1936] MAMMALS AND LIFE ZONES OF OREGON 29 



much more limited list of species. For flora it can show only two 

 tree species in sheltered gulches, aspen and balsam poplar, some 

 willows along the streams, and considerable other shrubby vegetation 

 of the Blue Mountain or Rocky Mountain types. 



HUDSONIAN ZONE 



Hudsonian Zone is the narrow timber-line belt just below the 

 permanent snow and ice fields of the higher peaks of the State. In 

 vertical width it is seldom over 1,000 feet and on the steep upper 

 slopes where found is at most but a narrow belt with a limited number 

 of characteristic forms of life. It varies considerably in altitude on 

 different peaks and ranges, conforming to the other zones in the 

 influence of high or low base level. 



On Mount Hood it ranges from about 5,000 to 6,000 feet on cold 

 slopes and 6,000 to 7,000 on warm slopes; on Jefferson 5,500 to 6,500 

 on cold and 6,500 to 7,500 on warm slopes; on Three Sisters from 

 6,000 to 7,000 on cold and 7,000 to 8,000 on warm slopes; on Mount 

 McLoughlin (Pitt) from approximately 7,000 to 8,000 all the way 

 around; in the Blue Mountains from 7,000 to 8,000 on cold and 8,000 

 to 9,000 on warm slopes ; and in the Steens Mountains about 7,500 to 

 8,500 on cold, and 8,500 to 9,354 feet on warm slopes but with poorly 

 defined limits. Thus a difference of 2,000 feet in the level of the 

 zone on corresponding slopes, shown in the State, is traceable to a 

 still greater difference in elevation of base level. 



PLANTS 



The plants of Hudsonian Zone, in spite of its scattered sections, 

 are more nearly the same throughout the State than are those of the 

 lower zones. Throughout the Cascades the species are largely the 

 same around all of the peaks high enough to afford the Hudsonian 

 climatic conditions. In the Blue Mountain section- the Hudsonian 

 species differ somewhat in showing a close affinity with the Rocky 

 Mountain flora, and in the Steens Mountains the greater aridity cuts 

 out all trees and many of the shrubs from the zone list. 



In the Cascades the characteristic species of the zone are the white- 

 stemmed pine, alpine hemlock, alpine larch, alpine fir, alpine 

 juniper, alpine mountain-ash, pink heather, white heather, little 

 wintergreens (CrOMltheriaovata and humifusa), little blueberry (Vac- 

 cinium scoparium) , LutTcea pectinata, wild currant (Ribes howellii), 

 creeping dewberry, white rhododendron, red monkeyflower, smooth 

 alum root, mountain lily (Erytkronium montanum), louse- wort 

 (Pedicularis surrecta), grass of Parnassus, stonecrop (Sedwrn 

 divergens), and twisted polygonum. 



In the Blue Mountains around the Wallowa and Baker _ 

 peaks the characteristic Hudsonian Zone plants include all of the 

 timber-line trees of the Cascades, a part of the shrubs and smaller 

 plants, and in addition a considerable number of Rocky Mountain 

 species, such as Ledwn glandulosum, Lonicera utahensis, Ribes lacus- 

 tre (molle?), Dasiophora fruticosa, Erytkronium parviflorum, Clay- 

 tonia lanceolata, Hoorebekia greenei, Ligmticum leibergi, Merathropta 

 intermedia, Gilia nuttallii, Epilobiwn fastigiatum and homemannii. 



