REMARKS ON SOME NORTHERN COLORADO 



PLANT COMMUNITIES WITH SPECIAL 



REFERENCE TO BOULDER PARK 



(TOLLAND, COLORADO) 1 



By Francis Ramaley 



Classification of Plant Communities. — The term community is 

 applied to an assemblage of plants occupying some definite area. If the 

 area thus covered be of wide extent the community is known as a forma- 

 tion. Communities of smaller area, or perhaps characterized by certain 

 dominant species, are called associations. Thus in the foothill region of 

 northern Colorado there is a coniferous forest formation made up of rock 

 pines and Douglas spruces : the former in drier places, the latter occupy- 

 ing shaded areas where there is more moisture. Here then the conif- 

 erous forest formation of the foothills embraces a rock pine association 

 and a Douglas spruce association. In like manner a thicket formation 

 may embrace an alder association, a willow association, etc. In the 

 grassland formation of our plains area there may be distinguished a 

 grama grass association, buffalo grass association and others. 



Within the limits of an association subsidiary groups of vegetation are 

 known as societies. Assemblages of mountain daisies {Erigeron) form 

 Erigeron societies in the Bouteloua association of the plains grassland 

 formation. 



Formations may well be given names which indicate at once the 

 general character of the vegetation, as: streamside deciduous forest 

 formation, plains grassland formation, alpine fell-field formation, etc. 

 On the other hand, it is customary to name associations and societies 

 for one or more species which are dominant and give character to the 

 community: limber pine association, Trifolium society, Elymus con- 

 densatus society. 



Somewhat at variance with the systematic classification here outlined 

 is the general American usage according to which almost any assemblage 



1 Adapted with certain changes from notes of a course of four lectures given at the University of Colo- 

 rado Mountain Laboratory at Tolland, Colo., in July, 1909. 



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