FORESTS OF THE UNITED STATES 63 



Rocky Mountain region and the other in the Pacific Northwest. 

 The eastern forests were made up chiefly of broad-leaf trees 

 and covered mountains and valleys in a great unbroken mantle 

 of green. The western forests, on the other hand, are composed 

 principally of softwoods and are interrupted by many treeless 



REGIONS OF 

 NATURAL VEGETATION 



NATURAL VEGETATION OF THE U. S. 



The three great divisions of natural vegetation in the United States arc forest, grass 

 and desert. Rainfall is the most important factor in the creation of these regions. 



valleys. In them, unlike the eastern forests, we find very abrupt 

 changes in species. 



The eastern forests contain over four hundred species of 

 broad-leaf trees. Many of them extend over large areas and 

 have high market value. The Western forests have about one 

 hundred broad-leaf species, very few of them valuable to man. 



The western forests are essentially softwood or evergreen 



