5i8 



AMERICAN FORESTRY 



certain areas of the south, where long- 

 leaf pine is not reproducing itself — not 

 because there is a lack of seed or be- 

 cause the conditions for germination 

 are unfavorable, but because the annual 

 fires kill the young trees. 



Eires 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 val- 

 uable trees. ]\Iany of the grass parks 

 in the western mountains are the result 

 of fire. A grass vegetation has re- 

 placed 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 ger- 

 mination that some species cannot de- 

 velop even when seed is abundantly sup- 

 plied. This is in some cases due to the 

 drying of the soil. A species which re- 

 quires protection against drought in 

 early youth might be excluded from 



openings made by fire. In the same 

 way the reproduction of a species sensi- 

 tive to frost in early youth is often con- 

 fined to areas protected by old trees. 



Where the fire makes a large clear- 

 ing, the succeeding forest usually dif- 

 fers in composition from the burned 

 5:tand, 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 by the birds, and prob- 

 ably much of it is already in the ground 

 before the fire. The trees with heavier 

 seed creep in gradually after a few 

 years. 



Fires may kill certain non-resistant 

 species, and thus stop their supply of 

 seed. The tendency of repeated fires is 

 to reduce the number of species in a 

 stand. 



(To be continued) 



