GROWTH AND UTILIZATION 



149 



Table 90. — Net annual growth oj western species 

 in the United States and Coastal Alaska, by 

 species group, 1952 ^ 



Species group 



Softwoods : 



Douglas-fir 



Ponderosa and Jeffrey pine 



Western hemlock 



White and sugar pine 



Redwood 



Other softwoods 



All softwoods 



Hardwoods 



All species 



Growing 

 stock 



Million 



cu. ft. 



902 



3479 



237 



100 



77 



833 



2, 628 

 149 



2,777 



Live saw- 

 timber 



Million 



bd.-ft. 



4,431 



* 1, 841 



1,038 



535 



396 



2,800 



11,041 

 265 



11,306 



' Net annual growth by species groups and regions is 

 shown in table 103 in this section (p. 167), and int he Basic 

 Statistics, tables 34 and 36 of the appendix. 



2 Reference to the more important species in other soft- 

 woods is found on p. 160. 



3 Excludes 4 million cubic feet of ponderosa pine in the 

 Plains Region. The total net annual growth of ponderosa 

 and Jeffrey pine in the United States is 483 million cubic 

 feet. 



^ Excludes 16 million board-feet of net growth of pon- 

 derosa pine in the Plains Region. The total net annual 

 growth of ponderosa and Jeffrey pine in the United States 

 is 1,857 million board-feet. 



Annual Growth Is Increasing 



The first published estimate of annual timber 

 growth in the United States appeared in 1920. 

 Revised estimates were made for subsequent re- 

 ports on the national timber situation as of 1930, 

 1936, and 1944: 



Annual growth 

 Billimi Billimi 



Date: Report:' bd.-ft. cu.fi. 



1920 Capper 9.7 6.0 



1930 Copeland 11.7 8.9 



1938 Joint Congressional Com- 32.0 11.3 



mittee. 



1944 Reappraisal 35.3 13.4 



1952 Timber Resource Review 47.3 14.2 



' For references see section on Forest Land and Timber' 

 page 113. 



For various reasons, these periodic estimates of 

 1 timber growth are not comparable. Changing 

 utilization standards, differing definitions as to 

 what constitutes forest land, and improvement in 

 timber inventory procedures, which have affected 

 periodic estimates of timber volume,^' have like- 

 wise afi^ected estimates of timber growth. In 

 addition, there were changes in standards and 

 techniques applying strictly to growth that were 

 1 reflected in estimates made at different times. In 



" See discussion 

 Timber, p. 113. 



in the section on Forest Land and 



some cases, the change has been toward an ap- 

 parent increase and, in others, toward an apparent 

 decrease in timber growth. 



Factors tending to exaggerate the increase of 

 annual growth that was probably taking place in- 

 clude the decrease in the lower limit of sawtimber 

 size in one region after another; the increase in 

 allowable percentage of defect; and the inclusion of 

 species formerly omitted and scattered stands of 

 sawtimber and much pole timber formerly over- 

 looked. In addition to these factors, the crude 

 estimate in the Capper Report of 1920 included 

 only the growth on existing stands and took no 

 account of the "ingrowth" of timber added to 

 growing stock during the year of estimate. Work- 

 ing in the opposite direction is the change in the 

 present report to net growth after allowing for all 

 mortality from fire, insects, disease, and other 

 causes. 



Data Adjusted for Comparability 



Progress of the Forest Survey in recent years, 

 including resurvey of much of the area previously 

 surveyed and improved techniques of timber in- 

 ventory and growth calculation, provided a rea- 

 sonably good basis for adjusting or reconstructing 

 the 1944 estimates to bring them into accord with 

 1952 standards. The method of adjustment varied 

 depending upon the Forest Survey and other data 

 available. Generally the adjustments involved (1) 

 deriving 1944 growth rates either through adapting 

 the 1952 rates corrected for changes in mortality 

 1944 over 1952 or by interpolation of growth rates 

 between successive surveys bracketing 1944, and 

 (2) the application of the 1944 rates so derived to 

 adjusted 1944 timber volumes or conversion of 

 these rates to growth per acre and applying them 

 to the 1944 adjusted acreage by stand-size classes. 



Apparent Overall Changes Indicate Favor- 

 able Trends 



The comparison of adjusted figures for 1944 and 

 1952 provides reasonably strong evidence that 

 sawtimber and growing-stock growth has increased 

 (table 91). The indications are that overall saw- 

 timber growth has increased 9 percent and total 

 growing-stock growth 14 percent. Whether these 

 differences represent the actual amount of change 

 cannot be proved because of the possibility of bias 

 in deriving the adjusted 1944 figure and sampling 

 errors associated with the 1952 estimate. Never- 

 theless it seems unlikely that the error of estimate 

 from whatever cause would be great enough to 

 affect the validity of the indicated trends signifi- 

 cantly. 



Perhaps even more encouraging is the apparent 

 increase in the growth of eastern species — for 

 hardwoods a 20-percent gain in growing stock and 

 16-percent gain in sawtimber, and for softwoods a 

 16-percent gain in growing stock and an 1 1 -percent 



