Apr. 15, 1925 
757 
Use of Liability Ratings in Forest Fire Protection 
type represented by those trees, and 
not with the type represented by the 
possibly more obvious cover, such as 
brush. In other words, brushfields 
which have a good stand of tree re¬ 
production beneath the brush cover 
should be classed with the proper 
timber type, and not with “ brush.” 
In case of two-storied types, as conifers 
under aspen in some parts of the Great 
Basin region, the cover should be 
classed according to the species of 
chief economic or silvicultural im¬ 
portance. For instance, if such a 
stand is to be handled as an aspen 
forest, the conifers may be considered 
as underbrush, and the type be called 
“ aspen.” But if the conifers are to 
grow to maturity and become the 
chief crop, and the aspen represents 
only a temporary phase of the devel¬ 
opment of a conifer stand, then the 
cover should be designated as belong¬ 
ing to the proper conifer type. Strictly 
speaking, there should be classed as 
“subalpine” only the strictly non¬ 
commercial scrubby or scattered high 
altitude stands, although the ratings as 
developed in this study undoubtedly 
included some merchantable fir and 
spruce and probably some lodgepole 
pine stands as subalpine. 
In general, the definitions of the 
different types will be about the same 
as those prescribed for use in timber 
surveys. In some cases, however, two 
or more of these types have been 
grouped together in the present study, 
and some of these groups may be al¬ 
lowed to stand even in working out 
more detailed ratings in the future. 
Others should be separated if possible. 
Such are the aspen type of the Cen¬ 
tral Rocky Mountains, now combined 
with other types; the Engelmann 
spruce and subalpine types, now com¬ 
bined in several regions; and the brush, 
grass, and woodland types, now thrown 
together in a number of cases. In some 
instances, where a type occurs over a 
limited area within a region, it has been 
combined with other types. Thus the 
limited areas of western yellow pine 
in the Northern Rocky Mountain re¬ 
gion should be thrown in with the 
Douglas fir or lodgepole pine types. 
Age classes. —Classification as to age 
should be based on the age of the 
major part of the stand; for instance, 
a very scattered stand of old seed trees, 
over a fairly well-stocked stand of re¬ 
production, would be classed as repro¬ 
duction; a stand composed of trees of 
several age classes, but with a large 
preponderance of mature trees, would be 
classed as mature. Not more than 
five age-classes should be recognized. 
These are: 
1. Reproduction_Trees up to 4 inches d. b. h. 
2. Small poles_Trees between 4 and 7 inches 
d. b. h. 
3. Large poles_Trees between 8 and 11 inches 
d. b. h. 
4. Young merchant- Trees 12 inches or more in 
able. d. b. h., up to the rota¬ 
tion age, or the age gener¬ 
ally considered as represent¬ 
ing maturity. 
5. Mature and over¬ 
mature. 
In addition to these five classes, a 
sixth class of stand should be recog¬ 
nized, viz: All-aged, where practically 
all ages are present in approximately 
equivalent proportions. 
Risk classes. —Each stand, after 
being classified according to type and age 
class, should be further classified accord¬ 
ing to the degree of risk involved. ‘ ‘Risk’ J 
is used here in the sense of inflammability 
and controllability, .independent of the 
probability of fires starting or of the 
presence or absence of a protective 
organization. For the purpose of 
rating liabilities, three risk classes 
should be recognized, based on the 
susceptibility of the stand to fire. 
This susceptibility is determined by 
the fire resistance or inflammability of 
the component species and of the ground 
cover, and to some extent by topo¬ 
graphic conditions, which favor or 
hinder rapid spread and destructive¬ 
ness of fires, and make control work 
difficult or easy. These classes may 
be designated as low risk, average risk, 
and high risk, and should represent the 
relative risks as between stands of the 
same type and age class, but not 
between stands of different types. A 
stand of western yellow pine classed as 
“high risk” might not represent as 
great damage or cost as a “low risk” 
stand of western white pine, but it 
would represent a risk greater than the 
average for the yellow pine stands in 
the region concerned. Brief tentative 
specifications for the different risk 
classes follow. 
LOW RISK 
Reproduction —Young trees scattered as individ¬ 
uals or in patches, with comparatively little brush 
or litter, or where the cover is grazed fairly close 
before the fire season, or where the inflammable 
ground cover as a whole—including tree reproduc¬ 
tion, grass, weeds, brush, and litter—is not con¬ 
tinuous, but is broken by numerous openings or 
patches of bare soil, rock, or less inflammable vegeta¬ 
tion, (such as bear clover). On sheltered flats or 
moist bottoms, the cover may be more continuous. 
Pole stands— For larger poles, stands with com¬ 
paratively little undergrowth or dead and down 
material, and with boles fairly clear of dead branches 
or moss. For smaller sizes of poles, broken stands 
with noninflammable openings. For all sizes, 
stands on sheltered flats and in moist situations. 
1997S—25t-5 
