CONIFERS OF THE ROCKY MOUNTAIN REGION. 31 



cedar (Thuja plicata). It is locally used for several of the same 

 purposes for which the latter is employed, such as fence posts, tele- 

 phone poles, light-traffic railway ties, shingles and shakes, sash and 

 doors, and "edge-grain" flooring, and some other interior finishing 

 material. Its soft, brittle texture and the ease with which it "chips" 

 has also recently brought this wood into use for cheap grades of 

 lead pencils. 



OCCURRENCE AND HABITS. 



Libocedrus decurrens occurs more commonly, as a rule, on western 

 than on eastern mountain slopes. It ascends somewhat higher on 

 the western slopes, chiefly because of greater moisture on such 

 exposures. The vertical range of incense cedar in the Pacific slope 

 region varies from about 3,500 to 7,500 feet, in exceptional instances 

 descending as low as 1,500 feet and ascending to about 9,000 feet 

 elevation. In its dry range within the Rocky Mountain region it is 

 confined mainly to canyons, gulches, and cool north slopes, at an 

 altitude of about 7,000 feet (Map No. 7). Incense cedar is adapted 

 to a variety of soils, but grows best in cool, moist, gravelly, porous 

 soils. It occurs also in rather dry soils (warm exposures), yet 

 probably only because it can endure them. With deficient soil 

 moisture, fairly deep, porous soils are essential, while with sufficient 

 moisture the quantity and quality of soil is less important. 



In the Pacific slope region incense cedar occurs variously in mixture 

 (but more or less subordinate), scattered singly, or in groups and 

 patches, mainly with western yellow pine, Jeffrey pine, Douglas fir, 

 white fir, red fir, California black oak, and sometimes with bigtree. 

 Under the best conditions for growth in this region it occasionally 

 forms from 25 to 50 per cent of the stand, particularly within the 

 range of western yellow pine and sugar pine. But in its limited range 

 in the Rocky Mountain region incense cedar forms only a very small 

 percentage of the stand and occurs mostly with western yellow pine. 



Incense cedar is moderately tolerant, enduring more shade than 

 western yellow pine, western white pine, and Douglas fir, and is 

 usually intermediate or subordinate in mature stands because of its 

 slower growth and greater tolerance. It is adapted both to moderate 

 shade and full light, but requires less light in youth than in later life 

 and tolerates most shade under conditions favorable to good growth. 

 Its tolerance varies, however, not only with age, but also with 

 atmospheric and soil moisture, character of soil, and climate. Rapid- 

 ity of growth and size attained in later life are checked ordinarily 

 n proportion to the intensity of shade to be endured. 



Incense cedar is a prolific seeder every two or three years under 

 favorable conditions of growth, some seed, however, being borne 

 locally about every year. Thrifty, mature trees standing in full 



