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Species Review

Elymus elymoides, squirreltail

Written
April, 2001
Contributors
Kevin Simonin - 1st Author

Simonin, Kevin A. 2001. Elymus elymoides, squirreltail. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/elyely

DOI
10.2737/feis-species-review-elyely

AbbreviationCommon NameScientific NameClassificationStatus
Plants
ELYELYsquirreltailElymus elymoidesLife Form: Plants/Graminoid
Kingdom: Plantae
Class: Monocot
Order: Cyperales
Family: Poaceae
Genus: Elymus		Fed. Protected: No
Nativity: Native
Invasiveness: Noninvasive

A photo of several reproductive stems of a grass, with awned seeds stacked tightly together to form the so-called "squirrel tail" that gives this grass its common name.
A photo of a low bunchgrass with reproductive stems barely exceeding the low leaves growing among dark gray stones with other low, alpine species. Numerous butterflies flutter behind the grasses, and mountains can be seen in the distance beyond a wide valley.
A photo of a bunchgrass with reproductive stems mostly exceeding its short, flat leaves. Reproductive stems have tufts of awned seeds at their ends.
A photo of low grasses growing with scattered shrubs in a somewhat dry, steppe-like area that appears to be transitioning to a weedy grassland after a fire.
A graph with "percent of maximum" on the y-axis and "phenological stages - available energy in roots of squirreltail at several stages of maturity" on the x-axis. Peaks and valleys along the line are labeled "first growth", "2nd leaf", "3rd leaf", "anthesis", "seed ripe", "quiescent", "fall regrowth", and "winter dormancy".

Taxonomy

A photo of several reproductive stems of a grass, with awned seeds stacked tightly together to form the so-called "squirrel tail" that gives this grass its common name.
Photo Credit
Wikimedia Commons image by Jim Pisarowicz.

Squirreltail in fruit in Wind Cave National Park.

The scientific name of squirreltail is Elymus elymoides (Raf.) Swezey [60,87,113] (Poaceae). Barkworth and Dewey [12] realigned Sitanion hystrix (Nuttall) J. G. Smith in the Elymus genus as Elymus elymoides. Realignment of the Elymus genus is based upon morphological and genomic characters [12,56].

The following subspecies are currently recognized: Elymus elymoides ssp. brevifolius, E. e. ssp. californicus, E. e. ssp. elymoides, and E. e. ssp. hordeoides [93]. Squirreltail hybridizes frequently with other Elymus species and infrequently with Hordeum species [200]. Squirreltail also hybridizes with saline wildrye (Leymus salinus) [106].

Synonyms

  • Sitanion hystrix (Nutt.) J. G. Smith [51,82,115,123,132]

Other Common Names

bottlebrush squirreltail

General Distribution

Squirreltail is found from British Columbia to Saskatchewan, south throughout the western and central United States and into Mexico [200]. The PLANTS database provides a distributional map for squirreltail. Elymus elymoides subsp. brevifolius occurs in the San Bernardino Mountains, Peninsular Ranges, Modoc Plateau, and Mojave Desert of California to Oregon, the Great Plains and south to northern Mexico. Elymus elymoides subsp. californicus is found in the Klamath Range, Cascade Range, Sierra Nevada, San Gabriel Mountains, San Bernardino Mountains, east Sierra Nevada of California to Washington, Montana and Utah. Elymus elymoides subsp. elymoides is found in the Transverse Ranges, San Jacinto Mountains, and Great Basin floristic Province from California to Washington, Wyoming and Colorado. Elymus elymoides subsp. hordeoides occurs in Klamath Range from California to Washington and Nevada.

A photo of a low bunchgrass with reproductive stems barely exceeding the low leaves growing among dark gray stones with other low, alpine species. Numerous butterflies flutter behind the grasses, and mountains can be seen in the distance beyond a wide valley.
Photo Credit
Photo by Matt Lavin, iNaturalist.org, some rights reserved.

Squirreltail growing on talus slopes on Mount Rose in Nevada (CC BY 4.0).

States and Provinces

  • United States: AZ CA CO ID IL KS KY MI MT NE NV NM ND OK OR SD TX UT WA WY
  • Canada: AB BC MB SK
  • Mexico

Site Characteristics

Squirreltail has wide ecological amplitude [161], but it most commonly occurs in disturbed areas of deserts, valleys, foothills, and mountain meadows [18].

Regional

Squirreltail is found throughout Colorado on dry hills, plains, and rocky slopes, and within open woods and meadows [92]. In Montana, squirreltail occurs in dry, open habitats, from valley to timberline [123]. Throughout the western Great Plains, squirreltail is commonly found on dry soils of pastures and roadsides [82]. In Utah, squirreltail prefers dry to moist vegetation types, from salt desert shrub to alpine grassland [200]. Plains, rocky hills, or montane slopes are common sites in New Mexico [132]. In Arizona, open sandy ground, rocky hills, and open pine woods are common sites [115]. Squirreltail is common to dry rangeland areas of Kansas [154]. In central Washington, squirreltail prefers disturbed sites. Within these sites plant density is negatively correlated with individual plant size [153]. In California, squirreltail is found in scattered stands at high elevations on dry, gravelly soils. It is also common to hillsides and brush associations [168].

Soils

Squirreltail inhabits a wide variety of soil types and is tolerant of saline [108] and alkaline soils [168]. It is widely distributed in salt-desert shrub ranges of the west, on dry, gravelly soils, or within alkaline conditions. Squirreltail is found on clayey soils of northeastern California sagebrush communities [27]. Throughout Montana it occurs predominantly on dry, gravelly soils, in saline or alkaline areas [150]. Within alpine areas of Olympic National Park, Washington, squirreltail prefers well-drained, undifferentiated, disturbed, shallow and stony soils [21]. Passey and Hugie [158] found squirreltail to achieve better growth on Newdale silt loam soils than on Brunt silt loam, in areas with similar climate, slope, and exposure. Squirreltail may also occur on loose, ashy soil [11].

Squirreltail is not common within wet areas such as river lowlands and soil along irrigation canals [153].

Elevation

StateElevation
Arizona2,000 to 11,500 (609-3,505 m) [115]
west-central Montana7,000 to 9,200 feet (2,135-2,805 m) [123]
New Mexico4,500 to 11,500 feet (1,372-3,505 m) [132]
Utah3,510 to 11,400 feet (1,070-3,500 m) [200]

Plant Communities

Squirreltail is a common component of sagebrush (Artemisia spp.)/grass communities of the Intermountain shrubsteppe [109,212].

Within rangelands of Utah, Nevada, southern Idaho, and western Wyoming, squirreltail commonly grows under and adjacent to shadscale (Atriplex confertifolia), black greasewood (Sarcobatus vermiculatus), and green rabbitbrush (Chrysothamnus viscidiflorus) [161]. Bottlebrush squirreltail is a common component of pinyon-juniper (Pinus spp.-Juniperus spp.) communities of the Great Basin. It occurs mostly within the mountain ranges of Nevada and Utah, and to a lesser extent in California and Idaho [191].

Arizona

Squirreltail occurs in northern desert shrub communities [137] and ponderosa pine (Pinus ponderosa) forests [39,137]. Within aspen (Populus tremuloides)-bunchgrass communities of northern Arizona, squirreltail commonly occurs with Arizona fescue (Festuca arizonica), mountain muhly (Muhlenbergia montana), western yarrow (Achillea millefolium), lupine (Lupinus spp.), fleabane (Erigeron spp.) and American vetch (Vicia americana) [86]. Squirreltail is occasionally found in openings and under shrub canopies within shrub live oak (Quercus turbinella)-mixed shrub communities [173].

