Overview

Distribution

National Distribution

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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More info for the term: presence

Sixweeks grama has a disjunct distribution. It is widely distributed in the Southwest, occurring from California east to Oklahoma and south to Oaxaca, Mexico [28,41,70,83]. Disjunct populations of sixweeks grama are noted in Montana [17,48]. Conflicting information is found within the literature, stating that sixweeks grama is both introduced [17] and native [48] to Montana. Sixweeks grama is considered rare in Oklahoma because of limited distribution and/or presence in low numbers in the state [40]. Grass Manual on the Web provides a distributional map of sixweeks grama in the United States. Sixweeks grama also occurs in Argentina [70].
  • 17. Dorn, Robert D. 1984. Vascular plants of Montana. Cheyenne, WY: Mountain West Publishing. 276 p. [819]
  • 28. Gould, Frank W. 1979. The genus Bouteloua (Poaceae). Annals of the Missouri Botanical Garden. 66: 348-416. [5758]
  • 70. Stomberg, Mark R.; Kephart, Paul; Yadon, Vern. 2001. Composition, invasibility, and diversity in coastal California grasslands. Madrono. 48(4): 236-252. [41371]
  • 83. Wiggins, Ira L. 1980. Flora of Baja California. Stanford, CA: Stanford University Press. 1025 p. [21993]
  • 40. Kartesz, John T.; Meacham, Christopher A. 1999. Synthesis of the North American flora (Windows Version 1.0), [CD-ROM]. Available: North Carolina Botanical Garden. In cooperation with the Nature Conservancy, Natural Resources Conservation Service, and U.S. Fish and Wildlife Service [2001, January 16]. [36715]
  • 41. Kartesz, John Thomas. 1988. A flora of Nevada. Reno, NV: University of Nevada. 1729 p. [In 3 volumes]. Dissertation. [42426]
  • 48. Mares, M. A.; Enders, F. A.; Kingsolver, J. M.; [and others]. 1977. Prosopis as a niche component. In: Simpson, B. B., ed. Mesquite: Its biology in two desert ecosystems. US/IBP Synthesis Series 4. Stroudsburg, PA: Dowden, Hutchinson & Ross, Inc: 123-149. [5194]

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States or Provinces

(key to state/province abbreviations)
UNITED STATES
AZ CA CO KS MT NV NM OK TX UT

MEXICO
Ags. B.C.N. B.C.S. Chih. Coah. Dgo. Gto. Gro. Hgo. N.L.
Oax. Pue. Qro. S.L.P. Sin. Son. Zac.

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Regional Distribution in the Western United States

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

BLM PHYSIOGRAPHIC REGIONS [5]:

3 Southern Pacific Border

6
Upper Basin and Range

7 Lower Basin and Range

11 Southern Rocky Mountains

12 Colorado Plateau

13 Rocky Mountain Piedmont

14 Great Plains

16 Upper Missouri Basin and Broken Lands
  • 5. 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]

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Physical Description

Morphology

Description

More info for the term: caryopsis

This description provides characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available: [6,7,14,16,17,26,29,30,32,41,42,48,51,59,80,85].

Sixweeks grama is a short-lived, warm season, native annual bunchgrass. It grows to an approximate height of 1 foot (0.3 m) [28,41,76]. The culms are tufted prostrate or spreading, 4 to 12 inches (10-30 cm) long. Leaves are 0.4 to 2.4 inches (1-6 cm) long and 1-1.5 mm wide, occurring sparingly along the culms [28,58]. The fruit is an awned caryopsis. Awns range from minute to as long as the fruit body. The fruit measures 4.0 to 6.5 mm long and weighs approximately 0.03 mg [33,82]. The inflorescence consists of 2 to 9 persistent branches that are 0.4 to 1.2 inches (1-3 cm) long, with 7 to 40 closely placed spikelets measuring 2.5 to 4 mm long [32,83].

In southern New Mexico and southern Arizona, sixweeks grama and Rothrock's grama, a perennial, often grow together and are mistaken as the same species. Sixweeks grama can be differentiated by its branched stems and shorter awns [14,28]. Keys for identification presented above will aid in proper identification of sixweeks grama.

  • 30. Harrington, H. D. 1964. Manual of the plants of Colorado. 2d ed. Chicago: The Swallow Press, Inc. 666 p. [6851]
  • 6. Booth, W. E. 1950. Flora of Montana. Part I: Conifers and monocots. Bozeman, MT: The Research Foundation at Montana State College. 232 p. [48662]
  • 7. Bowers, Janice E.; McLaughlin, Steven P. 1987. Flora and vegetation of the Rincon Mountains, Pima County, Arizona. Desert Plants. 8(2): 50-94. [495]
  • 16. Diggs, George M., Jr.; Lipscomb, Barney L.; O'Kennon, Robert J. 1999. Illustrated flora of north-central Texas. Sida Botanical Miscellany No. 16. Fort Worth, TX: Botanical Research Institute of Texas. 1626 p. [35698]
  • 17. Dorn, Robert D. 1984. Vascular plants of Montana. Cheyenne, WY: Mountain West Publishing. 276 p. [819]
  • 26. Goodrich, Sherel. 1986. Vascular plants of the Desert Experimental Range, Millard County, Utah. Gen. Tech. Rep. INT-209. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 72 p. [1033]
  • 28. Gould, Frank W. 1979. The genus Bouteloua (Poaceae). Annals of the Missouri Botanical Garden. 66: 348-416. [5758]
  • 29. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
  • 32. Hickman, James C., ed. 1993. The Jepson manual: Higher plants of California. Berkeley, CA: University of California Press. 1400 p. [21992]
  • 42. Kearney, Thomas H.; Peebles, Robert H.; Howell, John Thomas; McClintock, Elizabeth. 1960. Arizona flora. 2d ed. Berkeley, CA: University of California Press. 1085 p. [6563]
  • 51. Mauz, Kathryn. 1999. Flora of the Sawtooth Mountains, Pinal County, Arizona. Desert Plants. 15(2): 3-27. [38731]
  • 58. Munz, Philip A. 1974. A flora of southern California. Berkeley, CA: University of California Press. 1086 p. [4924]
  • 59. Nelson, A. B.; Herbel, H. M.; Jackson, H. M. 1970. Chemical composition of forage species grazed by cattle on an arid New Mexico range. Bulletin 561. Las Cruces, NM: New Mexico State University, Agricultural Experiment Station. 33 p. [4034]
  • 76. Van Dyne, George M. 1958. Ranges and range plants. Unpublished manuscript on file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. 290 p. [7310]
  • 80. Went, F. W. 1948. Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, California. Ecology. 29(3): 242-253. [12915]
  • 82. Wiens, John F. 2000. Vegetation and flora of Ragged Top, Pima County, Arizona. Desert Plants. 16(2): 3-31. [39488]
  • 83. Wiggins, Ira L. 1980. Flora of Baja California. Stanford, CA: Stanford University Press. 1025 p. [21993]
  • 85. Wright, Henry A. 1980. The role and use of fire in the semidesert grass-shrub type. Gen. Tech. Rep. INT-85. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 24 p. [2616]
  • 41. Kartesz, John Thomas. 1988. A flora of Nevada. Reno, NV: University of Nevada. 1729 p. [In 3 volumes]. Dissertation. [42426]
  • 14. 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]
  • 33. Hitchcock, A. S. 1951. Manual of the grasses of the United States. Misc. Publ. No. 200. Washington, DC: U.S. Department of Agriculture, Agricultural Research Administration. 1051 p. [2nd edition revised by Agnes Chase in two volumes. New York: Dover Publications, Inc.]. [1165]
  • 48. Mares, M. A.; Enders, F. A.; Kingsolver, J. M.; [and others]. 1977. Prosopis as a niche component. In: Simpson, B. B., ed. Mesquite: Its biology in two desert ecosystems. US/IBP Synthesis Series 4. Stroudsburg, PA: Dowden, Hutchinson & Ross, Inc: 123-149. [5194]

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Physical Description

Annuals, Terrestrial, not aquatic, Stolons or runners present, Stems trailing, spreading or prostrate, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath hairy at summit, throat, or collar, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades very narrow or filiform, less than 2 mm wide, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blades mostly glabrous, Ligule present, Ligule a fringed, ciliate, or lobed membrane, Inflorescence terminal, Inflorescence with 2 or more spikes, fascicles, glomerules, heads, or clusters per culm, Inflorescence a panicle with narrowly racemose or spicate branches, Inflorescence with 2-10 branches, Inflorescence branches 1-sided, Inflorescence branches terminating in bristle or point, Flowers bisexual, Spikelets sessile or subsessile, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets secund, in rows on one side of rachis, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes distinctly unequal, Glumes equal to or longer than adjacent l emma, Glume equal to or longer than spikelet, Glumes 1 nerved, Lemma coriaceous, firmer or thicker in texture than the glumes, Lemma 3 nerved, Lemma glabrous, Lemma body or surface hairy, Lemma apex dentate, 3-5 fid, Lemma teeth unequal. central tooth longer, Lemma distinctly awned, more than 2-3 mm, Lemma with 3 awns, Lemma awn less than 1 cm long, Lemma margins thin, lying flat, Lemma straight, Palea present, well developed, Palea membranous, hyaline, Palea shorter than lemma, Palea 2 nerved or 2 keeled, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.
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Dr. David Bogler

