INTRODUCTION 



Growth and yield data for pulping species are most meaningful when expressed in units 

 of dry fiber weight . Because grand fir ( Abies grandis Lindl.) is one of the better pulping species 

 in the Inland Empire,^ the growth and yield study of this species conducted by the author was 

 designed to provide data on specific gra^aty at breast height on each ^deld plot. In this report, 

 the prediction equations for converting the breast-height specific gravity to estimates for the 

 entire stem are derived. Three dependent variables are included: 



1 . Average specific gravity of the last 20 years of growth. 



2. Average specific gravity of the stem. 



3. Tree weight in pounds of di^^ matter. 



Each of these variables pertains to the tree stem from a stump height of 1 foot to a top 

 diameter of 3.6 inches inside bark. 



COLLECTION OF TREE DATA 



Field- sampling procedures .--Single-tree samples of grand fir were selected in two steps. 

 In the first step, breast-high cores w^ere taken from trees near the yield study plots. Each tree 

 in this preliminary sample was numbered, and its crowti class and d.b.h. were recorded. 

 Specific gravity of the core was determdned by the procedure described below. From this pre- 

 liminary sample, trees were selected to cover uniformly as wide a range of specific gra\T.ties 

 as possible within crown and diameter classes . 



From the 108 trees so selected, one additional core to the pith and two cores extending 

 through the outer 20 annual rings were taken from the three unsampled quadrants at the breast- 

 height position. The trees w^ere then felled, and seven disks cut from the stem at equal inter- 

 vals starting at the breast -height position and extending upward to the point where the diameter 

 inside bark was 3.6 inches. For trees taller than 100 feet, disks were cut from Lhe top of each 

 16.3-foot log, at breast height, and at the point where diameter inside bark becomes less than 

 3.6 inches. The diameter inside bark of each disk was recorded. The total height, height to 

 base of the live crown, and age at breast height were recorded for each tree. 



Distribution of the sampled trees by diameter and crown class is shown in table 1 . 



^ As used in this paper, the term "Inland Empire" includes northemldaho and northeastern 

 Washington. 



2 



