Plant communities of the Sarykum sand massif (Republic of Dagestan)

Open sands are usual elements of subarid and arid landscapes in Eurasia. The unique psammophytic flora makes an important contribution to the regions’ biological diversity. From the syntaxonomical point of view, psammophytic vegetation of south-east European part of Russia still poorly explored. The Sarykum sand massif is a unique object, due to its location in piedmonts of the Caucasus at a considerable distance from vast sands of Terek-Kum and Caspian lowlands (Fig. 1, 2). Our study presents the results of the analysis of 66 relevés. The data set was stored and processed in IBIS 7.2 software. As a result of performing hierarchical cluster analysis using Ward’s method, dendrogram was constructed reflecting the similarity of the relevés. Sokal/Sneath coefficient No. 1 which considers positive and negative species concurrences was used. Cluster analysis made it possible to reveal general differentiation patterns in psammophytic vegetation (Fig. 3). As a result, the relevés set was divided into two clusters differing in 28 species (Table 1). Cluster A represents poor of species and sparse communities on not fixed sands — in average 9 species per relevé and 18 % of the plants cover. Cluster B includes coenoses of fixed sands, with an average richness of 23 species and cover of 27 %. The studied communities belong to the class Festucetea vaginatae Soó ex Vicherek 1972, which represents the sandy steppes. It is distributed in the forest-steppe and steppe zones of Eastern and South-Eastern Europe, as well as in the south of Western Siberia and Northern Kazakhstan. The class includes the only order Festucetalia vaginatae Soó 1957. Psammophytic vegetation described from various regions of southern Russia belongs to the alliance Festucion beckeri Vicherek 1972, but none of its diagnostic species was noted in relevés. Comparison of our data with the associations described in the class on the territory of Russia and Ukraine allowed us to identify a group of species differentiating the psammophytic vegetation of the Sarykum massif: Artemisia tschernieviana, Astragalus brachylobus, Asperula diminuta, Centaurea arenaria, Syrenia siliculosa, Thesium maritimum, Tragopogon dasyrhynchus ssp. daghestanicus. These species can become the basis for the diagnosis of a new alliance. Its definition will be possible as a result of comparative analysis of psammophytic vegetation of the southeast of European Russia, primarily of the Caspian and Terek-Kum sands. Аss. Senecioni schischkiniani–Artemisietum tschernievianae ass. nov. (Table 2, relevés 1–18). Holotypus — relevé 1 in Table 2. (field no. 21-004), Republic of Dagestan, Kumtorkalinsky region, WSW from Korkmaskala village, Sarykum sands, leveled area in the upper part of the dune, 43.00751°N, 47.23290°E, 12.05.2021, author — A. Yu. Korolyuk. Diagnostic species (D. s.): Artemisia tschernieviana, Senecio schischkinianus, Melilotus polonicus, Tragopogon dasyrhynchus ssp. daghestanicus. Communities are found in the central, most open part of the Sarykum massif. They occupy slopes, as well as plane areas characterized by active sands winding (Fig. 4). Artemisia tschernieviana usually dominates. Аss. Leymo racemosi–Artemisietum tschernievianae ass. nov. (Tabl. 2, relevés 19–26), Holotypus — relevé 19 in Table 2. (field no. 21-026), Republic of Dagestan, Kumtorkalinsky region, WSW from Korkmaskala village, Sarykum sand massif, gentle northern slope of the dune, 43.01028°N, 47.23391°E, 13.05.2021, author — A. Yu. Korolyuk. D. s.: Artemisia tschernieviana (dom.), Leymus racemosus. The association represents pioneer cenoses that are widespread in the central elevated part of the massif. They are formed on slopes that are actively covered with sand (Fig. 5). The communities are sparse, with a cover of 10 to 25 % and the only dominant is Artemisia tschernieviana. Аss. Jurineo ciscaucasicae–Stipetum borysthenicae ass. nov. (Table 3, relevés 1–31). Holotypus — relevé 1 in Table 3. (field no. 21-030), Republic of Dagestan, Kumtorkalinsky region, WSW from Korkmaskala village, Sarykum sand massif, gentle slope of small hill in the northern foot of the dune, 43.0112°N, 47.2333°E, 13.05.2021, author — A. Yu. Korolyuk. D. s.: Agropyron fragile, Artemisia tschernieviana, Cephalaria uralensis, Cerastium semidecandrum, Jurinea ciscaucasica, Medicago caerulea, Pleconax conica, Scorzonera biebersteinii, Stipa borysthenica, Syrenia siliculosa, Teucrium orientale, Thesium maritimum. The communities of the association represent the background type of vegetation of the more fixed sands of the Sarykum massif. They develop on plane areas, gentle slopes of hillocks and ridges, along the bottoms of old blowed hollows (Fig. 6, 7). More than other species Cephalaria uralensis dominates, less are Agropyron fragile, Artemisia tschernieviana, Euphorbia seguieriana, Scorzonera biebersteinii, Secale sylvestre, Stipa borysthenica, Teucrium orientale, Ziziphora serpyllacea. As part of the association, we distinguish three variants: var. typica (Table 3, op. 1–16) is widely distributed to the north and northeast of the Sarykum dune, var. artemisia marschalliana (Table 3, op. 17–24) represents the richest communities of sandy steppes, var. inops (Table 3, op. 25–31) was noted only in the southern part of the massif on the sections adjacent to the railway. Five communities were described at the studied area. Com. Leymus racemosus occupy small patches, usually they form narrow strips between open sand and sagebrush coenoses (Fig. 8). Com. Eremosparton aphyllum was described in the middle part of the massif on the ridge slope (Fig. 9). Com. Calligonum aphyllum was observed on the top of a small sandy hill (Fig. 10). Com. Salix caspica was found on the tops of sand hills and represents large willow clones 2–3 meters high. Com. Imperata cylindrica was registered in the southwestern part of the massif along the slopes and bottom of depression (Fig. 11). Differentiation of classes Festucetea vaginatae and Artemisietea lerchianae Golub 1994 is an interesting syntaxonomical problem. In the European Vegetation Checklist (Mucina et al., 2016), the class Artemisietea tschernievianae Golub 1994, representing psammophytic vegetation, is assigned to the second class as a synonym. We carried out a formalized analysis of Dagestan communities and syntaxa of three classes described in Astrakhan, Saratov, and Rostov Regions (Fig. 12). Cluster analysis divided the syntaxa into two groups corresponding to the classes Artemisietea lerchianae (A) and Festucetea vaginatae (B). Desert associations of the class Artemisietea lerchianae united together with ass. Artemisietum tschernievianae Golub 1994. This association is the holotype of the class Artemisietea tschernievianae, so the latter one should be recognized as synonym of the class Artemisietea lerchianae, representing deserts and desert steppes (Korolyuk, Laktionov, 2021). The ass. Koelerietum sabuletorum Golub 1994 joined together with other syntaxa of the class Festucetea vaginatae representing sandy steppes and vegetation of fixed sands. The vegetation of the Sarykum sand massif is represented by original plant communities and numerous plant species that are typical for Middle Asia. In addition, about 20 plant species listed in the regional and federal Red Books grow on the territory of «Sarykum dune» cluster of Dagestan reserve and its protected zone. Despite the protection regime, the dune ecosystems are under human impact, which negatively affects the dune ecosystems.