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Relict vegetation of water-splashed petrifying rocks with calcareous tufa formation dominated by the fern Adiantum capillus-veneris and wetland bryophytes (phytosociological class Adiantetea) was investigated in Georgia, Caucasus biodiversity hotspot. The study brings the first phytosociological data on this scarce community in the Caucasus based on a novel dataset of vegetation plot records. A classification analysis revealed two main vegetation communities. They are represented by the Caucasian community recorded in the Mtkvari River valley inside the Tbilisi city (E Georgia) and the Colchic community developed under the humid, warm-temperate climate of Colchis (W Georgia), one of the key refugia of Tertiary flora across W Eurasia. To compare newly recorded vegetation types and so far described associations of the Adiantetea class, we used a broader dataset of the analogous communities reported from Europe and surroundings. It associated the Caucasian community with the pan-Mediterranean association Eucladio-Adiantetum. It was characterized by subhalophytes (e.g. Samolus valerandi), Eucladium verticillatum as a dominant bryophyte, and the absence of relict or endemic vascular plant species. The Colchic community represented a previously undescribed community. Therefore, we designated a new association Saxifrago cymbalariae-Adiantetum capilli-veneris delineated by the characteristic species of the Colchic-Caucasian territory (e.g. Hedera colchica, Saxifraga cymbalaria) and Palustriella commutata as the dominant bryophyte. Both associations belong to the Mediterranean-Atlantic alliance Adiantion. Described communities require conservation attention for their rarity, refugial character and presence of relict and endemic species. Modifications of the hydrological regime and construction activities are among their most important potential threats. [ABSTRACT FROM AUTHOR]

The Caucasus Region belongs among the most remarkable biodiversity hotspots globally. Local mountain floodplain forests represent highly endangered ecosystems and possess the status of protective forests. However, they have not been extensively phytosociologically assessed using Braun-Blanquet methods to date. Here, we present a novel dataset of vegetation plots recorded in two remarkable areas of forest plant diversity in this region. They were Enguri (Black Sea watershed) and Aragvi (Caspian Sea watershed) River basins in the Western and Eastern Greater Caucasus, respectively. Based on 49 relevés, sampled on a broad elevation gradient (980-1830 m), we distinguished three vegetation types using unsupervised classification. Main gradients in their species composition reflect biogeographical and climatic differences. Alnus incana dominated two types. The Enguri type (Brunnero macrophyllae-Alnetum incanae) was characterized by numerous species typical of the western part of the Greater Caucasus, including tall forbs and mountain species. The Aragvi type (Veronico filiformis-Alnetum incanae) showed a diagnostic combination of common Caucasian species and relatively thermophilous forest species. The subdivision of this unit included three subtypes according to grazing intensity. The last type (Sedo stoloniferi-Alnetum barbatae) was significant by a putative Tertiary relict Alnus glutinosa subsp. barbata as a canopy dominant. It occupied lower elevations of the Enguri Region, significantly influenced by the nearby Colchic Region. To provide a regional context of the sampled vegetation, we compiled an expanded dataset of alluvial alder forests from the Caucasus and its surroundings. Their joint classification highlighted the uniqueness of the recorded communities with A. incana and clearly distinguished them from the Euxinian alliance Alnion barbatae delimited by relict species typical of the Colchic refugium (e.g. Diospyros lotus, Pterocarya fraxinifolia). A comparison of the Caucasian A. incana forests with the alluvial forests of the boreonemoral alliance Alnion incanae supported the individuality of the Caucasian stands in terms of floristic composition and allowed us to describe them as a new alliance (Veronico filiformis-Alnion incanae all. nova). It is characterized by the dominance of A. incana accompanied by numerous geographically restricted species (e.g. Senecio propinquus, Symphytum asperum) coupled with boreo-montane forest species (e.g. Oxalis acetosella, Polygonatum verticillatum). Caucasian alluvial forests face many ongoing threats, including constructing of new water reservoirs and hydropower plants, overgrazing and illegal cutting. [ABSTRACT FROM AUTHOR]

