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A COMPARISON OF THE VEGETATIONAL FEATURES 

 OF TWO DESERT MOUNTAIN RANGES 



FORREST SHREVE 



The Desert Laboratory, Tucson, Arizona 



In southeastern Arizona and southwestern New Mexico there 

 are a number of forested mountains which are separated from 

 one another by desert plains and valleys. The irregular plateau 

 upon which these mountains stand is a portion of the continental 

 divide, draining westward into the Gila River and eastward into 

 the Rio Grande. The greater part of the so-called plateau lies 

 between 3000 and 5000 feet in elevation, being in fact the lowest 

 part of the continental divide between northern Canada and the 

 Isthmus of Tehuantepec. 1 None of the mountains exceed a 

 length of 25 miles, but many of them lie in broken chains, usually 

 running in a NNW-SSE direction and connected by low hills or 

 narrow passes. Immediately south of the group of mountains 

 under consideration lies the northern end of the Sierra Madre 

 Occidental, which forms the boundary between the states of 

 Sonora and Chihuahua, and north of the group are the White 

 Mountains and the Mogollon Mesa, which form the southern 

 edge of the Colorado Plateau. Far to the northeast lies the 

 southernmost portion of the Rocky Mountains, in northern 

 New Mexico. 



It is only on the mountains which exceed 7000 feet in eleva- 

 tion that forested areas are to be found, although lesser eleva- 

 tions are frequently occupied by low or open woodland. The 

 principal mountains in the group under consideration are: 

 Baboquivari, Santa Catalina, El Rincon, Santa Rita, Huachuca, 

 Pinaleno, Chiricahua, Las Animas and San Luis. Among the 



1 The Southern Pacific Railroad crosses the continental divide near Separ, 

 New Mexico, at 4502 feet, and the El Paso and Southwestern Railroad crosses it 

 near Vista, New Mexico, at 4679 feet. 



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