136 



FOREST REGULATION 



d. Growth on this sixty-acre sample of normal forest during: 

 one rotation of sixty years is Go X 5600 = 336000 cubic feet, or 

 twice the amount of Growing Stock found on the sixty acres at any 

 one time. In other words, the Growing Stock is replaced every 

 thirty years, or in general in r/2 years. 



e. Growing Stock is reduced each winter by the yearly cut, of 

 5600 cubic feet, and is replenished the following summer l)y the 

 season's growth. 



Uol. /acrt 



bO dtfves < T acres 



Figure 7. Diagram of a 6o-acre Sample of a perfectly regular or Nor- 

 mal Forest. In this forest of 60 acres : r is the Rotation or 60 years, Yr is 

 the ripe timber 60 years old on one acre, (5600 cu. ft. in our example) G is 

 the Growing stock on 60 acres, varying in age from i to 60 years. This G 

 does not change, i. e., it is the same every year. Each strip represents the 

 volume of timber or wood of one acre ; and the volume is here assumed to 

 vary directly as the age. The cut of ripe tim'ber in each year is Yr equal to 

 the growth on 60 acres. The cut in 60 years is 60 X Yr (The parallelogram 

 in ."igure ) or twice the growing stock found at any one time. Thinnings are 

 neglected in this consideration. 



