IMPORTANT RANGE PLANTS.' ' 3 



1 . A Transition zone or yellow-pine ass6ciation' occupying tlie 

 country between 3,000 and 4,500 feet elevation. 



2. A Canadian zone or lodgepole-pine association between 4,500 

 and 6,800 feet elevation. 



3. A Hudsonian zone or white-bark pine association between 

 6,500 and 8,500 feet elevation. 



4. An Arctic-alpine zone or alpine-meadow association from 

 8,000 feet elevation up. 



Owing to the wide difference in the physical conditions in these 

 zones, numerous rather distinct range types occur. The tune 

 during which each is grazed varies according to the location. 



The Transition zone (yellow-pine association), owing to the open 

 character of the tree stand, supports a rather dense grass cover. 

 Big bunchgrass (Agropyron spicatum) occurs in pure stands on the 

 less elevated lands, and pine grass (Calamagrostis suksdorfii), blue 

 bunchgrass (Festuca idahoensis), little bluegrass (Poa sandbergii), and 

 mountain June grass (Koeleria cristata), named in the order of their 

 importance, are the most valuable species at somewhat higher 

 elevations. The majority of the important species are herbaceous. 

 This zone is among the first to be grazed in the spring, the lower 

 lands usually supporting stock early in March. By June 1 the forage 

 in the higher adjoining lands is preferred because of its greater 

 succulence. 



The Canadian zone (lodgepole-pine association) is more densely 

 forested than the others. Also the forage, instead of being herbace- 

 ous, is mainly shrubby or of the ki chaparral" type. The most im- 

 portant browse plants in this zone are fire willow (Salix nuttallii), 

 black elder (Sambu-cus melanocarpa), high huckleberry (Vaccinium 

 membra naceum), and wax currant (Ribes cereum). Since the physical 

 conditions in the Canadian zone are intermediate between those of 

 the Transition zone below and the Hudsonian zone above, few plants 

 are wholly confined to this region, and many of the species of the 

 transition zone are encountered here. The grazing period in the 

 Canadian zone comes approximately between May 15 and July 15. 



The Hudsonian zone (white-bark pine association) is characterized 

 by scattered small clumps of woodland and a preponderance of 

 grassland. The most important forage species are mountain bunch- 

 grass (Festuca viridula), onion grass (Melica ~bella), porcupine grass 

 (Stipa occidentals), wild celery (Ligusticvm oreganum), and butter- 

 weed (Senedotriangularis). 



While this region is not suited for early grazing, because of the 

 lateness of the growing season, it has as great an area and carries 

 about as many stock as both of the lower zones together. It includes 

 all the high summer sheep lands, except the few crests that are 

 grazed above timber line. The grazing period begins approximately 

 July 15 and continues through August and September. 



