NATURAL AREAS AND REGIONS 



525 



is chiefly scrub oak. On the Western 

 Slope the sagebrush plains are separated 

 from the foothill forests by a scrub 

 growth of oaks and buckbrush (Sym- 

 phoricarpos) . 



The lower foothills of the eastern 

 slope are dominated from an altitude 

 of 6000 to 8000 ft. by a more or less open 

 forest of rock pine, with Douglas fir 

 replacing the pine on moist, cool slopes. 

 Along streams in the canyons there is a 

 mixed growth of narrowleaf cottonwood, 

 willow, boxelder, thornapple, wild plum, 

 and chokecherry. The chief mammals 

 of the foothill zone are the white-tailed 

 deer (Odocoileus virginianus macrourus), 

 chipmunk (Eutamias sp.), rock squirrel 

 (Otospermophilus grammurus), yellow- 

 haired porcupine (Erethizon epixan- 

 thum), Rocky Mountain cottontail rab- 

 bit (Sylvilagus nuttallii pinetis), and 

 mountain coyote (Cam's lestes). Birds 

 are numerous here and in the other life 

 zones. (The reader may consult Mrs. 

 Bailey's Handbook of the Birds of the 

 Western United States or Sclater's 

 History of the Birds of Colorado. For 

 an account of the mammals, see War- 

 ren's Mammals of Colorado.) 



The Montane (Lower Mountain) Zone 

 is next above the Foothill Zone and 

 includes altitudes from about 8000 to 

 10,000 ft. The forest here is either a 

 mixture of pines, spruce, Douglas fir, 

 and aspen or it may be an almost 

 pure stand of lodgepole pine (Pinus 

 murrayana). Mammals present in this 

 zone are the beaver, various squirrels, 

 chipmunks (Eutamias spp.), yellow- 

 haired porcupine, mule deer, mountain 

 coyote, timber wolf, and red fox (Vulpes 

 macroura). The species of birds are 

 almost as numerous here as in the 

 Foothill Zone. 



The Subalpine (Upper Mountain) 

 Zone forms the highest timbered belt, 

 extending from the Montane Zone at 

 about 10,000 ft. on up to the limit of 

 timber. The principal tree is the 

 Engelmann spruce (Picea engelmanni), 

 with the alpine fir (Abies lasiocarpa), 

 lodgepole pine, and limber pine (Pinus 

 flexilis) as secondary species. Engel- 



mann spruce is found on all the higher 

 mountain ranges and isolated peaks. 

 In the drier, more windswept localities 

 the spruce is largely replaced by limber 

 pine, lodgepole pine, and the bristle- 

 cone pine (Pinus aristata). Mammals 

 present in limited number are the mule 

 deer, Fremont squirrel, mountain 

 pocket-gopher (Thomomys fossor), 

 cougar, Rocky Mountain snowshoe hare 

 (Lepus bairdii), and bighorn sheep 

 (Ovis canadensis) . 



The average elevation of timber line 

 in Colorado is 11,500 ft.; above this 

 altitude is the Alpine Zone. All of the 

 higher peaks have extensive alpine 

 meadows and boulder fields with their 

 mat and cushion plants so typical of 

 alpine regions. Nearly all the plants 

 are perennials. A common mammal is 

 the pika, or cony (Ochotona saxatilis). 

 The ptarmigan is a well-known bird. 

 Many of the common birds of moderate 

 altitudes are frequent or occasional 

 above timberline, as certain jays, moun- 

 tain bluebird, western robin, western 

 violet-green swallow, and others. 



All of western Colorado is a high 

 plateau broken by mountain ranges 

 and cut into deep gulches and canyons, 

 with high and dry mesas between. 

 Extensive areas are covered by sage- 

 brush (Artemisia tridentata), the most 

 typical sagebrush country being in the 

 northwestern counties. In parts of 

 western Colorado one may travel for 

 miles through sagebrush, then through 

 pinyon pine and cedar, then through 

 sagebrush again; these two plant com- 

 munities alternating. Common mam- 

 mals of the sagebrush are the least chip- 

 munk (Eutamias minimus), white-tailed 

 prairie-dog (Cynomys leucurus), Green 

 River pocket gopher (Thomomys ocius), 

 Colorado cottontail rabbit (Sylvilagus 

 audobonii warreni), and mountain coy- 

 ote. Because of the slight rainfall the 

 growth of timber on south slopes is 

 sparse and there is often a sharp contrast 

 in appearance between north-facing and 

 south-facing mountain sides. In west- 

 ern Colorado the life zones are not 

 clearly and sharply limited. 



