FIRE ECOLOGY
SPECIES: Larix occidentalis | Western Larch 



FIRE ECOLOGY OR ADAPTATIONS : 
Adaptations to Fire:  Western larch is the most fire-resistant tree
species in the northern Rocky Mountains and interior Pacific Northwest.
It has very thick bark containing little resin, a high and open
branching habit, deep roots, and low-flammability foliage
[32,33,82,139].  At ground level the bark is often 6 inches (15.2 cm)
thick on mature trees [4].  The tendency of western larch to self-prune
lower branches and its tolerance of defoliation add to its fire
tolerance [30,19].  Fire favors the establishment of western larch
because it quickly invades openings, grows rapidly, and needs full
sunlight [152,113].  Western larch is very long-lived and able to
survive until fire creates a suitable seedbed [5,30].

Fire Regimes:  In the northern Rocky Mountains, the results of a number
of studies suggest two distinct fire regimes for stands with western
larch as a seral dominant [6].  On relatively dry sites, usually with
Douglas-fir or Engelmann spruce as potential climax dominants, the
natural fire regime was one of fairly short mean fire intervals of 20 to
75 years.  These intervals were shortened by recurring low- to
medium-intensity surface fires.  On moist sites that included grand fir,
western hemlock, and western redcedar as potential climax species, fires
were severe stand-replacing burns at 120- to 350-year intervals
[2,3,6,18].  The interval between stand-replacing fires was over 100
years under both of these fire regimes [6].

In lower and drier mixed conifer communities in the Blue Mountains of
Oregon, the mean fire frequency of low surface fires before protection
was about every 10 years [46].  In the same area in drier Douglas-fir
and grand fir habitat types, the mean fire frequency of underburns was
20 to 30 years [116].  In higher elevation communities in this region,
severe crown fires occurred at 100- to 300-year intervals, allowing
western larch, lodgepole pine, and western white pine (Pinus monticola)
to dominate large stands [121].

Fuels:  In the larch-Douglas-fir type of western Montana, fuel loading
ranges from 1.4 tons per acre (3.1 MT/ha) to 73.9 tons per acre (165.7
MT/ha) [29].  The following mean fuel loads were described for a study
in the western larch cover type in western Montana [119]:

                        Tons per Acre        Metric Tons per Hectare

Total fuels                  22.5                     50.4
Small fuels (0.25-3           3.6                      8.1
inches [0.6-7.6 cm])
Large fuels (>3 inches       17.7                     39.7
[.7.6 cm])
Duff                          1.2                      2.7


POSTFIRE REGENERATION STRATEGY : 
   crown-stored residual colonizer; short-viability seed in on-site cones
   off-site colonizer; seed carried by wind; postfire years one and two

Related categories for Species: Larix occidentalis | Western Larch