40 MEASUREMENT OF STANDING TREES. 



These tables rest upon the assumption that trees of the same 

 species, which have reached in the same time an equal height 

 and diameter, show also an equal volume, and that trees of the 

 same species, diameter, and height show volumes which differ 

 with the age of the trees ; in other words, the volume becomes 

 greater with advancing age, although the height and the dia- 

 meter at chest-height may be the same. Foresters say the 

 trees become less tapering, or more full-bodied, or the point 

 where the real tapering commences moves higher up the tree 

 with advancing age. 



In order to use such tables, it is necessary to ascertain the 

 diameter at chest-height, the total height and the approximate 

 age of the tree, when the volume corresponding to these data 

 can be obtained from the tables. It must, however, not 

 be forgotten that the tables give only averages, and conse- 

 quently only true results if used for determining the volume of 

 a number of trees, or of whole woods. 



Note. The Bavarian volume tables are based upon the 

 measurement of 40,000 trees; they give the volumes for 

 spruce, silver fir, larch, oak, beech and birch, arranged into 

 two age classes (up to 90 years, and above 90 years old), 

 the trees having been measured at a height of 4' 3" above the 

 ground. 



Volume tables are now-a-days less used than form factors, as 

 the latter are more handy. 



4. Measurement of Standing Trees by Sections. 



Analogous to the measurement of felled trees by sections, 

 the volume of standing trees can be ascertained by determining 

 the diameter (or girth) at various heights from the ground. 

 For this purpose a man must be sent up the tree, which is a 

 cumbrous procedure, or the several diameters must be deter- 

 mined indirectly. The latter, as has been explained in 

 Chapter I. (p. 12), is subject to great inaccuracies ; hence the 

 method is without practical value. 



