This study determined the minimum number of tree heights necessary to obtain an estimate of merchantable plot volume of loblolly pine that, with a probability of 0.95, is within ± 5% and ± 10% of the volume observed when all tree heights on the plot are measured. The size of the height subsample needed to achieve this objective was determined for all combinations of three estimation techniques and four sample designs. The estimation techniques examined were: A. Summation of tree volumes estimated by a merchantable volume equation using tree dbh coupled with a measured or predicted height. Subsample data were used to fit a plot height-diameter regression of the form ln(H)= α + /D, where H is tree height and D is dbh, to predict the heights of trees on the plot but not in the subsample, B. Substituting average D and H values into a merchantable volume equation and multiplying the result by the number of trees in the plot or stratum, and C. Computing the volume-basal area ratio of the subsample and multiplying the result by the total basal area in the stratum or plot. The sampling designs examined were a simple random sample, a stratified random sample, a stratified systematic sample, and a purposive sample. Results indicated that for the ± 5% accuracy level, estimation technique A with a stratified random sample required the smallest subsample size, 12 tree heights. For the 10% accuracy level, estimation technique A with a purposive sample required the smallest subsample size, only 4 tree heights. Recommended subsample sizes are given for all combinations of estimation techniques and sample designs. South. J. Appl. For. 17(3):124-129.
Document Type: Journal Article
Department of Forestry, College of Forestry and Wildlife Resources, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0324
Publication date: August 1, 1993
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Each regional journal of applied forestry focuses on research, practice, and techniques targeted to foresters and allied professionals in specific regions of the United States and Canada. The Southern Journal of Applied Forestry covers an area from Virginia and Kentucky south to as far west as Oklahoma and east Texas.