THE INFLUENCE OF THINNING ON WESTERN HEMLOCK 

 AND GRAND FIR INFECTED WITH ECHINODONTIUM 

 TINCTORIUM 



By James R. Weir, Forest Pathologist, and Ernest E. Hubert, 

 Scientific Assistant, Office of Investigation in Forest Pathology, 

 Bureau of Plant Industry, Missoula, Mont. 



The opening up of a stand of timber by the methods as practiced in 

 present-day private logging- operations is usually brought about by the 

 cutting and removal of the most valuable of the tree species and leav- 

 ing the inferior or less valuable material standing. In many instances 

 on National Forests definite thinnings or selection cuttings are made 

 as a predetermined system of forest management. As a result of these 

 activities, especially the earlier logging and timber sales operations, 

 there are many logged-off areas which have a considerable stand of the 

 so-called inferior species left growing. These areas form admirable 

 sites for the study of the influence which thinning bears on the problem 

 of the decay in this type of stand and the probable sanitation effect it 

 may have on the surrounding forest. It is well to mention here that 

 thinning as used in this article refers not to a particular process, such 

 as selection cutting, but is used as a term indicating the removal of a 

 certain portion of the original stand. It is a well-known fact that the 

 thinning of a stand very appreciably affects the vigor and size of the 

 remaining trees and is not alone due to the increased light, but must 

 also depend greatly upon the increased root space and moisture content 

 of the improved soil.^ The aim of this paper is to determine, if possi- 

 ble, the influence which the thinning of a stand and the opening of the 

 crowns to full light might exert upon the development of the trees in 

 question in respect to vigor, annual growth, etc., and to note the effect 

 this might have upon certain phases of the life of the fungus infecting 

 them. 



The study should develop the part which light plays in increasing 

 the crown and increment, and thereby the vigor, and should bring out 

 the relation which the action of full sunlight has upon the sporophores 

 produced by a tree infected w^^ile in the original stand. 



' Zon, R., and Graves, H. S. : Light in Relation to Tree Growth. 1911. U. S. 

 Dept. Agr., For. Service Bui. No. 92, p. 18. 



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