FIRE EFFECTS
SPECIES: Tsuga heterophylla | Western Hemlock 



IMMEDIATE FIRE EFFECT ON PLANT : 
Western hemlock is commonly killed by fire.  High-severity fires often
destroy all western hemlock [24].  After a severe crown fire at Olympic
Mountain, Washington, overstory western hemlock suffered 91 percent
mortality [4].  Even light ground fires are damaging because the shallow
roots are scorched [57].  Postburn mortality of western hemlock is
common due to fungal infection of fire wounds [29]. Most western hemlock
seedlings are killed by broadcast burning [27,64].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Burning may or may not benefit natural regeneration of western hemlock.
The response of seedlings to burning varies according to aspect, slope,
latitude, climate, etc.  After broadcast burning in coastal hemlock
zones, more seedlings were found in burned areas than in unburned areas
due to elimination of brush competition and reduction of dense patches
of slash [76].  On Vancouver Island after the third growing season,
burned seedbeds had 58 percent more seedlings with better distribution
than unburned seedbeds [57].  However, on a site near Vancouver, British
Columbia, due to sunscald, all new germinants on burned humus were dead
by mid-July [76].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Fire danger increases with the increasing volume of logging residue.
Logging old-growth stands or western hemlock can leave huge volumes of
residue compared with logging young stands, which leave little residue.
Burning cleans up the area and facilitates planting.  Therefore burning
is often favored by land managers who intend to plant Douglas-fir to
obtain a mixture of Douglas-fir and western hemlock.  The general trend
in western hemlock management, however, is away from broadcast burning
except where a huge accumulation of residues constitutes a fire hazard
[64].

Burning in western hemlock stands is a valuable treatment when seedlings
and saplings are infected with dwarf mistletoe and need to be destroyed.
Fire is helpful in rehabilitation of brushy areas; burning brush to
ground level facilitates planting and favors planted seedlings in
keeping ahead of the brush sprouts [64].

Fire spreads more slowly in western hemlock slash than in western
redcedar slash.  Western hemlock slash drops its foliage.  The slash of
western hemlock is less flammable when chipped [52]. Slash from western
hemlock/western redcedar/Alaska-cedar forests produce greater nutrient
losses to the atmosphere when the slash composition has a greater
proportion of Alaska-cedar and western redcedar.  One can expect smaller
nutrient losses when western hemlock makes up the majority of the slash
[28].  For further details on burning of western hemlock slash refer to
the fire case study in the Alaska-cedar Fire Effects Information System
species writeup.

Related categories for Species: Tsuga heterophylla | Western Hemlock