Shiga Prefecture Fisheries Experiment Station, Hikone, Shiga 522-0057, Japan
The influence of winter reaping of withered stems of the reed Phragmites australis on their budding and growth was examined in Lake Biwa. When the cut ends of withered stems were flooded in spring, growth of new shoots was inhibited probably because of limited oxygen supply to the rhizomes. As an adaptation, the reeds rapidly extended shoots to the water surface to obtain oxygen. However, it was thought that this adaptation would not function easily in natural lake areas because these shoots were easily damaged by wind and waves. On the other hand, it was confirmed that withered stems have a function to protect new shoots from wind and waves. Furthermore, the importance of the humus originating from the litter of reeds was confirmed for the budding and growth of the reeds. Thus, it was concluded that the withered stems should not be reaped in areas where submergence is expected at the time of budding.