THE THEORY AND PRACTICE OF WORKING PLANS 117 



werk"); II. Volume-period method (" Massenfachwerk ") ; 

 III. Area-and-volume-period method (" Kombiniertes Fach- 

 werk"). 



I. In the area-period method ('' Flachenfachwerk ") the 

 areas are assigned to various periods either as actual areas or 

 as reduced areas (see method No. i above) of equal produc- 

 tivity. The method aims to cut each year, or each period, an 

 equally productive area containing an approximately equal vol- 

 ume. The age-class table is the basis of the assignment to 

 periods, however these must then be shifted to secure equaHty 

 of utiHzation in each period. Knowing the area to be cut in 

 the first (immediate) period and (from yield tables or empirical 

 measurements) the volume }aeld thereof, the annual cut is found 

 by dividing this volume by the number of years in the period. 

 This volume calculation is usually confined to the first period. 

 Final cuttings are restricted to this period. 



1 20 



In a rotation of 120 years there are, e.g., = 6 periods. 



20 



Were the age-class distribution normal, the periods and the age 



limits of the stands comprised therein would be as follows: 



I Period Age of Stands loo-i 20 years 



II Period 80-100 



III Period 60-80 



IV Period 40- 60 



V Period 20- 40 



VI Period 0-20 



In practice this method is restricted to simple, regular con- 

 ditions with artificial reproduction after clearcutting. 



The area " framework " has the advantage of simplicity and 

 ease of application. Within the rotation, if no unforeseen dis- 

 turbances occur, the normal age-class distribution is attained. 

 But the method has the great disadvantage that no due regard 

 is paid to existing conditions (age-class distribution, growing 

 stock, increment). In the case of an overmature, broken stand 

 more should be cut than a strict period method permits; in 

 the case of immature stands, less should be cut than this period 



