Pine forests of the steppe and forest-steppe zones of West-Siberian plain (Ob-Irtysh watershed) represent a unique natural phenomenon. They form anomalously large continuous forest massifs (pine forest strips) on sand deposits in ancient ravines. These forests contrast sharply with the steppe and forest-steppe surroundings, both in the set of plant communities and in species composition. Meadow communities form a narrow belt along the periphery of pine forest strips (Lashchinsky et al., 2018).
The studied Kulunda and Kasmala (Fig. 1) pine forest strips are situated in the south-eastern part of West-Siberian plain (52°35′–53°25′ N and 81°10′–83°15′ E) within the forest-steppe zone (Kuminova et al., 1963; Pavlova, 1963). A data set comprising 105 relevés of meadows was classified using TWINSPAN algorithm in Juice (Tichý, 2002), and followed by manual re-arrangement. Cluster analysis of associations was used to determine the main geographical and ecological patterns in meadow vegetation (Fig. 2).
Traditionally, meadows are attributed to the class Molinio-Arrhenatheretea R. Tx. 1937. In the last decades, the concept of the class Festuco-Brometea has been changed (Mucina et al., 2016; Willner et al., 2017). In the modern interpretation, the order Brometalia erecti Koch 1926 unites the most mesophytic communities of the class. In this case, the Siberian syntaxa, which previously were considered as the order Festucetalia valesiacae, and some associations of the order Galietalia veri (Molinio-Arrhenatheretea) should be referred to the order Brometalia erecti of the class Festuco-Brometea.
The syntaxonomical diversity of meadow vegetation of Kulunda and Kasmala forest strips is represented by two classes, three orders, three alliances, four associations, three subassociations and one community (Table 1).
Ass. Peucedano morisonii–Festucetum valesiacae Tishchenko 2018 subass. P. m.–F. v. gypsophiletosum paniculatae subass. nov. hoc loco (Table 2, holotypus — relevé 1 (mr17-071): Altai Territory, Romanovskiy district, 6 km to the W from Guseletovo village, N 52.61063°, E 81.46572°, 25.07.2017. Author — M. P. Tishchenko) unites xeric meadows on slightly saline soils, which were found only in transition between the steppe and forest-steppe zones in southern part of the surveyed territory in the southern part of Kasmala strip (Fig. 3, 1). Specific features of their composition is the high constancy of mesoxerophytic species common in meadow steppes (Artemisia dracunculus, A. glauca, Peucedanum morisonii, Spiraea crenata, Stipa pennata, Veronica spuria, etc.).
Ass. Echio vulgaris–Poetum angustifoliae ass. nov. hoc loco (Table 3, holotypus — relevé 1 (mr17-027): Altai Territory, Tyumentsevskiy district, surroundings of Voznesenskiy village, N 53.21215°, E 81.72828°, 21.07.2017. Author — М. P. Tishchenko) represents the widespread xeric meadows on sandy soils at the edges of pine forest strips in the all studied territories (Fig. 3, 2, 3). These communities, which contain both meadow and steppe species, are used as pastures, so there is a lot of ruderal plants (Cynoglossum officinale, Echium vulgare, Erigeron acris, Nonea rossica, Senecio jacobaea) in diagnostic combination. Due to the different positions on moisture gradient two subassociations are distinguished: more mesic E. v.–P. a. typicum subass. nov. hoc loco (Table 3, rel. 1–18) and more xeric E. v.–P. a. caricetosum ericetorum subass. nov. hoc loco (Table 3, rel. 19–36; holotypus — relevé 20 (mr17-011): Altai Territory, Shelabolikhinskiy district, near Baturovo village, basin of the Kuchuk river, N 53.40929°, E 82.36375°, 18.07.2017. Author — М. P. Тishchenko).
Ass. Campanulo bononiensis–Dactylidetum glomeratae ass. nov. hoc loco (Table 4, rel. 1–6; holotypus — relevé 4 (mr17-104): Altai Territory, Pavlovskiy district, 6 km to the W from Kasmala village, N 53.42048°, E 83.17238°, 29.07.2017. Author — М. P. Тishchenko) unites rare forest meadows (usually secondary) of the order Carici macrourae–Crepidetalia sibiricae, which occur on the wet edges of pine and birch-pine forests (Fig. 3, 4).
In low depressions on the transition between forests and wetlands (Fig. 3, 5) on slightly saline soils there are wet meadows (the order Molinietalia) of ass. Heracleo sibirici–Festucetum pratensis ass. nov. hoc loco are found (Table 4, rel. 7–17; holotypus — relevé 7 (mr17-020): Altai Territory, Rebrikhinskiy district, near Ust-Mosikha village, valley of the Kulunda river, N 53.25558°, E 81.98389°, 20.07.2017. Author — М. P. Тishchenko). The tall-grass hay meadows with high constancy of mesophytic meadow and forest plants are within this syntaxon. These habitats are indicated by the presence of halotolerant plants (Cenolophium denudatum, Hordeum brevisubulatum, Plantago cornuti, Cirsium canum, Galatella biflora).
The community Agrostis gigantea–Cirsium esculentum unites grazing meadows, that are differentiated by the occurrence of Agrostis gigantea, Artemisia laciniata, Cichorium intybus, Cirsium esculentum, Melilotus dentatus, Senecio erucifolius, Sonchus arvensis (Table 4, rel. 18–21; Fig. 3, 6).
The cluster analysis of the associations representing steppes and xeric meadows of the southeastern part of West Siberia revealed two important facts. All associations were clearly spitted into two clusters, which represent the classes Molinio-Arrhenatheretea and Festuco-Brometea. Within the second cluster, the associations representing the steppe meadows of Kulunda and Kasmala pine forest strips were separated. This demonstrates that these communities differ from meadows and steppes representing alliances Carici supinae–Stipion zalesskii Korolyuk 2017 all. prov., Sileno borysthenicae–Cleistogenion squarrosae Korolyuk 2017, Helictotricho desertorum–Stipion rubentis Toman 1969 and Galatellion biflorae Korolyuk 1993. This suggests the possibility to describe new high rank syntaxa for meadows on sandy soils in the forest-steppe zone on West-Siberian plain, however new data from other regions are needed.
Successions of microbiotic communities of sandy soils in pine stands of different ages in the forest-steppe zone