152 



TIMBER RESOURCES FOR AMERICA'S FUTURE 



ISOFTWOODS HARDWOODS 



SAWTIMBER 



1 











4 



lillion board-fee 



6 



t 



8 10 



■ 







2 



1 



GROWING STOCK 



,,_ 







^^^^^■■i^^^^^^^l 









1.5 2.0 



^■H 







1.0 



ubic feet 



^^H 







0.5 



billion c 



includes Coastal Alaska 

 Figure 60. — Annual timber mortality, 1952. 



Eighty percent of the softwood sawtimber mor- 

 tality is in the West; 30 percent in the Douglas-fir 

 subregion alone. This distribution of mortality 

 is related to the concentration of softwood timber 

 volume in the West, particularly in the Douglas- 

 fir subregion, and to the high proportion of over- 

 mature timber in the West. Si.xty percent of the 

 hardwood sawtimber mortality is in the North. 

 This is a greater proportion than for timber volume 

 because the rates of 1952 mortality (mortality as 

 a percentage of timber volume) are higher in the 

 North than elsewhere: 





All species 



Softwood 



Hardwood 





(percent) 



(percent) 



(percent) 



North 



0. 78 



1.03 



0. 71 



South 



. 50 



. 53 



. 46 



West and Coastal Alaska 



. 61 



. 61 



. 58 



The high rate of hardwood mortaUty in the 

 North is believed to be related to widespread 

 incidence of birch dieback and oak wilt and early 

 susceptibility of aspen to stem canker. In soft- 

 wood mortalit}' rates, the difference between the 



North and the West and South is even more 

 marked — presumably because of the greater sus- 

 ceptibility of northern species to windstorm and 

 the early susceptibility of balsam fir to heart rot 

 and white pine to blister rust. 



Insects cause more mortality than either fire or 

 disease in the South and West (table 93). In 

 contrast to this, disease causes more mortalitj- 

 than either fire or insects in the North and in 

 Coastal Alaska. 



Table 93. — Annual mortality of growing stock and 

 live sawtimber, in the United States and Coastal 

 Alaska, by cause and by section, 1952 ' 



GROWING STOCK 













Total, 













United 



Cause 



North 



South 



West 



Coastal 

 Alaska 



States 



and 

 Coastal 

 Alaska 





Million 



Million 



Million 



Million 



Million 





CM. ft. 



cu. ft. 



cu. ft. 



cu. ft. 



cu. ft. 



Fire 



36 



126 



73 



1 



236 



Insects 



65 



112 



766 



27 



970 



Disease, _ 



461 



73 



190 



49 



773 



Other ^___ 



584 



318 



585 



23 



1,510 



Total _ - 



1, 146 



629 



1,614 



100 



3,489 







SAWTIMBER 









Million 



Million 



Million 



Million 



Million 





bd.-ft. 



bd.-ft. 



bd.-ft. 



bd.-ft. 



bd.-ft. 



Fire 



71 



294 



414 



2 



781 



Insects 



99 



412 



4,224 



98 



4,833 



Disease.. 



914 



233 



928 



204 



2,279 



Other ^.- 



995 



829 



2,717 



88 



4,629 



Total.^ 



2,079 



1,768 



8,283 



392 



12, 522 



' Estimates represent the current level of mortality indi- 

 cated by trends over a long period of time as determined in 

 1952. These estimates differ slightly from estimates of 

 actual mortality experienced in 1952 as reported in the 

 section on Forest Protection. The differences were entirely 

 in the Northern Rocky Mountain Region in the West, 

 where insect losses in 1952 were greater than the trend level 

 and losses due to disease and weather and animals were 

 slightly less. 



- Weather, animals, suppression, etc. 



Causes other than fire, insects, and disease ac- 

 count for 37 percent of all sawtimber mortality 

 and 43 percent of growing-stock mortality. The 

 proportions are higher in the East than in the 

 West. These losses include those from suppression 

 and senility as well as those from windstorm, ice, 

 animals, etc.^^ 



Reduction of mortalitj' from fire, insects, and 

 disease is implicit in the more comprehensive and 



" Causes of mortality and the full impact of these losses 

 on growth are more fully discussed in the section on Forest 

 Protection, p. 185. 



■i^ 



