Abstract
To estimate the acorn crops as the food resource of Japanese black bear (Ursus thibetanus), I examined the relationship between the production of sound (mature) acorns and the number of fallen male inflorescences of three Fagaceae species (F. crenata, Q. crispula, and Q. serrata). The annual fluctuation of male inflorescences in F. crenata tended to synchronize strongly with that of the total or sound acorns, and the regression equation between the number of male inflorescences and sound acorns showed a high coefficient of determination. On the other hand, the annual fluctuation of male inflorescences and mature acorns in two Q. species did not synchronize as strongly as that in F. crenata, and the regression equation between the number of male inflorescences and mature acorns in both species showed a low coefficient of determination. However, the acorn crop size estimated by the predicted number of sound (mature) acorn substantially matched up to the results based on the monitoring survey of fruiting intensity of three species in each year. These results showed that grasping the number of fallen male inflorescences is effective to provide a rough tendency of acorn crops in three Fagaceae species in early summer.
