THE THEORY AND PRACTICE OF WORKING PLANS 195 



cide; for the stand growing on a certain site is not necessarily 

 the one best suited to it. 



The age classes are in twenty-year gradations — each age 

 class is again di\aded in half so that the age-class distribution is 

 recorded by decades. 



Owing to the great regularity of the stands, calipering is not 

 ordinarily necessary. Stands less than half of the usual rota- 

 tion of eighty years are estimated from yield tables; stands 

 over forty years old are estimated ocularly and reestimated at 

 each ten-year revision. 



Where clear cutting preponderates, the normal annual cut 

 is taken roughly as the total area divided by the rotation. The 

 proper rotation age is determined by applying the index per 

 cent (Weiserprozent) to the individual stand.* Tables of value 

 increment have been prepared for the whole kingdom of Saxony, 

 based on the prices secured in the open market for the various 

 classes of timber. 



Saxon forestry foots on the soil-rent basis. In order to shov/ 

 the profits of management on this basis, the net income for the 

 whole forest is compared with the total cost of production. 

 This is done, for purposes of forest organization, by determining 

 the timber and soil capital which the forest represents and 

 then showing in tabular form the rate of interest returned 

 thereon for each year by the forest management (Reinertrags- 

 iibersicht). 



The normal annual cutting area is maintained as nearly as 

 may be. Under irregular conditions, departures therefrom are 

 necessary. The table of age-class distribution serves as an 

 index to the degree of departure necessary. If the higher age 

 classes are in excess, the annual cutting area is increased; con- 



* The index per cent, W, is determined by the formula W = (a-\-bztc) 



where a = volume increment, 6 = quality increment, c = value increment or depre- 

 ciation, .4= the arithmetical mean of present and future yield, and S = the soil 

 capital with interest thereon. (For details see Roth: " Forest Valuation," pp. 

 76 to 78.) 



