BURNING WOODED PASTURES AND FORESTED RANGES 229 



because of the deterrent effect it has upon erosion and as a ground 

 cover to stabilize streamfiow. If the timber and undergrowth 

 are killed by fire, not only is the financial loss great but the danger 

 of erosion is much increased. Forest fires vary all the way from 

 light surface fires that consume only the grass and topmost litter 

 to conflagrations that race through the treetops and destroy 

 every vestige of Hfe in the forest. Upon the intensity of the fire 

 depends the relative amount of damage done to both the timber 

 and the forage. 



In general, fires are destructive to forest and open pasture 

 lands ahke and differ only in degree. Owing to the large amount 

 of fire material in a woodland the effect upon the soil is usually 

 most serious there. Large areas are not uncommon on which 

 the soil is rendered " lifeless " or virtually sterile (devoid of 

 humus, bacteria, and earthworms) and for many years incapable 

 of supporting vegetation except of the most early-maturing and 

 drought-enduring type. 



Jacquot,^ in discussing the effect of fires on vegetation, says: 



The extraordinarily vigorous growth following on the burning of herbaceous 

 and semi-woody plants would, no doubt, tempt many people to a conclusion 

 favourable to fires as stimulators of growth. This exuberance, however, is 

 merely the effect of a temporary stimulus; it is not sustained, and is followed 

 by a depression, which is the reverse of enhancement. Chemical decompo- 

 sition in operation in the soil provides slowly, but surely and indefinitely, the 

 organic products which the growing stock assimilates every year. The fire, 

 however, at one operation, effects the transformation of the detritus and, so 

 to speak, condenses by anticipation the smaU but certain interests into an 

 immediately available capital, which stimulates for the moment, but rapidly 

 disappears, leaving to the trees only a minute fraction. The greater portion, 

 swept away by rain, flows into the subsoil out of reach of the absorptive 

 power of the enfeebled roots. In a very few years there remains no particle 

 of the ashes, and as the soU covering has not had time to re-establish itself, 

 the vegetation falls below its original condition. 



In rare cases, where deep layers of arid soil overlie the subsoil, the products 

 of combustion supply an excellent alkaline corrective. On the other hand, 

 if the humus is scanty, a fire is disastrous. In any case " fire is ever a dangerous 

 auxiliary." 



1 Jacquot, A., "Incendies en foret." English translation by C. E. C. Fischer, 

 p. 196, 1910. 



