To test the accuracy of current forest sampling techniques, three forest areas were mapped to scale and sampled by 144 sampling designs. Six plot sizes were applied to each of six areal plot shapes. The types of Bitterlich points were examined on a basal area factor of 5, 10, 20, 30, 40, and 50. One type was adjusted for edge bias according to Grosenbaugh's peripheral zone scheme, while the "unadjusted" points were corrected by formula during analyses. All of these sample unit shapes and sizes were then applied to random, systematic, and multiple-random-start distributions. The precision of each method was tested by running an analysis of variance on the sampling error of each design. Accuracy was measured by comparing the estimated means with the actual means. The 1/5th and 1/10th acre plots and the RAF-5 and BAF-10 point-samples were all equal with respect to these two parameters. The distribution design affected precision and accuracy, but not decisively so. On one forest all were equally precise, but the random was the most accurate. On the second forest, precisions were equal but the systematic design was most accurate. On the third forest, all were equally accurate, but the random design was the most precise. The multiple-random-start design was very inaccurate when analyzed by cluster analysis techniques. Grosenbaugh's peripheral zone techniques produced results that were neither precise nor accurate. Precision and accuracy by this method varied universally with the proportion of the population sampled. Plot shape was of no consequence in this study.
Document Type: Journal Article
Assistant Professor of Forest Mensuration, West Virginia University, Morgantown
Publication date: July 1, 1966
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