Transcaucasian Vegetation Database – a phytosociological database of the Southern Caucasus

Abstract

The Caucasus is a hotspot of global biodiversity. However, even in the era of big data, this region remains underrepresented in public vegetation-plot databases. The Transcaucasian Vegetation Database (GIVD code AS-00-005) is a novel dataset which primarily aims to compile, store and share vegetation-plot records sampled by the Braun-Blanquet approach and originating from Transcaucasia (the Southern Caucasus), i.e. the countries of Armenia, Azerbaijan and Georgia. The database currently contains 2,882 vegetation plots. The oldest plots originate from 1929, the newest from 2022, and their collection is ongoing. The data include mesophilous forests (phytosociological class Carpino-Fagetea) and various alpine and subalpine communities (e.g. Carici-Kobresietea, Loiseleurio-Vaccinietea) – selected other habitats are also represented. Most of the plots (84%) are georeferenced, 36% with high precision of 25 m or less. The database includes 2,500 taxon names; Asteraceae, Poaceae, Fabaceae and Rosaceae represent the most common families. Vascular plants are recorded in all plots, while data on species composition of bryophytes are available for 11% of plots. The database intends to contribute to the complex biodiversity research of this biologically unique territory. The data might be used in diverse projects in botany, biogeography, ecology and nature protection.

Taxonomic reference : The Plant List (http://www.theplantlist.org/ [Accessed 10 Jan 2023]).

Syntaxonomic reference : Mucina et al. (2016) .

Abbreviations : TVD = Transcaucasian Vegetation Database.

GIVD Fact Sheet: Transcaucasian Vegetation Database

Introduction

The databases collecting, storing and sharing georeferenced vegetation-plot records are among the significant data sources in the ongoing rapid emergence of ecoinformatics. However, the Caucasus is one of the areas of Europe and its adjacent territories still poorly represented in existing vegetation databases (Chytrý et al. 2016; Bruelheide et al. 2019; Preislerová et al. 2022).

The Caucasus is a mountainous region situated in the middle sector of the Alpine–Himalayan orogenic belt, on the borderline of Europe and Asia. The so-called Caucasian isthmus stretches between the Black and Caspian Seas. The area spans a broad elevation gradient from -29 m (Caspian Sea shore) to 5,642 m (Mount Elbrus), making it the broadest in western Eurasia. The region is mainly characterized by rugged topography and offers a wide range of geological bedrock, including limestone karst areas, extensive neovolcanic zones with both extrusive bodies and lava plateaus, clay and saline Tertiary sediments or ophiolite outcrops. The climatic gradients are also significant. In terms of annual precipitation, the highly humid Colchic mountains in western Georgia receive 4,500 mm of precipitation yearly and represent one of the wettest areas in western Eurasia. Contrary, the arid climate of the Azerbaijan lowlands is characterized only by 200 mm per year. Mean annual temperatures in vegetated areas span from -9 °C (Elbrus Mt.) to 14 °C (Black and Caspian Sea coasts). The climatic continentality gradient is also remarkable (Volodicheva 2002; Nakhutsrishvili et al. 2011; Bondyrev et al. 2015). This considerable variety of environmental conditions, the specific history of local biota and its position on a biogeographic crossroad of the Circumboreal and Irano–Turanian Floristic Regions support extraordinarily high biodiversity (Takhtajan 1986; Gegechkori 2020). The Caucasus is listed among the top 34 world biodiversity hotspots, along with the Mediterranean Basin, the only two remaining partly in Europe (Mittermeier et al. 2005). It harbours exceptionally high vascular plant species diversity, one of the highest in certain latitudes (Barthlott et al. 2005). This taxonomic group shows a considerable species endemism rate of ~25% out of 6,400 species in total (Mittermeier et al. 2005; Kier et al. 2009). Moreover, the territory includes two essential Tertiary flora refugia of temperate and subtropic Northern Hemisphere, Colchic in W Georgia and NE Turkey and Hyrcanian in SE Azerbaijan and NW Iran (Milne and Abbott 2002; Nakhutsrishvili et al. 2011, 2015). They harbour numerous ancient relicts, including many evergreen shrubs, and their forests are classified as temperate rainforests (Nakhutsrishvili et al. 2011, 2015; Nakhutsrishvili 2013). Vegetation and habitat richness is, therefore, also comparably high (Nakhutsrishvili 2013; Jiménez‐Alfaro et al. 2014; Fayvush and Aleksanyan 2016).

