12 LIFE ZONES 



rdunlat''.) r.nd Mulberry (Moms microphylla) be-;i'les many 

 smaller and less conspicuous plants. The trees and shrubs 

 are mostly lestricted to the foothills and airoyo:? w?ile the 

 higher plains are usually thickly covered with grass, the most 

 characteristic species of which are Blue Grama (Bouteloiia 

 oligostachya), Galleta Grass (Hilaria jamcsii), Buffalo 

 Grass (Bulbilis dactyloides), Porcupine Grass (Stipa comata) 

 and MuJilcnbcrgia graciUima besides many other species of 

 less importance. Sagebrush {Atriplcx spp.) is also found on 

 these plains in the northern part of the State. The annual 

 precipitation in this zone is probably from 12 to 15 inches as 

 an average, and the maximum temperature approximately 90° 

 to 95° F. 



3. Transition Zone. This zone is easily 



marked at its lower limit by the lower limit 

 of the Yellow Pine (called Bull Pine in the 

 mountain regions farther north and west), (Pinus 

 brachyptera). Its upper limit is not so well marked, since 

 it gradually shades into the next zone above. The zone lies 

 wholly in the mountains and includes the lower 1000 feet or 

 so of the area timljered with large forest trees. Characteristic 

 woody plants are the Yellow Pine (Pinus bracJiyptcra), the 

 Mountain Cottonwood {Popiihis angustifolia) , several Wil- 

 lows {Salix bebbiana, S. uionticola, S. irrorata, S. lasiandra), 

 the Rocky Mountain Cedar (Sabina Scopuloriiin), Alniis 

 temiifoUa, several of the deciduous leaved Oaks (Qtiercus 

 utahc7isis, 0. ncomexicana, 0. subiuollis, 0. venustida, Q. 

 Icptophylla and Q. gunnisonii) , the Wild Hop Vine (Humidus 

 lupidiis neomexicaniis), Buffalo Berry (Lepargyrea cana- 

 densis, Virginia Creeper (Psedera vitacca), Buckthorn 

 (Rhaiunus spp.). Hawthorn (Crataegus spp.). Wild Goose- 

 berries and Currants, and many others. The grasses and 

 herbaceous plants are very numerous — the commonest of the 

 former being Colorado Bluestem (Agropyron smithii), the 

 Wheat Grasses (Agropyron spp.), some of the Rye Grasses 