The Caucasus harbours unique forest vegetation so far only little studied using the Braun-Blanquet approach. This study is mostly based on a dataset (N = 110) of original phytosociological relevés of oak-hornbeam and ravine forests in the Eastern Greater Caucasus, Georgia. Their unsupervised classification produced seven communities. Five belong to oak-hornbeam forests (order Lathyro-Carpinetalia caucasicae). Of the zonal Caucasian alliance Crataego-Carpinion, the association Corno australis-Carpinetum inhabits valleys of the Greater Caucasus, and Clinopodio umbrosi-Carpinetum is confined to the warm Eastern Greater Caucasus promontories. The association Astrantio maximae-Carpinetum of the alliance Astrantio-Carpinion represents distinctive Caucasian montaneoak-hornbeam forests. The other two communities, documented by a few relevés, were described at the community level only. Within ravine forests (order Aceretalia pseudoplatani), we introduce a new Caucasian alliance Pachyphragmo macrophyllae-Tilion begoniifoliae with two associations. Valeriano tiliifoliae-Ulmetum glabrae comprises Caucasian montane ravine forests whereas Hedero pastuchovii-Aceretum velutini inhabits the foothills of the Eastern Greater Caucasian. To provide a broader context of the recognized communities, an expanded dataset (N = 231) of original relevés and previously published relevés of Georgian deciduous forests was analysed. It indicated a major turnover in species composition following biogeographical patterns presumably driven by macroclimate and vegetation history. [ABSTRACT FROM AUTHOR]

Aim: The aim of the paper is to describe species composition, ecology and syntaxonomy of unique mesophilous forests in Georgian Colchis in the context of the Euxinian forests. Location: SW Georgia, western part of the Caucasus Region, slopes of the Lesser Caucasus (80-990 m). Methods: Forest vegetation was sampled following the Braun-Blanquet approach and basic environmental characteristics were recorded for each relevé (n = 53). The dataset was clustered using modified TWINSPAN and diagnostic species for each cluster were defined by phi fidelity index. Links between the species composition of vegetation and environmental factors were analysed by detrended correspondence analysis. Numerical comparison of the distinguished clusters with previously published associations from northern Turkey was carried out (expanded dataset, n = 173). Results: Among the new relevés, we distinguished three vegetation types subsequently described as new associations: (i) Digitali schischkinii-Carpinetum betuli, chestnut-hornbeam forests of slightly dry sites, with low cover of evergreen shrubs, (ii) Rusco colchici-Castaneetum sativae, chestnut-hornbeam forests with a dense evergreen shrub layer, and (iii) Polysticho woronowii-Ulmetum glabrae, ravine forests with noble hardwood trees and ravine forest specialists. These associations were classified to the alliances of Euxinian forests, the first two to Castaneo-Carpinion and the third to Alnion barbatae. Major turnover in species composition within the dataset followed gradients of rockiness, slope inclination, altitude and mean annual temperature. The analysis of the expanded dataset revealed a decreasing occurrence of Mediterranean species and an increasing number of fern species along an easterly gradient. This change in species composition is likely to be driven by macroclimatic gradients. Conclusions: This paper presents the first numerical comparison of chestnut-hornbeam and ravine forests across central and eastern parts of the Euxinian Province. Our results have highlighted the uniqueness of Georgian Colchic forests, described as new associations, in the context of Euxinian forest vegetation. [ABSTRACT FROM AUTHOR]

River gravel-bar habitats are highly endangered. They are still well-preserved in the Caucasus, but developing conservation strategies is burdened by the lack of data from this region. We studied vegetation and habitat types on gravel bars of 22 rivers in Georgia, including successional stages from open early-successional herbaceous vegetation to scrub. We distinguished five vegetation types based on vegetation physiognomy and β-flexible clustering of species composition, and described them as phytosociological vegetation units: Early-successional herbaceous vegetation at higher elevations was described as the new association Epilobietum colchici and that at lower elevations as the Petrorhagia saxifraga–Crepis foetida community. The grassland dominated by Calamagrostis pseudophragmites and scrub vegetation were assigned to the associations previously described from Central Europe (Tussilagini farfarae-Calamagrostietum pseudophragmitae, Salici purpureae-Myricarietum germanicae and Salici incanae-Hippophaëtum rhamnoidis). We established diagnostic plant species for each type using the fidelity calculation and related these types to environmental variables. We further compared them with the previously published data on gravel-bar vegetation from the Russian part of the Caucasus and with European systems of habitat classification. This study demonstrates that vegetation and habitat types occurring in Georgia correspond to those recognized earlier in Europe, and can be easily linked to the European systems of habitat classification. Unlike in other parts of Europe, these habitats are still well-preserved on rivers with natural hydrological dynamics, but they are threatened by plans of dam building and other river regulations. Our study provides baseline data for developing conservation strategies for the Caucasian gravel-bar habitats. [ABSTRACT FROM AUTHOR]

Please be informed that the wrong table was inadvertently published in the following paper [ABSTRACT FROM AUTHOR]