DRY-ROT OF INCENSE CEDAR. 



43 



Not only does the total number of wounds increase with age in a 

 stand, but the number of severe wounds becomes proportionately 

 greater. Each tree was given a wound rating (x) , x, xx, or xxx, the 

 first symbol indicating very slight wounding and the last very 

 severe. In Table IX trees with a rating of xx or xxx are con- 

 sidered as severely wounded. In all cases the character as well 

 as the extent of the wounding and its relation to inoculation by 

 spores of the dry-rot fungus was carefully taken into account in 

 applying the rating. 



In column 4 of Table IX it is seen that while in the age class of 

 41 to 80 years only 6.7 per cent of the wounded trees are severely 

 wounded, an almost steady increase brings this figure to 68.5 per 

 cent in the class of 321 to 360 years. This is to be expected, espe- 

 cially since fire scars predominate, because large scars of this type 

 are almost invariably the result of recurring fires, and in the past 

 virgin stands in California have been fire swept time and again. 

 The two oldest age classes can not be given much weight, owing to 

 an insignificant basis. \. 



The above figures demonstrate the rather slight chance an incense 

 cedar has of rounding out its life without a reduction in its normal 

 increment through an injury interfering with the growth processes 

 or a reduction in its actual content of merchantable timber, either 

 directly from a wound or by a wound affording an entrance for a 

 heartwood-destroying fungus, in this instance most probably the 

 dry-rot fungus (Polyporus amarus) . 



RELATION OF DRY-ROT TO MECHANICAL INJURIES. 



The intimate connection of various kinds of wounding, especially 

 fire, with infection by the dry-rot are shown in Table X. The 

 infections are grouped under their respective causes and percentages 

 for each cause, figured on the basis of the total number of infections. 

 Trees of uncertain ages are included in these figures, since it makes 

 no difference in this table whether or not the absolute age of the 

 tree is known. 



Table X. — Mode of entrance of dry-rot infections of incense-cedar trees. 





Number 

 of infec- 

 tions 

 (basis). 



Means of entrance of infections (per cent). 



Locality. 



Fire 



scars. 



Knots. 



Wounds, 

 cause 

 un- 

 known. 



Light- 

 ning 

 scars. 



Un- 

 known 

 causes. 



Frost 

 cracks. 



Broken 



or dead 



tops. 



Intermediate area 



322 

 334 



75. S 

 58.7 



19.3 

 31.1 



0.6 

 5.1 



2.5 

 1.5 



0.9 

 2.4 



0.6 

 .9 



0.3 



Optimum area 



.3 







Combined. . . '. 



656 



67.1 



25.3 



2.9 



2.0 



1.7 



.8 



.3 







