FIRE EFFECTS
SPECIES: Artemisia californica | California Sagebrush 



IMMEDIATE FIRE EFFECT ON PLANT : 
Light-severity fire top-kills California sagebrush; severe fire causes
plant mortality [45,84,86].  The effect of moderate-severity fire is not
well documented.  Shallowly buried seed is often killed by fire [50].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Because California sagebrush seeds are fire sensitive and their seedbank
numbers moderate, seedling density may by low in the first postfire year
[41,50].  California sagebrush seedling density following a wildfire in
chamise chaparral near Pasedena was 0.25 per square foot (2.69/sq m),
while density in adjacent unburned chaparral was 0.34 per square foot
(3.67/sq m) [83].

Seedling recruitment is usually good after the first postfire year.
Population buildup is most rapid when fires are not severe and
top-killed plants consequently sprout.  Sprouts usually flower at
postfire year 1, although flowering is sometimes delayed until postfire
year 2 [42,84,86].  Seed resulting from sprout flowering, in addition to
windblown seed disseminated to burn areas, results in favorable seedling
establishment beginning at postfire year 2 or 3.  Sauer [74] reported a
California sagebrush seedling frequency of 12 percent in Big Sycamore
Canyon 3 years following the Mugu Fire in the Santa Monica Mountains.
He also reported a frequency of 12 percent for seedlings 3 years after
the nearby Topanga-Tuna Canyon Fire.  Crown density recovers to preburn
levels by postfire year 10 in coastal sage scrub unless the site is poor
or severe soil erosion occurs [38].

In a study comparing adjacent coastal sage scrub and bigpod
ceanothus-dominated chaparral communities at postfire year 26, Gray [20]
found that 33 percent of California sagebrush in coastal sage scrub
appeared to have resulted from crown sprouting, while 10 percent of
California sagebrush in chaparral appeared to have done so.  All
California sagebrush plants in the chaparral community were dead.
Density of California sagebrush in coastal sage scrub was 0.012 plants
per square foot (0.13/sq m).


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
California sagebrush seedlings may sprout when aboveground portions of
seedlings are damaged.  Coastal sage srub and chaparral communities
rarely burn in consecutive years, but unusual circumstances may trigger
this plant response. Germination of California sagebrush seed following
an arsonist-set fire on August 1979 on Otay Mountain, San Diego County,
resulted in a seedling density of 0.24 plants per square foot (2.62/sq
m) at postfire year 1.  In July 1980, another arsonist-set fire occurred
at the same site.  Fifteen percent of California sagebrush seedlings
established after the 1979 fire sprouted following the 1980 fire [92].


FIRE MANAGEMENT CONSIDERATIONS : 
Fire suppression in coastal sage scrub has been generally successful
during summer months but not during extreme conditions of high
temperature accompanied by Santa Ana winds in fall.  In areas where fire
suppression has been successful yearround, delayed burning has resulted
in the burning of abnormally large areas during the abovementioned
weather conditions [49].  In other areas, fire intervals have increased
due to human-caused fires.  Because coastal sage scrub is generally
closer to developed areas than is chaparral, it is more vulnerable to
accidentally- and arsonist-set fire.  Analysis of the fire history of
coastal sage scrub on Burton Mesa near Lompoc revealed that all of the
27 fires occurring between 1938 and 1986 were started by humans.  Only
eight of these fires were prescribed.  The wildfires occurred in fall
and spread in the direction of southwesterly-blown Santa Ana winds.
These wildfires were arrested or extinguished at roads, fields, or
firebreaks [13].  Zedler [89] stated that the current high fire
frequencies of some coastal sage scrub communities may not be natural
and that some suppression may be neccessary in these areas to restore
presettlement ecological conditions.

The long-term effect of fire suppression on California sagebrush and
other coastal sage scrub species is unclear.  Some authorities suggest
that coastal sage scrub under the public domain is expanding in size by
invasion into adjacent communities.  Epling and Lewis [15] state that
California sagebrush and other coastal sage scrub species are
successfully invading chaparral dominated by sprouting species because
unusually hot, stand-replacing fires occurring as a result of fuel
buildup have killed such sprouting species.  Thomas [77] reported that
California sagebrush in coastal sage scrub of the Santa Monica Mountains
National Recreational Area is invading adjacent valley oak (Quercus
lobabta) woodland.  A computer model, however, indicates that the
shortened fire frequencies common to many coastal sage scrub areas will
result in the disappearance of California sagebrush and other weakly
sprouting, nonobligate seeders from that community.  This model suggests
that given a fire interval of 30 years or less, California sagebrush
will be absent from coastal sage scrub after 100 years.  There is
therefore some concern that California sagebrush may be declining in
numbers [49].  Field studies comparing area of expansion and decline of
coastal sage scrub because of fire are lacking.  Modern fire regimes may
result in no net loss of coastal sage scrub or California sagebrush.
Managers practicing prescribed burning should be aware, however, that
California sagebrush populations may require longer fire intervals than
have been proposed for hazard reduction [49].  Because of the less
intense heat generated by spring burning of coastal sage scrub and
chaparral [22], it may be the most favorable season in which to burn
California sagebrush if consequent sprouting is desired.  Special
measures such as seeding may eventually be neccessary following burning
during other seasons in order to insure continuance of California
sagebrush populations.

Firebreaks and fuelbreaks are easily constructed in coastal sage scrub,
and are easily maintained by mechanical, herbicide or other treatment
[49].  In a 4-year study, Green and Newall [24] successfully used goats
to control growth of California sagebrush and other plants on fuelbreaks
on the Los Padres National Forest.  Considerations for development of a
fire prescription in coastal sage scrub and chaparral communities are
available in the literature [22,23].

Related categories for Species: Artemisia californica | California Sagebrush