Abstract
A statistical study was made on the size of sample plot to be used in the preparation of a yield table. This has always been an important problem needing solution in Korea. For this purpose, 3 replications of Korean white pine plantings with block size of $80m{\times}80m$ were established in the Kwangneung Experimental Forest. A location map was prepared of the pines in the blocks and the heights and the breast height diameters measured. Then those blocks were divided into 64, 64, 16, 16, 4, 4, and 1 standed $40m{\times}80m$ and $80m{\times}80m$ each. After these divisions, the average heights, average breast height diameters, standard deviations and coefficient of variations were computed for the plots and averaged according to plot size. As the results of these computations, it was shown that the standard deviation and the coefficient of variation suddenly increased with the beginning of an increase in plot size. However, these indicated an approximately constant value at a certain limit. Although the average value decreases with the initial increase in plot size, it also indicates an approximately constant value at a certain limit. This limit was between $20m{\times}40m$ and $40m{\times}40m$. With the purpose of evaluating these facts, the average height and the average diameter were computed for the number of standing trees in the $10m{\times}10m$ plots. A negative (minus) relationship was found between the number of standing trees and the average value. As a result of above evaluation, it was found that when the size of plot area was small, a larger estimated value, was obtained as well as a smaller standard deviation and coefficient of variation. It is possible, therefore, that an incorrect value might be used in the evalution of data as the stand structure could appear to be uniform when the plot size was small. In general, when the size of plot area is larger than $40m{\times}40m$, the probability of the difficulty occurring mentioned above is estimated to be small.
수확표조제시(收穫表調製時) 조사(調査)한 표준지(標準地)의 크기는 $40m{\times}40m$ 이하(以上)이어야 한다. 이것보다 작으면 과대(過大)한 평균치(平均値)를 주며 임분(林分)의 구조(構造)가 균일(均一)한것 같이 보이기 쉬우므로 자료음미시(資料吟味時) 기각상임분(棄却象林分)이 채용(採用)될 우려(憂慮)가 있다. $40m{\times}40m$ 크기에서는 우려(憂慮)는 없다.