30 



BTT-LETIX 871, U. S. DEPARTMENT OF AGRICULTURE. 



It is not to be expected that the growth habits of the dry-rot 

 fungus would vary to any extent in regions so closely related 

 climatically as the intermediate and optimum ranges of incense cedar; 

 therefore, it is reasonable to believe that no matter what the classifi- 

 cation of the trees on the intermediate area may be in respect to 

 dominance and suppression when compared with the volume-growth 

 curve for that area, to find the true relation of the dry-rot fungus to 

 dominant and suppressed trees it will be necessary to determine the 

 classification of each tree by comparison with, the volume-growth curve 

 for the optimum area. 



This is brought out in Table II, in which the trees from all the areas 

 are combined, the dominance or suppression of all the trees being 

 determined by comparison with the volume-growth curve for the 

 optimum area. Only trees in which the progress of the decay or a 

 fire scar did not make it impossible to determine the age at stump 

 height are included in this table. This explains the slight dis- 

 crepancy between the total number of trees dissected and the total 

 number included in this and subsequent tables. 



Table II. — Cull caused by dry-rot found in incense cedars of the combined areas. 



Age class. 



Number of trees 

 (basis). 



Average age. 



Cull caused by dry-rot 

 (percentage of the 

 total volume). 



Dominant. Suppressed. Dominant. Suppressed. Dominant. ;Suppressed. 



Oto 40 years 



41 to 80 years... 

 81 to 120 years.. 

 121 to 160 years. 

 161 to 200 years. 

 201 to 240 years. 

 241 to 280 years. 

 2S1 to 320 years. 

 321 to 360 years. 

 361 to400vears. 

 401 to 440 years. 



Combined 



1 

 43 

 125 

 218 

 191 

 84 

 79 

 42 

 16 

 2 

 2 



803 



74 

 105 

 142 

 ISO 

 223 

 265 

 301 

 341 

 372 



166 



40 

 57 

 105 

 140 

 179 

 222 

 258 

 294 

 332 

 368 

 436 



173 





 1 



2 

 4 



12 

 26 



40 

 h0 

 66 

 68 

 5 



20 



In Table II the dry-rot percentage in the age class 161 to 200 

 years, for example, is figured on the total volume of all the dominant 

 trees both sound and decayed in that age class and not on the total 

 volume of both dominant and suppressed trees. This is the method 

 used throughout the table. 



It will be noticed that the number of trees (basis) in the suppressed 

 class far exceeds the dominant, this being a direct result of the 

 influence of regional suppression on the trees of the intermediate area. 



The columns of greatest interest are the last two, in which the 

 dry-rot percentages of the dominant and suppressed trees in the 

 different age classes are directly comparable. By dry-rot percentage 

 is meant the percentage of cull caused by the decay resulting from 



