On critical-height sampling

Abstract

Critical-height sampling is shown to provide unbiased estimates of per-acre cubic volume if the sample trees are selected at stump height to determine if they are to be tallied. Selection at breast height implicitly assumes that the tree is a cylinder from breast height to stump height. It is also shown that unbiased estimates of merchantable volume can be obtained with critical-height sampling. The relationship between variances from critical-height sampling and the usual horizontal point procedure requiring volume estimates is shown to depend on tree spatial patterns. This is also true for growth estimates. A definite benefit of critical-height sampling is that no volume equation is needed.