用点抽样进行森林连续清查的研究

<正>用点抽样进行森林连续清查,国内外都有采用。如“席卷美国南部的森林清查新体系”和北欧三国的全国性连续清查都是以点抽样为基础。我国广西1977年开始的各级森林连续清查也采用了点抽样(角规控制检尺)。实践表明,用点抽样进行连续清查,不仅可能产生蓄积偏小误差,还可能产生断面积生长量的测算方法和精度问题。因此,国内外对此法的实践可行性存在着疑义。有必要对此法的实践可行性在理论和实践上作进一步的研究。 本文主要探讨了点抽样的效率,偏差及估计资源变化的方法和精度问题。 所用资料是以广西自治区用点抽样进行连续清查的2909个样点的生产性调查数据为基础,因为只有这样才能真正检验出这种方法在实践中所产生的问题,并找出相应解决办法。此外,为了对比分析,1980年复查时从全区2909个固定样点中又系统抽取了约1/4的样点(共717个),以样点为中心设置了面积为一市亩的方形样地717块进行每木调查,用之与相应样点的角规控制检尺调查结果作对比分析。同时还进行了一些模拟试验和理论分析。研究结果介绍如下:

A STUDY OF CONTINUOUS FOREST INVENTORY (CFI) BY POINT SAMPLING

This paper consists of four parts, which state to the effect that (i) Analyses and comparisons of efficiency of point sampling have been made. Materials indicate that efficiency of the point sampling was seriously affected by conditions of forests investigated; (2) Biases of omission were examined and analysed in both practice and theory. A method which can be used to eliminate biases of omission and estimate the size of biases is developed; (3) Comparisons have been made between the traditional method and the Meyer’s for estimating the change of forest resources, which show the latter is more efficient, but by this method it is not convenient for the current estimate of forest resources to be used as a basis for their next estimation; (4) According to the advantages and disadvantages of point sampling, the question of application of point sampling to continuous forest inventory and other matters that merit attention are discussed.