176 THE THEORY AND PRACTICE OF WORKING PLANS 



growing stock is estimated by calipering, either all the trees, or 

 certain representative stands, if conditions are sufficiently 

 uniform. The volumes are then calculated from basal area, 

 average height and form factor. The volume of stands of the 

 younger age classes is, if sufficiently regular, taken directly 

 from yield tables, or by means of sample areas.* The incre- 

 ment per cent is usually taken directly from the yield tables. 



The allowed annual cut is then found by dividing the volume 

 of the entire I period by twenty. 



A separate cutting plan for thinnings is drawn up. The cut 

 in thinnings is approximated from past experience. This in 

 eludes the accidental yield through drought and windfall. 



The regulation of selection forests is purposely simplified, 

 since these uneven-aged stands are primarily intended for protec- 

 tion. The division into subcompartments is usually waived; 

 the age classes are only approximated, and the calipering of 

 every single stem is not necessary. The allowed cut for the 

 I period is estimated for each working unit according to the 

 ripeness for cutting. Where the selection forest is a distinct 

 unit of sufficient size (e.g., a block) the average annual incre- 

 ment of the whole is determined and taken directly as the 

 allowed annual cut in so far as there is not a marked excess or 

 deficiency in the growing stock or the condition of the forest 

 or other cogent reasons demand a heavier cutting or vice versa. 

 Where the selection forest has been under regulated manage- 

 ment for some time past, experience will dictate the approxi- 

 mately correct annual cut. 



* The preparation of the working plan is one of the regular duties of the forest 

 supervisor; where necessary, he is aided in the field-work by younger members 

 of the Service (forest assessors, etc.); the rangers do the calipering, etc. It is 

 preceded by a working-plan conference between the district officer and the super- 

 visor. This conference discusses ways and means, is digested and incorporated 

 in the working-plan document (called the " Abschatzungswerk," a bound volume 

 of some 125 pages, manuscript or typewritten, with ample margins for additional 

 notes.) The working plan must be submitted through regular channels, to the 

 Minister of Agriculture, whose letter putting the working plan into effect is incor- 

 porated in the bound volume. 



