228 A NATIONAL PLAN FOR AMERICAN FORESTRY 



Without drastic reduction of drain and the most careful husbanding 

 of sapling, cordwood, and young saw-timber stands, there does not 

 seem to be any prospect of an enlarged volume of available saw timber 

 in the New England and Middle Atlantic regions. At present rapid 

 depletion of cordwood stands is preventing the building up of growing 

 stock of saw- timber size in these two regions. Even with drain at 

 only half the 1925-29 rate the area in the restocking and deforested 

 classes seems likely to increase to nearly half the total forest area of 

 these regions by 1950. 



Finally, these calculations afford no evidence that the volume of 

 young growth annually approaching maturity in the South after 1950 

 will be any greater than the amount maturing annually prior to that 

 time. The figures indicate that the forest situation in this great 

 region may remain without material change for some decades unless 

 forestry measures are aggressively adopted throughout the region. 



SUSTAINED YIELD POSSIBILITIES 



An underlying purpose in the management of forests is to provide 

 a stable and ample supply of usable timber of the character and 

 quality needed to meet the requirements of the users of wood and 

 wood products. This may apply to a single forest property, to the 

 forests of a region as a whole, or to an entire country. Forests so 

 organized and managed are referred to as being on a sustained-yield 

 basis, and the volume of material present, as the basis for manage- 

 ment is known as the growing stock. Under such management the 

 age classes will be more or less evenly distributed. 



Where there is a large surplus of mature and overmature timber, 

 as in the Pacific Coast region, the rate of cutting can exceed the growth 

 until the surplus is used up without violating the principle of sustained 

 yield. The cutting of this surplus should, of course, be extended over 

 a sufficient number of years to permit the existing young stands to 

 mature and the cut-over land to restock in a sequence which will 

 permit cutting to continue without interruption. Where there is a 

 serious deficiency in mature timber and timber approaching maturity, 

 as in the East, continued cutting of saw timber in excess of the annual 

 growth must sooner or later exhaust the supply of saw timber that is 

 large enough for economic utilization. 



Except for special situations like that on the Pacific coast, a fairly- 

 even distribution of age classes is necessary before a volume approxi- 

 mately equal to the annual growth can be permanently cut each year. 

 It is evident, therefore, that there is a close relationship between the 

 volume of growing stock and the volume of usable material that can 

 be cut annually. If we may assume that a forest should be handled 

 on an 80-year rotation for the production of saw timber we may think 

 of such a forest under sustained-yield management as being' in the 

 form of eight 10-year groups or age classes, the oldest group affording 

 the usable material for the first 10 years. The next group would reach 

 the age for cutting during the second 10-year period and so on, until 

 at the end of the 80-year rotation the area first cut over would again 

 be ready for cutting. Such a forest contains the minimum growing 

 stock that can supply a continuous cut equivalent to the annual 

 growth on the whole area without, as a rule, necessitating the cutting 

 of timber below the rotation age. 



