The West-Siberian Plain extends more than 1200 km from west to east. Its southern part is occupied by steppe and forest-steppe zones with pre-dominance of herbaceous plant communities. Steppes and xeric meadows are widespread on this territory and characterized by a high diversity and complex spatial structure.
This study presents the analysis of 874 relevés describing xeric meadows and steppes of the class Festuco-Brometea from the West Siberian Plain. Numerical analysis with using of plant indicator values showed that some ecological factors, such as soil moisture, salinity and sand content are important in differentiation of grasslands. Three zonal associations form the sequence on the latitudinal gradient from 56º to 51º of northern latitude: Galatello biflorae–Calamagrostietum epigeii (xeric meadows and meadow steppes on solonetz soils in forest-steppe zone), Helictotricho desertori–Stipetum rubentis (rich bunchgrass steppes of southern part of forest-steppe zone and northern part of steppe zone), Artemisio austriacae–Stipetum capillatae (typical bunchgrass steppes of steppe zone). Zonal associations form complexes with other grasslands of Festuco-Brometeae. In forest-steppe landscapes zonal communities usually adjoined with Galio borealis–Artemisietum ponticae in more mesic habitats and with halophyte association Limonio gmelini–Phleetum phleoides. In steppe regions zonal associations make an assemblage with relatively mesic grasslands of Trommsdorffio maculatae–Stipetum pennatae and halophyte communities of Limonio gmelini–Stipetum capillatae on solonetz soils. Three associations form the sequence related with increasing of sand content in soils: Gypsophilo paniculatae–Artemisietum glaucae, Sileno borysthenicae–Cleistogenetum squarrosae, Scorzonero ensifoliae–Festucetum valesiacae. All grasslands usually are under intense grazing that cause changes in plant communities, first of all, the reduction of meso-xerophyte species diversity. The class Festuco-Brometea in the West Siberian plain is divided into two orders. The order Festucetalia valesiacae unites xeric meadows and meadow steppes in forest-steppe landscapes. The class and order are diagnosed mainly by meso-xerophyte species with wide Eurosiberian distribution: Anemone sylvestris, Artemisia glauca, A. latifolia, Astragalus danicus, Campanula sibirica, Centaurea scabiosa, Dianthus versicolor, Festuca pseudovina, Festuca valesiaca, Filipendula vulgaris, Fragaria viridis, Galium ruthenicum, Galium verum, Koeleria cristata, Medicago falcata, Phleum phleoides, Phlomoides tuberosa, Plantago urvillei, Poa angustifolia, Polygala comosa, Scabiosa ochroleuca, Seseli libanotis, Stipa capillata, Stipa pennata, Tephroseris integrifolia, Trommsdorffia maculata, Veronica spicata. This order is presented by the alliance Galatellion biflorae located to the west from the Ob River (Korolyuk, Kiprijanova, 1998). Its communities differ from others by presence of salt-tolerant species: Artemisia pontica, Artemisia rupestris, Carex caryophyllea, Galatella biflora, Inula britannica, Melampyrum cristatum, Peucedanum morisonii, Plantago maxima, Silene multiflora. To the east from the Ob River this alliance is replaced by Poo urssulensis–Artemision glaucae, in the South Urals by Festucion valesiacae. The xeric meadows of Festuco-Brometea north from forest-steppe zone are replaced by mesic meadows of Molinio-Arrhenatheretea. The order Helictotricho-Stipetalia represents the typical steppes and xeric variants of meadow steppes. Its distribution covers steppe zone and southern part of forest-steppe zone. The main part of its diagnostic combination is formed by xerophyte steppe plants: Achillea nobilis, Adonis villosa, Androsace maxima, Artemisia austriaca, Carex supina, Galatella angustissima, Helictotrichon desertorum, Jurinea multiflora, Onosma simplicissima, Oxytropis pilosa, Pilosella echioides, Potentilla bifurca, P. humifusa, Salvia stepposa, Scorzonera austriaca, Seseli ledebourii, Spiraea crenata, Stipa zalesskii, Taraxacum erythrospermum, Thymus marschallianus, Verbascum phoeniceum, Veronica incana. Three alliances form the sequence along moisture gradient: more mesic rich steppes of Helictotricho desertori–Stipion rubentis (diagnostic species: Helictotrichon desertorum, Stipa zalesskii, Thymus marschallianus, Artemisia latifolia, Filipendula vulgaris, Fragaria viridis, Phlomoides tuberosa, Plantago urvillei, Seseli libanotis, Artemisia pontica, A. rupestris, Galatella biflora, Peucedanum morisonii, Silene multiflora), typical steppes of Artemisio austriacae–Festucion valesiacae (diagnostic species: Androsace maxima, Artemisia austriaca, Carex supina, Potentilla bifurca, Scorzonera austriaca, Taraxacum erythrospermum), and dry steppes of Stipion korshinskyi Toman1969 (diagnostic species: Kochia prostrata, Krascheninnikovia ceratoides, Leymus ramosus, Phlomoides agraria, Stipa korshinskyi, Stipa lessingiana).
Genesis problems of chernozems of the Galicia
