INCENSE CEDAR. 21 



A gradual increase in elevation from north to south is apparent, 

 ranging from between 1,100 and 5,000 feet at its northern limits to 

 between 4,000 and 9,000 feet at its southern. Similarly a rise is 

 noticeable from west to east, the limit in the coast ranges being 1,100 

 and 5,000 feet, on the west slope of the Sierras 3,000 and 7,000 feet, 

 and in western Nevada 5,800 and 7,000 feet. 



SILVICAL REQUIREMENTS. 



MOISTURE. 



The minimum water requirement of incense cedar is low compared 

 with other commercial timbers, as is shown by its frequent occur- 

 rence on dry, exposed ridges and at the extreme lower limits of 

 commercial tree growth. It does best,. however, where the supply of 

 soil moisture is fairly abundant. In its drought-resisting qualities 

 it is second only to western yellow pine among the commercially 

 important species of its range ; but extreme drought serves effectually 

 to shut it out and, more than any other factor, prevents it from 

 spreading to lower elevations. Excessive moisture, on the other 

 hand, is equally effective in limiting its range. Hence we do not find 

 it encroaching on wet mountain meadows or extending any great 

 distance into the regions of excessive precipitation of the Pacific 

 Northwest. 



Soil moisture and humidity complement each other to a certain 

 extent, it being possible for an abundance of one to make up partially 

 for a lack of the other. Where soil moisture is sufficiently abundant, 

 however, incense cedar will grow in an almost arid climate, showing 

 that no great amount of humidity is essential. 



Incense cedar is a shade-enduring tree and reaches its best develop- 

 ment in fairly dense stands. It is surpassed in tolerance only by 

 white fir and possibly, in northern California and southern Oregon., 

 by Douglas fir. The reluctance with which it sheds its lower limbs 

 is an indication of this extreme tolerance. To kill out incense cedar 

 by shading is almost impossible, though, of course, too much shade 

 hinders growth, and an abundance of light, if other conditions are 

 favorable, helps it. 



TEMPERATURE. 



Temperature is undoubtedly an important factor in the distribu- 

 tion of incense cedar, particularly in limiting its range at the higher 

 elevations. The extreme cold, combined with the short growing sea- 

 son, is probably responsible more than any other factor for ex- 



