Annual fluctuation of seed-fall amounts in the basin of Yokoyu river, Shiga heights [Japan]: Fagus, Quercus, and Cornus species in the utilization area of Japanese monkeys.
1991
Komiyama A. | Wada K. | Kuga H.
The basin of Yokoyu river in Shiga Heights, Nagano prefecture, is famous for the natural distribution of Japanese monkeys. In this study, the effects of annual fluctuation of seed production on the monkey populations are elucidated. A survey area of 327ha was established, and the distribution of vegetation type was analyzed. During 1978-1987, 52 seed-traps of 1 centiare were installed for Fagus, Quercus, and Cornus forests. Each tree species showed a remarkable annual fluctuation in seed number, and the mast-year was changed with the tree species. In some series of years, all the studied tree species had bad crops, and the amount of seeds in the study area remarkably decreased. Among vegetation types, large differences were found in seed production because of the difference in tree composition. It was considered that the main foods and utilization area of Japanese monkeys in autumn should change annually on account of the fluctuation of seed production.
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