THE THEORY ANI> PRACTICE OF WORKING PLANS 121 



both, of the next working period be in reasonable ratio to the 

 total area or volume, or both, of the entire working unit. 

 Modern economic conditions have greatly changed the concept 

 of sustained yield and often demand the cutting of other than 

 the exact period area; the zone of economic influence has 

 extended tremendously. 



(3) Cutting series are not dependent on a period method; 

 indeed the latter often resulted in cutting series of excessive 

 length. 



(4) The assignment of every compartment or other parcel 

 of the forest to a certain period presumes a certainty of judg- 

 ment on the part of the forest organizer amounting to pre- 

 science. As a result the cumbersome calculations are often 

 valueless. 



(5) These calculations of cut for the whole rotation in 

 advance are the m^ore unnecessary since, under proper admin- 

 istration, there are frequent revisions of the working plan at 

 regular intervals. 



Taking all these together, it is a just cricitism of the " frame- 

 work " methods to say that they are too hide-bound, adapted 

 only to even-aged stands, to intensive conditions, and to methods 

 of clearcutting with artificial reproduction. The realization 

 of this has brought about a revulsion from these methods. 

 Most of the German States have definitively abandoned the 

 " framework "; in others it still persists, but without any weight 

 on the determination of cut for future periods (see Part Two, 

 Chapter I). 



18. BY AREA AND VOLUME.— BASED ON PERIODS. AMERICAN 

 METHOD.* 



(a) Description of Method. — Professor Chapman offers this 

 method as a possible standard for regulation in all forests whose 

 increment per acre and age classes can be determined and as 



* Adapted from " Coordination of Growth Studies, Reconnaissance, and 

 Regulation of Yield on National Forests," H. H. Chapman, Proc. Soc. Am. For- 

 esters, Vol. VIII, No. 3, pp. 317-326. 



