HEIGHT GROWTH AS KEY TO SITE 757 



trolled and the forest maintained indefinitely by management in a state 

 totally different from that which would ultimately prevail in nature. 



In many large regions the permanent forest type is strikingly ap- 

 parent. In other places it remains exceedingly obscure. Even where 

 plainly evident, subdivisions with reference to yield are a necessity 

 from considerations of future as well as present management. 



This subdivision of permanent forest types or of any other kinds of 

 types can be effected by the use of an indicator. Indicator plants, vol- 

 ume growth, and height growth are means to this end. Under certain 

 circumstances the use of indicator plants may prove very useful, as 

 experiments by Korstian' and others indicate. Objections which ap- 

 pear to invalidate it for general application, however, have been pointed 

 out by Zon^ in his review of Cajander's* work on this subject; since 

 the indicator plants are not immune to the influence of biological factors 

 of the forest, this method cannot be considered to have promise as a 

 means of determining site except under special local conditions. 



The use of the current annual increment^" as a means of determining 

 site involves the double difficulty of securing a basis and of applying 

 the measure of the site, when found, to the identification of similar site 

 conditions elsewhere. As an exact indicator it may prove the last word 

 in refining previous site determinations in localities where it can be 

 employed, but as a general method, suitable for immediate use, it fails 

 to meet the requirements of simplicity and wide-spread utility previ- 

 ously set forth. 



The utility of height — one of the functions of volume, but far less 

 imwieldy as an index — ought to be plainly evident to every one as the 

 logical immediate basis for subdivision. Height growth, as a matter of 

 fact, appeals in two ways: First, as an immediate means of classifying 

 forest sites in general, and, second, as a guide and a short cut in arriv- 

 ing at a possible future classification of sites on a physical or perma- 

 nent type basis. There are a number of objections to the use of height 



' Korstian, Clarence F. : The Indicator Significance of Native Vegetation in 

 the Determination of Forest Sites. Plant World, vol. 2o, No. 9, pp. 267-287, 

 1917. 



' Zon, Raphael: Review of Prof. A. K. Cajander's Ueber Waldtypen. Proc. 

 Soc. Amer. Foresters. IX. pp. 1 19-125. 1914. 



* Cajander, A. K. : Ucber Waldtypen. Fennia 28, No. 2, 175 pp. Helsingfors, 

 1909. 



" Suggested by C. G. Bates in the following resolution, introduced at the meet- 

 ing of Forest Investigators, Washington, D. C, March i, 1917 (p. 304 of the 

 Proceedings of the Meeting) : 



"Resolzrd, That the only final criterion of site quality is the current annual 

 increment of the species concerned as judged by the measurement of a stand 

 approximately fully stocked." 



