Classification of beech (Fagus orientalis) forests of the Western Caucasus

Abstract

The classification of oriental-beech (Fagus orientalis) forests of the Western Caucasus was developed on the basis of quantitative analysis (Ward’s method, Euclidian distance) of 200 relevés (Fig. 2) and comparative syntaxonomic analysis. All Caucasian beech forests were attributed to the class Carpino–Fagetea sylvaticae Jakucs ex Passarge 1968 and Euxine order Rhododendro pontici–Fagetalia orientalis Passarge 1981. The associations of floristically poor beech forests occurring on the acidic bedrocks were included in the alliance Fagion orientalis Soó 1964. These are Orobo–Fagetum orientalis Passarge 1981, Dentario–Fagetum orientalis Passarge 1981, Polysticho–Fagetum orientalis Passarge 1981, Rhododendro pontici–Fagetum orientalis Stefanov ex Tzonev et al. 2006 (syn. Rhododendro pontici–Fagetum orientalis Frantsuzov 2006), Rusco colchici–Castaneetum sativae Novák et al. 2019 and new association Rhododendro lutei–Fagetum orientalis Ermakov ass. nov. (diagnostic species — Rhododendron luteum, Cicerbita petiolata, Hedera colchica, Ilex colchica, Oreopteris limbrosperma, Vaccinium arctostaphylos, Viburnum orientale). Nomenclature type (holotypus) of the Rhododendro lutei–Fagetum orientalis Ermakov ass. nov. is relevé 14, Table 1 (field relevé nr. — 129NE19, Abkhasia Republic, the upper part of the Pskhu River basin, aspect — SWW, slope — 27°, altitude — 1645 m, cover of tree layer — 70 %, cover of shrub layer — 60 %, cover of herb layer — 12 %, coordinates: 43.4299° N, 40.8661° E, size of plot — 100 m2, Date: 28.07.2019, Authors: N. B. Ermakov and V. D. Leiba). The alliance Thlaspio macrophylli–Fagion orientalis Ermakov all. nov. includes rich in species beech forests growing preliminarily on calcareous bedrocks in ultra-humid climate of the Western Caucasus (Colchis, Abkhasia). They occupy mountain slopes of different aspects at altitudes of 150–1800 m. Diagnostic species of the alliance are Acer laetum, A. pseudoplatanus, Aristolochia iberica, Asarum intermedium, Dryopteris caucasica, Galeobdolon luteum, Geranium gracile, Hedera colchica, Phyllitis scolopendrium, Polystichum aculeatum, Potentilla micrantha, Sambucus nigra, Symphytum grandiflorum, Thlaspi macrophyllum, Tilia begoniifolia, Ulmus glabra, Vicia crocea. Nomenclature type (holotypus) of the Thlaspio macrophylli–Fagion orientalis is the association Thlaspio macrophylli–Fagetum orientalis Ermakov ass. nov. (described in this paper) — relevés 1–43 in Table 2; syntaxa 1–4 in Table 3. Diagnostic species of the association are the same as for the alliance Thlaspio macrophylli–Fagion orientalis. Nomenclature type (holotypus) of the Thlaspio macrophylli–Fagetum orientalis Ermakov ass. nov. is relevé 12 in Table 2 (field relevé nr. — 103NE19, Abkhasia Republic, near Pskhu village, 2 km S, aspect — N, slope — 12°, altitude — 775 m, cover of tree layer — 60 %, cover of shrub layer — 20 %, cover of herb layer — 65 %, coordinates: 43.3614° N, 40.8035° E, plot size — 100 m2, Date: 26.07.2019, Authors: N. B. Ermakov and V. D. Leiba). This association represents beech forests occupying steep and moderately steep (15–40°) mountain slopes of western, eastern and partly southern aspects at altitudes 1690–1800 m. The association Thlaspio macrophylli–Fagetum orientalis includes four variants — var. typica, var. Asarum intermedium, var. Hypericum xylosteifolium, var. Polystichum setiferum. The association Senecioni jacquiniani–Fagetum orientalis Ermakov ass. nov. includes beech forests occurring in the upper part of forest belt in the Gagrskiy Ridge at altitudes of 1100–1600 m. Diagnostic species: Calamintha grandiflora, Campanula rapunculoides, Fragaria vesca, Hordelymus europaeus, Polygonatum glaberrimum, Senecio jacquinianus, Solidago virgaurea). Nomenclature type (holotypus) is relevé 49 in table 2 (field relevé nr. — 22NE20, Abkhasia Republic, Gagrskiy Ridge, Momzyshkha mountain, middle part, aspect — W, slope — 15°, altitude — 1125 m, cover of tree layer — 60 %, cover of shrub layer — 20 %, cover of herb layer — 70 %, coordinates: 43.2857° N, 40.3209° E, plot size — 100 m2, Date: 24.08.2020, Authors: N. B. Ermakov and V. D. Leiba). The alliance Thlaspio macrophylli–Fagion orientalis includes also the association Sambuco nigrae–Fagetum orientalis Frantsuzov 2006 from the North-Western Caucasus. The alliance Acero heldreichii–Fagion orientalis Ermakov all. nov. represents the beech forests occurring in the upper part of the forest and subalpine belts of the Caucasus on acidic and calcareous bedrocks at altitudes of 1600–1850 m. Diagnostic species of the alliance are subalpine species (including a large number of the Caucasian endemic tall-forb plants): Acer heldreichii subsp. trautvetteri, Abies nordmanniana, Adenostyles platyphylloides, Aconitum orientale, Agasyllis latifolia, Astrantia major, Asyneuma campanuloides, Calamagrostis arundinacea, Cicerbita petiolata, C. pontica, Dolichorrhiza correvoniana, Dryopteris caucasica, Euphorbia macroceras, Gentiana schistocalyx, Kemulariella caucasica, Lonicera orientalis, Petasites albus, Polygonatum verticillatum, Ptarmica biserrata, Ranunculus cappadocicus, Solidago virgaurea, Valeriana tiliifolia, Woronowia speciosa. Nomenclature type (holotypus) of this alliance is the association Acero heldreichii–Fagetum orientalis Ermakov ass. nov. (described in this paper) — relevés 43–59 in Table 1; syntaxa 19–20 in Table 3. Nomenclature type (holotypus) of the association Acero heldreichii–Fagetum orientalis Ermakov ass. nov. is relevé 54 in Table 1 (field relevé nr. — 47NE20, Abkhasia Republic, Gagrskiy Ridge, Momzyshkha mountain, upper part, aspect — W, slope — 30°, altitude — 1740 m, cover of tree layer — 65 %, cover of shrub layer — 18 %, cover of herb layer — 60 %, coordinates: 43.3138° N, 40.3469° E, plot size — 100 m2, Date: 28.08.2020, Authors: N. B. Ermakov and V. D. Leiba). This association occurs in the upper part of the forest and subalpine belts of the Gagrskiy Ridge (Abkhasia Republic) at altitudes of 1690–1800 m. It includes 2 subassociations — A. t.–F. o. typicum Ermakov subass. nov. and A. t.–F. o. vaccinietosum arctoctaphyli Ermakov subass. nov. At present the alliance Acero heldreichii–Fagion orientalis includes also 3 associations described by Passarge (1980) from the Central Caucasus — Petasito–Fagetum orientalis Passarge 1981, Veratro–Fagetum orientalis Passarge 1981 and Pyrolo–Fagetum orientalis Passarge 1981.