DESERT COMMUNITIES 



251 



148. Desert Communities.— Deserts are found where the annual 

 rainfall is uniformly low, usually below 15 inches, and the evapora- 

 tion rate is high, liecause of these environmental conditions the 

 \e<!;etation is ^ery xeric. 



In the Ignited States two general types of desert vegetation may 

 be recognized. The first is the sagebrush {Artemisia) type which 

 occupies the northern part of the desert region where the rainfall is 

 fairly well distributed throughout the year (Fig. 113). This type 

 of desert occurs extensively in Wyoming, western Colorado, northern 

 Arizona, Utah, Xe^'ada, southern Idaho, southeastern Oregon, 

 central Washington, and in central and southern California. Its 



Fig. 113.— Sagebrush desert. Utah. (Photograph by H. L. Shantz. Courtesy 

 of H. L. Shantz and the U. S. Department of Agriculture.) 



most typical development is in the central portion of the Great 

 Basin where the most characteristic dominant is Artemisia tridentata 

 accompanied by other species of Artemisia, rabbitbrush (Chryso- 

 thamnus) and other xeric shrubs. The California sagebrush is very 

 similar in appearance to that in the Great Basin but its dominants 

 are different. The most important sagebrush there is Artemisia 

 californica and this is accompanied by shrubby species of sage 

 ((Safoia) , buckwheat (Eriogonvm) , beardtongue {Penstemon), sumac 

 {Rhus), and various others. Cacti are not characteristic of this type 

 of desert. 



The southern part of the desert region is occupied by the creosote 

 bush {Larrea tridentata) and cactus desert (Fig. 114). The climate 



