LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 25 



poles to the ground or breaks them off at a height of from 10 to 

 20 feet. Snow-break may be beneficial in overdense stands which 

 are in need of thinning, but may also do considerable damage in 

 thinned stands where the individual trees can no longer rely on their 

 neighbors for support. 



The so-called "red belt" injury is manifested by the sudden red- 

 dening and subsequent death of practically all the needles on the 

 exposed portions of the trees in a well-defined altitudinal belt. 

 Some are killed outright, though usually the buds remain uninjured 

 and the trees later recover, in some cases after complete defoliation. 

 The most extensive damage of this nature on record occurred in Jan- 

 uary, 1909, when large areas were affected in the Black Hills and 

 throughout the Rocky Mountains from Montana to Colorado. The 

 belt was generally from 200 to 400 feet in width between elevations 

 of 6,500 and 7,000 feet in the lodgepole region, and at lower eleva- 

 tions in the northwestern portion of Montana. Trees on all aspects 

 were affected, but the greatest damage was done on southerly slopes 

 and in situations exposed to the wind. The injury resulted from un- 

 usual weather conditions during the winter. In 1909 it was caused 

 by a chinook of several days, when the ground was frozen and cov- 

 ered with snow. The air was quite warm and the sun very hot, 

 especially when reflected from the surface of the snow, causing the 

 leaves of the trees to transpire all of their available moisture. Since 

 the roots were frozen and additional moisture could not be obtained 

 from the ground, the leaves withered, and in some cases the buds 

 also dried out excessively. The most satisfactory explanation o£ 

 the occurrence of the injury in an altitudinal belt is that early in the 

 winter, before the ground froze, snow fell at the higher elevations 

 above the zone of injury. Later the ground in the belt froze solid, 

 but not the ground in the zone below it nor that in the zone above it. 

 Later still the entire area was covered by a heavy fall of snow. In 

 this way the belt was the only part of the region in which the ground 

 was solidly frozen and no soil moisture was available to replace the 

 water transpired by the leaves. 



Hedgcock grouped the species of the lodgepole region in respect 

 to their susceptibility to this injury as follows, naming the most 

 susceptible first: 



Yellow pine. 

 Douglas fir. 

 Lodgepole pine. 

 Limber pine. 

 Engelmann spruce. 

 Alpine fir. 

 Juniper. 



Douglas fir unquestionably suffered more than did lodgepole on 

 areas where the greatest damage occurred. Many Douglas fir 



