44 FORESTRY 



recover. Finally scrubby and worthless shrubs like bear 

 oak which can sprout annually for indefinite periods - 

 take the place of the chestnut and valuable oaks, and the 

 area can be classed as non-productive. Large districts of 

 this character can be found in parts of Pennsylvania. 



Perhaps the most common source of fires is the burn- 

 ing of the tops left after lumbering. Both in pines and 

 hardwoods, when logging is very heavy, the inflammable 

 nature and great quantity of the debris created, coupled 

 with the increased exposure of the soil to the sun and 

 wind, causes a very hot fire. This fire is almost sure to 

 kill chance seed trees left because of some defect, and 

 to wipe out all traces of seedling and sapling growth. A 

 condition is created which is favorable to future fires, and 

 the causes for these are not far to seek, in a region where 

 no effort is made to suppress them, and the resultant dam- 

 age is not appreciated. Forest fires are said by good 

 authority to have destroyed as much timber as the lum- 

 bermen have cut. But a far greater loss than this is rep- 

 resented in the seedlings burned, and the absolute pre- 

 vention of future growth over almost all of our pine forest 

 area. 



Other Forest Enemies. Of the other natural enemies 

 which threaten the forest, none are of such a nature that 

 they form a serious and universal menace. Occasional 

 fungus diseases occur, such as the chestnut blight, which 

 at present threatens this tree in the southern New Eng- 

 land region. The trees attacked are killed by the girdling 

 of the cambium through the operation of the fungus. Dry 

 seasons probably give rise to such epidemics by weaken- 

 ing the naturally resistant trees, and such a condition will 

 correct itself. Of the fungi which attack the heartwood, 

 there are several kinds but all of these operate only upon 

 trees which have some injury in the bark. Danger of pre- 

 mature decay from this source may be reduced in a well- 

 managed forest by removing the fruiting bodies of such 



B III 12 



