THE INFLUENCE OF THINNING 35 



class, but having a somewhat lower mean annual diameter growth for 

 the period prior to the thinning, are as follows : 



The thinning produces in both trees a very marked increase in the 

 width of the annual rings, being more marked in the case of hemlock. 



A larger diameter, height, and crown growth is recorded for both 

 species of tree growing in the cut-over area. In the case of the hemlock 

 a very marked secondary growth of the old crown takes place, while in 

 the grand fir a distinct secondary crown appears on the lower trunk 

 below and intermingled with the original crown, this secondary crown 

 in many cases extending to within a few feet of the ground. !More 

 injuries were found on trees on the cut-over area and a greater number 

 healed than on the uncut area. These facts indicate a greatly increased 

 vigor. 



A comparison of the cut-over and uncut areas after the figures for 

 the cut-over area had been adjusted, so as to be more nearly comparable 

 with those of the uncut area, shows the following results : The mean 

 annual diameter growth for the cut-over area was found to be 143 per 

 cent greater in hemlock and 176 per cent greater in grand fir than a 

 similar growth for similar tree species upon the uncut area. These 

 figures formed the basis for adjusting the figures of the cut-over area 

 to those of the uncut area. 



A comparison of the data thus secured indicates that a less favorable 

 condition for fungous activity exists within the cut-over area, and 

 shows plainly that a highly favorable environment for the fungus is 

 present in the uncut area. The total number of infected trees, the total 

 number of live sporophores, and the total number of sporophore-bear- 

 ing trees are comparatively less on the cut-over area for both species 

 of tree. 



A conclusion is reached that the influence of thinning very appre- 

 ciably affects the vigor of the trees on the cut-over areas, as shown by 

 the increased diameter, crown, and height growth, as well as the num- 

 ber of injuries healed. 



That a restrictive influence due to thinning is apparently exerted 

 upon the activities of the fungus Echinodontium tinctorium infecting 

 hemlock and grand fir. The increased light, the absence of maximum 

 moisture conditions and shade common to timber stands of this region, 

 and the increased light due to thinning are apparently unfavorable to 

 the germination and penetration of the fungous spores. 



The thinning influences affecting the fungus Bchinodontinin tiitc- 

 toriitiii are not of sufficient importance to cause any variation from the 

 predetermined sanitation rules to be applied to these species of trees. 



