This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (for example, [4,28,30,105,108]).
Above ground: Plains muhly is a densely tufted [28,35] perennial bunchgrass. Culms are coarse, arising from a bulbous, thick, scaly base [28,30,35,51,68]. Plants are of medium height [21], with culms ranging from 8 to 20 inches (20-60 cm) tall and 1 to 2 mm thick. Leaves are narrow and folded. The inflorescence is a narrow, uneven, spikelike panicle 2 to 5 inches (5-10 cm) long [4,28,30,51,68,108]. Flower spikelets are 2.5 to 3 mm long [35], with awnless lemmas [28]. Spikelets are 1- [51,72] or rarely 2-flowered [87], with 1 seed/spiklet generally developing [51]. The fruits are caryopses 1.6 to 2.3 mm long [4]. Seeds are 1.6 to 2.3 mm long [87] and weigh 213 g/L or 11,345 seeds/g [21].
Below ground: Plains muhly has short, fibrous roots. One study found plains muhly was shallowly rooted compared to 9 other Nebraska grasses; maximum root length of plains muhly was 3 feet (1 m) [45]. In a blue grama-rough fescue-porcupine grass-plains muhly community in southern Saskatchewan, plains muhly had the shallowest roots of the 4 dominant species. Its roots grew laterally from tillers for 5 to 6 inches (12-15 cm), then grew down to a maximum depth of 16 to 20 inches (40-50 cm). Main root branches were densely covered with small lateral roots up to 15 mm long. Roots of other grass species extended 4 to 13 inches (10-33 cm) below roots of plains muhly [14].
Plains muhly resembles Richardson's muhly (M. richardsonis) above ground; plains muhly is distinguished by its lack of rhizomes [4,68].
Physiology: Plains muhly is drought tolerant [1]. It is a C4 grass [91,100]. This photosynthetic pathway may confer tolerance to high temperatures and/or dry soils (review by [61]) (see Site Characteristics); it also has implications for plains muhly's response to fire.
Historically, the grassland and woodland communities in which plains muhly is common probably had mean fire-return intervals of 30 years or less. Descriptions—including this one—of presettlement FIRE REGIMES in Great Plains grasslands are mostly estimates. Since grasslands generally lack trees that tolerate repeated fire and retain fire scars, tree-scar fire histories in the Great Plains are mostly unavailable [113].
Great Plains grasslands: Historically, prairie fires on the Great Plains were likely extensive and frequent. Accounts of settlers in Wisconsin mention wildfires 12 miles (19 m) across (review by [12]). Estimates of presettlement fire-return intervals on the Great Plains range from 5 to 25 years (reviews by [56,57,103]). Fire-return intervals were likely longer in the Northern Great Plains than the Southern Great Plains, ranging from 8 to 25 years in the north [56] and 5 to 10 years in the south [57]. Areas with broken topography—where plains muhly often grows [62]—likely experienced fire less frequently ([115], review by [56]) than contiguous sites, with fire returning about every 30 years on dissected sites in the Northern Great Plains (reviews by [56,103]). Based on settlement accounts (Marcy 1849 cited in [103]) and the frequency of fire necessary to prevent mesquite (Prosopis spp.) invasion, Southern Great Plains grasslands that were dissected with rivers and breaks may have had fire-return intervals of 20 to 30 years (review by [103]). Fire season in the Great Plains ran from April to September, with most fires occurring in July and August (review by [56]).
It is uncertain how important Native American-set fires were in determining historical FIRE REGIMES in the Great Plains. Some authorities theorize that these treeless grasslands resulted from frequent, repeated aboriginal fires [83,93,94]. Native Americans burned prairies in the fall, and probably in other seasons as well. In the Northern Great Plains, Native Americans set fires in fall after frosts and plant dry-up. In the Southern Great Plains, Native Americans were noted as setting fires "as early as they could for hunting purposes" in late September (review by [12]). In a review, Wedel [109] concluded that it is "very probable" that Native American-set fires helped maintain the treeless structure of the Great Plains, but that "climate is primarily responsible for this (treeless) vegetation".
