174 



PRINCIPLES OF AMERICAN FORESTRY. 



A Sample Acre of Jack Pine Shows the Following 

 Stand: 



Diameter, No. Basal 



Breast-Height. Trees. Area. 



2 inches 1 .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 



11 inches 29 29.1400 



12 inches 11 8.6394 



13 inches 9 8.2962 



14 inches 2 2.1380 



15 inches 2 2.4544 



317 141.6357 



Putting all these trees in one class, and dividing the 

 total basal area by the number of trees, the mean basal 

 area is found to be .4468, which would correspond to a 

 diameter, at breast-height, of nine inches. Selecting 

 a tree nine inches in diameter, it is felled and measured 

 accurately, and the volume found to be 11.63 cubic 

 feet. This volume of the sample tree is multiplied by 

 the number of trees, 317, for the total volume on the acre 

 — 3,686.71 cubic feet. Greater accuracy may be attained 

 by taking a sample tree for each diameter size, and a forest 

 may be measured in miniature by felling and measuring 

 a proportionate number of each diameter, say one per 

 cent, of each. i 



The volume of a sample tree, or of sample trees, is often 

 found by applying the factor of shape, which has been pre- 

 viously determined for that particular species and locality. 



The Conversion of Cubic Feet Total Volume of Stand- 

 ing Timber into Feet Board Measure may be done roughly 