Source: USDA NRCS PLANTS Database

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Type Information

Isotype for Chondrosium subscorpioides Müll. Hal.
Catalog Number: US 883457
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of alleged type specimen
Preparation: Pressed specimen
Collector(s): G. W. Barclay
Locality: California / Texas, United States, North America
  • Isotype: Müller, J. K. 1856. Bot. Zeitung (Berlin). 14: 347.
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Type fragment for Chondrosium polystachyum Benth.
Catalog Number: US 865566A
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of alleged type specimen
Preparation: Pressed specimen
Collector(s): G. W. Barclay
Locality: Bay of Magdalena., Baja California Sur, Mexico, North America
  • Type fragment: Bentham, G. 1844. Bot. Voy. Sulphur. 56.
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Type fragment for Bouteloua barbata Lag.
Catalog Number: US 865567A
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of alleged type specimen
Preparation: Pressed specimen
Collector(s): Collector unknown
Locality: E of Monserrat, Mexico, Central America
  • Type fragment: Lagger, F. J. 1805. Varied. Ci. 4: 141.
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Isotype for Bouteloua pumila Buckley
Catalog Number: US 81706
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of alleged type specimen
Preparation: Pressed specimen
Collector(s): C. H. Wright
Year Collected: 1849
Locality: W. Texas to El Paso, New Mexico., New Mexico / Texas, United States, North America
  • Isotype: Buckley, S. B. 1862. Proc. Acad. Nat. Sci. Philadelphia. 14: 93.
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Syntype for Bouteloua polystachya var. major Vasey in G.M. Wheeler
Catalog Number: US 81711
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Preparation: Pressed specimen
Collector(s): J. T. Rothrock
Year Collected: 1874
Locality: Sannoita Valley., Arizona, United States, North America
Elevation (m): 1676 to 1676
  • Syntype: Wheeler, G. M. 1878. Rep. U.S. Geogr. Surv. Meridian. 6: 287.
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Holotype for Bouteloua rothrockii Vasey
Catalog Number: US 81709
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of alleged type specimen
Preparation: Pressed specimen
Collector(s): J. T. Rothrock
Year Collected: 1874
Locality: Cottonwood., Yavapai, Arizona, United States, North America
  • Holotype: Vasey, G. 1893. Contr. U.S. Natl. Herb. 1 (8): 268.
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Holotype for Bouteloua micrantha Scribn. & Merr.
Catalog Number: US 81724
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Card file verified by examination of alleged type specimen
Preparation: Pressed specimen
Collector(s): D. Griffiths
Year Collected: 1900
Locality: Fort Lowell., Arizona, United States, North America
  • Holotype: Scribner, F. L. & Merrill, E. D. 1901. U.S.D.A. Div. Agrostol. Circ. 32: 8.
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Ecology

Habitat

Habitat characteristics

More info for the terms: natural, shrubs, tree

Sixweeks grama predominantly occurs on dry sites [14,16,28,42]. In Utah it has been observed growing on moist sites, often in disturbed intermittent watercourses at low elevations [14,79]. This grass is commonly found on mesas, rocky and sandy hillsides, steep slopes, gravelly and sandy washes, open, "waste," and disturbed ground in desert communities dominated by creosote bush and other desert shrubs [7,28,30,41,48,54,59,62]. In the grassland rolling hills and prairies of Kansas, Oklahoma, and Texas, sixweeks grama thrives along roadsides, railroads, and "waste places" [16,29].

Soils: Loamy to sandy and gravelly soils composed of lithic sandstone and granite are most often associated with sixweeks grama [7,16,29,41,57,58].

Climate:

The natural habitat of sixweeks grama is normally one of low rainfall, hot summer temperatures, high evaporation, and high winds typical of desert ecosystems.  In the deserts of the southwestern United States, maximum summer temperatures can exceed 110 °F (43 °C) and winter lows can drop to 10 °F (-12 °C) [10,11,52,82,82,84]. Precipitation is commonly distributed in a bimodal pattern, with heavy rains falling in spring and summer and gentler rains in winter. In these arid environments, average yearly precipitation can range from 8.5 to 10 inches (216-254 mm) with extremes of 0.74 to 22.9 inches (19-581 mm) recorded [10,11,52,82,84]. Where sixweeks grama grows on the grasslands of Texas, average yearly precipitation is 7.0 inches (178 mm) with an extreme temperature range of 11 °F to 114 °F (-12 °C to 456 °C) [15].

Elevation: The range of elevations for sixweeks grama in several states is presented below:

Arizona 1,000 to 5,500 feet (300-1,700 m) overall [10,42,51,61]
<3,200 feet (1,000 m) in the Rincon Mts.[7]
1,640 to 1,750 feet (500-530 m) in the Sawtooth Mts. [51]
2,165 to 3,907 feet (660-1,191 m) on Ragged Top Peak [84]
California <5,000 feet (1,500 m)  overall [32,58]
2,500 to 5,000 feet (800-1,500 m) in Joshua Tree National Monument [80]
Colorado 4,250 to 7,100 feet (1,295-2,160 m) overall [30,50,57]
Nevada 1,000 to 5,600 feet (300-1,700 m) overall [41]
New Mexico <7,000 feet (2,100 m) overall [24]
Fort Bayard Range, 1,800 to 2,560 feet (550-780 m) [53]
Texas <4,000 feet (1,219 m) in Brewster County [15]
Utah 2,800 to 6,000 feet (850-1,800 m) overall  [80]
  • 52. McPherson, Guy R. 1995. The role of fire in the desert grasslands. In: McClaran, Mitchel P.; Van Devender, Thomas R., eds. The desert grassland. Tucson, AZ: The University of Arizona Press: 130-151. [26576]
  • 30. Harrington, H. D. 1964. Manual of the plants of Colorado. 2d ed. Chicago: The Swallow Press, Inc. 666 p. [6851]
  • 7. Bowers, Janice E.; McLaughlin, Steven P. 1987. Flora and vegetation of the Rincon Mountains, Pima County, Arizona. Desert Plants. 8(2): 50-94. [495]
  • 10. Buegge, J. Jeremy. 2001. Flora of the Santa Teresa Mountains in Graham County, Arizona. Journal of the Arizona-Nevada Academy of Science. 33(2): 132-149. [45078]
  • 11. Campbell, R. S.; Bomberger, E. H. 1934. The occurrence of Gutierrezia sarothrae on Bouteloua eriopoda ranges in southern New Mexico. Ecology. 15(1): 49-61. [596]
  • 15. Denyes, H. Arliss. 1956. Natural terrestrial communities of Brewster County, Texas. The American Midland Naturalist. 55(2): 289-320. [26765]
  • 16. Diggs, George M., Jr.; Lipscomb, Barney L.; O'Kennon, Robert J. 1999. Illustrated flora of north-central Texas. Sida Botanical Miscellany No. 16. Fort Worth, TX: Botanical Research Institute of Texas. 1626 p. [35698]
  • 24. Gay, Charles W., Jr.; Dwyer, Don D. 1965. New Mexico range plants. Circular 374. Las Cruces, NM: New Mexico State University, Cooperative Extension Service. 85 p. [4039]
  • 28. Gould, Frank W. 1979. The genus Bouteloua (Poaceae). Annals of the Missouri Botanical Garden. 66: 348-416. [5758]
  • 29. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
  • 32. Hickman, James C., ed. 1993. The Jepson manual: Higher plants of California. Berkeley, CA: University of California Press. 1400 p. [21992]
  • 42. Kearney, Thomas H.; Peebles, Robert H.; Howell, John Thomas; McClintock, Elizabeth. 1960. Arizona flora. 2d ed. Berkeley, CA: University of California Press. 1085 p. [6563]
  • 50. Martin, William C.; Hutchins, Charles R. 1981. A flora of New Mexico. Volume 2. Germany: J. Cramer. 2589 p. [37175]
  • 51. Mauz, Kathryn. 1999. Flora of the Sawtooth Mountains, Pinal County, Arizona. Desert Plants. 15(2): 3-27. [38731]
  • 53. Medina, Alvin L. 1987. Woodland communities and soils of Fort Bayard, southwestern New Mexico. Journal of the Arizona-Nevada Academy of Science. 21: 99-112. [3978]
  • 57. Muldavin, Esteban H.; De Velice, Robert L.; Ronco, Frank, Jr. 1996. A classification of forest habitat types: southern Arizona and portions of the Colorado Plateau. RM-GTR-287. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 130. [27968]
  • 58. Munz, Philip A. 1974. A flora of southern California. Berkeley, CA: University of California Press. 1086 p. [4924]
  • 59. Nelson, A. B.; Herbel, H. M.; Jackson, H. M. 1970. Chemical composition of forage species grazed by cattle on an arid New Mexico range. Bulletin 561. Las Cruces, NM: New Mexico State University, Agricultural Experiment Station. 33 p. [4034]
  • 79. Welsh, Stanley L.; Atwood, N. Duane; Goodrich, Sherel; Higgins, Larry C., eds. 1987. A Utah flora. The Great Basin Naturalist Memoir No. 9. Provo, UT: Brigham Young University. 894 p. [2944]
  • 80. Went, F. W. 1948. Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, California. Ecology. 29(3): 242-253. [12915]
  • 82. Wiens, John F. 2000. Vegetation and flora of Ragged Top, Pima County, Arizona. Desert Plants. 16(2): 3-31. [39488]
  • 84. Wolden, Lynn; Stromberg, Julie; Patten, Duncan; Richter, Holly. 1990. Understory restoration in three riparian forest types. Restoration & Management Notes. 8(2): 116-117. [13790]
  • 62. 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]
  • 41. Kartesz, John Thomas. 1988. A flora of Nevada. Reno, NV: University of Nevada. 1729 p. [In 3 volumes]. Dissertation. [42426]
  • 14. 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]
  • 48. Mares, M. A.; Enders, F. A.; Kingsolver, J. M.; [and others]. 1977. Prosopis as a niche component. In: Simpson, B. B., ed. Mesquite: Its biology in two desert ecosystems. US/IBP Synthesis Series 4. Stroudsburg, PA: Dowden, Hutchinson & Ross, Inc: 123-149. [5194]
  • 54. Milton, Suzanne J.; Dean, W. R. J.; Kerley, G. I. H.; [and others]. 1998. Dispersal of seeds as nest material by the cactus wren. The Southwestern Naturalist. 43(4): 449-452. [29454]
  • 61. Nichol, A. A. [revisions by Phillips, W. S.]. 1952. The natural vegetation of Arizona. Tech. Bull. 68 [Revised]. Tucson, AZ: University of Arizona, Agricultural Experiment Station: 189-230. [3928]

