94 OUR FEDERAL LANDS 



occurs in many isolated sections, great and small, de- 

 pendent upon altitudes. The main range of the 

 Rockies carries a ribbon of forest on either side its 

 barren and often snow-covered crest. So also many 

 of their component ranges, like the Bighorn, the Ab- 

 soroka, the Wasatch, and the Sangre de Cristo. So 

 also the Cascades and the towering Sierra. So also 

 isolated mountain masses in various parts of the 

 west, like the San Francisco Peaks in Arizona. So 

 also many lofty plateaus, like the splendid Kaibab 

 forest north of the Grand Canyon, which, with its 

 teeming population of deer, is wholly surrounded by 

 desert. When we speak of the Western Forest, we 

 mean all of these forested ribbons and fragments 

 considered as one. 



Because conditioned by altitude, the western 

 forest far more than the eastern is affected by the 

 life zones which belt lofty mountains, so that a jour- 

 ney from the hot plains of California to the bald 

 summit of the high Sierra, for example, will encoun- 

 ter gradations of vegetation and animal species simi- 

 lar to those encountered in a lowland journey from 

 the Gulf to the Arctic. 



Roughly differentiating the tree stocks of the 

 two main divisions of the western forest, that of the 

 Rockies and that of the Cascades and the Sierra, 

 very much is found in common, zone compared with 

 zone and latitude considered. In the north of both, 

 we find Douglas and lowland white firs, western red 

 cedar, lodgepole and western white pines, Engel- 



