Cryptomeria japonica D. Don (Japanese cedar) is a conifer in the temperate zone. The mortality of its seedling is very high in a snowy region because the optimum establishment site is restricted only on plant bodies and mineral soils. On the other hand, some research indicate that seedlings of C. japonica grow larger under canopy gaps. Therefore, a large disturbance might promote establishment of seedlings.

Typhoon disturbance uproots trees. Uprooted trees are sometimes alive and extend their buds and sprouts. Clonal growth of uprooted trees may have strong effect on forest regeneration. The purpose of this study is to clarify the effects of typhoon disturbance on regeneration of C. japonica forest.

To evaluate the typhoon disturbance, we set 2 plots: one plot has many uprooted trees and the other plot has less uprooted trees. We measured the size of the seedlings, the buds and sprouts of uprooted trees. In the uprooted plot, the number and the length of seedlings on mounds and fallen-logs are greater than the less uprooted plot. 56% of uprooted trees are alive. The maximum height of their buds and sprouts have reached 8.5m.

These results suggest that the large disturbance promotes the establishment of the seedlings, and that uprooted trees may have a strong effect on the forest regeneration.