FIRE EFFECTS
SPECIES: Thuja occidentalis | Northern White-Cedar 



IMMEDIATE FIRE EFFECT ON PLANT : 
Northern white-cedar is usually killed by surface fire.  Large trees may
survive if ground cover is sparse.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Northern white-cedar becomes established by seed on recently burned
sites if a seed source is nearby and the exposed soil is moist
[14,34,47].  Fire serves to remove competition and also removes the moss
layer that dries out in the summer and results in seedling mortality
[31].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed fire is recommended after northern white-cedar harvest unless
there is ample advance regeneration or if the organic soil is
unsaturated.  Fire removes the heavy slash that prevents regeneration
and also prepares a favorable seedbed [27,46].  However, deep ground
fires can start if the soil is not saturated [27].

If removing slash is the primary objective, prescribed fires are usually
conducted under the following conditions:  3 to 10 days after a rainfall
of more than 0.1 inch (0.3 cm), a minimum relative humidity of 30 to 60
percent, a maximum air temperature of 60 to 90 degrees Fahrenheit (16-32
deg C), and a maximum wind speed of 5 to 15 miles per hour (8-24 km/h).
If the objective is to remove slash and prepare a seedbed, the fire must
be hotter and is usually conducted under the following conditions:  at
least 7 days since a rainfall of more than 0.1 inch (0.3 cm), less than
45 percent relative humidity, air temperatures greater than or equal to
80 degrees Fahrenheit (27 deg C), and 5 to 15 miles per hour (8-24 km/h)
wind speed [27].

The effect of three different slash treatments on northern white-cedar
regeneration after winter clearcutting was investigated.  The treatments
were (1) a prescribed broadcast fire in August to burn the slash, (2)
skidding entire trees out of the study area and delimbing elsewhere, and
(3) leaving the slash in place.  Five growing seasons after
clearcutting, northern white-cedar less than or equal to 23.6 inches (60
cm) tall averaged 33.3 stems per miliacre (8.2 stems/sq m) on burned
plots, and 11.5 and 22.2 stems per miliacre (2.8 and 5.5 stems/sq m) on
full-tree skidded and slash-left plots, respectively.  Ten growing
seasons after clearcutting, northern white-cedar had increased to 40.2
stems per miliacre (9.9 stems/sq m) on burned plots but showed no change
on the other treatment plots [46].

Northern white-cedar slash is a fire hazard for 20 to 30 years because
of its resistance to decay [42].

Prescribed fire can be used to eliminate northern white-cedar that
invades fens in the absence of fire.  A low intensity fall fire (rarely
exceeding 70 BTU/sec/sq ft) resulted in a statistically significant
reduction in the percent cover of northern white-cedar for three
postfire growing seasons.  Annual prescribed burning is recommended for
restoring fens [40,41].

Related categories for Species: Thuja occidentalis | Northern White-Cedar