Agenda - Environmental Policy Board - 07/19/2021

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Comparative Evaluation of Accuracy and Efficiency of Six Forest Sampling Methods Jeffrey C. Sparks' and Ronald E. Masters2 Department of Forestry, Oklahoma State University, Stillwater, OK 74078 Mark E. Payton Department of Statistics, Oklahoma State University, Stillwater, OK 74078 'Current address: Texas Parks and Wildlife Department, Tyler, TX 75707 2Current address: Tall Timbers Research Station, Tallahassee, FL 32312 We compared estimates of woody stem density with known stem densities in three forest stands in southeast Oklahoma by using fixed -radius plots 3.64 m radius (0.01 acre; FRPs-AC), fixed -radius plots 5.64 m radius (0.01 ha; FRPs-HA); 10 m X 10 m quadrat (0.01 ha; QUAD), variable -radius plot (VRP), point -centered quarter (PCQ), and belt transect (BT) sampling techniques. These stands varied in stem density and were categorized as high, moderate, and low density stands. We found that FRPs were the most time -efficient and produced the most accurate estimates regardless of stem size. The VRP and PCQ methods were also time - efficient, but tended to underestimate actual stem density. Although FRPs of suitable size are accurate for large diameter stems in dense forest, time constraints limit applicability. We recommend using FRPs for small stems [(2.54- 11.42 cm diameter breast height (DBH)] and VRPs for large stems (>11.43 cm DBH). These methods with appropriate sample sizes should be applied after pre -sampling has been completed to determine sampling variance. This combination of methodologies provides a quick and relatively accurate manner to characterize or monitor change in the wide range of forest conditions found in Oklahoma. ©2002 Oklahoma Academy of Science INTRODUCTION Quantitative data are essential to adequately characterize the woody component of forest communities (1,2). Some form of sampling is required because total counts of in- dividuals in naturally occurring plant populations are generally impractical without an exhaustive expenditure of energy and resources (3). A number of sampling techniques are available to quantify forest communities. These techniques vary in quantitative capabilities, equipment re- quired, and time necessary to obtain an adequate sample for statistical analysis (4,5). Obtaining adequate information with minimum effort and time is a major concern when sampling vegetation (4,5). Variable radius plot (VRP), fixed radius plot (FRP), point -centered quarter (PCQ), belt transect (BT), and 10 m X 10 m plots (QUAD) are sampling methods commonly used to quantify forest vegetation (2-6). The purpose of this study was to determine the best sampling method for use in widely varying forest conditions that would adequately characterize forest communities in Oklahoma for the purpose of monitoring change in the woody component following either experimental manipulation or land use change. Our primary objective was to compare the accuracy of estimates of woody stem density for six forest sampling tech- niques under widely varying stand den- sities. A second objective was to compare Proc. Okla. Acad. Sci. 82:49-56(2002)