COMPARATIVE GROWTH. 



11 



were cut into sections varying in length from 2.5 to 10 feet, depending 

 upon the total length of the tree. Each stem was cut into at least 

 three sections. With the trees above 12 inches, cuts were made at 

 intervals of from 10 to 14 feet. The growth data were worked up 

 graphically, according to the method described by Mlodjiansky, 1 and 

 later modified by Graves. 2 



To obtain data for a comparison of the growth of western yellow 

 pine in the two forest types, 110 counts were made on yellow pine 

 stumps of different diameters on a timber sale in the pure yellow pine 

 type. Measurements of clear length and total height were also 

 taken on 800 western yellow pines in each type. , 



DIAMETER. 



The diameter growth, based upon age, of western yellow pine, 

 Douglas fir, and blue spruce is shown in Table 3. It will be seen that 

 the greatest actual diameter growth for yellow pine and Douglas fir 

 occurs at practically the same period, between the ages of 50 and 

 130 years. The greatest actual diameter growth of blue spruce 

 occurs earlier in the life of the tree, between 80 and 90 years. 



Table 3. — Diameter growth of western yellow pine, Douglas fir, and blue spruce. 3 





Diameter breast high out- 







side bark. 





Age. 











Pine. 



Fir. 



Spruce. 



Years. 



Inches. 



Inches. 



Inches. 



10 



0.6 



0.6 



0.4 



20 



1.3 



1.4 



1.1 



30 



2.2 



2.3 



2.2 



40 



3.4 



3.4 



3.8 



50 



4.6 



4.6 



6.0 



60 



6.0 



6.0 



9.2 



70 



7.5 



7.4 



12.3 



80 



9.0 



9.0 



14.8 



90 



10.5 



10.6 



16.8 



100 



12.0 



12.2 



18.4 



110 



13.4 



13,. 9 



19.8 



120 



14.8 



15.6 



21.0 



130 



16.2 



17.2 



22.0 



140 



17.5 



18.8 



22.8 



150 



18.8 



20.4 



23.5 



160 

 170 

 180 



20.0 

 21.2 



22.4 



22.0 

 23.5 

 25.0 









190 

 200 

 210 



23.6 

 24.7 

 25.8 



26.4 

 27.7 

 28.9 









220 

 230 

 240 

 250 

 260 

 270 

 280 

 290 

 300 

 310 

 320 

 330 

 340 

 350 

 360 



26.9 

 27.9 

 28.9 

 29.8 

 30.6 

 31.4 

 32.2 

 32.9 

 33.5 

 34.1 

 34.7 

 35.2 

 35.7 

 36.2 

 36.6 



30.1 

 31.2 

 32.1 

 33.1 

 34.0 

 34.8 

 35.6 

 36.4 

 37.2 

 37..8 

 38.4 











































1 Forest Service Bulletin 20, "Measuring the Forest Crop." 



2 " Forest Mensuration." 



3 Based on stem analyses of 180 western yellow pine, 185 Douglas fir, and 135 blue spruce. 



