SPECIES: Muhlenbergia porteri
Aleksoff, Keith C. 1999. Muhlenbergia porteri. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ .
No special status
Bush muhly occurs from the southern part of the Great Basin and Intermountain region south to California, Texas and Mexico .
FRES30 Desert shrub FRES34 Chaparral-mountain shrub FRES40 Desert grassland
AZ CA CO NV NM OK TX UT MEXICO
3 Southern Pacific Border 5 Columbia Plateau 6 Upper Basin and Range 7 Lower Basin and Range 10 Wyoming Basin 11 Southern Rocky Mountains 12 Colorado Plateau
KO27 Mesquite bosques K039 Blackbrush K040 Saltbush-greasewood K041 Creosotebush KO42 Creosotebush-bursage KO43 Palverde-cactus shrub K057 Galleta-three-awn shrubsteppe
68 Mesquite 242 Mesquite
211 Creosotebush scrub 212 Blackbrush 501 Saltbush-greasewood 503 Arizona chaparral 506 Creosotebush-bursage 507 Palo verde-cactus 508 Creosotebush-tarbush
Bush muhly occurs in desert grasslands, desert shrub, within and above
interior chaparral, and as an understory component of the Madrean evergreen
woodland in central Arizona. It occurs mainly along drainages in the Great Basin .
Bush muhly is commonly found in association with velvet mesquite (Prosopis velutina), creosotebush (Larrea tridentata) and Joshua tree (Yucca brevifolia). Common grass associates of bush muhly include bristlegrass (Seraria leucopila), plains bristlegrass (S. macrostachya), plains lovegrass (Eragrostis intermedia), cane beardgrass (Bothriochloa barbinodis), green sprangletop (Leptochloa dubia), Arizona cottontop (Digitaria californica), and Lehmann lovegrass (Eragrostis lehmanniana) .
Bush muhly is readily eaten by livestock throughout the year when available; however, it is usually not abundant enough to provide much forage. It is grazed heavily in winter when other species become scarce . Because of its branching habit, it is extremely susceptible to heavy grazing [41,43]. Bush muhly is damaged when continuously grazed to a stubble height of less than 4 inches (10 cm) .
Bush muhly ranges from average to highly palatability
to all classes of livestock, depending on season and precipitation [8,43].
With sufficient moisture, bush muhly may remain green throughout the year
and is especially palatable in the winter and prior to summer rains when
other grasses are dry [22,40,41].
The palatability of bush muhly for livestock and wildlife species in Utah is rated as follows :
Cattle Good Domestic sheep Fair Horses Good Pronghorn Fair Elk Poor Mule deer Poor Small mammals Fair Small nongame birds Fair Upland game birds Poor Waterfowl Poor
Ash 6.6 Crude Fiber 37.3 Ether extract 2.1 N-free extract 46.8 Protein (N × 6.25) 7.2 Calcium 0.39 Phosphorus 0.10
Cover value of bush muhly for wildlife species in Utah is rated as follows :
Small mammals Good Small nongame birds Fair Upland game birds Poor Waterfowl Poor
Compared with other grasses, bush muhly was rated with regard to its potential in rehabilitation work as follows :
Potential biomass production Medium Erosion control potential Medium Establishing requirements Medium Short-term revegetation potential Low Long-term revegetation potential Medium
Grazing: Bush muhly can be very susceptible to heavy winter grazing when it is
green and other plants are scarce . In southern Arizona there was a marked increase
in bush muhly after 4 years of protection from cattle and domestic goat grazing .
When growing beneath shrubs, the shrubs may provide some protection from large
Martin and Morton  report that on the Santa Rita grazing unit near Tucson, Arizona, bush muhly density increased more under yearlong grazing than rotation grazing. The yearlong units received higher rainfall than the rotation units.
Other: Bush muhly increased in size when tebuthiuron was used to kill creosotebush, but bush muhly density remained the same [15,32]. Increased growth of bush muhly was not observed when land imprinting and 2-way railing were used because these mechanical methods did not kill the shrubs. Disking killed most of the bush muhly plants .
In areas where creosotebush is less than 3 feet (1 m) in stature, bush muhly appears to affect the creosotebush detrimentally and in some instances may be responsible for its death by competing for moisture, nutrients, and sunlight .
Bush muhly regenerates by seed. Bush muhly seeds composed about 33% of the seedbank near Globe, Arizona . Milton and others  found that that bush muhly made up the largest portion
of construction material in cactus wren nests, and that the nests
contained viable seeds. They suggested that the cactus wren is an
important diperser of bush muhly seeds, capable of spreading them
as far as 213 feet (65 m).
