The Nikko highway is famous for its avenue of cedar trees. But more than a hundred trees wither a year and the number has a tendancy to increase year by year. We think that the program to protect them need to be intensified more perfectly. The content are as follows.(1) Through historical review of material on the management of the Nikko highway, we point out problems on the protective policy of them.(2) Analisys is done to clarify the relation between the number of withered trees and environments of the road and the roadside.(3) From the result we recommdnd programs to protect them.