California

Squirreltail is native to California's central valley and is commonly associated with purple tussock grass (Nassella pulchra), nodding tussock grass (N. cernua), smallflower tussockgrass (N. lepida), and shooting star (Dodecatheon spp.) [14]. It is a minor component of blue oak (Quercus douglasii) [28,126] and interior live oak (Q. wislizenii) habitats [126].

Within sagebrush scrub of the White Mountains, prairie Junegrass (Koeleria macrantha), muhly (Muhlenbergia spp.) and timberline bluegrass (Poa glauca spp. rupicola) are common associates [130]. Within alluvial fans of desert shrub communities, squirreltail is commonly associated with Indian ricegrass (Achnatherum hymenoides) and desert needlegrass (A. speciosum). Shrub associates of squirreltail include California jointfir (Ephedra californica), goldenfleece (Ericameria arborescens), white burrobrush (Hymenoclea salsola), and purple sage (Salvia dorrii) [135].

Squirreltail occasionally occurs in alpine flora of the Sierra Nevada eastern slope [40]. It is also an occasional understory species of California red fir (Abies magnifica) forests in the Sierra Nevada [155].

Colorado

Squirreltail is a member of north-central Colorado's short-grass prairie [45,57,175]. Within the short-grass prairie, squirreltail is commonly associated with western wheatgrass (Pascopyrum smithii), purple threeawn (Aristida purpurea), sideoats grama (Bouteloua curtipendula), blue grama (Bouteloua gracilis), buffalo grass (Buchloe dactyloides), and needle-and-thread grass (Hesperostipa comata) [57]. It occurs in blue grama ranges of Colorado along with sun sedge (Carex heliophila), sand dropseed (Sporobolus cryptandrus), and purple threeawn [139].

Within Colorado pinyon-Utah juniper (Pinus edulis-Juniperus osteosperma) habitats of Colorado, squirreltail is associated with Gambel oak (Quercus gambelii), Utah serviceberry (Amelanchier utahensis), true mountain-mahogany (Cercocarpus montanus), fendlerbush (Fendlera rupicola), banana yucca (Yucca baccata), and antelope bitterbrush (Purshia tridentata). Grass associates include cheatgrass (Bromus tectorum), Indian ricegrass, mutton grass (Poa fendleriana), and brome grasses (Bromus spp.) [67].

Squirreltail is an occasional associate of Rocky Mountain bristlecone pine (Pinus aristata) [162].

Idaho

Squirreltail is a dominant species in shadscale communities of south-central Idaho [174], along with Indian ricegrass [189].

Montana

Squirreltail generally occurs as scattered plants on rangelands [150]. In the eastern plains of Montana, squirreltail is a dominant species of saline rangelands in association with alkali sacaton (Sporobolus airoides), western wheatgrass (Pascopyrum smithii), thickspike wheatgrass (Elymus lanceolatus), inland saltgrass (Distichlis stricta), Sandberg bluegrass (Poa secunda), and basin wildrye (Leymus cinereus). Shrub associates include black greasewood and Nuttall's saltbush (Atriplex nuttallii).

Nevada

Squirreltail occurs in gray low sagebrush (Artemisia arbuscula ssp. arbuscula) and big sagebrush (A. tridentata) communities. Principal grass associates include cheatgrass [24], Sandberg bluegrass [24,25], bluebunch wheatgrass (Pseudoroegneria spicata), and Thurber needlegrass (Achnatherum thurberianum). Common shrub associates include green rabbitbrush and gray horsebrush (Tetradymia canescens). Forb associates include bird's-beak (Cordylanthus ramosus), mourning milkvetch (Astragalus atratus), woollypod milkvetch (Astragalus purshii), desert yellow fleabane (Erigeron linearis), lava aster (Lonactis alpina), Heerman's buckwheat (Eriogonum heermanii), tail cup lupine (Lupinus caudatus) and phlox (Phlox longifolia) [25].

In northeastern Nevada squirreltail is commonly found with black sagebrush (Artemisia nova) [107,219], shadscale, Nevada ephedra (Ephedra nevadensis), Sandberg bluegrass and Indian ricegrass [107].

Squirreltail also occurs in shadscale communities [24,145]. Common shrub associates include green molly (Kochia americana), winterfat (Krascheninnikovia lanata), budsage (Artemisia spinescens) and spiny hopsage (Grayia spinosa) [145]. Common grass associates are cheatgrass, Indian ricegrass [24] and galleta (Pleuraphis jamesii) [145]. Several common forb associates are salt lover (Halogeton glomeratus), Adonis blazingstar (Mentzelia multiflora) and gooseberryleaf globemallow (Sphaeralcea grossulariifolia). Squirreltail is also common to juniper (Juniperus spp.) and greasewood communities [24].

Squirreltail is found in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) rangelands of Nevada [23].

Oregon

Eastern Oregon grass associates of squirreltail include bluebunch wheatgrass, prairie Junegrass [31], Idaho fescue (Festuca idahoensis), Thurber needlegrass [31,59], Sandberg bluegrass and cheatgrass. Common forbs include Hood's phlox (Phlox hoodii) and maiden blue eyed Mary (Collinsia parviflora) [59]. Squirreltail occurs in lodgepole pine stands in the Cascades of Oregon [61], along with western needlegrass (Achnatherum occidentale) and Ross' sedge (Carex rossii) [65].

Texas

In western Texas squirreltail occurs in Pinchot juniper (Juniperus pinchotii) rangelands with sideoats grama, buffalo grass, slim tridens (Tridens muticus), awnless bushsunflower (Simsia calva) and plains fleabane (Erigeron modestus) [143].

Utah

Squirreltail is common in salt-desert shrub ranges along with the shrubs shadscale (Atriplex confertifolia), mat saltbush (A. corrugata), fourwing saltbush (A. canescens), valley saltbush (A. cunneata), greasewood, winterfat, spiny hopsage, budsage, black sagebrush and green rabbitbrush. Common grasses include Indian ricegrass, Sandberg bluegrass, galleta, alkali sacaton, sand dropseed, and blue grama. Squirreltail is also found in pinyon-juniper woodlands [29], ponderosa pine savannas [148] along with dry Douglas-fir (Pseudotsuga menziesii) and mixed conifer habitats [29].

Wyoming

Squirreltail commonly occurs in big sagebrush steppe along with aspen, big sagebrush, mountain snowberry (Symphoricarpos oreophilus), Utah serviceberry, rose (Rosa spp.), Scouler's willow (Salix scouleriana), and Oregon-grape (Mahonia repens). Common forb associates include rosy pussytoes (Antennaria microphylla), arrowleaf buckwheat (Eriogonum compositum), pineywoods geranium (Geranium caespitosum) and northern bedstraw (Galium boreale). Graminoid associates include needle-and-thread grass, Columbia needlegrass (Achnatherum nelsonii), and elk sedge (Carex geyeri) [36].

