THE ROTS OF WESTERN WHITE PHiTE. 



11 



Table I shows that for each type of site the rot percentage gradu- 

 ally increases from the youngest to the oldest age class, reaching 18 

 per cent in the bottom sites and 14.7 per cent on the slope sites. 

 Comparing similar age classes of the two types of sites, the figures 

 for rot percentage on the bottom sites run consistently higher than 

 those of the slope sites. 



Table III. — Comparison of bottom and slope sites of different sale areas of 

 western white pine, shoimng the relation of rots to site, independent of age 

 classes. 





Bottom sites. 



Sale area. 



Slope sites. 



Sale area. 



Plat 



No. 



Num- 

 ber of 

 trees 

 (basis). 



Average 



age 

 (years). 



Rot 



(per 

 cent). 



Plat 

 No. 



Num- 

 ber of 

 trees 

 (basis). 



Average 



age 

 (years). 



Rot 



(per 

 cent). 





2 

 1 

 3 

 1 



15 

 18 



70 



347 

 120 



379.1 



146.4 



72.0 



111.0 

 159.6 



20.53 

 8.01 



.002 



5.23 

 9.32 



Bennett-Miner 



1 



1 



2 



la 



4 



71 

 100 

 149 

 16 

 33 

 241 



340.6 

 142.2 

 79.0 

 122.0 

 118.0 

 120.7 



14.62 





2.98 





/Silver Creek 



.63 













Do.. . . 



do 



.70 





Tent Creek 



2.19 







Total 







Total 





570 









712 























In comparing the average volume of rot for the two types of site 

 in Table I a striking contrast is found between the butt-rot volumes. 

 The average butt-rot volume on the bottom sites is found to greatly 

 exceed the average volume for the slope sites, the average volume of 

 trunk-rot is approximately equal, while the average volume of com- 

 bined rots is shown to be somewhat larger on the bottom sites. 



INFECTION AGE. 



The average infection age, as defined in a previous work,^ repre- 

 sents the average age of the youngest trees in the stand open to first 

 infection by fungous enemies. It is the average age at which the 

 stand is most liable to first infection and below which infection 

 rarely occurs. Subsequent to this age infection is to be guarded 

 against, as the chances of infection, up to a certain point, will con- 

 tinue to increase with the increase in age, number of injuries, etc. 



In this bulletin the term age of earliest infection is used in place 

 of "average infection age." It is believed the newer term will more 

 accurately convey the meaning intended. 



On the bottom sites, Table IV, the age of the earliest infection for 

 the combined trunk and butt rots can be placed approximately in 

 the 61 to 70 age class, since the first tree with visible decay is found 

 in the 71 to 80 age class and is 73 years old. It must be remembered 

 that actual infection is expected to take place some time before visible 



1 Weir, J. R., and Hubert, B. E. A study of beart-rot in western hemlock. U. S. 

 Dept. Agr. Bui. 722, 39 p., illus. 1918. 



