116 THE l-HEORY AND PRACTICE OF WORKING PLANS 



distribution of the age classes, but this very desirable goal is 

 attained without undue sacrifices. 



It is a method of great freedom and adaptability. Freedom 

 in so far as the cutting of certain stands is not prescribed far in 

 advance for a certain time, but entirely according to the exi- 

 gencies of the situation. It is adaptable to all methods of high 

 forest which result in even-aged or fairly even-aged stands, 

 i.e., to all but the selection system. 



The method in its simple application is well suited to Amer- 

 ican conditions where it is often of prime importance to dispose 

 of the overmature and decadent timber within the reasonable 

 check of a sustained volume yield aided by the corrections of 

 decennial redetermination of the cut, and to work toward the 

 distant goal of a normal age-class distribution. 



17. BY AREA AND VOLUME.— BASED ON PERIODS (" FACH- 

 WERKSMETHODEN " *). 



(a) Description of Method. — The rotation is divided into a 

 number of equally long periods of time. Usually these periods 

 comprise twenty years. Every compartment or subcompart- 

 ment is assigned to a period corresponding with its age, so that 

 each part of the entire area of the working unit, with the ex- 

 ception of certain areas reserved for selection forest, protec- 

 tive belt, or other special purpose, is used once during the 

 rotation. 



The sums of the individual periods must be approximately 

 equal, or somewhat higher for the later periods. If this is not 

 the case, adjustment is necessary, by transferring certain 

 stands or subcompartments to an adjacent period. Accord- 

 ing as this adjustment emphasizes equality of area, or equality 

 of volume, or equality in both, different kinds of period methods 

 are recognized as: I. Area-period method (" Flachenfach- 



* The name " Fachwerksmethoden " comes from the German " Facher " 

 or pigeon-holes into which the various parts of the forest are placed by these 

 methods. A " Facherwerk " or " Fachwerk " is, therefore, a framework con- 

 sisting of many pigeon-holes, and these methods are " Framework " methods. 



