TOPOGRAPHY AND LIFE ZONES OF OREGON [37] 



douglasii douglasii), mountain beaver (^Aplodontia rufa mfa), and numerous 

 species of mice (M.icrotus) and pocket gophers (Thomomys). 



In the arid Transition Zone, great open, parklike forests of yellow pine 

 (Pinus ponderosa) cover the eastern slopes of the Cascades, the plateaus and 

 lower slopes of the Blue Mountains, and the numerous little ranges that 

 are found in the broad triangle that lies with its apex at Bend and its 

 southern base along the California boundary from Klamath Falls to east 

 of Lakeview. In this section, the Transition Zone varies from 1,000 to 

 5,000 or 6,000 feet in altitude, according to local conditions, although it 

 descends almost to sea level in the Columbia gorge. So completely is this 

 zone outlined by the yellow pine that no other plant need be mentioned 

 as characteristic. Associated with it, however, are the western tamarack 

 (Larix occidentalis*), numerous species of willow (Salix), such shrubs as 

 the low-growing species (JBerberis repens and B. nervosa) that are related to 

 the Oregon grape (B. aquifolium), bearberry or kinnikinnick {Arctosta- 

 phylos uva-ursf), snowberry {Symphoricarpus albus), bitterbush (Purshia 

 tridentatd), and a prostrate Ceanothus (C. prostratus), which grows like a 

 holly-leafed carpet beneath the yellow pine and is known as mahala-mat 

 or squawcarpet. 



In southeastern Oregon, where the rainfall is too scanty to permit tree 

 growth, the Transition Zone on the Steens Mountains and the high rough 

 country to the south and east of that range, is not well marked vege- 

 tatively. On the eastern slope of Hart Mountain, a small patch of yellow 

 pine is found; but to the east this indicator is absent and here it is difficult 

 to distinguish this zone from the sage-clad areas of the Upper Sonoran. 

 The sage (^Artemisia) is not quite so rank and grows more widely scattered 

 than in the bottoms of the Sonoran, while juniper {Juniperus^ and moun- 

 tain-mahogany (fercocarpus ledifolius) are found scattered over the slopes. 

 In this territory, Transition influence predominates up to 6,000 or 7,000 

 feet, but the boundaries are poorly denned, and the zones merge into one 

 another almost imperceptibly. Such plants as Balsamorhifa sagittata, 

 Wyethia amplexicaulis, Paeonia broivnii, Phlox rigida and P. viscida, Erigeron 

 aureus and E. poliospermus, Eriogonum ovalifolium, Gaillardia aristata, several 

 species of wild parsnip (Lomattum), Lewisia rediviva, and Pentstemon aridus 

 and P. custckii become conspicuous members of the flora at proper seasons. 



Few mammals are confined to the arid sections of the Transition Zone, 

 though the rimrock sheep (Qvis canadensis californiana) were formerly 

 present in some numbers. At present most of our remaining antelope 

 (^Antilocapra americana oregona) range in it; white-tailed jack rabbits (Lepus 

 townsendii towns endii), pygmy rabbits (^Brachylagus idahoensis), desert wood- 

 chucks (Marmota), chipmunks (Eutamias), and Oregon ground squirrels 

 (Citellus oregonus) are found; and numerous species of mice and pocket 

 gophers (Thomomys) overflow from other zones into its boundaries. 