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Key Plant Community Associations

More info for the terms: association, codominant, constancy, density, shrub, shrubs, tree, xeric

Sixweeks grama occurs primarily in southwestern desert shrubland, chaparral-mountain shrub,
and desert grassland communities [8,10,12,36,37,52,54,58,59,62,78,84].
It also occurs in  plains
grasslands [4,16,17,44,48,61]. Literature
on sixweeks grama focuses largely on its occurrence in Arizona and New Mexico.

Arizona: Warren and others [77] describe sixweeks grama as common and
widespread in Arizona, although not a dominant species. In the Sonoran Desert, sixweeks grama is
found in desert chaparral, pinyon-juniper (Pinus-Juniperus spp.)
woodland [4,10,61], creosotebush (Larrea
tridentata) [4,36,61], and mesquite (Prosopis spp.) bosque [48,61,84] communities. Sixweeks grama grows
alongside needle grama (Bouteloua aristidoides) and the dominant grass
species Rothrock's grama in the yellow palo verde-white bursage-saguaro (Parkinsonia
microphylla-Ambrosia dumosa-Carnegiea gigantea) vegetation type in the
eastern Sonoran Desert [39,61]. In the Santa Teresa Mountains, sixweeks grama
occurs in the understory of the Madrean evergreen woodlands. This xeric part of
the range has coarse soils and is composed mainly of Emory oak (Quercus
emoryi), gray oak (Q. grisea), and alligator juniper (Juniperus
deppeana) [10]. In ponderosa pine/pointleaf
manzanita (Pinus ponderosa/Arctostaphylos pungens) forests in southern Arizona and
portions of the Colorado plateau, sixweeks grama is found at
<1% density/cover. The understory is dominated by alligator juniper and
Colorado pinyon (Pinus edulis) [57].
California: Sixweeks grama grows from creosotebush scrub up to pinyon-juniper
woodland [58] in the Colorado and
east Mojave deserts
[37]. Below 3,900 feet (1,200 m) in Joshua Tree National Monument, California, sixweeks grama is found with the dominant
shrubs creosotebush and desertholly (Atriplex hymenelytra). At
approximately 5,000
feet (1,500 m), it grows with singleleaf pinyon (P. monophylla) and
junipers; and between 3,300 and 5,000 feet (1,000-1,500 m), it occurs
in Joshua tree (Yucca brevifolia) woodland [38,80,81].
Nevada: Sixweeks grama is found in the creosotebush belt of southern
Nevada, primarily with croton (Croton spp.), blackbrush (Coleogyne
ramosissima),
desert-thorn (Lycium
spp.), saltbush (Atriplex) spp., and hopsage (Grayia) spp. [41].
Literature on sixweeks grama occurrence in Nevada is limited.
New Mexico: Sixweeks grama occurs in the Chihuahuan Desert within
creosotebush and desert grassland communities. Other species common in the
creosotebush and grassland communities include desertholly, broom snakeweed (Gutierrezia
sarothrae), honey mesquite (Prosopis
glandulosa), tarbush (Flourensia
cernua), silver leaf
nightshade (Solanum eleagnifolium), bush muhly (Muhlenbergia
porteri), burro grass (Scleropogon brevifolius), black grama (Bouteloua eriopoda), poverty threeawn (Aristida
divaricata), tobosa (Pleuraphis mutica), and low woolly grass (Erioneuron pulchellum) [25,44,59,78].  In the Fort Bayard area of southwestern New
Mexico, sixweeks grama grows in 3 plant communities: 1) oneseed juniper (Juniperus monosperma)-Colorado
pinyon with 0.1% density and 14% constancy; 2) Colorado pinyon-alligator
juniper with trace density and 4% constancy; and 3) gray oak with 0.1% density
and 11% constancy [53]. Nelson [60] lists sixweeks grama as a
prominent annual grass in black grama communities of the Jornada
Experimental Range, located in the southern part of the state.
Texas: Sixweeks grama is found in Cross Timbers, prairie, rolling plains,
and other dry grassland communities [15,16]. Denyes [15] describes sixweeks
grama as a codominant grass in the shortgrass association in the plains
grasslands of Brewster County. Other dominant
shortgrasses include blue grama (Bouteloua gracilis), hairy grama (B.
hirsuta), black grama, purple threeawn (Aristida purpurea), Wright's
threeawn (A. p. var. wrightii), blue
threeawn (A. glauca), and Wooton's threeawn (A. pansa). Oneseed juniper is
a common tree, and honey mesquite and javelin bush (Microrhamnus ericoides) are common
shrubs in the shortgrass association. 

Utah: Sixweeks grama grows within desert shrub and creosote bush communities [79].
Literature on sixweeks grama occurrence in Utah is limited.

