TAPER TABLES, DEFINITION AND PURPOSE 197 



classes are distinguished. In tables based upon diameter and height 

 only, no record of form is shown. The volumes as given in the table 

 do not indicate whether the tree is full-boled or conical. This draw- 

 back is further aggravated by the use of board-foot log rules whose 

 values are not interchangeable. 



167. Taper Tables, Definition and Purpose. There are two methods 

 for recording differences in the form of trees, form tables or taper tables, 

 and form classes or form factors. 



A table which does not show the volume of the tree, but shows 

 the actual form by diameters at fixed points from base to tip, is com- 

 monly termed a taper table. From such a table, the volume of the aver- 

 age tree for each diameter and height class can be measured as readily 

 in the office as from the felled tree. Tables of volume can thus be 

 constructed from a taper table, using any desired unit of product, 

 such as cubic feet, board feet or piece products. They therefore form 

 the basis for any required future volume table. For this reason, if 

 taper measurements are taken at regular intervals, preferably 8.15 feet, 

 from stump to top of tree, they constitute a permanent scientific record 

 of tree form which will make it unnecessary to measure felled trees 

 again for new volume tables. 



168. Methods of Constructing Taper Tables. Taper tables are 

 based on total height and hence they should record the form of the 

 entire bole. 



A separate table is required for each height class showing the taper 

 of trees of each diameter in this class; e.g., for white ash ^ tapers are 

 shown for trees of 10-foot height classes from 30 to 120 feet. 



For each height class, and D.B.H. class, the diameter of the tree 

 inside bark must be given at each fixed point, 8.15 feet or multiples 

 thereof above the stump. 



The bole, below D.B.H. , tapers much less regularly than above 

 that point, but a complete taper table should give the average diam- 

 eter inside bark preferably at 1, 2, 3 and 4 feet from the ground. 



In Table XXXIII, p. 198, stump tapers are given, the diameter inside bark 

 at B.H. and the upper diameters at 8.15-foot intervals from stumps taken as 

 uniformly 1 foot high. But one class is shown, namely, 90-foot trees. A similar 

 table is constructed for trees of each separate height class, such as 80-foot or 70-foot 

 trees. 



When the taper measurements have been taken at fixed points 

 on all trees, the average diameters at these points may be obtained 

 directly from the original data. The process is shown in Table XXXIV. 



' Bui. 299 U.S. Dept. Agr., The Ashes, W. D. Sterrett. 



