1966 年 16 巻 6 号 p. 241-247
The reserved forest dominated by Cyclobalanopsis glauca and C. myrsinaefolia is developed on the immediately upper part of the slopes where the Akiyoshi-do, is situated ; this limestone cave is best known for its vast scale in Japan. This study is prompted by two ways of investigation on the present forest ; one is on the basis of the structural analysis and the other is of the analysis of floristic composition. Thirty one quadrats of 10m×10m in size were established according to the topographical conditions within the forest for sampling vascular plants. In order to get or select the typical and homogeneous stands for the C. glauca and C. myrsinaefolia forest, only the quadrats in which either of the two species concerned occupies at least 50 or more of Total Importance Value and one of the two is more than two times of the other in T.I.V. were picked up. The values of similarity index, C_λ (MORISITA 1959b), were computed among the quadrats with all their combinations by means of the number of individuals of the component tree species having more than 1cm in D.B.H. There were selected based on similarity index six quadrats representative of C. glauca and eight of C. myrsinaefolia. The former group falls undoubtedly into the category of Nandineto-Cyclobalanopsidetum glaucae by YAMANAKA (1955). The latter group suggests a lower unit of that association or another new association. The quadrats were classified into two groups according to the magnitude of the slope inclination ; one is more than 30° and the other is less than that value. There is statistically significant difference between the two groups concerned in the totol number of individuals of the two species of Cyclobalanopsis. Namely, C. glauca grows predominantly on the slope more than 30° in the inclination, while C. myrsinaefolia grows predominantly on the slope of less than 30°. The values of interspecific correlation, R_δ (MORISITA 1959b), between the two species of Cyclobalanopsis were calculated along the gradient of the slope inclination. R_δ-values near null, though they fluctuate somewhat along the gradient, suggest that difference in distributional behaviours of the two species under consideration may not result from the competition between them but from their specific preference for environmental factor or factor complex by which the slope inclination is represented.