METHOD OF PERIODS BY AREA. 313 



first rotation; it may be smaller, equal, or larger than the 

 normal yield. 



An essential part of this method of regulating the yield 

 is the preparation of a framework or general working plan 

 drawn up for one rotation and divided into a number of 

 periods, showing during which period each wood is cut over. 

 The allotment can be made according to area, volume, or the 

 two combined, so that practically three different methods are 

 established, which must be considered separately. 



1. The Method of Periods by Area. 



a. Description of the Method. 



The woods of a forest are so allotted to the several periods 

 of one rotation, that each contains the same, or approximately 

 the same area, called the periodic coupe. 



Where little or no difference exists in the quality of the 

 in the different parts of the forest, the size of each 



A 



periodic coupe will be = , where n represents the number of 



periods in the rotation. If such differences exist, the areas 

 must be reduced to one common quality standard, and the size 



of the periodic coupe becomes = - . Unless this is 



done the periodic yields in the second and following rotations 

 will not be equal. 



In allotting the woods to the several periods, that to be 

 dealt with first receives the oldest woods and those with the 

 most deficient increment, taking into consideration a suitable 

 arrangement of the cutting series ; the allotment to the other 

 periods is made according to the age of the woods, with due 

 consideration to a suitable grouping of the age classes. If 

 then the totals in the several periods differ, shiftings are made 

 by moving certain areas backward or forward, until each period 

 contains the same, or approximately the same area. . 



The woods placed into the first period are measured, their 



