1398 A NATIONAL PLAN FOR AMERICAN FORESTRY 



2. How much damage will a given fire cause to the productivity 

 of the land (the site)? 



3. With what degree of difficulty will a forest be restablished after 

 fire? 



4. Will future protection be increased in difficulty after a fire runs 

 over the forest? 



These criteria, which reflect the major purposes in all forest 

 management, are interrelated and have been used in this inquiry as 

 a device to measure the degree of damage that a given forest type is 

 likely to suffer as a result of fire. In applying them we frequently 

 find, for example, that a mere surface fire may cause the complete 

 destruction of a spruce or white-pine forest. A fire of moderate 

 intensity in the ponderosa pine type will seriously injure the site, 

 wipe out young reproduction, and take some toll of mature timber. 

 In the hardwood forests of the Central States, a ground fire will 

 usually diminish the growth capacity of the forest and stimulate 

 decay from damaging wood-destroying fungi, seriously depreciating 

 the quality of timber. In the longleaf-pine type, fires do far less 

 damage than in the other types mentioned. A fire in the brush-field 

 watersheds of California seriously threatens storage reservoirs, special 

 spreading grounds, and dependent agricultural land for 3 to 5 years, 

 until a new brush cover returns. In a like manner, the damage done 

 by fire to forage and watershed values, recreation values, and wild 

 life varies between regions and even within a region. These varying 

 factors have been taken into account in the determination of the 

 objective in fire control. 



Realizing that complete fire exclusion is not a practicable measure 

 and in many instances is too costly, an objective in fire control has 

 been set up for each forest type based on the percentage of the area 

 that may burn over annually without impairing radically the forest 

 values as determined by the predominant purposes of management. 

 This objective of fire control is expressed as the area of allowable 

 burn, and has been determined for each of the major forest types 

 (table 3). It becomes obvious that the absolute acreage burned over 

 in different forest types is not the sole criterion either of the damage 

 sustained or of how nearly the objective has been met. Tin's annual 

 allowable percentage index has been calculated by considering how 

 the four factors influencing damage from fires operate in the different 

 forest types of the United States. Controlled fires used for definite 

 silvicultural or protective purposes are not included in computing the 

 allowable burn. 



From these estimates of allowable percentage of burn in forest 

 types it is possible to compute a percentage for each of the forest 

 regions. Obviously, this composite regional percentage is only a 

 very rough estimate of value and a broad indicator of the goal in 

 view to permit a somewhat more general administrative grasp of the 

 fire situation. Such figures, computed separately for the national 

 forests and for the areas outside, are given in table 4. 



