New association Typhetum austro-orientalis ass. Nov. (Phragmito-magnocaricetea Klika in Klika et Nov'ak 1941) from Russia

Southeastern cattail ( Typha austro-orientalis ) was described in 2006 from the Volgograd region. The natural range of T. austro-orientalis covers the desert and steppe regions of the European part of Russia and Central Asia (Kazakhstan, Uzbekistan). The growth of this species was also noted to the north of the main area of its distribution: it is known in the Kaluga region and in the Vyatka-Kama Cis-Urals, recently discovered in Western Siberia, in the extreme south of the Tyumen region. Typha austro-orientalis differs from closely related species of cattails ( Typha linnaei , T. angustifolia ) both in the features of the morphology of monocarpic shoots and in the range. This species forms communities where it is a dominant and an edificator, which previously belonged to the ass. Typhetum angustifoliae Pignatti 1953. At the same time, the syntaxonomy of communities formed by T. austro-orientalis has not yet been developed. The purpose of this work was to establish the syntaxonomic status of the communities formed by T. austro-orientalis and to characterize the identified syntaxa. We carried out the studies of communities dominated by T. austro-orientalis in 2011-2020 on the territory of the Astrakhan region (Western steppe ilmens and Astrakhan State Natural Biosphere Reserve), within the Vyatka-Kama Cis-Urals (south of the Udmurtian Republic), and in Western Siberia (south of the Tyumen region). A total of 79 descriptions were made. To assess the abundance of species on the sample plots described, the J. Braun-Blanquet abundance scale was used with the following abundance-coverage scores: r - the species is extremely rare with insignificant coverage, + - the species is rare, the degree of coverage is small, 1 - the number of individuals is large, the degree of coverage is small or the individuals are sparse, but the coverage is large, 2 - the number of individuals is large, the projective cover is from 5 to 25 %, 3 - the number of individuals is any, the projective cover is from 25 to 50 %, 4 - the number of individuals is any, the projective cover is from 50 to 75 %, the number of individuals is any, the cover is more than 75 %. The relevés were introduced into database developed on the basis of the TURBOVEG program and processed using the JUICE program. The names of syntaxa are given according to the “International Code of Phytosociological Nomenclature”. The system of higher syntaxa is given in accordance with “Hierarchical floristic classification…”. The studied communities were assigned to the new ass. Typhetum austro-orientalis, 6 subassociations, and 13 variants. The nomenclature type of association is relevé N 12 in Table 3. It is shown that in the communities of the ass. Typhetum austro-orientalis, the number of species ranges from 1 to 16 (in average 6). The total projective cover varies from 20 to 100 % (in average 77.5 %). The height of the herbage is 2-5.5 m; five substages are distinguished in it. The first substage of the tallest grasses, as a rule, is dense, formed by the edificator of communities - T. austro-orientalis . In addition to it, other large cattails ( Typha domingensis , T. latifolia , T. australis ), as well as other species of tall grass helophytes, may be present in the first substage ( Phragmites altissimus , P. australis , Scirpus hippolyti , S. lacustris , Phalaroides arundinacea ). The second substage is formed by less tall grasses, the abundance of which varies from + to 5. This is a large group of plants (more than 30 species) belonging to different ecological groups: helophytes ( Alisma lanceolatum , Butomus umbellatus , Nelumbo caspica , Sparganium erectum , etc.), hygrohelophytes ( Bolboschoenus maritimus , B. glaucus , Carex riparia , Oenanthe aquatica ), hygrophytes ( Bidens tripartita , B. frondosa , Echinochloa crusgalli , Lycopus exaltatus , Lythrum salicaria , etc.) and hygromesophytes ( Amaranthus albus , Ambrosia artemisiifolia , Althaea officinalis и др.). The third substage is formed by surface grasses from the ecological groups of helophytes ( Alisma gramineum ), hygrohelophytes ( Agrostis stolonifera , Rorippa amphibia , etc.) and hygrophytes ( Atriplex prostrata , Galium palustre , Inula britannica и др.). The fourth substage is represented by hydrophytes floating on the water surface, belonging to non-rooting ( Hydrocharis morsus-ranae , Lemna turionifera , Salvinia natans , Spirodela polyrhiza ) or rooting ( Nuphar lutea , Nymphaea alba , Nymphoides peltata , Trapa astrachanica ) plants. The fifth substage contains submerged hydrophytes, both rooting ( Batrachium circinatum , Caulinia minor , Potamogeton lucens , Vallisneria spiralis , etc.) and freely floating in the water column ( Ceratophyllum demersum , Lemna trisulca , Utricularia australis , etc.).