Periodical Literature 393 



Again, stands, which treated by thinnings in the subdominant 

 furnish equal yields, may behave quite differently under thinnings 

 in the dominant. Not yield classes, but real forest site classes are 

 needed ; such a site class to comprise all the places which under all 

 silvicultural operations approximately behave alike. The limits 

 of the classes will have to be agreed to by practical considerations 

 and the classes are to be determined by the best available soil 

 knowledge. When such classification is attained the observing 

 forest manager will relate his experience to such site classes and 

 recommend only for such his operations. 



The general rule that there is no general rule is applicable in 

 forest organization where subjective considerations must enter. 

 But in silviculture this is different ; for silviculture is a doctrine 

 of the consequences of human interference with nature; the same 

 kind of interference under the same conditions must have the 

 same result. It must, therefore, be possible, as with other natural 

 history-technical sciences, for silviculture to bring together all its 

 experiences into a whole less and less contradictory. To attain 

 this, the author insists, the finer distinction and description of 

 sites is necessary. 



To be sure, the author admits, that the knowledge to do this 

 efficiently, is but poorly developed and hence difficulties arise. 

 These the experiment stations themselves must first overcome as 

 one of the primary most important undertakings. "The present 

 status of experimentation forces the open acknowledgment that 

 the art of inaugurating silvicultural experiments is much more 

 difficult than had been assumed when the experiment stations 

 were founded and the desire by the experiments to solve directly 

 qustions arising in practice has led to neglect in furnishing the 

 fundamentals for a successful experimentation (except in mensu- 

 ration)." To develop this neglected art, to further for its own 

 sake the art of experimentation and description of experiments 

 will most certainly further the solution of problems for the 

 practice much more rapidly. 



A hint as to how to proceed with site description is given by 

 referring to Liebig's law of the minimum which the author 

 phrases happily into : "the fertility of a site is limited by its 

 most unfavorable factor." Hence for an exhaustive site descrip- 

 tion the ascertainment of that factor which prevents a better 

 development than the existing is indicated. Such a determination 



