2021 Volume 103 Issue 4 Pages 285-290
The stand growth process of an overcrowded old-growth plantation of Japanese Cedar (Cryptomeria japonica D. Don) was investigated for 41 years, beginning when the stand was 134 years old, in the slope and flat site. In the slope site, since very weak cutting of about 10％ in number ratio was carried out several times, overcrowding condition could not be eliminated and mortality continued. However, as the trees were continuously cut down, the degree of crowding gradually improved and DBH growth increased, average height: DBH ratio decreased to less than 70, and net increment in stand volume reached more than 10 m3/ha/year. In the flat site, the low thinning of 22％ in number ratio was carried out, when the stand was 146 years old, and overcrowding condition was eliminated and mortality stopped. As DBH growth increased, average height: DBH ratio decreased to less than 70 and net increment in stand volume increased to around 20 m3/ha/year. It was confirmed that since the tree height growth continues at first site class, the net stand volume increment would be around 20 m3/ha/year for about 20 years, if lower thinning is conducted to exceed 15％ of the relative spacing index.
