Effects of Cryptomeria japonica and Chamaecyparis obtusa Thinning Season and Bucking Method on the Emergence of Urocerus japonicus Adults.

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The effects of the thinning season (winter or summer) and the bucking method (non-bucked, bucked to 2 m, or bucked to 6 m) for sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa) on the moisture content of sapwood, the emergence of Urocerus japonicus adults, and their sex ratio were investigated. Control of the emergence of U. japonicus adults by the thinning season and the bucking method was examined. The difference in moisture content by the thinning season was not remarkable. However, the amount of emergence was smaller in winter than in summer, and this tendency was more significant in hinoki. On the other hand, the moisture content and the number of emerged adults were changed significantly with the bucking method. The range of moisture content in which many adults emerged was 80170% for sugi, and 50150% for hinoki. The range corresponded to the tree bucked to 6 m for sugi, and the tree bucked to 2 or 6 m for hinoki, respectively. It was suggested that the emergence of U. japonicus adults could be controlled by the thinning season. On the other hand, in the case of the trees felled in winter or summer, the bucking didn't control the emergence of adults. It was suggested that the emergence of adults is promoted rather than controlled by the length of bucking.
日本森林学会の論文