Abstract
The development of willow (Salix pierotii) community at upstream inlet area of the reservoir, which is located at 30 years old Egawa dam and is a part of Chikugo River system, was studied. By interpretation of aerial photographs and analysis of tree age, it is determined that the colonization of S. pierotii community started since 1986. Although upstream area of the reservoir is submerged, this area often gets drawdown during seedling period of S. pierotii, and the exposed ground is capable of germination and colonization. S. pierotii is submerged at one meter depth for 66 days per year on average and 200 days in a row per year when submergence occur frequently. Sediment deposition formed by flood also occur at this colonization area, resulting in strict condition for plant, but this S. pierotii community keeps on growing with developing adventive root.
