromopsis variegata, Campanula collina, Gentiana septemfida, Huynhia pulchra, Koeleria albovii, Psephellus xanthocephalus, Pulsatilla albana, Ranunculus caucasicus, and others. Additionally, this order is distinguished by the presence of high-mountain species of broader distribution, such as Aster alpinus, Phleum alpinum, and Plantago atrata.

Clusters 2.2.1.1–2.2.1.4 corresponded to the so-called mountain steppes, following the classification of Makagian (1941). These clusters are linked to the class Festuco-Brometea within a new order Onobrychido transcaucasicae-Stipetalia pulcherrimae and a new alliance Onobrychido transcaucasicae-Stipion pulcherrimae, which unite the Transcaucasian mountain steppes.

With an average of 46.8 vascular plants in 10 m², the dry grasslands of Armenia were significantly richer than the Palaearctic average of the three relevant ecological-physiognomic vegetation types (A.3 - Xeric grasslands and steppes; B.2 - Meso-xeric grasslands; D.3 - Garrigues and thorn-cushion communities) in the high-quality database GrassPlot (v.2.10; https://edgg.org/databases/GrasslandDiversityExplorer; see Biurrun et al. 2021) with 35.8 species. By contrast, bryophytes (0.4 vs. 3.0 species) and lichens (0.1 vs. 0.9 species) were clearly poorer than in dry grasslands elsewhere. The difference is even more pronounced when comparing with the dry grasslands of the central valleys of the Alps, where Bergauer et al. (2022) reported averages of 35.1 vascular plant, 3.9 bryophyte and 1.9 lichen species in the same plot size. For the inneralpine dry grasslands of Austria, Magnes et al. (2021) reported even a slightly lower richness of vascular plants (34.2), but a slightly higher of bryophytes and lichens combined (6.1) than in Switzerland. Thus, it is astonishing why the Armenian dry grasslands deviate so strongly by higher small-scale vascular plant richness and lower bryophyte and lichen richness not only from the Palaearctic average but also from the dry grasslands in the central valleys of the Alps that should share similarities with the central valleys of the Caucasus. One explanation for the higher density of species in Armenia and also in the Italian Apennines (49.5 species in 10 m², Filibeck et al. 2018) could lie in the glaciations (Bergauer et al. 2022). While during the Pleistocene the valleys of the Alps were almost entirely filled by glaciers, in the case of the Caucasus and the Apennines only local glaciers on mountain tops occurred (Aseev et al. 1984), which could mean that the vascular plant flora of the Alpine valleys is simply so impoverished that no more species for higher plot-scale richness are available. By contrast, bryophytes and lichens should be much less affected by the glaciations as their spores are so much lighter than seeds of vascular plants, that they hardly suffer from dispersal limitations. One potential explanation for the very low richness of non-vascular taxa in Armenia could be that the majority of bryophyte and lichen taxa is adapted to cooler climate, while the mean annual temperature in Armenia is higher than in the Alps. However, both potential explanations are not much more than speculations at present. Moreover, while essentially in any region where EDGG studied dry grasslands before, the meso-xeric types were much richer at plot scale than the xeric types (Dengler et al. 2012; Magnes et al. 2021), we did not find a significant richness difference between our more xeric class 1 (Ziziphora tenuior-Stipa arabica grasslands) and the less xeric class 2 (Festuco-Brometea) (Figure 13). All these unexpected patterns and our ad hoc explanations call to be tested with a comprehensive dataset that contains standardized richness data for dry grasslands in many different situations in the Palaearctic, such as the GrassPlot database (Dengler et al. 2018).