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 “xed 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 of 
the occurrence of the injury in an altitudinal helt 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. 
Hedgecock 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 
