NORMAL FOREST 135 



1. Let a given forest have an area of 12,000 acres, all of the 

 same quality of land, site II, and be stocked with Pine, managed on 

 a rotation of sixty years. Being perfectly regular in age classes, 

 there are on this forest in the fall of the year and before the yearly 

 cut is made, 200 acres of sixty-year old timber, 200 acres of fifty- 

 nine-year old, etc., down to 200 acres of plantations one season old. 



2. If we take one acre sample of each of these stands we get a 

 miniature model forest of sixty acres with one acre sixty years old, 

 one acre 59 years old, etc. 



This small model or sample forest can be regarded as a separate 

 normal forest and what is true of this sample applies also to the 

 12,000 acre forest. 



This sixty acre model or sample is represented by a diagram in 

 Fig. 7 ; each strip represents the volume of wood on one acre of 

 land. The strip at the right represents one acre of sixty years old 

 timber now ready to cut or the Yield of one acre, i. e., Yr., say 

 5600 cubic ft. 



3. If the silvicultural plan is to cut clear and plant at the age 

 of sixty and thin each stand every six years, then the work on this 

 Normal forest of sixty acres is as follows : Each year there is : . 



One acre cut clear. 



One acre of six-year old, one acre twelve years old, etc., in all 

 nine acres are thinned. 

 One acre is planted. 

 Sixty acres are cared for and have taxes paid on them. 



4. Leaving out of consideration growth and cut of stuff re- 

 moved in thinnings, the following is true : 



a. Cut each year is 5600 cubic ft., i. e., the stuff on one acre of 

 ripe, or sixty-year old timber. 



b. Growth on the sixty acres is 5600 cubic ft. per year or the 

 amount cut each year. The growth being sixty acres, and the cut 

 on one acre we do not cut the growth of the year, but an amount 

 equal to the growth. 



c. Growing Stock on sixty acres is indicated by the triangle 

 at least closely enough for our purpose here. This triangle has an 

 area : 



60 X 5600/2 = Yr X r/2. 



Growing Stock 168,000 cubic feet. 