  • 52. McPherson, Guy R. 1995. The role of fire in the desert grasslands. In: McClaran, Mitchel P.; Van Devender, Thomas R., eds. The desert grassland. Tucson, AZ: The University of Arizona Press: 130-151. [26576]
  • 4. Barbour, Michael G.; Burk, Jack H.; Pitts, Wanna D. 1980. Major vegetation types of North America. In: Barbour, Michael G.; Burk, Jack H.; Pitts, Wanna D. Terrestrial plant ecology. Menlo Park, CA: The Benjamin/Cummings Publishing Company, Inc: 486-583. [45729]
  • 8. Brown, David E. 1982. Sonoran savanna grassland. In: Brown, David E., ed. Biotic communities of the American Southwest--United States and Mexico. Desert Plants. 4(1-4): 137-141. [8897]
  • 10. Buegge, J. Jeremy. 2001. Flora of the Santa Teresa Mountains in Graham County, Arizona. Journal of the Arizona-Nevada Academy of Science. 33(2): 132-149. [45078]
  • 12. Carmichael, R. S.; Knipe, O. D.; Pase, C. P.; Brady, W. W. 1978. Arizona chaparral: plant associations and ecology. Res. Pap. RM-202. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 16 p. [3038]
  • 15. Denyes, H. Arliss. 1956. Natural terrestrial communities of Brewster County, Texas. The American Midland Naturalist. 55(2): 289-320. [26765]
  • 16. Diggs, George M., Jr.; Lipscomb, Barney L.; O'Kennon, Robert J. 1999. Illustrated flora of north-central Texas. Sida Botanical Miscellany No. 16. Fort Worth, TX: Botanical Research Institute of Texas. 1626 p. [35698]
  • 17. Dorn, Robert D. 1984. Vascular plants of Montana. Cheyenne, WY: Mountain West Publishing. 276 p. [819]
  • 25. Gibbens, Robert P.; Beck, Reldon F. 1988. Changes in grass basal area and forb densities over a 64-year period on grassland types of the Jornada Experimental Range. Journal of Range Management. 41(3): 186-192. [5227]
  • 36. Jackson, Laura L.; McAuliffe, Joseph R.; Roundy, Bruce A. 1991. Desert restoration. Restoration & Management Notes. 9(2): 71-79. [22746]
  • 37. Johnson, Hyrum B. 1976. Vegetation and plant communities of southern California deserts--a functional view. In: Latting, June, ed. Symposium proceedings: plant communities of southern California; 1974 May 4; Fullerton, CA. Special Publication No. 2. Berkeley, CA: California Native Plant Society: 125-164. [1278]
  • 38. Juhren, Marcella; Went, F. W.; Phillips, Edwin. 1956. Ecology of desert plants. IV. Combined field and laboratory work on germination of annuals in the Joshua Tree National Monument, California. Ecology. 37(2): 318-330. [12975]
  • 39. Karpiscak, Martin M. 1980. Secondary succession of abandoned field vegetation in southern Arizona. Tucson, AZ: University of Arizona. 219 p. Dissertation. [53608]
  • 44. Kemp, Paul R. 1983. Phenological patterns of Chihuahuan Desert plants in relation to the timing of water availability. Journal of Ecology. 71: 427-436. [5054]
  • 53. Medina, Alvin L. 1987. Woodland communities and soils of Fort Bayard, southwestern New Mexico. Journal of the Arizona-Nevada Academy of Science. 21: 99-112. [3978]
  • 57. Muldavin, Esteban H.; De Velice, Robert L.; Ronco, Frank, Jr. 1996. A classification of forest habitat types: southern Arizona and portions of the Colorado Plateau. RM-GTR-287. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 130. [27968]
  • 58. Munz, Philip A. 1974. A flora of southern California. Berkeley, CA: University of California Press. 1086 p. [4924]
  • 59. Nelson, A. B.; Herbel, H. M.; Jackson, H. M. 1970. Chemical composition of forage species grazed by cattle on an arid New Mexico range. Bulletin 561. Las Cruces, NM: New Mexico State University, Agricultural Experiment Station. 33 p. [4034]
  • 60. Nelson, Enoch W. 1934. The influence of precipitation and grazing upon black grama grass range. Technical Bulletin No. 409. Washington, DC: U.S. Department of Agriculture. 32 p. [4175]
  • 77. Warren, Peter L.; Hoy, Marina S.; Hoy, Wilton E. 1992. Vegetation and flora of Fort Bowie National Historic Site, Arizona. Tech. Rep. NPS/WRUA/NRTR-92/43. Tucson, AZ: The University of Arizona, School of Renewable Natural Resources, Cooperative National Park Resources Studies Unit. 78 p. [19871]
  • 78. Welsh, Richard G.; Beck, Reldon F. 1976. Some ecological relationships between creosotebush and bush muhly. Journal of Range Management. 29(6): 472-475. [3970]
  • 79. Welsh, Stanley L.; Atwood, N. Duane; Goodrich, Sherel; Higgins, Larry C., eds. 1987. A Utah flora. The Great Basin Naturalist Memoir No. 9. Provo, UT: Brigham Young University. 894 p. [2944]
  • 80. Went, F. W. 1948. Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, California. Ecology. 29(3): 242-253. [12915]
  • 81. Went, F. W.; Westergaard, M. 1949. Ecology of desert plants. III. Development of plants in the Death Valley National Monument, California. Ecology. 30(1): 26-38. [11102]
  • 84. Wolden, Lynn; Stromberg, Julie; Patten, Duncan; Richter, Holly. 1990. Understory restoration in three riparian forest types. Restoration & Management Notes. 8(2): 116-117. [13790]
  • 62. 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]
  • 41. Kartesz, John Thomas. 1988. A flora of Nevada. Reno, NV: University of Nevada. 1729 p. [In 3 volumes]. Dissertation. [42426]
  • 48. Mares, M. A.; Enders, F. A.; Kingsolver, J. M.; [and others]. 1977. Prosopis as a niche component. In: Simpson, B. B., ed. Mesquite: Its biology in two desert ecosystems. US/IBP Synthesis Series 4. Stroudsburg, PA: Dowden, Hutchinson & Ross, Inc: 123-149. [5194]
  • 54. Milton, Suzanne J.; Dean, W. R. J.; Kerley, G. I. H.; [and others]. 1998. Dispersal of seeds as nest material by the cactus wren. The Southwestern Naturalist. 43(4): 449-452. [29454]
  • 61. Nichol, A. A. [revisions by Phillips, W. S.]. 1952. The natural vegetation of Arizona. Tech. Bull. 68 [Revised]. Tucson, AZ: University of Arizona, Agricultural Experiment Station: 189-230. [3928]

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Habitat: Rangeland Cover Types

More info on this topic.

This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):

More info for the terms: cover, shrub

SRM (RANGELAND) COVER TYPES [68]:



207 Scrub oak mixed chaparral

209 Montane shrubland

211 Creosote bush scrub

212 Blackbush

215 Valley grassland
216 Montane meadows

412 Juniper-pinyon woodland

413 Gambel oak

414 Salt desert shrub

501 Saltbush-greasewood

502 Grama-galleta

503 Arizona chaparral

504 Juniper-pinyon pine woodland

505 Grama-tobosa shrub

506 Creosotebush-bursage

507 Palo verde-cactus

508 Creosotebush-tarbush

509 Transition between oak-juniper woodland and mahogany-oak association

604 Bluestem-grama prairie

701 Alkali sacaton-tobosagrass

702 Black grama-alkali sacaton

703 Black grama-sideoats grama

704 Blue grama-western wheatgrass

705 Blue grama-galleta

706 Blue grama-sideoats grama

707 Blue grama-sideoats grama-black grama

708 Bluestem-dropseed

709 Bluestem-grama

713 Grama-muhly-threeawn

715 Grama-buffalo grass

718 Mesquite-grama

724 Sideoats grama-New Mexico feathergrass-winterfat

727 Mesquite-buffalo grass

728 Mesquite-granjeno-acacia

729 Mesquite

732 Cross timbers-Texas (little bluestem-post oak)

733 Juniper-oak
735 Sideoats grama-sumac-juniper
  • 68. Shiflet, Thomas N., ed. 1994. Rangeland cover types of the United States. Denver, CO: Society for Range Management. 152 p. [23362]

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Habitat: Cover Types

More info on this topic.

This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

More info for the term: cover

SAF COVER TYPES [20]:



63 Cottonwood

68 Mesquite

220 Rocky Mountain juniper

235 Cottonwood-willow

237 Interior ponderosa pine

239 Pinyon-juniper

241 Western live oak

242 Mesquite
  • 20. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905]

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Habitat: Plant Associations

More info on this topic.

This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the term: shrub

KUCHLER [46] PLANT ASSOCIATIONS:



K011 Western ponderosa forest

K016 Eastern ponderosa forest

K019 Arizona pine forest

K023 Juniper-pinyon woodland

K024 Juniper steppe woodland

K027 Mesquite bosques

K031 Oak-juniper woodland

K032 Transition between K031 and K037

K034 Montane chaparral

K039 Blackbrush

K040 Saltbush-greasewood

K041 Creosote bush

K042 Creosote bush-bur sage

K043 Paloverde-cactus shrub

K044 Creosote bush-tarbush

K048 California steppe
K053 Grama-galleta steppe

K054 Grama-tobosa prairie

K057 Galleta-threeawn shrubsteppe
K058 Grama-tobosa shrubsteppe

K059 Trans-Pecos shrub savanna

K060 Mesquite savanna

K061 Mesquite-acacia savanna

K062 Mesquite-live oak savanna

K065 Grama-buffalo grass
K084 Cross Timbers

K085 Mesquite-buffalo grass

K086 Juniper-oak savanna

K087 Mesquite-oak savanna
  • 46. 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]

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Habitat: Ecosystem

More info on this topic.

This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

ECOSYSTEMS [23]:

FRES21 Ponderosa pine

FRES30 Desert shrub

FRES32 Texas savanna

FRES33 Southwestern shrubsteppe

FRES34 Chaparral-mountain shrub

FRES35 Pinyon-juniper

FRES38 Plains grasslands

FRES39 Prairie

FRES40 Desert grasslands

FRES42 Annual grasslands
  • 23. 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]

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General Ecology

Fire Management Considerations

More info for the terms: fire management, nonnative species, shrub

Information pertaining to fire management of sixweeks grama is lacking, and research is needed on the fire ecology and management of sixweeks grama. Historically, fires occurred frequently in desert grassland communities, actively inhibiting the invasion of shrub species. Research suggests that the reintroduction of fire into these communities will facilitate the return of native grasslands by eliminating woody overstory species [10,62,64]. However, managers should be cautious using fire as a management tool in areas where red brome exist. Nonnative species such as red brome may exhibit population explosions after disturbances such as fire and severely reduce native plant coverage [19].
  • 10. Buegge, J. Jeremy. 2001. Flora of the Santa Teresa Mountains in Graham County, Arizona. Journal of the Arizona-Nevada Academy of Science. 33(2): 132-149. [45078]
  • 19. Esque, Todd C.; Schwalbe, Cecil R. 2002. Alien annual grasses and their relationships to fire and biotic change in Sonoran desertscrub. In: Tellman, Barbara, ed. Invasive exotic species in the Sonoran region. Arizona-Sonora Desert Museum Studies in Natural History. Tucson, AZ: The University of Arizona Press; The Arizona-Sonora Desert Museum: 165-194. [48660]
  • 64. Robinett, Dan. 1995. Prescribed burning on upper Sonoran rangelands. In: Roundy, Burce A.; McArthur, E. Durant; Haley, Jennifer A.; Mann, David K., compilers. Proceedings: wildland shrub and arid land restoration symposium; 1993 October 19-21; Las Vegas. Gen. Tech. Rep. INT-GRT-315. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station: 361-363. [27500]
  • 62. 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]

