100 



TIMBER TRENDS IN THE UNITED STATES 



Mortality Equivalent to More 

 Than One-third Net Growth 



Mortality from all causes in recent years has 

 amounted to about 5.6 billion cubic feet of grow- 

 ing stock annually, including 3.6 billion cubic 

 feet of softwoods and 2.0 billion cubic feet of 

 hardwoods (table 68). Sawtimber mortality 

 totaled 19.7 billion board feet in 1962, including 

 15.0 billion board feet of softwoods and 4.7 billion 

 board feet of hardwoods. These figures re- 

 present "trend level" estimates based upon 

 measurement of year-to-year endemic losses plus 

 allowances for sporadic major losses by fii-e, 

 blowdown, or other events of unusual severity. 



Mortality of gi-owing stock in 1962 thus was 

 equivalent to about one-third of the net gi'owth 

 of gi'owing stock, and to roughly 36 percent of the 

 net gi'owth of sawtimber (fig. 44). 



In addition to the trees 5.0 inches and larger 

 that are included in estimates of mortality, de- 

 structive agents cause a large annual gi'owth loss 

 of other sorts. Retarded gi^owth rates of live 

 trees resulting from attacks by insects, disease, 

 or dwarfmistletoe, loss of trees under 5.0 inches, 

 and delays in restocking of areas burned, all add 

 to the growth loss from destructive agents. 

 Defects caused by borers in southern hardwoods, 



for example, also reduce the grade and value of 

 standing timber. Such additional impacts on 

 gi'owth were not estimated in this study but may 

 well equal or exceed the estimated volume of 

 mortality. 



Softwood Mortality Mainly in 

 West/ Hardwood in East 



About 9 billion board feet of softwood sawtimber 

 has been killed annually in the Pacific coast section 

 in recent years, and 4 billion board feet in the 

 Rocky Mountains (table 68). These losses repre- 

 sented about 85 percent of the total softwood 

 mortahty in the United States. In Washington 

 and Oregon alone, the volume of timber dying 

 from natural causes has amounted to approxi- 

 mately 7 billion board feet annually in recent 

 years. Much of this loss, moreover, has been in 

 overmature trees containing relatively large pro- 

 portions of high-gi^ade material. 



Hardwoods accounted for about one-fourth of 

 the sawtimber mortality in 1962. Because hard- 

 wood losses are for the most part widely dispersed 

 and because dead hardwood timber deteriorates 

 rapidly, very little of this dead timber has been 

 classed as salvable. 



NET GROWTH AND MORTALITY, 1962 



Softwoods 



Hardwoods 



iiS: Net Growth 

 ^P Salvaged Mortality 

 Unsalvaged Mortality 



I i 



1 



6 8 



10 



billion cubic feet 





Fisure 44 



