# An evaluation of the use of tarif tables in second growth Douglas-fir

for a particular stand. To find the tarif number, total stem cubic-foot volume and the diameter at breast height are needed for each sample tree. In this report, three volume equations that could be used to calculate tarif tested on an independent data set of sectioned young growth Douglas-fir (Pseudotsuga menziesii (mirb.) Frcrnco) trees for their accuracy to predict volume. The percent difference of the means and a modified chi-square test

were used to evaluate the Weyerhaeuser, Bruce-DeMars, and British Columbia (immature) cubic-foot volume equations. It was found that the first two equations predicted volume well and gave very comparable results while the third consistently underestimated volumes. Error limits are reported so that each equation can be evaluated to see if it meets desired accuracy criteria. Graphical analysis was used to further look at the effects of measurement errors on the calculation of tarif numbers and eventually on volume estimates. Accuracy must be considered for each circumstance; however, in some cases measurements may not have to be as accurate as presently suggested. It was found that diameter measurements are not as important as height measurements. Also, measurements to obtain tarif must be much more accurate if Scribner volume is desired as compared to total stem cubic-foot volume. Finally, further research needs for realizing the full

potential of the tarif system are discussed.

Advisor:Bell, John F.; Paine, David P.; Brodie, J. Douglas

School:Oregon State University

School Location:USA - Oregon

Source Type:Master's Thesis

Keywords:chambers charles j comprehensive tree volume tarif tables forests and forestry mensuration douglas fir

ISBN:

Date of Publication:05/04/1981