4 BULLETIN 426, U. S. DEPARTMENT OF AGRICULTURE. 



graceful dov/nward sweep to the limb. Even in this position they 

 can not escape the squirrels that depend on the rich-flavored seed 

 for a winter food supply and cut la.rge numbers before maturity. 



SIZE AND LONGEVITY. 



Sugar pine attains a greater size than yellow pine, white fir, incense 

 cedar, or any of its associates, except the huge Sequoias of the 

 Sierras, which tower far above it in the scattered localities where 

 the two species occur together. Its average maximum height is 175 

 feet and the corresponding diameter 4^ feet. The maximum height 

 reached is 240 feet and the maximum diameter 11 feet, measured 

 outside the bark at 4^ feet above the ground. The average number 

 of logs per thousand feet board measure, ascertained from sales of 

 National Forest stumpage, varies from 4 in unfavorable situations to 

 1,5 in the best localities. This species attains an a^ge of 500 years, 

 but rarely more than that. 



SUSCEPTIBILITY TO INJURY AND DISEASE. 



Various injuries tend to shorten the life of sugar pine, but none 

 result in the immediate death of a high percentage of mature stands 

 except those caused by destructive insects. 



FIRE. 



Repeated fires cause butt scars or "cat faces," and thus weaken 

 the tree mechanically, retard growth, and bring about conditions 

 favorable to disease. Such scars also decrease the value of butt 

 logs. Seedlings, saplings, and poles are destroyed in large numbers, 

 but very few trees over 12 inches in diameter at breast height are 

 killed, except on steep slopes during very high winds. 



LIGHTNING, WIND, FROST, AND SNOW. 



Sugar pine undoubtedly is injured more frequently by lightning 

 than its associated species, yellow pine, fir, and incense cedar, because 

 of its greater height and occurrence at relatively high elevations, 

 where such storms are common ; but because of the brief season dur- 

 ing which lightning storms are prevalent, and their local character, 

 the aggregate amount of damage wrought is not serious. Insects 

 almost invariably attack lightning-damaged trees and complete the 

 destruction, when the wound in itself would not prove fatal. 



The strong, widespreading, lateral root system and the thick, 

 sturdy bole of this tree resist winds of extraordinary velocity. Some- 

 times weakened trees in exposed situations yield to exceptionally 

 severe storms. Large trees are subject to a mechanical defect known 

 as windshake, the result of stresses in the butt section caused by 

 severe wind in conjunction with low temperature. Circular seams 

 are opened up and the value of the trees for lumber is lowered. 



