NATURAL AREAS AND REGIONS 



561 



wood (Sarcobatus vermiculatus) and 

 shadscale (Atriplex sp.) are the domi- 

 nant species on extensive areas of alkali 

 flats in the arid valleys. A distinctly 

 halophytic association of vegetation is 

 found on the salt flats adjacent to many 

 of the salt lakes and on those extensive 

 areas in eastern Nevada which were 

 covered originally by the ancient Lake 

 Bonneville. On the coarser soils of 

 the foothills the junipers (Juniperus 

 utahensis and /. monosperma) and in 

 the central and southern part of the 

 state, pinyon (Pinus edulis and P. mono- 

 phylla) form open park-like woodlands. 

 (These types of vegetation fall within 

 the Upper Sonoran Life Zone.) 



An area of extreme desert conditions 

 is found in the southern part of the 

 state, similar to and sometimes con- 

 sidered an extension of the California 

 desert. This is characterized as a 

 small-leafed shrub desert in which the 

 creosote bush (Covillea tridentata) and 

 the sandbur (Franseria dumosd) are 

 common dominant plants over consider- 

 able areas, (Lower Sonoran Life Zone). 

 This association contains quite a num- 

 ber of deciduous shrubs and large semi- 

 succulents (Yucca brevifolia, Y. arbo- 

 rescens, and Opuntia sp.) are found 

 scattered through it. Grasses and per- 

 ennial herbs are uncommon, but short- 

 lived annuals are abundant during the 

 spring months. While no mammals 

 except the small burrowing forms occur 

 naturally in this area, reptiles are very 

 abundant. 



The higher mountains were originally 

 clothed with a coniferous forest which, 

 with certain modifications, may be 

 regarded as a southward extension of 

 the northern evergreen forest. Western 

 yellow pine (Pinus ponderosa scopulo- 

 rum) occurs limitedly on the Nevada 

 Mountains and those to the south. In 

 the northern part of the state this 

 species is replaced at similar elevations 

 by either a brush cover composed of 

 various species of shrubs or often by 

 grasslands (Transition Life Zone). The 

 next higher type altitudinally is rather 

 unique in that its composition is quite 

 different from any other common forest 



type in adjacent states. Aspen (Popu- 

 lus tremuloides) is the commonest 

 tree in the lower part of this type. 

 Occurring to some extent in mixture 

 with aspen and common at the higher 

 elevations limber pine (Pinus flexilis,) 

 and alpine fir (Abies lasiocarpa) form 

 forests which have been exploited com- 

 mercially, notably in the Jarbidge 

 Mountains. Farther south in the Ne- 

 vada Mountains Engelmann spruce 

 (Picea engelmanni) is found. Succu- 

 lent plants are confined principally to 

 the forest zone on the higher mountain 

 slopes. 



The animals and birds of the various 

 vegetative associations common on the 

 great Intermountain Plateau have been 

 listed in the Utah account. 1 The 

 writer's knowledge of the fauna of 

 Nevada is not sufficient to warrant an 

 attempt to indicate such minor differ- 

 ences as may occur. 



Many of the desert areas have been 

 used as winter range for sheep and 

 cattle which have grazed in the moun- 

 tain forests of this and other states in 

 summer. The state is much better 

 adapted to the livestock industry than 

 to farming. The grazing of livestock 

 has been practiced almost continuously 

 since the early settlement of the state 

 and has been developed to such an 

 extent that it has resulted in consider- 

 able over-grazing. On many of the 

 open ranges in the state the situation 

 is becoming acute. On the other hand, 

 remedial measures to prevent over- 

 grazing are being applied on the National 

 Forests. 2 Because of the fact that the 

 settlements and mining camps of Ne- 

 vada have, for the most part, been very 

 remote from large industrial sources of 

 supply, it was necessary for the settlers 

 to utilize the local resources. There- 

 fore, with the continued development 

 of the state and the exploitation of the 

 local resources, the natural conditions 



1 This volume, pages 557-560. 



*See "Grazing in the National Forests," this 

 volume, pages 33-34. 



The situation in Nevada is also illustrated in figs. 

 1-3, accompanying "Grazing Practice on the Na- 

 tional Forests and Its Effect of Natural Conditions," 

 by C. F. Korstian in, Scientific Monthly, 13: 275-281. 

 1921. 



