Vegetation of the floodplains of the rivers Vychegda and Pechora. The class Phragmito–Magno-Caricetea Klika in Klika et Novák 1941

The present study continues a series of publications by the authors on the diversity of the herb vegetation in the floodplains of the Vychegda and Pechora rivers and their tributaries (Komi Republic). The floristic classification of the orders Molinietalia Koch 1926 and Arrhenatheretalia R. Tx. 1931 was published earlier (Shushpannikova, Yamalov, 2013, 2014). The results of classification of communities belonging to the class Phragmito–Magno-Caricetea Klika in Klika et Novák 1941 are discussed in this paper in accordance with principles of the Braun-Blanquet approach (Braun-Blanquet, 1964; Mirkin, Naumova, 1998). Analysis was based on 268 relevés made in 1981–2016. The assessment of environmental parameters was performed by ecological methods by L. G. Ramensky (Ramensky et al., 1956). Syntaxonomic diversity of the vegetation of the class Phragmito–Magno-Caricetea in the floodplain of rivers Vychegda and Pechora is presented by 3 orders (Phragmitetalia W. Koch 1926, Oenanthetalia aquaticae Hejny in Kopecky et Hejny 1965 and Magno-Caricetalia Pignatti 1953), 4 alliances (Phragmition communis W. Koch 1926, Nardosmion laevigatae Klotz et Köck 1986, Equisetion arvensis Mirkin. et Naumova in Kononov et al. 1989 emend. Taran 1995 and Magnocaricion elatae Koch 1926) and 13 associations. The communities of the class Phragmito–Magno-Caricetea, as well as the order Molinietalia of Molinio–Arrhenatheretea, are located at all levels of the floodplains and are characterized by a variety of humidification conditions. However, the communities of the class Phragmito–Magno-Caricetea are characterized by higher humidification indices (72.2–86.3) compared to meadow vegetation the order Molinietalia of the class Molinio-Arrhenatheretea of (68.8–74.4). A lot of associations, heterogeneous in their floristic composition, can be divided into 9 subassociations and 10 variants. New 4 subassociations (caricetosum vesicariae, equisetosum fluviatilis, persicaretosum amphibiae and lysimachetosum vulgaris), are included into ass. Caricetum gracilis Savich 1926. The peculiarities of the floristic composition of the above mentioned associations, as well as their distribution and ecology are discussed. The distinguished associations are well differentiated by their elevation position on the floodplains. The communities of the ass. Caricetum gracilis are located at all levels of the floodplainons; these of Agrostio stoloniferae–Equisetetum arvensis — on the highest ones; Equisetetum fluviatilis — on the lowest part of the floodplains in the riparian zone. The described communities are located on the soils with various ecological indi­cators. The distinguished associations are differentiated by the levels of humidification (65.9–89.9), mean figures — 70.3–86.3. The communities of the ass. Agrostio stoloniferae–Equisetetum arvensis occupy the driest sites (65.9–72.9); these of associations ­Equisetetum fluviatilis and Nardosmietum laevigatae — the wettest ones (80.7–87.8). The ass. Caricetum aquatilis has a wide range of humidification (72.7–89.9). The variability of humidification varies from alternating to high values (6.4–12.0). The ­greatest differences in humidification are experienced by the communities of the ass. Caricetum gracilis (5.5–12.0). Тhe communities of the ass. Agrostio stoloniferae–Equisetetum arvensis occupy the richest (10.5–15.0) and alluvial soils (4.0–5.0). They are located on the low level in the riverine and middle zone of the floodplain and are formed by annual flooding on alluvial deposits. The distinguished associations are differentiated by pH (3.0–8.0), mean figures — 4.5–7.0. The communities of the associations Caricetum juncellae, Caricetum gracilis and Caricetum acutae–rostratae are located on the most acidic soil; these of the ass. Equisetetum fluviatilis — on the neutral ones. The associations are distributed by the scale of pasture digression in range 2.5–4.5, mean figures — 3.0–3.9. The communities are used for hay-making. The question of the boundary between the meadow vegetation, lowland swamp and semi-aquatic vegetation remains unsolved. The communities of the class Phragmito–Magno-Caricetea described in this paper belongs to meadows. Ass. Nardosmietum laevigatae (previously referred to the class Galio-Urticetea Pass. 1967) is included into the order Phragmitetalia W. Koch 1926. The communities of the ass. Agrostio stoloniferae–Equisetetum arvensis have a mesophilic species composition and low moisture values, so they represent a transition between the class Molinio-Arrhenatheretea order Molinietalia and class Phragmito–Magno-Caricetea. A comparison of species composition of the syntaxa in Komi Republic and that in other regions of the Eastern Europe and the Asian part of Russia showed that the semiaquatic communities of the Komi Republic have low species diversity. It is less than 16 species on sample plot. The richest are communities of the associations Caricetum gracilis and Carici acutae–Phalaroidetum arundinaceae. 101 vascular plant species are recorded in 268 geobotanical relevés of the class Phragmito–Magno-Caricetea. The aboveground phytomass varies from 30–80 g/m2 (Agrostio stoloniferae–Equisetetum arvensis) to 420 г/м2 (Phalaroidetum arundinaceae).