Сommunities of Myrica gale L. (sweet gale), their ecology and geography in coastal mires of the Gulf of Finland within St. Petersburg and the Leningrad Region on the Southeastern border of their range are described based on 70 relevés, made in 1981–2018. This species is included in the Red Data Books of Russia (2008), Leningrad Region (2018), St. Petersburg (2018), and Republic of Karelia (2007).
The distribution of the communities in the studied area is as follows (Fig. 1) — the Yuntolovskiy reserve (the largest population), vicinity of the Lisiy Nos settlement, forest-park “Gagarka”, Tarkhovskiy Mys, Yuntolovskiy forest-park (within St. Petersburg); vicinity of the Pesochnoe settlement, the Bolshoy Beryezovyy Isl., near the port “Primorsk” (the Northern coast of the Gulf of Finland) and the vicinity of Bolshaya Izhora settlement (Southern coast of the latter) in the Leningrad Region area. Communities are found mainly in coastal mires of various types (raised bogs, transitional mires, fens) in the place of former lagoons and in inter-dune depressions in different trophic conditions; most diverse in the last two. Communities are assigned into 12 associations, two of which with the shrub layer formed by Myrica gale.
Sphagnetum myricosum galis is the most common association in transitional mires (Table 3). The communities are two-layers: Myrica gale shrub one and closed moss layer of Sphagnum species of different ecological groups. The association is subdivided into 3 subassociations by dominanting Sphagnum species and groups of determinant species: sphagnosum angustifolii, sphagnosum flexuosi, and sphagnosum teretis. The communities of this association are located in newly formed mires, and their species composition is in the process of formation. These are succession stages between the fens and transitional mires.
The ass. Myricetum caricosum lasiocarpae (table 4) includes communities of fens with close (50 to 80 %) Myrica gale shrub layer. Carex lasiocarpa is the dominant of the herb layer, in some communities there is the lower herb sublayer of Comarum palustre. There is no moss layer. Association Myricetum comaroso–betulosum with sparse Betula pubescens 5–12 m high tree layer is also recorded in fens (Table 4).
Communities of the ass. Salicetum myricoso–paludiherbosum with the dominance of shrub willows and Myrica gale are rather widespread in coastal fens. They have closed (up to 100 %) shrub layer formed by various willows and M. gale. The composition and cover of paludal herbaceous species is variable, the only constant, sometimes abundant, species is Comarum palustre. The association is subdivided into 3 subassociations (salicosum phylicifoliae, salicosum phylicifoliae-myrsinifoliae and salicosum rosmarinifoliae-myrsinifoliae) according to the dominating willows and mire grasses.
Besides the above associations with high abundance of Myrica gale, this species occurs with low abundance in the communities of other, often widespread mire associations, as their coastal variants (Tables 2–4). The discussed community types in the Leningrad Region and St. Petersburg have regional features and differ in species composition from the sweet gale communities of Western and Northern Europe.
Due to the rarity in the European part of Russia communities with both low abundance and dominance of Myrica gale need protection as well as their habitats.
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