NOTES ON WINTERKILLING OF FOREST TREES.* 

 Carl P. Hartley. 



The observations given below were made in Dis- 

 trict 2 of the United States Forest Service, which includes 

 Colorado, Kansas, Nebraska, part of South Dakota, and Wy- 

 oming. The national forests in this region are administered 

 by the Forest Service office at Denver, with which the writer 

 has been cooperating. The observations here reported are not 

 complete or conclusive, but may be of value to those who are 

 interested in the problems connected with winter injury to 

 forest trees. 



Winterkilling is a name under which different types of 

 injury are grouped because of the unfortunate lack of knowl- 

 edge as to the distinctions between the types and the factors 

 which cause each type. The study of winter injury in the 

 forests is not of any great immediate economic importance, 

 because there is relatively little chance to prevent it even after 

 the controlling factors are known. However, notes on its 

 occurrence, and especially on the chinook type of injury which 

 occurred in the Black Hills Forest in 1909, will be of some 

 interest to foresters as well as to patholo'gists. 



The first type of winterkilling to be considered is that 

 which is believed to be most common. This typically affects 

 reproduction, and does little harm to saplings and older trees. 

 The tips of the branches which are less than one year old, 

 are especially subject to injury, but where the damage is seri- 

 ous, the tree may be partially or completely killed. On exposed 

 hillsides Lodgepole Pine (Pinus contorta) reproduction has been 

 seen which was turned entirely brown by the large number of 

 winterkilled trees. To what extent smaller trees, both natural 

 regeneration and stock resulting from direct seeding, are 

 killed during their first two or three winters is not known to 

 the writer ; some loss undoubtedly occurs. Winter injury dur- 

 ing the first winter after planting is sometimes an important 

 factor in reducing the stand in the sand-hill plantations on 

 the Nebraska Forest. 



'Published by permission of the Secretary of Agriculture. 



