FIRE EFFECTS
SPECIES: Poa cusickii | Cusick's Bluegrass 



IMMEDIATE FIRE EFFECT ON PLANT : 
Data on the immediate effects of fire on Cusick's bluegrass are not
available.  The effects of fire on Cusick's bluegrass are probably
comparable to those observed on mutton grass, a closely related and
morphologically similar species [35].  Mutton grass is unharmed to
slightly harmed by light-severity fall fire [11,45,46,50].  Mutton grass
appears to be harmed by and slow to recover from severe fire [54,55].

Pedestalling increases the susceptibilty of bunchgrasses to fire.  When
grasses are elevated, new tillers are no longer insulated from fire by
the soil [37,52].  Cusick's bluegrass plants that have become
pedestalled by local erosion may be severely damaged or killed by fire,
although fuels at such sites may be too patchy to support fire spread.
Overgrazed Cusick's bluegrass rangelands are characterized by 25 to 45
percent bare ground and pedestalled Cusick's bluegrass plants [43].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Most information on Cusick's bluegrass response to fire is anecdotal
[20,51,52,53].  Cusick's bluegrass recovery from fire is reported as
"moderately rapid" [20] to "very rapid" [52,53].  Least damage occurs
with late summer or fall fire when Cusick's bluegrass is dormant.  Most
damage is thought to occur from spring fire that occurs after plants
have started growth [53].

Wildfire in mid-August, 1973, reduced vegetative growth and reproduction
of Cusick's bluegrass for at least 3 years.  The wildfire burned through
a portion of a bluebunch wheatgrass-Thurber needlegrass (Stipa
thurberiana) community on the Arid Lands Ecology Reserve in
south-central Washington.  An unburned portion of the community (fire
excluded for at least 30 years) was used as a control.  Basal area was
reduced by 42 percent the first year after fire and remained reduced for
all 3 postfire years on the burned site [40,42].  Leaf length,
flowerhead length, and number of flowering culms were reduced the first
year after fire.  In postfire year 2, the number of flowering culms per clump
was much greater than that on an unburned stand.  By postyear 3, leaf
length and the number of flowering culms equalled plants on the unburned
stand.  These results are similar to those from an earlier study in
southern Idaho [26].

A comparison of Cusick's bluegrass on burned and unburned control plots
for postfire years 1 to 3 follows.  Data are means (standard errors)
[40,41,42].

                           1974  
________________________________________________________
|                               Burn         Control   |
|                           ___________    ___________ |
|live herbage (g/sq m)        2.4 (1.1)      4.2 (3.8) |
|dead herbage (g/sq m)          0            3.8 (3.4) |
|leaf length (cm)          **14.1 (0.2)     21.9 (0.2) |
|basal area (sq cm)       **219.9 (23.3)   381.7 (35.5)|
|culm length (cm)            46.6 (0.8)     46.9 (0.6) |
|flowerhead length (cm)     **5.7 (0.1)      6.4 (0.1) |
|Number of flowering        **4.3 (0.9)      9.5 (1.6) |
|  culms/clump                                         |
|clumps with flowering         **67             72     |
|  culms (%)                                           |
|______________________________________________________|

                           1975 
________________________________________________________
|                                Burn        Control   |
|                            ___________   ___________ |
|live herbage (g/sq m)        1.5 (1.4)      2.4 (2.0) |
|dead herbage (g/sq m)        0              1.0 (0.7) |
|leaf length (cm)          **17.5 (0.1)     20.2 (0.2) |
|basal area (sq cm)       **183  (20)      324  (29)   |
|culm length (cm)          **43.4 (0.5)     36.9 (1.4) |
|flowerhead length (cm)     **5.8 (0.1)      6.8 (0.2) |
|number of flowering        *17.5 (4.3)      4.3 (1.0) |
|  culms/clump                                         |
|clumps with flowering         **69             31     |
|  culms (%)                                           |         
|______________________________________________________|

                           1976
________________________________________________________
|                                Burn        Control   |
|                            ___________   ___________ |
|live herbage (g/sq m)        *0.3 (0.2)     4.1 (2.0) |
|dead herbage (g/sq m)        *0.4 (0.2)     5.5 (2.3) |
|leaf length (cm)           **18.5 (0.2)    19.2 (0.2) |
|basal area (sq cm)        **169  (16)     285  (22)   |
|culm length (cm)             41.9 (0.5)    42.5 (0.5) |
|flowerhead length (cm)      **5.6 (0.1)     6.5 (0.1) |
|number of flowering           8.5 (1.6)     7.8 (1.5) |
|  culms/clump                                         |
|clumps with flowering            60            65     | |  culms (%)                                           |
|______________________________________________________|
 *Significantly different from unburned plot (p < 0.05)
**Significantly different from unburned plot (p < 0.01)


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Repeated prescribed fire is recommended for reducing sagebrush (Artemsia
spp.) on sagebrush/Cusick's bluegrass rangelands in eastern Oregon.
Kovalchik [18] reported that on big sagebrush-silver sagbrush/Cusick's
bluegrass communities that are in fair or better condition, repeated
prescribed fire greatly decreases big sagebrush cover and increases
cover of Cusick's bluegrass.  Silver sagebrush cover is not reduced as
much as big sagebrush cover because silver sagebrush sprouts, but silver
sagebrush decreases at least somewhat as Cusick's bluegrass increases in
vigor [18].

Considering Cusick's bluegrass meadows of eastern Oregon, Volland [43]
wrote that, "Nothing is known about the effect of prescribed burning on
this plant community."  Because it is nonrhizomatous, Cusick's
bluegrass may decline at the expense of Kentucky bluegrass, which is
rhizomatous and common in Cusisk's bluegrass communities.  Volland
cautioned that if Cusick's bluegrass meadows are burned, they should be
protected from grazing for at least one growing season after fire.

Related categories for Species: Poa cusickii | Cusick's Bluegrass