This original article is a preliminary report on the discussion related to the changes of the forest and climate in the Postglacial age, based on the present writer's palynological investigations about the late Quaternary deposits in Japan, especially Hokuriku region, during the last ten years.
The evolution of the forest of Japan since the Late Glacial age is divided into seven phases and may be summarized as follows:
(1) Cold stage (E-G phases, 12000-11000 years before the present): This stage is divided into three phases, namely G phase: Fagus, Abies and Larix; F phase: Corylus and Gramineae; and E phase: Fagus with Abies and Larix.
F phase is satisfactorily correlated with the Alleröd oscillation in Europe.
(2) Increasing warmth stage (D phase, 11000-8000 years before the present): This stage is trangitional age from the Late Glacial to Postglacial climatic optimum, and the dominanting pollen grains were made up of deciduous Quercus and Pinus, with Picea and Fagus as generally subordinate associates.
(3) Postglacial climatic optimum (C phase, 8000-4000 years before the present): This phase is correlated with the Atlantic and the early part of Subboreal in Europe. The characteristic genera were evergreen Quercus, Alnus and Cryptomeria. At some time during the Postglacial certain warmth-living plants were more widely distributed than at present, reaching higher latitudes as well as higher altitudes, namely the forest zone was 200-300m higher and it was 2-3°C warmer than the present time in average temperature.
The beginning of this phase can be tentatively correlated with the lower horizon of the first Jomonian Tado remains, being dated as about 8000 years before the present. Moreover. the maximum warmth stage may be correlated with the age of the Flandrian transgression.
(4) Cool stage (B phase, 4000-1500 years before the present): The characteristic forest of this phase was the mixed flora of evergreen broad leaves-trees and Fagus crenata (submerged erect tree stumps). It was some 1°C lower than the present time in average temperature. The dominanting pollen grains are Cryptomeria, Castanea and Pinus. The decreasing warmth stage may almost correspond with the age of the miner falling of sea-level in the Hokuriku region.
(5) Present climate stage (A phase): After about 1500 years before the present.
These climatic changes, exclucive of (4) Cool stage, satisfactorily correspond with the results obtained by many investigaters throughout the world.
The figure (Fig. 1) shown the changes of the forest and climate during Postglacial age throughout the world and Japan will help for understanding.