Classifications describing plant communities in which squirreltail is a dominant species are as follows:

  • Idaho [97]
  • California [218] Colorado [119]
  • New Mexico [94,146]
  • Nevada [24,25,107,125,192,221]
  • Oregon [59,101,197]
  • Utah [151,203]
  • Wyoming [186]

Botanical Description

A photo of a bunchgrass with reproductive stems mostly exceeding its short, flat leaves. Reproductive stems have tufts of awned seeds at their ends.
Photo Credit
Image by Dave Powell, USDA Forest Service (retired), Bugwood.org.

Squirreltail growth form.

Squirreltail is a cool season, [8] perennial bunchgrass native to the Intermountain West [18]. It is solitary [200], possessing solid, mostly flowering culms [210], with flat leaf blades. The inflorescence is a spike 0.8 to 6.7 inches (2-17 cm) long [82,150,200]. Ecotypic variation is common among squirreltail populations [9].

Reynolds and Fraley [164] found bottlebrush squirreltail roots to achieve depths of 39.4 inches (100 cm) below the soil surface. Depths below 39.4 inches (100 cm) were not seen due to a subsurface layer of basalt, suggesting rooting depths greater than 39.4 inches (100 cm) are possible. A lateral root extension of 16 inches (40 cm) was observed at 9.8, 20, 24 and 39.4 inch (25, 50, 60 and 100 cm) depths.

Raunkiaer Life Form

  • Hemicryptophyte [163]

Seasonal Development

The wide ecological amplitude of squirreltail leads to differential timing of phenological events between individuals of differing habitats [43,109]. Flowering generally occurs in spring or early summer [18,57]. Lower elevation populations (that is, cold desert, salt desert habitats) usually mature early June with higher elevation populations (that is, mountain brush, mountain meadows) reaching maturity in late July [18]. Hironaka and Tisdale observed phenological differences between the subspecies Elymus elymoides ssp. elymoides and ssp. californicum. In a common garden experiment E. e. ssp. elymoides developed 10 to 14 days earlier than ssp. californicum [100].

Between 1960 and 1969, Murray and others evaluated squirreltail phenology in southern Idaho. Growth began from mid-March to mid-April. Flower stalks began to form late-April to mid-May, with anthesis occurring in early to mid-June. Plants were dormant from the middle of July to the end of August with fall regrowth occurring through October [152].

Clary [43] evaluated squirreltail phenology and rate of growth from different environments using a transplant garden and growth chamber. The timing of squirreltail phenological events and overall growth rate was closely related to homesite environmental conditions. Squirreltail individuals from higher elevations were limited by cold temperatures whereas individuals from lower elevations were limited by water availability and warm temperatures. Under the same environmental constraints, squirreltail from areas with low moisture stress and cool climates showed higher growth rates, attaining maximum height earlier than individuals from warmer drier sites. Squirreltail requires the longest time to flower in areas of relatively moderate temperature and moisture regimes:

Time to flowering in days for squirreltail individuals from different habitats is shown below. Plants were grown at 6,490 feet (1,980 m) on a clay loam with an annual precipitation of 21.4 inches (544 mm) and annual temperature of 49 degree Fahrenheit (9.5 °C).

Squirreltail collection site descriptionDays to flower
7,410 feet (2,260 m), silt loam, ponderosa pine205.5
4,990 feet (1,520 m), stony clay loam, ponderosa pine201.2
7,200 feet (2,200 m), loam, pinyon-juniper193.8
7,810 feet (2,380 m), clay loam, ponderosa pine192.5
9,780 feet (2,980 m), gravelly loam, spruce-fir172.5
9,320 feet (2,840 m), gravelly sandy loam, mountain grassland166.8
4,530 feet (1,380 m), loamy fine sand, short grass165.8
4,720 feet (1,440 m), cobble clay, pinyon-juniper162.2
4,990 feet (1,520 m), stony clay loam, ponderosa pine159.5
5,510 feet (1,680 m), silty clay loam, sagebrush-greasewood158.0
4,530 feet (1,380 m), stony loam, oak savannah153.5

Squirreltail is responsive to fall rains in northern areas of the Great Basin, allowing for fall regrowth. Fall regrowth uses the majority of total available root carbohydrates partitioned during the summer [50]. The optimal soil temperature for root and shoot growth occurs at approximately 77 degrees Fahrenheit (25 °C). However, squirreltail shows continuous root growth down to 41 degrees Fahrenheit (5 °C) soil temperature [100].

Regeneration Processes

Squirreltail regenerates from surviving root crown [29,201] and seed [18]. Vegetative propagation is nonexistent [18]. Squirreltail has the ability to produce large numbers [99,214] of highly germinable seeds, with relatively rapid germination [214] when exposed to the correct environmental cues. Plants are self-fertilizing [55]. Seeds are readily dispersed by wind [15,99] a few days following maturation [18]. Dispersal is a function of squirreltail's long reflexed awns and disarticulating, mature inflorescence [99,131,148]. Seeds are dispersed when the spike inflorescence is carried along the ground by wind catching the long awns [131].

Although squirreltail has the potential for long distance seed dispersal, Martlette and Anderson [131] found natural plant cover to act as a barrier to dispersal. Wind dispersal of squirreltail seed did not exceed 131 feet (40 m), with viable seed remaining relatively close to mature squirreltail plants.

Dormancy protects squirreltail seeds from germinating during seasonal dry periods. Dry seeds require a period of afterippening, which widens environmental conditions conducive to germination [18]. Allen and others [2] found germination rate increased and dormancy levels decreased as the duration of dry storage increased. Desert squirreltail seed commonly show higher levels of dormancy than seed from mountain populations [18].

Squirreltail seeds may germinate without a period of afterippening, showing a partial state of dormancy. However mean germination time for recently harvested seeds is longer than for afterippened seeds.

Beckstead [19] evaluated the germination temperature requirements of recently harvested bottlebrush squirreltail seeds obtained from mountain and desert habitats. The greatest germination occurred primarily at 50/68 degrees Fahrenheit (10/20 °C) and 59/77 degrees Fahrenheit (15/25 °C), with higher temperatures of 68/86 degrees Fahrenheit (20/30 °C) inhibiting germination.

Environmental conditions and timing of phenological events greatly affect the probability of recently harvested squirreltail seed germination. Temperatures of 50/68 degrees Fahrenheit (10/20 °C) and 59/77 degrees Fahrenheit (15/25 °C) are unlikely to occur during summer months in desert habitats. In higher, mountain habitats, summer temperatures of 50/68 degrees Fahrenheit (10/20 °C) and 59/77 degrees Fahrenheit (15/25 °C) may occur; however, squirreltail usually ripens later at higher elevations [19]. In general, recently harvested squirreltail seeds at lower elevations have a much greater probability of fall germination than seeds from higher elevations [2].

Chabet and Billings [40] observed germination of squirreltail seeds from alpine sites (10,793 feet (3,290 m)) in the Sierra Nevada. The greatest germination (%) occurred at day/night temperatures of 81/73 degrees Fahrenheit (27/23 °C (96%)) and 90/82 degrees Fahrenheit (32/28 °C (92%)).

Successional Status

Depending upon habitat type, squirreltail may occur as an early, mid-, or late successional species.

