A simulation study examined what sampling methods might be appropriate in a forest inventory to estimate the frequency distribution of tree stem diameters or ages across a forest population that covers a large area. It reviews the efficacy of such inventories done in aspen (Populus tremuloides Michx.) forests in southwestern USA and uses them as a particular example. A range of frequency distributions of stem diameters and tree spatial arrangements across the landscape were simulated as an attempt to cover a wide range of possible forest circumstances. Three sampling methods, fixed-area plot, k-tree and individual-tree sampling all yielded unbiased estimates of the frequency distribution of tree diameters and ages. Point sampling also gave unbiased estimates of the diameter distribution, but with increasingly poorer precision of frequency estimates as tree diameter declined. It yielded biased estimates of the frequency distribution of tree ages because it determines the probability of the inclusion of tree in a sample using the square of its stem diameter, rather than its age; methods exist that might sometimes overcome this limitation, but they require rather complex methodology. The results should apply equally to individual-tree characteristics other than tree age, characteristics such as tree height, severity of disease, suitability for bird roosting or level of seed production.

一项模拟研究检查了在森林清单中哪种抽样方法可能适用，以估计覆盖大面积森林人口的树干直径或树龄的频率分布。它回顾了在美国西南部的白杨（Populus tremuloides Michx。）森林中进行的此类清单的有效性，并以它们为例。模拟了整个景观中茎直径和树木空间排列的频率分布范围，以试图涵盖各种可能的森林环境。三种采样方法，固定面积图，k树木和单棵树木的采样都对树木直径和树龄的频率分布进行了无偏估计。点采样还给出了直径分布的无偏估计，但是随着树直径的减小，频率估计的精度越来越差。由于它使用树的茎直径的平方而不是树的年龄来确定树木在样品中包含的概率，因此得出树的年龄分布的偏向估计值。存在有时可以克服此限制的方法，但是它们需要相当复杂的方法。该结果应同等适用于树木年龄以外的其他树木特征，树木高度，疾病严重性，鸟类栖息地的适宜性或种子生产水平等特征。