An Inventory of Subtidal Vegetation Associations in the Far Eastern Seas of Russia

Assemblages of subtidal vegetation in the Far Eastern seas of Russia have been poorly and nonsystematically studied. The scopes of assemblages (from a local phytocoenosis to the entire vegetation belt of certain areas) described by different researchers varied or were not clearly determined. A general methodological framework, which would allow classifying their composition, has not yet been proposed. The concept of an adaptive zone (AZ) can serve as such a basis for systematization of diverse descriptions. An AZ is defined as a site of vegetation cover where the habitat conditions for a single species are so favorable that it forms phytocoenoses and dominates them in abundance. Many phytocoenoses with a common main dominant species can be described as vegetation associations. An inventory and analysis of the distribution of subtidal vegetation associations, thus interpreted, has been carried out. For this purpose, information regarding those dominant species of subtidal vegetation for which AZs are formed in the regions of the Russian Far East have been selected from available literature sources. Quantitative data or text indications, provided by these sources, that each species under consideration dominates in abundance at a certain set of vegetation sites have been used. As a result, a total of 67 associations distributed in 13 areas of the Russian Far East have been distinguished. One-third of the associations have a narrow distribution in a single area; half of them are distributed moderately in 3–5 areas; the others are widespread in 7–9 areas. High-boreal areas are depleted in coenotic diversity (5–11 associations in each), while low-boreal areas are coenotically abundant (23–31 associations in each). Maximal similarity in the vegetation composition between the areas of the Sea of Japan (at least 62%) and the northern areas of Sea of Okhotsk (at least 73%) is distinguished. The pronounced thermo-coenotic (α = 1.7 ± 0.3, R2 = 0.71, p = 0.0006) and floro-coenotic (α = 0.14 ± 0.06, R2 = 0.56, p = 0.05) gradients show that the increase in the number of associations from north to south is consistent. This follows the Humboldt–Wallace rule and represents its phytocoenotic aspect. The ratio of the numbers of assemblages of different systematic groups can characterize the thermotropism of vegetation in both large areas and local sites.