Population Growth and Migration Rate of Fagus crenata during the Holocene in Southwestern Hokkaido, Japan

摘要

The Holocene population growth and migration rate of Fagus crenata in south- western Hokkaido (Yakumo area) was in- vestigated based on pollen analysis. The species invaded a Quercus-dominated forest 3,400 years BP; subsequently the population grew progressively and was saturated after 1,700 years. Quercus popu- lation decreased rapidly at the initial stage of Fagus crenata invasion, attained stabili- ty and then gradually decreased. The in- trinsic growth rate (0.0031) of Fagus crenata, fitting the logistic growth model, is in good agreement with the rates known from central and northeastern Honshu. Doubling time is 230 years. The migration rate is extremely low (about 20m/yr) compared with rates in northeastern Honshu, with that of F. sylvatica in Europe, and with that of F. grandifolia in North America. The low migration rate in southwestern Hokkaido implies that the population was estab- lished by seed dispersal, whereas the pop- ulation in northeastern Honshu was estab- lished by expansion of extant sparse popu- lations. The long term (1,700 years) requir- ed for forest replacement probably results from strong competition with resistant forest species such as Quecus, etc.