12 American Midland Naturalist Monograph No. 4 



pole pine {Pinus contorta) is common on the flats and moraines up to about 

 8,000 feet with very little undergrowth. Extensive areas are covered with 

 alpine fir {Abies lasiocarpa) and Engelmann spruce (Picea Engelmanni) , 

 which extend up to timberline. Whitebark pine (Pmus albicaults) is often 

 an associate, especially in the upper part of the range. Douglas fir (Pseudot- 

 sugd taxijolia) occurs in many places, generally in association with alpine 

 fir and Engelmann spruce, or sometimes in open stands on rocky southern 

 exposures. 



Shrub species characteristic of the fir and spruce forests are very similar 

 to those found in Yellowstone National Park. Among them may be listed 

 myrtle pachistima (Pachistima myr smites), rusty menziesia (Menziesia fer- 

 ruginea) , creeping hollygrape (Mahonia repens) , bearberry honeysuckle 

 {Lonicera involucrata) , russet buffaloberry (Shepherdia canadensis), service- 

 berry (Ainelanchier alntfolia), mountain ash {Sorbus scopulina), and wild 

 currants and gooseberries (Ribes species). In forest openings and on open 

 slopes are found western thimbleberry (Rubus parviflorus) , snowbrush ceano- 

 thus (Ceanothus velutinus), black chokecherry {Primus virginiana var. mel- 

 anocarpa), and sagebrush (Artemisia tridentata and var. arbuscida) . Several 

 species of Salix are common along streams in valley bottoms and thinleaf 

 alder (Alnus tenuifolia) on moist hillsides. 



Aspen (Popidus tremuloides) is abundant at the lower elevations, often 

 forming pure stands in moist locations. Higher up on dry open slopes it 

 is also common, sometimes forming dense thickets. Here, however, it tends 

 to become dwarfed and shrubby. Narrowleaf cottonwood {Popidus angusti- 

 folia) is found occasionally along the eastern boundary and balsam poplar 

 {Populus balsamifera) occurs in a few localities. 



The trees at high elevations become much dwarfed and scattered, some- 

 times forming mats or carpets on exposed ridges at timberline. In these 

 subalpine areas characteristic shrub species are subalpine spiraea {Spiraea 

 densiflora), Rocky Mountain whortleberry {Vaccinium oreophilum) , and 

 shrubby willows. Numerous herbaceous species are found here as well as in 

 the alpine meadows above timberline. Low alpine shrubby plants include 

 red mountainheath {Phyllodoce empetrijorryiis), skyland willow {Salix petro- 

 phila), mountain bog Kalmia {Kalmia polifolia var. microphylla), and 

 Mount Washington dryad {Dryas octopetala) . 



Rocky Mountain National Park 



Rocky Mountain National Park in north central Colorado is located in 

 the southern province of the Rocky Mountain Region. The park lies along 

 the Continental Divide at relatively high elevations, from about 7,600 feet 

 at the east entrance to 14,255 feet at the top of Long's Peak. Yearly rainfall 

 averages 19 inches at Estes Park on the east side and 16 inches at Grand 

 Lake at about 8,300 feet on the west side. A fine motor highway crosses the 

 Continental Divide at an elevation of over 12,000 feet which affords the 

 traveller an opportunity to observe without undue effort the changes in vege- 

 tation in passing through several different Life Zones. 



