6 BULLETIN 1140, U. S. DEPARTMENT OF AGRICULTURE. 



lowed then that poles and young thrifty standards were subject to 

 much more rapid deterioration than large trees, in which the ratio 

 of sapwood to heartwood is inverted. 



The upper side of the trunk decayed most rapidly, and the under 

 side, the portion resting on the ground, much more slowly. This is 

 probably explained by the retarding effect on the development of 

 wood- destroying fungi from the excessive moisture content, lessened 

 oxygen supply, and lower temperature of the wood of the under 

 side as compared with the upper side. Decay first appeared along 

 the checks, but avoided the dried outer layer of sapwood. Tongues 

 of decay extended down from the ends of the checks. The decay 

 then spread from the checks, finally involving the entire sapwood 

 with the exception of the outer layer. Where the bark was left on in 

 the top, the outer layer also decayed. Barking, the tree somewhat 

 retards decay, but not enough to be of practical importance, while 

 on the other hand it promotes checking. 



Generally it was impossible to determine the exact kind of decay 

 in the different trees, but where this was done it was found that a 

 white cellulose pocket rot 3 caused by Polyporvs anceps Pk. was most 

 common, while a brown friable rot caused by the brown Lenzites 

 (Lenzites sepiaria (Wulf.) Fr.) and a yellow-brown friable rot 

 caused by Fomes pinicola (Fr.) Cke. occasionally occurred. 



Heart-rot was not found in the trees until the third season of 

 exposure. Decay first appeared as tongues running in from the 

 sapwood or following in along deep checks. The white cellulose 

 pocket rot was most common. 



A negligible amount of loss resulted from breaks, usually in the 

 top, when the trees were felled. 



A more important source of cull was fire at the time the trees were 

 felled and bucked. This sometimes did considerable damage. When 

 the bark was burned, trees with open wounds were very likely to 

 burn out along the scar and for some distance in advance. Fire 

 scars, particularly in pitchy butts, were common starting points for 

 destructive burns. Felling trees across one another or leaving limbs 

 resting on the trunk resulted in additional loss from fire.- 



The loss caused by wood-boring insects was negligible. Ambrosia 

 beetles did not attack the trunk from which the bark had been re- 

 moved, while the round-headed and flat-headed borers did not attack 

 the trees until sap-rot was well started. 



From the foregoing discussion of Table 2 it is apparent that while 

 checks caused some loss (and in a lesser degree so did fire), decay , 

 particularly the very rapid decay of the sapwood, is responsible for 

 most of the deterioration in these trees. 



CONCLUSIONS. 



The facts brought out in this bulletin should not be considered 

 as of value for local application only. The climatic conditions of 

 the Klamath Lake region, characterized by a small yearly precipita- 

 tion, with a long summer drought, often beginning in the late spring 

 and extending well into the fall, and low winter temperatures, are 



8 This decay has also been called western red-rot. According to Dr. J. R. Weir, 

 Polyporus eUisianus Murr. as known in the West is the same as P. anceps Pk. 



