Analysis of the planting density toward low-cost forestry: A result from the experimental plots of obi-sugi planting density

We investigated the planting density of Sugi (Cryptomeia japonica) at two experimental density plots of Obi-sugi trees in the south forest district of the national forest, Miyazaki Prefecture. There were established in 1974. Both have the same systematic experimental design formulated by Nelder (1962) with 10 density blocks in the range of 376∼10,000 stems/ha and 36 repetitions. The weakness was identified in the extreme high and low density classes on the basis of the tree size, growth rate and wood quality. The high density class included the higher volume density per ha, which became constant with a volume density greater than 1,615 stems/ha. This class included trees with lower wood quality, while the low density class included those with the lower volume density per ha. From the above analysis, we concluded that the moderate planting density, which is approximately 2,000-2,800 stems per ha, is the appropriate density for low-cost forestry.