New association of the West Siberian lowland meadows - Cirsio cani-Calamagrostietum epigeii

The wide spreading of semihydromorphic landscapes is a characteristic feature of the West Siberian subtaiga subzone. It is explained by a plain relief and poor draining of watersheds. Considerable anthropogenic transformation of the territory makes the study of contemporary state of ecosystems and preserved components of original vegetation topical. We carried out field studies in the central sector of the West Siberian plain: on the Tobol-Irtysh and the Ob-Irtysh watersheds. In the course of these studies, we discovered original communities of primary lowland meadows with salt-tolerant plants. Such communities usually occur near wet aspen-birch forests but sometimes form a vegetation belt between watershed meadows and herb mires. They often contact with saline meadows. Our task was description and syntaxonomic interpretation of these communities. By means of direct ordination and DCA-ordination, we showed that the studied group of meadows occurs in more salty habitats (more than 12 stages) in comparison with other lowland meadows but it is not separated on the gradient of moisture. The described communities commonly represent polydominant phytocenoses where codominate Calamagrostis epigeios, Brachypodium pinnatum, Filipendula ulmaria and rarely (in the Vagay river basin) - Molinia caerulea. Calamagrostis epigeios has the highest activity: its constancy is 78% and the cover averages 20% up to 80% in monodominant variants. The floristic composition always contains species of wet meadows and eutrophic mires, which indicates excessive moisture of habitats and species implying weak salt soils. Groups of meadow and meadow-forest species are represented completely enough as well as meadow-steppe and synanthropic plants. The ecological spectrum of coenoflora in relation to moisture has expressly bell-form with maximum of eumesophytes in the group that indicates the meadow character of communities. A considerable width of ecological spectrum is connected with ecological heterogeneity of floristic composition which manifests itself in coexistence of xerophyte and hygrophyte species. The ecological spectrum of coenoflora in relation to richness-salinity has a similar structure. Its basis is formed by eutrophic species. The floristic list of meadows contains halophyte species, their appearance is connected with periods of drying up of upper soil horizons when the concentration of soluble salts rises. According to a phytosociological classification, these communities were identified as a new association Cirsio cani-Calamagrostietum epigeii from alliance Deschampsion cespitosae, order Molinietalia, class Molinio-Arrhenatheretea. The described association contains a considerable bloc of species common with meadow associations of alliance Molinion caeruleae from Central Europe since their habitats have the same regime of moistening. But, because of peculiarities of edaphic conditions, the communities from West Siberia contain a group of halo-tolerant species which are not typical of European wet meadows. We found blue moor (Molinia caerulea) -European meadow species which has the east limit of distribution in West Siberia in the communities of the association. It also determines a primary native character of phytocoenosis high nature-protection signification of the described communities. The article contains 2 figures, 2 tables, 21 ref.

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