FOREST MANAGEMENT 135 



there will be 6 Periods, in each of which 2,000 acres 

 will be dealt with that is to say, an average of 100 acres 

 per annum. 



If differences in the quality of soil or situation occur, the 

 areas may be reduced to one common quality standard. 



The advantage of the allotment system is that it is more 

 elastic than mere division into fixed annual coupes. Under 

 the system of " Periods," the wood manager is at liberty 

 within limits to determine the area of the year's felling. 



Allotment by Volume. The method of allotting the 

 woods into Periods by volume is made according to the an- 

 ticipated yield (growing stock and increment), so that the 

 total quantity of produce from each Period may be nearly 

 the same. The system of volume allotment has found but 

 little support in practice, owing to the difficulty, and indeed 

 impossibility, of determining the yields far into the future 

 with sufficient accuracy. 



Combined Method. An improvement upon forest regula- 

 tion by volume alone is found in the "combined method," 

 by which the areas receive more consideration, and due 

 importance is given to the arrangement of the age classes. 



First of all, a suitable distribution of the areas into the 

 several Periods is effected, then the volume returns are cal- 

 culated (at least, for the first one or two Periods), and, so 

 far as appears necessary for the equalisation of the returns, 

 shiftings of single areas are made. 



The estimate for determining the amount of the yield 

 which may safely be taken is sometimes confined to the next 

 ten years of the rotation. This practice, which originated 

 in Saxony, is gaining favour. A selection is made of the 

 woods which it is necessary to take in the course of the 

 coming decade, and the fellings are distributed as evenly 

 as practicable, so that the supply is made nearly constant. 

 The woods most urgently requiring removal are those whose 

 increment has sunk or is sinking below that which is profit- 

 able ; but in the removal of such woods, due regard must, 

 of course, be given to the sequence of the age classes. 



