NATIVE VEGETATION AND CLIMATE OF 
COLORADO IN THEIR RELATION 
TO AGRICULTURE 
By WILFRED W. ROBBINS 
INTRODUCTION * 
A close relationship exists between climate and vegetation, 
whether vegetation in the native state or under cultivation. Each 
climatic region has its characteristic natural plant life. There are, 
also, certain crop plants best suited to every distinct climatic area. 
Colorado has a variety of climates. One may travel from the 
warm valleys of the Western Slope, or from the Great Plains, to 
the crest of the Continental Divide, and pass through as many dis¬ 
tinct climates as he would in travelling from Virginia to arctic 
Greenland. This variety is largely a result of differences in alti¬ 
tude, although range of latitude and topographic diversity are also 
responsible. The lowest point in Colorado has an elevation of 
3,386 feet, and the highest, 14,402 feet, thus giving an altitudinal 
range of 11,016 feet. The latitudinal range is 4° (37° to A\°). 
Chiefly as a consequence of the great altitudinal variation, Colo¬ 
rado has many distinct climates, each with native plants and with 
crop possibilities peculiar to it. 
Climatic and Local Environmental Factors .—It is worthy of 
mention that native plants and crop plants are subject to the same 
environmental factors. We may separate the external factors af¬ 
fecting plants into two classes: Climatic factors and local 
( edaphic ) factors. Climatic factors, such as light, temperature of 
*This bulletin is an outgrowth of a number of years of observation and study of 
the native vegetation of Colorado in its relation to climate and to agriculture. During 
the summer season of 1916, special attention was directed to this study, and an auto¬ 
mobile trip, which covered the territory shown in Fig. 1, was taken for the purpose of 
testing conclusions arrived at, and finding new relations. Little consideration is given 
to the question of the value of native plant life as an indicator of the local physical 
conditions of the environment. Such detailed study, however, is of much practical im¬ 
portance, and it is planned to engage in such a study later. But, the attempt here is 
to point out the broader relations between our large native plant associations and the 
principal climatic factors under which they are growing, and to show their relation, in 
a very general way, to Colorado agriculture. The writer realizes that a number of con¬ 
clusions herein drawn rest upon insufficient data, and therefore are subject to more or 
less modification, as further information comes to hand. Furthermore, he well knows 
that climatological data employed, in the form given us, in the interpretation of biologi¬ 
cal phenomena, although not without qualitative meaning, frequently have little quanti¬ 
tative value. 
