30 
The Colorado Experiment Station 
SUMMARY OF CHARACTERISTIC FEATURES OF COLORADO CLI¬ 
MATE, ESPECIALLY THOSE THAT BEAR UPON AGRICULTURE 
1. Great variation throughout the state. We have a variety 
of climates such as one would pass through in going from Vir¬ 
ginia to Greenland within the Arctic Circle. This variation neces¬ 
sitates the development of special crops, and special varieties, for 
the different climatic districts. 
2. Low precipitation in districts where temperature condi¬ 
tions are most favorable for crops, hence necessity for irrigation. 
3. Short growing season in regions with considerable precipi¬ 
tation. 
4. Extremes of heat and cold, both diurnal and annual, espe¬ 
cially on the plains, in the upland valleys, and in the western sec¬ 
tion of the state. 
5. Cool nights and warm days. 
6. Frequent late spring and early fall frosts, that is, a great 
variation from year to year in the length of the growing season. 
7. High winds which, together with low winter temperatures, 
have much to do with winter killing. 
8. Comparatively low relative humidity throughout the year, 
resulting in rapid loss of water from plant surfaces. The absence 
from Colorado of many fungous diseases is in part due to the low 
relative humidity of its atmosphere. 
9. Wide variations from the normal as regards almost all cli¬ 
matic factors. 
NATIVE VEGETATION 
Chief Native Plant Communities *.—No attempt will be made 
here to give a full discussion of all the native plant communities 
in Colorado. Only those that cover large areas, or are in the main 
climatically determined, will receive attention. However, as has 
been stated, the character of a plant covering is a response to local 
as well as climatic factors, and it is difficult to distinguish the rela¬ 
tive effects of the two sets of factors. 
The following large communities of Colorado native plants, 
with their climatic and agricultural relations, are discussed : 
1. Grass-steppe or short-grassland (Great Plains). 
2. Shrub-steppe. Sagebrush, greasewood, rabbitbrush, etc. 
*The term “community” is used here in a general, unrestricted sense to include any 
aggregation of plants, such as grassland, oakbrusb chaparral, yellow pine forest, etc., 
regardless of its vegetational rank. 