The Caucasus might be divided according to the main ridge of the Greater Caucasus, which shows a general west–east orientation. The northern slopes of the Greater Caucasus and adjoining hilly and undulated landscape are called Ciscaucasia (or Northern Caucasus). Contrary, Transcaucasia (or the Southern Caucasus) lies southwards from the main ridge. Its vegetation cover is the main subject of the AS-00-005 - Transcaucasian Vegetation Database (TVD) presented here, which is included in the Global Index of Vegetation-Plot Databases (GIVD) and the European Vegetation Archive (EVA; Chytrý et al. 2016).

Transcaucasia, with its unique nature, attracted generations of naturalists. The history of research on local vegetation dates back to the 19^th century, when the German botanist Karl Koch twice visited the Caucasus and Transcaucasia. After his journeys, he published the first map of Caucasian vegetation (Koch 1850; Lack 1978). He was succeeded by the German universal naturalist Gustav Radde and the Russian botanist Jakob Sergejevitsch Medwedew who published a series of articles describing fundamental vegetation characteristics of specific regions of the Southern Caucasus (e.g. Radde 1866; Medwedew 1869). These investigations accelerated in the early decades of the 20^th century when the first pioneering overviews of vegetation formations in specific areas appeared (e.g. Rubel 1914; Troitsky 1930). However, during the century, a vegetation classification approach based on the dominant species strongly prevailed in the region (e.g. Magakyan 1941; Takhtajan 1941; Grossheim 1948; Makhatadze 1958; Prilipko 1970; Gulisashvili et al. 1975) while studies carried out following the protocols of the Braun-Blanquet’s Zürich–Montpellier school were scarce (e.g. Bush and Bush 1936). In the 1980s, many phytosociological studies applying the Braun-Blanquet approach were published, especially those focusing on subalpine and alpine plant communities or forest vegetation of the Greater Caucasus (e.g. Passarge 1981a, 1981b; Guinochet 1984; Bedoshvili 1985). After the dissolution of the Soviet Union in the early 1990s, armed conflicts slowed the research of Caucasian vegetation. Later, the research accelerated again, and many studies focusing mainly on Georgian territory were published, both dominant-based (Nakhutsrishvili 1999, 2013; Huseynova 2021; Ibadullayeva and Huseynova 2021) and Braun-Blanquet-based (e.g. Filibeck et al. 2004; Kaffke 2008). In the last decade, more Braun-Blanquetian studies appeared, both local (e.g. Novák et al. 2020, 2021; Goginashvili et al. 2021) or focusing on large areas or whole national territories (e.g. Jabbarov et al. 2020; Kalníková et al. 2020; Nakhutsrishvili et al. 2022). A field workshop by the Eurasian Dry Grassland Group in Armenia in 2019 (Aleksanyan et al. 2020; Biurrun et al. 2021) brought a considerable step forward in the knowledge of the Transcaucasian grassland vegetation. The first modern comprehensive habitat overviews of the Transcaucasian countries were published after 2010, serving as an essential reference for vegetation research (e.g. Akhalkatsi and Tarkhnishvili 2012; Fayvush and Aleksanyan 2016). Despite this persistent effort, Transcaucasian vegetation diversity belongs among the less phytosociologically explored within Europe and adjacent areas (Preislerová et al. 2022). Existing vegetation-plot databases from Transcaucasia within GIVD (Dengler et al. 2011) primarily focus on relatively small fractions of the region or specific habitats. They correspond to five databases originating from Azerbaijan (EU-AZ-001–005) and storing plots recorded for purposes of specific grants and theses in the 2000s. Additionally, the Caucasus Vegetation Database Georgia (AS-GE-001) includes plots of subalpine and alpine formations in two distinct mountainous areas of Georgia (Bakuriani, Kazbegi). However, these databases are not included among the EVA core databases (Chytrý et al. 2016) and thus accessibility of Caucasian vegetation data for EVA projects has been seriously limited to date. Aiming to fill geographical and ecological gaps in the vegetation-plot records from Transcaucasia, we established a novel database intending to encompass the entire territory and all vegetation types.

