HEIGHT GROWTH AS A KEY TO SITE ' 



By E. H. Froth INGHAM 

 Forest Examiner, U . S. Forest Service 



I think it is unnecessary to emphasize the peculiar importance in 

 America of a standard rational classification of forest sites. Mr. Zon- 

 has called it "our silvical mission" to perfect such a system — a result 

 never yet achieved in any country. The mass of conflicting opinion 

 and evidence published on "site" and "type" are sufficient proof both 

 of the importance of the subject in the minds of foresters and of the 

 perplexities which will have to be overcome before a practicable plan 

 can be agreed upon. The writer's excuse for adding yet another paper 

 on this subject is a study on which he and Mr. Russell Watson were 

 engaged last summer in the southern Appalachians, which had for its 

 object the beginning of classification of forest sites on the basis of 

 height growth. Since this, so far as known, is the first actual field 

 study which has been made toward this end, the ideas which have 

 grown out of the field-work and a partial compilation of the results 

 may be worth contributing. 



A great deal of confusion can, it seems to me, be cleared away by 

 showing clearly the difiference in object between the two principal 

 schemes of classification which have been suggested within recent years, 

 namely, (i) that advanced by Mr. Zon," the identification of the per- 

 manent forest types of the country and the determination of the physi- 

 cal factors responsible for them, and (2) Professor Roth's* proposal, 

 amplified by Mr. Watson,'' to classify all the tree species of the country 

 according to the height attained at a specified age on the best sites, and 

 to base site classes for each species on the degree by which the height 

 falls ofif from this maximum, the height index of site being at arbi- 

 trarily chosen intervals. The important difiference is that while Zon 



^ Presented at the annual meeting of the Society of American Foresters at 

 Pittsburgh, January i, 1918. 



° Zon, Raphael : Quality Classes and Forest Types. Type Symposium in 

 Proc. Soc. Amer. Foresters, VIII, i, pp. 100-104, 1913. 



'Zon, Raphael: Principles Determining Forest Types. Proc. Soc. Amer. 

 Foresters, I, 3, pp. 179-189, 1906. 



* Roth, Filibert: Concerning Site. Forestry Quarterly, XIV, i, pp. 3-12, 1916. 



'^ Watson, Russell : Site Determination, Classification, and Application. Jour, 

 of Forestry, XV, 5, pp. 552-563, I9i7- 



"^A 



