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SPECIES: Leymus ambiguus


Anderson, Michelle D. 2004. Leymus ambiguus. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: /database/feis/plants/graminoid/leyamb/all.html [].


Elymus ambiguus Vasey & Scribn. [13,15,24]


Colorado wildrye

The currently accepted scientific name of Colorado wildrye is Leymus ambiguus (Vasey & Scribn.) D.R. Dewey (Poaceae) [10,23,41,42].


No special status

Colorado wildrye is rare in Nevada [24].
Special consideration status for Colorado wildrye was considered and rejected in Idaho [35].


SPECIES: Leymus ambiguus
Colorado wildrye grows primarily along the east slope of the Rocky Mountains, from Montana south through Wyoming, Colorado, and New Mexico [7,10,23]. It has also been reported in Idaho [35], Utah [23], and Nevada [24].

Plants database provides a distributional map of Colorado wildrye.

FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES23 Fir-spruce
FRES29 Sagebrush
FRES34 Chaparral-mountain shrub
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES38 Plains grasslands

STATES/PROVINCES: (key to state/province abbreviations)


6 Upper Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau

K011 Western ponderosa forest
K012 Douglas-fir forest
K015 Western spruce-fir forest
K018 Pine-Douglas-fir forest
K021 Southwestern spruce-fir forest
K023 Juniper-pinyon woodland
K032 Transition between K031 and K037
K037 Mountain-mahogany-oak scrub
K038 Great Basin sagebrush
K055 Sagebrush steppe
K056 Wheatgrass-needlegrass shrubsteppe

206 Engelmann spruce-subalpine fir
210 Interior Douglas-fir
220 Rocky Mountain juniper
237 Interior ponderosa pine
239 Pinyon-juniper

301 Bluebunch wheatgrass-blue grama
302 Bluebunch wheatgrass-Sandberg bluegrass
303 Bluebunch wheatgrass-western wheatgrass
304 Idaho fescue-bluebunch wheatgrass
309 Idaho fescue-western wheatgrass
314 Big sagebrush-bluebunch wheatgrass
315 Big sagebrush-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
409 Tall forb
412 Juniper-pinyon woodland
413 Gambel oak
415 Curlleaf mountain-mahogany
416 True mountain-mahogany
417 Littleleaf mountain-mahogany
419 Bittercherry
420 Snowbrush
504 Juniper-pinyon pine woodland
509 Transition between oak-juniper woodland and mahogany-oak association

In Colorado, Colorado wildrye may dominate montane grassland communities or codominate shrub communities with Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) [9]. Common associates in Rocky Mountain juniper (Juniperus scopulorum)-big sagebrush (A. tridentata) communities include wax currant (Ribes cereum), sulphur-flower buckwheat (Eriogonum umbellatum), varileaf phacelia (Phacelia heterophylla), and Indian ricegrass (Achnatherum hymenoides) [1,20].

The following classifications identify Colorado wildrye as a plant community dominant:

Colorado [9,22]


SPECIES: Leymus ambiguus
The following description of Colorado wildrye provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g. [10,13,41,42]).

Colorado wildrye is a native, loosely caespitose perennial [10,13,21,23] that forms culms 12 to 43 inches (30-110 cm) tall [10,13].

Colorado wildrye leaves are mostly basal [10,13,21] and may be flat [10,41,42] or involute [13,15]. Leaves are 0.04 to 0.24 inch (1-6 mm) wide [13,15] and glabrous to sparsely pubescent [10]. Compared with the morphologically similar Salina wildrye (L. salinus), Colorado wildrye tends to be more lush in appearance due to its abundant vegetative growth and leafy culms [10].

Colorado wildrye spikes are erect and reach 3 to 7 inches (8-17 cm) long and 0.08 to 0.24 inch (2-6 mm) wide [10,13]. Spikelets may be paired or solitary at each node [10,13,41,42] and are 0.4 to 0.9 inch (10-23 mm) long [13]. Spikelets bear 2 to 10 flowers [10,13].

Colorado wildrye occasionally produces short rhizomes [10,21].


Colorado wildrye reproduces both by seed [28,36] and vegetative growth [10,21,28].

Breeding system: No information is available on this topic.

Pollination: No information is available on this topic.

Seed production: Limited data indicate Colorado wildrye exhibits "strong seed habits" [30], producing approximately 390 seeds per plant. There are approximately 6,875 seeds per pound (243 seeds/gram) [36].

Seed dispersal: No information is available on this topic.

