THE SILVA OF COLORADO 



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be dignified by the name of forest. Near Pawnee Buttes in northeastern 

 Colorado there are limber pines instead of rock pines. To the south, 

 and in certain parts of the western area of the state, the pinyon pine is 

 added to the rock pine and cedar. 



Classification of forests. — From a botanical standpoint forests may 

 be distinguished as mesophytic and xerophytic. The former are those 

 made up of trees requiring a moderate amount of moisture, the latter 

 are dry-country forests capable of enduring drought; they occur in 

 regions of slight rainfall or in situations where the run-off is rapid. 

 Mesophytic trees in Colorado are confined to areas where there is con- 

 siderable seepage water, except in the case of Engelmann spruces in the 

 sub-alpine zone where there is much more rainfall than at lower altitudes. 



It may be convenient to list the principal forest formations of Colo- 

 rado in tabular form. 



♦ The pinyon pine is found only in the warmer and drier parts of the state 

 enter into the foothill forest formation in certain places. They are entirely 

 of Denver. » 



Oaks, chiefly shrubby species, 

 absent from the foothills north 



