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Yakushima is an island located at about 130 km to the south of Kagoshima city. Total area and circumference of the island are equal to 500.56 km^2 and 100 km, respectively. The island has the shape which is similar to a circle. The distance between north and south capes of the island is about 28 km, while the distance between west and east capes of the island is about 24 km. Besides Mt. Miyanoura, the highest in Kyushu region, with the elevation of 1,935 m, there are also more than 30 mountains with the elevation of 1,000 m and avove. In relation to the above mentioned, 45,461 ha or 90.8% of total island area is covered by mountain forest. This is consisting of National Forest, Communual Forest and Private Forest with the area of 38,600 ha (84.9%), 1.705 ha (3.8%) and 5,156 ha (11.3%), respectively. The main species in the National Forest is Sugi (Cryptomeria japonica) with the ages of more than 1000 years and normally called as “Yakusugi”. Diameter (DEW) of the Yakusugi is larger than 120 cm. Meanwhile, in Yakushima, trees with DBH smaller than 120 cm are normally called as “Kosugi”. As the standing stock of Yakusugi is gradually decreases its protection and cultural treatment has been becoming a serious problem in the recent time. This study intended to obtain the basic data for the protection and cultural treatment of Yakusugi and to clarify the effective method for the estimation of the number of tree of Yakusugi. In relation to this purpose, an investigation by strip sampling has been conducted in Hanayama district, Shimo-Yaku Forest Region and Shiratani district, Kami-Yaku Forest Region. The investigated forest area are 175.13 ha in Hanayama district and 138.96 ha in Shiratani district. As the result, it was obtained that total number of Sugi trees in Hanayama district, with the significant level of 5%, is equal to 19947.3f4587.5 stems (The total number for Hinoki, Tsuga and Momi trees are equal to 875.7f716.4 stems, 2723.8±1317.2 stems and 389.7±468.5 stems, respectively). In Shiratani district, it was found that the total number of Sugi trees is equal to 18103.0±12278.2 stems (The total number Tsuga and Momi trees are equal to 1827.3±3117.2 stems and 548.9f625.7 stems, respectively). The larger-size trees with DBH of 120 cm and above, was found to equal to 17 stems and 11 stems of them are Yakusugi (these are covering 8.3% and 5.4% of total number of 204 stems, respectively). In Shiratani district, it was found that larger-size trees are amount to 2 stems and 1 stem of them is Yakusugi (these are covering 2% and 1% of total number of 99 stems, respectively). The interpretation of standing stock of Yakusugi by aerial photograph has not presented the expected result. This is because the aerial photograph esed in this study are old panchromatic photos taken in October 1963 and May 1969. And therefore, the different of crown form, tone and contrastly between Sugi and Tsuga or another needle-leave trees, was not clearly identified. However, the relations between DBH and crown diameter (CD) for Sugi and Tsuga present the different significantly. In the future, it is necessary to conduct the investigation by using the film which be able to present the clearly different characteristics of multispectral and reflection of different species, such as infrared film, infrared color film, false color film, digital color film, etc.
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