THE INFLUENCE OF THINNING 33 



cut-over area to a condition nearly equal to the uncut area called for a 

 subtraction or an addition. 



In Table i, comparing the total figures in the uncut area with the 

 figures given for the adjusted cut-over area, the cut-over area has al- 

 most similar averages for age, diameter (breast high), and height, a 

 much larger average crown. 21 per cent fewer live sporophores, 21 per 

 cent more dead sporophores, 8 per cent more sound trees, 8 per cent 

 fewer infected trees, 27 per cent fewer trees bearing sporophores, 8 

 per cent fewer trees showing rot at the stump, and identical figures for 

 mean annual diameter growth and for density. 



In Table 2 a similar comparison shows the grand fir on the cut-over 

 area has almost similar averages for age and diameter breast height, an 

 average height greater by 13 feet, a larger original crown and a large 

 average secondary crown not possessed by the trees on the uncut area, 

 39 per cent fewer live sporophores, 29 per cent more dead sporophores, 

 25 per cent more sound trees and 25 per cent fewer infected trees, 52 

 per cent fewer trees bearing sporophores, 25 per cent fewer trees show- 

 ing rot at the stump, and identical figures for mean annual diameter 

 growth and for density. 



On the other hand, the activity of the fungus is much more pro- 

 nounced in the uncut stand, where all the environmental factors favor 

 the progress of infection and decay. Here the vigor is greatly lowered, 

 due to the crowding of the stand, and by reason of this density and its 

 resultant shade the lower portions of the crowns die out, causing the 

 formation of dead branches and branch stubs, which become open to 

 infection. The shade produced by this crowding and its attendant 

 moisture conditions also favors the germination of the fungous spores. 

 In the cut-over area these factors are all reversed. Crowded conditions 

 give way to an open stand, light is admitted to the greater portion of 

 the tree, secondary crowns and secondary thickening of old crowns are 

 produced in place of dead branch stubs, and the vigor is greatly in- 

 creased. The annual rings become much wider, the efifect being evi- 

 dent soon after thinning, and consequently the trees show a larger 

 diameter growth. Conditions unfavorable to the germination and pene- 

 tration of the fungous spores are established and the data indicate, 

 although not conclusively, that the activities of the fungus within the 

 tree as regards the development and viability of the sporophores is 

 appreciably curtailed. The old sporophores that developed on the trees 

 while still in the forest had in most cases died and were completely 

 separated from the old pin knots by 5 or 6 layers of living wood. The 

 old branch wounds were thus completely occluded and the sporophores 



