Hardwoods growing in close proximity have been observed to have a wide range in Girard form class. Accurate determination of Girard form class can therefore be important in getting accurate estimates of hardwood timber volume. However, the cost of estimating Girard form class for every tree being measured in the stand would be prohibitively expensive. Thus, estimation of average Girard form class for a stand is considered here. Three instruments used to estimate Girard form class a Wheeler pentaprism optical caliper, a wedge prism, and a Spiegel relaskop were compared to direct measurement.
Direct measurement requires the fewest trees to achieve the desired results.
However, it requires considerably more time per tree than any of the instruments tested. The Wheeler pentaprism requires only a few more trees than direct measurement, and considerably fewer trees than either the wedge prism or the Spiegel relaskop. Use of all three instruments is hindered when understory vegetation obscures the top of the first log. Hydrologic Impacts of Logging an Appalachian Watershed Using West Virginia's Best Management Practices J.N. Kochenderfer, P.J. Edwards, and F. Wood. Both growing season peakflows and total stormflow had small but significant increases due to treatment.