THE FOREST FAMILIES 23 



In the forests of the Rockies the evergreens stand 

 some distance apart so that their tops do not 

 touch. As a result, these Western forests do not 

 shade the ground as well as those in the east. 

 This causes the soils of these forests to be much 

 drier, and also increases the danger from fire. 



The forests of western Washington and Ore- 

 gon, unlike most timberlands of the Rocky Moun- 

 tain Region, are as dense as any forests in the 

 world. Even at midday it is as dark as twilight 

 in these forests. The trees are gigantic. They 

 tower 150 to 300 feet above the ground. Their 

 trunks often are 6 feet or larger in diameter. 

 They make the trees of the eastern forests look 

 stunted. They are excelled in size only by the 

 mammoth redwood trees of northern California 

 and the giant Sequoias of the southern Sierras. 



Differences of climate have largely influenced 

 tree growth and types in this country. The dis- 

 tribution of tree families is changing all the time. 

 It shifts just as the climate and other conditions 

 change. Trees constantly strive among them- 

 selves for control of different localities. For a 

 time one species will predominate. Then other 

 varieties will appear and displace the ones al- 

 ready established. The distribution of trees 



