Agenda - Environmental Policy Board - 07/19/2021

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Title 190-Forestry Inventory Methods Technical Note Figure 7: Example of a Systematic Line -Plot Sampling Layout for a 10- Percent Sample Using Fixed Plots in a 40-Acre Stand I I Many features of point sampling and fixed plot sampling are identical. • The number and location of plot centers are determined in the same manner. • Methods for determining which borderline trees to sample are the same. • Tree measurements (diameter, height, defects, etc.) are also measured or estimated by methods similar to those used in point sampling. • The primary difference between the two methods is that fixed plot sampling requires measurement of plot dimensions. Also, fixed plots may be less efficient in stands with a large number of small trees, because of the additional time required to measure them. Table 4: Commonly Utilized Dimensions for Fixed Plot Sampling, Showing Radii for Circular Plots Plot Dimensions 1/1000-acre plot = 3.7-foot radius or 6.6 feet x 6.6 feet 1/500-acre plot = 5.3-foot radius or 9.3 feet x 9.3 feet 1/250-acre plot = 7.4-foot radius or 13.2 feet x 13.2 feet 1/100-acre plot = 11.8-foot radius or 20.9 feet x 20.9 feet 1/300 —acre plot = 6.8-foot radius or 12 feet x 12 feet 1/20-acre plot = 26.3-foot radius or 46.7 feet x 46.7 feet 1/10-acre plot = 37.2-foot radius or 66 feet x 66 feet 1/4-acre plot = 58.9-foot radius or 104.4 feet x 104.4 feet 1/5-acre plot = 52.7-foot radius or 93.3 feet x 93.3 feet 1/2-acre plot = 83.3-foot radius or 147.6 feet x 147.6 feet 1-acre plot = 118-foot radius or 208.7 feet x 208.7 feet Strip Sampling In strip sampling, the sample units are continuous strips of uniform width, spaced at a predetermined distance apart. The width of the strips and the distance between the centerline of the strips determines the percentage of the area sampled. (Technical Note No. 190-FOR-01, Jul 2018) 13