Communities of the class Oxycocco-Sphagnetea Br.-Bl. et R. Tx. 1943 in the East European tundras
Authors: Lavrinenko O. V. , Lavrinenko I. A. 
Published: February 2020

According to the tradition of the Braun-Blanquet school 3 new associations belonging to Oxycocco-Sphagnetea Br.-Bl. et R. Tx. 1943 class and Sphagnetalia magellanici (Pawl. 1928) Kдstn. et Flцss. 1933 order were described on the latitudinal gradient of the East European tundras. New ass. Carici globularis–Pleurozietum schreberi occurs on peaty gley soils of watersheds in the south part of tundra zone and in the northern forest-tundra. It is related to the Oxycocco–Empetrion hermaphroditi Nordh. 1936 alliance included the dwarf-shrub-Sphagnum communities of ridges and hummocks of the ombrotrophic raised bogs and aapa mires in subcontinental and continental areas of the taiga zone of the North Eurasia (Lapshina, 2010; Ermakov, 2012). Palsa peatlands are widespread in permafrost zone in the East European tundras. Shape and size of palsa mounds vary fr om the north to the southern direction. Polygon and small palsa peatlands are distributed in typical tundras (on the Barents Sea islands and coastal areas) in the continuous permafrost zone. The lowest flat palsa peatlands can be seen in the southern tundra in discontinuous permafrost zone. The high palsa peatlands and slightly differentiated peat plateau can be found in the northern forest tundra in the insular permafrost zone. All palsa peatlands have similar ecological features: oligotrophic, hyperacidity, closeness of permafrost, good drainage conditions and the dry upper layer of peat. The lichens (Cladonia and Flavocetraria genera) predominate in the ground layer of palsa peatlands. A role of Sphagnum moss is not remarkable, other mosses such as Dicranum elongatum and Polytrichum strictum dominate there. The new Rubo chamaemori–Dicranion elongati alliance are proposed to classify the dwarf-shrub-cloudberry-moss-lichen communities of oligotrophic palsa and polygon peatlands of the Subarctic region. Creation of the new alliance has some challenges: 1) the same vascular plants (Empetrum hermaphroditum, Ledum decumbens, Rubus chamaemorus, Vaccinium vitis-idaea, V. uliginosum) dominate on ombrotrophic raised bogs and aapa mires, but they are typical for palsa and polygon peatlands also; these species are listed already as character ones for existing higher syntaxonomic units, including Oxycocco–Empetrion hermaphroditi alliance; 2) in the East European tundras, on palsa and polygon peatlands the dominating lichens (Oxycocco-Sphagnetea class) have the same high constancy and they are often abundant in Loiseleurio-Vaccinietea Eggler ex Schubert 1960 class communities, commonly grown in the sandy habitats, therefore they are not characteristic species for both classes. There are 18 species of lichens (Lavrinenko, Lavrinenko, 2013), including Cladonia arbuscula, C. rangiferina, Cetraria islandica, Flavocetraria nivalis, defining physiognomic similarity of plant communities on peaty and sandy soils. To solve the problem, we propose to distinguish a new Rubo chamaemori–Dicranion elongati alliance based on a combination of differentiating taxa (see Molenaar, 1976; Matveyeva, 2006) such as: Andromeda polifolia subsp. pumila, Betula nana, Cetraria islandica, Cladonia arbuscula, C. rangiferina, Dic­ra­num elongatum, Empetrum hermaphroditum, Fla­vocetraria nivalis, Ledum decumbens, Polytrichum strictum, Rubus chamaemorus, Vaccinium vitis-idaea, V. uliginosum. Among them following species Andromeda polifolia subsp. pumila, Dicranum elongatum, Ledum decumbens, Polytrichum strictum, Rubus chamaemorus are character selective regional species of the alliance. The syntaxonomic analysis was based on 185 relevйs made from 1997 to 2012 in 35 regions in the Timanskaya, Malozemelskaya and Bolshezemelskaya tundras as well as on Kolguev, Dolgyi and Vaigach Islands. Two associations (one of them is represented by 3 subassociations) were identified and described on the palsa peatlands. The plant communities of 3 syntaxa are spread in the typical tundra subzone: ass. Tephroserido atropurpureae–Polytrichetum stricti — in the northern strip of subzone, on polygonal peatlands on the Vaigach Isl., ass. Rubo chamaemori–Dicranetum elongati subass. inops — in the southern strip of subzone, on polygonal and low palsa peatlands on the Kolguev and Dolgyi Isl., ass. R. c.–D. e. subass. caricetosum rariflorae — ibid, on small palsa and polygon peatlands on the low marine terraces along the Barents Sea coast. The plant communities of ass. R. c.–D. e. subass. typicum are common in the south tundra subzone and the northern forest-tundra on the low and high palsa peatlands and slightly differentiated peat plateau in the Timanskaya, Malozemelskaya and Bolshezemelskaya tundras.

Plant communities of these syntaxa are very sensitive to anthropogenic load and they react by changing the species abundance and their frequency. Three subassociations of Rubo chamaemori–Dicranetum elongati association got two variants: typica — distinguished on undisturbed peatlands; Ochrolechia frigida — typical for sites damaged by reindeers grazing. Plant communities referred to variant typica have a high abundance of fruticose lichens (Cladonia arbuscula, C. rangiferina); another variant Ochrolechia frigida has a bigger number of species; wh ere the high constancy and abundance got the crustose lichens (Ochrolechia androgyna, O. frigida, O. inaequatula, Icmadophila ericetorum) and cup-shaped Cladonia species (Cladonia coccifera, C. cornuta, C. deformis, C. pleurota, C. sulphurina), growing on dead plant material and peats. Such species as Dicranum elongatum, Rubus chamaemorus and some dwarf shrubs are noticeable by their abundance.

Since the palsa peatlands are wide spread over the territory of plain tundras not only in eastern European part of Russia but also in the Western Siberia, we can predict that the new associations belonging to the alliance Rubo chamaemori–Dicranion elongati will be described.