8 Forestry Quarterly. 



tlie form of the stem, and being a factor easily determined with 

 tolerable accuracy. 



When used with judgment these tables have proved of very 

 great value in practical forestry operations greatly lessening the 

 labor of determining the volume of stands inasmuch as they do 

 away entirely with the necessity of sample trees, the volumes of 

 the trees in the various diameter and height classes being read 

 directly from the table. They are of course not used and not in- 

 tended for use in the determination of volume in single trees, for 

 trees of the same age, height and breast-high diameter growing 

 side by side in the same stand sometimes vary in cubic content 

 by 20 ''/c or even more. In a stand that is approximately an 

 average stand, however, these individual variations compensate, 

 and a very .satisfactory average result may be obtained. 



Unfortunately, even in Germany with its intensive management, 

 variations of a very marked character occur in the form of the 

 average stem due to other causes than age. Where, as in America, 

 the forests have developed without care and the silvicultural con- 

 ditions are merely a result of natural forces and where great 

 variations in age occur even on very limited areas making age 

 classes impossible, these variations are of much more frequent 

 occurrence. The weakness of a table founded on height, diame- 

 ter, and age classes is shown in that it is incapable of adapting 

 itself to any variation in the average form of the .stem aside from 

 that caused by age. 



In an effort to overcome this difficulty Schuberg ' in 1891 pre- 

 pared "correction tables" by means of which it was possible 

 to take into consideration the changes in the form of stems due 

 to the various and often varying factors of site and silvicultural 

 conditions. These tables prescribed that a percentage be added 

 to or deducted from the amount read in his volume tables for the 

 Silver Fir according as the stems proved of more or less cylindrical 

 in form than normal. This variation in the form was determined 

 by comparing the relation between the breast-high diameter {d) 

 and the diameter at the middle of the stem (8). The propo.sition 

 that any variation in the cubic content of the boles of trees of 

 equal height and diameter, must show it.self in a more or less 

 cylindrical form of these boles, seems impregnable. That this 



' Formzahlen und Massentafeln fur die Weistanne, Berlin, 1S91. 



