562 



NATXJRALIST'S GUIDE TO THE AMERICAS 



in the vicinity of these settlements 

 were materially changed through the 

 denudation of the mountains as a result 

 of unregulated timber cutting, un- 

 restricted grazing, fires, and the re- 

 sultant erosion. Since the creation 

 of the National Forests in the moun- 

 tains, the U. S. Forest Service has in- 

 augurated systems of timber cutting 

 and regulated grazing which favor the 

 ultimate restoration of the forest and 

 the forage plants on the lands under 

 its management. 



None of the major vegetational asso- 

 ciations have been destroyed, except 

 locally. Many desert areas, because 

 of the extreme aridity, will doubtless 

 remain in essentially a natural condition. 

 The forest conditions have been de- 

 scribed by Baker and Locke^ in con- 

 nection with the discussion of the 

 National Forests. The location of the 

 Forest Supervisor's headquarters is 

 also given. 



The Southern Pacific and Los Angeles 

 and Salt Lake Railroads pass through 

 the desert for the entire distance which 

 they traverse the state. Side trips 

 into the heart of the desert can be made 

 from many of the towns along these 

 railroads, the larger of which are Pali- 

 sade, Elko, Battle Mountain, Winne- 

 mucca Reno, Caliente, Modena, and 

 Las Vegas. The Overland Trail and 

 the Lincoln Highway automobile routes 

 from Utah to California cross the state 

 northerly and the Arrowhead Trail 

 crosses the southern tip. 



Aside from the National Forests and 

 Indian Reservations no specially re- 

 served areas within Nevada have been 

 brought to the attention of this 

 Committee. 



*The Lehman Cave National Monument 

 in Nevada is an area of commonplace 

 pinyon-juniper woodland, similar to 

 thousands of acres elsewhere in Nevada, 

 much more readily reached. This cave 

 has been insufficiently studied for 

 anything to be known regarding the 

 animal life that may be present. — 

 F. S. Baker. 



' This volume, page 224. 



3. ARIZONAi 



By G. a. Pearson, E. A. Goldman, 



Forrest Shreve and Charles 



t. vorhies 



I. general topography (f. s.) 



The state is one in which altitude and 

 topographic features are of basic im- 

 portance in determining the distribu- 

 tion of the widely dissimilar types of 

 biota found within its 113,020 sq. mi. 

 of extent. The conditions of tempera- 

 ture and rainfall are themselves deter- 

 mined by altitude much more than by 

 the 5f ° of difference in latitude between 

 its southern and northern borders. 



The most elevated part of Arizona 

 is a broad ridge running from the north- 

 west corner to the center of the eastern 

 boundary, and forming the southern 

 edge of the Colorado Plateau. The 

 broadest part of this ridge, in the north- 

 western part of the state, has been cut 

 by the Grand Canyon of the Colorado 

 and dissected by other streams. The 

 southeastern end of the ridge, known 

 as the Mogollon Mesa, is narrow, has 

 been less dissected, and culminates 

 near the New Mexican line in the White 

 Mountains, embracing some of the 

 highest elevations in the state. Super- 

 posed on the Mogollon Mesa, in the 

 center of the northern half of Arizona, 

 are the volcanic San Francisco Peaks 

 (elevation 12,794 ft.) About 175 mi. 

 to the southeast Ord Peak (10,266 ft.) 

 and Escudilla Peak (10,691 ft.) form 

 the summits of an extensive elevated 

 region. On going northeast from any 

 part of the Mogollon Mesa the descent 

 is gradual into the plain drained by the 

 Little Colorado River, lying between 

 5000 and 6000 ft. in elevation. This 

 plain is bordered on the north and east 

 by a plateau 6000 to 8000 ft. in elevation 

 and by low mountains. On going 

 southwest from the Mogollon Mesa 

 into the drainage of the Salt and Bill 

 Williams Rivers, the descent is abrupt 



1 Where there was no cooperation between the 

 different authors, the names stand in the order of 

 receipt of manuscripts. The committee has ar- 

 ranged the parts and indicated authorship. 