Many anthropogenic factors cause the current deterioration of Transcaucasian biodiversity. They include, for instance, extensive legal and illegal logging to obtain firewood or timber, overgrazing of alpine grasslands, environmental pollution, slope erosion, construction activities including building of new water reservoirs, forest fires, outbreaks of tree pathogens and invasions of alien species. Ongoing climate change will presumably bring new threats, including more frequent drought periods, desertification or shifts of the upper treeline (Zazanashvili and Mallon 2009; Akhalkatsi 2015; Slodowicz et al. 2018; Fayvush and Aleksanyan 2020). Within Europe and adjoining areas, Transcaucasian countries are among the states with the highest need for effective nature conservation (Giam et al. 2010).

Data collection

The field data collection started in the summer of 2015; during the first vegetation expedition of the botanists from the Masaryk University (Brno, Czech Republic) to Georgia led by V. K. and P. N. Thenceforth, regular fieldwork with intensive vegetation sampling leading to the Southern Caucasus started. Plots sampled during these expeditions served as a basis for the database. Additionally, we digitized vegetation plots from numerous literature sources, including papers, vegetation overviews and monographs, and unpublished sources (i.e. “grey literature” like project reports and theses). All plots in the database were sampled using the Braun-Blanquet phytosociological approach (Dengler et al. 2008). They are currently stored in the TURBOVEG (version 2.159, Hennekens and Schaminée 2001).

All plots contain information on vascular plant species assemblages. Species covers were visually assessed in percentages or in grades of Braun-Blanquet (Dengler et al. 2008) or specific ad hoc cover scales, depending on their author. A fraction of plots from the aforementioned expeditions also include bryophytes, determined by experienced bryologists (see Acknowledgments). Data on the species composition and covers in the bryophyte layer are additionally available from a few literature sources.

Header data from the original sources accompany the stored plots. As the geographic location is among the principal attributes of the plots, we paid particular attention to their georeferencing (WGS84). Plots with missing coordinates, thus especially those digitized from older literature before the 2000s, were georeferenced with appropriate accuracy, as far as possible, according to their site descriptions. The geographic coordinates’ precision is provided for most georeferenced plots. When achievable, the localization of plots from the literature was additionally consulted with their authors.

Plots from the literature that could be localized only roughly (e.g. region, state) were also digitized as they may serve specific purposes like national vegetation and flora overviews. Further environmental data acquired during the field sampling or digitized from literature include elevation (m a. s. l.), slope inclination (°) and aspect (°). For a high portion of plots from our field research, we measured soil pH in a suspension (2:5) of a soil sample (uppermost 15 cm of soil surface) and deionized water by portable devices (e.g. GMH 3530, Hach HQ40d). The sampling date (at least the year) from the literature was also extracted. Full citations of the source literature of the digitized plots are provided (Suppl. material 1).

Database content

The TVD is the largest vegetation-plot database in the Caucasus in terms of the number of stored plots as well as geographic scope (39°–44°N, 40°–49°E). Currently, the collection encompasses 2,882 plots recorded using the Braun-Blanquet method (Figure 1).

The database comprises unpublished plots from the authors’ field research (30%) and plots (70%) from 45 literature sources. Their header data show various completeness (Figure 2). The oldest plots were sampled in 1929 (Bush and Bush 1936), the newest in 2022 (unpublished to date). Thus, the database covers almost a century of phytosociological research in Transcaucasia. The number of plots per decade steadily increases from the 1990s on (Table 1). The geographic coordinates are available for 84% of plots. The remaining plots (typically ones located at the country level only) were impossible to georeference even in a very rough grid. 36% of plots are precisely located (GPS coordinates with an accuracy of up to 25 m) while 27% show an accuracy of up to 1 km and 21% an accuracy between 1 and 10 km. Plots originate from four countries, comprising 2,295 plots (80%) recorded in Georgia, 433 in Azerbaijan (15%), 124 (4%) in Russia and 30 (1%) in Armenia. Georgian plots were sampled primarily in the Central Greater Caucasus and at lower elevations. Armenia is represented mainly by forest plots sampled in the northern part of the country. A higher number of plots cover Azerbaijan. However, they generally lack geographic coordinates due to missing localization in their source literature. Moreover, the database stores plots from selected studies from the main Greater Caucasus range and the Caucasian promontories in Russia.

