SPECIES: Pascopyrum smithii

INTRODUCTORY

SPECIES: Pascopyrum smithii
AUTHORSHIP AND CITATION:
Tirmenstein, D. 1999. Pascopyrum smithii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

ABBREVIATION:
PASSMI

SYNONYMS:
Agropyron smithii Rydb. [61,66,97]

NRCS PLANT CODE:
PASM

COMMON NAMES:
western wheatgrass

TAXONOMY:
The fully documented scientific name of western wheatgrass is Pascopyrum smithii P.A. Love (Poaceae) [12,86]. There has been much confusion concerning the taxonomy of western wheatgrass [12,13,14,41,42,43,64,77,78]. It is believed to be the product of an allo-octoploid (2n=56) derived from hybridization of 2 tetraploid grasses (2n=28); thickspike wheatgrass (Elymus lanceolatus) and beardless wheatgrass (Pseudoroegneria spicata ssp. inerme) [111]. Barkworth and Dewey [12] recognize the monotypic genus Pascopyrum A. Love.

Ecotypes of western wheatgrass vary in forage and seed production characteristics and in color, coarseness, and competitiveness [68].

LIFE FORM:
graminoid

FEDERAL LEGAL STATUS:
No special status

OTHER STATUS:
no entry


DISTRIBUTION AND OCCURRENCE

SPECIES: Pascopyrum smithii
GENERAL DISTRIBUTION:
Western wheatgrass grows east of the Cascade Range from British Columbia south to eastern Washington and Oregon, Nevada, and Arizona, eastward to Ontario, New York, Tennessee, and Texas [20,21,33,56,77,78].

ECOSYSTEMS:
FRES15 Oak-hickory
FRES17 Elm-ash-cottonwood
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES23 Fir-spruce
FRES26 Lodgepole pine
FRES29 Sagebrush
FRES30 Desert shrub
FRES34 Chaparral-mountain shrub
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES38 Plains grasslands
FRES39 Prairie

STATES:
AK  AZ  CA  CO  CT  HI  IL  IN  IA  KS
MA  MI  MN  MO  MT  NE  NV  NH  NM  NY
ND  OH  OK  OR  PA  SD  TN  TX  UT  VT
WA  WI  WY  AB  BC  MB  ON  PQ  SK


BLM PHYSIOGRAPHIC REGIONS:
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountains Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands

KUCHLER PLANT ASSOCIATIONS:
K011 Western ponderosa forest
K012 Douglas-fir forest
K015 Western spruce-fir forest
K016 Eastern ponderosa forest
K017 Black Hills pine forest
K018 Pine-Douglas-fir forest
K021 Southwestern spruce-fir forest
K023 Juniper-pinyon woodland
K037 Mountain-mahogany-oak scrub
K038 Great Basin sagebrush
K040 Saltbush-greasewood
K051 Wheatgrass-bluegrass
K053 Grama-galleta steppe
K055 Sagebrush steppe
K056 Wheatgrass-needlegrass shrubsteppe
K063 Foothills prairie
K064 Grama-needlegrass-wheatgrass
K065 Grama-buffalograss
K066 Wheatgrass-needlegrass
K067 Wheatgrass-bluestem-needlegrass
K074 Bluestem prairie
K081 Oak savanna
K098 Northern floodplain forest

SAF COVER TYPES:
219 Limber pine
220 Rocky Mountain juniper
237 Interior ponderosa pine
238 Western juniper
239 Juniper-pinyon
256 California mixed subalpine

