66 



MISC. PUBLICATION 11, U. S. DEPT. OF AGRICULTURE 



the growth rings get narrower the tree may still be putting on more increment 

 than when the tree was smaller and growth rings wider. It is important not to 

 confuse the two, because in general a larger proportion of desirable and valu- 

 able products are secured from the larger trees. But when increment ceases 

 to increase satisfactorily, the tree has reached commercial maturity and ordi- 

 narily should be harvested. "Maturity" throughout this statement is used 

 with this meaning. 



The following tabulation, based on the local volume table for Engelmami 

 spruce, illustrates this point and will be found helpful in determining the 

 maturity of any tree: 



Nii/niher of rings in outside inch required to maintain uniform rate of volume 



increment in the tree 



D. b. h. (inches) 



Number of 

 rings per inch 



required to 



show a growth 



rate of 5 



board feet 



per year 



Number of 

 rings per inch 



required to 



show a growth 



rate of 1 



cubic foot 



per year 



D. b. h. (inches) 



Number of 

 rings per inch 



required to 



show a growth 



rate of 5 



board feet 



per year 



Number of 

 rings per inch 



required to 



show a growth 



rate of 1 



cubic foot 



per year 



6 







20 - — .. 



20 

 24 

 27 

 30 

 33 

 36 

 40 



17 



8 





I 



10 



22 



19 



10 



4 



7 



11 



14 



17 



24__ 



21 



12 



26 



■^3 



14 .- 



28--^ 



30--- 



* 25 



16 



28. 



18 



32-_ 



30 









The point at which commercial maturity is attained varies with species, site, 

 and market requirements. Some stands are commercially mature at prop size, 

 others at railroad-tie size, while still others, possibly of the same species, can 

 be most profitably held for saw-timber production. Each stand is a problem 

 in itself and requires special consideration and skill, on the part of the marker 

 if the desired results are to be attained. The marker should examine each tree 

 closely and his conclusions should be based on external appearances, checked 

 sufficiently by use of the increment borer. 



Conditions on the ground, after cutting and brush disposal are completed, are 

 what count. This principle should be kept in mind in determining the marking 

 policy for a given sale, and sacrifice should be made in stumpage rather than in 

 desirable silvicultiiral, practice. 



MARKING PRACTICE 



Marking in all types will follow the selection system. Only in clearly defined 

 cases where different treatment is justified because of fire or wind damage, 

 insect injury, disease or decadence, or stagnation beyond point of recovery, 

 will this practice be departed from. The object in all marking is to harvest the 

 commercially mature and overmature timber and to remove defective, diseased, 

 or overcrowded trees in the younger age classes. 



Diameter guides. — Diameter guides are intended merely to give forest officei*s 

 inexperienced in marking in a given type of timber a general, idea of the 

 average sizes at which the dilferent species reach commercial maturity. These 

 guides are not intended to be applied mechanically, and care will be necessary 

 to see that marking officers understand their application. The size at which 

 maturity is reached will vary widely with conditions of site and growth, and 

 marking must be based upon a close examination of each tree. 



Vary markinff. — One of the chief faults in marking practice is failure to 

 change the marking when the character of the stand changes. In passing from 

 a thrifty mature stand to a pole or overmature stand the marking must change 

 abruptly. On ridges and otherwise poor sites, trees virtually stop growing at 

 smaller diameters than on good sites, and the marking must vary accordingly. 



Defects of various kinds often furnish sufficient reason for taking out trees 

 that are approaching maturity or certain trees located in stands where there 

 is an opportunity to practice selection. However, the same defects occurring 

 on younger trees mny not be of sufficient importance to warrant their removal 



