36 



A PRIMER OF FORESTRY. 



THE RATE OF GROWTH. 



The rate of growth of differeDt trees often decides 

 which one will survive in the forest. For example, if 

 two intolerant kinds of trees should start together on a 

 burned area or an old field, that one which grew faster 

 in height would overtop the other and destroy it in the 

 end by cutting off the light. Some trees, like the 

 Black Walnut, grow rapidly from their earliest youth. 



Fig. 34.— Pure forest of Western Yellow Pine in the Black Hills of South Da- 

 kota. The trees here are smaller in size than those of Montana (see tig. 35), 

 but tlieir jiower of reproduction is much greater. 



Others grow very slowly for the first few years. The 

 stem of the Longleaf Pine, at 4 years old, is usually 

 not more than 5 inches in length. During this time 

 the roots have been growing instead of the stem. The 

 l^eriod of its rapid growth in height comes later. 



The place where a tree stands has a great infiuence 

 on its rate of growth. Thus the trees on a hillside are 

 often much smaller than those of equal age in the rich 