SRM (RANGELAND) COVER TYPES:
303 Bunchgrass wheatgrass-western wheatgrass
309 Idaho fescue-western wheatgrass
310 Needle-and-thread-blue grama
314 Big sagebrush-bluebunch wheatgrass
401 Basin sagebrush
402 Mountain big sagebrush
403 Wyoming big sagebrush
412 Juniper-pinyon woodland
504 Juniper-pinyon woodlands
601 Bluestem prairie
602 Bluestem-prairie sandreed
604 Bluestem-grama prairie
606 Wheatgrass-bluestem-needlegrass
607 Wheatgrass-needlegrass
608 Wheatgrass-grama-needlegrass
609 Wheatgrass grama
610 Wheatgrass
611 Blue grama-buffalograss
612 Sagebrush-grass
613 Fescue grassland
615 Wheatgrass-saltgrass-grama
704 Blue grama-western wheatgrass
705 Blue grama-galleta
710 Bluestem prairie
711 Bluestem-sachuista prairie
712 Galleta-alkali sacaton
715 Grama-buffalograss
722 Sand sagebrush-mixed prairie
725 Vine mesquite-alkali sacaton
727 Mesquite-buffalograss

HABITAT TYPES AND PLANT COMMUNITIES:
Western wheatgrass grows in grasslands and sagebrush (Artemisia spp.) deserts; it commonly grows in pure stands, but more often grows mixed with other grasses [78,119,130,145,150]. It is often the dominant grass in mixed-grass prairie communities [10].

Western wheatgrass is a codominant or indicator in many habitat types in sagebrush-grassland, pinyon-juniper (Pinus ssp.)-(Juniperus ssp.), and Rocky mountain juniper (J. scopulorum) types [81,102]. It is of major importance in the central and northern Great Plains grassland where it is commonly associated with blue grama (Bouteloua gracilis), sideoats grama (B. curtipendula), alkali sacaton (Sporobolus airoides), buffalo grass (Buchloe dactyloides), prairie junegrass (Koeleria macrantha), needle and thread grass (Hesperostipa comata), green needlegrass (Nassella viridula), and little bluestem (Schizachyrium scoparium) [11].

Western wheatgrass occurs with a number of shrubs including big sagebrush (A. tridentata), bitterbrush (Purshia tridentata), and broom snakeweed (Gutierrezia sarothrae) [1].

On the sagebrush rangeland of the Intermountain area, western wheatgrass is often mixed with bluebunch wheatgrass (Pseudoroegneria spicata) and thickspike wheatgrass [25]. In northern mixed-grass prairies, western wheatgrass occurs as a dominant with needle-and-thread grass, blue grama, and bluestems [49,52]. Publications using western wheatgrass in vegetation classifications are listed below:

Vegetation and soils of the Crane Springs Watershed [20]
Vegetation and soils of the Rock Springs Watershed [21]
Phyto-edaphic communities of the Upper Rio Puerco Watershed, New Mexico [55]
The vegetation of the Grand River/Cedar River, Sioux, and Ashland Districts of the Custer National Forest: a habitat type classification [71]
Preliminary habitat types of a semiarid grassland [56]
The vegetation of Theodore Roosevelt National Park, North Dakota: a habitat type classification [72]
Classification and management of riparian and wetland sites in central and eastern Montana [73]
Range plant communities of the Central Grasslands Research Station in south central North Dakota [101]
Grassland and shrubland habitat types of western Montana [110]
Shrub-steppe habitat types of Middle Park, Colorado [140]
Grassland and shrubland habitat types of the Shoshone National Forest [144]
Analysis of grassland vegetation on selected key areas in southwestern North Dakota [166]
Grassland types of south central Montana [171]

MANAGEMENT CONSIDERATIONS

SPECIES: Pascopyrum smithii
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
Western wheatgrass is an important forage species on ranges in good condition in pinyon-juniper, chaparral, northern desert shrub, and shortgrass prairie [48]. It is one of the most valuable North American wheatgrasses [88]. Although leaves are stiff, they rarely become sufficiently coarse to discourage animal use [36,84,121].

Western wheatgrass is one of the primary grasses eaten by cattle in New Mexico and in central and eastern Montana [4,95]. It provides important domestic sheep forage in southeastern Montana, particularly during June, July, and August [2]. Fall regrowth cures well on the stem, so western wheatgrass is considered good winter forage for domestic livestock [68].

