256 CLARENCE F. KORSTIAN 



in a very definite manner. Therefore, in the determination of 

 site quality a detailed consideration of the individual causal 

 factors is not as essential as the combined effect, which is ex- 

 pressed in the resultant growth or increment. The native 

 plants, in their response to the habitat factors, may be regarded 

 as showing the effect of the summation of these factors as they 

 influence growth. 



The scientific study of forest vegetation must in the future ac- 

 company rational silvicultural and range management more 

 closely than now, and in fact, as soon as possible, should precede 

 it. The time has come for intensive investigations of this nature 

 which will form the foundation upon which the superstructure 

 of practical forest regulation will be built permanently. When 

 the relation between the silvicultural characteristics and the 

 physical factors which affect tree growth and the correlation of 

 increment with the associated shrubby and herbaceous species 

 are better understood, the different sites may be regarded as 

 integral biological units which the administrator can use as a 

 basis for the rational organization of his forest. 



The importance of a correlation between the site factors and 

 the silvical requirements of the arborescent species has been em- 

 phasized by Tourney. 8 The difficulty involved in the exact 

 measurement of the physical factors of the site and the interpre- 

 tation of the vegetation in terms of site factors is indicated. 

 The herbaceous or shrubby vegetation can be used by the prac- 

 ticing forester in a field evaluation of the site factors, and in de- 

 termining the site quality or the yield capacity. This method 

 is particularly desirable when the productivity of a site must be 

 assessed without the aid of forest trees. 



In order to effect a proper correlation of site conditions, the 

 forester must be well acquainted with the natural forest vegeta- 

 tion and the manner in which it is influenced by the physical 

 factors of the site. The lack of a fundamental biological train- 

 ing is admitted by many foresters and is shown by the work of 

 others. A training in the natural sciences is an absolute pre- 



8 Toumey, James W. Seeding and Planting in the Practice of Forestry. 

 Pp. 40-43, New York, 1916. 



