FOREST PATHOLOGY IN FOREST REGULATION. 5 



The same laxity noted in the use of the terms " decay" and "de- 

 terioration" is commonly found in the use of the term "decadence," 

 as applied to a stand or a given species, which is often understood to 

 include individual decadence from old age; that is, arrested or min- 

 imized growth, liability to attack from fungi and insects, and finally 

 decay. The fact that a given species is unusually liable to heart rot 

 does not make it decadent. Many of our most thrifty and aggres- 

 sive species are particularly subject to heart rot. It is also doubtful 

 whether this hypothetical knowledge, if ever attained, of the total 

 rate of total loss in "virgin" forests, as compared with the equally 

 hypothetical rate of increment of the forests as a whole, would help 

 us to any extent. The vastness of our forests in area creates a 

 tendency either to think in broadest terms and to overlook the fact 

 that a forest is an artificial unit made up of natural units; the stands 

 with all their immense variety of character, or, on the other side, to 

 take a familiar unit and to transfer its characteristics to the whole. 

 The latter mistake is more easily remedied than the first. As a 

 science, forestry must be founded upon inductive methods. Inten- 

 sive study of detail alone can form a solid basis for the formulation 

 of principles. 



What is needed is exact studies of all components of the total-loss 

 factor per species before we attempt to fix the total-loss factor for 

 the stand. 



Such detailed studies will be easiest in all-aged pure stands of a 

 thrifty species little liable to decay. Unfortunately the vast majority 

 of stands on national forests in the West are composed of two to 

 five or more species of very different characters. It may be that the 

 total annual loss equals the annual increment in some of the medium 

 long-lived species of the pine group least liable to decay. It can 

 not be true for the extraordinarily long-lived redwood and big tree, 

 with their unusual resistance to decay, insects, and storms. It is 

 equally untrue for all shorter lived species much exposed to decay 

 and other influences that make for loss. Libocedrus decurrens, for 

 example, although most aggressive and thrifty, is from an early age 

 on liable in an uncommon degree to the attacks of Polyporus amarus, 

 which renders as much as 70 or 80 per cent and even higher per- 

 centages of the stand completely unmerchantable. Merchantable 

 incense cedar is of high value; so much the greater, then, is the 

 total-loss factor The same is, mutatis mutandis, true for white fir 

 and a number of other species. For all these the increment is not 

 only offset but far exceeded by the decay of the valuable heartwood; 

 the total annual loss is far greater than the annual increment, 

 although numerically the loss may not be apparent. 



The gain through increment, we must remember, consists of sap- 

 wood of little value; the loss by decay, on the other side, affects the 



