i68 Forestry Quarterly. 



D. B. H. (Inches) 2 3 4 5 6 7 8 9 10 11 12 13 14 

 Height (Feet) 14 22 29 37 45 53 61 69 76 82 89 94 100 



D. B. H. 15 16 17 18 



Height 105 109 113 118 



Age-Height-Diameter Growth. 



Applying Graves' modification of Mlodziansky's graphic method 

 of determining the average volume growth of a group of trees 

 to the case of our red pine stand, some 398 measurements were 

 plotted to obtain the curve for diameter growth inside the bark 

 at a height of two feet from the ground ; 261 measurements for 

 a point 18 feet from the ground; 135 for 34 foot point; 128 for 

 the 50 foot point ; and 86 for the 66 foot point. These curves 

 were then transferred to a single sheet of cross-section paper — 

 placing each curve to the right of the zero point as many years 

 as are required to reach the heights at which the diameters are 

 measured. Thus the stump curve is set over 8 years, the one for 

 18 feet above the ground 30 years, etc. The similar shape of the 

 four lower curves at once suggests the method of interpolation 

 for the 26, 42 and 58 foot points, as well as many others at which 

 it may be desirable to know the diameter at any given age of the 

 stand. 



From the set of curves here shown it will be seen that at the 

 age of 150 years the stump diameter inside the bark averages 12 

 inches, the top of the first sixteen foot log 10 inches, the top of 

 the second log 9.2 inches ; of the third log 8 inches ; of the fourth 

 log 5.7 inches- 



Similarly, if it is desired to know at what age a red pine stem 

 will measure 9 inches inside the bark at a height of 50 feet from 

 the ground, an inspection of the 50 foot curve shows it is 173 

 years. 



Age-Volume Growth. 



By combining the results of the Age-Diameter and Diameter- 

 Volume curves we get the following table showing the average 

 volumes of red pine stems for each decade from 60 to 200 years. 



