1936] MAMMALS AND LIFE ZONES OF OREGON 13 



slopes a far greater number of Transition Zone species generally 

 occur. Those most conspicuously indicating Upper Sonoran are sev- 

 eral species of CeanotJyus (cuneatus, integerrimus, sanguinem) , man- 

 zanita (Arctostaphylos viseida), bitterbush (Purshia Pridentata) , 

 birch-leaved mahogany (Cercocarpus "betulaefolius), syringa (Phila- 

 delphia gordonianus) , cherry (Prunm subcordata), silktassel-bush 

 (Garry a fremonti), skunk bush (Rhus trilobata and diversiloba) , 

 serviceberry (Amelanchier florida and pallida), lupines (Lupinus 

 ore g 'onus pusttlus and subsericeus) , wild licorice (Glycyrrhiza lepi- 

 dota and glutinosa), Hosackia (Lotus), several species, rabbitbrush 

 (Chrysothamnus nauseosus) , and a great number of grasses and her- 

 baceous plants. A few of these species extend northward into the 

 Williamette Valley, indicating an approach in climate to the Upper 

 Sonoran Zone, but not in sufficient numbers of species or abundance 

 of individuals to warrant mapping even the warm slopes of the 

 valley as other than Transition. 



In the Columbia River Valley east of the Cascades the climate is 

 slightly warmer and more humid, with greater rainfall in winter, 

 than over the Great Basin area farther south and east. Consequently 

 the fauna and flora are somewhat peculiar, as shown by the follow- 

 ing species: Townsend's ground squirrel, northwest pocket mouse, 

 Dalles and Columbia pocket gophers, Scheffer's mole, and little 

 canyon bat. There is generally a greater abundance of grass with 

 a considerable number of other plants not found over the rest of 

 the zone in eastern Oregon. Certain crops are also raised follow- 

 ing the winter rainy season, without irrigation but through dry- 

 farming methods and careful tillage. 



As a new country becomes settled and the best of the land is 

 brought under cultivation, the native species of plants and animals 

 are eradicated or supplanted by those introduced from other coun- 

 tries, and even the stock range is so overgrazed as to destroy much of 

 the original type of vegetation. It becomes increasingly more diffi- 

 cult to define the life zones. But fortunately over most of Oregon 

 there is still sufficient native life to give a good index to long-estab- 

 lished climatic conditions. 



The practical value of this knowledge of life zones becomes 

 apparent when a new valley, plain, or slope is brought under culti- 

 vation and the question arises as to crops, fruit, or stock best adapted 

 to its climate. In long-cultivated valleys these questions generally 

 have been answered, although often by costly failures. Now expe- 

 rience shows that the successful products of one valley may be safely 

 extended into another having satisfactory indications of the same or 

 closely similar native fauna and flora. In other words the study 

 and careful mapping of life zones gives a practical aid to agricul- 

 ture as well as a guide to management of wildlife resources. 



It would not be wise to try to restock the desert ranges of eastern 

 Oregon, once inhabited by the rimrock mountain sheep, with 

 Canadian Zone animals from the high Rocky Mountains, but any of 

 the Upper Sonoran desert forms from Nevada, southern California 

 or Arizona would thrive on these low ranges and canyon walls. 

 Restocking and building up a depleted game supply will require 

 careful consideration of life-zone conditions. 