Woodlands: Woodlands of the Great Plains may have historically experienced frequent surface and infrequent stand-replacing fires. Estimates for historical fire-return intervals of interior ponderosa pine woodlands in eastern Montana, the Dakotas, and Nebraska range from 20 to 300 years for surface and stand-replacement fires, respectively. Some claim that interior ponderosa pine woodlands experienced a combination of surface and stand-replacement fires, with stand-replacing fires more common; others contend that these communities experienced mostly frequent surface fires (review by [54]). Brown and Sieg [8] report an average fire-return interval of 22 years for presettlement interior ponderosa pine communities of South Dakota. Fire-return intervals of interior ponderosa pine communities in Wind Cave National Park, South Dakota, averaged 10 to 12 years, with a range of 2 to 23 years [8]. Fire season on interior ponderosa pine savannas of eastern Montana and the Dakotas peaks in July and August, when the majority (73%) of lightning-strike ignitions occur. Wildfire season generally extends from April to September [39].
Fires might have been rare in Rocky Mountain Douglas-fir/plains muhly habitat types on moist sites of the Missouri River Breaks in Montana. Of 14 stands, 61% "showed no evidence" of either multiple fire scars or charcoal. The authors ascribed low fire frequency to the "isolated, island-like nature" of these communities [79].
Wooded draws, ravines, and coulees of the Great Plains [15,60,70] likely had surface, mixed-severity, and stand-replacement fires, with a mean of 10 years between surface fires and a range of 30 to 100 years for stand-replacement fires. Surface fires might have been more common than stand-replacing fires [55].
See the Fire Regime Table for further information on FIRE REGIMES of vegetation communities in which plains muhly may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
FIRE ADAPTATIONS AND PLANT RESPONSE TO FIRE:
Fire adaptations: Research on plains muhly's adaptations to fire was lacking as of 2009. In part, the bunchgrass form is an adaptation to low-severity fire. Tiller buds on the root crown are at or below the soil surface [95], and so are protected from fast-moving grassland fires.Plant response to fire: Specific information on methods of plains muhly regeneration after fire was not available in the literature. Plains muhly probably sprouts from tillers and establishes from seed after fire. In general, muhlys (Muhlenbergia) show no change or increase after fire [103,115]. For example, on the Pipestone National Monument, Minnesota, plains muhly showed 0.1% cover the 5th year of annual April burning [6]. Its prior absence suggests that it established from seed after fire. Spring prescribed fire may favor plains muhly and other warm-season, C4 grasses over cool-season, C3 grasses [56,91].
On the Konza Prairie Natural Research Area, Kansas, plots in a big bluestem-switchgrass (Panicum virgatum)-Indian grass community were either burned under prescription in various seasonal rotations or mowed and baled, with bales moved off site. Plains muhly abundance was greatest on plots burned annually in November[26]:
Percent plains muhly abundance after prescribed burning or mowing and baling on the Florence soil series on the Konza Prairie Natural Research Area. The number of plots/treatment ranged from 1-5. Treatments started in 1972; data were collected in 1983 [26]. Fire rotation and season Plains muhly cover (and frequency) (%) Unburned 0.8 (15) Annually burned November 2.4 (50) March 1.6 (40) 2-year rotation, April fire 0.07 (80) 4-year rotation, April fire 0.7 (22) Mowed & baled, March 0.7 (45) Mowed & baled, July 0.2 (25) Soil characteristics on the Florence soil series (compiled by Gibson [50]) Depth (cm) 25 Topography upper rims of slopes Slope (%) 0 Texture cherty silt-loamAnother study on the Konza Prairie Natural Research Area found no significant difference in plains muhly biomass after prescribed fire on lowland vs. upland big bluestem communities. Starting in 1981, study sites were burned in early April on 1- to 4-year rotations (n=11 burned sites + 4 unburned controls). Data were collected from 1981 to 1985, with data from sites with different fire rotations pooled. Although apparently insensitive to site differences, plains muhly was sensitive to differences in year of sampling, achieving greatest biomass 2 years after burning (P=0.013) [25,27].
