lO Forestry Quarterly. 



reproduction under mature stands, means that Jack Pine forests 

 can in nature only be secured by Hre. This fact will be borne 

 out by further investigation. 



Danger and Diseases. — Jack Pine is fairly resistant to fire. 

 During early youth, however, up to 30 years of age, the thin, soft 

 bark of the sapling offers no resistance to the forest fire, while the 

 resinous foliage presents an ideal fuel for the flames. Sweeping 

 fires receive a great impetus when pure Jack Pine stands are 

 encountered, and it is here that the greatest damage is done. 



The adult tree is not as susceptible to damage by fire, the bark 

 being thicker and firmer. Yet in an ordinary ground fire as much 

 as 60% of the stand may be so weakened that the stock will 

 eventually die, death being caused by the killing of the root 

 system or either by insects. 



Jack Pine is one of our most hardy species, and rarely injured 

 by frost even during the earliest stages of its development, and 

 altogether it can adjust itself to extremes of temperature which 

 are very common to its range of distribution. 



The normal healthy tree is practically free from insect attack 

 of every kind. Rare instances have been noted where the leaders 

 of sapling trees have been wounded, resulting in a resinous excre- 

 scence interiorly on which a pupa was developing — "presumably 

 Retina comstockiana" — beyond this case no insects have ever 

 been observed attacking the healthy tree. 



The weakened, or fire-killed tree, however, is the subject of 

 attack immediately after the fire i. e. if during the summer by 

 bark and wood destroying insects common to the region, e. g. 

 genus Monohammus and Pissodes strobi. 



In two seasons after the attack, the wood will be so riddled as 

 to be useless for lumber, although not damaged so seriously as 

 to prevent its use for tie purposes. 



Porcupines seem to have a particular liking for the bark from 

 trees 10 to 14 inches in diameter, and, although the damage is not 

 widespread, individual cases have been seen where as many as 18 

 trees on a quarter acre have been girdled by a band one foot high 

 around the stem, with all the enclosed bark eaten clean away. 



