94 THE BOOK OF FORESTRY 



ous, for while they consume the seed which has fallen and 

 the little seedlings and may even kill some of the thin- 

 barked saplings, they do not as a rule kill merchant- 

 able timber. All of their results, however, are not visible 

 immediately. Many a woodlot which has been swept by 

 a severe ground fire may, four or five years later ex- 

 hibit a very large number of trees affected with fungus 

 diseases just above the ground. The trees really were 

 damaged at the time of the fire but did not show it 

 until later. Even though the trees may not be severely 

 damaged the fire consumes the litter and leaf mold which 

 should have enriched the soil and as a consequence 

 growth will be seriously checked. On cutting down a 

 tree the scars of an old fire may be seen towards the 

 center of the tree and it is quite common to note that 

 the annual growth rings have diminished in width after 

 the fire, owing to the burning up of the food supply 

 stored up in the humus. 



Surface fires are most common in the spring and fall 

 and if the ground beneath is damp only the loose leaves 

 on top will be consumed. In the regions where the 

 long winters and short cool summers cause a thick 

 accumulation of leaf mold or duff, this layer may take 

 fire and the ground fire thus started may assume serious 

 proportions. In such cases it may smolder along beneath 

 the surface of the peaty layer, burning off the roots of 

 the trees until the first strong wind will pile them up 

 like jackstraws. If the duff is particularly thick a 

 ground fire may smolder for months. 



A crown fire is a calamity hard to appreciate, and 

 to see or hear one is an experience never to be for- 

 gotten. Crown fires occur only during extremely dry 

 seasons and in dense coniferous stands where the trees 

 are very close together. The start of a crown fire occurs 



