GRASSLAND COMMUNITIES 



247 



ing to the three genera, Pimis, Junipenis, and Quercus. In Cali- 

 fornia the digger pine (P. sohiniann) is important l)ut elsewhere the 

 pine that is concerned is the jnnyon pine {P. conbruide.s- and its 

 \arieties). In the northern part of the range the juniper that is 

 most imi)ortant is J. utahens is while farther south it is J. monosperma 

 and in some places J. pachyphloca. In the Chisos Mountains of 

 Texas the weeping juniper (J. flaccida) is an added constituent 

 while in northern New ^Mexico and Colorado J. scopulorum is fre- 

 quent, and in California J. califoniica is important. 



The oaks are more important in the southern part of the range and 

 are mostly evergreen oaks such as Quercus reticulata and Q. hijpo- 



FlG 



111.— A very sparse pinyon-juniper woodlan 



Monument, Utah. 



(.'apit(jl 



National 



leuca and, in California, Q. douglasii and Q. icislizeni. In some 

 places the oaks are present to the exclusion of one of the other genera, 

 thus making an oak-juniper or a pine-oak community, but the most 

 typical connnunity is a pinyon pine-juniper association. 



147. Grassland Communities.— The grassland formation is the 

 most extensive type of vegetation in the United States. It occupies 

 nearly all of the central portion of the country from the deciduous 

 forests of the east to the foothills of the Rocky ]\Iountains on the 

 west, extending northward into Canada and southward into Mexico. 

 It also occurs, intermittently and in various modifications, westward 

 to the Pacific coast. 