Plains muhly frequency was reduced slightly 3 years after a September fire in a threadleaf sedge-needle-and-thread grass-blue grama community in Theodore Roosevelt National Park, North Dakota [19]:
Plains muhly frequency (%) on burned and unburned sites, postfire year 3, in Theodore Roosevelt National Park [19] Site Burned Unburned Dedication Hill 0 2 North Rim 50 55Plains muhly is typically dominant on dry, dissected hills and ridges (see Site Characteristics). In most years, plains muhly-dominated plant communities may be less dense and productive [62,64], and have lighter fuel loads, than surrounding plant communities. Plains muhly may comprise a substantial portion of total biomass on some mixed-grass prairies, though [5]. Fuels characteristics for plant communities with plains muhly are presented below by state and region.
Minnesota: Before a fall prescribed fire, litter depth in a blue grama-Canada bluegrass-prairie dropseed (Poa compressa-Sporobolus heterolepis)-plains muhly shortgrass prairie in Blue Mounds State Park ranged from 1.0 to 9.8 inches (2.5-25 cm), with a mean of 6.9 inches (17.5 cm). There was "almost no litter" after the fire. The next growing season, the vegetation "was very thick", and litter accumulation was <1 inch (2.5 cm) [10].
North Dakota: Blue grama-needle-and-thread grass-plains muhly plant communities of the Central Grasslands Research Station were the least productive of 9 short- and mixed-grass prairie communities surveyed, with production averaging 2,665 kg/ha. Most biomass in this community was from forbs [64]. A needle-and-thread grass-plains muhly-narrowleaf sedge vegetation type in southwestern North Dakota had an average yield of 135.8 g/m²; plains muhly contributed 12.2 g/m² to the total yield. Whitman [112] provides breakdowns of percent composition of the community by species' basal areas and densities.
South Dakota: In a blue grama-little bluestem mixed-grass prairie where plains muhly was a "major species", mean total biomass for grass litter and standing dead vegetation was 132 g/m² and 21 g/m², respectively. The study site was on the Samuel H. Ordway, Jr. Memorial Prairie [91]. Maximum standing dead herbage on the Prairie may range from 97 g/m² to 243 g/m² [5,91].
Kansas: In a common garden experiment, plains muhly transplants attained a leaf area of 17 cm²/plant, the least of 4 Muhlenbergia spp. tested [90].
Southern Great Plains: See Coupland [12] for seasonal aboveground biomass measures for mixed-prairie communities in the Southern Great Plains.
Plains muhly is most common on dry, coarse soils with dissected topography.
Soils: Plains muhly tolerates and is most abundant on dry [4,5,7,23,28], shallow soils. On remnant patches of rolling prairie in Kansas and Nebraska, plains muhly was most frequent on dry-mesic to very dry soils (2.2%) and absent on mesic soils [4]. It was noted on shallow soils in western North Dakota [29] and was most common on weakly developed soils in short- and mixed-grass prairies of South Dakota [68,110]. A study in a mixed-grass prairie in southeastern Montana found that plains muhly occurred on thin-soiled hills but not on deeper, low-lying loams or sandy loams (P=0.05) [111]. However, plains muhly is not confined to shallow soils. Blue grama-needle-and-thread grass-plains muhly plant communities of the Central Grasslands Research Station occur on deep, well-drained soils on moderately permeable glacial till [64].
Plains muhly is often noted on eroded soils [110]. On prairies of southern Canada, Coupland [13] found plains muhly was "characteristic of eroded places" and infrequent elsewhere. Looman [62,63] classified plains muhly as an indicator species of eroded, highly calcarious (pH ≥7.2), old soils in southern Saskatchewan.
