BLACK WALNUT: ITS GROWTH AND MANAGEMENT. 



25 



to 150 years at least. The age to which individual walnut trees could 

 be best grown, from the standpoint of greatest volume production, is 

 probably limited not so much by an ultimate decrease in the rate of 

 volume growth as by the setting in of butt rot. The average age at 

 which logs are cut at the present time is 80 or 90 years — a period at 

 which the tree is making rapid growth. 



Table 5. — Volume groivth of Mack tcalnut. 







Average 



Current 



Age. 



Volume. 



annual 



annual 







growth. 



growth. 1 





Board 



Board 



Board 



Years. 



feet. 



feet. 



feet. 



50 



48 



1.0 





60 



100 



1.7 



5.2 



70 



150 



2.1 



5.0 



80 



200 



2.5 



5.0 



90 



260 



2.9 



6.0 



100 



320 



3.2 



6.0 



110 



380 



3.5 



6.0 



120 



440 



3.7 



6.0 



130 



505 



3.9 



6.5 



140 



565 



4.0 



6.0 



ISO 



635 



4.1 



7.0 



1 Average annual growth for each decade. 



RELATION BETWEEN RATE OF GROWTH IN DIAMETER AND THE 

 FORMATION OF SAPWOOD. 



The thickness of the sapwood depends very largely upon the 

 rapidity of growth, the trees which have grown most rapidly having 

 the widest sapwood. For this reason thrifty young trees are more 

 likely to have wide sapwood than old trees. Local differences in site, 

 however, frequently modify the tendency to vary with rapidity of 

 growth. Trees from certain regions are notoriously sappy, but from 

 other places the percentage of black heart is uniformly high. The 

 relation of rapidity of growth to thickness of sapwood is shown in 

 Table 6, which is based on 124 logs from widely scattered points. Of 

 those trees in which the rate of growth was about the average the sap- 

 wood contained from 12 to 14 annual growth rings. 



Table 6. — Thickness of sapwood: 



Growth 



Thick- 



Years 



Growth 



Thick- 



Years 



Growth 



Thick- 



Years 



last 



ness of 



in 



last 



ness of 



in 



last 



ness of 



in 



decade. 



sapwood. 



sapwood. 



decade. 



sapwood. 



sapwood. 



decade. 



sapwood. 



sapwood. 



Inches. 



Inches. 





Inches. 



Inches. 





Inches. 



Inches. 





0.2 



0.3 



25 



0.9 



1.2 



14 



1.5 



1.9 



13 



.3 



.4 



20 



1.0 



1.4 



14 



1.6 



2.0 



13 



.4 



.7 



18 



1.1 



1.5 



14 



1.7 



2.1 



12 



.5 



.8 



16 



1.2 



1.6 



13 



1.8 



2.2 



12 



.6 



.9 



15 



1.3 



1.7 



13 



1.9 



2.4 



12 



.7 



1.0 



14 



1.4 



1.8 



13 



2.0 



2.5 



12 



.8 



1.1 



14 















1 Based on measurements of 124 logs. 