Shrub Rangelands

Squirreltail is generally a dominant component of seral big sagebrush/bunchgrass communities [217]. Squirreltail is represented in early seral and climax stages of big sagebrush/bluebunch wheatgrass associations in Nevada. Tueller and Platou observed the most pronounced bottlebrush squirreltail during early and climax stages of big sagebrush/bluebunch wheatgrass associations in Nevada [190]. Squirreltail is found within seral and climax stages of big sagebrush rangelands in southeastern Idaho [4]. It is a component of climax big sagebrush communities in Idaho [205] and is a member of climax big sagebrush/western wheatgrass communities of Colorado [183]. Within shrub-steppe ecosystems of western Colorado, squirreltail is an early seral species [117]. Squirreltail also occurs in climax shadscale communities [100].

Pinyon-juniper Communities

Squirreltail is common in mid-seral and climax pinyon-juniper communities of Mesa Verde, Colorado [67,68]. Squirreltail is a component of seral and climax western juniper (Juniper occidentalis) communities of the Pacific Northwest [54].

Ponderosa Pine Communities

Squirreltail is a member of interior ponderosa pine climax communities within the central and southern Rocky Mountains [209].

Prior to invasion of nonnative annuals in the Snake River Plain, Idaho, squirreltail occupied a mid to late seral status, suppressing the early seral fescues, sixweeks fescue (Vulpia octoflora), and foxtail fescue (Vulpia myuros) [160].

Immediate Fire Effects

Although squirreltail is generally top-killed by fire, its small size and low density of coarse fuel per unit basal area make it relatively fire tolerant [31,198,208]. Low density of above ground plant tissue produces a quick, "hot" flame, transferring little heat to growing points below the soil surface [208,210]. The solid culms of squirreltail do not readily burn, compared to those of perennial grass associates [210].

A photo of low grasses growing with scattered shrubs in a somewhat dry, steppe-like area that appears to be transitioning to a weedy grassland after a fire.
Photo Credit
Photo by Matt Lavin, iNaturalist.org, some rights reserved.

Squirreltail growing with weedy annual grasses including cheatgrass and medusahead on a burned site in Elmore County, Idaho (CC BY 4.0).

Postfire Regeneration Strategy

  • Crown residual colonizer (on-site, initial community)
  • Secondary colonizer (on-site or off-site seed sources) [182]

Fire Adaptations

Squirreltail's small size, coarse stems, and sparse leafy material aid in its tolerance of fire [31]. Postfire regeneration occurs from surviving root crowns and from on- and off-site seed sources [29]. Frequency of disturbance greatly influences postfire response of squirreltail. Undisturbed plants within a 6 to 9 year age class generally contain large amounts of dead material, increasing squirreltail's susceptibility to fire [210].

Koniak [120] found squirreltail to be a major component of postfire pinyon-juniper communities of the Great Basin at any time during succession. Greatest occurrence and coverage of squirreltail are generally achieved during mid-seral stages.

Successional stageOccurrence (%)Percent of areas achieving > 5% cover
Early (1 year old)433
Early-mid (4-8 years old)5815
Mid (15-17 years old)4928
Late-mid (22-60 years old)900
Late > 60 years old440

Plant Response to Fire

Squirreltail sprouts from surviving root crown [29,201] and colonizes from seed [29].

Seasonal trends in squirreltail root carbohydrate reserves greatly affect postfire response. Burning is generally harmful during late spring and early summer [30,208] coinciding with low points in carbohydrate reserves [20]. Squirreltail is most tolerant of late summer (anthesis) or mid-fall (before regrowth) fires [30,49,79], coinciding with relatively high carbohydrate reserves [20]:

A graph with "percent of maximum" on the y-axis and "phenological stages - available energy in roots of squirreltail at several stages of maturity" on the x-axis. Peaks and valleys along the line are labeled "first growth", "2nd leaf", "3rd leaf", "anthesis", "seed ripe", "quiescent", "fall regrowth", and "winter dormancy".
Photo Credit
Image from [20].

A difference in phenological traits of surviving postfire individuals may exist between small (1 to 3 inch (2.5-7.6 cm) crown diameter) and large (>3.5 inches (8.9 cm) crown diameter) squirreltail plants. Wright [210] found large plants to produce significantly (p<0.01) higher numbers of flowering stalks than small plants after fire.

Wright [208] compared squirreltail response to burning and clipping near Boise, Idaho. Heat was applied by propane burner for 20 to 30 seconds to raise soil surface temperature to 400 or 800 degrees Fahrenheit. The 800 degree Fahrenheit treatment killed 25% of squirreltail plants during July and August. No other treatment caused mortality. Burning and clipping during all seasons reduced yields 1 year after treatment. Burning reduced yield most during May. Average herbage weight (in grams) per squirreltail plants in relation to season and treatment at 1 postfire year is summarized below:

Season400 °F800 °FClippedControl
May3.94a5.487.4122.58
June6.968.507.2622.09
July8.51a4.32ab13.2514.01
August7.50a9.4211.5816.61
September10.446.11ab10.2121.97

a Differences from clipped treatment significant at p<0.05

b Differences from 400 °F treatment significant at p<0.05

Wright [207] conducted time/temperature evaluations of squirreltail mortality on 5 dates between 19 May and 21 September, at temperatures between 120 to 200 degrees Fahrenheit (48.9-93.3 °C). Time required to kill squirreltail tissue at all temperatures within the test range increased as burning date increased. The greatest change occurred between 10 June and 21 July.

Time (minutes) required to kill squirreltail tissue at 172 degrees Fahrenheit (78 °C) [208]:

Date19 May10 June21 July20 August21 September
Time (minutes)4.005.5018.5028.0033.50

Fox [77] found a direct association between postfire response of squirreltail and ponderosa pine tree density and canopy cover. The greatest cover (%) of squirreltail was achieved in areas with larger (>4 inches (10 cm) diameter) trees and less dense tree canopies.

Blank and others [26] grew squirreltail under greenhouse conditions in soil from a July wildfire site and adjacent unburned areas within a big sagebrush habitat of Nevada. Squirreltail had greater aboveground biomass and more total N, P and K, along with greater silica content, when grown in soil collected from wildfire sites.

Spring

Early spring fire (May) within sagebrush ecosystems of eastern Oregon greatly reduced squirreltail basal area [31,32]. Basal area decreased an average of 47 % the 2nd postfire year. Britton and others [31] compared squirreltail postfire response in eastern Oregon to clipping. Yield (1 postfire year) after a May fire was less than yield from clipping (down to 0.4 inch (1 cm) stubble). Results the 2nd year showed no significant difference.

Squirreltail populations increased after a "moderate" spring (May 1972) wildfire in a ponderosa pine forest on limestone-sandstone derived soils, near flagstaff Arizona. The area observed was logged 2 years before, averaging 16,875 board feet/acre (6,750 board feet/ha). Number of bottlebrush squirreltail stems per hectare in 1972 and 1974 is summarized below in thousands/ha [17]:

YearModerate burnSevere burnControl (logged, not burned)
19727.200
197418.10.11.1

Although frequency of squirreltail was too low for statistical analysis, Champlin [42] reported no damage to squirreltail basal cover and height 2 postfire years after a spring fire in a big sagebrush community of northern California. Squirreltail vigor increased the 1st and 2nd postfire growing season in central Oregon, following a spring fire within a sagebrush-bitterbrush/bunchgrass plant community [1].