Bison feed on western wheatgrass in the Great Plains; it is preferred by bison to blue grama in northeastern Colorado [74,112,142]. Western wheatgrass makes up a higher percentage of bison diets on heavily grazed ranges than on lightly grazed sites [112]. In Wind Cave National Park, South Dakota, elk consume western wheatgrass during the fall, winter, spring, and summer [172]. It is eaten by white-tailed deer in eastern and central Montana, with heaviest use during the spring [4].

Western wheatgrass is used by various small mammals. It is heavily used by pocket gophers from May through September [35]. It is also heavily grazed by black-tailed prairie dogs in South Dakota [83].

PALATABILITY:
Western wheatgrass is described as "very palatable" [31]. New growth is particularly palatable to cattle and to domestic sheep. Plants often become coarse by early summer and palatability declines [68]. In some areas plants may become "stemmy and unpalatable" by late summer [130]. The degree of use shown by livestock and wildlife species is rated as follows:
                     CO    MT    ND    UT    WY
Cattle              Good  Good  Good  Good  Good
Domestic sheep      Fair  Fair  Fair  Fair  Good
Horses              Good  Good  Good  Good  Good
Pronghorn           ----  Poor  Poor  Fair  Fair
Elk                 ----  Good  ----  Fair  Good
Mule deer           ----  Poor  Poor  Fair  Fair
Small mammals       ----  Poor  Poor  Good  Fair
Small nongame birds ----  Poor  Poor  Fair  Fair
Upland game birds   ----  ----  Poor  Fair  Fair
Waterfowl           ----  ----  Good  Fair  Fair
NUTRITIONAL VALUE:
Western wheatgrass is described as "highly nutritious" [31]. It is rated as "good" in energy value and "fair" in protein value [45].

However, protein content varies by plant part and by seasonal development. Protein content peaks during the period of most rapid growth in the southern plains (usually in April) and is generally lowest at or just after the end of flowering [129]. Specific crude protein values are as follows [111]:

early May                     31.6%
regrowth in early July        13.0%
late 1st harvest early July    9.8%
1st harvest late July          7.9%
In-vitro digestible dry matter by season is as follows [111]:
initial harvest early May     74.5%
initial harvest mid May       76%
late 1st harvest early July   59%
1st harvest late July         54%         
In a Wyoming study, calcium and magnesium content did not increase with maturity and the iron content remained fairly constant during the growing season, but manganese increased after September 30th and phosphorus became deficient prior to August 17th. Crude protein content declined steadily from 14.5% on June 29th to 4.7% by October 29th [117].

Protein content per gram is greater in the tops, roots, and rhizomes of clipped plants than in nonclipped plants; the soluble sugars and starch per gram are less in clipped plants. Recovery and growth of plant tops is prevented by frequent removal of vegetation [65,50]. The nutrient quality of plants can also be altered by defoliation by grasshoppers. Severe defoliation can produce decreased foliar nitrogen and carbohydrates, and can increase phenolic concentrations [118].

COVER VALUE:
Western wheatgrass can be used to produce good stands of nesting cover for various ducks in the Dakotas [91]. It provides good nesting sites for mallards, gadwalls, and blue-winged teal [99]. Grasses, including western wheatgrass, are frequently selected for nesting sites by green-winged teal, pintail, and northern shoveler [138]. The degree to which western wheatgrass provides cover for wildlife species is as follows [45]:
                         MT        ND        UT        WY
Pronghorn               Poor      Fair      Poor      Poor
Elk                     Poor      ----      Poor      Poor
Mule deer               Poor      Fair      Poor      Poor
White-tailed deer       Poor      Fair      ----      Poor
Small mammals           Fair      Good      Fair      Good
Small nongame birds     Fair      Good      Fair      Good
Upland game birds       Fair      Good      Poor      Fair
Waterfowl               Good      Good      Poor      Fair
VALUE FOR REHABILITATION OF DISTURBED SITES:
Western wheatgrass is a good soil binder and is well suited for reclamation of disturbed sites such as surface coal mines, erosion control, and soil stabilization [37,105,139]. It is commonly included in seed mixtures used for rangeland seeding, revegetation of saline-alkali areas such as saltwater blowout sites, and in critical areas for erosion control [27,69]. It can also be seeded onto wet areas or waterways [131].

