The North American Forest 19 



species reached the place, they found the light con- 

 ditions favorable all over the locality, but in one 

 half of it the soil or the moisture relations were 

 such that the newcomers could not endure it. 

 Then the result of the war would be, that on one 

 half of the tract the beeches have superseded the 

 oaks, while on the other the oaks remain in un- 

 diminished vigor. The conditions affecting the 

 outcome are rarely so simple as we have here as- 

 sumed for the sake of clearness. Ordinarily, they 

 are exceedingly complex, so that it becomes very 

 difficult to trace them. But a knowledge of these 

 processes is necessary for the skilful pursuit of sil- 

 viculture. One important practical rule we may 

 mention here, which is based on this observation 

 that the species of tree growing in any given place 

 is not always directly regulated by the natural cir- 

 cumstances of the locality, but influenced by the 

 competition of other species. It is this : The fact 

 that in any region a species is never found except in 

 places of some special character, as in swamps, or 

 on sandy soil, does not prove that it will not flour- 

 ish elsewhere. It may have been driven into these 

 retreats by its competitors, and would really much 

 prefer the better places from which it has been ex- 

 cluded by them. This may often be of importance 

 in silviculture, when it is desired to grow a tree 

 outside of its apparent favorite habitat. 



Just as each species competes with every other 

 species for the most favorable places, so every in- 

 dividual tree competes with every other, whether 



