TIMBER; FORESTRY 



113 



group oaks, elms, and ashes; hi another, oaks and hicko- 

 ries; in another, beeches and maples (fig. 95). Along the 

 fertile river bottoms of the Middle West one may often find 

 a combination of sycamores, oaks, ashes, black walnuts, elms, 

 and hackberries. 



106. Tolerant and intolerant trees. A tree which can endure 

 a good deal of shade is said to be tolerant. Examples of this 

 are the hemlock and red spruce, among conifers, and the 

 beech and maple, among hard 

 woods. Trees which require 

 much light are said to be intol- 

 erant. Examples are the white 

 pine and the larch, among 

 conifers, and the oaks, hicko- 

 ries, and chestnuts, among 

 hard woods. As a rule, seed- 

 lings require far less light 

 to begin life than is needed 

 to enable the mature tree to 

 reach its maximum size. So 

 it often happens that seedling 

 trees may survive for years on 

 the forest floor, making but 

 little growth until the decay 

 and fall of overshadowing trees, 

 their destruction by wind, or 

 their removal by the lumber- 

 man enables the seedling to grow rapidly into a large tree. 



The relative tolerance of trees is an important topic in prac- 

 tical forestry, since the succession of forest growths often 

 depends largely upon this factor. White-pine seedlings could 

 not be made to grow under a good stand of pine or hemlock 

 timber, but young hemlocks or red spruces would succeed 

 there. On the other hand, white-pine seedlings can grow in 

 an aspen forest, and white oak and maple seedlings can grow 

 in an oak-maple forest. 



FIG. 95. Primeval deciduous mixed 

 forest of maple and beech 