Summer

Squirreltail increased following an August wildfire in a big sagebrush community with an understory dominated by cheatgrass and Lyall's milkvetch (Astragalus lyallii) [95]. Significantly (p<0.01) greater biomass was achieved 1 postfire year after a 19 July prescribed fire in Oregon. At time of burn, bottlebrush squirreltail had entered summer quiescence with no green shoot material evident. Mean shoot biomass of burned plants was greater per unit crown area, compared to control. Burned plants also averaged 49% higher root biomass per unit crown area, producing a shoot:root biomass ratio of 1.73 compared to control plots at 0.43 shoot:root biomass. Burning also increased the proportion of reproductive culms; 74.8% of all shoots of burned plants produced reproductive culms compared to 14.3% for unburned plants [220].

Squirreltail showed a negative postfire response to summer (July) wildfire within a sagebrush rangeland in Utah, for the 2nd and 3rd postfire years compared to control [202]. Squirreltail decreased in abundance 1 postfire year after a summer (July) prescribed fire and after a lightning fire within a mountain mahogany-big sagebrush community [187].

Fall

Squirreltail maintained previous levels of production (kg/ha) 1 postfire year after an October fire in an aspen-bunchgrass community of northern Arizona. Although total vegetative production remained constant, percent cover and density of squirreltail were significantly higher. The October fire resulted in a large squirreltail population consisting of small individuals whose combined vegetative biomass equaled or exceeded preburn levels. Associated dominants, Arizona fescue and mountain muhly, decreased [86].

For further information on squirreltail response to fire, see Fire Case Studies, Lyon's Research Paper (Lyon 1971), and the following Research Project Summaries:

  • Response of vegetation to prescribed burning in a Jeffrey pine-California black oak woodland and a deergrass meadow at Cuyamaca State Park, California
  • Effects of fall and spring prescribed burning in sagebrush steppe in east-central Oregon
  • Vegetation response to restoration treatments in ponderosa pine-Douglas-fir forests of western Montana

Fire Regimes

Fire regimes for plant communities in which squirreltail occurs are summarized below. For additional fire regime information, search FEIS for this species by entering the species name on the Advanced Search page and selecting “Fire Regime” as the publication type.

Community or EcosystemDominant SpeciesFire Return Interval Range (years)
silver fir-Douglas-firAbies amabilis-Pseudotsuga menziesii var. menziesii>200
sagebrush steppeArtemisia tridentata/Pseudoroegneria spicata20-70 [33]
basin big sagebrushA. t. var. tridentata12-43 [170]
mountain big sagebrushA. t. var. vaseyana20-60 [7,37]
Wyoming big sagebrushA. t. var. wyomingensis10-70 (40)** [196,215]
saltbush-greasewoodAtriplex confertifolia-Sarcobatus vermiculatus<35 to <100
desert grasslandsBouteloua eriopoda and/or Pleuraphis mutica5-100
plains grasslandsBouteloua spp.<35
blue grama-needle-and-thread grass-western wheatgrassB. g.-Hesperostipa comata-Pascopyrum smithii<35
blue grama-buffalo grassB. g.-Buchloe dactyloides<35
grama-galleta steppeB. g.-Pleuraphis jamesii<35 to <100
blue grama-tobosa prairieB. g.-P. mutica<35 to <100
cheatgrassBromus tectorum<10
mountain-mahogany-Gambel oak scrubCercocarpus ledifolius-Quercus gambelii<35 to <100
western juniperJuniperus occidentalis20-70
Rocky Mountain juniperJ. scopulorum<35
Sierra lodgepole pine*Pinus contorta var. murrayana35-200
Rocky Mountain ponderosa pine*P. ponderosa var. scopulorum2-10
Arizona pineP. p. var. arizonica2-10
galleta-threeawn shrubsteppePleuraphis jamesii-Aristida purpurea<35 to <100
mesquite-buffalo grassProsopis glandulosa-Buchloe dactyloides<35
Texas savannaP. g. var. glandulosa<10 [33]
mountain grasslandsPseudoroegneria spicata3-40 (10)** [6]
Rocky Mountain Douglas-fir*Pseudotsuga menziesii var. glauca25-100
interior live oakQuercus wislizenii<35 [33]

*fire return interval varies widely; trends in variation are noted in the species summary

**(mean)

Fire Management Considerations

Humphrey and Schupp [103] compared squirreltail seedling emergence within burned and unburned cheatgrass dominated areas of the Great Basin, Utah. Greater seedling emergence (April) occurred on seeded burned areas compared to unseeded, within loamy fine sand (85% sand) sites. On a dune site with sandy soil (95% sand), seedling emergence occurred in March with no significant difference between burned and unburned sites. However, a significantly greater proportion of squirreltail seedlings survived on burned dune areas compared to unburned.

Seeding

Aerially applied seed mixture of mutton grass, prairie Junegrass, Indian ricegrass, slender wheatgrass (Elymus trachycaulus) and squirreltail aided in the reestablishment of squirreltail after a summer (August) wildfire within Mesa Verde National Park, Colorado [74]. Squirreltail was an important component 1, 2, [76] and 3 postfire years [75] in seeded areas, whereas no squirreltail was observed in unseeded areas [74].

Postfire recovery of squirreltail occurred after a summer (June 1956) wildfire in Arizona chaparral, aerially seeded with weeping lovegrass (Eragrostis curvula) and crested wheatgrass. Results shown that percent frequency of squirreltail within 9.6 foot (2.9 m) square plots increased steadily for 4 years postfire [157]:

Species19561957195819601961
squirreltail02.54.010.521.5
crested wheatgrass014.020.517.513.0
weeping lovegrass0.52.01.54.06.0

Seeding postfire pinyon-juniper communities of the Great Basin with desert wheatgrass (Agropyron desertorum), intermediate wheatgrass (Thinopyrum intermedium), and smooth brome (Bromus inermis) inhibits establishment of bottlebrush squirreltail [120].

Pinyon-juniper Communities

Four years after a late summer (July-August) wildfire in pinyon-juniper woodlands of Mesa Verde, Colorado, Erdman [67] found bottlebrush squirreltail as an important component. Squirreltail, along with Indian rice grass and mutton grass, assumed dominance after a 3-year annual grass/forb stage. At 25 postfire years, squirreltail is a member of climax stands.

Within pinyon-juniper ranges of west-central Utah, squirreltail is an important native perennial species at 5 to 6 postfire years [13].

A fire return interval less than 10 to 25 years should increase abundance of bottlebrush squirreltail in newly expanded (young) western juniper stands (Juniperus occidentalis) receiving greater than 14 inches (350 mm) precipitation, at elevations higher than 4,900 feet (1,500 m), in southwestern Idaho [35].

Squirreltail postfire response in a ponderosa pine forest of Arizona

Source

Vose, James M.; White, Alan S. 1991. Biomass response mechanisms of understory species the first year after prescribed burning in an Arizona ponderosa pine community. Forest Ecology and Management. 40(3/4): 175-187. [199].

Season/Severity Classification

This was a late October fire. The fire smoldered for several days and consumed the entire litter layer, with a total heat yield of 115,830 calories/ft2 (1600 kJ/m2).

Study Location

The prescribed fire took place within open sawtimber sites, pole sites, and sapling sites within a ponderosa pine (Pinus ponderosa)/Arizona fescue (Festuca arizonica) habitat type on the Fort Valley Experiment Forest near Flagstaff.

Prefire Vegetative Community

Site typeTree characteristics
Saw timber sites296 trees/acre (120 trees/ha)
Pole sitesaverage tree diameter of 5.9 inches (15cm) at 1,730 trees/ha
Sapling sitesaverage tree diameter 1.8 inches (4.5 cm) at 10,070 trees/ha

Target Species Phenological State

No entry.

