其他摘要：In order to clarify the influence of non-weeding treatment on the early growth of Chamaecyparis obtusa, we examined the factors affecting the size and growth in terms of vertical and lateral suppression through comparison of tree size and growth with weeded site. Mean tree height and diameter at breast height (DBH) at the end of the 4th growing season did not differ significantly between treatments. However, mean crown projection area was far smaller in the non-weeding site. Decision tree analysis demonstrated the relationships between tree height or DBH and vertical suppression, showing that vertical suppression is the predominant factor restricting the early growth of hinoki. The comparison of the growth between treatments showed the influence of both vertical and lateral suppression on every measure. Decision tree analysis, however, indicated the stronger influence of lateral suppression than vertical suppression. Lateral suppression might reduce the light availability and inhibited the increment of leaf mass of hinoki, resulting in the decrease of mass production. We concluded that avoiding vertical suppression on tree top is essentially required to maintain the ordinary growth of hinoki. However, as the cumulative effects of lateral suppression might realize even after weeding, the timing of weeding should be decided based on not only the status of vertical suppression but also the crown volume and/or leaf mass affected by lateral suppression.
关键词：決定樹分析;下刈り省略;上方-側方被圧;低コスト育林;ヒノキ
其他关键词：decision tree analysis;non-weeding;vertical-lateral suppression;laborsaving in silviculture work;Chamaecyparis obtusa
