Diversity of aquatic plant communities in the lakes of the Ob-Irtysh interfluve (West Siberia)

Abstract

The information on the syntaxonomic diversity of aquatic vegetation in the Ob-Irtysh interfluve (south of West Siberia), which was revealed using the ecological-floristic approach (Braun-Blanquet, 1964) is summarized. Lake ecosystems of the studied region are exposed to cyclical changes in accordance with the cyclicity of the hydrological regime of the lakes. Periodic fluctuations in the water level in lakes are accompanied by changes in mineralization, and therefore the biological regime of the lakes is unstable. The studies were carried out from 2001 to 2014 in Novosibirsk Region and Altai Territory. 164 complete geobotanical relevés made by the author on 80 lakes are used (Fig. 1, table 1); a list of studied lakes is given. Field work was carried out during the period of the lowest water level (summer dry season) — July–August. The following scale was used for abundance estimation: r — the species is extremely rare; + — rare, small cover; 1 — the number of individuals is large, the cover is small or individuals are sparse, but the cover is large; 2 —cover of 5–25 %; 3 — 26–50 %; 4 — 51–75 %; 5 — more than 75 %. Computer programs Turboveg for Windows 2.117 (Hennekens, Schaminée, 2001) and Juice 7.0.45 (Tichý, 2002) were used for data treatment. The syntaxonomic affiliation of phytocenoses was determined using modern literature (Bobrov, Chemeris, 2006; Vegetace…, 2011; Chepinoga, 2015; Landucci et al. 2015; Mucina, 2016). The coenotic diversity of aquatic vegetation in the studied lakes is 43 associations and 2 communities from 12 alliances, 6 orders, 5 classes (Tables 2–11). Eight associations belong to the class Lemnetea; 18 associations — Potamogetonetea; 3 associations and 2 communities — Stigeoclonietea tenuis; 9 associations — Charetea intermediae; 5 associations — Ruppietea maritimae. This rather high value of phytocenotic diversity is due to the high diversity of ecological conditions of specific lakes, in turn, determined by the different origin of lakes, the nature and composition of soils, salinity and chemical composition of waters, and temperature regime. Two new associations – Najadetum majoris ass. nov. and Ranunculetum subrigidi ass. nov. — are described. Table 10 shows the values of the frequency of associations (aquatic communities) in the lakes of the Novosibirsk region. We have identified phytocenotic complexes on the basis of data on the ranges of halotolerance of associations and in accordance with the frequency of associations in the lakes of different mineralization. Four phytocenotic complexes can be distinguished for the studied lakes of the Baraba Lowland and Kulunda Plain: freshwater, oligo-mesohaline, meso-hyperhaline, and euryhaline (Fig. 12). As for the ranges of halotoleration of lake communities, it is obvious that it is impossible to establish the universal ranges of halotolerance of species and communities of macrophytes for a number of reasons 1) regional differences in the salt composition of waters, 2) seasonal fluctuations in water salinity; 3) varying methods of mineralization measuring (ionometrically or analytically and also different analytical methods — by the sum of ions, and by the dry residual). However, several general trends can be distinguished. The main trend is a decrease in the species and coenotic diversity of aquatic and semi-aquatic vegetation with mineralization growth (Hammer, 1988; Williams, 1998; our data, etc.) This universal pattern is true for all groups of biota (Hammer, 1986; Williams, 1998; Kipriyanova et al., 2007, etc.). Communities of the assosiations Lemnetum trisulcae, Lemno–Utricularietum vulgaris, Potamogetono–Ceratophylletumsubmersi, Najadetum marinae, Potamogetonetum perfoliati were more resistant to high mineralization (up to 5 g/dm3 according to our data). The highest halotolerance among aquatic plant communities is found for the associations Ruppietum maritimae and Ruppietum drepanensis, as well as for Cladophoretum fractae. Based on the results of our research, it has been shown that in the continental lakes of the southeast of Western Siberia, such specific cenoses of continental water bodies of Siberia, as the communities of the assosiations Stuckenietum macrocarpae and Cladophoro fractae–Stuckenietum chakassiensis (Kipriyanova, 2017), mainly occur in oligo- and mesohaline waters in the range of mineralization 0.5–18.0 g/dm3. Stratiotetum aloidis, Nymphaeo–Nupharetum luteae, Nymphaeetum candidae associations were common in the freshwater lakes (up to 0.5 g/dm3), another ones were met moderately and less frequently. Associations Lemnetum trisulcae, Lemno minoris Ceratophylletum demersi were common in the β-oligohaline (0.5–1 g/dm3) lakes. Lemno–Utricularietum vulgaris, Myriophylletum sibirici, Potamogetonetum pectinati, Potamogetonetum perfoliati, Stuckenietum macrocarpae were moderately frequent, the rest were rare and solitary. Associations Lemnetum trisulcae, Lemno minoris–Ceratophylletum submersi, Stuckenietum macrocarpae, and Cladophoro fractae–Stuckenietum chakassiensis were common in the α-oligohaline lakes (1–5 g/dm3). The rest were moderately and less frequent. In mesohaline waters (5–18 g/dm3), associations Cladophoro fractae–Stuckenietum chakassiensis and Ruppietum maritimae were common. The rare in the studied lakes communities of the associations Najadetum marinae, Ruppietum maritimae, Ruppietum drepanensis, Charetum tomentosae, Nitellopsidetum obtusae are need in protection, since they include the species listed in the Red Data Book of the Novosibirsk Region (Krasnaya ..., 2018).