ROLE OF FIRE IN CALIFORNIA PINE FORESTS 19 
clusive. Besides the area covered by the fire, an adjoining area of 
similar type and topography was used as a control plot and examined 
during the same period. dn both oi these plots a hundred per cent 
cruise of all insect damage was made. Fortunately, in connection 
with other studies, the cruise for 1916 had been made before the 
_ occurrence of the fire and the records for that year, covering as they 
do a large area long undisturbed by fire, may be accepted as showing 
the stage of infestation of the area before the fire. Table 8 presents 
data of this study. 
TaBLE 8.—Relation of fire and insect damage 
{Mormon Hill burn, Sierra National Forest, October 15, 1916] 
Insect damage 
} 
Insect damage on are: 
pesert ge On Bersict area on unburned area! 
Year of observation 
| Trees Total Loss per} ‘Trees Total | Loss per 
| lost loss acre lost loss acre 
——————q— leq“ | KS —xHKt ) moO xqxxcxxx6r 
Board feet Board feet Board feet | Board feet 
2, 745 | 51 | 17 5 | 11 
PR eee et Si _ sat wed Be Pe ew ea as ao 47 3 22, 695 | 
ALP 7 ra Seid SS rg ea bare AA ee wk dee Qe eh a 97 | 129, 970 203 21. 30,700 | 15 
OTH Ghee ten cere ee rea ee? 252382 116 | 120, 690 189 37 47, 033 24 
| LU sees area Sanaa SS ies eee eee 40 33, 370 52 43 51, 600 26 
SRO aire fae We sed PES ak 300 | 316, 775 | 495 118 | 152,028 | 76 
| 
1 Unburned control area of 2,000 acres, adjoining Mormon Hill burn. 
2 Data for this year gathered before the burn, over a territory of 640 acres long undisturbed by fire. 
On the control plot the infestation during the period of observation 
was relatively constant, both as to number of trees killed each year 
and the actual volume lost. There was a slight tendency to increase 
_from the beginning to the end of the observation period; but the 
_ maximum loss in any one year did not exceed 26 board feet an acre, or 
one tree to 50 acres, which is well within the limits considered as nor- 
mal infestation. 
On the burned area the loss during the year before the fire was 
- somewhat greater than for the control plot. As indicated by the con- 
trol plot, the normal infestation was increasing slightly during the 
period of the study, but the increase on the burned area was far more 
rapid than the normal rate. In the year following the fire a sudden 
and sharp increase in loss from insects was reported. In 1918 the 
number of trees lost was stilllarger. In 1919, the third year after the 
fire, the infestation subsided to Shout the same level as betore the fire. 
Other evidence confirming these investigations has been obtained 
in the study of the Snake Lake experimental burn. The figures on 
insect damage on this area, shown in Table 9, were obtained by a 
hundred per cent cruise which covered 105 acres burned in 1919 and 
again in 1920; also from an unburned control plot adjoining the burned 
area. As has been explained, the Snake Lake plot is an area burned 
over lightly for experimental purposes. All the fires here have been 
very slow in spreading and light in character, the burning being done 
at the earliest possible date in the spring and the fires set to burn 
downhill under control. 
