50 BULLETIN 1204, U. S. DEPARTMENT OF AGRICULTURE 
ter and left untouched or merely charred the lower and deeper 
accumulation. Cost figures were never made available by the opera- 
tor; but the expense per acre must have been extremely low, as the 
only cash outlay was in the setting of fire. 
The first striking feature disclosed was that the fire spread freely 
through the western yellow pine-Jeffrey pine type, but entirely failed — 
to cover the ground in the mixed conifer type. Dozens of fires had — 
been set on the slopes, often by collecting dry material, but these fires 
invariably went out after covering a spot a few feet in diameter. . This © 
experiment, therefore, went to prove that in a country of diversified — 
topography the flats and warm slopes will be burnable before the cooler 
and moister exposures. 
The value of the burning in reducing hazard was studied in detail 
by locating sample plots on adjacent unburned portions. The details 
of a representative sample and check plot are given below: 
Pitot 2—BuRNED 
Slope.—20° N., 45° E., near bottom of slope. 
Elevation.—4,750 feet. | 
Depth of litter—Maximum, 0.07 foot; minimum, 0.00 foot; average of 20 meas- 
urements, 0.05 foot. 
Underbrush.—W hitethorn clumps now cover 30 per cent of the plot, though before ~ 
the fire not more than 10 per cent was covered. 
Reproduction.—Heavy stand of reproduction killed; only one live seedling found. 
Hazard.—The trampling by sheep has reduced the danger temporarily, but fire 
could run over most of the plot. 
PiLotT 2,—UNBURNED.-. 
(Adjoining area with same conditions of slope, elevation, and exposure) 
Depth of litter—Maximum, 0.09 foot, minimum, 0.00 foot, average of 20 meas- 
urements, 0.04 foot. Distributed more uniformly than on plot 2. 
Underbrush.—Only one whitethorn alive; several killed by suppression; small 
amount of grass and weeds. 5 
Reproduction.—Area uniformly covered with dense thickets of seedlings, and 
small saplings of incense cedar. 
Hazard.—Fire danger higher than on plot 2, because crowns of reproduction 
reach to the ground; no greater, if only litter is considered. 
On the burned plots studied in detail the average depth of litter 
was 0.075 foot and the corresponding check plots 0.058 foot. The 
actual increase in amount of inflammable material as a result of the 
, fire is further evidence that the practice of light burning gives, at the 
most, only an ephemeral reduction of hazard. Furthermore, on the 
burned plots the area occupied by brush increased about 30 per cent 
within the three years following the fire, due in part to the removal 
of the competing coniferous advance growth. 
A summary of the effect of the fire on the various classes of in- 
flammable material runs as follows, considering the effect first as it 
appeared immediately after the fire and then as it showed up three 
years later: 
UPPER LITTER 
(Needles, ete.) 
Immediate effect—Burned fairly completely. 
Subsequent effect—Renewed by natural fall from timber, from reproduction, and 
from brush killed; a noticeable increase over that before the fire. 
