The synthaxonomy and ecology of communities with predominance of Hordeum jubatum L., included in the «black list» of the Republic of Bashkortostan (Abramova, Golovanov, 2016a), the preliminary «black list» of the Orenburg Region (Abramova et al., 2017) and the «Black book of flora of Middle Russia» (Vinogradova et al., 2010), are discussed in the article, which continues a series of publications on the classification of communities with alien species in the South Urals (Abramova, 2011, 2016; Abramova, Golovanov, 2016b).
H. jubatum was first found in the South Urals in 1984 as an adventive plant occurring along streets in the town of Beloretsk, as well as in gardens where it was grown as an ornamental plant. During the 1980s, it was met also at some railway stations and in several rural localities. Its active distribution throughout the South Urals started in XXI century (Muldashev et al., 2017). Currently, H. jubatum, most naturalized in the native salted habitats of the steppe zone, is often found in disturbed habitats in all natural zones within the region. The short vegetating period and resistance to drought allowed it to be naturalized also in dry steppes, where it increasingly acts as the main weed on broken pastures.
The aim of the work, conducted during 2011–2017, was further finding the centers of H. jubatum invasion in 3 regions adjacent to the South Urals — the Republic of Bashkortostan and the Chelyabinsk and Orenburg Regions (Fig. 1). In the main sites of H. jubatum invasion 71 relevès were performed on 10–100 m² sample plots with the information of location, date, the plot size, the total cover, average and maximum height of herb layer. Classification was carried out following the Braun-Blanquet method (Braun-Blanquet, 1964) with using the Kopecký–Hejný approach (Kopecký, Hejný, 1974).
The community ecology was assessed by weighted average values according to the optimal ecological scales by E. Landolt with usfge of the software of IBIS (Zverev, 2007). PCA-ordination method with usage CANOCO 4.5 software package was applied to identify patterns of environmental differentiation of invasive communities.
The current wide distribution area of H. jubatum and its naturalization in synanthropic, meadow and saline communities in the South Urals, as well as its occurrence within mountain-forest belt, forest-steppe and steppe zones both in the Cis- and Trans-Urals, indicates species wide ecological amplitude, high adaptive capability and invasive potential. Its vast thickets are known in the steppe zone, both in disturbed steppes around settlements and along the banks of water bodies. The invasion sites are smaller in the northern regions and mountain forest belt, where these are located in settlements or along communication lines. Therefore, the steppe zone is more favorable for invasive populations, and their distribution will continue from the south to the north.
Communities with predominance of H. jubatum, described earlier (Abramova, Golovanov, 2016b) in the Cis-Urals as two derivative communities (associations Hordeum jubatum [Scorzonero–Juncetea gerardii], Hordeum jubatum [Artemisietea]) and Polygono avicularis–Hordeetum jubati, were met in other regions of the South Urals. Also a new derivative community Hordeum jubatum–Poa pratensis [Cynosurion cristati], occuring in the northern part of the Cis-Urals and Trans-Urals, was established.
In new habitats this species forms three types of communities: ass. Polygono avicularis–Hordeetum jubati (Fig. 2) the most widespread in anthropogenic habitats throughout the South Urals; derivative community Hordeum jubatum–Juncus gerardii [Scorzonero–Juncetalia gerardii] (Fig. 5) which replaces saline meadows mainly in the steppe zone of the region; derivative community Hordeum jubatum–Poa pratensis [Cynosurion cristati] (Fig. 4) which y replaces low-herb meadows in the forest-steppe zone and mountain-forest belt.
PCA ordination (Fig. 6) shows that moisture (H) and soil richness-salinization (S) factors are in priority in differentiation of communities with predominance H. jubatum. The first axis is mainly related to the salinization and soil richness. The community pattern along the second axis is associated with wetting factor.
The cenoses of the derivative community Hordeum jubatum–Poa pratensis [Cynosurion cristati] (less salted substrates in drier conditions in the northern part of the forest-steppe zone and the mountain forest belt) are grouped in the upper part of the ordination diagram, while communities of ass. Polygono avicularis–Hordeetum jubati (drier conditions in settlements, the steppe zone) in its low left part. Thus, axis 1 also reflects the intensity of trampling. Another group is formed by cenoses of the derivate community Hordeum jubatum–Juncus gerardii [Scorzonero–Juncetalia gerardii], (salt substrates with a high level of moisturization, on not very damaged water body banks). All communities with H. jubatum are well differentiated in the space of the main ordination axes that indirectly confirms the correctness of our syntaxonomic decision.
Undoubted is further expansion of H. jubatum with its entering both anthropogenic and natural plant communities within the South Urals that suggests a constant monitoring in centers of species invasion.
Climate-Driven Holocene Migration of Forest-Steppe Ecotone in the Tien Mountains