90 



TIMBER RESOURCES FOR AMERICAS FUTURE 



demand and supply and thus alter the timber 

 outlook. 



Needed and projected growth and inventory 

 are estimated only for the lower and medium 

 levels of timber demand. None are developed for 

 the upper-level demand projections for timber 

 products because: (1) The projections of growth 

 and inventory related to medium demand for 

 timber products show such wide disparity between 

 needs and expectations (under the assumptions 

 made) that the even greater disparities that would 

 be shown by relating growth and inventory to 

 upper demands for timber products would be of 

 little more than academic interest; and (2) the 

 intensity of forestry that will be needed to sustain 

 even medium demands for timber products is so 

 much greater than what may be expected from 

 a continuation of recent trends in forestry that 

 the even greater intensification necessary to 

 sustain upper timber demands by 2000 probably 

 would not be practical of attainment in such a 

 short period of time. 



Growth Capacity 



Growth capacity of the Nation's commercial 

 forest lands is not known and means different 

 things to different people. Growth capacity 

 may be viewed as a series of levels somewhat like 

 the rungs of a ladder on the scale of growth 

 possibilities. One such rung or benchmark might 

 be an annual growth of 50 billion cubic feet 

 including 200 billion board-feet of sawtimber, 

 which is the growth that could be obtained if 

 there were proper distribution of age classes and 

 if each acre of forest land in each type and site 

 class were producing as much as the most pro- 

 ductive timber stands are today for the respective 

 types and sites. Growth capacity ultimately 

 might be even higher depending upon results of 

 forest genetics research and the use of growth- 

 increasing substances still in experimental stages. 



A more practical and conservative concept of 

 growth capacity is the growth that ultimatel}^ 

 would be attained if the commercial forest land 

 in each region were placed under the better forest 

 management currently in effect in that region. 

 This is termed "realizable growth" and is esti- 

 mated at about 100 billion board-feet of sawtimber, 

 70 percent of which would be softwoods. This 

 estimate was developed locally, region by region, 

 utilizing the best available technical information 

 and judgment of experts familiar with local 

 conditions. 



Realizable growth of sawtimber is more than 

 twice the 1952 net growth of 47.4 billion board- 

 feet. In terms of growing stock, the realizable 

 growth of 27.5 million cubic feet is also about 

 twice the 1952 level. Thus, the realizable growth 

 occupies a point on the scale of growth capacity 

 about double the 1952 levels, but well below 



growth capacities that might be estimated on 

 the basis of more theoretical concepts. Realizable 

 growth is summarized in table 56 by growing 

 stock and sawtimber and by species groups. 



Timber Removal 



Earlier in this summary section the projected 

 demands for timber were converted to timber 

 cut.^^ The conversion of demand to timber cut 

 is also explained in more detail in the section on 

 Future Demand for Timber. Before estimates 

 can be made of needed and projected growth, 

 one additional step must be taken, i. e., the 

 addition of a "margin" to the timber cut that 

 is needed to meet projected demand. The result 

 is called "timber removal." The only difference 

 between timber cut and timber removal is that 

 the latter includes not only timber cut but also 

 an additional allowance for removals from the 

 inventory commonly referred to as a "margin." 



Following are the steps taken to develop 

 estimates of needed growth and inventory in 

 proper order: (1) Projected demand for timber 

 products; (2) the timber cut necessary to supply 

 projected demand; (3) the timber removal 

 necessary to supply timber cut; (4) the growth 

 necessary to supply the timber removal; (5) the 

 standing timber inventory necessary to produce 

 the needed growth. The transition from step 1 

 to 2 is summarized in table 10 (p. 22). The 

 second, third, and fourth steps are shown in 

 table 55. 



A Margin Is Included 



The inclusion in timber removal of an allowance 

 or margin in addition to timber cut has proved 

 controversial in the past. One reason for this is 

 that neither the reasons for the margin nor the 

 percentage allowances have been clearly under- 

 stood . The correct concept of the margin is that it 

 accounts for withdrawals from the timber inven- 

 tory which are not included in the timber cut. 

 The margin covers three items: 



(1) Inventory withdrawals due to natural 

 catastrophes from insects, disease, storm, or fire in 

 excess of the allowance made for mortality due to 

 these causes in estimating net growth. Thej'^ 

 include events of such extreme severity as to be 

 unpredictable as to time or place of occurrence. 

 For that reason, including regional estimates for 

 catastrophes in the calculations of net growth was 

 not practicable. 



(2) Unforeseen new uses for wood. Although 

 foreseeable new uses for wood have been accounted 

 for in projected demand for timber products, the 

 rapidit}^ of new developments in wood utilization 

 dm-ing recent years and the renewable character 



" See discussion under Projected Demand Converted 

 to Timber Cut, p. 21, and table 10. 



iii 



