42 THE PRINCIPLES OF HANDLING WOODLANDS 



5. Cost of Reproduction. Some species cost more than 

 others to reproduce, both artificially and naturally. 



6. Resistance to Injury. Species subject to damage by 

 wind, insects, disease, or other damage may be rejected, 

 even though otherwise desirable. A species may some- 

 times be favored primarily because of its ability to resist 

 fire. 



7. Silvicullural Value. A species may be of special 

 value in its influence on the growth of its neighbors or 

 in conserving the factors of site. Thus, hemlock in 

 mixture with pine helps the development of the latter, 

 and furnishes an excellent soil cover. 



8. Esthetic Value. Sometimes a species is chosen 

 because of its peculiar value from the esthetic or senti- 

 mental standpoint. This question becomes of impor- 

 tance on private estates, and those public forests which 

 are used as recreation resorts. 



Pure and Mixed Stands Contrasted 



A pure stand is one composed of a single species. 

 As the terms are used in this country, the stand is called 

 pure if 80 per cent, of the main crop is composed of one 

 species. If there are two or more species, and no one of 

 them comprises over 80 per cent., it is a mixed stand. 

 The aim of forestry is to reduce the proportion of the 

 less valuable species in the forest. Ultimately the un- 

 desired species will be represented only as scattered, 

 accidental specimens. The tendency in forestry is 

 constantly toward pure stands. This is especially true 



