Sociological studies of the forests in the Tohoku District 4. Forest communities in the northernlimits of Shiia Siebodii.

Abstract

On the Pacific side of Japan, the northern limits of the evergreen broad leaved forest dominated by Shiia Sieboldii occur at a coastal hill about 20 km northeast of Taira City, Fukushima Prefecture (37°10′N.L.). In the northern limits the annual mean temperature is slightly higher than 12℃ and the montyly mean temperature of the coldest month (January) is 2℃. The 2℃ isothermal line of the monthly mean temperature of January falls nearly on the northern limits of the forest of Shiia Sieboldii. Two types are distinguished among the climax forests of Shiia Sieboldii ; one is the Shiia Sieboldii-Machilus Thunbergii Community in coastal sites and the other the Shiia Sieboldii-Cyclobalanopsis myrsinaefolia Community in inland sites. These climax forests, at present, remain scattered as residual ones on undisturbed sites. Owing to clearing and fire a greater part of the climax forest of Shiia Sieboldii has degenerated into the secondary one of Pinus Thunbergii ; of P. densiflora and of Quercus serrata-Castanea crenata.