Effects of initial size and surrounding weed trees on height growth of planted sugi (cryptomeria japonica) trees in Kyushu, Japan

Abstract

To clarify the effects of initial height and surrounding weed trees on the height growth of 107 planted sugi (Cryptomeria japonica) trees, we investigated competition between weed trees and the sugi trees in a four-year-old plantation. In this plantation, weeding was conducted when trees were one and two years old, but was not conducted when they were three years old. The height growth of sugi was more strongly influenced by vertical suppression than lateral suppression of the crown. Height growth decreased when the top of the crown was covered by surrounding weed trees. Additionally, we found a significant positive correlation between initial size and height growth for the sugi trees whose top of crown was covered by weed trees. On the other hand, height growth of the taller sugi trees did not change regardless of the cover by weed trees, and variation in their height growth was relatively low. These results indicate that it is better to conduct weeding at the initial stage after planting to favor growth of planted sugi. Our study showed that the height of sugi and vertical competition between sugi and weed trees are useful indices to effective decision making in weeding management.