Site Description

Ponderosa pine/Arizona fescue habitat type

Fire Description

The day of initiation, average temperature was between 57.2 and 64.4 degrees Fahrenheit (14-18 °C) and relative humidity was 21%.

Fire Effects on Target Species

Vegetative biomass within open saw timber sites, including surviving squirreltail plants and new seedlings, was approximately 3 times greater (P<0.05) on burn plots compared to control, 247 lbs (112 kg/ha) and 88 lbs (40 kg/ha) respectively. Surviving squirreltail plants within burned, open saw timber areas had more than twice the vegetative production. Seedling recruitment within open saw timber sites was also greater on burned than control plots. Burned open saw timber plots produced an average seedling biomass 15 times greater (p<0.05) than on control plots. Squirreltail in pole sites and sapling sites showed a more negative response to fire than in open sawtimber sites. Results for squirreltail are summarized below:

Plant typeBurn biomass (kg/ha)Control biomass (kg/ha)Density (plants/m2)Control density (plants/m2)
Open saw timber sites
all plants112.4540.069.065.74
residual plants96.0040.234.344.56
seedlings15.841.034.980.57
Pole sized sites
all plants18.9721.862.275.56
residual plants18.2318.642.053.41
seedlings0.783.170.281.99
Sapling sites
all plants14.0811.722.914.18
residual plants12.7710.641.962.97
seedlings1.360.771.140.52

No significant phenological differences were found between all burned areas and control.

Fire Management Implications

Overall response of squirreltail within pole and sapling stands was less than in open saw timber areas; however, the response of surviving plants in pole and sapling stands remained strong. Seedlings are generally more vulnerable to environmental changes than established plants. The postfire response of surviving squirreltail plants may result in an increased presence of bottlebrush squirreltail within later postfire stages.

Federal Status

None

Other Status

No entry.

Importance to Wildlife and Livestock

Squirreltail is a dietary component of several wildlife species. It is a minor component of bison and cattle summer diets within sagebrush rangelands of southern Utah [195]. Although of little importance, squirreltail may provide forage for mule deer [122,124]. Pronghorn of western Utah feed upon squirreltail [16]. Townsend's ground squirrels [211], Nuttall's cottontails [111,127], and black-tailed jackrabbits [5,72,112,127] all feed upon squirreltail.

In southeastern Oregon salt desert-shrub ranges, squirreltail is an important component of domestic livestock seasonal diets. Winter months show greatest use [83,140].

Palatability and Nutritional Value

Squirreltail is a very palatable winter forage for domestic sheep of Intermountain ranges. Domestic sheep relish the green foliage [104]. Overall, bottlebrush squirreltail is considered moderately palatable to livestock.

When present, the long sharp awns of squirreltail greatly reduce its palatability [150]. Mature awns may penetrate flesh around the mouth of grazing animals, producing inflammation [51,115]. Eye and ear injury may also occur [51].

Clary [44] compared chemical constituents (%) of squirreltail within open and timbered ponderosa pine overstories in Arizona. Greater digestibility and significantly (p<0.05) higher crude protein were found in open versus timbered overstories:

Chemical constituentOpenTimbered
Crude protein (%)169.7
Phosphorus (%)0.250.26
Ash (%)12.313.7
Digestibility (%)66.761

Bottlebrush squirreltail nutrient levels fluctuate throughout the growing season. Levels of S, P, and K usually drop from March to October. Amounts of Mg and Ca stay relatively the same with high points in spring, late summer, and early fall [152]. Overall, squirreltail is a poor source of phosphorus, carotene, and digestible protein, but a good source of energy [48]. The average chemical composition (%) of squirreltail in Great Basin desert ranges is summarized below [47]:

NutrientComposition (%)
Ether Extract2.6
Total protein4.5
Ash17.1
Lignin8.7
Cellulose37.5
Other Carbohydrates29.6
Phosphorus0.07
Gross energy1730 (kcal/lb)
Carotene0.5 (mg/lb)

Cover Value

The degree of environmental protection provided by squirreltail for wildlife species is as follows [58]:

AnimalUtahWyoming
PronghornPoorPoor
ElkPoorPoor
Mule deerPoorPoor
White-tailed deer—Poor
Small mammalsGoodGood
Small nongame birdsFairGood
Upland game birdsFairFair
WaterfowlPoorFair

Value for Rehabilitation of Disturbed Sites

Squirreltail is tolerant of disturbance [133]. The Bureau of Land Management, U.S. Department of the Interior, identifies bottlebrush squirreltail as a high priority species for restoring native plant diversity in the Great Basin and the Columbia River Plateau [90]. Squirreltail naturally colonizes disturbed sites in Yellowstone National Park and is a component of seed mixtures used for restoration of lodgepole pine communities [129]. Brown and Amacher [34] recommend squirreltail for use in restoration of disturbed arid to semi-arid, desert shrub and pinyon-juniper systems. Squirreltail is well adapted for seeding of Wyoming, black and low sagebrush communities of the Intermountain West, receiving 9 to 13 inches (229-330 mm) annual precipitation. Squirreltail grows well under rabbitbrush canopies in south-central Idaho rangelands [149].

Squirreltail inhabits xeric sandy soils (73.9% sand, 16.8% silt, 9.2% clay, 1.3% organic matter) of a 50-year-old abandoned tailings pond from a Pb-Zn-processing mill [41], and is recommended for seed mixtures used to reclaim strip mines in southeastern Montana [64].

The large ecological amplitude of squirreltail lends to ecotypic differentiation. Phenological differences in growth rate, root:shoot ratios, leaf area, and overall plant size exist between subspecies of squirreltail. Differences are directly related to subspecies distribution [100]. Squirreltail seed source should be considered when implementing revegetation projects. Arredondo and others [9] observed a higher root length-to-leaf area ratio in plants grown from seed collected from different environments. Differences in phenology between individuals of different habitats are common (see Seasonal Development).

Squirreltail seed is available commercially [103,104,134]. The United States Department of Agriculture (USDA), Utah Division of Wildlife Resources, in conjunction with the Intermountain Research Station, Forest Service, USDA, established squirreltail seed quality standards. Seed quality standards as of 1990 are summarized below [181]:

Seed unit1Acceptable purity (%)2Acceptable viability (%)2
spikelet with or without awns9085

1 Reproductive structure marketed as seed.

2 Purity (%) and germination (%) expected using seed quality testing rules in seeds of commercial quality.

Germinability of primed squirreltail seed significantly (p<0.05) decreases when dried and stored [89].

Competition with Invasive Weeds

The persistence of squirreltail in areas invaded by exotic weeds is well recognized. Bottlebrush squirreltail persists in areas infested with cheatgrass [9,18,99,100,103,188], medusahead (Taeniatherum caput-medusae) [9,96,169,213,216], and Japanese brome (Bromus japonicus) [166].

