SNOWBED VEGETATION OF FAR NORTHEASTERN ASIA

Two main types of snowbed habitat with their typical vegetation in far NE Asia are described. In extreme snowbeds, snow depth is greater than or equal to 5m; the vegetation is sparse and characterized by Salix polaris and arctic and arctic-alpine taxa adapted to a very short growing season. In moderately snow-rich habitats, with a snow depth of 1.5 - 5 m, the environment is more favourable for plant growth as compared to both extreme snow-rich and mesic habitats, because of snow protection in winter, little permafrost, high organic matter accumulation, and no major reduction of the growing season. Within each snowbed habitat there are two series of community types for lime-rich and lime-poor habitats. Along with a large number of pH-amphitolerant species including the dominants Salix polaris, Cassiope tetragona, Artemisia tilesii which occur in both habitat types, acidic sites usually also have stenoacidophytes (Carex nesophila, Loiseleuria procumbens), and hemiacidophytes (Salix chamissonis, Artemisia arctica). Differential taxa of circumneutral and basic soils are the stenobasiphytes Salix rotundifolia and Dendranthema integrifolium and the hemibasiphytes Salix reticulata and Carer scirpoidea. Ten Chukotka snowbed associations are provisionally described and a diagnostic table is presented according to the Braun-Blanquet approach. The syntaxonomy and evolution of Beringian snowbed vegetation are discussed.