luJ 



CHAPTER II \. 



Life Zones of the Carlsbad Region 



Climatic conditions are reflected in the native plant 

 and animal life of any region, not only in the dominance 

 of peculiar species and the development of such charac- 

 teristics as best served the plants and animals in their 

 habitat, but in the absence of species developed under 

 different climatic conditions. An occasional hot or 

 cold, wet or dry, year usually has little effect, as the 

 local plant and animal life is the product and the index 

 of average climatic conditions over a long period of time. 



The life of the Tropics is strikingly different from that 

 of the Temperate zones, as is the life of these zones from 

 that of the Arctic zone, but the humid and arid Tropics 

 are also widely different in fauna and flora. Likewise, 

 in the several well recognized transcontinental life 

 zones between the Tropics and the Arctic there are many 

 subdivisions based on the effects of peculiarities of 

 climate, mainly of different degrees of humidity. The 

 broad zones of similar climatic conditions extending 

 across the continent have a fundamental basis of tem- 

 perature, as has been shown by numerous authors since 

 the time of Humboldt. However, the details of varia- 

 tion have been only partially determined by recent in- 

 vestigations in the field, and by actually mapping the 

 geographic distribution of many species of plants and 

 animals. In New Mexico and Texas this has been 

 done in considerable detail and the life zones and their 



