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TEXTBOOK OF BOTANY 



Pinon-juniper woodlands (Fig. 417). Usually below the western yel- 

 low pine belt where the rainfall is somewhat less or the evaporation 

 greater, there are extensive open woodlands particularly in the Great 

 Basin region between the Sierras and the Rockies and on the Arizona 



Fig. 417. Juniper and pinon pine form the characteristic woodland on the plateaus 

 and lower slopes of mountains in the Southwestern States. Photo by U. S. Forest 

 Service. 



plateau. Two small species of pine and several species of juniper occur 

 in various combinations over vast areas. Collectively they may be called 

 the pinon-juniper woodland. South of the Arizona plateau it is mixed 

 with and finally replaced by scrub oak woodlands (encinal). Below it 

 are the still drier grasslands and semi-desert scrub. 



The higher levels of the Mexican plateau are also covered by pine 

 forests, which contain at least 6 species in addition to the western yellow 

 pine. Douglas fir is again present on mountains above 9000 feet, with 

 lodgepole pine, trembling aspen, and a Mexican fir. At levels below the 

 pine forests are areas of the pinon-juniper, or the scrub oak encinal, 

 together with shrubs and low trees of the dry tropics. 



