THE THEORY AND PRACTICE OF WORKING PLANS 127 



1. Selection Method. — The cutting cycle — i.e., the period 

 of return — is of more real importance than the rotation. The 

 cutting cycle, in turn, depends on the time required for repro- 

 duction and on the growth. 



Regulation must be simple to fit the extensive conditions. 

 Volume with an area check is suggested. For volume use : 



Von Mantel's method (No. 2) or 

 Swiss method (No. 4) or ■ 



Heyer's method (No. 9) or 



Hufnagl's diameter class method (No. 12, especially 

 Var. II). 



The choice of methods depends on the available data. 



Methods 4, 9, and 12 may often be employed as a check on each 



^u T- 1-1 total area _ , 



other. For area check use ^ -X volume per acre to 



cuttmg cycle 



be cut. 



2. Shelterwood Method. — In its strict form, this leads to 

 even-aged stands, but may exhibit quasi-cutting cycles if the 

 period of reproduction is long. The determination of the age 

 classes is important. 



In the former case — even-aged stands with rapid reproduc- 

 tion — regulation can be by volume with an area check or by 

 volume and area. For volume use Heyer's formula (No. 9) 

 or even Von Mantel's method of " glorious simplicity " (No. 



A -n total area ^^ , _ , 



2). For area use ^ X volume per acre. For volume 



rotation 



and area use Hufnagl's method based on age-classes and the mean 



annual increment (No. 15) or Chapman's "American method " 



(No. 18). 



The distribution of age-classes, actual and normal, is of 

 great value in judging the needs and the progress of the man- 

 agement. 



If the period of reproduction is so long as to constitute a 

 quasi-cutting cycle, the regulation will be like that for selec- 

 tion method. 