Plains muhly prefers coarse-textured soils [4,23,28]; parent materials are variable. Plains muhly typically grows in sandy soils and, as the alternative common name "stonyhills muhly" suggests, cobbly and gravelly soils [4,21,23,28,31], but it is not restricted to coarse soils. Plains muhly is noted on silty clays in glaciated plains of Montana [81] and in southwestern North Dakota [112]. In southwestern Saskatchewan, plains muhly grew in loams but not sands or clays [47]. It also grows on fine loams in South Dakota [91]. In North Dakota, the needle-and-thread grass-plains muhly-narrowleaf sedge vegetation type occurred on sandy loams of moderate to steep slope. Soils where plains muhly was codominant were characterized by "extreme shallowness", with bedrock, gravel, or scoria (volcanic rock containing cavities created by gas bubbles trapped in lava) close to the soil surface. Soil organic matter content was "surprisingly" high (5.05%); the soil was slightly saline (conductivity of 0.97); and pH range was 7.2 to 8.9 [112]. In South Dakota, plains muhly grew in soils formed from "any parent material that was rapidly eroding" [110]. Plains muhly often grows on limestone-derived soils, including limestone outcrops [4]. Plains muhly occurs on limey upland and thin loess soils in Nebraska [97].
Topography: Plains muhly is most common on hillslopes, ridges, and other upland sites [4,5,17,21,28,29,64,110], with aspect varying with site. Topography is often broken and dissected where plains muhly is dominant [5,62]. In the Badlands of western North Dakota, plains muhly was mostly found on the tops of scoria buttes. Vegetation was sparse (10%-15% total cover); mostly plains muhly and western wheatgrass in scattered clumps [114]. On the Knife River Indian Villages National Historic Site, North Dakota, blue grama-needle-and-thread grass-western wheatgrass-plains muhly communities occurred on terraces above the Knife and Missouri rivers [11]. On remnant patches of rolling prairie in Kansas and Nebraska, plains muhly was most frequent on steep upper slopes (14.4%), present on gentle upper slopes (2.2%), and absent from lowlands [48]. In Minnesota, plains muhly is common on dry beach ridges of ancient Lake Agassiz in big bluestem-needle-and-thread grass-blue grama mixed-grass prairies [20]. It occurs in rocky bluff edges in the Upper Peninsula of Michigan [105]. In big bluestem-plains muhly prairie on the Samuel H. Ordway, Jr. Memorial Prairie [5] and in rough fescue and blue grama communities of central Saskatchewan [40], plains muhly was most common on south-facing slopes. In southern Saskatchewan, however, plains muhly was an indicator species of north-facing coulees, growing on low- to midslopes [15]. In coulees of the Oldman River, Alberta, plains muhly occupied steep slopes of all aspects [61].
Elevation: Plains muhly occurs from 980 to 4,600 feet (300-1,400 m) across its range [4]. State elevational ranges are given below.
Area Range Benton County, Arkansas collected at 1,000-1,250 feet [69] Colorado 5,000-6,800 feet [35] Missouri River Breaks, Montana 2,700-3,200 feet in Douglas-fir/plains muhly habitat types [85] New Mexico 5,000-6,500 feet [68]Climate: Prairie communities, where plains muhly is most common, have semiarid to dry subhumid climates, with individual years ranging from arid to humid (review by [12]). Extended droughts are frequent in the Great Plains [57,109].
Information on fire's effects on plains muhly was lacking as of 2009. Research is needed on all aspects of plains muhly fire ecology.
In general, grassland fires consume aboveground vegetation of bunchgrasses, but perennating buds in the root crown are protected by plant foliage and/or soil [95]. Because it is a bunchgrass of moderate size and density, it is likely that fire usually top-kills plains muhly.
Plains muhly provides seasonal forage for elk [117,118], white-tailed deer, mule deer, and livestock [72,87,110], with use varying with site. In Wind Cave National Park, elk used plains muhly most in winter (7.8%) [117,118] and least in fall (trace) [117]. Plains muhly was not important forage for elk and mule deer on the Missouri River Breaks of Montana [65].
Wild turkeys feed on plains muhly seeds in fall and winter [72,87].
Several species of bugs (Homoptera) that are endemic to tallgrass prairies feed exclusively or nearly exclusively on plains muhly [32].
