Differences in fixed-radius plot sample size estimates when using the inherent variability among diameter classes in stand tables rather than average values

This article is part of a larger document. View the larger document here.

  • Authors: VanderSchaaf, Curtis L.
  • Publication Year: 2020
  • Publication Series: Proceedings - Paper (PR-P)
  • Source: e–Gen. Tech. Rep. SRS–253. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station

Abstract

As part of many forest inventories, sample sizes needed to meet some desired level of precision are estimated. In many timber inventories, based on estimates of the inherent variability (e.g., coefficient of variation, CV), sample sizes are estimated for average total merchantable volume or for the most valuable product class such as average sawlog volume. However, often foresters are equally interested in producing accurate and precise stand tables. Stand tables contain number of trees by diameter and/or height classes while stock tables contain amount of volume by diameter and/or height classes. The most important component of most timber prospectuses in the Southeastern United States is actually stand and/or stock tables, not average values. This study attempted to quantify differences in sample size estimates of fixed-radius plots when using variability among diameter classes in stand tables as opposed to the variability in average values in the sample size equation. Several methods were proposed to quantify the CV among diameter classes within stand tables. Fixedradius plots of varying sizes from many inventories conducted across the Southeastern United States and a few from other parts of the country were examined. In most cases, sample sizes needed for stand tables were at least twice as large when compared to estimating average trees per acre. However, when using Method Four at an 80 percent probability, sample size estimates (n = 27) were similar to sample sizes for average volume per acre at 95 percent probability (n = 29).

  • Citation: VanderSchaaf, Curtis L. 2020. Differences in fixed-radius plot sample size estimates when using the inherent variability among diameter classes in stand tables rather than average values. In: Bragg, Don C.; Koerth, Nancy E.; Holley, A. Gordon, eds. 2020. Proceedings of the 20th biennial southern silvicultural research conference. e–Gen. Tech. Rep. SRS–253. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station: 19-25.
  • Keywords: stand tables, stock tables, forest inventory
  • Posted Date: September 14, 2020
  • Modified Date: September 16, 2020
  • Print Publications Are No Longer Available

    In an ongoing effort to be fiscally responsible, the Southern Research Station (SRS) will no longer produce and distribute hard copies of our publications. Many SRS publications are available at cost via the Government Printing Office (GPO). Electronic versions of publications may be downloaded, printed, and distributed.

    Publication Notes

    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
    • Our online publications are scanned and captured using Adobe Acrobat. During the capture process some typographical errors may occur. Please contact the SRS webmaster if you notice any errors which make this publication unusable.
    • To view this article, download the latest version of Adobe Acrobat Reader.