The Sonoran, or Arboreal, Desert

Named for the State of Sonora, Mexico, in which the greater portion of it lies, the Sonoran Desert is one of four divisions of the North American desert of the Southwest. Each division is characterized by plant and animal communities or associations, some of which are represented in several or all of the divisions while others are restricted to only one. The giant saguaro, for example, is found only in the Sonoran Desert whereas the creosotebush and ocotillo occur in three.

Within the Sonoran Desert, different elevations have temperature and precipitation variations which exert a profound influence upon plants and animals. An example of this is the Tanque Verde-Rincon uplift rising across the eastern end of the monument. This uplift and the adjacent Santa Catalinas are high enough to intercept the prevailing movement of rain-clouds causing greater rainfall on the mountains than in the surrounding desert. The greater moisture and lower temperature of these highlands create conditions favorable to an entirely different plant-animal ecology.