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Broad-scale Impacts of Plant Response to Fire

More info for the terms: density, shrubs

Information on sixweeks grama's response to fire is very limited. One study
assessed the effects of multiple disturbances on Chihuahuan Desert shrubs, perennial
grasses, and annual grasses in a a tobosa-buffalo grass community in the San
Simon Valley of southeastern Arizona. Twenty plots, measuring 33 feet by 33 feet
(10 ×10 m), were subjected to the
following experimental treatments: ungrazed
and unburned (–G –B), ungrazed and burned
(–G +B), grazed and unburned (+G
–B), and grazed and burned (+G +B). Ungrazed
plots had been fenced off from grazing since 1977. In June 1993, 1995,
and 2000, burn plots were ignited with a propane torch, burning all aboveground vegetation.
In late August or early September, 1993
to 2000, each plot was measured in 15 regularly spaced 0.25 m2
quadrats. Sixweeks grama only occurred in numbers substantial enough to be
counted in 1996. Sixweeks grama densities did not differ significantly among the
4 treatments. The following table shows the mean density (individuals per
0.25 m2) of sixweeks grama on each of the 4 treatment plots [73]:

-G -B -G +B +G  -B+G +B
0.731.970.650.68
  • 73. Valone, Thomas J. 2003. Examination of interaction effects of multiple disturbances on an arid plant community. The Southwestern Naturalist. 48(4): 481-490. [47270]

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Immediate Effect of Fire

Sixweeks grama is typically killed by fire. Plants may only be top-killed if fire occurs early in the growing season [80,81].
  • 80. Went, F. W. 1948. Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, California. Ecology. 29(3): 242-253. [12915]
  • 81. Went, F. W.; Westergaard, M. 1949. Ecology of desert plants. III. Development of plants in the Death Valley National Monument, California. Ecology. 30(1): 26-38. [11102]

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Post-fire Regeneration

More info for the terms: initial off-site colonizer, secondary colonizer

POSTFIRE REGENERATION STRATEGY [69]:
Initial off-site colonizer (off-site, initial community)
Secondary colonizer (on-site or off-site seed sources)
  • 69. Stickney, Peter F. 1989. FEIS postfire regeneration workshop--April 12: Seral origin of species comprising secondary plant succession in Northern Rocky Mountain forests. 10 p. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station, Fire Sciences Laboratory, Missoula, MT. [20090]

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Fire Ecology

More info for the terms: cacti, cactus, fire exclusion, fire frequency, frequency, fuel, severity, shrub, shrubs, tree

Fire adaptations: Fire does not seem to have a detrimental effect on the seeds of sixweeks grama [62]. Sixweeks grama probably recovers from fire by establishing from soil-stored seed and from off-site, wind-dispersed seed.

FIRE REGIMES: Sixweeks grama predominantly occurs in desert scrub/thorn scrub and desert grassland communities. Historic FIRE REGIMES for these communities widely differed, with desert scrub/thorn scrub communities rarely burning and grassland communities burning often [62].  European-American settlement and subsequent land use changes has altered FIRE REGIMES greatly [10,62,74].

Desert scrub and thorn scrub communities:

Historically, fire was not an important ecological process in desert scrub and thorn scrub communities where sixweeks grama occurs. The annual grasses either did not accumulate enough fine fuel on the ground to facilitate fire or thrived during summer monsoon rains. Dominant tree, shrub, and cactus species were widely spaced and open branched, so there were usually not enough fuels to carry fire. However, this has dramatically changed since the 1970s with the spread of several nonnative species including red brome (Bromus madritensis spp. rubens), cheatgrass (B. tectorum), mediterranean grasses (Schismus spp.), and buffel grass (Pennisetum ciliare). Nonnative grasses have increased the risk and severity of fires in these communities [1,74]. Late spring and summer fires (from mid-May to July), fueled primarily by red brome, have dramatically increased in recent years. When fires occur before late summer, when sixweeks grama typically germinates, they often kill dominant plants including the columnar cacti species saguaro, senita (Lophocereus schottii), and organpipe (Stenocereus thurberi), the trees species bursera (Bursera spp.) and desert ironwood (Olneya tesota), and the shrub species bursage (Ambrosia spp.), paloverde (Parkinsonia spp.), brittle bush (Encelia farinosa), and creosotebush [74].

Desert grassland communities:

Prior to land use changes, grassland communities where sixweeks grama occur burned frequently [52,85]. While there are relatively few fire frequency data available prior to the 1880s, it is estimated that fire occurred every 7 to 10 years [52]. Grassland fires played an important role in thwarting the invasion of woody vegetation [64].  However, grazing pressures and fire exclusion have promoted the conversion of desert grassland communities to shrub-dominated communities [62]. The establishment of shrubs in desert grasslands has decreased available fuels and subsequently, fire frequencies [10,62,74].

The following table provides fire return intervals for plant communities and ecosystems where sixweeks grama is important. For further information, see the FEIS review of the dominant species listed below.

Community or Ecosystem Dominant Species Fire Return Interval Range (years)
saltbush-greasewood Atriplex confertifolia-Sarcobatus vermiculatus 62]
desert grasslands Bouteloua eriopoda and/or Pleuraphis mutica <35 to <100 [52,62]
plains grasslands Bouteloua spp. 62,86]
blue grama-needle-and-thread grass-western wheatgrass B. gracilis-Hesperostipa comata-Pascopyrum smithii 62,65,86]
grama-galleta steppe B. g.-Pleuraphis jamesii <35 to <100
blue grama-tobosa prairie B. g.-P. mutica <35 to <100
California montane chaparral Ceanothus and/or Arctostaphylos spp. 50-100
blackbrush Coleogyne ramosissima <35 to <100 [62]
California steppe Festuca-Danthonia spp. <35 [62,70]
paloverde-cactus shrub Parkinsonia spp./Opuntia spp. <35 to <100
creosotebush Larrea tridentata <35 to <100
Ceniza shrub L. t.-Leucophyllum frutescens-Prosopis glandulosa <35
pinyon-juniper Pinus-Juniperus spp. <35 [62]
Colorado pinyon P. edulis 10-400+ [22,27,43,62]
interior ponderosa pine* P. ponderosa var. scopulorum 2-30 [2,3,47]
Arizona pine P. ponderosa var. arizonica 2-15 [3,13,67]
galleta-threeawn shrubsteppe Pleuraphis jamesii-Aristida purpurea <35 to <100 [62]
mesquite Prosopis glandulosa <35 to <100 [52,62]
mesquite-buffalo grass P. g.-Buchloe dactyloides <35
Texas savanna P. g. var. glandulosa <10
oak-juniper woodland (Southwest) Quercus-Juniperus spp. <35 to <200 [62]
*fire return interval varies widely; trends in variation are noted in the species review
  • 22. 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]
  • 47. 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]
  • 52. McPherson, Guy R. 1995. The role of fire in the desert grasslands. In: McClaran, Mitchel P.; Van Devender, Thomas R., eds. The desert grassland. Tucson, AZ: The University of Arizona Press: 130-151. [26576]
  • 86. Wright, Henry A.; Bailey, Arthur W. 1982. Fire ecology: United States and southern Canada. New York: John Wiley & Sons. 501 p. [2620]
  • 13. Cooper, Charles F. 1961. Pattern in ponderosa pine forests. Ecology. 42(3): 493-499. [5780]
  • 2. Arno, Stephen F. 1976. The historical role of fire on the Bitterroot National Forest. Res. Pap. INT-187. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 29 p. [15225]
  • 3. 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]
  • 10. Buegge, J. Jeremy. 2001. Flora of the Santa Teresa Mountains in Graham County, Arizona. Journal of the Arizona-Nevada Academy of Science. 33(2): 132-149. [45078]
  • 64. Robinett, Dan. 1995. Prescribed burning on upper Sonoran rangelands. In: Roundy, Burce A.; McArthur, E. Durant; Haley, Jennifer A.; Mann, David K., compilers. Proceedings: wildland shrub and arid land restoration symposium; 1993 October 19-21; Las Vegas. Gen. Tech. Rep. INT-GRT-315. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station: 361-363. [27500]
  • 65. Rowe, J. S. 1969. Lightning fires in Saskatchewan grassland. Canadian Field-Naturalist. 83: 317-324. [6266]
  • 70. Stomberg, Mark R.; Kephart, Paul; Yadon, Vern. 2001. Composition, invasibility, and diversity in coastal California grasslands. Madrono. 48(4): 236-252. [41371]
  • 74. Van Devender, Thomas R.; Felger, Richard S.; Burquez M., Alberto. 1997. Exotic plants in the Sonoran Desert region, Arizona and Sonora. In: Kelly, M.; Wagner, E.; Warner, P., eds. Proceedings, California Exotic Pest Plant Council symposium; 1997 October 2-4; Concord, CA. Volume 3. Berkeley, CA: California Exotic Pest Plant Council: 10-15. [44103]
  • 85. Wright, Henry A. 1980. The role and use of fire in the semidesert grass-shrub type. Gen. Tech. Rep. INT-85. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 24 p. [2616]
  • 43. Keeley, Jon E. 1981. Reproductive cycles and FIRE REGIMES. In: Mooney, H. A.; Bonnicksen, T. M.; Christensen, N. L.; Lotan, J. E.; Reiners, W. A., 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]
  • 62. 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]
  • 1. Alford, Eddie J.; Brock, John H. 2002. The effects of fire on Sonoran Desert plant communities. Final Report: RMRS-99164-RJVA. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 111 p. [Alford's Dissertation]. On file with: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. [47514]
  • 27. 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]
  • 67. Seklecki, Mariette T.; Grissino-Mayer, Henri D.; Swetnam, Thomas W. 1996. Fire history and the possible role of Apache-set fires in the Chiricahua Mountains of southeastern Arizona. In: Ffolliott, Peter F.; DeBano, Leonard F.; Baker, Malchus, B., Jr.; [and others], tech. coords. Effects of fire on Madrean Province ecosystems: a symposium proceedings; 1996 March 11-15; Tucson, AZ. Gen. Tech. Rep. RM-GTR-289. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 238-246. [28082]

