Open Collections

Lo, Hsiao-Chi

University of British Columbia

Critical Height Sampling (CHS) estimates stand volume free from any model and tree form assumptions. Despite its introduction more than four decades ago, CHS is rarely used in the field due to perceived measurement challenges. The objectives of this study were to (1) compare estimated stand volume between CHS and sampling methods that used volume or taper models, (2) assess the equivalence of the sampling methods, and (3) evaluate their relative efficiency. I established 65 field plots in plantation forests of two coniferous tree species in Taiwan. I estimated stand volume for a range of Basal Area Factors (BAFs). Results showed that CHS produced the most similar mean stand volume across BAFs for both tree species with maximum differences between BAFs of 5-18 m³ ha⁻¹. Horizontal Point Sampling (HPS) using volume models produced very large variability in mean stand volume across BAFs with differences up to 126 m³ ha⁻¹. However, CHS was less precise and less efficient than HPS. Furthermore, no sampling methods were statistically interchangeable with CHS at an allowable tolerance of ≤ 55 m³ ha⁻¹. About 72% of critical height measurements were below crown base indicating that critical height was more accessible to measurement than expected. My study suggests that the consistency in the mean estimates of CHS is a major advantage when planning a forest inventory. When checking against CHS, results hint that HPS estimates might contain potential model bias. These strengths of CHS could outweigh its lower precision. My study also highlights significant financial implications when selecting a sampling method, as using a method other than CHS could lead to revenue overestimation or underestimation by US$7,000 per hectare. Lastly, CHS benefits forest management by offering an alternative option of estimating stand volume. CHS could be used as a check when models are not reliable.

Text

2025-03-18

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90498

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/