10 EMORY OAK IN SOUTHERN ARIZONA. 



CAUSES OF ItfJUKY. 

 FIRE. 



Emory oak constitutes no exception to the general truism about 

 any tree in America that fire is its greatest enemy. Fire is not only 

 a source of injury in itself but is the antecedent of secondary injury 

 by insects or fungi, or both combined. The worst fire season lasts 

 from February until the heavy rains of July, and the most severe fires 

 occur in May or June. 



In the open valleys the thick bark of the old trees forms a sufficient 

 protection against most of the fires, but younger trees, up to 2 or 3 

 inches in diameter at the base are seriously injured, and smaller 

 sprouts and young shoots are killed outright. In narrow valleys and 

 on bench lands, where the thickets reach a maximum density and 

 there is likely to be a good deal of litter on the ground, the fires are 

 extraordinarily bad, and may kill as much as 30 per cent of the domi- 

 nant stand and all of the shoots and suppressed growth. Slope stands 

 are damaged in direct proportion to their density and the amount of 

 ground cover. 



The usual fire damage on all growth more than 2 inches in diameter 

 breast high below that diameter the trees are killed consists of a 

 scorched bark which is rarely burned through, though it is usually 

 cracked and loosened from the trunk. This permits the entrance of 

 fungi which cause a heart rot that is very common. 



When sprouts are killed back to the ground, from 5 to 25 new 

 shoots spring from the root collar and make a height growth of 

 from 1 to 4 feet the first season. If the fire is late in the season this 

 growth fails to harden sufficiently to withstand winter conditions 

 and is partially killed back. Occasionally some of the very tender 

 shoots are affected by sun scald. 



FIRE PREVENTION. 



The people of the region have yet to learn the necessity of fire 

 protection. Yet the effect of prevention of fire on the Garces Na- 

 tional Forest can not fail to have an educative value, and the prac- 

 tice of allowing fires to run unchecked will come to an end. Fire 

 fighting is comparatively easy because of the open nature of the 

 stands, which makes most of the fires merely surface fires, except in 

 the thickest stands or during severe winds. Where the grass is 

 thick, the most effective method is judicious back-firing supplemented 

 by beating the fires out with squares of canvas or wet gunny sacks; 

 where the grass cover is thin or broken, the beating alone will suffice. 

 The ground is not rough, it imposes no difficulties of transportation, 

 and there are plenty of roads and trails, so that fire fighters can go 

 readily from one place to another. The one difficulty is the scarcity 

 of labor available, but this can be partly met by an adequate system 

 of patrol supplemented by the use of the telephone. 



