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THE AMEBIC AX NATURALIST [Vol. XL VII 



therefore, begins the struggle for space and the differen- 

 tiation into dominant and suppressed, with the subse- 

 quent dying out of the latter. They have followed this 

 process throughout the entire life of the stand, have es- 

 tablished its various degrees of severity, and have dis- 

 covered its culmination during the period of the most 

 rapid growth in height. This struggle for space and 

 light is the basis of the forester's operations, as only by 

 utilizing and controlling it is he capable of producing 

 wood of high technical qualities, tall cylindrical boles, 

 free of branches, and wood with uniform annual rings 

 possessing great elasticity. Without this struggle there 

 is no forest, there is no production of valuable timber, 

 save firewood. 



The struggle for existence in a forest stand is not con- 

 fined to individual members of the same age or the same 

 story, but the forest, as a whole, battles for its existence 

 against the adjoining meadow, swamp or shrub vegeta- 

 tion; the old trees against the young growth that comes 

 up under them ; groups of trees of different species or of 

 different ages against each other. In this struggle the 

 forest accomplishes what no other vegetation does; 

 namely, it actually changes the climate over the area oc- 

 cupied by it, and makes it inhospitable for its enemies. 

 The forest creates its own interior environment to which 

 its own members are completely adapted, but in which 

 other species find either too much or too little light, the 

 humus too scant or too deep, or too acid, the temperature 

 too high or too low. Whatever it may be, the forest's 

 competitors are eliminated through the changed environ- 

 ment. To change this environment, however, there must 

 be a close stand, there must be present the struggle for 

 existence among the individual members of the stand. 

 Through interior struggle among its own members the 

 stand secures resistance against invasion by other vege- 

 tation. How manifoldly broad and deep, then, is the 

 struggle for existence in the forest. 



When we come now to natural selection nowhere else is 



