Minimizing the Rounding Error from Point Sample Estimates of Tree Frequencies
Author: Ritchie, Martin W.
Source: Western Journal of Applied Forestry, Volume 12, Number 4, 1 October 1997 , pp. 108-114(7)
Publisher: Society of American Foresters
Abstract:Three solutions are presented for estimating stems per acre when trees are tallied by diameter class with horizontal point sampling. The first solution is based on the arithmetic mean of the diameter-class limits. The second is based on the geometric mean of the diameter-class limits and is unbiased for uniform within-class diameter distributions. The third is a harmonic mean solution; it is derived from the ratio of the geometric mean squared and the arithmetic mean. If the within-class distribution is linear, then the solution based on the geometric mean is preferable. Any of these solutions may be adequate provided diameter-class widths are minimized, particularly for small trees. The geometric-mean solution is the recommended solution in instances where uniformity can be assumed within diameter classes. Observed frequencies in two stands, however, provided inconsistent results. In estimating tree frequency, errors resulting from grouping become smaller as tree diameter increases. For large trees, estimation of frequency can be obtained with much wider diameter limits than with small trees for a fixed level of grouping error. Rather than fixing diameter-class width, it may be advantageous to consider a narrower class width or exact measurement for trees in smaller diameter classes. West. J. Appl. For. 12(4):108-114.
Document Type: Journal Article
Affiliations: Pacific Southwest Research Station, USDA Forest Service, Redding CA, 96001
Publication date: 1 October 1997
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