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Regeneration Processes

More info for the terms: cactus, root crown, shrub, tree

Sixweeks grama regenerates by seed [36].

Breeding system: No information is available on this topic.

Pollination: Sixweeks grama is probably wind pollinated.

Seed production: In Joshua Tree National Monument, California, sixweeks grama produced seeds within 4 weeks of germination at elevations below 1,000 feet (300 m) and within 6 weeks above 1,000 feet (300 m) elevation [80]. In the Chihuahuan Desert of southeastern Arizona, seed production was observed 6 to 8 weeks after germination at an elevation of 5,000 feet (1,500 m) [73].

Seed dispersal: Given sixweeks grama's small seed weight (0.03 mg), dispersal by wind is likely. Seeds are also dispersed by birds, small mammals, and ungulates when awns attach to fur and feathers [49]. A controlled study of the chisel-toothed kangaroo rat on plots of Chihuahuan Desert shrub habitat in southeastern Arizona found that sixweeks grama was significantly (p<0.05) less abundant in areas where the chisel-toothed kangaroo rat had been removed. This was attributed to both seed dispersal mechanisms and soil disturbance [9]. A study of cactus wren in Arizona found transported seeds of sixweeks grama surrounding the wrens' nests [54].

Seed banking: Little information pertaining to sixweeks grama seed banking exists. A study was conducted north of Las Cruces, New Mexico, to determine plant emergence from soils collected on 3 desert grassland sites representing 3 rangeland conditions (poor, fair, and good). The researchers noted that needle grama and sixweeks grama could not be differentiated in the seedling stage. On good-condition range sites dominated by black grama, 26.1 sixweeks grama/needle grama seedlings emerged per m2. Sixweeks grama comprised 17.5% of total plant species composition based on coverage of the poor-condition range. On fair-condition range dominated by mesa dropseed (Sporobolus flexuosus), 11.0 grama seedlings emerged per m2 (6.8% of total plant species composition). On poor-condition range dominated by fluffgrass (Erioneuron pulchellum), 10.2 grama seedlings emerged per m2 (6.4% of total plant species composition) [54]. A study conducted by Went and others [38] (see Germination below) seems to indicate that a large bank of sixweeks grama seeds are held in the soil.

Seed dormancy: To date (2005), the literature does not describe how long seeds remain viable in the soil. However, several studies have found that sixweeks grama does not germinate when precipitation is inadequate [6,12,17,25,26,31,37,38], so it seems likely that soil-stored seeds remain viable for several years.

Germination: Sixweeks grama germination is dependent upon warm soil temperatures and heavy summer precipitation associated with thundershowers and monsoon rains in desert ecosystems [12,37,37,61]. Studies conducted in Joshua Tree National Monument [80]  and the Chihuahuan Desert of New Mexico [44] found that a single rainfall of 0.6 to 1 inch (15-25 mm) was required for germination to begin. In gullies or collection areas, germination has occurred with as little as 0.4 inch (10 mm) of rain [80]. In laboratory experiments conducted by Went [80], sixweeks grama showed good germination under a temperature regime of warm days (8 hours at 80 °F (27 °C)) and warm nights (16 hours at 78 °F (26 °C)), but poor germination under a temperature regime of warm days and cool nights (16 hours at 55 °F (13 °C)). In another experiment by Went and others [38], between 50 and 100 cm³ of soil was collected from Joshua Tree National Monument and subjected to 3 different temperature regimes. Eighty sixweeks grama and needle grama seeds germinated with warm daytime soil temperatures of 86 °F (30 °C); 29 grama seeds germinated in moderate daytime soil temperatures ranging from 62 °F (17 °C) to 73 °F (23 °C); and no seeds germinated with cool daytime soil temperatures of 50 °F (10 °C) [38].

Seedling establishment/growth: Upon seedling establishment, sixweeks grama's life cycle can be "measured in terms of weeks rather than months" [4]. Growth occurs rapidly, with the plant reaching its maximum size and setting seed within 4 to 6 weeks following germination [44,61,80].

In Joshua Tree National Monument, sixweeks grama was observed producing new growth from its root crown toward the end of its life cycle. The new growth occurred following "substantial" rainfall when daytime temperatures were between 90 ºF and 105 ºF (32-41 ºC ). Sixweeks grama does not sprout from the root crown following autumn rains due to cool temperatures [84].

  • 4. Barbour, Michael G.; Burk, Jack H.; Pitts, Wanna D. 1980. Major vegetation types of North America. In: Barbour, Michael G.; Burk, Jack H.; Pitts, Wanna D. Terrestrial plant ecology. Menlo Park, CA: The Benjamin/Cummings Publishing Company, Inc: 486-583. [45729]
  • 6. Booth, W. E. 1950. Flora of Montana. Part I: Conifers and monocots. Bozeman, MT: The Research Foundation at Montana State College. 232 p. [48662]
  • 9. Brown, James H.; Heske, Edward J. 1990. Control of a desert-grassland transition by a keystone rodent guild. Science. 250(4988): 1705-1707. [54673]
  • 12. Carmichael, R. S.; Knipe, O. D.; Pase, C. P.; Brady, W. W. 1978. Arizona chaparral: plant associations and ecology. Res. Pap. RM-202. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 16 p. [3038]
  • 17. Dorn, Robert D. 1984. Vascular plants of Montana. Cheyenne, WY: Mountain West Publishing. 276 p. [819]
  • 25. Gibbens, Robert P.; Beck, Reldon F. 1988. Changes in grass basal area and forb densities over a 64-year period on grassland types of the Jornada Experimental Range. Journal of Range Management. 41(3): 186-192. [5227]
  • 26. Goodrich, Sherel. 1986. Vascular plants of the Desert Experimental Range, Millard County, Utah. Gen. Tech. Rep. INT-209. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 72 p. [1033]
  • 31. Herbel, Carlton H.; Nelson, Arnold B. 1966. Species preference of Hereford and Santa Gertrudis cattle on a southern New Mexico range. Journal of Range Management. 19: 177-181. [5313]
  • 36. Jackson, Laura L.; McAuliffe, Joseph R.; Roundy, Bruce A. 1991. Desert restoration. Restoration & Management Notes. 9(2): 71-79. [22746]
  • 37. Johnson, Hyrum B. 1976. Vegetation and plant communities of southern California deserts--a functional view. In: Latting, June, ed. Symposium proceedings: plant communities of southern California; 1974 May 4; Fullerton, CA. Special Publication No. 2. Berkeley, CA: California Native Plant Society: 125-164. [1278]
  • 38. Juhren, Marcella; Went, F. W.; Phillips, Edwin. 1956. Ecology of desert plants. IV. Combined field and laboratory work on germination of annuals in the Joshua Tree National Monument, California. Ecology. 37(2): 318-330. [12975]
  • 44. Kemp, Paul R. 1983. Phenological patterns of Chihuahuan Desert plants in relation to the timing of water availability. Journal of Ecology. 71: 427-436. [5054]
  • 49. Martin, Alexander C.; Zim, Herbert S.; Nelson, Arnold L. 1951. American wildlife and plants. New York: McGraw-Hill Book Company, Inc. 500 p. [4021]
  • 73. Valone, Thomas J. 2003. Examination of interaction effects of multiple disturbances on an arid plant community. The Southwestern Naturalist. 48(4): 481-490. [47270]
  • 80. Went, F. W. 1948. Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, California. Ecology. 29(3): 242-253. [12915]
  • 84. Wolden, Lynn; Stromberg, Julie; Patten, Duncan; Richter, Holly. 1990. Understory restoration in three riparian forest types. Restoration & Management Notes. 8(2): 116-117. [13790]
  • 54. Milton, Suzanne J.; Dean, W. R. J.; Kerley, G. I. H.; [and others]. 1998. Dispersal of seeds as nest material by the cactus wren. The Southwestern Naturalist. 43(4): 449-452. [29454]
  • 61. Nichol, A. A. [revisions by Phillips, W. S.]. 1952. The natural vegetation of Arizona. Tech. Bull. 68 [Revised]. Tucson, AZ: University of Arizona, Agricultural Experiment Station: 189-230. [3928]

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Growth Form (according to Raunkiær Life-form classification)

More info on this topic.

