Method for Regulating Yield. 27 



The proposed treatment in the example should result in nearly 

 equalizing the fellings until the Class IV shall have grown into 

 the exploitable Class I. By placing the surplus of 7 trees of 

 Class III with the deficiency of 21 in Class IV, the net deficiency 

 in the latter class becomes 14. However, 7 of the redistributed 

 trees in that class are larger than is normal for Class IV, and the 

 deficiency in volume will be less than the deficiency in numbers 

 would indicate. A felling at the present time also should result 

 in augmenting Class V^L so that toward the end of the rotation 

 it may be possible to add trees from that class to those in the 

 present Class V and equalize the yield of these two classes. The 

 number of years required to grow a tree 13 inches in diameter 

 into one 16 inches in diameter will determine the cutting cycle, or 

 the years that must elapse before a second felling will be made. 

 The Forest Officer can quite readily prepare a diameter-age table 

 in any timber sale of the species in question and thus determine 

 the number of years required to grow a 13-inch tree into a 16-inch 

 tree. 



When the marking is being done the area can be roughly 

 divided into individual acres on which the marking is done in con- 

 formity with instructions indicated in the analysis illustrated in 

 Table I. Less accurately, one or more acres may be thus carefully 

 worked and the rest marked by judgment based on the carefully 

 marked acres. 



It must be remembered that practical forestry is commonly a 

 compromise between what is best from a purely forester's point of 

 view and what the timber purchaser is willing to do. But the 

 forester should have a definite opinion of what is best from his 

 view point. It is well that his ideas be established on concrete 

 data rather than on surmise. To what extent he is willing to 

 sacrifice good forestry to practical lumbering is a matter which 

 only local conditions can govern. It is even advisable to sacrifice 

 stumpage prices in order to practice good forestry, which in the 

 long run will prove most remunerative. The above analysis 

 should assist him at least in his conception of good forestry. If 

 the data is reliable nothing further is needed as a guide. With 

 a suitable rotation, or exploitable age, involving the proper 

 diameter limit, with the diameter classes properly filled by trees 

 well spaced, the annual growth, or increment, will be normal. 

 Normal increment is the prime object to be attained, for that 

 represents the returns on the investment. 



