FIRE EFFECTS
SPECIES: Muhlenbergia montana | Mountain Muhly 



IMMEDIATE FIRE EFFECT ON PLANT : 
Mountain muhly culms and leaves are probably killed by fire.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Mountain muhly density generally decreases from prefire values during
the first few years after fire [31,62], but it may increase over
original values thereafter [4].  Mountain muhly usually takes at least 3
years to fully recover from fire [31].  However, after prescribed fire
in central Arizona, mountain muhly had recovered prefire biomass within
10 months [35].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
In central Arizona mountain muhly was sampled in September 1981, on
sites that previously had been prescribed burned in ponderosa pine pole
timber and mature stands.  Thinning treatments and grazing management
varied from site to site.  All burned sites were matched with similar,
unburned controls.  The following mountain muhly production (kg/ha)
means were reported [4]; standard errors are in parentheses:

                         Ponderosa Pine Pole Stands

                 2 yr burn         5 yr Burn         7 yr burn

Burn            0.21 (0.06)*      0.60 (0.22)       4.56 (1.06)*
Control         1.60 (0.82)*      0.28 (0.12)       1.22 (0.38)*
 
                         Mature Ponderosa Pine Stands

Burn            0.88 (0.30)       0.16 (0.15)       0.84 (0.27)
Control         8.24 (4.20)       0.10 (0.05)       0.67 (0.20)

* Indicates significant difference (p<.05) between burn and control.

In 2-year-old burns, mountain muhly production was less than on control
sites.  In 5- and 7-year-old burns, mountain muhly production was
greater than on control sites [4].

In central Arizona mountain muhly occurred on an area that was
prescribed burned October 18 and 19, 1977.  Mountain muhly density was
sampled before the fire, in 1974, and again after the fire, in 1980.
Backfires and short strip headfires were used; estimates of fuel
consumption ranged from 50 to 75 percent.  Most ponderosa pine
regeneration was not killed.  Mountain muhly density was 1.01 stems per
square meter in 1974.  In 1980, after the fire, stem density was zero
[62].

In central Arizona mountain muhly biomass and nutrient concentrations
were measured during the first growing season after burning on plots in
a ponderosa pine/Arizona fescue habitat type.  The stand had been
unburned since a fire in 1876.  The overstory consisted of uneven-aged
ponderosa pine distributed in even-aged groups of mature trees, poles,
or saplings.  Mountain muhly was dominant in the herbaceous vegetation
within openings.  Controlled burning occurred in November 1976.  The
fire consumed surface needles on 94 percent of the area, and exposed
mineral soil on 16 percent of the area.  Fuels less than 1 inch (2.54
cm) in diameter were reduced 63 percent.  Fuel reduction was greatest
under mature trees, where fuel loads were heaviest; it was intermediate
in pole stands, and least in sapling stands.  Mountain muhly standing
crop was sampled on 11 burned and 7 unburned plots during June and
September of postfire year 1.  Mountain muhly standing crop and measured
nutrient concentrations (% oven-dry weight) were as follows 7 months
after fire [35]:

                                    June 1977

             Mature Timber             Pole                Sapling

           Unburned   Burned     Unburned   Burned     Unburned   Burned

Standing      
  Crop          
  (kg/ha)     3.97     3.26         2.18*    0.47         0.26     2.09
N  (%)        0.99     1.19         1.02*    1.31         1.07     1.15
P  (%)        0.25*    0.35         0.28*    0.34         0.27     0.32
K  (%)        0.69*    0.82         0.68*    0.82         0.62*    0.82
Ca (%)        0.13*    0.18         0.14*    0.19         0.14*    0.18
Mg (%)        0.10*    0.14         0.12     0.14         0.12     0.12

* Indicates significant difference (p<.05) between burned and unburned
    sites withing a stratum.

By 10 months after fire, no significant differences in standing crop
were found between unburned and burned plots, and few significant
differences in nutrient concentrations persisted [35].


FIRE MANAGEMENT CONSIDERATIONS : 
Mountain muhly is a principal grass in some ponderosa pine/grass types
where recurring fires have maintained savanna.  In north-central
Arizona mountain muhly will usually carry surface fires in November,
and perhaps during the winter and spring [11].

In the Santa Catalina Mountains of Arizona, decades of fire protection
have resulted in many ponderosa pine stands with a dense undergrowth of
ponderosa pine saplings.  In the 1960's, an inventory of ponderosa pine
stands burned within the past few decades revealed that those burned by
lightning-caused fires, which occur at a relatively high frequency in
the range, were primarily open and parklike, with an herb layer
dominated by mountain muhly.  However, intensity of a major incendiary
fire was so severe that it killed all ponderosa pines in the stand and
enhanced development of oak (Quercus spp.) scrub, which shaded out
mountain muhly [61].

In ponderosa pine/bunchgrass forests in Arizona and New Mexico, fires
applied every decade to reduce fuel and thin tree seedlings will
maintain ponderosa pine/bunchgrass savanna [58].

Related categories for Species: Muhlenbergia montana | Mountain Muhly