Bush muhly seedlings, shoots, and roots are all adversely affected by a high temperature regime. In a growth chamber study, Sosebee and Herbel  obtained an optimum germination rate of 84% under a temperature range of 68 to 95 degrees Fahrenheit (20-35 oC) with alternating light and dark periods. Seedling survivorship after 21 days was 94% with maximum soil temperatures of 102 degrees Fahrenheit (39 oC) and 5% with a maximum soil temperature of 122 degrees Fahrenheit(53 oC)). Ashby and Hellmers  concluded that bush muhly germinated best at 86 degrees Fahrenheit (30 oC).
Generally, bush muhly grows on low elevation semidesert grassland ranges
in good condition, as well as in deserts. It occurs on mostly rocky
or sandy sites on lower plains, dry mesas, canyons,
foothills, and open hillsides from 760 to 4,300 feet (230-1300 m). In Colorado it ranges
up to 6,500 feet (1900 m) . Throughout much of its range bush muhly
is often found growing under the protection of shrubs, such as mesquite and
creosotebush, more than in open areas [2,6,10,16,22,27,30,32,43].
Growth of bush muhly on various soil textures in Utah is rated as follows :
Gravel Poor Sand Good Sandy loam Good Loam Good Clay loam Good Clay Fair Dense clay Poor
Bush muhly is considered a climax species . Bush muhly was dominant throughout much of the desert grassland of New Mexico, but is now secondary to fluffgrass (Erioneuron pulchellum), burrograss (Aplopappus tenuisectus), and threeawns (Aristida spp.) . Bush muhly originally existed in extensive stands, but now is generally found growing under the protection of shrubs [10,43]. Bush muhly may decrease greatly on heavily grazed rangeland, but may be a substantial component of mesa rangelands in the process of recovery. Bush muhly is shade tolerant, and survives beneath mesquite canopies .
Bush muhly begins growth from late winter to early spring and flowers from early spring to early summer
[22,25,27]. Given sufficient moisture, bush muhly does not back to the root crown in winter, and new growth starts from near the base of the previous year's stems [22,30]. Phenology of bush muhly in the northern Chihuahuan Desert of New Mexico was :
new growth Feb.-April
fruits mature mid-Sept.
A nonrhizomatous species, bush muhly regenerates following fire from soil-stored seed .
Bush muhly occurs in plant communities dominated by velvet mesquite, creosotebush, and Joshua tree. To learn more about the fire regimes of these dominant species refer to the FEIS summary for that species, under "FIRE ECOLOGY OR ADAPTATIONS."
Ground residual colonizer (on-site, initial community)
Fire probably top-kills bush muhly. Burning causes at least short-term decline of bush muhly. Recovery time is thought to vary considerably [13,45] and is probably dependent on postfire weather and competition .
Information on regeneration of bush muhly after fire is lacking in the literature. Bush muhly probably establishes after fire by sprouting from the root crown and from soil-stored seed. Response to a single fire event may be favorable. Bush muhly's loosely arranged culms probably burn cooler and transfer less heat to the root crown compared to culms of more compact bunchgrasses. However, native bunchgrasses including bush muhly decline under repeated desert grassland fires enhanced by cheatgrass (Bromus tectorum) and red brome (B. rubens) .
Bushy muhly has shown poor establishment after fire in 2 studies, 1 of which involved a repeat burn. Near Tucson, Arizona, a late spring fire was conducted in 1992 to restore desert grassland invaded by Lehmann lovegrass. Seven native grasses including bush muhly were direct seeded after the fire. On 1 plot, sown in June 1992, bush muhly seedling density was 2.2 plants/m2 in October 1992. Bush muhly failed to establish on a plot sown in August 1992. By 1993, bush muhly was the only direct-seeded grass that was absent from all plots. In June 1994, an arson-ignited fire burned the study plots. The plots were not reseeded after the arson fire but grasses established from soil-stored seed. Seedling density of bush muhly in October 1994 was 0.6 plant/m2, the lowest of the 8 grass species present .
In another study near Tucson, bush muhly density 2 years after a management-ignited spring fire was 0.09 plant/m2 on unburned plots compared to no plants on burned plots. The author stated that there were too few bush muhly plants on either treatment to draw definite conclusions .
When ungrazed, bush muhly's dense grow may contribute to fire spread. It may be most
susceptible to fire damage when growing beneath shrubs because of increased fuels and higher temperatures as shrubs burn.
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