FOREST PATHOLOGY IN FOREST REGULATION. 59 



are correct and that the next cutting may occur, for example, in 30 

 years, we may with comparatively small risk leave thrifty unwounded 

 trees of any age on the area; wounded but thrifty trees of more than 

 120 years are to be cut, wherever practicable, because in 30 years 

 they will be over 150 years old, at which age trees of this class are 

 more liable to deteriorate. Wounded trees which at the same time 

 are suppressed should be eliminated. It is bad silviculture to leave 

 individuals in the forest which not only do not produce the maximum 

 of timber but which in all probability will prove a total loss and which 

 occupy the place that should be fully stocked with trees promising 

 a full and sound crop. In case of an emergency, such as occurs 

 under very unfavorable market conditions or where the protection 

 of young stuff is the most important feature, wounded and sup- 

 pressed white firs left standing should not be older than 100 years, 

 since in 30 years they will have reached their critical age that is, 

 130 years. After they have reached this age it appears that dam- 

 aging decay becomes prevalent in trees of this description. Very 

 severely injured trees have, of course, no place in the managed 

 forest. The same is true for unusually suppressed or unhealthy 

 trees, unless it may be expected with reasonable certainty that the 

 opening of the crown cover will benefit them materially. Trees with 

 open fire scars and with open frost cracks should be cut in preference 

 to those with lightning scars or those having wounds from falling 

 neighbors. In short, all wounds reaching far into the wood are to 

 be given a higher rating with respect to decay than superficial wounds 

 unless the latter are unusually large. 



PATHOLOGICAL ROTATION AND CUTTING CYCLES. 



Since we may expect that cutting during the period of transition 

 will practically eliminate all those trees which by their combination 

 of suppression and wounding become subject to early decay (critical 

 age), the age of decline forms the basis for what might be termed the 

 "pathological rotation," for want of a better expression. It does 

 not indicate that a given species should most advantageously be cut 

 in regular intervals expressed by the pathological-rotation age, but 

 that it should not be cut at a higher age. It is really a factor limiting 

 the rotation and therefore also the cutting cycle. 



Rotation based on maximum volume alone can not be more than 

 a makeshift during the transition period; logically it should be nar- 

 rowed down to maximum-volume production of sound timber. Such 

 species as Sequoia gigantea and Sequoia sempervirens are so resistant 

 to decay that their pathology will not influence then- rotation at all. 

 In some of our valuable pines the pathological rotation will probably 

 be very high, either coinciding with or reaching beyond the age of 

 maximum-volume production. In white fir, incense cedar, and a 



