SUSTAINED ANNUAL YIELD 835 



First felling (1021) — 



Ys of 40,000 13,333 feet 



Second felling (1941) — 



^ 26,667 plus growth 



Yl (26,6C7 plus 5,000) (31,667) 10,556 feet 



Third felling (1961) — 



Y, 24,445 plus 5.000 9,815 feet 



Fourth felling (1981) 



Yii 22,983 plus 5,000 .9,328 feet 



Here the volume cut is gradually decreased to correspond with the 

 amount of the annual growth; and by doing so the amount of growing 

 stock is gradually reduced to normal. 



In this case (overstocking), the G^ for the land is 15,000 feet. 



Vr R 



(Ga= ~) / or Ga replaces in — - years. The stand was, thus, over- 

 stocked by 10,000 feet. 



In the first case (understocking) the G^ is 12,000 feet. Here the 

 stand was understocked by 2,000 feet. 



Of course, any rotation may be assumed and used; and by use of 

 different rotations different relative degrees of stocking may be ob- 

 tained. The amount of growth, however, is set by the forest and the 

 quality of site ; and since by this method the amount cut depends upon 

 the amount that grows, no serious overcutting or undercutting can 

 take place. 



The amount- one-third is, to be sure, a figure that is not entirely 

 adapted to all regions. In fact the flat rate of one-third the basal area 

 may be modified by special permission in some cases where the quality 

 of the site and the characteristics of the species grown produce extraor- 

 dinary conditions of growth. Such may be, as examples, the alpine 

 forests, or the very rapidly growing stands on the overflow lands of the 

 lower Mississippi River bottoms. 



In any case, there is offered by the plan, the opportunity of handling 

 the forest on a proper working plan with entire freedom of method of 

 cutting. It is simple of understanding and of application ; it is easily 

 checked in the field ; and it maintains a forest of growing timber. 