Seed banking: No information is available on this topic.

Germination: No information is available on this topic.

Seedling establishment/growth: Initial seedling establishment of Colorado wildrye is generally high due to high germination rates and rapid seedling growth. Final establishment, however, is reportedly low, perhaps due to the xeric nature of most sites [30].

The growth of perennial range grasses can be described in 2 phases. The 1st phase is defined by the growth of vegetative shoots which is accelerated until the maximum growth rate is reached, after which the rate of growth declines. During this interval the inflorescence is differentiated from the apical meristem, thus initiating the 2nd growth period. The growth of the flower stalks is also accelerated, though the growth rate declines as the fruit ripens and the plant reaches maturity [28]. McCarty [28] found that growth of Colorado wildrye flower stalks progresses very slowly at first, with heads appearing in mid- to late June. As growth of the flower stalks accelerates, the dry weight of the plant is also greatly increased. Increases in dry weight slow in conjunction with flowering and the production of fruit. In general, increases in dry weight lag behind height growth. Adventitious root growth occurs in late July and lasts approximately 2 weeks, followed by secondary shoot growth [28].

Asexual regeneration: Colorado wildrye occasionally reproduces vegetatively from rhizomes [10,21,28].

Colorado wildrye is found on steep, rocky mountainsides [10,20,41,42] and other dry slopes [13,15,20]. It is often more common near the base of slopes than at the crest or middle of slopes [12,13]. Colorado wildrye occurs on all aspects but grows best on south-facing slopes [20]. In Colorado where it is most prevalent, Colorado wildrye grows from 5,200 to 8,500 feet (1,585-2,590 m) [14]. Soils are usually shallow and coarse-textured [20], though Colorado wildrye can grow in light sand to heavy clay soil [21].

Self-perpetuating stands of Colorado wildrye are indicative of climax conditions on rocky, xeric grassland sites along the Colorado Front Range [22].

Colorado wildrye growth ends in mid-September. Seeds are disseminated in early to mid-September [28].


SPECIES: Leymus ambiguus
Fire adaptations: Review of the available literature yielded no information pertaining specifically to the fire ecology or adaptations of Colorado wildrye. Further study is needed to clarify the relationship between fire and Colorado wildrye. Basin wildrye (L. cinereus) is a morphologically similar species, though it occurs on somewhat different sites and has a wider distribution. Information on fire ecology and adaptations of basin wildrye can be found in the FEIS species summary; it is unknown to what extent this information can be applied to Colorado wildrye.

Fire regimes: Fire return intervals for plant communities and ecosystems in which Colorado wildrye occurs are summarized below. 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".

Community or Ecosystem Dominant Species Fire Return Interval Range (years)
sagebrush steppe Artemisia tridentata/Pseudoroegneria spicata 20-70 [29]
Wyoming big sagebrush Artemisia tridentata var. wyomingensis 10-70 (40**) [39,45]
plains grasslands Bouteloua spp. < 35 [29,44]
curlleaf mountain-mahogany* Cercocarpus ledifolius 13-1,000 [6,33]
mountain-mahogany-Gambel oak scrub Cercocarpus ledifolius-Quercus gambelii < 35 to < 100
Rocky Mountain juniper Juniperus scopulorum < 35 [29]
wheatgrass plains grasslands Pascopyrum smithii < 5-47+ [29,31,44]
Engelmann spruce-subalpine fir Picea engelmannii-Abies lasiocarpa 35 to > 200 [3]
pinyon-juniper Pinus-Juniperus spp. < 35 [29]
Colorado pinyon Pinus edulis 10-400+ [17,19,25,29]
interior ponderosa pine* Pinus ponderosa var. scopulorum 2-30 [3,8,27]
mountain grasslands Pseudoroegneria spicata 3-40 (10**) [2,3]
Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [3,4,5]
oak-juniper woodland (Southwest) Quercus-Juniperus spp. < 35 to < 200 [29]
*fire return interval varies widely; trends in variation are noted in the species review

Rhizomatous herb, rhizome in soil
Tussock graminoid
Ground residual colonizer (on-site, initial community)
Initial off-site colonizer (off-site, initial community)


SPECIES: Leymus ambiguus
Little information is available regarding the effect of fire on Colorado wildrye, though it is presumably top-killed by fire. Colorado wildrye typically forms small, loosely caespitose bunches that grow in close aggregation [7,21]. This growth form suggests that Colorado wildrye may burn quickly, with little heat transferred downward into the crown. Typically, other bunchgrasses that are morphologically similar have basal buds at or just below the surface that are not subjected to prolonged heating and survive to resprout [44]. The occasionally rhizomatous nature of Colorado wildrye [10,21] also suggests some resistance to fire mortality.

