314 



CONSERVATION 



still preserved in perfect condition after 

 thousands of years of service. 



The longevity of timber under these two 

 extremes of climate and moisture conditions 

 has naturally made people ask, What causes 

 wood decay? The answer is, fungi and 

 bacteria, low forms of plant life which live 

 in the wood and draw their nourishment 

 from it. These organisms are so small that 

 a microscope is required to see them, yet 

 their work results in the destruction of bil- 

 lions of feet of timber each year, and the 

 railroad corporation with its cross-tie bill 

 running up into seven figures and the 

 farmer who spends a hundred or so dollars 

 a year for fence posts are alike drawing upon 

 the knowledge of experts in all parts of the 

 world in efforts to learn the most economical 

 and most satisfactory method of preserving 

 wood against the inroads of decay. In study- 

 ing the means of preventing decay wood- 

 preserving experts have learned many things 

 about the obnoxious fungi which sap the 

 life of timber. 



The small organisms can grow either in 

 light or in total darkness ; but all of them 

 require requisite amounts of air, food, mois- 

 ture and heat. If one or more of these 

 essential requirements is lacking, they can- 

 not live, and the decay of timber will not 

 take place. Wood constantly submerged in 

 water never rots, simply because there is 

 an insufficient supply of air. This condition 

 accounts for the soundness of the old Baltic 

 piles. On the other hand, if wood can be 

 kept air-dry it will not decay because there 

 will then be too little moisture. The tim- 

 ber used by the Egyptians will last indefi- 

 nitely so long as it is bone-dry. 



There are a great many cases, however, 

 where it is impossible to keep wood sub- 

 merged in water, or in an absolutely air-dry 

 condition. In fact, a large percentage of the 

 timber which is used is exposed to the 

 weather, and is subjected to decay simply 

 because it contains enough air and enough 

 water for the decomposing organisms to 

 get a foothold. Decay is most serious 

 where the atmosphere is warm and damp, 

 because these conditions are most favorable 

 for its development. In the coal mines of 

 Pennsylvania timber decays in two or three 

 years because the temperature is warm and 

 constant and the air is damp. And in the 

 South, the warm, humid atmosphere often 

 causes the timber rapidly to decompose. 



Decay may be prevented by two general 

 methods, by treating the wood with antisep- 

 tics, thus poisoning the food supply of the or- 



ganisms which cause decay, and by treating 

 it with oils which render it waterproof. 

 A combination of these two methods is most 

 commonly used, as when wood is treated with 

 creosote which fills up the pores in the 

 timber and keeps out water and is also a 

 powerful antiseptic. 



The United States Government considers 

 the investigations of the preservative treat- 

 ment of timber of such importance that the 

 business of one branch of a bureau in the 

 Department of Agriculture — the "Office of 

 Wood Preservation" in the Forest Service 

 at Washington — is given over entirely to 

 the work of experiments in cooperation with 

 railroad companies and individuals in pro- 

 longing the life of railroad ties, mine props, 

 bridge timbers, fence posts and transmission 

 poles. Advice and practical assistance is 

 furnished all who request this advice of the 

 Forester. The lengthening of life of timber 

 means the saving of thousands of dollars 

 annually through doing away with the heavy 

 expense of labor and cost of material for 

 renewals. 



Damage by Barkbeetles in Northwest 



It is well known how eiiormous is the 

 damage done by fires to the forests of the 

 Northwest, but there are other enemies of 

 the trees of this region. Insects are also 

 active destroyers of live timber. 



The Forest Service has lately found that 

 in one locality in Washington a species of 

 h^rkheetlc—Dendrocfoiuis ponderosee. the en- 

 tomologists call it — has been killing spots 

 of thrifty young Douglas fir and doing thou- 

 sands of dollars of damage. These beetles 

 ordinarily breed only in small numbers be- 

 tween the bark and the wood of damaged, 

 dying, dead or recently felled trees, but when 

 suitable breeding places become particularly 

 numerous and favorable, they increase so 

 enormously in numbers that they_ are forced 

 to take up their residence in living trees, 

 which they promptly kill. 



The fact that these barkbeetles find such 

 favorable breeding places in old logging 

 works is a strong additional reason, the 

 Forest Service concludes, for burning over 

 slashings after logging. .If the beetles he- 

 come excessively abundant only when they 

 have the unconsumed debris from logging to 

 breed in, and if they will kill valuable tim- 

 ber when they do bemme excessively abund- 

 ant, foresters ask why leave this debris to 

 facilitate" propagation? 



