The paper presents floristic and geo-botanical characteristics of rare forest ecosystems of the south of Western Siberia -spruce forests on the site of the Ob river ancient bed within the modern Bolshaya Sogra within the boundaries of the state natural reserve 'Kislukhinsky' (Altai region). Spruce forests here are at the edge of their spread in the West Siberian Plain conditions. There are over 300 species of vascular plants found in these spruce forests. Among them are plants that are typical of the mountain taiga associations of Russian Altai, as well as orchids, which have high species diversity. Spruce forest set of associations is also varied. The uniqueness of the described communities to the south of Western Siberia, the large number of rare and endangered plant species listed in the Red Books of different ranks, as well as the boreal forest species complex rare to the lowland wooded steppe, which has a relict character, all served as the basis for allocating a special protection area in the 'Kislukhinsky' reserve and attributing the studied spruce forests to the forests of high conservation value.

The syntaxonomic analysis of pine forests with Acer negundo occurring on fluvio-glacial sandy deposits of Altai Krai (South-East Siberia) was made based on 93 releves. It was established that Acer negundo takes a different phytocenotic part in 2 associations, 2 variants, and 6 no-ranked communities of 4 classes and 4 orders according to the Braun-Blanquet approach. The method of detrended correspondence analysis (DCA coordination) implemented in the DECORANA software package was used to confirm the ecological and floristic integrity of the identified vegetation units. New data on the spatial syntaxa distributions depend on the complex humidity gradient, soil fertility, and anthropogenic factors. Acer negundo is most abundant and common in the communities of the Brachypodio-Betuletea pendulae class, which are characterized by habitats with moderate moistening and greater soil fertility. In the spatial series considered, according to the soil fertility and humidity gradients, we observe an increase in Acer negundo in the Vicia sylvatica – Pinus sylvestris community and an increase in the activity of mesophytes and mesohygrophytes that are more demanding to soil fertility.

Elaeagnus angustifolia L. (Russian olive) is a deciduous small tree or large multi-stemmed shrub that becomes invader in different countries all other the world. It is potentially invasive in some regions of Russia. In the beginning of 20th century, it was introduced to the steppe region of Altai Krai (Russia, southwestern Siberia) to prevent wind erosion. During last 20 years, Russian olive starts to create its own natural stands and to influence on native vegetation. This article presents the results of eco-coenotic survey of natural plant communities dominated by Elaeagnus angustifolia L. first described for Siberia and the analysis of their possible syntaxonomic position. The investigation conducted during summer season 2012 in the steppe region of Altai Krai allows revealing one new for Siberia association Elytrigio repentis–Elaeagnetum angustifoliae and no-ranged community Bromopsis inermis–Elaeagnus angustifolia which were included to the Class Nerio–Tamaricetea, to the Order Tamaricetalia ramosissimae. During the study, the following special features of communities have been described: polydominance of herbal layer, anthropogenic and grazing load, variation of the species richness, plant cover and vertical stratification into layers. These peculiarities mostly prove unestablished character of communities, all of them are relatively young (25–30 years). Russian olive shrubberies varies in moisture and saline regime, which connected with their existence in different landforms (lake alluvial plains, gentle slopes of lakes, low lake terraces).

Ash-leaved maple is one of the most aggressive alien species in most Russian regions. It was first brought to the Altai Krai in 1933. For a long time, maple had been used in the urban and village greenery planting and tree belt areas. Nowadays, it is actively settling along riverbanks, roadsides, abandoned lands, etc. Ash-leaved maple is a danger as a transformer species, preventing the pine’s reproduction in the unique natural communities – ribbon pine forests. We studied the state of the Acer negundo L. populations as a transformer species in the Barnaul ribbon pine forest. The maple population status was assessed by the transect method at the selected registration sites. The age of plants was determined by the method of T. A. Rabotnov. The first ordered branches were used for a more detailed characterization of the maple populations. The introduction of maples into the Pinus sylvestris L. communities is associated with a significant anthropogenic impact on the natural communities of the ribbon pine forest. There are pure maple communities formed in some places in the northern part of the ribbon pine forest. Throughout the Barnaul ribbon pine forest, the maple populations are normal and invasive only in the south part. The first-ordered maple branches in the southern part of the ribbon pine forest have signs of apex change associated with adverse ecological factors. The development indicators of maple trees along the entire ribbon pine forest were evaluated for the first time. The results indicate the high adaptability of maple to various ecological factors.

The article shows a variety of ordination methods used to analyze different types of vegetation and presents the results of the ordinal analysis of meadow (i.a. idle lands) and steppe phytocenoses that are widespread in Altai Krai. Ecological ordination is performed by means of the Detrended Correspondence Analysis (DCA) method. The ordination of grass communities is based on 616 complete geobotanical descriptions (330 - meadow, 286 - steppe). The article determines the position of community types on the gradients of humidification and soil richness-salinity for steppes and suggests the directions of the progressive successions of idle land communities in Altai Krai.