DRY-ROT OF INCENSE CEDAR. 55 



intervals of 165 and 210 years, respectively, but simply that if it is 

 left to a greater age there is a full realization of the resulting enor- 

 mously increased loss through dry-rot. The pathological rotation 

 becomes a maximum limiting factor for the actual rotation, which 

 may be financial, silvicultural, or one of maximum volume, depending 

 on conditions in the future. From present indications it is highly 

 probable that all other rotations for incense cedar will fall below the 

 pathological rotation in both regions; the difference will be quite 

 marked in the optimum range. It is possible in the optimum range 

 that during the transition period, if necessary to leave suppressed 

 trees standing after cutting, the increased vigor of such individuals 

 which may follow the opening up of the stand might raise the critical 

 age somewhat, but in the present state of our knowledge not only 

 regarding the influence of thinning on the development of wood- 

 destroying fungi in standing trees, but in the case of incense cedar 

 regarding the actual response of the trees themselves, this consider- 

 ation is entirely too hypothetical to influence our present conclusions. 



SUMMARY. 



The results of this study point to the following main conclusions : 



(1) Incense cedar is classed as an inferior species because of a 

 uniformly heavy percentage of cull caused by the dry-rot fungus 

 (Polyporus amarus) . Judicious scaling and instruction in the proper 

 methods of bucking will ultimately aid materially in changing this 

 view. 



(2) Dry-rot can be eliminated in a large measure from future stands 

 by intensive fire protection, but it can not be entirely controlled in 

 this way, owing to the continued occurrence of unavoidable mechan- 

 ical injuries caused by pruning, lightning, and frost. 



(3) The following directions should apply to marking on timber 



(a) Trees with sporophores and shot-hole cups must be marked for cutting. 



(b) Seriously wounded trees, especially those with fire scars, should be marked to 

 be cut. 



(c) In the intermediate range all but a very small percentage of the trees are sup- 

 pressed. Since suppressed trees are subject to severe dry-rot after they pass the 

 critical age of 165 years, trees left standing should be of such an age that they will not 

 pass that age before the next cutting occurs. Dominant trees, being so few, may be 

 classed with suppressed trees, but in reserving seed trees only the most thrifty indi- 

 viduals should be considered. By this practice some dominants will be among the 

 trees left, and these will be safe until the age of 210 years is reached. 



(d) In the optimum range, suppressed trees are subject to damaging dry-rot after they 

 pass the age of 165 years (the critical age), while dominant trees are safe until 210 years 

 (the age of decline) is reached. Therefore, suppressed trees left standing must be of 

 such an age that they will not pass the critical age (165 years) before the next cutting 

 occurs, and dominant trees left should not pass the age of decline (210 years) before the 

 next cutting. Suppressed trees, however, should be heavily marked for cutting and 

 only left unmarked if unavoidable. 



