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A comparison of N-tree distance sampling with fixed-radius plot and variable-radius point sampling methods.

机译：N树距离采样与固定半径图和可变半径点采样方法的比较。

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摘要

N-tree distance sampling is examined analytically and empirically as an alternative to the traditional forest inventory methods, fixed-area plot and variable-radius point sampling. With n-tree distance sampling, the number of trees sampled at every location is the same (n). The radius of the circular plot is the distance from the sample location to the center of the n{dollar}rmsp{lcub}th{rcub}{dollar} tree. The method is easy to conduct in field applications.; The estimators of trees per acre and basal area per acre are unbiased for all three methods in random or clustered spatially patterned forests modeled by the Poisson or negative binomial distributions, respectively. A formula was derived to quantify the precision relationship of n-tree sampling and plot sampling when estimating the number of trees per acre in these forest types. The number of trees needed for n-tree distance sampling to be as precise as plot sampling depends on the fixed-radius plot size, the forest density, and the amount of clustering.; N-tree sampling of stands produced estimates which were slightly biased. The direction of this bias depended on both the spatial pattern of the forest and the form of the sampling estimator. Although the coefficients of variation for n-tree sampling tended to be larger than those of traditional methods it was compared with, increasing the number of samples for the n-tree method made the precision of the methods equivalent. A time study demonstrated that when few trees are included in an n-tree sample, increasing the number of samples may be a cost effective alternative.
机译：对N树距离采样进行了分析和经验检验，以替代传统的森林清查方法，固定区域图和可变半径点采样。使用n树距离采样时，在每个位置采样的树数是相同的（n）。圆图的半径是从样本位置到第n个树的中心的距离。该方法易于在现场应用中进行。在由泊松或负二项分布分别建模的随机或群集空间模式森林中，对于这三种方法，每英亩树木和每英亩基础面积的估计量都是无偏的。在估算这些森林类型中每英亩树木的数量时，导出了一个公式来量化n树采样和样地采样的精度关系。 n树距离采样要精确到地块采样所需的树数取决于固定半径地块大小，森林密度和聚类数量。展位的N树抽样得出的估计值略有偏差。这种偏向的方向既取决于森林的空间格局，又取决于采样估计器的形式。尽管与传统方法相比，n树采样的变异系数趋于更大，但与之相比，n树方法的采样数量增加使方法的精度等效。一项时间研究表明，当n树样本中包含的树木很少时，增加样本数可能是一种经济高效的选择。

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