ClIAl'lER V. 



THE FOREST OBGANISM. 



The forest is much more than an assemblage of different trees, it 

 is an organism; that is, the trees that compose it have a vital rela- 

 tion to each other. It may almost be said to have a life of its own, 

 since it has a soil and a climate, largely of its own making. 



Without these conditions, and without the help and hindrance 

 which forest trees give to each other, these trees would not have their 

 present characteristics, either in shape, habits of growth or nature 

 of wood grain. Indeed, some of them could not live at all. 



Since by far the greater number of timber trees grow in the for- 

 est, in order to understand the facts about trees and woods, it is neces- 

 sary to know something about the conditions of forest life. 



A tree is made up of three distinct parts: (1) the roots which 

 anchor it in the ground, and draw its nourishment from the moist 

 soil; (2) the trunk, or bole, or stem, which carries the weight of the 

 branches and leaves, and conveys the nourishment to and from the 

 leaves; (3) the crown, composed of the leaves, the branches on which 

 they hang, and the buds at the ends of the branches. As trees stand 

 together in the forest, their united crowns make a soit of canopy or 

 cover, Fig. 55, which, more than anything, determines the factors 

 affecting forest life, viz., the soil, the temperature, the moisture, and 

 most important of all, the light. 



On the other hand, every species of tree has its own requirements 

 in respect to these very factors of temperature, moisture, soil and 

 light. These are called its silvical characteris'ics. 



SOIL. 



Some trees, as black walnut, flourish on good soil, supplanting 

 others because they are better able to make use of the richness of the 

 soil; while some trees occupy poor soil because they alone are able to 

 live there at all. Spruce, Fig. 56, will grow in the north woods on 

 such poor soil that it has no competitors, and birches, too, will grow 



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