in no way by the cutting practice 

 employed on other areas. By 

 1 966, it is estimated, the net growth 

 of stands assumed to be converted 

 to immature status subsequent to 

 1936 will be about 215 million 

 board feet annually if past cutting 

 practice continues. Cutting on a 

 light selection basis, however, 

 would raise the net growth of such 

 stands in 1966 to 520 million board 

 feet, or more than 2.4 times that 

 which would be obtained by con- 

 tinuation of past practice (fig. 24.) 

 Over a rotation, the spread be- 

 tween the volume growth following 

 lit^ht and that following heavy 

 cutting would be smaller than for 

 the initial 30-year period, but the 

 difference in quality of growth 

 would still be great. If the antici- 

 pated demand for privately owned 

 timber is completely met, a critical 

 period will arrive in the heavily 

 producing units within one to two 



2,500 



500 



400 



300 



200 



100 



1936 

 Figure 24. 



1946 



-Annual growth of stands that would b, 



subsequent to 1936, by cutting practice. 



I956 I966 



converted to net growth status 



■§ 2,000 



v. 







1,500 



,000 



500 



"1 



1936-45 1946-55 



Periodic annual growth ,95"75 percent cutting 

 Periodic onnual growth, 75~50 percent cutting 

 Periodic annuol growth, 50~50 percent cutting 



1956-65 

 Periodic annual depletion 

 Potential annuol growth, pine sites 

 Potential annual growth, other sites 



Figure 23. — Regional periodic annual growth under three degrees of cutting, periodic 

 annual depletion, and potential annual growth. 



decades. The quality and quan- 

 tity of growth available in the 

 reserve stands will then decide 

 how drastic the curtailment must 

 be. Both amount and value of 

 growth as of this period can be 

 greatly increased, and conse- 

 quently the necessary curtailment 

 considerably reduced, by shifting 

 cutting practice to a light selec- 

 tion basis now. 



Potential Annual Growth 



Potential annual growth, as 

 already defined, is the average 

 annual increment obtainable 

 through reasonably intensive for- 

 estry as judged by current local 

 standards. It does not represent 

 maximum increment; the theo- 

 retical ultimate value has been 

 substantially reduced to allow for 

 an amount of understocking and 

 nonuse of forest land believed 



47 