No additional information is available on this topic.

Available literature does not address Colorado wildrye's response to fire. More research is needed regarding both fire effects and Colorado wildrye response. More is known about basin wildrye, a morphologically similar bunchgrass; however, the degree to which this information can be applied to Colorado wildrye is unknown. Basin wildrye is adapted to well-drained lowland and upland sites in the Great Basin, while Colorado wildrye is generally found on steep, xeric sites. For more information regarding fire effects on basin wildrye, see the FEIS species summary.

No additional information is available on this topic.

No additional information is available on this topic.


SPECIES: Leymus ambiguus
Colorado wildrye has a low tolerance to grazing and generally rates low in palatability, except perhaps in early spring [30].

Palatability/nutritional value: McCarty [28] found that the starch and sugar content of Colorado wildrye roots and stem bases reaches a maximum immediately following current seasonal growth, declines slightly during the dormant period, and reaches minimum levels during the formative stages of shoot development. For initial growth of both roots and shoots, Colorado wildrye depends completely on stored carbohydrates for energy and building material. The manufacture of carbohydrates begins relatively quickly, but this carbohydrate is used as fast as it is manufactured. Carbohydrate storage only begins when growth rates decrease [28]. Carbohydrate reserves are therefore directly related to growth rates, decreasing during rapid growth and increasing during slow growth [28,43]; however, temperature and the availability of water and nutrients also affect the seasonal variation of carbohydrate reserves [43].

Cover value: No information is available on this topic.

No information is available on this topic.

No information is available on this topic.

Field trials have demonstrated that Colorado wildrye has high survivability and forage production potential in the eastern Central Great Plains, perhaps indicating its usefulness in livestock production [40].