Since rhizomes may persist in land broken for cultivation, western wheatgrass spreads rapidly on abandoned land [121,153]. In Wyoming and Montana, western wheatgrass is one of the most promising grasses for reclaiming saline seeps, as well as other problem sites [121]. In Nebraska and Saskatchewan, it shows potential value for controlling wind erosion in sand blowouts or on dunes [67,103,126]. Western wheatgrass is used for roadside revegetation at "higher elevations" in Arizona, and along roadsides in Iowa [24,47].

In Arizona, successful coal-mine reclamation included the use of fertilizers, a combination of natural rainfall and sprinkler irrigation for the first 2 years, and seeding perennial grasses including western wheatgrass, crested wheatgrass (Agropyron cristatum), and Indian ricegrass (Achnatherum hymenoides) [129]. The effects of 3 soil materials, 3 mulching treatments, and 2 soil moisture treatments on the growth and forage production of western wheatgrass when used in the reclamation of coal mine spoils were investigated during a 3-year experiment in Arizona. Average stems per pot and dry forage yield per pot for western wheatgrass were determined for all treatment combinations. The highest number of stems per plot, the tallest plants, and the highest forage yield were produced with Gila loam soil, barley straw mulch, and soil moisture treatment with maximum production. More vigorous plants and more forage were produced when soil mulch was used than when soils were not mulched [36].

Vesicular-arbuscular mycorrhizae are a common component of arid soils. They usually increase nutrient and water intake, as well as increasing the dry mass of plants. The disturbance of land often leads to the reduction or elimination of mycorrhizal fungi propagules. Workers investigating the development of vesicular-arbuscular mycorrhizae and proliferation of roots of western wheatgrass in a revegetated mine spoil in southeastern Wyoming found that western wheatgrass was not highly dependent on mycorrhizal infection for survival [100]. Researchers at the Kemmerer Coal Mine in southwestern Wyoming found that mycorrhizae benefited western wheatgrass [3].

Western wheatgrass can be successfully drilled or broadcast seeded [5,88]. It can be successfully seeded during the spring or fall [120]. Numerous cultivars, adapted to a wide range of environmental conditions, are available for commercial use [7,10,53,79,121,139]. 

OTHER USES AND VALUES:
Native and seeded stands of western wheatgrass are used for pasture and hay [152].

OTHER MANAGEMENT CONSIDERATIONS:
Western wheatgrass can tolerate moderate grazing but is damaged by close spring grazing [152]. Heavy grazing "may be tolerated, but production will be lowered considerably by this practice" [130]. Western wheatgrass is a decreaser on upland sites in the Great Plains with less than 20 inches (500 mm) average annual precipitation. In areas with over 20 inches, it is an increaser. When western wheatgrass is mixed with taller or more palatable species, it often increases. When it is mixed with shorter grasses and warm-season species, western wheatgrass decreases when grazed early in the spring [152]. However, Hafenrichter and others [68] report that continuous early spring grazing of mixed stands can result in nearly pure stands of western wheatgrass. Western wheatgrass increases in both density and frequency after grazing and chaining in pinyon-juniper communities [149].

Western wheatgrass is susceptible to grasshopper damage during moderate to heavy infestations. In prolonged wet periods, forage quality is decreased from ergot, as well as leaf and stem rusts [152].

In some instances large increases in western wheatgrass have been reported after herbicide application. In a Wyoming study, increases of 260% were reported within 2 years of herbicide applications, with increases of 490 to 720% live canopy cover reported during the 7th year after application [167]. Detailed information on response to various herbicides is available [114,167].

