FIRE EFFECTS
SPECIES: Philadelphus lewisii | Lewis' Mockorange 



IMMEDIATE FIRE EFFECT ON PLANT : 
Lewis' mockorange is top-killed by fire, but the root crown usually
survives and produces sprouts [10,23,24].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Lewis' mockorange sprouts vigorously from the root crown following fire
[10,23,24].  After an April fire on a south-facing slope in
north-central Idaho, Lewis' mockorange increased to prefire densities by
the third postfire growing season [22].

The following two studies have investigated the sprouting response of
Lewis' mockorange to fire.

Seral brushfields within the grand fir (Abies grandis)/pachistima
(Pachistima myrsinites) habitat type in northern Idaho were burned in
either spring (late March - early April) or fall (October).
Temperatures during the fires ranged from 67 to 78 degrees Fahrenheit
(19-26 deg C), and relative humidities ranged from 25 to 48 percent.
Lewis' mockorange on sites burned in October did not sprout until the
following April.  Lewis' mockorange on the spring-burned sites sprouted
4 to 8 weeks after the fire.  Twenty completely top-killed Lewis'
mockorange (eleven on the fall burned sites and nine on the spring
burned sites) were measured at the end of the first postfire growing
season [24]:

                                       Fall Fires       Spring Fires

Average crown diameter (ft)     
   prefire                             4.7 (143 cm)     4.7 (143 cm)
   postfire                            2.4 (73 cm)      2.2 (67 cm)

Average crown height (ft)
   prefire                             8.8 (268 cm)     9.6 (293 cm)
   postfire                            4.1 (125 cm)     3.7 (113 cm)

No. basal sprouts per plant
   prefire                             1.5              0.6
   postfire                           38.0             28.9

Average postfire sprout height (ft)    2.4 (73 cm)      2.1 (64 cm)

A multiple regression equation is presented which relates the number of
postfire basal sprouts to prefire crown height, crown diameter, and
crown volume [24].

In another study in north-central Idaho, a brushfield was burned three
times at 5-year intervals (31 March 1965, 3 May 1970, and 14 May 1975).
Maximum air temperatures during the fires were 77, 81, and 88 degrees
Fahrenheit (25, 27, and 31 deg C), and relative humidities at 4:00 pm
were 35, 16, and 27 percent, respectively.  Leaves on shrubs and
succulent herbaceous growth depressed the fire in 1975.  A single Lewis'
mockorange was followed during the study.  The plant was dormant during
the first fire, but leaves were beginning to emerge at the time of the
second fire and were completely emerged at the time of the third fire.
With each successive fire, average sprout height decreased.  Reduced
growth following the second and third fires may have resulted from the
advanced phenological stage at the time of those fires.  Sprout height
and number were measured the first growing season following each fire.
Crown height and diameter were measured during the second postfire
growing season [23].

             No. basal sprouts          Average sprout height (ft)
  1965               14                         2.0 (61 cm)
  1970               19                         1.5 (46 cm)     
  1975               16                         1.0 (30 cm)


                  Crown height (ft)         Crown diameter (ft)
  prefire            7.0 (213 cm)               1.5 (46 cm)

  1966               4.0 (122 cm)               2.0 (61 cm)
  1971               2.5 (76 cm)                2.0 (61 cm)
  1976               2.5 (76 cm)                1.5 (46 cm)



DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Lewis' mockorange palatability increases following fire.  After a spring
fire in northern Idaho, utilization of Lewis' mockorange by Rocky
Mountain elk was significantly (p<0.05) greater on recently burned sites
than on adjacent unburned sites [21].

                     % of available twigs browsed

                    1st season         2nd season 
      
Control                 1.3                0.6 
Burn                   36.3               30.0

Allometric equations, which can be used to estimate fuel quantities,
have been developed for Lewis' mockorange.  The equations use basal stem
diameter to estimate foliage biomass and total biomass [5].

Related categories for Species: Philadelphus lewisii | Lewis' Mockorange