Syntaxonomy of desert steppe vegetation of Bogdinsko-Baskunchakskiy natural reserve (class Artemisietea lerchianae V. Golub 1994)
The Astrakhan region, one the most arid region of Russia, is mainly a plain territory with the unique mountain Bolshoe Bogdo, where the Bogdinsko-Baskunchaksky natural reserve was founded, including the adjacent plains and Baskunchak Lake. So far syntaxonomy of arid regions of Russia are rather poor, only the Lower Volga valley is described in detail (Golub, 1994; Golub, Maltsev, 2013). The aim of present study was to carry out floristic classification of desert-steppe vegetation of the reserve territory. The study is based on the authors’ 133 relevés, made in 2019, and 41 published ones (Safronova, 2013). Cluster analysis was carried out (Ward’s method, Chekanovsky-Dyce-Sorensen coefficient). Two dendrograms, built on the species presence-absence and their cover, allowed to distibguish phytocenons and determine their differential species. At the first step, the dendrogram based on the species presence-absence was analyzed (Fig. 3). At levels from 2 to 8 clusters, the number of differential species with IV-V class constancy (Table 1) were assess. At the level of 3 clusters all relevés were divided into petrophytic, psammophytic and zonal communities (Table 2). According to large number of differential species two classes (Artemisietea lerchianae V. Golub 1994 - petrophytic desert-steppe communities and Festucetea vaginatae Soo ex Vicherek 1972 - psammophytic steppes) were distinguished. Also desert-steppe communities on fine soils which belong to the first class without own differential species were distinguished and their relevés were included in further analysis. Class Artemisietea lerchianae V. Golub 1994 unites the northern desert and desert steppe communities. Diagnostic species (D. s.): Alyssum turkestanicum, Anabasis aphylla, A. salsa, Artemisia lerchiana, Bassia prostrata, Camphorosma monspeliaca, Nitrosalsola dendroides, Ceratocarpus arenarius, Ceratocephala testiculata agg., Eremopyrum orientale, Ferula caspica, Medicago medicaginoides, Meniocus linifolius, Peganum harmala, Petrosimonia oppositifolia, Poa bulbosa, Zygophyllum fabago. Order Agropyretalia desertorum ord. nov. includes desert steppes, widely spread in the southern part of the steppe zone, with domination of semishrubs and bunchgrasses. Holotypus hoc loco - ass. Artemisio lerchianae-Stipetum sareptanae ass. nov. D. s.: Agropyron desertorum, Allium inderiense, A. tulipifolium, Astragalus pseudotataricus, A. testiculatus, Ephedra distachya, Erysimum leucanthemum, Euphorbia undulata, Galatella tatarica, Prangos odontalgica, Rochelia retorta, Serratula erucifolia, Sterigmostemum caspicum, Stipa lessingiana, S. sareptana, Tanacetum achilleifolium, Tragopogon marginifolius, Tulipa patens, T. biflora. Alliance Agropyrion desertorum all. nov. Holotypus hoc loco - ass. Artemisio lerchianae-Stipetum sareptanae ass. nov. D. s. of the alliance = D. s. of the order. Ass. Artemisio lerchianae-Stipetum sareptanae ass. nov. hoc loco (Table 4, rel.1-34), holotypus hoc loco: Table 4, relevé 1 (field number 19-077), Astrakhan region, Akhtubinskiy district, to the south of the Nizhny Baskunchak village, Bolshoe Bogdo Mt., 48.13294° N, 46.83287° E, convex near-top part of NNE slope, 22.05.2019, author: A. Yu. Korolyuk is central in the alliance. D. s.: Agropyron desertorum, Ephedra distachya, Erysimum leucanthemum, Prangos odontalgica, Stipa lessingiana, S. sareptana, Tanacetum achilleifolium, Tulipa biflora. Oommunities occupy large areas at foothills and gentle slopes of ridges, occasionally occur on moderately steep slopes. Ass. Artemisio pauciflorae-Atraphaxietum replicatae ass. nov. hoc loco (Table 5, rel. 1-13), holotypus