10 LIFE ZONES 



ditions determine the kinds and quantities of cultivated plants 

 that will grow in such areas, and thus regulate to a marked 

 degree the activities of men in the region. 



Since the grazing industry is almost wholly dependent, 

 as yet, on the natural distribution of the plants of the State, 

 and since man can regulate this distribution little or none 

 by any artificial means, these natural life zones are of par- 

 ticular interest and importance to stockmen. 



A large amount of work has been done by the 

 investigators of the Bureau of Biological Survey, United 

 States Department of Agriculture, on the Life Zones of New 

 Mexico and they have prepared a map outlining the.se zones, 

 which will be published in a short time. Through the 

 kindness of the chief of this Bureau. Dr. H. W. Henshaw, we 

 are permitted to print a reduced and rough copy of this map 

 which will give some general idea of the areas included in 

 each zone in the State. We use the names for the zones now 

 generally used in American pul^Iications on the subject, and 

 append lists of some of the most characteristic plants of each 

 zone. In all comparisons with zones of the humid region the 

 reader must remember that New Mexico is all above 3500 

 feet altitude and that the air is correspondingly thin, as the 

 result of altitude, and is also vcr\- dry nearly all the time. 

 These two conditions materiallv inflncnce the climate by their 

 effect ui)on radiation, and in consequence the daily variation 

 of temperature is always and everywhere very large. This 

 makes tlie mean tem])crature th.- average of a high maximum 

 and a low minimum, and since the extreme temperatures are 

 of much more importance in governing plant distribution 

 than the mean, the arid zone equivalents do not exactly 

 correspond with those of similar name in the humid regions. 

 There are a numb-.r of other factors entering into the problem 

 which need not be mentioned here. 



Commencing at the southern end of the State in the 

 lowest valleys and following northward and upward, we 



