Abstract
We investigated tree growth and height/diameter (H/D) ratio of understory trees of sugi and hinoki in the alternate strip-clearcutting stand 26 years after the even-aged stand of 65 year-old hinoki with mean dominant-tree height of 18 m was cut alternately in clearcut and leave strips with width of about 14 m and 19 m, respectively. Tree height and DBH increased from the middle of leave to clearcut strips. We found that height growth of the understory trees in the clearcut strips was similar to that of even-aged stands in the vicinity, based on comparing the local yield tables with height growth curves obtained from stem analysis and with mean dominant-tree height for each distance class from the edges between clearcut and leave strips. The H/D ratio was almost constant irrespective of distance from the edges and the mean values were 81 and 76 for hinoki and sugi, respectively, being similar to mean values observed in even-aged stands managed by normal density control in Japan. The strip width is the most critical determinant of height growth and H/D ratio of the understory trees, with the former being influenced by the balance between microclimatic improvement and light quantity reduction due to the leave trees and the latter by the amount of direct light from zenithal and lateral direction. We conclude that the clearcut strip width equivalent to about 80% of the dominant-tree height is appropriate judging from height growth and H/D ratio of understory trees. The alternate strip-clearcutting system may have potential to fulfill the conditions required for sustainable managed forests such as high profitability, high productivity, high stocking and biodiversity conservation.
