CYPRESS AND JUNIPER TREES OF ROCKY MOUNTAIN REGION. 35 



tains, however, have not been determined. In its Mexican range 

 drooping juniper is said to grow at elevations between 6,000 and 

 8,000 feet. In the Chisos Mountains it occurs in small groups or as 

 scattered trees, commonly associated with alligator juniper, Mexican 

 pinon, Texas oak, Mexican mulberry, and Texas madrone. Within 

 its vertical range are found Rocky Mountain scrub oak, Emory oak, 

 western yellow pine, one-seed juniper, stunted Douglas fir, Arizona 

 cypress, and Texas ash. 



Drooping juniper bears fruit abundantly, especially when growing 

 on open slopes. Some berries are produced practically every year, 

 and especially large crops are borne at intervals of from two to three 

 years. Reproduction is sparse on dry, rocky slopes, but abundant in 

 moist canyon bottoms and on deep-soiled benches. The seed is 

 probably not disseminated to any extent by birds, as in the case of 

 some of the other junipers, because the berries are dry and unpalat- 

 able. The relatively small number of perfect seeds in each berry 

 also account for the slow reproduction of this tree. 



Seedlings and young trees grow thriftily in dense shade. Pole- 

 size trees can maintain themselves almost indefinitely under such 

 conditions, though their growth is exceedingly slow. The crowns 

 of shaded trees are much thinner and the foliage less robust than in 

 the case of trees enjoying full light. Dense side shade and moderate 

 top light produce the tallest and clearest trunks, with open crowns. 

 Full sunlight gives short trees, with little or no clear trunk and very 

 dense crowns. 



LONGEVITY. 



Drooping juniper gives evidence of being a very long-lived tree. 

 So far, however, it has been possible for the writer to determine the 

 age of only one tree, 5 inches in diameter at the collar, which was 

 approximately 200 years old. During the first 150 years of its life, 

 this tree appears to have grown in dense shade. During the last 

 50 years its crown seems to have received direct light, and in this 

 period its growth nearly equaled that of the previous century and a 

 half. The largest trees (from 14 to 20 inches in diameter) so far 

 found in the Chisos Mountains are growing under somewhat more 

 favorable conditions of light, so that they are probably between 400 

 and 500 years old. 