In North Dakota, western wheatgrass produces approximately 1/3rd of its annual yield prior to May 20th. The bulk of production occurs from May 20th to June 30th [165].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Pascopyrum smithii
GENERAL BOTANICAL CHARACTERISTICS:
Western wheatgrass is a long-lived, native perennial, cool-season, endomycorrhizal grass [114,115]. It is an aggressive sod-forming grass characterized by an abundance of long, branched rhizomes [10,27]. Rhizomes allow plants to survive moderately severe drought [152]. The erect culms reach 12 to 36 inches (30-90 cm) in height [130].

Rhizomes lie 0.5 to 2 inches (1.3-5 cm) below the soil surface. The highly branched root system may penetrate the soil to a depth of 7 feet (21 m). In the deep rich soils of eastern Nebraska and Kansas, roots may extend as deep as 11.8 feet (3.6 m). Root extensions in more arid eastern Colorado may extend downward to depths of only 4.9 feet (1.5 m) [34]. In dry grasslands of Montana, only 6% of the roots of western wheatgrass were observed in the top 0 to 0.5 inch (0-1 cm) soil layer.

Longevity of western wheatgrass roots was studied by banding roots of plants grown in containers from seed. In the second year 55 and 60% of the banded roots were dead. By the end of the second summer western wheatgrass roots had a survival of 42% [154]. Zhang and Romo [174] report tiller longevity of 2 to 3 years in Saskatchewan.

RAUNKIAER LIFE FORM:
Geophyte

REGENERATION PROCESSES:
Western wheatgrass regenerates vegetatively through rhizomes to form uniform stands [68]. It also spreads via seeds. A limited seed supply usually matures late, but this is offset by reproduction from rootstocks [150]. Stands are slow to develop from seed [27], but once established are vigorous, hardy, and drought resistant. Seeds germinate slowly, but a fairly uniform sod is usually obtained within 2-3 years [10].

Western wheatgrass exhibits a low and much-delayed germination at 66 to 73 degrees Fahrenheit (19-2 oC) [26,114,145]. Germination is most successful with alternating temperatures of 59 degrees Fahrenheit (15 oC) and 86 degrees Fahrenheit (30 oC) [39]. Light does not affect germination [122,141].

Peak germination response for western wheatgrass was 94% at 65 degrees Fahrenheit (18.5 oC) for 8 hours and 50 degrees Fahrenheit (10 oC) for 16 hours. The mean germination time was 11.8 days. In constant temperature without light, germination percentages decrease [93,122].

SITE CHARACTERISTICS:
Western wheatgrass is drought tolerant, and established stands can survive even extended periods of drought [27,68,130]. It commonly occurs along ephemeral creeks where it grows through thick layers of silt in areas that flood in spring [9,68]. It also grows on well-drained upland sites [130]. Western wheatgrass grows in mesic areas, swales, overflow sites, and subirrigated lowlands. Western wheatgrass is tolerant of periodic flooding, poor drainage, and water tables within 6 inches (15 cm) of the soil surface [27].

Western wheatgrass commonly grows on medium to heavy textured soils [27]. It can grow on even heavy gumbo soils, but does poorly on sand [9,130]. In parts of Colorado, western wheatgrass grows on clayey soils with an average pH of 7.78 [9].Western wheatgrass is highly tolerant of saline to alkali soils [27]. Western wheatgrass is adapted to areas that receive 14 to 35 inches (360-870 mm) of average annual precipitation [130].

Elevational ranges vary as follows [45]:

    3,600 to 10,000 feet (1098-3049 m) in Colorado
    2,400 to  3,600 feet (732-1098 m)  in Montana
    4,200 to  7,500 feet (1280-2677 m) in Utah
    3,400 to  8,200 feet (1037-2500 m) in Wyoming
 
SUCCESSIONAL STATUS:
Western wheatgrass occurs in all seres. It is however, frequently described as a "late successional species" [89,127]. It is present in many climax plant communities [115]. Western wheatgrass increases during secondary succession. Its ability to rapidly reestablish after disturbance is attributed to its rhizomatous growth habit [123]. Samuel and Hart [124] report that it typically appears much earlier and in much greater abundance than other long-lived perennial grasses on disturbed sites in Wyoming.

