210 WORKING PLANS 



Under Part I is a head for data of growth and outturn. In 

 most woods such figures will not be available when a plan is 

 first prepared, but the plan may provide for the collection of 

 such statistics, which would be of great value when it is 

 revised in the future ; the woodman may be entrusted with 

 the work. The rate of growth in cubic contents per acre is 

 roughly ascertained from the results of a number of measure- 

 ments made, in the way already described in Chapter XIV, 

 at intervals of five years, throughout specially marked off 

 areas known as ' growth measurement ' or ' sample ' plots. If 

 such measurements are made at regular intervals in woods of 

 different ages, the compiler will be able to judge approxi- 

 mately what amount of timber will be added to a wood in any 

 given number of years, and he will also get some idea of the 

 ' possibility ' of the forest. The possibility is the maximum 

 quantity of material which may, for the time being, be 

 annually removed from a forest consistently with such treat- 

 ment as shall tend to bring the forest as near as possible to 

 the normal state, and with maintaining a constant yield. 



In some plans the compiler fixes the outturn by volume 

 only, laying down that so many cubic feet are to be cut every 

 year, and in this case he must ascertain the possibility in cubic 

 feet. The first estimate can be constantly corrected as time 

 passes, and experience is gained from results. In other plans 

 the above detail is not entered into, and the possibility is 

 merely one by area governed by sylvicultural conditions. 

 This will usually be the case at present in British working 

 plans, the area to be cut each year being laid down ; the 

 possibility in this case is the annual yield, or the volume which 

 can be obtained from the area cut annually. This is ascer- 

 tained by measuring the standing crop in the compartments 

 to be felled, or from the results of previous cuttings in similar 

 woods. 



The woodman will find no difficulty in understanding all 

 that is written in a plan under the remaining heads in Part I. 



