FIRE EFFECTS
SPECIES: Schizachyrium scoparium | Little Bluestem 



IMMEDIATE FIRE EFFECT ON PLANT : 
Little bluestem is minimally affected by fire if burned dormant.  It
increases or only slightly decreases in frequency following
dormant-season fires [8,45,84,157].  Spring and winter fires consume
aboveground plant parts in proportion to the amount of moisture in the
standing dead material and in the soil.  In Nebraska, Bragg [14]
reported that about 98 percent of aboveground biomass was consumed by
April fires, while 84 percent of aboveground biomass was consumed by
fire in June when plants were moist and actively growing.  Results from
prescribed fire in late spring in South Dakota indicate that as soil and
fuel moisture content at the time of ignition increases, the amount of
aboveground vegetation consumed decreases [156].  Fires in areas with a
soil moisture content of 33 percent and a fuel moisture content of 30
percent consumed 47.2 percent of little bluestem aboveground biomass.
However, fire in areas with a soil moisture content of 46 percent and a
fuel moisture content of 45.6 percent consumed only 31.4 percent of
aboveground biomass.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
Most often exhibiting a bunch habit, the plant crown of little bluestem
is relatively resistant to fire under moist conditions [141].  Under dry
conditions, fire can burn the crowns more easily, injuring basal buds
that are below the soil surface during dormancy [159].  During summer
little bluestem is particularly succeptible to fire damage because
apical meristems are elevated about 1 inch (2.5 cm) above the soil
surface [15] and therefore exposed to the fire's flames and heat [159].
Late summer fires in Oklahoma resulted in little bluestem suffering 58
percent basal area reduction on plots with low fuel quantities and 95
percent reduction on plots with high fuel quantities [47].  Within 2
months, regrowth, which was minimal, came from surviving tillers.  Few
new tillers were initiated.  Although some ecotypes have small
inconspicous rhizomes, information concerning sprouting via rhizomes
following fire is lacking.


PLANT RESPONSE TO FIRE : 
Fires occurring during fall or spring when plants are dormant generally
consume aboveground foliage, but new growth resumes in the spring as
usual.  The extent to which seed contributes to revegetating postburn
stands is unknown, but Ehrenreich and Aikman [42] reported that seeds
from burned stands have higher germination percentages than seeds from
nearby unburned stands.  Little bluestem plants burned when dormant
generally start growth earlier in the spring and produce more herbage
than plants on nearby unburned areas.  Early resumption of spring growth
has been observed during the first growing season following late spring
burns in Iowa [43] and South Dakota [156], an early spring burn in
Missouri [84], and an October lightning-caused fire in Nebraska [99].
Earlier and increased growth is most often attributed to increased solar
radiation reaching the soil following the removal of standing dead
material [45,67,106].  As a result of increased solar radiation, soil
temperatures on burned areas are higher than on unburned areas [32].
Following spring burning in native bluestem prairie in Missouri, soil
surface temperatures on burned areas compared with unburned areas
averaged 7.1 degrees Fahrenheit (3.9 deg C) warmer in April, 11.4
degrees Fahrenheit (6.3 deg C) warmer in May, 8.3 degrees Fahrenheit
(4.6 deg C) warmer in June, and 7.1 degrees Fahrenheit (3.9 deg C)
warmer in July [84].  Increased soil temperatures promote earlier root
growth and activity, and thus earlier emergence of shoots.

Numerous authors have reported increases in flowerstalk abundance (up to
1200 percent) following spring burning in tallgrass prairie
[30,45,67,84,112].  These increases are attributed to increased nitrogen
availability and to the removal of the litter layer around the growing
points, which increases the amount solar radiation received [67,106].
Long-term observations indicate that increases in flowerstalk and
herbage production are short-lived.  Following spring burning in Iowa,
flowerstalk production increased dramatically the first growing season
but returned to normal by the third growing season [45].  Stem density
declines as the amount of standing dead material increases.  In eastern
Kansas, little bluestem shows a linear decrease in abundance with time
since burning [54].  When little bluestem's abundance was compared on
grasslands with different burning frequencies, its greatest abundance
was on stands annually burned.  In the Kansas Flint Hills, Towne and
Owensby [141] observed that on plots burned annually 48 out of 56 years
before 1982, total herbage production of little bluestem was greatest in
1981 (compared to the previous 56 years), indicating long-term annual
burning is not detrimental to little bluestem.


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
Postburn frequencies indicate that little bluestem's response to fire is
influenced most by the season of burn and by the mean annual
precipitation (MAP) of the burned area.  When precipitation is normal or
above normal, little bluestem generally increases after spring burns in
the tallgrass prairie where precipitation is normally greater than 20
inches annually.  An exception is the Flint Hills of Kansas, which
receive about 30 inches (75 cm) of MAP.  Here late spring burning
neither increased nor decreased yields, but mid or early spring burning
reduced yields significantly [8,109].  In other areas of the tallgrass
prairie, yield increases greater than 100 percent have been observed the
first year following late spring burns in North Dakota [79], Minnesota
[134], Missouri [84], and Iowa [44].  Farther west in the mixed-grass
prairie, little bluestem is stimulated by fires only in areas receiving
over 16 to 20 inches (40-50 cm) of MAP during years with above normal
precipitation [11,158].  In the Black Hills of South Dakota, which
receive 15 to 17 inches (38-43 cm) of MAP, a late spring burn (May 27)
increased little bluestem yields by 31 percent [126].  In the
mixed-grass prairie, burning followed by periods of below normal
precipitation decreases yields compared to unburned stands [9,157].
Late spring burning, when warm-season grasses are about to resume
growth, appears to be most beneficial to little bluestem.


FIRE MANAGEMENT CONSIDERATIONS : 
Late spring appears to be the best time for burning little bluestem
stands.  Late spring fires have yielded the greatest increases in little
bluestem abundance [6,8,15,79,84].  The later the burn occurs in the
spring (just prior to the emergence of green shoots), the greater the
herbage production will be following burning.  If burning is too early,
lower production may result, due to increased evaporation of soil
moisture in the interval between the fire and the resumption of new
growth.  Soil is exposed for least amount of time following late spring
fires; therefore soil moisture levels over the growing season are
reduced less after late spring burns than after winter, early spring, or
mid-spring burns [6,95].

For grazing purposes, late spring burning can be used to increase grass
productivity and improve cattle use in areas receiving over 16 to 20
inches (40-50 cm) of annual precipitation.  Grazing distribution may be
improved because cattle prefer grasses on burned areas over grasses on
unburned areas [87].  Anderson and others [8] observed increased steer
weight gains on late spring burns in Kansas, and improved range
condition due to an increase in warm-season grasses.  Chemical analysis
of little bluestem following annual spring burning on April 10 in Kansas
shows that its nutrient value increased slightly.  When sampled in July,
plants from burned stands had a protein content of 6.3 percent compared
to 5.7 percent for plants from unburned stands [130].  Chapin and
Van Cleve [23] observed a 10 percent increase in nitrogen, 11 percent in
phosphorus, and 10 percent in calcium 3 months after burning.

Late spring burning can be used to increase little bluestem and other
warm-season grass composition in warm-season pastures or rangelands
infested with undesirable cool-season grasses such as Kentucky
bluegrass.  Late spring burning favors warm-season grasses because they
are dormant at the time of ignition, resuming growth from stored food
reserves held in underground organs.  Cool-season grasses are harmed,
since they begin spring growth earlier and are actively growing at the
time of burning.

Related categories for Species: Schizachyrium scoparium | Little Bluestem