THE PRINCIPLES WHICH DETERMINE SPACING 53 



gives 50,000 seedlings or more per acre. 1 When Scotch pine is 

 sown in prepared strips, Prussian practice requires a germination 

 of 10,000 to 15,000 per acre. Tolerant species, as a rule, should 

 develop in much closer stands than intolerant ones, hence they 

 require more seedlings per acre at the start. Where early thin- 

 nings cannot be profitably made, as is usually the case in the 

 United States, there is no material advantage in extremely close 

 spacing. If the seedlings are of uniform size, there is very decided 

 disadvantage because the competition tends to dwarf all alike. 

 Although in the United States a more open spacing is usually 

 acceptable in stands arising from direct seeding than in Euro- 

 pean practice, the author believes that we are in grave danger from 

 accepting too sparse stands arising in this manner as acceptable 

 reproduction. 



2. The Species as a Determining Factor in the Closeness 

 of the Stand from Direct Seeding 



The mode of growth of a species is an important factor in de- 

 termining how close the young trees should stand in the regener- 

 ation. Because of the length of time required to form a complete 

 canopy, species of rapid juvenile growth can be much wider 

 spaced than slow-growing ones. Spruce will develop in good form 

 under a more open reproduction than most species of pine. Close 

 spacing is needed with species that have a spreading crown form, 

 as in oak, beech, and maple. 



The young seedlings of forest trees are more or less subject to 

 injury by animals, insects, fungi, and the effects of climate such 

 as frost, drought and excessive moisture. The ability of a species 

 to resist these various forms of injury is also a factor in determin- 

 ing the density of the stand. 



3. The Quality of the Site as a Determining Factor in the 

 Closeness of the Stand from Direct Seeding 



As the quality of the site influences the growth and vigor of the 

 young plants and the percentage of failures after germination, it 

 is a determining factor in density. When the growth is likely to 

 be slow and the percentage of loss large, the young seedlings 

 should stand closer than when the same species are used for re- 



1 Hauch, L. A.: Buchen- und Eichenkulturen in Bregentved, Danemark. 

 (Centralblatt f. d. gesamte Forstwesen, S. 14^-164 u. 205-222. 1913.) 



