LATE-QUATERNARY DEVELOPMENT OF THE FAGUS FOREST IN THE JAPANESE ARCHIPELAGO

Abstract

Fagus trees began to expand in distribution northwards and to higher elevations from coastal refugia south of 38°N latitude ca.12,000 years ago. The Japan Sea and Pacific populations presumably merged around the Mabechi River area ca. 9,000 years ago. After its initial arrival at each new site, Fagus pollen showed a logistic increase in tree abundance. The intrinsic rate of population growth (λ in yr^<-1>) in near-optimal growing conditions ranges widely from 0.0017 to 0.0055 (which are still typical values for climax forest species). At Lake Nojiri, the λ value in the relative frequency curve (0.0055) is higher than that in the absolute influx (gr cm^<-2>yr^<-1>) curve (0.0037), definitely suggesting that changes of the relative pollen frequency in the early developmental phase of the forest were affected by declines and increases in the abundance of other species.