Squirreltail naturally invades rangelands dominated by cheatgrass and medusahead [9]. However, mechanisms behind squirreltail's ability to occupy weed-infested areas are not completely understood. Several studies have evaluated the persistence of squirreltail within cheatgrass infested ranges. Beckstead [18] found recently harvested bottlebrush squirreltail seeds from mountain brush and meadow sites to possess lower levels of dormancy than cheatgrass at higher temperatures, 68/86 degrees Fahrenheit (20/30 C), whereas the opposite was true of lower temperatures, 41/59 degrees Fahrenheit (5/15 C). Squirreltail at lower elevations (4,100 feet (1,250 m)) have a greater probability of autumn germination than cheatgrass [2]. Established squirreltail plants generally initiate growth before the rosettes of cheatgrass in desert rangelands of Nevada [188]. Beckstead [18] suggests fall seeding of squirreltail into cheatgrass infested rangelands.

Early spring growth and ability to grow at low temperatures contribute to the persistence of squirreltail among cheatgrass dominated ranges [100]. Bottlebrush squirreltail seedlings have the ability to grow roots at low soil temperatures, allowing for soil penetration similar to medusahead and cheatgrass in the northern regions of the Great Basin. Root development at low temperatures promotes squirreltail seedling establishment and effective competition with medusahead [96].

Bottlebrush squirreltail has potential to outcompete medusahead. Management goals often concentrate on protecting squirreltail seedlings from livestock and rabbits, along with maintaining a natural supply of seed [169]. Hironaka and Sindelar [98] evaluated squirreltail growth under greenhouse conditions, when closely associated with medusahead. Squirreltail plants (10 plants) were observed in combination with 0, 4, 12, 36, 108, and 324 medusahead/foot2. Squirreltail growth was not affected by medusahead until 5 weeks old, grown under densities of 108 and 324 medusahead/foot2. Although stunted, no squirreltail mortality was seen at all densities tested, whereas a large amount of medusahead mortality was observed in the 324 medusahead/foot2 level. Squirreltail acquired greater root carbohydrate reserves than medusahead under competitive conditions. Under proper management, Hironaka [96] suggests a successional sequence of cheatgrass to medusahead to squirreltail dominated sites for northern Great Basin areas receiving greater than 11 inches (279 mm) precipitation.

Rome and Eddelman [166] compared squirreltail seedling growth in competition with Japanese brome at densities of 0, 50, 100, 200, 400 Japanese brome/m2. Observations were made in Missoula, Montana at 23, 42, 56, 82, and 97 days following an 8 April seeding of squirreltail and Japanese brome. Squirreltail averaged 85% survival in areas without Japanese brome, compared to an average of 66% survival from areas with 100 to 400 Japanese brome/m2 (p<0.05). Overall, squirreltail under competition with Japanese brome showed the greatest competitive ability at 100 Japanese brome/m2.

Martlette and Anderson [131] observed poor squirreltail seed dispersal into adjacent crested wheatgrass (Agropyron cristatum) stands. Plant cover acted as a barrier restricting the dispersal capabilities of squirreltail.

Under greenhouse conditions, Schlatterer and Tisdale [172] found sagebrush leaf litter to significantly (p<0.05) decrease squirreltail germination compared to moss and rabbitbrush (Chrysothamnus spp.) litter. The average number of squirreltail seeds (20 seeds/pot) germinating under different litter treatments is summarized below:

Litter typeBig sagebrushMossRabbitbrushNo litter
Number of squirreltail seeds germinating (n=20)11.2518.7518.2518.25

Squirreltail will readily establish in pinyon-juniper tree litter when a fermentation layer is not present [69].

Robertson [165] observed seeded squirreltail within a big sagebrush habitat at 5,200 feet (1,585 m) in northern Nevada to be short lived, persisting for 5 years. Squirreltail persisted for 30 years following direct seeding within a big sagebrush/bluebunch wheatgrass site in south-central Idaho [148].

Other Uses

No entry.

Other Management Considerations

The addition of nitrogen to disturbed sagebrush communities in Colorado [141] and mountain meadows of Nevada [62] had no positive effect on squirreltail establishment. Squirreltail decreased after the addition of nutrients in the form of stabilized sewage sludge [78].

Squirreltail reproductive potential is adversely affected by jointworm larvae. Spears and Barr [179] found culm length, seed weight, germination (%), and germination rate all significantly lower (p<0.01) on squirreltail infested with jointworms compared to uninfested plants. Results are summarized below:

Larvae presenceInfestedUninfested
Culm length (cm)30.033.7
Leaf length (cm)22.023.1
# of spikelets59
Seed weight (mg 25 seeds)108.2162.5
Germination (%)20.066.0
Growth rate (Seedlings day -1 100 seeds -1)2.87.8

Rangelands

Squirreltail is a valuable winter range plant in the Great Basin [48], with leaves remaining green and succulent through the winter.

Squirreltail's total available root carbohydrate reserves are lowest in early spring (approximately 3rd leaf stage), and at the beginning of fall regrowth. Total available carbohydrates are highest after anthesis [50]. By the 4th leaf stage, squirreltail has replaced the carbohydrate reserves found in roots at the beginning of the growing season [20]. Wright [206] found squirreltail most tolerant to herbage removal at time of seed maturity, declining slightly after maturity before fall regrowth. In eastern Oregon, squirreltail is resistant to late season defoliation [31]

Squirreltail generally increases in abundance when moderately grazed or protected on the foothills of intermountain winter ranges [104]. Moderate trampling by livestock in big sagebrush rangelands of central Nevada enhanced squirreltail seedling emergence compared to untrampled conditions. Heavy trampling destroys germination sites and significantly (p<0.05) reduces germination, whereas moderate trampling may enhance germination [63].

Squirreltail is tolerant of grazing in big sagebrush rangelands of southeastern Idaho [4]. In sagebrush rangelands of western Utah, Cook and Child [46] found winter harvesting to have a minor effect on crown cover, whereas early spring (April 1, May 1) harvest greatly reduced squirreltail cover.

Squirreltail vegetative vigor was evaluated over 25 years within a sagebrush rangeland of southeastern Oregon excluded from grazing. Vigor of squirreltail increased significantly over the 25 year period, with the 1st decade showing slower growth than the 2nd. The average annual precipitation over the 25 years equaled 8.3 inches (210 mm) with 40% falling during April, May, and June. Winters were cold with snow cover from December to March. Summers were hot, occasionally exceeding 100 degrees Fahrenheit (38 °C) [3].

Squirreltail is commonly found in heavily grazed and browsed (cattle and deer) aspen stands of big sagebrush steppe in Wyoming [36].

McPherson and Wright [144] observed significantly (p<0.01) greater coverage of bottlebrush squirreltail on ungrazed versus grazed Pinchot juniper rangelands in western Texas. Within the ponderosa pine bunchgrass ranges of the central Rocky Mountains, squirreltail production is greatest under light and moderate grazing regimes [52]. Squirreltail is tolerant of heavy grazing in the ponderosa pine zone of the Coconino Plateau, Arizona, since its long, sharp awns are usually present to discourage grazing [8].

On shortgrass ranges of the central plains squirreltail is very tolerant of light to moderate grazing [118].

Silviculture

Climax western juniper stands are of mixed age, consisting of 1st year seedlings to trees several hundred years old. Seral stands are composed of predominately younger aged trees. In central Oregon, Vaitkus and Eddleman [194] observed significantly greater (p<0.05) squirreltail production when associated with large (older) trees compared to small trees. Production of bottlebrush squirreltail was also significantly greater (p<0.05) under juniper canopies compared to intercanopy zones. McPherson and others [143] observed significantly greater (p<0.01) squirreltail under Pinchot juniper canopies and at canopy edges compared to areas beyond canopy, within grazed and relict grasslands of western Texas. Evaluations by Tueller and Platou [190] lend supporting evidence (see Successional Status).

