The paper represents the results of grass pine forests classification in Dagestan by the Brown-Blanquet method. A number of 68 releves of pine forests (taken from the paper by Abdurakhmanova et al., 2018) were included in two higher categories of vegetation – the boreal forests of the class Vaccinio–Piceetea Br.-Bl. in Br.-Bl. et al. 1939 and the sub-Mediterranean thermophilous forests of the class Erico–Pinetea Horvat 1959 based on the quantitative classification. Comparative syntaxonomic analysis of the Caucasian communities of the Erico–Pinetea class revealed their high level of floristic originality in comparison with similar forests of southern Europe, Western Asia and Crimea. This corresponds to the unique bioclimatic conditions of Dagestan located on the territory with a clear effect of «rain shadow» from the high mountain ranges of the Greater Caucasus stretching on the way of the western Atlantic moist air masses that result in the high climate continentality. These essential ecological and floristic peculiarities of the grass pine forests of the Eastern Caucasus provided a basis for the description of a new order — Alchemillo sericaceae–Pinetalia sylvestris ord. nova hoc loco representing the extreme eastern part of the Erico–Pinetea class range. The diagnostic species group of the order includes dominantly Eastern-Euxinian, Caucasian endemics and Eurasian xerophilous species: Juniperus oblonga, Alchemilla sericata, Galium valantioides, Peucedanum ruthenicum, Thalictrum foetidum, Rosa elasmacantha, Filipendula vulgaris, Koeleria cristata, as well as diagnostic species of subordinated alliances. The order includes two alliances demonstrating the ecological and floristic differences of Dagestan pine forests due to the thermic factor. The alliance Bupleuro polyphylli–Pinion sylvestris all. nova hoc loco (holotypus of the order) includes grass pine forests with predominance of thermophilous floristic elements. Differential species of the alliance are Astrantia major, Valeriana alliariifolia, Polygonatum verticillatum, Pyrethrum coccineum, Psephellus daghestanicus, Galium rubioides, Calamagrostis arundinacea, Rubus saxatilis, Brachypodium pinnatum, Fragaria vesca, Fragaria viridis, Primula macrocalyx, Anthriscus sylvestris, Amoria ambigua, Bupleurum polyphyllum, Hylocomium splendens, Pleurozium schreberi, Dicranum scoparium, Rhytidiadelphus triquetrus, Rhodobryum roseum, Climacium dendroides, Abietinella abietina, Plagiomnium cuspidatum, Betula litwinowii, B. pendula. Three associations and two non-rank communities were included in the alliance (Carici albae–Pinetum sylvestris Ermakov, Abdurakhmanova, Potapenko 2019 — holotypus of the alliance, Ranunculo caucasicae–Pinetum sylvestris ass. nova hoc loco, Viburno lanatae–Pinetum sylvestris Ermakov, Abdurakhmanova, Potapenko 2019, community Stachys atherocalyx–Pinus sylvestris, community Centaurea phrygia–Pinus sylvestris). The alliance Onobrichido cornutae–Pinion sylvestris all. nova hoc loco includes unique cryophilous pine forests with predominance of the cushion plants in the gound layer and numerous constant species of Caucasian cryophilous and xerophilous endemics. Diagnostic species of the alliance are Onobrychis cornuta, Festuca woronowii, Gypsophila tenuifolia, Salvia canescens, Rosa elasmacantha, Androsace koso-poljanskii, Galium brachyphyllum, Thymus daghestanicus, Asperula alpina, Anthemis dumetorum, Scutellaria oreophila, Satureja subdentata, Potentilla recta, Teucrium polium, Euphorbia virgate, Scabiosa gumbetica, Astragalus alexandri, A. fissuralis, Seseli alexeenkoi, Pseudomuscari pallens, Rhamnus pallasii, Vincetoxicum funebre, Jurinea ruprechtii, Helianthemum dagestanicum, Stipa caucasica, Centaurea edmondii, Selaginella helvetica, Scorzonera filifolia, Dracocephalum austriacum, Viola somchetica, Oxytropis lanata. At present the alliance is represented by a single association – the Onobrichido cornutae–Pinetum sylvestris ass. nova hoc loco. The results of the classification have demonstrated a significant level of originality of the Caucasian grass pine forests and a high floristic status of the Caucasus as a one of the important centers of modern phytodiversity.
To the problem of syntaxonomy of pine forests (Pinus sylvestris var. hamata) with the participation of boreal floristic elements in Dagestan (North Caucasus)
