48 



MISC. PUBLICATION 11, U. S. DEPT. OF AGRICULTURE 



further complicated by lack cf knowledge of the effect of the two cuttings 

 on the stand. 



In order to get some idea of what the yield from cut-over land might be in 

 50 years, 500 increment borings were taken on a mixed stand cut about 45 

 years ago. The results of this study were then applied to the reserve stand 

 left on this working circle. 



Table 2 shows the increase in diameter by 2-inch diameter classes for a 

 50-year period. 



Application of these results to the stand and stock tables for the Government 

 land cut over to date gives the following : 



Volume per acre in l)oard feet 



Cutting cycle 



Average 



origiBal 



stand 



Amount Amount 

 cut (84.7 left (15.3 

 per cent) per cent) 



Increment 



on 12-inch 



d. b. h. 



trees left 



Volume of 

 pole stuff 

 merchant- 

 able 



Average 



stand at 



second cut 



50 years 



30,700 



26,000 ; 4,700 



10,000 



2,800 



17,509 







i 









Under the provisions of this plan it is proposed to leave 20 per cent of the 

 stand and remove 80 per cent. Under these conditions the resultant stand at 

 the end of 50 years would be as follows : 



Volume per acre in 'board-feet at the end of 50 years 



Cutting cycle 



50 years. 



Average Amount 



original cut (80 



stand per cent) 



30,700 



24,600 



Amount 



left (20 



per cent) 



100 



Increment 



on 12-inch 



d. b. h. 



trees left 



Volume of 

 pole stuff 

 merchant- 

 able 



1 Average 

 \ stand at 

 i second cut 



12,000 



t 

 2,800 I 



20,900 



The above computations indicate that with a reserve stand of 6,100 per acre 

 a stand of 20,000 or over would be produced in 50 years. This is not con- 

 sidered too much to expect, inasmuch as 90 per cent of the trees left are under 

 30 inches d. b. h., and with release from competition and suppression should 

 take on increment rapidly. A cut of 16,000 per acre is therefore considered 

 conservative for the second cutting cycle. 



DISCUSSION OF ROTATION AND CUTTING CYCLES 



Available growth data indicate that on a 100-year rotation a tree of at least 

 18 inches d. b. h. can be produced. The reproduction under 4 inches d. b. h. now 

 on the ground should, in a 100-year period, be from 24 to 30 inches d. b. h. 

 Figuring that logging during the second cutting cycle will destroy about one- 

 half of the reproduction, there should be at the end of the first rotation a stand 

 one-half stocked with trees from 18 to 30 inches d. b. h., with a small percentage 

 of larger trees left for seeding purposes when the second cut is made. It 

 would therefore seem safe to assume a rotation period of 100 years to start 

 with. 



In determining the length of cutting cycles to be adopted the following condi- 

 tions were considered : 



1. A rapid cutting over of the area, removing from 60 to 65 per cent of the 

 volume. First cutting cycle, 35 to 40 years. Second, 60 to 65 years. 



2. A slower cutting over of the area, removing from 80 to 85 per cent of the 

 volume. Cutting cycles, 50 years each. 



Advantages of rapid cutting. — Removes decadent and part of mature timber 

 in from 35 to 40 years. Leaves heavier second cut more nearly approaching a 

 sustained-yield basis. 



Disadvantages of rapid cutting. — (a) From 15 to 20 per cent of timber left 

 would be of mature and thrifty-mature classes. (6) Marking would be com- 

 plicated, (c) A lighter cut per acre reduces the chance for a profitable opera- 

 tion at present.. 



