COMBINATION VOLUME TABLES 193 



164. Combination Volume Tables for Two or More Products. 



Close utilization of tree volumes requires the measurement of two or 

 more classes of products, such as saw timber and residual cordwood, 

 saw timber and residual mine props, railroad ties and residual mine 

 props. 



In all tables of this class, the method of construction is to determine 

 the diameter which limits the sizes used for the higher purpose, and then 

 to measure the contents of the remainder of the bole to the smaller 

 diameter which limits the sizes used for the residual product. The 

 measurements must be taken on the felled tree before any portion is 

 skidded off. 



For example, in constructing a sawlog, tie, prop table for lodgepole 

 pine, on the Arapahoe National Forest, Colorado, 6 inches was used 

 as the top diameter for sawlogs, to be scaled by Scribner Decimal C 

 log rule. Five inches was the top diameter for mine props. The 

 number of feet remaining in the top, between 6 and 5 inches, was 

 recorded as linear feet. In the same manner, 10 inches was fixed as 

 the top diameter for the production of hewn ties (this has now been 

 lowered to 8.5 inches by new specifications), and the number of ties 

 in each tree, to this point, recorded. Above 10 inches, the 8-foot 

 lengths are entered as prop material.^ 



The residual cordwood in the tops of trees cut for sawlogs or ties 

 is measured as for cubic feet. Where the volumes for the more valu- 

 able product are measured to a fixed top diameter, the problem of resid- 

 ual volume is easily solved. Where top diameter varies with other 

 factors, the amount of cordwood in the tops varies accordingly. This 

 variation is further increased when branch-wood or lapwood is included. 

 Tables usually express the volume of residual cordwood in terms of 

 decimal fractions of cords per tree, and the data are frequently simplified 

 by averaging the contents on basis of diameter. 



165. Graded Volume Tables. A graded volume table is an attempt 

 to show the amount of different standard grades of lumber which may 

 be sawed from trees of different dimensions. Its purpose is to aid in 

 estimating the value of standing timber. The preparation of graded 

 volume tables is one of the objects of mill-scale studies (§ 74). The 

 basis of these tables is the sawed lumber produced from logs. To 

 coordinate these data with the volume of standing trees, the following 

 points must be 'considered : 



1. The logs sawed are usually cut into variable log lengths and 

 cannot be standardized to a given length, such as 16 feet. 



2. In sawing logs, especially hardwoods, the resultant output will 



1 Ref . Volume Table for Lodgepole Pine, A. T. Upson, Forestry Quarterly, 

 Vol. XII, 1914, p. 319. 



