Aquatic vegetation of the South Urals (Bashkortostan Republic). II. Class Potametea

Republic of Bashkortostan (51º 34ʹ–56º 31ʹ N and 53º 08ʹ–59º 59ʹ E) covers an area of 143.6 thousand km² stretching fr om north to south about 550 km, from west to east — 440 km. Its territory is located within the Southern Urals and adjacent plains. The relief is complex and diverse, strongly dissected. Elevations range from 60 to 1640 m above sea level.

Climate is continental, with pronounced diffe­rences between average monthly temperatures. The average July temperature ranges from +16.5 to +20.0 °C, the average January temperature — from –11.6 to –17.0 °C. There has been quite a sharp difference in the distribution of precipitation in the territory: average annual precipitation of 300 mm (in the southern regions of Transurals) to 750 mm (in the mountain forest zone of the Southern Urals). The frost-free period is 40 to 130 days (Gareev, 2001).

The river system of the investigated area belongs to the three largest river basins: the Volga (79 % of the territory), the Ural (20 %) and the Ob (less than 1 %). The rivers of the Republic are mostly snow-feed; they are characterized by rising of the water level during spring flood and there is a small rise caused by autumn rains. On the territory of the Republic of Bashkortostan operated 943 units of reservoirs and ponds, including 511 units of more than 100 thousand m³. There are about 3000 lakes. They mostly oxbow origin and located in the valleys of large rivers (the Belaya, the Ufa, the Dema, the Aj etc.). Some large lakes of the Cisurals (the Aslykul, the Kandrykul, the Akkul) are karst reservoirs. In the foothills of the Transurals there is a chain of lakes, kettles formed as a result of tectonic processes (the Karagajly, the Bolshie Uchaly, the Urgun, the Kalkan, the Karabalakty, the Chebakty, the Yaktykul, the Surtandy). There are 20 lakes with a surface area of 22 to 2 km², among them 4 lakes belong to the Volga river basin, 15 — to the Ural and 1— to the Ob.

The aquatic vegetation of the Southern Urals (Republic of Bashkortostan) became a subject of geobotanical research only the second half of the XX century. In 1986, a group of geobotanists from Ufa in the Bashkir Cisurals and mountain forest zone of the South Urals investigated some rivers (and oxbows): the Belaya, the Ufa, the Dema, the Inzer, the Ashkadar, the Kuganak, the Sterlya and a number of lakes: the Anuchino, the Arhimandritskoe, the Berezovoe, the Gryaznoe, the Dolgoe, the Shamsutdin. The vegetation of water objects in Salavat, Sterlitamak and Meleuz towns (Grigoryev, Solomeshch, 1987; Petrov, Grigoryev, 1991; Petrov, Onishchenko, 1991) was studied also. Important contribution to the observation of aquatic vegetation of the Bashkir Cisurals was made by German geobotanists (Klotz, Köck, 1984). They identified a number of associations. Later, aquatic communities have been investigated only occasionally during the complex geobotanical research in some areas of the Bashkir Cisurals and the Transurals (Baktybaeva et al., 2011; Golovanov et al., 2011; etc.).

The database on vegetation of water bodies of the South Urals on the basis of the published relevés and the relevés obtained by authors was created. This article is based on 604 geobotanical relevés of water communities of class Potametea, carried out from 1986 to 2012. Most of relevés (272) was made by S. S. Petrov; 140 — Z. B. Baktybaeva; 109 — Ya. M. Golovanov; 83 — I. N. Grigoriev. Water reservoirs wh ere the relevés were made vary from rivers, lakes and oxbows belonging to the river basins of the Belaya and the Ural. In this article we applied the modern European syntaxonomical system to the class Potametea.

The analysis of phytocoenotic variety of vegetation of the class Potametea Klika in Klika et Novák 1941 was carried out. This article continues to review the aquatic vegetation of the Southern Urals (Yamalov et al., 2014). The results of the syntaxonomical analysis of the collected materials of vegetation of the class Potametea are presented.

The aquatic vegetation of South Urals of the class Potametea is classified to 2 orders, 4 unions, 24 associations, 27 variants, 4 facies and 1 community. Class Potametea unites communities of hydrophytes such as bottom watering plants with floating leaves, widespread in reservoirs with still or drift water. Class Potametea is a cosmopolitan one. The Najadetum minoris and Trapetum natantis associations are noted in this region for the first time. On the territory of the Southern Urals these associations have a limited distribution such as a floodplain of the Ufa River (the Svetloe Lake etc.). Communities of associations are found in the lakes with slimy bottoms. The diagnostic species of the association Trapetum natantis is listed in the Red Book of Bashkortostan Republic with categories 1 — species on the critically endangered. Many other associations (Elodeetum canadensis, Potametum crispi, Potametum lucentis, Potametum pectinati, Potametum perfoliati, Potameto–Nupharetum luteae, Nymphaeetum candidae etc.) are widespread in the Bashkortostan Republic; their communities grow in various water reservoirs.

The comparative analysis of communities of the class Potametea described from the various regions of Russia and the neighboring countries has shown that the South Urals is characterized by a high syntaxonomic variety. The mentioned above communities are the most similar to the communities described in the undercurrent of the Volga River (Golub, Maltsev, 2013). This fact may be explained by the nearly latitudinal location of the regions and the similarity of water reservoirs types belonging to the same river basin. The smallest similarity is noticed for the communities of the northern regions of Russia (Chemeris, 2004; Teteryuk, 2012; et al.) and the southern part of the Eastern Siberia (Chepinoga et al., 2013).