58 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. 



The effect of logging on the pathological condition of white firs that 

 are left on the area may be twofold. The opening of the crown cover 

 through cutting will prove beneficial to all suppressed and interme- 

 diate white firs. The ready response of the species to light is well 

 known. It is probable that such trees, if already infected, will not 

 allow the decay to proceed very much farther, i. e., the newly formed 

 upper logs may be sound. These trees move up into the dominant 

 class. The mycelium in the heartwood, however, if well established, 

 will not die out, and after a while sporophores appear which carry the 

 disease to hitherto sound trees! As there can not be any infection 

 except through spores coming from sporophores on diseased trees, it is 

 evident that it is poor silviculture to leave individuals infected with 

 any parasite of economic importance on cut-over areas. Such trees 

 on timber-sale areas should be marked and cut under all circum- 

 stances if we expect to save and utilize the sound timber they may 

 contain and to protect other trees from decay. Sanitation of the 

 forest must be the first and fundamental step in forest regulation. The 

 introduction of the so-called sanitation clause in the timber-sale con- 

 tracts of the Forest Service aims at this very point. 



It is evident that blind enforcement of the sanitation clause, 

 following the letter and not the spirit of the principle expressed, is just 

 as pernicious as laxity in its application. Not all parasites are of 

 equal importance; our efforts should first be concentrated on the most 

 dangerous ones. The time will come when forest sanitation will 

 include all controllable elements making for loss in timber volume and 

 timber values. 



On the other hand, if only thrifty trees are left standing after log- 

 ging operations, they are, by the very opening of the " forest screen/ 7 

 more exposed to flying spores from surrounding untreated tracts, but 

 unless wounded they are in no great danger of infection. The smaller 

 the tract, the more will this influence make itself felt. The improved 

 conditions under which they grow will help them to either overcome 

 or limit the extent of decay in case they do become infected. As long 

 as we do not possess any exact figures on the recovery of white fir on 

 cut-over areas, however, it is advisable to consider wounded white-fir 

 trees left standing as unaffected by the opening up of the stand, at 

 least during the transition period, that is, in first fellings. All these 

 trees have grown up under unfavorable conditions, and the chances 

 that they are lastingly injured are considerable. By the time second 

 logging operations cover the area, it is to be assumed that a more pro- 

 found knowledge of the life history of white fir will be at hand. 



The choice of white-fir trees to be left on the area, with the expecta- 

 tion that they will be sound and merchantable at the next felling, 

 depends altogether on their condition and the length of time probably 

 elapsing until that felling takes place. Assuming that our figures 