More info for the term: therophyte

RAUNKIAER [63] LIFE FORM:
Therophyte
  • 63. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford: Clarendon Press. 632 p. [2843]

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Life Form

More info for the term: graminoid

Graminoid

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Plant Response to Fire

As a short-lived annual, sixweeks grama plants have little chance to sprout unless fire occurs early in its development.

Sixweeks grama seeds survive burning, and surviving seeds germinate when favorable conditions occur (hot temperatures and sufficient rainfall) [80,81].

  • 80. Went, F. W. 1948. Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, California. Ecology. 29(3): 242-253. [12915]
  • 81. Went, F. W.; Westergaard, M. 1949. Ecology of desert plants. III. Development of plants in the Death Valley National Monument, California. Ecology. 30(1): 26-38. [11102]

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Successional Status

More info on this topic.

Sixweeks grama is an early seral species. It often occurs on disturbed sites with bare ground and sparse vegetation [7,14,17,26,28,32]. Sixweeks grama is considered an invader under heavy grazing [76].
  • 7. Bowers, Janice E.; McLaughlin, Steven P. 1987. Flora and vegetation of the Rincon Mountains, Pima County, Arizona. Desert Plants. 8(2): 50-94. [495]
  • 17. Dorn, Robert D. 1984. Vascular plants of Montana. Cheyenne, WY: Mountain West Publishing. 276 p. [819]
  • 26. Goodrich, Sherel. 1986. Vascular plants of the Desert Experimental Range, Millard County, Utah. Gen. Tech. Rep. INT-209. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 72 p. [1033]
  • 28. Gould, Frank W. 1979. The genus Bouteloua (Poaceae). Annals of the Missouri Botanical Garden. 66: 348-416. [5758]
  • 32. Hickman, James C., ed. 1993. The Jepson manual: Higher plants of California. Berkeley, CA: University of California Press. 1400 p. [21992]
  • 76. Van Dyne, George M. 1958. Ranges and range plants. Unpublished manuscript on file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. 290 p. [7310]
  • 14. 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]

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Life History and Behavior

Cyclicity

Phenology

More info on this topic.

More info for the terms: phenology, tree

Following sufficient summer rains, sixweeks grama begins its rapid growth. Sixweeks grama reaches maturity, sets seed, and dies within 6 to 8 weeks of germination [4,44,80].

In Joshua Tree National Monument, sixweeks grama was observed producing new growth from root crowns toward the end of its life cycle (see Seedling establishment/growth) [84]. The period of flowering for sixweeks grama is presented in the table below:

Location Beginning of Flowering End of Flowering
Arizona July September [61,73]
California June October [4,58]
Colorado July October [30,37,58]
Kansas/Oklahoma August October [29]
New Mexico July October [11,50]
Nevada July August [41,83]
Texas July October [15,83]
Utah July September [26]
Baja California July October [83]

The phenology of sixweeks grama in the northern Chihuahuan Desert of southern New Mexico is presented in the table below [44]:

Phenological event Period of event
Seeds germinate Late August to early September
Flowering September
Seeds mature Late September to early October
Seeds dispersed/plant death Late October
  • 30. Harrington, H. D. 1964. Manual of the plants of Colorado. 2d ed. Chicago: The Swallow Press, Inc. 666 p. [6851]
  • 4. Barbour, Michael G.; Burk, Jack H.; Pitts, Wanna D. 1980. Major vegetation types of North America. In: Barbour, Michael G.; Burk, Jack H.; Pitts, Wanna D. Terrestrial plant ecology. Menlo Park, CA: The Benjamin/Cummings Publishing Company, Inc: 486-583. [45729]
  • 11. Campbell, R. S.; Bomberger, E. H. 1934. The occurrence of Gutierrezia sarothrae on Bouteloua eriopoda ranges in southern New Mexico. Ecology. 15(1): 49-61. [596]
  • 15. Denyes, H. Arliss. 1956. Natural terrestrial communities of Brewster County, Texas. The American Midland Naturalist. 55(2): 289-320. [26765]
  • 26. Goodrich, Sherel. 1986. Vascular plants of the Desert Experimental Range, Millard County, Utah. Gen. Tech. Rep. INT-209. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 72 p. [1033]
  • 29. Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: University Press of Kansas. 1392 p. [1603]
  • 37. Johnson, Hyrum B. 1976. Vegetation and plant communities of southern California deserts--a functional view. In: Latting, June, ed. Symposium proceedings: plant communities of southern California; 1974 May 4; Fullerton, CA. Special Publication No. 2. Berkeley, CA: California Native Plant Society: 125-164. [1278]
  • 44. Kemp, Paul R. 1983. Phenological patterns of Chihuahuan Desert plants in relation to the timing of water availability. Journal of Ecology. 71: 427-436. [5054]
  • 50. Martin, William C.; Hutchins, Charles R. 1981. A flora of New Mexico. Volume 2. Germany: J. Cramer. 2589 p. [37175]
  • 58. Munz, Philip A. 1974. A flora of southern California. Berkeley, CA: University of California Press. 1086 p. [4924]
  • 73. Valone, Thomas J. 2003. Examination of interaction effects of multiple disturbances on an arid plant community. The Southwestern Naturalist. 48(4): 481-490. [47270]
  • 80. Went, F. W. 1948. Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, California. Ecology. 29(3): 242-253. [12915]
  • 83. Wiggins, Ira L. 1980. Flora of Baja California. Stanford, CA: Stanford University Press. 1025 p. [21993]
  • 84. Wolden, Lynn; Stromberg, Julie; Patten, Duncan; Richter, Holly. 1990. Understory restoration in three riparian forest types. Restoration & Management Notes. 8(2): 116-117. [13790]
  • 41. Kartesz, John Thomas. 1988. A flora of Nevada. Reno, NV: University of Nevada. 1729 p. [In 3 volumes]. Dissertation. [42426]
  • 61. Nichol, A. A. [revisions by Phillips, W. S.]. 1952. The natural vegetation of Arizona. Tech. Bull. 68 [Revised]. Tucson, AZ: University of Arizona, Agricultural Experiment Station: 189-230. [3928]

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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: NNR - Unranked

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© NatureServe

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

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Management

Management considerations

More info for the term: resistance

Sixweeks grama has high resistance to grazing [76].
As an ephemeral, sixweeks grama is only valuable to livestock for a short period
of time. Rangelands containing an abundance of sixweeks grama may be stocked heavily for grazing for 1 to 2 months,
while plants are green [24,34,35].
  • 24. Gay, Charles W., Jr.; Dwyer, Don D. 1965. New Mexico range plants. Circular 374. Las Cruces, NM: New Mexico State University, Cooperative Extension Service. 85 p. [4039]
  • 76. Van Dyne, George M. 1958. Ranges and range plants. Unpublished manuscript on file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. 290 p. [7310]
  • 34. Humphrey, Robert R. 1960. Arizona range grasses: Description--forage value--management. Bulletin 298. Tucson, AZ: University of Arizona, Agricultural Experiment Station. 104 p. [5004]
  • 35. Humphrey, Robert R.; Brown, Albert L.; Everson, A. C. 1952. Common Arizona range grasses: Their description, forage value and management. Bulletin 243. Tucson, AZ: University of Arizona, Agricultural Experiment Station. 102 p. [4442]

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Relevance to Humans and Ecosystems

Benefits

Importance to Livestock and Wildlife

More info for the terms: cactus, cover

Livestock: Sixweeks grama provides poor forage for livestock. The plants are small, produce green feed for a short period of time, and have a weak root system that allows them to be pulled up easily during grazing. Sixweeks grama is almost worthless as forage after maturity [24,34,41,76]. A 4-year study was conducted from 1961 to 1964 to determine the forage preferences of Hereford and Santa Gertrudis cattle in the Jornada Experimental Range, New Mexico. Basal cover of sixweeks grama at the study site ranged from a trace to 1.7%. Sixweeks grama basal cover declined in 1963 and 1964 due to drought conditions. Sixweeks grama primarily occurred in 1962, with very small amounts in 1961 and 1964. Favorable moisture conditions in 1961 and 1962 led to a substantial growth of sixweeks grama, which was grazed heavily even after its maturity, particularly when softened by morning dew. Both Hereford and Santa Gertrudis cattle were observed actively grazing sixweeks grama when it was "dormant" in the winter of 1964, due in large part to a shortage of more palatable species. The table below describes the percent usage of sixweeks grama by Hereford (H) and Santa Gertrudis (SG) cattle from 1961 to 1964 [31]:

Fall Winter Spring Summer
H SG H SG H SG H SG
1.7 3.3 7.1 1.9 -- -- -- 9.4

Wildlife: A variety of upland game birds (e.g. wild turkey), songbirds (e.g. brown-capped rosy-finch, chestnut-collared longspur, McCown's longspur, and Brewer's sparrow), and small mammals (e.g. prairie pocket mouse, black-tailed and Gunnison prairie dogs, desert kangaroo and banner-tailed rats) eat the seeds and seedheads of grama grasses (Bouteloua spp.) [49]. Harvester ants in Sonoran Desert lowlands of Arizona also eat sixweeks grama seeds [36]. The seeds of sixweeks grama have been found in the surrounds of cactus wren nests [54]. Caches of sixweeks grama seeds have been identified in the dens of the banner-tailed kangaroo rat, Merriam's kangaroo rat, and white-throated woodrat [56]. Jackrabbits (antelope and white-sided), prairie pocket mice, prairie dogs (black-tailed and Gunnison), and ungulates (pronghorn, American bison, mule and white-tailed deer, elk, and bighorn sheep) eat grama grasses [49].

