THE THEORY AND PRACTICE OF WORKING PLANS 69 



1. BY AREA. 



(a) Description of Method. — The forest or main divisions 

 thereof (working groups, blocks) is divided into a number of 

 cutting areas — annual or periodic^corresponding to the rotation 

 age. These annual or periodic cutting areas are marked on the 

 ground; annually or periodically, a cutting area is logged. The 

 size of the cutting areas is either exactly equal or else is equal 

 to the reduced area corresponding to the varying site qualities. 

 In order to give more accurate expression to the distribution of 

 the age classes, Hufnagl has suggested that each annual cutting 



area be multiphed by the factor: , ,. , — —. — or - 



half the rotation _ r 



2 



thus securing the maximum sustained annual cutting area. 



In selection forest, i.e., a forest through all parts of which 

 many different age classes are represented, the individual 

 area is cut over several times during the rotation, the interval 

 between cuts on the same area being the cutting cycle (cc). 

 Hence in forests managed under the selection method, the annual 



cut = X amount to be removed per acre under the 



cc 



selection cutting. 



(b) Example: — I. Area not reduced. II. Area reduced. 

 III. Hufnagl variation. 



I. A block contains 10,000 acres. It is to be managed on a 



A 



rotation of 60 years. The annual cutting area = — = 166.7 acres. 



If the cutting period is twenty years, then the periodic cutting 

 area will be 166.7X20 = 3334 acres. 



II. By REDUCED area: Each site quahty produces for a fully 

 stocked stand a varying volume at the rotation age. These 

 volumes can either be secured empirically or by means of 

 normal yield tables. E.g., for white pine it has been deter- 

 mined * that the maximum yield (Site 1) ^or a sixty-yeai 



* Table 6, Bulletin 13, U. S. Dept. of Agric, new series, " White Pine under 

 Forest Management." 



