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UBC Theses and Dissertations

Sampling heights of second growth coastal douglas-fir in fixed area plots Riel, William G.


Knowledge of tree heights is important for classifying sites, projecting growth and yield and estimating stand volume. Tree height is expensive and time consuming to measure so samples should be taken in the most efficient way possible. The impact of different sample designs and sizes on the fitting of height-diameter equations and subsequent prediction of volume is explored in this thesis. Several different height-diameter equation forms were compared for estimating height in second growth Douglas-fir. After selecting the best equation, a variety of simple sampling designs and sizes were compared using this equation. It was found that a uniform design, which was based on sampling tree height uniformly from 3 diameter classes, gave good results for height estimation. A “large” design, which concentrated 50% of its samples in the largest diameter class, gave the best estimates for tree volume. In plots less than 50 years old, it was found that sampling more than 16 tree heights produced diminishing benefits in height and volume estimates.

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