New locality of downy willow scrubs (Carici aquatilis-Salicetum lapponum Taran 1993, Alnetea glutinosae) in Western Siberia

We revealed a new locality of willow scrubs dominated by Salix lapponum L. in the Yagmunyagun River floodplain, 37 km east of Surgut city, 61°19'23''N, 74°12'01''E, Surgut district of Khanty-Mansi Autonomous Okrug, Russia. The aim of this paper is to give detailed syntaxonomical and landscape characteristic for the original plant communities scantily reported in geobotanical literature. The study area is located in the middle taiga subzone. In geomorphological respect, the Yagmunyagun floodplain occupies surfaces of the ancient meander belt of the Ob holocene terrace. In hydrological respect, it is a combined floodplain of 3 rivers: the Ob, the Tromyogan and the Yagmunyagun. The Yagmunyagun key plot area equals 162.4 ha. The main elements of its phyto-geomorphological structure are: downy willow scrubs - 43.4% (70.4 ha), swampy meadows and fens - 30.8% (50.1 ha), wet birch forests - 7.7% (12,5 ha); lakes and channels - 14.9% (24.2 ha); sandy embankments under a road and industrial object -3.2% (5.2 ha). According to Braun-Blanquet classification, the Yagmunyagun downy willow scrubs belong to the association Carici aquatilis-Salicetum lapponum Taran 1993 (Salicion cinereae Th. Mtiller et Gors ex Passarge 1961, Salicetalia auritae Doing 1962, Alnetea glutinosae Br.-Bl. et Tx. ex Westhoff et al. 1943). The willow scrubs are divided into 2 subassociations: C. a.-S. L typicum Taran 1993 (var. Carex lasiocarpa) and Carici aquatilis-Salicetum lapponum juncetosum filiformis Taran, Tyurin et Dyachenko subass. nov.; diagnostic species of the latter are Juncus filiformis, Gentiana pneumonanthe and Phalaroides arundinacea. The willow scrubs of Carici aquatilis-Salicetum lapponum juncetosum filiformis are formed on the meadow-boggy peaty soils and located on flood levels of 90-95% probability. Mean willow height in C. a.-S. l juncetosum filiformis coenoses is 1.5 m, mean total projective cover of the willow -24%, field layer - 48% and ground-layer mosses - 17%. Mean species saturation of the coenoses with vascular plants is 20.5, with mosses - 10.6 species per 100 m. In field layer of 8 releves of C. a.-S. l juncetosum filiformis coenoses, 11 species of vascular plants are noted with the greatest summary projective cover: Calamagrostis purpurea -119, Comarumpalustre - 88, Sanguisorba officinalis - 48, Carex acuta - 32, Phalaroides arundinacea - 24, Naumburgia thyrsiflora - 20, Juncusfiliformis - 18, Galium palustre -18, Galium boreale - 12, Carex aquatilis - 10, Agrostis stolonifera - 10%. The most abundant species in ground layer of the subassociation coenoses are Drepanocladus aduncus, Pohlia nutans, Calliergonella lindbergii, Polytrichum commune and Calliergon giganteum. In all 9 releves of the Yagmunyagun downy willow scrubs, we revealed 44 species of vascular plants, 1 species of liverworts and 27 species of mosses, including Sphagnum inundatum, new for moss flora of Khanty-Mansi Autonomous Okrug. Eight moss species (Amblystegium serpens, Bryum creberrimum, Ceratodon purpureus, Fontinalis hypnoides, Leskea polycarpa, Polytrichum juniperinum, Sphagnum centrale, Sphagnum inundatum) found in the Yagmunyagun downy willow scrubs are new for bryoflora of Carici aquatilis-Salicetum lapponum. Taking into account our results obtained in Western Siberia earlier, now Carici aquatilis-Salicetum lapponum bryoflora numbers 4 species of liverworts and 46 ones of mosses.

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