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《模拟样地抽样调查法》确有它的独特见解。模拟样地与常规样地比较,具有速度快、简便易行等优点。但该法的基本原理和计算方法也存在一定问题。为使这个调查方法日臻完善,提出下面几点不同见解,进行讨论。一、关于模拟样地的半径r_i的计算全距模拟样地半径r_i的计算是:式中:r_(ij)是第i样地第j株树木的株距。我们认为r_i是每株林木所占林地面积按正六边形模拟,然后求得平均正六边形面积的半径,因此: 至于中距模拟样地半径r_i的计算式中:r_(i3),r(i4)分别为距中心木最近的第3株,第4株树木的距离。这样又增加株距的一阶方差,所以更为不妥。二、关于每公顷蓄积量估计值(?)_(ha)的计算式中:(?)_(ha)——每公顷模拟株数的估计值 (?)——平均株距 (?)——模拟林木平均单株材积我们认为机械布点后,以各点邻近的7株木组成样本单元,每个样本单元的株数一样,而面积不等,实际上是不等概抽样,在计算总体每公顷蓄积量估计值(?)_(ha)时要进行概率折算。
The Sample Surveys Act does have its own unique view. Compared with the conventional plots, the simulated plots have the advantages of fast speed, simple and easy operation. However, there are some problems with the basic principles and calculation methods of this law. In order to improve this method of investigation, we put forward the following points for discussion. First, on the simulation plot radius r_i calculation Full range simulation sample radius r_i is calculated: Where: r_ (ij) is the i-th sample of j-tree spacing. We think that r_i is the forest area occupied by each tree according to the regular hexagon model and then the average hexagonal area radius is obtained. Therefore, as for the calculation formula of the radius r_i for the intermediate range model, r_ (i3), r i4) are the distance from the third tree closest to the center wood and the fourth tree. This will increase the first-order variance of plant spacing, so it is more inappropriate. (Ha) - Estimated number of simulated strains per hectare (?) - Average spacing (?) - Simulation We think that after the mechanical placement, the seven trees adjacent to each point form a sample unit, each sample unit has the same number of strains but different sizes. In fact, it is unequal sampling. When calculating the total accumulation per hectare Estimate (?) _ (Ha) Probability conversion.