A NATIONAL PLAN FOR. AMERICAN FORESTRY 



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It will be instructive to consider some of the growing-stock aspects 

 of the forests in the several regions in relation to sustained saw-timber 

 yield. The results of theoretical calculations of the yields which 

 might be maintained on three assumptions of regulated growing stock 

 are presented in table 21. The first column is based on a growing 

 stock in which the saw-timber volume equals the volume of present 

 saw- timber stands ; the second column upon a growing stock in which 

 the saw- timber volume equals that portion of present saw- timber 

 stands estimated to have a positive utilization value under 1925-29 

 conditions (see preceding subsection, " Availability of Timber 

 Stands"); the third upon a growing stock in which the saw- timber 

 volume equals the estimated saw- timber volumes in 1950 on the 

 basis set up in table 20. 



TABLE 21. Estimated saw-timber yields theoretically possible on forests with regular 

 distribution of age classes based on assumed saw-timber volumes 



These calculations are premised on an even distribution of age 

 classes, no cutting except for salvage, thinnings and other improve- 

 ment cuttings, until the saw timber reaches rotation age; and meas- 

 ures adequate to restock cut-over lands and to protect the growing 

 stock. Rotations also are necessarily assumed 60 years for soft- 

 woods in the South, 80 years for hardwoods in the South and for all 

 other species in the other eastern regions, 100 years in the Pacific 

 Coast region, and 120 years in the Rocky Mountain regions. For 

 convenient reference table 21 also gives the 1925-29 average saw- 

 timber drain. 



These calculations indicate (column 1, table 21) in New England 

 and the Middle Atlantic regions that regulated growing stock with 

 saw-timber volumes equal to present volumes would just about sup- 

 port through sustained yield, a drain of saw timber equal to the 

 1925-29 rate. This indicated sustained yield exceeds the present 

 annual growth because it assumes no cutting of stands below rotation 

 age other than in cultural operations, whereas under current prac- 

 tices there is a heavy drain in both cordwood and small saw-timber 