Western wheatgrass grows in a variety of successional stages in sagebrush (Artemisia spp.) communities. It has been described as a "mid-seral species" in semi-arid sagebrush communities of northwestern Colorado. In these sagebrush communities, annual forbs dominate disturbed sites for the first 2 years after disturbance. By year 3, cheatgrass (Bromus tectorum) typically becomes dominant and perennial grasses such as western wheatgrass become dominant by the 4th year after disturbance [104]. In big sagebrush communities, western wheatgrass may among the earliest species to become prominent following disturbance [19]. In Wyoming big sagebrush communities, western wheatgrass dominates "late intermediate seral stages" in steppe communities [16]. It replaces blue grama in "early intermediate seral stages" and is replaced by big sagebrush later in succession.

Western wheatgrass is common on disturbed sites (abandoned towns) in parts of southwestern Montana [92]. During the drought of the 1930s, western wheatgrass supplanted tall grasses over much of the eastern Kansas prairie [113]. Grasses reverted to the original composition as more "normal" (more moist) conditions returned.

In certain Montana riparian communities, years of heavy grazing can cause cottonwood stands to be replaced by shrub/grass communities dominated by silver sagebrush (Artemisia cana), greasewood (Sarcobatus vermiculatus), and western wheatgrass [70].

SEASONAL DEVELOPMENT:
Western wheatgrass produces best growth in spring. Flowering occurs in June, and seeds ripen in August or September [150]. In South Dakota, vegetative growth typically begins in early June, flowering begins by mid to late June, and seeds shatter by mid-August [85]. Flowering dates by state are as follows [45]:

State   Earliest date observed   Latest date observed
CO      June                     August
MT      June                     August
ND      June                     July
WY      June                     August
A representative phenology for a population of western wheatgrass from the northern Great Plains is as follows [143]:
Dormancy         5-20 November
Early growth    15-20 April
Rapid growth     1-10 June
Boot stage       1-15 August
A western Wyoming study of phenological development of western wheatgrass from 1973 to 1975 showed that "normal" seed dissemination was difficult to predict as inflorescences appearing in July did not necessarily produce viable seed. Seed may not shatter until late fall or early the following summer [90].
Phenology           Range                Average
Growth initiation   March 5-April 26     March 15
Full bloom          June 20-July 20      July 10
Start of seed       July 25-November 20  August 15
  dissemination

In northeastern Colorado, the following phenological development was observed [44]:

Floral buds and open flowers                  Early June
Floral buds, open flowers and ripening fruit  Mid-June
Buds, flowers, green and ripe fruit           Early June
Bud, flowers, green, ripe fruit and 
  dispersing seed                             End of July-Early August

Green and ripe fruit, dispersing seed and
  senescence                                  Early October   
In a 2nd Colorado study, seasonal growth was initiated by the 2nd or 3rd week of April and flowering began by the 1st week of June, with maximum flowering by the 3rd week of June. Maximum rate of leaf area increase occurred from late May through June [109]. In Texas, western wheatgrass generally begins fall growth by September. The short growing period in the fall is followed by peak growth in late spring (April) when maximum leaf widths are reached. Plants did not grow during winter, even under irrigation [129].

The growth and phenological stages of western wheatgrass plants are inversely related to carbohydrate reserve storage. Lowest root and crown total nonstructural carbohydrate (TNC) levels are reached during the 3rd leaf stage in April. The highest TNC levels occur during the 5th leaf stage in late June and at the end of the growing season, fall quiescence [106]. Seed maturity occurs when water concentrations reach approximately 300 to 350 g/kg (dry weight basis) [17]


FIRE ECOLOGY

SPECIES: Pascopyrum smithii
FIRE ECOLOGY OR ADAPTATIONS:
The major adaptation of western wheatgrass to fire is its rhizomatous growth form [151]. Western wheatgrass is characterized by loosely clustered, coarse culms with a minimum of leafy material. During a fire these culms usually burn rapidly with little heat transferred downward into meristematic tissue.

