TIMBER SUPPLY OUTLOOK 



485 



future demands into two broad size or quality 

 classes. On this basis 84 percent of the timber 

 cut from gi'owing stock in 1952 consisted of saw- 

 timber (table 289). Although a slight decline in 

 this proportion is anticipated by 2000, more than 

 80 percent of projected demands will require trees 

 of sawtimber size. 



Table 289. — Proportion of timber cut represented 

 by sawtimber in 1952, 1975, and 2000 ' 



Year and demand 

 level 



Total 



timber 



cut 



Sawtim- 

 ber cut 



Sawtimber 

 cut in re- 

 lation to 

 total cut 



1952 ^ . 



Billion 

 cu. ft. 

 10. 76 



13.99 

 12. 43 



19.71 

 15. 66 



Billion 

 cu. ft. 

 9.07 



IL 64 

 10. 33 



16. 16 

 12. 83 



Percent 



84 



1975: 



Medium level 



83 



Lower level 



83 



2000: 



Medium level 



82 



Lower leveL 



82 







' Summarized from table 81, of Basic Statistics in ap- 

 pendix. 



Trees under sawtimber size included in growing 

 stock do not lend themselves to the manufacture 

 of lumber, veneer, and many other products. 

 This is because tliey are frequently knotty or have 

 other undesirable quality characteristics, and the 

 yield of usable material is low per unit of volume 

 handled. Cost of logging and manufacture of such 

 trees is also higher per unit of volume output than 

 for larger trees. The same limitations apply in 

 part to the smaller trees included under the 

 definitions of sawtimber used in this report. 



Within these limitations, the needed growth of 

 sawtimber is the best available expression that 

 combines consideration of both the quality and 

 volume required to sustain estimated demands 

 for the majority of products. On the other hand, 

 needed growth of growing stock takes no account 

 of size distinctions, and attainment of it could 

 leave unsatisfied demands for many important 

 products. 



GROWTH AND INVENTORY EX- 

 PECTED IF PROJECTED DEMANDS 

 ARE MET AND FORESTRY TRENDS 

 CONTINUE 



Estimates of the growth and inventory needed 

 to sustain lower and medium level demands have 

 already been discussed. Comparisons of realiz- 

 able growth with needed growtf\ have shown that 

 both medium and lower level demands are within 



reach. To complete the timber outlook picture, 

 comparisons are now made between the supplies of 

 timber needed (needed growth ' and inventory) 

 and the supplies that would be available in future 

 years under certain assumptions (projected growth 

 and inventory). 



The growth and inventory of tiie future will 

 result from the interplay of the following four 

 factors: (a) the 1953 inventory, (b) additions to 

 this inventory by growth (including ingrowth), 

 (c) subtractions from the inventory by timber re- 

 moval, and (d) subtractions due to losses caused 

 by destructive agents, grouped under the term 

 "mortality," and not included in timber removal. 

 These four factors are known quantities for the 

 base year 1953. However, projected growth and 

 inventoiy can be developed only by estimating 

 future values for growth rates, timber removal, 

 and mortality rates on the basis of broad trends 

 assumed to prevail during the period 1953-2000. 



The trends assumed for estimates of projected 

 growth under each demand level are (1) that an- 

 nual timber removal will climb steadily from 1952 

 to meet the removal necessary to supply demands 

 each year until 2000 (table 283), and (2) progress 

 in forestry will continue as indicated by recent 

 trends so that by 2000 it will be considerably more 

 widespread and intensive than in 1952. 



Under these assumptions, projected net growth 

 (including ingrowth), mortality, and inventory 

 were calculated by projection periods for each of 

 the 13 regions recognized in this report. The 

 initial years of the projection periods used were 

 1953, 1965, 1975, and 1985. Regional calculations 

 of projected net growth plus mortality for the 

 initial year of each projection period wore sum- 

 marized for the three species groups, and for all 

 species combined, and expressed as percentages of 

 the corresponding projected inventories. 



Under lower level demands, the gross growth 

 rates thus derived for all species combined changed 

 from 3.0 percent in 1953 to 3.7 percent in 1985, an 

 increase in growth rate of 23 percent (table 290). 

 Growth rates under the medium level projection 

 were slightly higher because the larger volume of 

 timber removed under this projection would result 

 in inventories of generally younger trees with 

 higher growth rates than would timber removal at 

 the lower level. 



Increasing growth rates were adopted for west- 

 ern species because of expectations that (1) im- 

 proved forest practices will become more intensive 

 and widespread tJian at present and (2) rapidly 

 growing young stands now under sawtimber size 

 will develop into sawtimber in increasing amounts 

 during the projection period while continued 

 cutting of old growtli will reduce the area of very 

 slow growing timber. Thus, the growth rate for 

 western species in the initial year of the last pro- 

 jection period, 1985, is 53 percent higher than the 

 1953 rate at the lower level of demand (table 290). 



