LIFE ZONES 



No one who has traveled long distances over the 

 earth's surface has failed to note the changes in the plant 

 life which occur as the result of change of latitude. And 

 he who has climbed high mountains has appreciated more 

 or less the changes occurring in the vegetation as he has 

 gone towards the top. If he has thought of the reasons for 

 such changes and obtained a definite idea of the conditions 

 as they exist on any high mountain, he has probably grasp- 

 ed the idea that the changes are due to that very poorly 

 defined summation of factors which we call climate, a var- 

 iable thing which is to some extent governed by latitude and 

 altitude. If his observations have been fairly accurate and 

 extensive, he has seen that the vegetation is approximately 

 in irregular belts surrounding the mountain or spread over 

 the flat country in broad uneven bands. These bands or belts 

 show close relationship to the latitude and altitude and each 

 is more or less characterized by certain groups or societies of 

 plants and animals. 



As a means of understanding the distribution of plant 

 and animal life and as a basis for the study of the factors 

 which govern this distribution, considerable work has been 

 done in mapping these larger life areas or zones and much 

 has been written on the subject. 



On account of the large variations in altitude (and to 

 a much less degree in latitude) New Mexico is not like the 

 flat states of the prairie, valley, or coastal plains regions 

 farther cast, but has areas within its borders that correspond 

 in c-limatic variation with those found in the flat country 

 ranging from the subtropical to the arctic areas. These 

 life zones are of the utmost economic importance in the State, 

 since they mark in a visible form the areas having certain 

 fairlv definite climatic conditions. And these climatic con- 



