72 COMMISSION OF CONSERVATION 



the absorption of moisture by the balance of the material, bringing 

 about partial decay. In unlopped tops, possibly an average of i8 years 

 would be required for decay, while the period of extreme fire danger 

 would extend through not less than half this period instead of being 

 limited to about 3 years as in the case of lopped tops. In a limabering 

 operation, where only saw logs are removed, the time required for 

 decay in lopped tops may be averaged at 8 years and for imlopped tops 

 at about 25 years. These statements must be regarded as only the 

 roughest kind of approximations, intended merely to give some idea 

 of the relative rate of decay under different average conditions. There 

 was not sufficient opportunity to check all these figures with field ob- 

 servations, and the subject should be investigated fvirther. 



The striking point in connection with the efficiency of top-lopping 

 is the fact that the period of extreme danger is concentrated from 8 or 

 10 years to approximately 3 years, and that decay is practically complete 

 in 7 or 8 years, with only a moderate fire danger after the first three 

 years, instead of having the period of decay doubled or tripled with a 

 serious fire danger covering at least the first half or two-thirds of the 

 total period required for decay. 



The margin of difference is of course greatest on a lumbering, 

 operation and decreases with the degree of utilization into the top. 

 As previously noted, on a present-day pulpwood operation, the amount 

 of brush necessarily lopped from the merchantable portion of the stick 

 may be as much as 90 per cent, of the total amount of brush originally 

 on the tree. It is self-evident that decay will on the average proceed 

 much more rapidly, and the fire danger will be much less serious after 

 a few years, where 75 to 90 per cent, of the brush is lopped, as on a 

 modem pulpwood operation, than it will in the case of an old-time 

 lumbering operation, where the percentage of unlopped material may 

 closely correspond to these figures. Any increase in the percentage 

 of brush lopped, whether by closer utilization or through observance of 

 law, wiU inevitably increase the average rapidity of decay and will 

 thus decrease the fire danger to that extent. 



Since the fire danger due to slash is in direct proportion to the 

 amount of brush, the above conclusions may be stated in another way. 

 In an ordinary lumbering operation, the lopping of tops will reduce the 

 period of decay from 25 years to 8 years on 75 per cent to 85 per cent of 

 the debris, while the period of most extreme fire danger will be decreased 

 from 10 years to 3 years ; this statement assumes that the lower 

 branches, comprising 15 to 25 per cent, of the debris, would be lopped 

 in any event as a part of the operation. In a pulpwood operation, 

 lopping will reduce the period of decay from 15 years to 7 years, on 



