MEASUREMENT OF GROWING STOCK. 137 



MEASUREMENT OF GROWING STOCK. 



The Growing Stock of a Forest, or Volume of Stand- 

 ing Timber, is equal to the sum of the volumes of all the 

 trees. Where the tract is small caliper all the trees, or if the 

 tract is large caliper all the trees on a small sample area selected 

 as typical of the whole. If each species is in uniform stand, 

 separation into species classes will be sufficient, but where much 

 difference exists between individuals of the same species, due 

 to conditions of growth, diameter and height classes in each 

 species should be formed, and the volume of each class com- 

 puted by itself. From the diameters obtained by calipering at 

 breast height the average basal area is determined in each class, 

 and trees of corresponding diameters in each class are felled and 

 measured accurately. The volume of a sample tree, or the mean 

 volume of several sample trees, times the number of trees, gives 

 the volume of that class, and the sum of the volumes of the dif- 

 ferent classes is the total volume of timber on the tract. The 

 more sample trees that are measured the more accurate will be 

 the results, as trees vary so much in shape that quite different 

 volumes may be obtained for two trees of the same diameter and 

 height. 



A Sample Acre of Jack Pine Shows the Following 

 Stand : 



Diameter, Basal 



Breast Height. No. Trees. Area. 



2 inches i .0218 



3 inches 6 .2946 



4 inches 6 .5238 



5 inches 16 2.1824 



6 inches 33 6.4779 



7 inches 40 10.6920 



8 inches 60 20.9460 



9 inches. . 56 24.7408 



10 inches 46 25.0884 



1 1 inches 29 29. 1400 



12 inches ! i 8.6394 



13 inches 9 8.2962 



14 inches 2 2.1380 



15 inches 2 2.4544 



317 141.6357 



