Agenda - Environmental Policy Board - 07/19/2021

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FOREST SAMPLING METHODS 51 Data Analysis: To facilitate comparison, density estimates were summarized on a hectare basis. Stems were classified into two size classes for analysis: 2.54 to 11.42 cm and >11.43 cm. A difference value was obtained by subtracting actual stems/ha from esti- mated stems/ha. Chi-square analysis was used to determine the accuracy of sampling methods (P < 0.05; 13). We also analyzed the data as a randomized complete block design (ANOVA) with stands as the block and sampling technique as the treatments to determine if mean density estimates were different between techniques. Technique means were separated with the protected least significant difference (LSD) test (14). RESULTS As expected, we found wide variation among sample plot estimates within a given technique by stand density. Therefore, we were not able to detect a significant dif- ference in density estimates between samp- ling techniques by using the LSD test (P > 0.05). We found that technique performance was apparently dependent on the size class and distribution of woody stems in a given stand. We did detect differences in accuracy using chi-square analysis. Stems 2.54 to 11.42 cm: The FRP-AC and FRP-HA methods were accurate in the high density stand (x2 = 0.11 and 0.01, respec- tively, P < 0.05; Fig. 1). Both FRP methods underestimated stem density on less dense stands (Fig. 1). The QUAD method was not accurate and underestimated density in both high and moderate density stands, but did produce reasonable estimates in low density stands. The VRP method produced varied estimates across all three levels of stem density and was judged to be unsuitable for small stems (Fig. 1). The BT technique produced more accurate results at low densities than at moderate and high den- sities (Fig. 1). Stems > 11.43 cm: The FRP-AC and QUAD produced accurate (x2 = 3.20 and 1.60, respectively, P < 0.05) estimates of stem density in high density stands (Fig. 2). The BT was somewhat accurate for high density stands (x2 = 4.10, P < 0.10). The QUAD and BT methods produced accurate (x2 = 1.50 and 2.30, respectively, P < 0.05) estimates at TABLE 1. Total time (minutes) required to sample approximately 10% of a hectare various sampling techniques on Pushmataha Forest Habitat Research Summer 1994. Stem Size -Class, Technique a Stems 2.54-11.42 cm FRP-ACb FRP-HA QUAD BT Stems > 11.43 cm PCQ All stems FRP-AC VRP BT High 50 55 63 144 235 160 72 327 Stand Density Moderate 30 34 44 99 104 145 47 225 Low 20 25 41 86 47 137 34 195 using Area, a FRP-AC = fixed -radius plot, 3.64 m radius (0.01 acre); FRP-HA = fixed radius plot, 5.64 m (0.01 ha); QUAD = 10 m X 10 m quadrat, (0.01 ha); VRP = variable -radius plot; BT = belt transect; PCQ = point -center -quarter. b These times for this technique were relative estimates because all stem size classes were counted when applying this technique. Proc. Okla. Acad. Sci. 82:49-56(2002)