84 MISC. PUBLICATION 9 0, U. S. DEPT. OF AGRICULTURE 



Diameters over 30 inches breast high are unusual, and the tree seldom 

 reaches a height of more than 100 feet. 



Fire resistance. — Young Douglas fir is almost sure to be killed 

 by any fire which burns through the stand, because of its thin bark, 

 dense stand, and inflammable foliage. After becoming mature, 

 Douglas fir suffers less on account of the heavier bark, but remains 

 more liable to damage than western yellow pine. 



Characteristics of the wood. — The wood is strong, hard, durable, 

 coarse, and knotty. It holds nails well and is valuable for ties, mine 

 timbers, poles, and lumber, especially dimension material. 



Commercial importance. — Because of its relative accessibility, 

 much Douglas fir was cut by the pioneers in Utah". It is still one 

 of the most important timber trees of the State, being extensively 

 used for mine props, railroad ties, farm timbers, and lumber. 



The most important broadleaf tree in Utah is aspen (Populus 

 tremuloides) , of which there is believed to be 6,000,000 cords in the 

 State. 



Occurrence. — In Utah aspen is very generally distributed, being 

 found at elevations between 7,000 and 10,500 feet on all the national 

 forests in the State. It forms the most extensive stands and attains 

 its largest size in the mountains of central Utah and western 

 Colorado. 



Requirements. — Aspen is not very selective as to soils, being found 

 on all kinds from loamy sand to heavy clays. It does best, however, 

 on a deep soil and requires considerable moisture. 



Reproduction. — At present, there is practically no reproduction of 

 aspen by seed in Utah. It is believed that in geological times when 

 the climate of this region was more favorable, aspen became generally 

 distributed through the forests by seed. Then as conditions became 

 less favorable to germination, reproduction by seed was reduced 

 until now it has been almost entirely replaced by suckering from the 

 roots. As a result, aspen stands extend themselves very slowly. 

 Roots sprout vigorously at all ages up to 110 years. 



Groivth and yield. — Aspen has a variable development in the 

 Rocky Mountain region, from a low twisted shrub to trees that reach 

 a diameter of 38 inches at breastheight and a height of 90 feet. In 

 general it ranges from 8 to 11 inches in breast-high diameter and 

 from 50 to 60 feet in height. Most of the large aspen trees seen in 

 the mountains of Utah are over 100 years old, and specimens 200 

 years old have been found. 



Fire resistance. — A very light fire will kill aspen, as the bark is 

 thin and green, with no protecting corky layers. Scars which lead 

 to heart rot will be made on the large trees by the lightest fires. 

 The aspen leaf fall and litter are too scant to carry fire readily, and 

 since the accumulation of dry grass and weeds has been prevented by 

 grazing there have been almost no fires in the aspen stands of Utah. 



Characteristics of the wood. — The wood of aspen is straight 

 grained, of smooth texture, white in color, and light when dry. The 

 green wood contains a large percentage of moisture, losing almost 

 50 per cent in weight when kiln-dried. 



