This paper analyzed forest structure include wild Rhododendrons in comparison to a managed forest's stand at 25 years ago and an uncared forest's stand during 50 years in the secondary forest floor of Hyogo prefecture in Japan. As a result of the analysis, the number of the plant in a management forest's stand were 42 species, and 20 of 29 species of trees were deciduous broad-leaved trees including Rhododendron reticulatum which does not have a flower. In addition, there were 13 species of herb at forest floor. On the other hand, there were a small number of the plant with 23 species in a uncared forest's stand, and 8 of 20 species of trees were deciduous broad-leaved trees without wild Rhododendrons. And uncared forest also had only 3 species of herb at forest floor. Hence this paper implies that the dominant trees and an evergreen broad-leaved tree of forest floor in the early success ional stage had a conservation effect for biological diversity of deciduous trees and herbs in spite of past 25 years uncared.
