4 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. 



This "generality," in which almost every word is open to criticism, 

 seems to have become one of the stand-bys of American forestry. It 

 finds its chief support in the assumption that our forests to-day, 

 having been untouched by man and exposed to the same factors of 

 their surroundings since times immemorial, must represent more or 

 less exactly the same character they had 100 or 1,000 years ago. But 

 we have practically no genuinely virgin forests; in the great majority 

 of commercial accessible stands — and here we are interested only in 

 these — man has for centuries practiced some kind of primitive for- 

 estry by setting fires. This "Piute forestry" has changed the aspect 

 of many stands so completely that the term "virgin forests" is far 

 from being correctly applied. At best, can one speak of scattered 

 virgin stands here and there. Even in the latter the assumption that 

 the present stand has more or less the same character as 100 to 1,000 

 years ago reposes upon another assumption, namely, that here the 

 ecological formation has reached the final stage of development and 

 has come to stay. Of the remaining part of the cited rule of thumb 

 all factors are more or less unknown. 



Our knowledge of increment is, according to Chapman, "con- 

 spicuously lacking." 1 We know just as little about actual extent 

 and progress of decay in virgin forests, so that the "generality" is 

 reduced to an equation in which all factors are unknown. Besides, 

 the term "decay" leaves out all losses from the decrease in number 

 of trees steadily going on in the forest, as in every community of 

 living beings. Prompted, perhaps, by a subconscious realization of 

 this fact, the term "decay" in the equation is sometimes supplanted 

 by "deterioration." This makes matters even worse. Deteriora- 

 tion in this connection often means the visible loss irrespective of 

 cause. It is primarily a numerical consideration. A number of 

 trees containing certain amounts of timber annually drop out through 

 various causes, and this loss is then said to offset the annual incre- 

 ment. Secondarily, it might include loss from decay. In forest 

 regulation it is not the number of trees and the volume of timber they 

 produce per acre that count, but the volume of sound, merchantable 

 timber that we can expect to raise; and the only factor in the equa- 

 tion of any value would be, therefore, not decay only and deteriora- 

 tion or numerical loss of individual trees but "total loss." The 

 components of this total-loss factor are known. They include the 

 dropping out of individual trees by death from suppression or " old 

 age," fire, snowbreak, lightning, windfall, insects, diseases of vital 

 parts of the tree, and finally loss through decay. What we do not 

 know are the respective values to substitute for these components 

 in the actual figuring of total loss. 



1 More recently Barrington Moore has published a valuable study — Yield in uneven-aged stands — in 

 Proc. Soc. Amer. Forest., v. 9, no. 2, pp. 216-228, 1914. 



