積雪によるスギ造林木の根曲りについて-2-

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This report deals with the bend of lower part of afforested cryptomeria caused by creeping pressure and settling force of snow deposit in the neighborhood of Yamagata Branch Station. Frequency of the bend amount to 100 percents in the sites where mean diameter breast high is less than 10 centimeters and even in the sites of the mean diameter of 30 centimeters it shows more than 80 percents. When the shapes of stems are classified as following according to bending 0 (almost straight), I (slightly bent), II (remarkably bent), III (most remarkably bent), total percentage of 0 and I shows 58 percents and that of II and III shows 42 percents, this figures show that percentage of large extent of bend occupies more than half. Occurrence of bend depends on the growth and the sites of small increment tends to show large percentage of bend. The lowest percentage of bend appears in the sites with the gradient of 5 degrees, and the percentage becomes higher when the gradient is steeper or more gentle than 5 degrees gradually. Level site and 20 degrees slope show about same percentage of the bend. From topographical viewpoint, the percentage of the bend is relatively low in the sites such as convex surfaces or terraces and it is high inversely in the sites such as concave or intricate surfaces. The relation between the ratio of bent part to the whole stem volume in percent (R) and slope in degrees (α) is expressed as following; R=0.34α+7.5 The coefficient 7.5 is related to snow depth and is determined in the area of about 1.5 meters depth, however, it should be presumed to fluctuate to some extent depending upon the physical properties of snow deposit.
社団法人日本雪氷学会の論文

積雪によるスギ造林木の根曲りについて-2-

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