Notes on Winterkilling of Forest Trees 



41 



taneous and sudden appearance of the trouble on both isolated 

 and massed trees, and by the failure of tests in moist chambers 

 and cultures to develop any known parasites from the killed 

 twigs. 



The only special significance of the observations of this 

 case of spring injury in Nebraska is that some of the tip injury 

 found in forests, and commonly called winterkilling, may 

 h.ive occurred at other times of the year, and that freezing 

 temperatures may not have any necessary connection with 

 certain types of winter injury. 



The statement of a Forest Service officer, that on the 

 Colorado National Forest the needles of a young Lodgepole 

 Pine frequently die while covered with snow drifts, is of in- 

 terest as indicating an entirely different type of winterkilling. 

 Since snow is excellent protection against excessive loss of 

 water, and against alternation of freezing temperatures with 

 those much above freezing, it is hard to offer any purely 

 physical explanation of this. Possibly the trouble is of the 

 same order as the Schutte or leaf-cast disease of German forest 

 trees, which often kills seedlings covered with heavy mulch. 

 If a parasite should be found to work in the needles of the 

 plant when thus buried in snow, so that their temperature 

 never goes materially above 32 Fahr., we would have a very 

 interesting phenomenon. 



The most interesting type of winterkilling is the chinook 

 type, of which an excellent example appeared in the Black 

 Hills Forest in South Dakota in 1909. The following weather 

 records were taken by Mr. E. F. Irwin at Lead, during Jan- 

 uary. The thermometer used was Fahrenheit, and readings 

 were taken at 4:30 P. M. 



