Two methods are commonly used to measure the diameter of a tree’s crown or to make tree crown projection figures. One is to measure between points transcribed by eye from the ends of the tree’s ...branches to the ground below the tree; the other is based on aerial photographs. However, the accuracy and precision of these methods can vary by tens to hundreds of centimeters, as it is difficult to determine the precise locations of these points by eye or from photographs. To address this issue, we developed a new tree crown measurement tool, the Ten-bou-kyou, roughly translated as vertical mirror-eye to the sky. To assess the tool’s accuracy and precision, we used it to measure branch like marks beyond our reach 100 times and compared the results with known reference data. The results using our device differed from the reference data by -1 to 4 cm, with an average of 1.8 ± 1.0 cm. Therefore, we conclude that, despite its slight positive bias, the Ten-bou-kyou may be a promising method for determining the location of points directly below tree branches to within approximately ± 1.0 cm.
A planting test of Sasa nipponica was conducted under the various conditions to prevent the frost heave damages on the slopes along a road in a cold region by native S. nipponica. Studying the growth ...during 2 years after the planting through the soil property test, the meteorological observation and the growth investigation, it appeared that the growth was influenced by the kinds of soil and the low temperature during winter. Namely, it was clarified from the survival rate of S. nipponica that the frost-susceptible and fine-grained soil is more suitable for the growth of S. nipponica than the nonfrost-susceptible and sandy soil. Further, S. nipponica planted at the frost-susceptible soil site was larger in the average height than that at the non-frost: susceptible soil site. Since the height of grasses in all sites were smaller than that in the previous year, S. nipponica at the frost-susceptible soil grew superior to grasses which compete to grow with it. Therefore, the species seemed to achieve a suitable environment for the growth in a cold region through such cold weather.
To establish management criteria for watershed forests, basic studies on sugi (Cryptomeria japonica) plantation forests were performed at Okinoshima, Shimane Prefecture, Japan. Fourteen forests were ...surveyed. In nine forests, which had not been thinned in over 10 years (not-thinned forest), the relative yield index (Ry) was >0.8 and stand density was high. In two forests, which had been thinned in the past 10 years (recently thinned forest), Ry was <0.7 and stand density was low; these values were consistent with the yield table for the San-in region (western part of the Japan Sea littoral zone). In two other recently thinned forests, Ry was >0.7 and stand density was high. In the remaining recently thinned forest, Ry was >0.9 and stand density was very high, despite being thinned recently. Stand density was high after thinning because (1) the forest owner had no clear production target, (2) the forest was thinned only to meet criteria for financial support from the government, and (3) stand density was extremely high before thinning. A definition of thinning is to thin trees to achieve a production or management target; however, with no clear target, the thinning of very dense forests is not for maintenance, but simply to cut some of the trees. Criteria for obtaining financial support from the government involves the ratio of cut trees to total trees before thinning; thus, very dense forests can still remain dense, even after thinning. Therefore, criteria for acquiring financial support from the government must be reconsidered.
The aim of this study is to organize the techniques for long term forest management and put the vanishing technique on record by examining the existing technique in Yoshino. We obtained by hearing ...the criteria of thinning tree selection and Mr. Tadakazu Arizuka's autobiography who is one of 'Yamamori' forester working at sugi and hinoki plantation at Sugitani in Higashiyoshino. As the results, it is clear that he found fun and something to work for and was responsible for his work. He learned about some of techniques by his leaders and he kept working for a long time. His criteria of thinning tree selection are; 1. 'To keep good tree formation. (He would like to keep forest high quality.) 2. To watch the tree canopy. (By doing so, he decides which tree is to be thinned.) 3. To cut the tree standing at the upper side of the hill. (Such trees will disturb the growth of ones standing at lower.)
The characteristics of thinning tree selection applied by Mr. Tadakazu Arizuka was analyzed at Sugitani in Higashiyoshino. We selected some thinning trees setting for further long-term management. ...Before and after the selection, we measured the DBH of all individuals. In spite of applying the same criteria in selection of thinning trees, the way of thinning selection was different between older forests (about 50-120 years) and younger forests (about 17-45 years). The management system of Sugitani plots corresponded to the Yoshino's thinning selection methods in middle intensity. We compared the Yoshino thinning selection in middle intensity with that of. Wakayama by growth ring distribution. It was appeared that Yoshino thinning selection system was able to keep the width of ring growth constant.
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