PROTECTION OF FORESTS FROM FIRE 243 



Fires may influence reproduction through their effect 

 on the soil and the soil cover. 'Frequently after fires the 

 ground is occupied by heavy brush or by grass, which 

 impedes or in some cases prevents the reproduction of 

 valuable trees. Many of the grass parks in the Western 

 mountains are the result of fire. A grass vegetation has 

 replaced the forest. The running wild of burned areas 

 to a heavy growth of brush is a common occurrence after 

 fires in many of our Eastern forests, as, for example, in 

 Pennsylvania. 



Forest fires modify the composition of stands. The 

 opening up of a forest may so change the conditions of 

 germination that some species cannot develop even when 

 seed is abundantly supplied. This is in some cases due 

 to the drying of the soil. A species which requires pro- 

 tection against drought in early youth might be excluded 

 from openings made by fire. In the same way the repro- 

 duction of a species sensitive to frost in early youth is 

 often confined to areas protected by old trees. 



Where the fire makes a large clearing, the succeeding 

 forest usually differs in composition from the burned 

 stand, except where there are only one or two species 

 native to the region. The first species to spring up on 

 the burn are those whose seed is readily and abundantly 

 distributed to a distance from the seed-trees. Thus, in 

 the north woods of the East, birch and aspen are among 

 the first species, because their seed is very light and is 

 blown by the winds to great distances. Bird cherry 

 comes up in abundance, because its seed is spread widely 



