Willow shrub communities in the North of the Koryak Okrug (Kamchatka Territory)

Plant communities formed by shrub willows are widespread in the North of the Koryak Okrug (the mainland of the Kamchatka Territory) in valleys and floodplains of rivers and streams, on gentle mountain slopes, hollows and depressions, along the mire edges. The main dominants are Salix pulchra, S. alaxensis, and S. krylovii. Communities formed by some other species of shrubby willows (Salix lanata, S. saxatilis, S. glauca) are quite rare. The detailed geobotanical characteristics of shrub willow communities of the Koryak Okrug are presented. The dominant-determinant classification based on 54 relevés was elaborated following the main principles and classification methods of the Russian geobotanical school approach. As the result 21 associations, included into 13 association groups and 5 formations are revealed. The peculiarities of their species composition, communities’ structure, ecology and geographical distribution are considered. Communities formed by Salix pulchra are characterized by the higher community diversity in the study area; they occupied a wide range of habitats — from floodplains and tussock tundra to drained slopes of ridges. The low community diversity was typical for phytocoenoses formed by Salix lanata, which are quite rare in the North of the Koryak Okrug, but widespread in the Arctic regions of Eurasia. Shrub willow communities formed by Salix pulchra, S. alaxensis or S. krylovii are represented by Oligoherbosa, Calamagrostidosa, Varioherbosa, Caricosa appendiculatae and Vacciniosa uliginosi association groups; they occupy depressions, hollows, foots of ridges, the slopes of hills, and flat watersheds. Sphagnosa and Paludiherbosa willow communities are found along the mire edges and in the lake hollows. The predominance of herbaceous mesophytes is character for Varioherbosa association group; among these constant are Calamagrostis purpurea s. l. prevailed and Cirsium kamtschaticum, Chamerion angustifolium, Equisetum arvense, Galium boreale, Geranium erianthum, Rubus arcticus, Saussurea pseudotilesii, Thalictrum minus, Trientalis europaea, Veratrum oxysepalum, Viola epipsiloides. The moss layer is formed by Aulacomnium palustre, Brachythecium salebrosum, Bryum pseudotriquetrum, Climacium dendroides, Dicranum majus, Hylocomium splendens, Sanionia uncinata, Sciuro-hypnum reflexum, S. starkei, etc. Alluvial gley soils and podburs are character for the sites of Varioherbosa and Calamagrostidosa association groups. The predominance of mesohygrophytes and hygrophytes in the grass layer, and green and Sphagnum mosses in the ground layer are character for Paludiherbosa willow communities. The grass layer is usually predominated by sedges Carex appendiculata and C. lyngbyei subsp. cryptocarpa with common hygrophilous herbs (Comarum palustre, Equisetum fluviatile, Galium trifidum, Caltha palustris). Mosses Calliergon cordifolium, Plagiomnium ellipticum, Philonotis fontana, Pseudobryum cinclidioides, Rhizomnium punctatum, Straminergon stramineum occur in wet depressions. Gley, peat-gley and peat soils are character for Sphagnosa and Paludiherbosa willow communities. Arctoboreal dwarf-shrubs Empetrum nigrum s. l., Ledum palustre s. l., Vaccinium uliginosum s. l., V. vitis-idaea s. l., dwarf birches Betula exilis and B. middendorffii and mesophilous mosses are main species in the communities of Vacciniosa uliginosi association group. Caricoso lugentis-eriophorosa vaginatae association group formed by Salix pulchra is transitional to zonal tundra communities in which tussock-forming plants cotton grass Eriophorum vaginatum and sedge Carex lugens subsp. soczavaeana in the grass layer predominate. The community site differed by peat-gley and cryosols underlained by permafrost. The shrub willow community’s classification units were compared with the syntaxa identified due to the floristic (Brown-Blanquet) classification approach. Shrub willow communities occupy vast areas in river valleys and intermountain depressions; they are extremely important and valuable reindeer pastures during the summer and early autumn grazing seasons.