CONTENTS OF STANDING TREES BY SHORT METHODS 27 



3. Estimate, checking the estimate occasionally with hypsometer, the 



height from stump up to 5 D.B.H. outside bark. 



4. Tally these three measurements on Form 3 A, using one vertical 



column for each species. On the left-hand side of the column, 

 opposite the proper D.B.H. class, enter the width of bark and on 

 the right-hand side the height up to | D.B.H. for each tree cal- 

 ipered. 



5. From these field measurements compute the volume inside bark 



of each tree from the formula . 

 Method H. — By tallying the D.B.H. of each tree and securing heights 

 from a height curve. 



1. Caliper D.B.H. outside bark of the trees whose volumes are to be 



computed. 



Note. — When the D.B.H. of a tree falls at a point where the bole is swell- 

 butted the measurement should be reduced so as to give the tree the average 

 amount of taper which in the judgment of the cruiser the conditions will 

 warrant, for otherwise the formula will give results too high. 



2. Take measurements of D.B.H., width of bark, and merchantable 



length to ^ D.B.H. on at least 30 fallen trees of various sizes. 



3. From these measurements construct a height curve showing mer- 



chantable heights for different diameters breast high outside bark. 



4. Using an average width of bark for each D.B.H. and with heights 



obtained from the height curves, compute volumes inside bark 

 with the Spaulding Log Rule, for trees 20, 30, 40, 50, 60, 70 inches 

 D.B.H. outside bark. 



5. Plot the volumes of the sizes thus computed, connect with a curve, 



and read off the volumes of the intermediate diameters breast 

 high outside bark. 



6. Tally the volumes thus obtained in tabular form, and use this table 



for computing the volumes of trees calipered. 

 Illustration 2. — To Compute the Contents of Standing Trees in Board Feet 



by the Doyle Rule. 

 Explanation. — The Doyle Rule is simpler than the one described above but 



is not accurate for Pacific Coast timber, since it will give high results, as is 



the case when this rule is used with large-sized logs in any region. The 



rule follows : 



Volume of tree = ( — — - ) XL. 



m 



D = middle diameter inside bark obtained by averaging the diameters at the 



top and base of the merchantable length of the tree; 

 L = merchantable length. 



Directions. 



To apply the Doyle Rule follow Illustration I, Method I, described above, 

 except that the middle diameter should be tallied instead of D.B.H. 



