202 Forestry Quarterly. 



The loss of the forest floor, the drying out and loss of fertility 

 of the site, have a marked effect on the growth of the remaining 

 trees. The dry, semi-arid conditions prevailing in many con- 

 stantly burned stands prevent the life of some species which might 

 withstand the fires themselves. Pin Oak (Q. palustris), for a 

 bottom land tree is rather fire resistant, yet it dies on sites re- 

 peatedly burned and consequently dry. Other species have their 

 growth seriously curtailed. Often a stand stagnates and scarcely 

 grows at all. "Stag-headedness" is a common result of recurring 

 fires which destroy the soil leaving the trees without proper 

 nourishment. Stands losing many of their members in early life, 

 by the direct or indirect effects of fire, suffer later from incom- 

 plete stocking. 



It is sometimes argued that fires by killing the smaller and 

 weaker trees, do the forest a service by effecting what is practically 

 a thinning. This may be true to a certain extent for some forest 

 regions, but certainly not for southern New England. The in- 

 jury to the remaining trees more than counter-balances the good 

 effect of the thinning. 



Direct Effect of Recurring Fires: There are two kinds of re- 

 curring fires — annual and periodic. 



After annual fires have swept a tract a few times, there is noth- 

 ing left to burn but the accumulation of a single season. There- 

 fore fires are progressively less intense till they reach a point of 

 uniform minimum intensity. One season's accumulation of litter 

 is seldom sufficient to generate enough heat to injure the cambium 

 of trees out of the sapling stage; hence if a mature stand begins 

 to suffer annual burning without having been previously injured, 

 little direct damage results. If it has been previously injured so 

 that the wood at the base of the trees is exposed, fire becomes a 

 fourth agent, with insects, fungi and wind, in the destruction of 

 the injured trees. While the charring of the wood produces an 

 unfavorable condition for the entrance of insects and fungi, it 

 usually merely drives their attacks higher up where the wood is 

 imcharred. Annual fires often at length reach the roots. In 

 time they will destroy even a mature hardwood stand, killing the 

 large trees one by one and preventing all reproduction. 



The effect of periodic differs somewhat from that of annual 

 fires. Time enough elapses for sufficient litter to form for a kill- 



