FIRE EFFECTS
SPECIES: Symphoricarpos occidentalis | Western Snowberry 



IMMEDIATE FIRE EFFECT ON PLANT : 
Western snowberry is top-killed or killed by severe fires [4,5,60,94].
In the northern Great Plains, "hot" fires in late summer and early fall
have severely burned roots of western snowberry [60].  In Minnesota in a
partially burned colony of western snowberry, all stems were killed and
all stem bases charred.  By the fall of the same year, an average of 2.5
sprouts per stem base was observed [94].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Western snowberry sprouts from the root crown following fire [100].
Several studies have reported rapid recovery and postfire increases in
western snowberry densities [5,11,43,100], although decreases have been
reported [3,4,11,45].  In quaking aspen parklands in Alberta, western
snowberry sprouted 2 weeks after spring fire; by 3 months its canopy
cover was greater on burned sites than on control plots [5].  In
Saskatchewan a prescribed fire occurred in October 1976 in native fescue
grassland; western snowberry was top-killed.  By postfire year 1,
western snowberry live stem density was similar in burned and unburned
areas [97].

In North Dakota an October 1976 fire burned mixed-grass prairie and
wooded draw plant communities.  Average densities (stems/sq m) of
western snowberry in the summers of 1977 and 1978 were higher on burned
than unburned transects in wooded draws [142]:

                           1977     1978

lower draw-burned          41.2     31.5
upper draw-burned          68.6     38.8
unburned                   ----     12.5

In Saskatchewan eight prescribed fires were set from October 1986 to
April 1988 to reduce western snowberry encroachment into native
grassland.  Two plots were burned with headfires at each of the
following times:  mid-October 1986, mid-October 1987, early May 1987,
and late April 1988; two additional blocks were left as control sites.
All plots were monitored for 4 years after burning.  Average western
snowberry stem densities (stems/sq m) were higher on burned than
unburned plots [100]:

growing season       control     autumn     spring     standard error

prefire                36          39         38             8.1
postfire year 1        39a*        72ab      122b           14.6
postfire year 2        43a         67ab      111b           12.3
postfire year 3        46          62         95            12.9
postfire year 4        46          57         51             5.5

*Different letters within a year indicate means are significantly
different (P< or =0.05).  A similar letter or no letter within a year
indicates means are not significantly different (P> or =0.05)

Western snowberry density was significantly greater on spring-burned
plots than on autumn-burned or control plots.  

In Alberta two prescribed burns were conducted on May 8, 1970 and May
11, 1971.  Western snowberry was the dominant shrub on unburned sites.
All western snowberry stems were killed by the fires, but plants started
sprouting 2 weeks after fire.  Stem densities (stems/sq m) for western
snowberry during three growing seasons following spring 1970 burning
were as follows [5]:

year     unburned     burned
 
1970       86           236
1971       65           199  
1972       66           170

Western snowberry stem densities increased significantly (P<0.05)
following fire.


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
In South Dakota a May 1, 1974 prescribed fire was conducted in native
grassland.  Stem density (stems/sq m) and average height (cm) of western
snowberry were reduced following fire.  Results were as follows [45]:

                     prefire                postfire
                (Ocotber 15, 1973)       (June 28, 1974)

stem density           79                      55
stem height            61                      24

In Alberta early spring burning in fescue grassland was conducted
annually for 24 years.  Stem densities (stem/sq m) were 17.8 and 25 in
burned and unburned areas, respectively.  Frequency and cover of western
snowberry in July 1976 after the last fire were as follows [3,4]:  

                  frequency (%)     cover (%)

unburned              56              31
burned                52               2

Western snowberry canopy cover declined greatly on burned sites, but
frequency and stem density did not change significantly.  

In Minnesota prescribed spring fires were conducted annually from 1983
to 1987.  Western snowberry shoot height decreased from 3.3 to 1.6 feet
(1-0.5 m) on burned sites [11].  
                


FIRE MANAGEMENT CONSIDERATIONS : 
In the absence of fire, western snowberry has become the dominant native
shrub on mixed-grass prairies in the northern Great Plains [111].
Annual burning may restrict expansion of western snowberry colonies onto
native prairie grasslands, whereas periodic burning may enhance the
spread of western snowberry [5,60,94,100].  Periodic burning could
create even-aged, youthful stands of western snowberry, which may be
more productive of wildlife forage and provide better cover [100].  

In North Dakota two prescribed fires in mid-June 1982 and 1984
top-killed most western snowberry.  Unburned vegetation ("skips") within
burn areas mostly occurred in dense patches of western snowberry.
Gadwalls started nesting in these "skips" 4 days after the burns, where
dead stems of western snowberry were still standing [75].

Related categories for Species: Symphoricarpos occidentalis | Western Snowberry