Association Carici juncellae-Salicetum rosmarinifoliae (Alnetea glutinosae) on the south taiga section of the Ob River floodplain

The Carici juncellae–Salicetum rosmarinifoliae Korolyuk et Taran in Taran 1993 association (Salicion cinereae, Salicetalia auritae, Alnetea glutinosae) includes the communities of the shrub (Salix rosmarinifolia, S. cinerea)-birch (Betula pubescens) tussock (Carex juncella, C. cespitosa) mires spread on the big West Siberian river floodplains within the taiga zone. On the Ob River, the association is represented by the C.j.–S.r. spiraeetosum salicifoliae Taran 1993 subassociation. Its range covers the Ob floodplain 830-kilometer distance crossing the subtaiga, south taiga and middle taiga subzones of Western Siberia. In the south taiga subzone (surroundings of the former village Kaibasovo, Krivosheinskiy district of Tomsk Region, 57º14'44"N, 84º11'05"E), the C.j.–S.r. spiraeetosum salicifoliae subassociation is studied for the first time. Near the Kaibasovo, the subassociation is represented by two facies: shrubby (Spiraea salicifolia, Salix rosmarinifolia, Salix cinerea) and birch (betulosum pubescentis). The communities of these facies found some floristic differences, which made it possible to attribute them to different variants: var. Cicuta virosa and var. Kadenia dubia. Carex juncella, C. cespitosa and Comarum palustre dominate in the field layer of the tussock mires. In the C.j.–S.r. spiraeetosum salicifoliae subassociation communities near the Kaibasovo, the average total projective cover (TPC) of the tree layer is 7%, shrubs – 34%, grasses – 48%, tussocks – 20%, ground mosses – 14%. Average tussock height is 59 cm. Average species saturation of the communities is 27 species of vascular plants and 18 species of mosses per 100 m², the volume of the local coenoflora is 39 species of vascular plants and 28 species of mosses. Six moss species (Brachytheciastrum velutinum, Bryoerythrophyllum recurvirostrum, Bryum moravicum, Fissidens bryoides, Plagiomnium cuspidatum, Pylaisia selwynii) were found in the Ob communities of the C.j.–S.r. spiraeetosum salicifoliae for the first time. Due to this, the total volume of the moss flora of the subassociation Ob stands increased to 74 species. The analysis of the variability of the main coenotic and floristic parameters of the C.j.–S.r. spiraeetosum salicifoliae subassociation in the geographical space of the Ob floodplain (from the subtaiga subzone to the middle taiga one) is carried out. The main regularities of these shifts are revealed. The volume of the subassociation local vascular coenoflora (52-53 species) and average species saturation of the communities by vascular plants (20-21 species per 100 m²) are stable on the most of the Ob floodplain sections. At the same time, changes are observed downstream of the Ob River, which can be interpreted as an intracoenotic response of the subassociation communities to smooth changes in the ecological regime of the floodplain when moving in geographical space from south to north. Thus, from the south to the north, many average parameters increase in the subassociation communities, namely: the height of trees, TPCs of tree layer, tussocks and ground mosses, the species saturation with mosses (from 4 to 18 species per 100 m²). The species richness of local moss floras also increases from 11 to 54 species. On the contrary, the average TPCs of shrub and field layers from south to north decrease. A number of deviations from general trends were found in the Kaibasovo birch-shrub tussock mires, namely: high species saturation with vascular plants (27 species per 100 m²), low reach of vascular coenoflora (39 species). The first can be explained by the proximity of the studied mires to the Ob riverbed, the second – by the crowding of the relevés in a relatively small area of the floodplain.