The database utilizes the TURBOVEG species list Russia with plant species nomenclature following Czerepanov (1995) supplemented by several taxa described after this source was published. Regarding taxonomical composition, the database encompasses 2,500 taxon names. Out of this number, it contains 2,305 species of vascular plants from 139 families and 195 species of bryophytes from 39 families. The most frequent families of vascular plants include Asteraceae, Poaceae, Fabaceae and Rosaceae while Brachytheciaceae, Amblystegiaceae, Mniaceae and Pottiaceae represent the most common bryophyte families (Figure 3). All plots contain vascular plants accompanied by their cover values, while data on species composition of the bryophyte layer is available for 11% of plots.

As the database contains a large number of mesophilous forest plots, the most common trees across the dataset are: Carpinus betulus (present in 20% of all plots), Fagus orientalis (20%), Fraxinus excelsior (11%), Quercus petraea subsp. iberica (11%) and Tilia begoniifolia (9%). The most frequent herbs and shrubs encompass Galium odoratum (16%), Ranunculus oreophilus (16%), Leontodon hispidus (15%), Trifolium ambiguum (15%), Corylus avellana (15%), Bromus variegatus (14%), Veronica gentianoides (14%), Brachypodium sylvaticum (13%), Geranium robertianum (12%) and Campanula rapunculoides (12%). Aliens originating outside western Eurasia (sensu Kikodze et al. 2010) are relatively scarce in the dataset. The most common ones include the Asian herbs Oplismenus undulatifolius (6%) and Duchesnea indica (2%), and the North American tree Robinia pseudoacacia (1%). All chiefly occur in forest vegetation across low and warm parts of Transcaucasia.

The plot area varies (Figure 4), including plots of < 1 m² (0.5% of plots), 1–25 m² (23%), 26–100 m² (32%), 101–400 m² (17%) and > 400 m² (0.5%). For 27% of plots, the area is unknown. The elevation of plots ranges between 0 and 3,600 m (1,465 m on average). It shows a bimodal distribution (Figure 5) with maxima in lower elevations (lower forest belt) and subalpine and alpine zones. As basic soil properties are among the key environmental variables driving vegetation diversity, we provide measured soil pH for most plots recorded during the field expeditions (26%). It spans from 3.8 to 8.0 (6.3 on average).

The dominant vegetation formations of the database include deciduous broad-leaved forests, subalpine tall-forb vegetation, shrub and elfin forests, and alpine grasslands and heathlands. They all represent the region’s key natural vegetation (Bohn et al. 2000–2003). Many other habitats are also present in the database (Figure 6). Moreover, plots from the Caucasian gravel river bars are stored in a separate database (Kalníková and Kudrnovsky 2017).

The current version of the TVD is available upon request via GIVD (Dengler et al. 2011) and EVA (Chytrý et al. 2016).

Figure 1. Geographic distribution of georeferenced plots stored in the Transcaucasian Vegetation Database (to 2023-04-26).

Figure 2. Completeness of main header data for the plots stored in the Transcaucasian Vegetation Database. Grey areas show the proportion of plots containing data for the given variables.

Figure 3. Relative contribution (%) of the ten most frequent families in the Transcaucasian Vegetation Database.

Table 1. Numbers of plots in the Transcaucasian Vegetation Database recorded per decade. Decades with no plots available were omitted.

Decade	Number of plots
1921–1930	31
1931–1940	62
1971–1980	18
1991–2000	13
2001–2010	143
2011–2020	451
2021–2030	646
not indicated	1518
Total number	2882

Figure 4. Size (area) of plots stored in the Transcaucasian Vegetation Database.

Figure 5. Elevation distribution of plots stored in the Transcaucasian Vegetation Database.