Palatability/nutritional value: When young, sixweeks grama is palatable to livestock and is actively grazed [41,66]. Sixweeks grama is moderately nutritious when green [31,34,35]. But, since the green period is short, little forage is produced and nutritional value rapidly decreases upon maturity rendering the plant "practically worthless" [24]. A 1962 winter nutritional analysis of sixweeks grama (% of dry weight) taken in the Jornada Experimental Range, New Mexico, is presented below [59]:

Date Protein
(%)
Ether extract
(%)
Acid-detergent fiber
(%)
Ash
(%)
Ca
(%)
P
(%)
February (overripe) 4.1 1.4 51.3 6.2 0.30 0.05
March (dormant) 5.0 1.5 53.2 1.7 0.63 0.05

Cover value: Given its small mass, sixweeks grama likely provides cover for only small animals.

  • 24. Gay, Charles W., Jr.; Dwyer, Don D. 1965. New Mexico range plants. Circular 374. Las Cruces, NM: New Mexico State University, Cooperative Extension Service. 85 p. [4039]
  • 31. Herbel, Carlton H.; Nelson, Arnold B. 1966. Species preference of Hereford and Santa Gertrudis cattle on a southern New Mexico range. Journal of Range Management. 19: 177-181. [5313]
  • 36. Jackson, Laura L.; McAuliffe, Joseph R.; Roundy, Bruce A. 1991. Desert restoration. Restoration & Management Notes. 9(2): 71-79. [22746]
  • 49. Martin, Alexander C.; Zim, Herbert S.; Nelson, Arnold L. 1951. American wildlife and plants. New York: McGraw-Hill Book Company, Inc. 500 p. [4021]
  • 59. Nelson, A. B.; Herbel, H. M.; Jackson, H. M. 1970. Chemical composition of forage species grazed by cattle on an arid New Mexico range. Bulletin 561. Las Cruces, NM: New Mexico State University, Agricultural Experiment Station. 33 p. [4034]
  • 76. Van Dyne, George M. 1958. Ranges and range plants. Unpublished manuscript on file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. 290 p. [7310]
  • 34. Humphrey, Robert R. 1960. Arizona range grasses: Description--forage value--management. Bulletin 298. Tucson, AZ: University of Arizona, Agricultural Experiment Station. 104 p. [5004]
  • 35. Humphrey, Robert R.; Brown, Albert L.; Everson, A. C. 1952. Common Arizona range grasses: Their description, forage value and management. Bulletin 243. Tucson, AZ: University of Arizona, Agricultural Experiment Station. 102 p. [4442]
  • 56. Monson, Gale; Kessler, Wayne. 1940. Life history notes on the banner-tailed kangaroo rat, Merriam's kangaroo rat, and white-throated wood rat in Arizona and New Mexico. Journal of Wildlife Management. 4(1): 37-43. [12166]
  • 66. Sampson, Arthur W.; Chase, Agnes; Hedrick, Donald W. 1951. California grasslands and range forage grasses. Bull. 724. Berkeley, CA: University of California College of Agriculture, California Agricultural Experiment Station. 125 p. [2052]
  • 41. Kartesz, John Thomas. 1988. A flora of Nevada. Reno, NV: University of Nevada. 1729 p. [In 3 volumes]. Dissertation. [42426]
  • 54. Milton, Suzanne J.; Dean, W. R. J.; Kerley, G. I. H.; [and others]. 1998. Dispersal of seeds as nest material by the cactus wren. The Southwestern Naturalist. 43(4): 449-452. [29454]

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Value for rehabilitation of disturbed sites

Research in the Jornada Experimental Range, New Mexico, has shown that sixweeks grama gives protection against wind erosion until perennials take hold [60]. Other information pertaining to sixweeks grama's value for rehabilitating disturbed sites is lacking.
  • 60. Nelson, Enoch W. 1934. The influence of precipitation and grazing upon black grama grass range. Technical Bulletin No. 409. Washington, DC: U.S. Department of Agriculture. 32 p. [4175]

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Wikipedia

Bouteloua barbata

Bouteloua barbata is a species of grass known by the common name six-weeks grama. It is native to North America, where it occurs in the southwestern United States and south to Oaxaca in southern Mexico. It may occur in Montana.[1][2] It is also present in Argentina.[1]

This species is an annual or perennial grass producing tufts of stems up to 30 to 75 cm (12 to 30 in) long,[1][2] lying prostrate, spreading, or standing erect. The inflorescence has up to 11 branches,[2] each a dense row of up to 40 spikelets. The fruit weighs about 0.03 milligrams. This lightweight seed is dispersed on the wind and by animals. It is annual or perennial, sprouting from seed or from its root crown after summer rainfall. Flowering usually begins around July and lasts until October.[1] There are three varieties of this species. The var. barbata is an annual plant with decumbent stems that may root at stem nodes, var. rothrockii, sometimes considered a separate species, is perennial with erect stems, and var. sonorae, which is limited to northern Mexico, spreads via stolons.[2]

This grass grows in many types of habitat including prairie, grasslands, pinyon-juniper woodland, chaparral, creosote, shrubsteppe, savanna, and Ponderosa pine forest. It is a resident of dry regions. It grows in the deserts of the American southwest and Mexico, including the Colorado, Mojave, and Chihuahuan Deserts. It can also be found in dry disturbed habitat such as roadsides, railroads, and overgrazed pastures.[1]

While it is palatable, this grass is not considered a good forage for livestock, as it is a small plant and is green for a short time. Many types of other animals utilize it, however. Many birds, and small animals including prairie dogs and desert kangaroo rats eat the seeds of this and other grama grasses. Harvester ants in Arizona also eat the seeds of this species.[1]

References[edit]

  1. ^ a b c d e f Hauser, A. Scott (2005) Bouteloua barbata. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved 12-12-2011.
  2. ^ a b c d Bouteloua barbata. Grass Manual Treatment. Retrieved 12-12-2011.
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Names and Taxonomy

Taxonomy

The scientific name of sixweeks grama is Bouteloua barbata Lag. (Poaceae) [16,32,40,48,80]. A single variety is recognized by some authorities
[32,80]:

Bouteloua barbata var. barbata Cienc.
Sonoran grama, formerly recognized as Bouteloua barbata var. sonorae (Griffiths) Gould, and Rothrock's
grama, formerly recognized as Bouteloua barbata  var. rothrockii (Vasey) Gould, are
currently recognized as the distinct species Bouteloua sonorae Griffiths
and Bouteloua rothrockii Vasey, respectively [40].
  • 16. Diggs, George M., Jr.; Lipscomb, Barney L.; O'Kennon, Robert J. 1999. Illustrated flora of north-central Texas. Sida Botanical Miscellany No. 16. Fort Worth, TX: Botanical Research Institute of Texas. 1626 p. [35698]
  • 32. Hickman, James C., ed. 1993. The Jepson manual: Higher plants of California. Berkeley, CA: University of California Press. 1400 p. [21992]
  • 80. Went, F. W. 1948. Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, California. Ecology. 29(3): 242-253. [12915]
  • 40. Kartesz, John T.; Meacham, Christopher A. 1999. Synthesis of the North American flora (Windows Version 1.0), [CD-ROM]. Available: North Carolina Botanical Garden. In cooperation with the Nature Conservancy, Natural Resources Conservation Service, and U.S. Fish and Wildlife Service [2001, January 16]. [36715]
  • 48. Mares, M. A.; Enders, F. A.; Kingsolver, J. M.; [and others]. 1977. Prosopis as a niche component. In: Simpson, B. B., ed. Mesquite: Its biology in two desert ecosystems. US/IBP Synthesis Series 4. Stroudsburg, PA: Dowden, Hutchinson & Ross, Inc: 123-149. [5194]

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Common Names

sixweeks grama

six-weeks grama
six weeks grama

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