hoc loco: Table 5, relevé 1 (field number 19-081), Astrakhan V. Golub 1994, Akhtubinskiy district, to the south of Nizhny Baskunchak village, Bolshoe Bogdo Mt., 48.13597° N, 46.84192° E, plain area, slight depression, 22.05.2019, author: A. Yu. Korolyuk. D. s.: Anabasis salsa, Artemisia pauciflora, A. semiarida, Atraphaxis replicata, Atriplex cana, Camphorosma monspeliaca, Catabrosella humilis, Ferula caspica. Communities occur on convex slopes of various exposition, often with active erosion. Ass. Stipo lessingianae-Artemisietum tauricae ass. nov. hoc loco (Table 5, rel. 14-37), holotypus hoc loco: Table 5, relevé 14 (field number 19-085), Astrakhan region, Akhtubinskiy district, to the south of Nizhny Baskunchak village, Bolshoe Bogdo Mt., 48.13558<sub>°</sub> N, 46.84563<sub>°</sub> E, gentle foothill of the eastern slope, 22.05.2019 author: A. Yu. Korolyuk. D. s.: Artemisia taurica, Elaeosticta lutea, Galatella villosa, Tulipa gesneriana, Veronica multifida. Relatively closed ommunities are most often common at foothills, also they occur on tops of ridges and their slopes of various steepness and exposition. Order Artemisietalia lerchianae V. Golub 1994, central in the class, unites zonal northern desert communities, at least within the Caspian region. D. s.: Alyssum turkestanicum, Anabasis aphylla, A. salsa, Artemisia lerchiana, Camphorosma monspeliaca, Caroxylon dendroides, Ceratocarpus arenarius, Ceratocephala testiculata agg., Eremopyrum orientale, Ferula caspica, Bassia prostrata, Medicago medicaginoides, Meniocus linifolius, Peganum harmala, Petrosimonia oppositifolia, Poa bulbosa, Zygophyllum fabago. Alliance Artemision lerchianae V. Golub 1994. D. s. of the alliance = D. s. of the class and order. Ass. Poo bulbosae-Artemisietum lerchianae ass. nov. hoc loco (Table 6, rel. 1-39), holotypus hoc loco: Table 6, relevé 34 (field number 19-135), Astrakhan region, Akhtubinskiy district, to the northwest of Nizhny Baskunchak village, 48.23968<sub>°</sub> N, 46.81434° E, 24.05.2019, author: A. Yu. Korolyuk. D. s.: Alyssum turkestanicum, Anabasis aphylla, Artemisia lerchiana, Ceratocarpus arenarius, Eremopyrum orientale, Meniocus linifolius, Poa bulbosa. Communities dominated by Artemisia lerchiana and Poa bulbosa develop on fine soils within the subzones of northern deserts and desert steppes. Subass. P. b. -A. l. typicum subass. nov. hoc loco (Table 6, rel. 34-39). Communities are widely spread in the northern part of the desert zone and less common in the subzone of desert steppes. Subass. P. b.-A. l. tanacetosum achilleifolii subass. nov. hoc loco (Table 6, rel. 1-33), holotypus hoc loco: Table 6, relevé 12 (field number 19-008), Astrakhan region, Kharabalinskiy district, to the NW from the Volnoe village, the upper part of gentle slope, 47.16164° N, 47.59213° E, 17.05.2019, author: A. Yu. Korolyuk. D. s.: Astragalus dolichophyllus, Gagea bulbifera, Holosteum umbellatum, Medicago orthoceras, Tanacetum achilleifolium, Veronica triphyllos. Within subassociation, which is common within the desert steppe subzone, two variants are distinguished: typica (Table 6, rel.12-33) and Artemisia taurica (Table 6, rel.1 -11). Alliance Anabasio salsae-Artemision pauciflorae Lysenko in Lysenko et Mucina 2015 unites communities dominated by Anabasis salsa and Artemisia pauciflora on solonetz soils (Lysenko, Mucina, 2015), common in the subzones of dry and desert steppes as well as in the north of the desert zone. D. s.: Anabasis aphylla, A. salsa, Artemisia pauciflora, Atriplex cana, Leymus ramosus, Suaeda physophora. Community Anabasis salsa (Table 6, rel. 40-45) dominated by nameforming species occur on eroded slopes of clay saline deposits at the territory of Bogdinsko-Baskunchaksky reserve and adjacent land-scapes.