著者

箕輪 光博

出版者

一般社団法人日本森林学会

雑誌

日本林學會誌 (ISSN:0021485X)

巻号頁・発行日

vol.61, no.11, pp.410-412, 1979-11-25

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A new sampling technique for deriving stand volume through the estimation of the sum of critical heights by STRAND'S method is proposed. This technique is characterized by double counting based on both KITAMURA'S critical height method and STRAND'S vertical line sampling, the latter of which is modified to something like point sampling in this paper. First, two parallel lines are selected in the stand, each of which has a random point as its center and is perpendicular to the segment formed by the two center-points. Next, double counting (horizontal counting followed by vertical counting) from each center-point is made for all surrounding trees, allowing an unbiased estimate of stand volume to be formed by the average tree count per point-line multiplied by a constant factor associated with a pair of given horizontal and vertical angles. It should be noted that the vertical angle used at each point is not constant but is a variable angle associated with the horizontal angle that is between the corresponding line and the line sighted from the point to the surrounding tree. This procedure, however, offers the possibility of reducing the difficulties encountered in the direct measurements of critical heights notwithstanding the above additional work.