3 « 
The Colorado Experiment Station 
Fig. 11.—Distribution of sagebrush (Artemisia tridentata) shrub- 
steppe in Colorado. 
whole Great Basin area. Fig. 11 gives the general distribution of 
sagebrush in Colorado. It is seen to occupy much of western 
Colorado, North Park and Middle Park. In narrow valleys, it is 
on the narrow benches bordering the streams (Fig. 12). It may 
also clothe rounded hills to their summit. The most typical sage¬ 
brush territory in Colorado is in the northwest counties. It grows 
to an altitude of 10,000 feet in some localities, but as a plant for¬ 
mation it reaches its best development below 9,000 feet. Com¬ 
petition, not temperature, seems to be the limiting factor in its 
upper altitudinal distribution. Where precipitation and topog¬ 
raphic conditions are such as to permit the growth of trees, sage¬ 
brush is at a disadvantage. In North Park and Middle Park sage¬ 
brush and lodgepole pine forest meet, and the boundary line is 
sharp. Again, it may form a sharp boundary line with the yellow 
pine, or aspen, or oak brush, or pinyon pine and juniper. But, in 
nearly all of these cases, factors other than temperature are deter¬ 
minative. 
Types of shrub-steppe that are second in importance only to 
sagebrush are the greasewood and rabbitbrush associations, which 
cover the larger part of San Fuis Valley, and more limited areas 
in other sections of the state. Greasewood is present throughout 