Squirreltail does not reduce ponderosa pine seedling growth. Two-year-old pine seedlings that were planted the 1st postfire spring, after a June wildfire in northern Arizona, were not affected in height or diameter by competition with squirreltail [66]. In Arizona ponderosa pine forests, seedlings normally gain dominance over squirreltail within 5 years [8].

Squirreltail drastically increased 4 years after a clear-cut within a lodgepole pine forest of northeastern Utah at 8,800 feet (2,700 m). Bottlebrush squirreltail showed the largest increase in vegetative production out of all grasses present [10]:

Graminoid species1976 (kg/ha)1980 (kg/ha)
Ross' sedge56.842.0
elk sedge2.14.4
Poa spp.10.240.7
squirreltail3.347.7
5 others013.9

Squirreltail was an early colonizer after the clear-cut of a ponderosa pine forest in north-central California [138].

Squirreltail populations were greatest 11 to 25 years after clearcuts of a red fir forest in the Sierra Nevada, California [73].

Everett and Sharow [70] found squirreltail seed production was less under singleleaf pinyon (Pinus monophylla)-Utah juniper woodland canopies than in clearcut areas (1 and 2 postharvest years).

Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.

Forest and Range Ecosystems

  • FRES20 Douglas-fir
  • FRES21 Ponderosa pine
  • FRES23 Fir-spruce
  • FRES26 Lodgepole pine
  • FRES28 Western hardwoods
  • FRES29 Sagebrush
  • FRES30 Desert shrub
  • FRES32 Texas savanna
  • FRES33 Southwestern shrubsteppe
  • FRES34 Chaparral-mountain shrub
  • FRES35 Pinyon-juniper
  • FRES36 Mountain grasslands
  • FRES38 Plains grasslands
  • FRES40 Desert grasslands
  • FRES44 Alpine [80]

BLM Physiographic Regions

  • 3 Southern Pacific Border
  • 4 Sierra Mountains
  • 5 Columbia Plateau
  • 6 Upper Basin and Range
  • 7 Lower Basin and Range
  • 8 Northern Rocky Mountains
  • 9 Middle Rocky Mountains
  • 10 Wyoming Basin
  • 11 Southern Rocky Mountains
  • 12 Colorado Plateau
  • 13 Rocky Mountain Piedmont
  • 14 Great Plains
  • 15 Black Hills Uplift [22]

Kuchler Plant Associations

  • K005 Mixed conifer forest
  • K007 Red fir forest
  • K008 Lodgepole pine-subalpine forest
  • K010 Ponderosa shrub forest
  • K011 Western ponderosa forest
  • K012 Douglas-fir forest
  • K016 Eastern ponderosa forest
  • K017 Black Hills pine forest
  • K018 Pine-Douglas-fir forest
  • K019 Arizona pine forest
  • K020 Spruce-fir-Douglas-fir forest
  • K021 Southwestern spruce-fir forest
  • K022 Great Basin pine forest
  • K023 Juniper-pinyon woodland
  • K024 Juniper steppe woodland
  • K026 Oregon oakwoods
  • K030 California oakwoods
  • K031 Oak-juniper woodland
  • K032 Transition between K031 and K037
  • K037 Mountain-mahogany-oak scrub
  • K038 Great Basin sagebrush
  • K039 Blackbrush
  • K040 Saltbush-greasewood
  • K041 Creosotebush
  • K046 Desert: vegetation largely lacking
  • K050 Fescue-wheatgrass
  • K052 Alpine meadows and barren
  • K053 Grama-galleta steppe
  • K054 Grama-tobosa prairie
  • K055 Sagebrush steppe
  • K056 Wheatgrass-needlegrass shrubsteppe
  • K057 Galleta-threeawn shrubsteppe
  • K059 Trans-Pecos shrub savanna
  • K060 Mesquite savanna
  • K064 Grama-needlegrass-wheatgrass
  • K065 Grama-buffalo grass
  • K066 Wheatgrass-needlegrass
  • K085 Mesquite-buffalo grass
  • K086 Juniper-oak savanna [121]

SAF Cover Types

  • 66 Ashe juniper-redberry (Pinchot) juniper
  • 68 Mesquite
  • 207 Red fir
  • 209 Bristlecone pine
  • 210 Interior Douglas-fir
  • 217 Aspen
  • 218 Lodgepole pine
  • 220 Rocky Mountain juniper
  • 229 Pacific Douglas-fir
  • 237 Interior ponderosa pine
  • 238 Western juniper
  • 239 Pinyon-juniper
  • 241 Western live oak
  • 242 Mesquite
  • 243 Sierra Nevada mixed conifer
  • 244 Pacific ponderosa pine-Douglas-fir
  • 246 California black oak
  • 250 Blue oak-foothills pine
  • 256 California mixed subalpine [71]

SRM Rangeland Cover Types

  • 101 Bluebunch wheatgrass
  • 102 Idaho fescue
  • 104 Antelope bitterbrush-bluebunch wheatgrass
  • 105 Antelope bitterbrush-Idaho fescue
  • 106 Bluegrass scabland
  • 107 Western juniper/big sagebrush/bluebunch wheatgrass
  • 108 Alpine Idaho fescue
  • 109 Ponderosa pine shrubland
  • 110 Ponderosa pine-grassland
  • 201 Blue oak woodland
  • 207 Scrub oak mixed chaparral
  • 210 Bitterbrush
  • 211 Creosotebush scrub
  • 212 Blackbush
  • 301 Bluebunch wheatgrass-blue grama
  • 310 Needle-and-thread-blue grama
  • 314 Big sagebrush-bluebunch wheatgrass
  • 315 Big sagebrush-Idaho fescue
  • 318 Bitterbrush-Idaho fescue
  • 320 Black sagebrush-bluebunch wheatgrass
  • 321 Black sagebrush-Idaho fescue
  • 322 Curlleaf mountain-mahogany-bluebunch wheatgrass
  • 401 Basin big sagebrush
  • 403 Wyoming big sagebrush
  • 405 Black sagebrush
  • 406 Low sagebrush
  • 407 Stiff sagebrush
  • 408 Other sagebrush types
  • 409 Tall forb
  • 410 Alpine rangeland
  • 412 Juniper-pinyon woodland
  • 413 Gambel oak
  • 414 Salt desert shrub
  • 415 Curlleaf mountain-mahogany
  • 416 True mountain-mahogany
  • 417 Littleleaf mountain-mahogany
  • 501 Saltbush-greasewood
  • 502 Grama-galleta
  • 503 Arizona chaparral
  • 504 Juniper-pinyon pine woodland
  • 509 Transition between oak-juniper woodland and mahogany-oak association
  • 607 Wheatgrass-needlegrass
  • 611 Blue grama-buffalo grass
  • 612 Sagebrush-grass
  • 614 Crested wheatgrass
  • 615 Wheatgrass-saltgrass-grama
  • 704 Blue grama-western wheatgrass
  • 712 Galleta-alkali sacaton
  • 713 Grama-muhly-threeawn
  • 714 Grama-bluestem
  • 715 Grama-buffalo grass
  • 718 Mesquite-grama
  • 727 Mesquite-buffalo grass
  • 735 Sideoats grama-sumac-juniper [176]

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