Abstract
Change in height growth of Japanese cedar was investigated within a plantation of this species which was planted in 1908, was thinned three times during the age of 45∼73 years old with various intensities, and was 104 years old at the last inventory. To test whether the height growth rate of trees should be lower after thinning operations than without thinning operations, pairs of 45-years-old trees were selected; for each pair, one tree was selected from stands with thinning operations and the other from those without thinning, with criteria that they were almost equivalent in terms of diameter and height. Among these pairs (189 in total), the pairs which showed equivalent diameter growth of constituent trees afterward were selected, and height and slenderness (height/diameter) was compared between the trees belonging to the same pair. The trees of intensively thinned stand showed lower height growth beyond the age of 60, and this tendency persisted until age of 104. The trees of moderately and lightly thinned stands showed a similar pattern during the later period. At the age of 104 year old, trees in the moderately- or intensively-thinned stands showed lower values for slenderness than those in the un-thinned stands. This was explained by both greater diameter growth and lowered height growth caused by thinning operations.
