756 JOURNAL OF FORESTRY 



sites are then to be recognized either by the identification of similar 

 indicators or by determining the similarity of the physical site factors. 

 These may be measured in precise terms or simply estimated. Precise 

 measurements appeal to the investigator. Accepting the permanent 

 type as an indicator, for example, it would only remain to learn quan- 

 titatively the physical factors determining it. These physical factors, 

 wherever found interacting in precisely the same amounts, will always 

 produce in time, barring accident or design, precisely the same form 

 of forest. The plan of a classification based on physical factors appeals 

 to the investigator because it is truly fundamental. The apparent diffi- 

 culties in deciding what is the permanent type in the isolation and meas- 

 urement of the several physical factors, etc., may not be so formidable, 

 after all, and the work may be simplified by the discovery that only one 

 or two of the factors are of particular significance. But one is forced 

 to conclude that we are far from a solution, except possibly in a few 

 regions of simple forest distribution, and that the time is far oiT when 

 we can adopt such a classification for the entire country. The problem' 

 is complicated by practical demands, such as the need of knowing: 

 promising sites for temporary as well as for permanent forms of forest. 

 Since each temporary type has its own particular relation to site, not 

 coincident with that of the permanent type, this, too, would logically 

 demand a determination. The whole matter of the relative importance 

 and the measurement of physical factors is still in the experimental 

 stage and still subject to differences of expert opinion.® Much time 

 will likely elapse and many revisions be necessary before a working 

 agreement can be reached, and it is no argument against the study of 

 physical factors to say that for the present we must get along without 

 it, so far as a general classification of sites is concerned. 



As a fundamental guide in silviculture, the value of a knowledge of 

 the permanent forest type is beyond dispute, if only as a menace to be 

 provided against. It would assure the forester as to the inevitable nat- 

 ural succession on a particular site and facilitate his choice of silvicul- 

 tural methods to combat or to hasten the process. As a matter of fact,, 

 in many parts of the country foresters already know in a general way 

 what to expect, although in the later stages of the succession, when two 

 or more species are fighting for supremacy, the result may be difficult 

 to foretell. In these later stages, too, the result may be easily con- 



° In his paper on Plant Formation and Forest Types (Proc. Soc. Amer. For- 

 esters, IV, I, pp. 50-63), Dr. Clements makes the following statement: 



"From its nature, the building of such a foundation will be a slow and 

 painstaking task, in which quantity of result and time must be almost completely 

 ignored, and accuracy and permanence alone considered." 



