Syntaxonomy and ecology of the Moscow Region black alder communities

Alnus glutinosa is an European species with a wide range from the south of Scandinavia to the Mediterranean. However in many countries of Europe the areas of forests formed by black alder are scattered and often do not exceed 1–5 % of the forest cover due to both the small size of suitable ecotopes and their conversion to agriculture (Claessens et al., 2010). In the Moscow Region located in the center of the Russian Plain (Fig. 1), black alder forests also are about 5 % (Kotlov, Chernenkova, 2020) and have not been documented appropriately yet. Based upon 51 relevés two associations dominated by Alnus glutinosa from two vegetation classes were described using the Braun-Blanquet method. Ass. Urtico dioicae–Alnetum glutinosae Bulokhov et Solomeshch 2003 (class Alno glutinosae–Populetea albae Fukarek et Fabijanić 1968) (Bulokhov and Solomeshch, 2003; Semenishchenkov, 2016) includes floodplain hygro-mesophytic forests with nemoral species in herb layer (Table 1). This association is distributed in nemoral and broad-leaved coniferous zones of Eastern Europe. As a result of comparison with similar syntaxa from different regions of European Russia (Table 2) (Vasilevich, Stchukina, 2001; Sokolova, 2015; Semenishchenkov, 2016) its diagnostic species combination was enlarged by Impatiens noli-tangere, and new subassociation was described. Subassociation U. d.–A. g. athyrietosum filix-feminae Morozova et al. subass. nov. (Table 1, Fig. 2–4, nomenclature type (holotypus) — relevé 15 (author’s number serg-171a-14, Moscow Region, Sergiev Posad district, valley of a small river, author E. G. Suslova; diagnostic species: Angelica sylvestris, Athyrium filix-femina, Crepis paludosa, Deschampsia cespitosa, Oxalis acetosella, Padus avium, Rubus idaeus) unites the communities occurring in the floodplains of small rivers and relatively well-drained stream habitats in the broad-leaved coniferous zone and the southern taiga. Ass. Carici elongatae–Alnetum glutinosae Tx. 1931 (class Alnetea glutinosae Br.-Bl. et Tx. ex Westhoff et al. 1946) (Table 3, Fig. 5, 6) with variants typica and Menyanthes trifoliata comprises herb-swamp alder carrs growing mainly in depressions of the watershed area and ancient lake basins, as well as near swampy streams, i.e. in habitats of poor drainage of the territory (Table 4). Diagnostic combination of this association in Moscow Region includes Alnus glutinosa, Calla palustris, Caltha palustris, Carex appropinquata, Cicuta virosa, Equisetum fluviatile, Lycopus europaeus, Scirpus sylvaticus, Scutellaria galericulata, Solanum dulcamara. Dominant species are Filipendula ulmaria, Phragmites australis, Calamagrostis canescens, and Carex vesicaria; a microrelief formed by tussocks of sedges (Carex appropinquata, C. cespitosa) is common. Black alder forests of var. Menyanthes trifoliata are different in the set and sometimes dominance of species of mesotrophic bogs like Menyanthes trifoliata, Comarum palustre, Thyselium palustre, Thelypteris palustris and cover of mosses that on occasion can reach 80 %. The predominance of Alno glutinosae–Populetea albae species in first association and Alnetea glutinosae species in the second one is evident. A distinctive feature of the ass. Urtico dioicae–Alnetum glutinosae is relatively large proportion of nemoral species of the class Carpino-Fagetea (11.1 %) and small amount of wetland species of the class Phragmito-Magnocaricetea (3.5 %), these in the ass. Carici elongatae–Alnetum glutinosae, are 3.6 and 20.8 % respectively (Fig. 7). The floristic composition and structure of black alder stands depend on the hydrological regime and nutrient availability (Slezák et al., 2011), which are determined by the position of communities in the landscape. The most important factors were interpereted via vegetation using the method of Ellenberg ecological scales (Ellenberg et al., 1991) (Fig. 8). Нabitats of the ass. Urtico dioicae–Alnetum glutinosae are mesic to humid, rather rich and neutral in soil acidity, with poorly expressed microrelief, and with almost no tussock forming species. Such sites often occur in floodplains of small rivers (Table 4), which have a short flooding period (Braslavskaya, 2004), as well as on peat mining along the reclamation channels. Ass. Carici elongatae–Alnetum glutinosae occupies more wet waterlogged and acidic habitats and less rich ones (Fig. 9). Fluctuations in the groundwater level here are not so considerable, and the duration of flooding is longer due to the difficulty of flow and poor drainage of the territory (Döring-Mederake, 1990; Blagoveshсhinskii, 2018). A specific mircorelief is developped with water between sedge tussocks, the shape and height of which depend on the depth of flooding (Alekseyev, Abramova, 1980). Communities of the var. Menyanthes trifoliata occupy the poorest habitats among studied black alder forests. The distribution of Alnus glutinosa dominated forests in the Moscow Region is due to the landscape structure, which determines habitat environment. Ass. Urtico dioicae–Alnetum glutinosae are mainly distributed in the north of the study area (on the Upper Volga Lowland) and in the west (on the Moscow Upland), while herb-swamp alder carrs of ass. Carici elongatae–Alnetum glutinosae are more common on the lowlands: the Upper Volga in north and the Meshchera in the east. When the hydrological regime of the territory changes, a transformation of one syntaxon to another is possible, that, for example, was recorded in the Priokso-Terrasny Nature Reserve as a result of beaver activity (Andreeva, Mikaleva, 2012).