A Study on the multiple evaluation of heavy thinning for production of large-diameter medium-quality logs of Cryptomeria japonica in Tokushima [Japan]
2008
Otsuka, K.(Kyoto Univ. (Japan)) | Hasegawa, H. | Nobuchi, T.
'Senboku-ikurin' is a local silvicultural system which was proposed more than 30 years ago in western part of Tokushima prefecture. The noteworthy features are early selection of trees left for the future at stand age of ca. 15 year, and heavy thinning at ca. 25 years. Its goal is early production of large- diameter logs. In this study, we tried to evaluate effects of the heavy thinning on the growth of Cryptomeria japonica, forest ecosystem, and the profitability of thinning. The evaluation was made by comparing characteristics of stands that experienced heavy thinning and those that were treated by normal thinning. The results of vegetation survey showed that the heavy thinning enhanced species-diversity of woody plants. Additionally, stem analysis and estimation of income from heavy thinning suggested that early practice of heavy thinning is superior in tree growth to late practice, but inferior in its profitability. We concluded that the heavy thinning of 'Senboku-ikurin' had positive effects for planted trees, forest ecosystems, and forest management. However when we try to put this system to practical use at the present time, we should introduce some operational flexibility by making changes in the timings of heavy thinning and final cutting, and innovate more appropriate logging systems.
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