Classification of communities with invasive species in the South Urals. II. Communities with a presence of genera Cyclachaena Fresen. and Xanthium L. species

This article is the second part of the series of publications on vegetation classification of communities with invasive species in the South Urals (Abramova, 2011). The communities with a presence of two aggressive species of North American origin such as Cyclachaena xanthiifolia (Nutt.) Fresen. and Xanthium albinum (Widd.) H. Scholz. are presented. Both species are included in “The black book of flora of the Central Russia” (Vinogradova et al., 2010). Research was conducted during 2000–2009 in the territory of Bashkortostan Republic. Species invasion in the region and their naturalization on flood plains of the South Urals was noted (Abramova, Anufriyev, 2008; Abramova, 2014; Abramova, Nurmiyeva, 2014). In the centers of invasion of mentioned species 110 complete geobotanical descriptions of communities on trial platforms of 4–100 m² were executed. Classification of communities with the invasive species is carried out according to the Braun-Blanquet method with application of the deductive method (Kopečky, Hejny, 1974). The allocated syntaxa were compared to units earlier described in Bashkortostan Republic and other regions (Vegetace …, 2009; Yamalov et al., 2012; etc.).

For the first time, Cyclachaena xanthiifolia was recorded in 1999 in the Kuyurgazinsky region in the southwest of Bashkortostan Republic. Nowadays over 70 centers of invasion of this species in the Cisural and Transural parts of region investigated are revealed. Communities with Cyclachaena xanthiifolia include Ivaetum xanthiifoliae Fijałkowski association with two variants (typica and Onopordum acanthium) and derivate community Cyclachaena xanthiifolia [Stellarietea mediae/Bidentetea tripartitae] as a part of class Stellarietea mediae R. Tx. et al. ex von Rochow 1951.

In the South Urals species of genus Xanthium L. are known since the end of the XIX century. Until the beginning of the XXI century two species of genus — X. strumarium L. and X. albinum were did not recognized as separate species. In recent years in the territory of Bashkortostan Republic X. strumarium was not found, thus all vegetation descriptions belong to communities with participation of X. albinum. Two derivate communities: Xanthium albinum [Stellarietea mediae] as a part of the class Stellarietea mediae R. Tx. et al. ex von Rochow 1951 and Xanthium albinum [Potentillion anserinae/Bidentetea tripartitae] as a part of the class Molinio-Arrhenatheretea R. Tx 1937 were revealed.

Ecological spectrum of communities with a presence of invasive species from genus Cyclachaena and Xanthium is wide and it includes the communities of different moistening regime — from wet floodplain communities to dry steppes of the Trans-Urals and the communities different succession stages — from pioneer one-year communities to grassland communities. The invasive species penetrate synanthropic, semi-na­tural and natural communities and in many cases they replace the native species forming new communities with dominance of alien species.