248 FOREST PROTECTION 



consumed by a severe fire. The bare rock may be left ex- 

 posed and in such a case the soil has been entirely destroyed. 



A soil lacking humus and bare of htter is subject to erosion. 

 This carries away the most fertile portion of the soil. In 

 extreme cases the entire surface layers of soil may be eroded 

 leaving exposed the subsoil or even the imderlying rock. 



Injury to the Productive Power of the Forest. — Loss may be 

 sustained either in reduced quantity or quality of production. 

 This is primarily dependent on the condition of the soil, and 

 the extent to which the individual trees have been damaged. 



Fire injury to the productive power of the forest may be 

 classified as follows: 



(a) Injury due to replacement of good by poor species or to 

 failure of the burned areas to restock. 



Frequently the natural reproduction following a fire is of 

 species inferior to those previously occup)dng the ground. In 

 some cases this situation is reversed and a more valuable 

 species, preferring an open burned-over seedbed, seizes the 

 opportunity to restock the bum. This is an example of the 

 beneficial influence of fire. 



In numerous instances no natural reproduction follows the 

 fire and the burn becomes barren. 



(J) Injury due to reduction in the density of stocking. 



Fires which do not destroy the whole stand may break the 

 canopy and have the general effect of making the stand more 

 open by reducing the number of trees below the density 

 required for highest production. 



(c) Injury due to the poor growth of individual trees. 



Trees partially girdled at the base have lost part of their 

 equipment for transporting food materials and for building 

 wood structure. This throws an added burden on the cam- 

 bium layer of the ungirdled portions. Increased growth may 

 take place here, as a result of the enlarged food supplies 