Information on the value of plains muhly as livestock forage is limited and conflicting. Some studies show high livestock utilization of plains muhly; others show low use. On the Missouri River Breaks of Montana, cattle use of plains muhly in a big sagebrush-western wheatgrass community was high in summer (15%), but cattle grazed plains muhly in only trace amounts in winter [65]. On the Livestock Experiment Station near Miles City, Montana, cattle grazed dissected, hilly rangelands with plains muhly more than rolling hill upland rangelands and less than seasonally flooded bottomland rangelands [42]. According to Goetz [29], plains muhly in western North Dakota is "seldom eaten by livestock" in any season.
Palatability and/or nutritional value: Plains muhly provides fair to good forage for elk, white-tailed deer, and mule deer, and sometimes for livestock. [16,72,87,110]. However, reports are mixed on plains muhly palatability for livestock. One North Dakota study found plains muhly was palatable to livestock [46] despite its coarse leaves. However, another North Dakota study concluded that plains muhly was "tough and wiry" and unpalatable to cattle [82].
Cover value: Plains muhly provides fair cover for ground-nesting birds [51]. Rocky Mountain juniper/yellow sweetclover (Melilotus officinalis)-plains muhly woodlands in Badlands National Park provide habitat for at least 25 bird species [89].
Plains muhly dominates some but not most of the plant communities in which it grows [78]. It is most abundant in short- and mixed-grass prairies and less important in tallgrass prairies, mountain grasslands, shrublands, and woodlands.
Shortgrass prairie:
Plains muhly is most common in wheatgrass-blue grama-needlegrass (Triticeae-Bouteloua gracilis-Stipeae) shortgrass prairies of the Northern Great Plains [2,3,47,53]. It may be dominant or may codominate with blue grama [10] and/or western wheatgrass (Pascopyrum smithii) and needle-and-thread grass (Hesperostipa comata) [24] on some sites. It is typically dominant on steep slopes, with blue grama and western wheatgrass dominant on low slopes and flats [17].
Mixed-grass prairie:
Northern mixed-grass prairie:
Plains muhly typically grows in association with bluestems (Andropogoneae) and gramas (Bouteloua spp.) in northern mixed-grass prairies. On the Felton Prairie of Minnesota, plains muhly was an important component of big bluestem (Andropogon gerardii)-needle-and-thread grass-blue grama prairies [20]. It is most frequently associated with little bluestem (Schizachyrium scoparium) on mixed-grass prairies of South Dakota [110]. For example, plains muhly had 49% frequency on remnant big bluestem-little bluestem-Indian grass (Sorghastrum nutans) prairies of eastern South Dakota [38]. It sometimes codominates with little bluestem. On the Samuel H. Ordway Jr. Memorial Prairie of South Dakota, the little bluestem-plains muhly-porcupine grass
(Hesperostipa spartea) community occurs on dry, upland sites [104]. Plains muhly may be a minor component of the big sagebrush (Artemisia tridentata)-mixed-grass rangeland type of the Northern Great Plains [9,113].
Central and southern mixed-grass prairie:
Plains muhly is commonly associated with little bluestem and sideoats grama in the Central Great Plains [97]. For example, it is a characteristic species of hairy grama-sideoats grama-buffalo grass (Bouteloua hirsuta-B. curtipendula-Buchloe dactyloides)-little bluestem prairies on the loess hills of Missouri [49]. It is a minor component of blue grama-sideoats grama mixed-grass prairie near a mixed-grass-tallgrass prairie ecotone in central Nebraska [45]. Coupland [12] listed plains muhly as an associated grass in western wheatgrass-big bluestem-buffalo grass communities of the Southern Great Plains.
Tallgrass prairie:
Plains muhly is often only a minor component of tallgrass prairies dominated by big and/or little bluestem [107]. In North Dakota,
Hirsch [41] found plains muhly was commonly associated with big bluestem prairies, but often had low relative cover (<3%). In Indiana, plains muhly grows in the gravel prairie barrens [44], a rare [44,50] community dominated by sideoats grama [43].
