86 



BULLETIN 544, V. S. DEPARTMENT OF AGRICULTURE. 



For purposes of comparison Tabic 13, giving diameter growth of 

 Norway spruce (Picea excefrsa) is included. 



Table 13. — Diameter growth of Norway spruce. 1 

 [curved.] 





Average 



Age. 



diameter 



breast high 





of stand. 



Years. 



Inches. 



5 



1.0 



10 



2.8 



15 



4.4 



20 



5. 7 



25 



6.8 



30 



7. 7 



35 



S.4 



40 



9.0 



45 



9.6 



50 



10.2 



55 



10.8 



60 



11.4 



1 Based on the measurement of all trees in 11 plantations (8 Qualities I and 3 Quality II) 24-55 years 

 old, made by Messrs. Tillotson, Barrows, and Williamson in 1911, in Rhode Island, Connecticut, Illinois, 

 and Iowa. 



Even more than with height comparisons it is necessary to bear 

 in mind the influence of soil, spacing, and cultural methods on the 

 diameter growth of volunteer stands and plantations when drawing 

 conclusions from the foregoing figures as to the relative growing 

 qualities of red and Norway spruce. 



SECTIONAL AREA GROWTH. 



The growth in sectional area, or the increase in the superficial 

 area of a given cross section, is effective as a means of comparison 

 for even-aged stands of different ages or of the same age but of 

 different site qualities. Either the total basal area of the stand at 

 a definite height from the ground, usually at breastheight, or the 

 basal area of the average tree, may be employed. Table 14, covering 

 second-growth, even-aged spruce stands of the old pasture type 

 shows the relative average total basal area of stands of different 

 ages and site quality based (1) on all green trees; (2) on green trees 

 6 inches and over; (3) on all dominant trees; and (4) on all domi- 

 nant and intermediate trees. 



