Classificаtion of Wrangel Island vegetation

The syntaxonomical study of Wrangel Island carried out in accordance to Braun-Blanquet approach is proposed. As a result 29 associations, 1 type of com­munity, 18 subassociations, 8 variants and 5 facies are distinguished. A series of associations belong to 13 allian­ces, 12 orders and 9 classes which were des­cribed earlier (some of them are provisional). The procedure of classification have showed some metho­dical difficulties. One of them is the revealing of be­longing syntaxa to any class, a lot of which were described in more south regions. As a result much of diagnostic species of these classes are absent in arctic regions. So far as many species of Arctic characterized by wide distribution they cannot be used as character species. The concept of vicariant syntaxa is used: 5 associations are considered as vicariants of syntaxa already distinguished. At present there are not any higher syntaxa (class) for correct description for zonal (plakor) vegetation, erect shrubs and zoogenic vege­tation in arctic tundra subzone. The syntaxa of Carici rupestris—Kobresietea bellardii and Thlaspietearotun­difolii predominate in island. There are north limits of areas of some syntaxa such as ass. Sphagno—Eriopho­retum vaginati vic. Polytrichastrum alpinum, Bra­chy­thecio salebrosi—Salicetum glaucae, Parryo nudicau­lis—Salicetum lanatae, Equisetetum borealis vic. Polemonium acutiflorum on Wrangel Island. Zonal associations are characterized by lowest number of character species (2—4). The reason of this pheno­mena is the average meaning of ecological parameters in plakors. As a consequence many species of different ecological groups can growth together. There are fr om 9 to 17 character species in some intrazonal associa­tions: Carici membranaceae—Dryadetum integri­foliae, Castillejo elegantis—Caricetum rupestris, Salici calli­carpaeaе—Dryadetum chamissonis, Arte­misio borea­lis—Chamaenerietum latifolii.

Following associations of plakor are characterized by the highest species richness: Parryo nudicaulis—Dryadetum punctatae (255 taxa) and Artemisio ti­lesii—Deschampsietum borealis (250). Besides these the ass. Salici polaris—Caricetum podocarpae which is formed in snowbed sites have 251 taxa. A lot of species have middle (III) or low (II, I) constancy. The higher number of species in syntaxa compared to community is due to rare species.

The coverage of majority of species varies from <1 % to 5 %, not more than 10 species — from 6 % to 12 %. Only 3 species form an stable coverage more than 25 %: Carexlugens, Dryaspunctata, D. inte­grifolia. Two types of community are characterized by the homogeneous cover: ass. Meesio triquetris—Caricetum stantis vic. Warnstorfia sarmentosa and ass. Salici polaris—Caricetum podocarpae. The tundra turf is heterogeneous in zonal (plakor) communities. It consists of different fragments of mosses, lichens and vascular plants. Frost boils (patches) are most common elements of horizontal structure. The turf around patches forms continuous net. Non closed (open) communities are predominate at all slopes, tops and mountain terraces. Cushions formed by herbs Artemi­siaborealis subsp. richardsoniana, A. glo­merata, Oxytropisgorodkovii, Potentillasubvahliana are usual in such sites. There are 2 layers in com­munities: an upper one (10—30 cm) wh ere herbs are predominate and dwarf shrubs-lichen-moss (less than 10 cm). The height of shrub Salixlanata subsp. richard­sonii layer at the center of island is 45—60 cm.