2006 Volume 23 Issue 2 Pages 137-152
Ecogeography of a forest community, which includes Siebold's beech (Fagus crenata Blume), in the Pacific side of eastern Japan (Yamizo Mts., Abukuma Mts. and Kitakami Mts.) was studied, based on data from 54 forest stand. Forest stands were classified into five groups, A to E, by TWINSPAN analysis. Four groups (A-D groups) were characterized by the species which are common to climax forests of the lower temperate zone in the Pacific side of eastern Japan, such as Fagus japonica forests and Abies firma forests. On the other hand, E group was characterized by the evergreen shrub species which were common to the climax Siebold's beech forests in the Japan Sea side region. Many species such as Quercus serrata, Carpinus laxiflora, F. japonica and A. firma, were co-dominant in A, B and C groups, without a single, major dominant species, but Siebold's beech was the major dominant in D and E groups. The climatic cline among stand groups was obvious; from A group to E group, the Kira's warmth index decreased, while the amount of winter precipitation and the maximum depth of snow increased. In terms of micro-topography, most forest stands were established on the ridge or on the upper side slopes. Population structure of Siebold's beech showed distinct differences, in accordance with the change of vegetation from A group to E group; the relative dominance and the density of Siebold's beech increased, and the size structure changed from the sporadic type to the continuous type. It is considered that Siebold's beech originally had an extensive distribution both horizontally and vertically, as a component of the various types of climax temperate forests in the area, forming dominant forests in the upper temperate zone, and forming scatterred metapopulations in the lower temperate zone.
