Syntaxonomy of xeropetrophytic vegetation of Southern Urals: alliance Elytrigion pruiniferae all. nov.

Abstract

The dominance of xeropetrophytic plant communities with original species composition along with high phytocenotic diversity is the first to determine the distinctness of the South Ural low-mountain steppe province within the Ural Mountains. As the zonal steppe ecosystems are totally destroyed and transformed, petrophytic cenoses represent the predominant type of natural vegetation. They are of high conservation importance due to preserving unique biodiversity with a large number of rare and endangered species, relics and endemics (Ryabinina, 2003; Yamalov et al., 2019). Stony steppes in the Southern Urals have been studied for more than 100 years. Initiated in the 1980s, the syntaxonomical research covers now only the limited territories, mainly within the protected areas (Unikalnye ..., 2014; Prirodnye ..., 2018). The recent studies are focused on the relationship between the petrophytic vegetation and macroecological gradients in the context of geographical zonation (Zolotareva et al., 2019; Korolyuk et al., 2020). Our study presents the results of the analysis of 265 relevés of petrophytic communities of the steppe zone, carried out by the authors on the territory of the Gaysky, Kuvandyksky, Saraktashsky and Belyaevsky administrative districts of the Orenburg region, as well as the Khaibullinsky district of the Bashkortostan Republic in 2014–2018 (Fig. 1). Six phytocoenons were identified using the TWINSPAN algorithm followed by manual sorting. They represent the main diversity of petrophytic vegetation in the studied region and differ in the groups of species identified by formal criteria (Korolyuk et al., 2016; Zolotareva et al., 2019). We conducted the cluster analysis to compare these with the petrophytic associations of the Urals: 26 associations from the classes Festuco-Brometea Br.-Bl. et Tx. ex Soó 1947 and Anabasietea cretaceae Golovanov et al. 2021 (Fig. 2, 3). Five communities were assigned to the steppe vegetation, and their position in the syntaxonomical system was determined. Communities 1–3 regarded as typical steppes have similar floristic composition and dominant plants; community 4 is closer to the rich forb-bunchgrass steppes; community 5 and the ass. Anthemido trotzkianae–Thymetum guberlinensis have transitional features to desert steppes. We identified the new alliance Elytrigion pruiniferae all. nov. D. s.: Allium tulipifolium, Alyssum turkestanicum, Artemisia salsoloides, Centaurea turgaica, Elytrigia pruinifera, Ferula tatarica, Linaria uralensis, Poa bulbosa s. l., Polycnemum arvense, Spiraea hypericifolia. Holotypus — the association Elytrigietum pruiniferae Lebedeva ass. nov. Alliance represents xeropetrophytic vegetation of the steppe zone of the South Urals. Its area covers the watersheds of the Sakmara, Ural and Ilek rivers. Its communities were also found on the right bank of the Sakmara river (the Guberlya and Kuragan basins), as well as in the lower part of the Bolshoy Ik river basin. The communities occupy convex slopes and tops of ridges with immature gravelly soils. In the southern part of the alliance distribution area, they are confined to slopes of various shapes and exposures, while in the northern part mainly to convex southern slopes or to the top of the ridges. The alliance represents xerophytic part of the order Helictotricho-Stipetalia. It replaces the more mesophytic alliance Helictotricho desertori–Orostachyion spinosae on the moisture gradient (Korolyuk, 2017). The alliance includes 3 associations and 1 community type. Ass. Elytrigietum pruiniferae Lebedeva ass. nov. (Table 4), holotypus — rel. 1 (field no. 15-086): Orenburg region, Kuvandyk district, 1.5 km southwest of Yalnair village, near-summit convex part of a rocky slope, 51.28635°N, 57.81782°E, 10.06.2015, author — A. Yu. Korolyuk. D. s.: Alyssum turkestanicum, Centaurea turgaica, Elytrigia pruinifera, Linaria uralensis, Poa bulbosa s. l., Polycnemum arvense, Spiraea hypericifolia, Thymus guberlinensis, Tulipa scythica. The association unites petrophytic steppes in hilly lands and low-mountains of the Saraktash, Kuvandyk and Gaysky districts of Orenburg region and on the Turatka mountain in Khaibullinsky district of Bashkiria. The cenoses are confined to convex slopes and tops of ridges. They are developed on gravelly soils on outcrops of basic and metamorphic rocks, less often on sedimentary rocks. There are 4 variants within the association. Ass. Thymo guberlinensis–Galatelletum villosae Yamalov ass. nov. (Table 5), holotypus — rel. 2 (field no. 16-015): Orenburg region, Kuvandyk district, 19 km SW of Zaluzhye village, 51.18268°N, 56.91858°E, author — A. Yu. Korolyuk. D. s.: Astragalus tenuifolius, Ephedra distachya, Galatella villosa, Hedysarum argyrophyllum, Meniocus linifolius, Scorzonera stricta, Stipa lessingiana. The association represents xerophytic stony steppes. They occur in all regions confined mainly to the southern slopes and tops of ridges with fine gravelly soils on sedimentary rocks. There are 4 variants within the association. Ass. Stipo zalesskii–Centauretum turgaicae ass. nov. (Table 6, rel. 7–22), holotypus — rel. 10 (field no. 17-122): Orenburg region, Gaysky district, east of the Kazachya Guberlya village, slightly convex slope of the ridge in the near-top part, 51.14663°N, 58.03227°E, 06.18.2017, author — A. Yu. Korolyuk. D. s.: Amygdalus nana, Campanula sibirica, Carex pediformis, Cephalaria uralensis, Erysimum canescens, Helictotrichon desertorum, Pulsatilla patens, Stipa pulcherrima, S. zalesskii. The association was described in the southeastern part of the Guberlinsky Uplands (Gaysky District). The communities occupy habitats typical for petrophytic steppes — convex slopes and tops of ridges on outcrops of basic and metamorphic rocks. The associations Elytrigio pruiniferae–Stipetum sareptanae Golovanov ass. nov. and Anthemido trotzkianae–Thymetum guberlinensis Golovanov et al., 2021 were described in the study area as well. Ass. Elytrigio pruiniferae–Stipetum sareptanae ass. nov. (Table 7), holotypus — rel. 10 (field no. GY18-043): Orenburg region, Kuvandyk district, 4 km SE Novyi village, Suyunduksai Balka, 51.02067°N, 57.33993°E, author — Ya. M. Golovanov. D. s.: Artemisia lerchiana, Astragalus tenuifolius, Atraphaxis frutescens, Ephedra distachya, Gypsophila rupestris, Hedysarum argyrophyllum, H. razoumovianum, Meniocus linifolius, Sterigmostemum tomentosum. The association is found mainly to the south of the latitudinal section of the Ural River within the Guberlinsky Uplands (Kuvandyk District), as well as of the hilly lands of the South Urals (Saraktashsky District). The communities are confined to slopes of different exposure and steepness on outcrops of sedimentary rocks. The plants of dry and desert steppes, as well as those preferring chalk outcrops, are among the diagnostic species. This brings the association together with desert-steppe communities of the order Agropiretalia Korolyuk et Laktionov 2021, class Artemisietea lerchianae Golub 1994 (Korolyuk, Laktionov, 2021). Nevertheless, the composition and structure of cenoses confirm the assignment of the association to the class Festuco-Brometea. There are 4 variants within the association. The diversity of xeropetrophytic vegetation of the South Urals is much higher than that described in the article. The involvement of data from the adjacent regions of Kazakhstan will facilitate the further development of its syntaxonomical system.