2020 Volume 102 Issue 4 Pages 239-243
The environment for the growth of seedlings and small- and medium-sized trees of Yanase-sugi was studied to understand necessary conditions for the natural regeneration of Yanase-sugi trees in Senbonyama Gene Preservation Forest in Kochi, Japan. We measured the height, basal diameter, canopy openness, soil water content of each seedling (less than 1 cm in diameter at breast height) and litter depth around it. We also measured the height, diameter at breast height, canopy openness, relative growth rate of the last 5 years, and soil water content of each small- or medium-sized tree (1 to 40 cm in diameter at breast height), and the total basal area of each of the neighboring trees surrounding it. Yanase-sugi seedlings were observed only on fallen trees and 98.6％ of the seedlings were growing under the relatively dark conditions of approximately less than 12％ canopy openness. On the other hand, 89.3％ of the small- and medium-sized trees grew under the conditions of more than 12％ canopy openness. The small- and medium-sized trees showed the significant relationship of the relative growth rate to canopy openness, and not to any other environmental factors. Therefore, the natural regeneration of Yanase-sugi in Senbonyama Gene Preservation Forest may need the light conditions of at least 12％ canopy openness. As a result, seedling growth can not be expected in the current situation of this forest unless drastic improvements in light conditions are made.
