VOLUME LVIII 



NUMBER 5 



THE 



Botanical Gazette 



NOVEMBER 19 14 



AIRIE VEGETATION OF A MOUNTAIN-FRONT AREA 



IN COLORADO 



Arthur G. Vestal 



(with nine figures) 



This account is based on a study, during the past three seasons, 

 )lant associations in the Great Plains region and of their modi- 



mountain 



climatic 



physiographic, and vegetational differences which are of influence 

 immediately adjoining the foothills, and to a less degree within « 



eastward for several miles from the moun 



"mesa" belt extending 



tains. The study was carried on chiefly in the neighborhood 

 of Boulder, Colorado. The area under particular consideration 

 may be seen in the map (fig. i). The mesas at Colorado Springs, 

 slightly more arid than those at Boulder, have been studied by 

 Shantz (17). A mountain-front area in New Mexico has recently 

 been described by Watson (20). Vegetation of the open plains 



ND 



by Shantz (18). 



The region 



The structure of the Great Plains is well described by Johnson 

 (10, especially pp. 627, 628). They are essentially a structural 

 rock slope, covered by debris from the Rocky Mountains. Near 

 the mountains the debris apron is a mixture of rock fragments of 

 all sizes; it has been removed in places by erosion, exposing 

 the shales or sandstones beneath, with their residual soils. The 



377 



