Standardisation of Instruction. 355 



ground covers, such as sphagnum and other mosses, ferns, flower- 

 ing plants, etc. 



In addition to the changes in the external conditions of the Hfe 

 of forest trees which arise as soon as they form stands, or tree 

 societies, there occur other processes in the hfe of the forest itself 

 which are the result of the aggregate or social life of the forest 

 trees. The most important processes are the struggle for existence 

 between trees of the same stand and the process of differentiation 

 of trees into dominant and suppressed. The rapidity of these 

 differences is dependent upon the physical conditions of the site 

 as well as upon the conditions of the stand itself (density, com- 

 position, etc.). What are the causes of this differentiation of 

 trees into dominant and suppressed classes, and what is the 

 silvical importance of these processes? In connection with the 

 differentiation of trees into dominant and suppressed classes, it 

 may be advisable to explain the general laws of growth of stands, 

 the influence of soil and climatic conditions on the increment of 

 stands, and the basis for classifying the conditions of growth into 

 site classes or quality classes. Here also would be the proper 

 place to explain that the natural thinning of stands does not mean 

 only a change in the increment of the stand but brings about 

 a change in the ecological or silvical conditions of the stand as 

 well. The light conditions under forest cover, the soil protective 

 capacity of the trees, the character of the living and dead ground 

 covers all change in the natural process of thinning of the stand. 



Aside from the direct struggle for existence among trees of 

 the same stand, there may be observed also other relations which 

 are more in the character of co-operation. Here belong the 

 assistance which one species gives to the other by forcing it up- 

 ward, by clearing its dead branches, etc. x^nother social function 

 is the natural regeneration of the forest itself, the appearance of 

 a new growth under the cover of the old one and also outside of 

 the forest on ground not yet occupied by forest. The natural 

 regeneration of a stand depends upon conditions created by the 

 stand as a whole. These conditions should be considered now 

 with special application to natural regeneration. In connection 

 with the discussion of the spreading of a forest upon ground not 

 yet occupied by it, it is necessary to discuss the influences of 

 stands upon the land surrounding it. A comparison must 



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