Mountain grasslands:
Plains muhly is occasional to common in mountain grasslands. In Montana, it occurs in bluebunch wheatgrass (Pseudoroegneria spicata) [70,84] and northern rough fescue [70] habitat types. It is a common component in the needle-and-thread grass phase of the northern rough fescue (Festuca altaica)-bluebunch wheatgrass rangeland type east of the Continental Divide [99].
Woody communities:
Plains muhly is sometimes present in woody plant communities but is rarely dominant. It is a component of shrubby cinquefoil (Dasiphora floribunda)/northern rough fescue and skunkbush sumac/Idaho fescue (Rhus trilobata/Festuca idahoensis) habitat types of western Montana [70]. Plains muhly occurs in interior ponderosa pine (Pinus ponderosa var. scopulorum) woodlands of Montana [73], North Dakota ([76], review by [34]), and Nebraska ([101], review by [34]); limber pine (P. flexilis) [75] woodlands of western North Dakota; and Rocky Mountain juniper (Juniperus scopulorum) woodlands of South Dakota [89]. Plains muhly was a minor component of interior ponderosa pine/little bluestem woodlands of northwestern Nebraska, with 1% relative cover [71]. It had <10% cover in Rocky Mountain lodgepole pine (P. contorta var. latifolia) forests of west-central Montana [84]. Plains muhly is dominant, however, in the ground layer of Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca) habitat types in the Missouri River Breaks of north-central Montana [79] and Rocky Mountain juniper woodlands of Badlands National Park, South Dakota [88].
The following vegetation classifications describe plant communities where plains muhly is a dominant species:
Research on plains muhly's position in grassland succession was sparse as of 2009. Limited studies suggest that plains muhly is a seral species and that drought, soil disturbance, erosion, and other conditions that set grasslands back to early-successional stages favor plains muhly.
Plains muhly prefers open sites [68,90] but apparently tolerates light shade. In a Kansas field experiment, all 30 plains muhly plants transplanted under the canopy of a slippery elm-shagbark hickory (Ulmus rubra-Carya ovata) forest died, while 77% (23 plants) survived transplanting in an open garden [90]. Plains muhly is noted in open woodlands, though. In northwestern Nebraska, plains muhly occurred in scattered or open interior ponderosa pine stands but not in dense stands [101]. In Saskatchewan, plains muhly is noted in quaking aspen (Populus tremuloides) groves [66] and wooded draws near the Matador Research Station [60]. Quaking aspen may become invasive in some southern Canadian prairies, eventually shading out plains muhly and other grasses [66].
In a study of mixed-grass prairie communities during the "Dust Bowl" drought of 1933 to 1940, Albertson and Weaver [1] found plains muhly cover increased as big bluestem and little bluestem died off. In 1938, the authors reported plains muhly seedling establishment on study sites across Nebraska, Iowa, Colorado, Kansas, Missouri, and Oklahoma. By 1942, small, pure stands of plains muhly were common, with individual plains muhly bunches 5 to 8 inches (10-20 cm) in diameter [1].
Some soil disturbances, such as erosion and animal disturbance, may favor or have little effect on plains muhly abundance. In southern Alberta and Saskatchewan, Coupland [13] found plains muhly was dominant on eroded soils (18% frequency) but only occasional in climax grasslands on stable soils (2%-4% frequency). Plains muhly occurs in habitats of fossorial mammals. It grows, for example, in black-tailed prairie dog towns of Billings County, North Dakota [96]. On the Cayler Prairie Preserve in Iowa, plains muhly occurred both on and off American badger mounds near dens, but its mean dry-weight biomass was more on mounds (16.1 g/m²) than off (11.0 g/m²) [74].
In a study of succession on blowout (wind-eroded) communities in the Nebraska sandhills, plains muhly was an important component of the prairie sandreed-lemon scurfpea (Psoralea lanceolata) blowout association, a successional stage in duneland communities in which blowouts are actively forming. Blowouts were more common in the region during the settlement period than at present; this may be due to improved rangeland management and/or fire exclusion [98].