species other than ponderosa pine was grouped 

 with the losses caused by disease and wind throw 

 and an annual loss rate of 0.75 percent of the total 

 stand of these species was estimated, or 342 million 

 board feet. 



Fire Depletion 



Although fire causes a much smaller loss of saw 

 timber than does cutting or insects, it is nevertheless 

 an important agency. Unlike cutting depletion, 

 the total loss from fire cannot be measured in 

 board or cubic feet. The outright killing of trees of 

 saw-timber size is only a portion of the loss; often 

 the greater part is in timber defective because of fire 

 scars, the destruction of immature stands or reduc- 

 tion in their stocking, and material losses in the 

 productivity of the forest soils. 



The study of fire depletion was based on fires that 

 occurred during the 12-year period, 1924-35. From 

 data obtained from these fires were computed aver- 

 age annual gross area covered by fire, the area de- 

 forested, the net loss of saw-timber volume in board 

 feet (table 18), and loss in trees 5.1 inches d. b. h. 

 and larger in cubic feet (table 19). Detailed fire- 

 depletion data by type and unit are given in 

 supplemental tables in the appendix. 



National Forests 



The average of 36,000 acres of national-forest 

 land covered by fire annually during the 12-year 

 period amounted to 0.33 percent of the total, but 

 considerably less than half of this was deforested. 

 Of the area deforested, approximately 40 percent 

 was occupied by noncommercial types, 35 percent 

 by saw-timber stands, and 25 percent by second- 

 growth conifer stands. Less than a third of the 

 burned area of saw timber was classed as defor- 

 ested, in contrast to more than half of the area of 

 other types in this class. The noncommercial 

 group of types includes the lodgepole pine types 

 which are highly inflammable (fig. 22), usually 

 inaccessible, and in the lightning zone. Forty per- 

 cent of the total area deforested was occupied by 

 immature lodgepole pine (type 26). Of the saw- 

 timber stands, the upper-slope mixture (type 27%) 

 was the most inflammable; the ratio of area de- 

 forested to the total area of the type on the national 

 forests was approximately two and a half times 

 that of pure ponderosa pine stands (type 20%). 



Table 18. — Estimated annual average gross joresl-land area 

 covered by fire, area deforested, and saw-timber volume (log 

 scale) lost, ponderosa pine region, 1924-35 



Ownership and forest-type groups 



National forest: 



Conifer saw timber (5}4 20, 20J4 20A, 



20B, 21, 27, 6, 7, 8, 9A, 23, 27^, and 29) 

 Conifer second growth (22, 28, 10, 9B, 24, 



28H, and 30)... 

 Noncommercial (4, 5, 25, 26, 33, and 38). . 

 Old cut-over areas, nonrestocked, and 



previously deforested burns (35A and 



37) 

 Hardwood timber ®\ l A and 31) 



Total 



Other ownerships: 



Conifer saw timber (5J4 20, 20^, 20A, 



20B, 21, 27, 6, 7, 8, 9A, 23, 27H, and 29). 

 Conifer second growth (22, 28, 10, 9B, 24, 



28K and 30) 



Noncommercial (4, 5, 25, 26, 33, and 38)... 

 Old cut-over areas, nonrestocked, and 



previously deforested burns (35A and 



37) 



Hardwood timber (31J4 and 31) 



Total 



All ownerships: 



Conifer saw timber (5V 2 , 20, 20V 2 , 20A, 



20B, 21, 27, 6, 7, 8, 9A, 23, 27^, and 29).. 

 Conifer second growth (22, 28, 10, 9B, 24, 



28K and 30) 



Noncommercial (4, 5, 25, 26, 33, and 38)... 

 Old cut-over areas, nonrestocked, and 



previously deforested burns (35A and 



37) 



Hardwood timber (31^ and 31) 



Total 



Area of 

 burns 



Acres 



16,676 



5, 307 

 13, 654 



35, 720 



31, 876 



11,737 

 5,144 



981 

 13 



49, 751 



48, 552 



17,044 

 18, 798 



1,058 

 19 



Defor- 

 ested 

 area 



Acre* 

 5, 334 



3,859 

 6,111 



15,304 



14, 955 



5,634 

 1,140 



21,729 



20, 289 



9,493 

 7,251 



Saw- 

 timber 

 volume 

 loss 



M hoard 

 feet 

 46, 002 



31 

 402 



46, 435 



39, 52S 



627 

 99 



40,254 



85, 530 



658 

 501 



The 46 million board feet of saw timber killed by 

 fire and not salvaged was only 0.07 percent of the 

 total volume of the national-forest saw timber. 

 Approximately 45 percent was ponderosa pine. 

 Timber salvaged annually averaged only 370 M 

 board feet, practically all ponderosa pine. 



Other Lands 



On lands other than national forest the area 

 burned over annually averaged 0.45 percent of the 

 total area of such forest land and the area de- 

 forested 0.19 percent, or approximately the same 

 ratio as on national-forest land. Approximately 

 69 percent of the area deforested was occupied by 

 saw-timber types, 26 percent by second-growth 

 stands, and the remainder by noncommercial 



39 



