174 THE THEORY AND PRACTICE OF WORKING PLANS 



i8 Unstocked blanks. 



19 Cutting area of the I period, in hectares. 



20 Cutting area of the II period in hectares. 



21 Silvicultural method to be used. 



22 Species to be reproduced. 



23 Remarks. Explanations of measures adopted. 

 Reasons for departures from the usual rotation 

 age. 



The block and the ranger district usually coincide. Working 

 groups (" Betriebsklassen ") are segregated whenever there are 

 salient differences in species, rotation, or method of management. 



The block is subdivided into rectangular units called 

 " Jagen " (" hunts ") in the plains, " Distrikte " (" districts ") 

 in the mountains. The boundaries are roads or topographic 

 features (ridges, streams, etc). The average size in pine stands 

 is from 49.4 to 74.1 acres; in spruce stands, from 24.7 to 49.4 

 acres. 



Subcompartments are not segregated for minor differences, 

 and never for less than 2.47 acres (i hectare). 



To insure continuity of records the numbers and boundaries 

 of blocks, compartments, etc., are not changed except for urgent 

 reasons. 



The soil and rock description is usually taken directly from 

 the geological survey maps. 



The site quaUty is usually gauged by means of the average 

 height as given in ^-ield tables pubhshed by the experiment 

 station. The average height is determined by hypsometer 

 measurements of trees in representative stands or, where less 

 important, merely estimated. 



In uneven-aged stands in which the age classes blend one 

 into the other, the age limits and average age are indicated; 

 where the age classes are widely divergent (e.g., very young and 

 mature) they are entered separately. Great weight attaches 

 to the age class and area table. 



The criterion of cutting the sustained >deld is the normal 

 area of the period. This is determined by the proportion of the 