Leymus ambiguus: References

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2. Arno, Stephen F. 1980. Forest fire history in the Northern Rockies. Journal of Forestry. 78(8): 460-465. [11990]
3. Arno, Stephen F. 2000. Fire in western forest ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 97-120. [36984]
4. Arno, Stephen F.; Gruell, George E. 1983. Fire history at the forest-grassland ecotone in southwestern Montana. Journal of Range Management. 36(3): 332-336. [342]
5. Arno, Stephen F.; Scott, Joe H.; Hartwell, Michael G. 1995. Age-class structure of old growth ponderosa pine/Douglas-fir stands and its relationship to fire history. Res. Pap. INT-RP-481. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 25 p. [25928]
6. Arno, Stephen F.; Wilson, Andrew E. 1986. Dating past fires in curlleaf mountain-mahogany communities. Journal of Range Management. 39(3): 241-243. [350]
7. Atkins, Riley J.; Barkworth, Mary E.; Dewey, Douglas R. 1984. A taxonomic study of Leymus ambiguus and L. salinus (Poaceae: Triticeae). Systematic Botany. 9(3): 279-294. [2851]
8. Baisan, Christopher H.; Swetnam, Thomas W. 1990. Fire history on a desert mountain range: Rincon Mountain Wilderness, Arizona, U.S.A. Canadian Journal of Forest Research. 20: 1559-1569. [14986]
9. Baker, William L. 1984. A preliminary classification of the natural vegetation of Colorado. The Great Basin Naturalist. 44(4): 647-676. [380]
10. Barkworth, Mary E.; Atkins, Riley J. 1984. Leymus Hochst. (Gramineae: Triticeae) in North America: taxonomy and distribution. American Journal of Botany. 71(5): 609-625. [2889]
11. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. [434]
12. Brotherson, Jack D. 1999. Measured and inferred moisture gradient relationships across ecotone boundaries in shrub-dominated foothill communities. In: McArthur, E. Durant; Ostler, W. Kent; Wambolt, Carl L., compilers. Proceedings: shrubland ecotones; 1998 August 12-14; Ephraim, UT. Proceedings RMRS-P-11. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 40-48. [36060]
13. Cronquist, Arthur; Holmgren, Arthur H.; Holmgren, Noel H.; [and others]. 1977. Intermountain flora: Vascular plants of the Intermountain West, U.S.A. Vol. 6. The Monocotyledons. New York: Columbia University Press. 584 p. [719]
14. Dittberner, Phillip L.; Olson, Michael R. 1983. The plant information network (PIN) data base: Colorado, Montana, North Dakota, Utah, and Wyoming. FWS/OBS-83/86. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service. 786 p. [806]
15. Dorn, Robert D. 1984. Vascular plants of Montana. Cheyenne, WY: Mountain West Publishing. 276 p. [819]
16. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905]
17. Floyd, M. Lisa; Romme, William H.; Hanna, David D. 2000. Fire history and vegetation pattern in Mesa Verde National Park, Colorado, USA. Ecological Applications. 10(6): 1666-1680. [37590]
18. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; Lewis, Mont E.; Smith, Dixie R. 1977. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service. 68 p. [998]
19. Gottfried, Gerald J.; Swetnam, Thomas W.; Allen, Craig D.; [and others]. 1995. Pinyon-juniper woodlands. In: Finch, Deborah M.; Tainter, Joseph A., eds. Ecology, diversity, and sustainability of the Middle Rio Grande Basin. Gen. Tech. Rep. RM-GTR-268. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 95-132. [26188]
20. Hess, Karl; Alexander, Robert R. 1986. Forest vegetation of the Arapaho and Roosevelt National Forests in central Colorado: a habitat type classification. Res. Pap. RM-266. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 48 p. [1141]
21. Hitchcock, C. Leo; Cronquist, Arthur; Ownbey, Marion. 1969. Vascular plants of the Pacific Northwest. Part 1: Vascular cryptogams, gymnosperms, and monocotyledons. Seattle, WA: University of Washington Press. 914 p. [1169]
22. Johnston, Barry C. 1987. Plant associations of Region Two: Potential plant communities of Wyoming, South Dakota, Nebraska, Colorado, and Kansas. 4th ed. R2-ECOL-87-2. Lakewood, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Region. 429 p. [3519]
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25. Keeley, Jon E. 1981. Reproductive cycles and fire regimes. In: Mooney, H. A.; Bonnicksen, T. M.; Christensen, N. L.; [and others], technical coordinators. Fire regimes and ecosystem properties: Proceedings of the conference; 1978 December 11-15; Honolulu, HI. Gen. Tech. Rep. WO-26. Washington, DC: U.S. Department of Agriculture, Forest Service: 231-277. [4395]
26. Kuchler, A. W. 1964. United States [Potential natural vegetation of the conterminous United States]. Special Publication No. 36. New York: American Geographical Society. 1:3,168,000; colored. [3455]
27. Laven, R. D.; Omi, P. N.; Wyant, J. G.; Pinkerton, A. S. 1980. Interpretation of fire scar data from a ponderosa pine ecosystem in the central Rocky Mountains, Colorado. In: Stokes, Marvin A.; Dieterich, John H., technical coordinators. Proceedings of the fire history workshop; 1980 October 20-24; Tucson, AZ. Gen. Tech. Rep. RM-81. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 46-49. [7183]
28. McCarty, Edward C. 1935. Seasonal march of carbohydrates in Elymus ambiguus and Muhlenbergia gracilis, and their reaction under moderate grazing use. Plant Physiology. 10: 727-738. [9497]
29. Paysen, Timothy E.; Ansley, R. James; Brown, James K.; [and others]. 2000. Fire in western shrubland, woodland, and grassland ecosystems. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: Effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-volume 2. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 121-159. [36978]
30. Plummer, A. Perry; Christensen, Donald R.; Monsen, Stephen B. 1968. Restoring big-game range in Utah. Publ. No. 68-3. Ephraim, UT: Utah Division of Fish and Game. 183 p. [4554]
31. Quinnild, Clayton L.; Cosby, Hugh E. 1958. Relicts of climax vegetation on two mesas in western North Dakota. Ecology. 39(1): 29-32. [1925]
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33. Schultz, Brad W. 1987. Ecology of curlleaf mountain mahogany (Cercocarpus ledifolius) in western and central Nevada: population structure and dynamics. Reno, NV: University of Nevada. 111 p. Thesis. [7064]
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36. Stevens, O. A. 1957. Weights of seeds and numbers per plant. Weeds. 5: 46-55. [44071]
37. Stickney, Peter F. 1989. Seral origin of species originating in northern Rocky Mountain forests. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Fire Sciences Laboratory, Missoula, MT. 10 p. [20090]
38. U.S. Department of Agriculture, National Resource Conservation Service. 2004. PLANTS database (2004), [Online]. Available: /. [34262]
39. Vincent, Dwain W. 1992. The sagebrush/grasslands of the upper Rio Puerco area, New Mexico. Rangelands. 14(5): 268-271. [19698]
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