12 



BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. 



and the average tree on each of 14 other sample areas, or a total of 

 559 trees. All the trees of the three crown classes in the stand and 

 on the different qualities of site are represented. Under the influence 

 of all these different factors, which are considered variables in mat- 

 ters of tree growth and volume increment, the size of both diameter 

 and crown spread have been found to vary uniformly and in the same 

 direction. This intimate relationship between tree diameter and 

 crown spread is apparently an expression primarily of tolerance or 

 relative demand of the species for light. 



Table 4 gives the average crown spread in feet of each breast-high 

 diameter class from 5 to 16 inches. It shows a perfect regularity 

 between the size of the tree and the space occupied by its crown, 

 irrespective of age and vigor. 



The table shows that for each increase of 1 inch in tree diameter the 

 crown spread increases 1.4 feet in xirkansas and 1.75 feet in New 

 Jersey. This difference in rate is probably due to the effect of differ- 

 ent climatic conditions upon the tolerance of the species. During 

 earlier life up to about 15 years the relation appears to be in the 

 ratio of 1 foot of crown spread to each inch in tree diameter. 



This law of growth finds practical application in determining for 

 any specified diameter class the total number of trees that can most 

 profitably be grown per acre in a well-stocked stand. Since diameter 

 is a direct function of age in any given quality of situation, the tree 

 density on the ground at any desired age can likewise be ascertained. 

 Knowledge of this sort is fundamental in working out problems of 

 thinning, cutting, and final yields of timber. 



Table 4. — Relation of tree diameter and crown diameter for shortleaf pine trees in fully 

 stocked stands for all ages from 20 to 80 years — Contrast of regional difference for 

 Arkansas and New Jersey. 





Crown diameter. 





Favorable region (Arkansas). 



Unlavorable region (New 

 Jersey). 



Tree diameter breast high (inches). 



Crown 

 diameter. 



Amount 



of 

 increase. 



Differ- 

 ence in 

 crown 

 diamtter 

 and tree 

 diameter. 



Crown 

 diameter. 



Amount 



of 

 increase. 



Differ- 

 ence in 

 crown 

 diameter 

 and tree 

 diameter. 



5 



Feet. 

 5. 2 



Feet. 



1.4 

 1.4 

 1.4 

 1.4 

 1.1 

 1.1 

 1.4 

 1.4 

 1.4 

 1.4 

 1.4 



Feet 



■1. s 

 6.1 

 7.4 

 8.7 

 10.05 

 11.4 

 12.7 

 11 



15.3 

 16.6 

 17.95 



Feet. 



3.25 



5 



6.75 



8.50 

 L0.25 

 12 



13. 7.5 

 15.50 



F<it. 



/■',,/. 

 ■j. 85 



6 



6.6 



8 



9.1 

 10.8 

 12. 2 

 13.6 

 1.5 

 16. -1 



1.75 



1.75 

 1.75 

 1.75 



1.75 

 1 . 7.5 



1.75 



1 .5 



7 



8 



9 



10 



11 



12 



13 



6. 15 

 7.8 

 9. .5 

 11.21 

 12.85 

 14.5 



14 17. S 









15 19.2 









lii !0.fi 



19.3 



















