Floristic diversity of meadow and steppe vegetation to the east of the Ob River

Forest-steppe landscapes of Siberia are characterized by a high diversity of flora and plant communities. The zonal vegetation of piedmont forest-steppe to the east of the Ob River is represented by meadow steppes, xeric meadows and small-leaved forests. Various ecological-coenotic groups of species form these communities and indicate different ecological conditions as well as an anthropogenic impact. Correctly identified ecological-coenotic groups can be used in vegetation classification, assessment of ecological characteristics of habitats, and communities genesis. The aims of our study were: (1) a formalized analysis of geobotanical releves of steppe and meadow vegetation and the identification of ecological-coenotic groups of species for piedmont foreststeppe landscapes to the east of the Ob River; (2) characterization of plant communities with high syntaxonomical rank using distinguished ecological-coenotic groups. Our research was carried out in Novosibirsk region to the east of the Ob River between its valley and the Salair Ridge (53°30'N - 55°N, 81°30'E - 84°E) (See Fig. 1). 505 releves were selected for further analysis, 352 were sampled by the authors of the paper, and 153 were taken from literature [Makunina and Mal'tseva 2008; Dymina 1989 ; Makunina et al. 2010]. Each releve was assigned to the high rank syntaxa (class, order, alliance). Using IBIS 7.2, a table was prepared, which was processed in JUICE 7.0 using Modified TWINSPAN Classification. For all types of communities, lists of indicator species with occurrence and importance values were compiled. To distinguish differential species, the formal criteria were used [Dengler et al., 2005; Michl et al., 2010]. To assess the environmental characteristics of habitats, indicator values for species on ecological gradients (pasture digression, soil richness-salinity and moisture, tolerability for hemeroby) were used. Four types of plant communities were identified using cluster analysis (See Fig. 2). A synoptic table was built taking into account the constancy and importance value of species (See Table). On the basis of formal analysis of the releves, 8 ecological-coenotic groups were identified, including 93 species in total (27% of the total flora of the steppe and meadow vegetation of the studied region). All of them have an indicator or differential significance. To determine the leading environmental factors in the differentiation of vegetation, indicator values of plants and DCA-ordination were used. For each releve its position on four gradients was calculated: soil moisture, tolerability for hemeroby, soil richness-salinity and pasture digression. An analysis of Pearson's correlation between the position of the releves on ecological gradients and on the first three axes of DCA-ordination showed that the first two factors play a leading role in the differentiation of vegetation. On the gradient of soil moisture, all releves were divided into steppes, steppe meadows and forest meadows. The second factor is responsible for the difference between communities of pastures and fallows on one side and natural or slightly transformed steppes and meadows on the other. Four generalized types of plant communities were identified using cluster analysis. The first cluster represents steppe vegetation. Members of 1, 5 and 6 ecological-coenotic groups take part in the steppe coenoflora (See Table). This coenoflora includes 11 species with a high importance value, among which are the common steppe dominants Stipa capillata and Artemisia glauca. Another four plants are dominants and co-dominants: Medicago falcata, Stipa pennata, Poa angustifolia, Fragaria viridis. The analyzed communities occupy the driest position on the moisture gradient: 52-53 gradations on average (See Fig. 3). The second cluster represents xeric meadows and meadow steppes that dominate in foreststeppe landscapes. These are rich multi-dominant communities that are characterized by a large group of plants with a high importance value. The basis coenoses are formed by common mesoxeric meadow-steppe and meadow plants: Fragaria viridis, Calamagrostis epigeios, Poa angustifolia, Filipendula vulgaris, Dactylis glomerata, Peucedanum morisonii, Phlomoides tuberosa, Brachypodium pinnatum, Medicago falcata, Iris ruthenica, Seseli libanotis, Stipa pennata, Vicia amoena, Centaurea scabiosa and Artemisia latifolia. Representatives of 2, 5-8 ecological-coenotic groups actively participate in the formation of coenoflora (See Table). Steppe meadows and meadow steppes are the most heterogeneous type of communities. On the moisture gradient they are located between steppes and forest meadows (average moisture gradations are 57-58). The third community type combines transformed variants of meadow vegetation: pastures and fallows. Phytocoenoses are characterized by multidominance and an approximately equal ratio of rhizome grasses (Dactylis glomerata, Poa angustifolia, Festuca pratensis, Phleum pratense, Elytrigia repens, Bromopsis inermis) and perennial herbs (Fragaria viridis, Filipendula vulgaris, Medicago falcata, Amoria repens, Trifolium pratense, Taraxacum officinale). 3, 6, and 8 ecological-coenotic groups actively participate in the species composition of transformed meadows (See Table). This type of communities is well separated on the gradient of tolerability for hemeroby, while according to moistening conditions it corresponds to xeric meadows (See Fig. 3). The fourth type represents forest meadows. Coenoses are multi-dominant with many abundant and constant species. Among them prevail perennial herbs: Filipendula ulmaria, Aegopodium podagraria, Heracleum dissectum, Pteridium aquilinum, Cirsium setosum, Urtica dioica, Rubus saxatilis, Anthriscus sylvestris, Crepis sibirica and Bupleurum longifolium. Usually, rhizome grasses are the main codominants: Bromopsis inermis, Brachypodium pinnatum, Calamagrostis epigeios and Poa angustifolia. Species from 4, 7, and 8 ecological-coenotic groups form this type of communities (See Table). On the moisture gradient, forest meadows occupy wet parts: 62 gradations on average. The described types of communities can be used both in the dominant classification and in syntaxonomy. The indicator and differential species allow to detail the phytocoenotic diversity of vegetation, its spatial patterns and dynamics. The paper contains 3 Figures, 1 Table and 19 References. The Authors declare no conflict of interest.

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