CYPEESS AND JUNIPER TREES OF ROCKY MOUNTAIN REGION. 17 



OCCURRENCE AND HABITS. 



Western juniper grows on exposed high mountain slopes and sides 

 of canyons, in dry gravelly and rocky soils, and sometimes in crevices 

 of bare rocks. In the Rockies 1 it is found generally at elevations 

 between 2,000 and 9,000 feet, though most often between 6,000 to 

 8,000 feet, where the best growth occurs. It usually forms very 

 open but practically pure stands, and is sometimes scattered 

 among other trees of its high range. As a rule, pure stands are 

 limited to from a few to 40 or 50 acres. Western juniper is fores trally 

 important because it thrives at high elevations, in dry wind-swept 

 situations, where few other trees can exist. It always grows in the 

 full enjoyment of light, and appears to be decidedly intolerant of 

 shade. Even seedlings in partial shade are much less vigorous than 

 young plants growing in full light. 



Western juniper produces its fruit abundantly, yet the seedlings 

 are always much scattered and occur only in pure mineral soil. 

 As in the case of other junipers many of the berries are eaten by 

 birds, which assists in distributing the seed; but very tardy germina- 

 tion of the seed under the particularly unfavorable conditions within 

 the tree's habitat, as well as the fact that seedlings can not grow in 

 better soil under the shade of other trees, probably accounts for the 

 sparse reproduction. 



LONGEVITY. 



While the extreme age this tree may attain is not yet fully deter- 

 mined, it is known to be exceedingly long-lived. Both height and 

 diameter growth are slow when the tree is rooted in crevices of rock 

 and exposed, as it usually is, to fierce winds. Even in such situa- 

 tions, however, it grows persistently, producing a trunk that is out 

 of all proportion in thickness to its height. The wood of such trees 

 is very narrow-ringed (one-sixth to one-tenth of an inch), indicating 

 great age. In protected mountain coves and on flats with deep 

 washes of loose earth, diameter growth is more rapid and the annual 

 rings wider. Trees of this type, from 20 to 48 inches in diameter, 

 are from 125 to 300 years old, while in general the age of full-grown 

 trees is estimated to be between 500 and 700 years. The largest 

 trees grown in exposed places are probably from 800 to 1,000 or more 

 years old. 



1 Elsewhere in its range this juniper has a widely varying vertical distribution from 600 to about 10,500 

 feet, the highest elevation attained being in the California Sierras. Its commonest occurrence there is 

 at elevations between 6,000 and 9,000 feet. 



84703°— Bull. 207—15 2 



