Meadow vegetation of the floodplains of the Vychegda and Pechora rivers. Order Arrhenatheretalia R. Tx. 1931
The present study continues a series of publications of the authors on diversity of the meadow vegetation in the floodplains of the Vychegda and Pechora rivers and their tributaries (Komi Republic). The floristic classification of wet meadows of the order Molinietalia Koch 1926 was published early (Shushpanikova, Yamalov, 2013). The results of floristic classification of meadow vegetation belonging to the order Arrhenatheretalia R. Tx. 1937 are discussed in this article. Analysis was based on 383 original relevés of the meadow vegetation of the order Arrhenatheretalia made in accordance with principles of the Braun-Blanquet approach (Braun-Blanquet, 1964; Mirkin and Naumova, 1998). The studies were performed in the floodplains of the Vychegda and Pechora rivers and their tributaries (Sysola, Kazhym, Pozheg, Viled, Usa, Colva, Synya, Sebys, Ilych, Syuzyu, Shchugor). The descriptions were conducted at the study plots of 10x10 m. Plant communities of small size were described within the natural limits. A location, dimensions of community, species composition, species saturation, composition of dominant and co-dominant species, total coverage and height of grass stand, aboveground phytomass production were identified. The abundance of species in meadow communities was recorded using the J. Braun-Blanquet method: r - species occurs sporadically, + - minor species, total coverage less than 1 %, 1 - 1-5 %, 2 - 6-25 % 3 - 26-50 %, 4 - 51-75 %, 5 - 76-100 %. The assessment of environmental parameters was performed by ecological methods of L. G. Ramensky (Ramensky et al., 1956). Syntaxonomic diversity of the meadow vegetation of the order Arrhenatheretalia of the Vychegda and Pechora rivers floodplains presented by 2 unions (Cynosurion R. Tx. 1947 и Festucion pratensis Sipaylova et al. 1985), 7 associations (Festucetum ovinae Turubanova 1986, Festuco pratensis-Deschampsietum caespitosae Turubanova 1986, Anthoxantho odorati-Agrostietum tenuis Sillinger 1933, Festuceto pratensis-Dactyletum glomeratae Dymina 1989 in Korolyuk et Kiprijanova 1998, Amorio repens-Poetumpratensis ass. nov., Equiseto arvensis-Elytrigietum repentis Maraculina 2009, Elytrigio repentis-Bromopsidetum inermis Yamalov 2011. Two new communities without rank are described (Agrostis vinealis, Hypericum maculatum-Phleum pratense). Most plant associations are heterogeneous by their floristic composition and they can be divided into 10 subassociations and 5 variants. The peculiarities of the floristic composition of the above mentioned associations, as well as their distribution and ecology are discussed. The distinguished associations are well differentiated by their elevation level on the floodplains. The meadow communities of Festucetum ovinae are located on the highest floodplains in the inland zone; there is Agrostis vinealis in the streamside zone of the floodplains. The meadow communities of the ass. Anthoxantho odorati-Agrostietum tenuis are located on the low floodplains in the streamside zone. The meadow communities of the associations Festuco pratensis-Deschampsietum caespitosae, Equiseto arvensis-Elytrigietum repentis, Elytrigio repentis-Bromopsidetum inermis, Festuceto pratensis-Dactyletum glomeratae are occupied the medium level floodplains. The meadow communities of the ass. Amorio repens-Poetum pratensis are found at different locations of the floodplain; they are formed under grazing. The described meadows grow on the soils with different ecological indicators. The distinguished associations are differentiated by water level (52.2-73.0), average figures - 55.9-68.9. The meadow communities of the ass. Festucetum ovinae occupy the driest sites of the floodplain; the ass. Antho xantho odorati-Agrostietum tenuis is located in the wettest floodplains. The meadow communities of the ass. Elytrigio repentis-Bromopsidetum inermis occupy most rich and alluvial soils. They are located on the low ridges in the middle zone of the floodplain and they are formed by annual