ブナ林の異常分布に及ぼす裏日本気候の影響

抄録

The lower limit of the altitudinal distribution of the Japanese beech (Fagus crenata) forests is remarkably lower in the Japan Sea climate than in the Pacific climate with similar temperature conditions. The authors attempted to explain the phenomenon by an analysis of the effects of climatic factors on two dominant species, Fagus crenata of the cool-temperate deciduous forest zone and Quercus stenophylla of the warm-temperate evergreen oak forest zone. Results of the temperature analysis using Kira's warmth index and coldness index showed that beech can survive in the warmer areas in the Japan Sea climate than in the Pacific climate. Conversely, the temperature condition of the upper limit of the oak forest distribution was the same in both climate. A multiple regression analysis of 58 climatic factors was done to explain the abnormal lower distribution of beech forests. The phenomenon could be satisfactorily explained by the absolute value of the products of winter precipitation and coldness index. The value, snowdrifts duration index (SDI), was related closely to the duration of snowdrifts.