Figure 6. Examples of vegetation types and complexes included in the Transcaucasian Vegetation Database. A) Colchic temperate rainforest with understory rich in ferns, Samegrelo Region, W Georgia; B) Mesophilous Fagus orientalis forest, Ijevan Region, N Armenia; C) Western Caucasian Abies nordmanniana forest, Racha Region, W Georgia; D) Complex of rock and forest vegetation in deeply incised valleys, Ijevan Region, N Armenia; E) Grazed alpine grassland in the Central Greater Caucasus, Racha Region, W Georgia; F) A diverse landscape of the intermontane Greater Caucasian basin, a mosaic of semi-natural and natural habitats including subhalophilous grasslands on travertine deposits, Khevi Region, N Georgia; G) Semi-desert in the arid parts of central Transcaucasia, Kartli Region, E Georgia.

Future perspectives

The TVD represents a developing vegetation database focusing on a global biodiversity hotspot where a comparable dataset has not been available to date.

Plots from the TVD are currently being analyzed and have been used in numerous international EVA projects, particularly those focusing on various aspects of the botanical, functional or ecological diversity of Europe and adjacent areas.

Data collection and storage in the TVD is an ongoing process. The number of stored plots is continuously growing by both the own field research of the authors and the digitization of newly published data. The field expeditions aiming at plot recording are led yearly and focused on various areas of the Southern Caucasus and diverse vegetation types. We plan to sample especially in poorly represented areas and vegetation types, both zonal (e.g. beech and coniferous forests, steppes) and azonal (e.g. wetlands, rocks and screes). Therefore, the geographic and ecological scope of the TVD is regularly extending. Consequently, the database might serve a wider variety of thematic projects dealing with, for instance, large-scale vegetation classifications, alien species monitoring, biodiversity assessments and the potential impact of climate change. Moreover, it provides data applicable to nature protection, including habitat mapping, environmental management planning, restoration projects, and vegetation monitoring. The plots with high precision of coordinates might be used as a baseline for a future resurvey that would detect eventual changes in vegetation structure and plant species assemblages.

The database intends not only to help fill the gaps in our knowledge of this key biodiversity area but also to provide an opportunity for international collaboration among vegetation scientists from various countries.

Author contributions

PN and VK conceived the idea of the database. PN built the database, elaborated data and led the writing. DS prepared the map. All authors provided vegetation plot data to the database, revised the manuscript and approved its final version.

Acknowledgements

We thank Svatava Kubešová, Eva Mikulášková and Tomáš Peterka for their considerable help with the bryophyte determination and Otar Abdaladze, Helena Chytrá, Kryštof Chytrý, Martin Harásek, Anna Hlaváčková, Petr Hubatka, Pavel Lustyk, Kateřina Nováková, Zdenka Preislerová, Štěpánka Pustková, Jaroslav Rohel, Jakub Salaš, Gabriela Štětková, Martin Večeřa, Pavla Vlčková and Kamila Zábranská for their help with the field sampling. The database was established and is managed and updated under the project of the Czech Science Foundation (project 19-28491X). The Aragvi Protected Landscape (Georgia) field sampling was funded by the Czech Development Agency (project GE-2020-008-RO-11110).

E-mail and ORCID

Pavel Novák (Corresponding author,[email protected]), ORCID:https://orcid.org/0000-0002-3758-5757

Veronika Kalníková ([email protected]), ORCID:https://orcid.org/0000-0003-2361-0816

Daniel Szokala ([email protected]), ORCID:https://orcid.org/0000-0002-3593-1791

Alla Aleksanyan ([email protected]), ORCID:https://orcid.org/0000-0003-4073-1812

Ketevan Batsatsashvili ([email protected]), ORCID:https://orcid.org/0000-0001-7654-3720

George Fayvush ([email protected]), ORCID:https://orcid.org/0000-0002-9710-2200

Sandro Kolbaia ([email protected]), ORCID:https://orcid.org/0009-0003-3602-3773

George Nakhutsrishvili ([email protected])

Vojtěch Sedláček ([email protected]), ORCID:https://orcid.org/0009-0001-2631-5612

Tadeáš Štěrba ([email protected]), ORCID:https://orcid.org/0009-0004-4829-6792

Dominik Zukal ([email protected]), ORCID:https://orcid.org/0000-0003-3248-5703

Supplementary materials

Supplementary material 1

Complete list of the sources of the plots acquired from the literature

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