Fire did not alter species composition after fire in a South Dakota mixed-grass prairie community containing western wheatgrass [158]. This may not be true of all communities in which western wheatgrass occurs. To learn more about the fire regimes in specific communities in which western wheatgrass occurs, refer to the FEIS summary for those species, under "Fire Ecology or Adaptations."

POSTFIRE REGENERATION STRATEGY:
Rhizomatous herb, rhizome in soil

FIRE EFFECTS

SPECIES: Pascopyrum smithii
IMMEDIATE FIRE EFFECT ON PLANT:
Western wheatgrass is generally unharmed by fire. Smith and Busby [134] report that it is "slightly damaged" by fire in Wyoming. Rhizomes may be damaged but are generally not killed by fire.

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
No entry

PLANT RESPONSE TO FIRE:
Western wheatgrass cover usually increases or changes little after fire. On sagebrush (Artemisia spp.)-grass ranges western wheatgrass often revegetates rapidly after fire [152]. Recovery occurs within 2 to 5 years in sagebrush and pinyon-juniper zones of the Intermountain region [147,148,161]. In Nevada, western wheatgrass increased in frequency after fire; above ground biomass increased more than 7 times above preburn levels during the 1st postfire season [28]. In sagebrush (Artemisia spp.) communities of Wyoming, western wheatgrass generally increases after fire [133]. In eastern Montana, western wheatgrass production was unaffected by spring or fall burns [75]. In some instances, vegetative spread of western wheatgrass is enhanced by fire [158].

Variable responses by season of burn have been reported for western wheatgrass. Spring burns often favor western wheatgrass [6] by increasing density during the 1st growing season after fire [60,157]. Although the height of western wheatgrass is reduced by burning at all dates, plants usually increase in abundance and density after spring fire [2,21,36,,45,48,66,68,85,86,89]. In the northern Great Plains, best response of western wheatgrass may be observed after very early spring (March-April) or late summer burns [76]. Kruse and Higgins [94] report that spring burns may produce increases, decreases or no change in western wheatgrass cover. Gartner and White [63] report that late spring and early summer burns can cause increases or decreases during the 1st growing season, but no difference between preburn and control was evident by the 2nd growing season in mixed-grass prairie communities.

Fall burns can also stimulate productivity of western wheatgrass, but sometimes to a lesser degree than can spring burns [162,163]. In Montana, plants burned in fall and spring exhibited similar yields after mid-May [163]. Studies in eastern Montana indicate that western wheatgrass increases in abundance after spring, summer, and early fall burns. However, best response was noted after late summer or early fall fires [75].

Summer burns generally produce increases in western wheatgrass cover or production [94]. In the northern Great Plains, best response of western wheatgrass may sometimes be observed after late summer (August-September) burns [76].

Winter burns produce no change or result in increases in cover in South Dakota [63].

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
On a clay upland range site with a shortgrass mixture of buffalo grass and blue grama in Kansas, a March fire consumed dry vegetation to ground level. Western wheatgrass yields did not fully recover until the 3rd growing season after the fire. For the 1st and 2nd years, it was reduced 82% and 39%, respectively [98].

In western North Dakota on a mesic mixed-grass prairie with annual precipitation of 16 inches (410 mm), the effects of 3 wildfires (May, August, and September) were studied on areas subject to trespass grazing. Frequency of western wheatgrass plants remained the same or higher than before burning on all 3 treatments.

In western South Dakota, yield and density of western wheatgrass were increased by late winter or early spring burns [22]. Western wheatgrass and Japanese brome (Bromus japonicus) were codominants in Badlands National Park in west-central South Dakota on land that had not been cultivated or grazed for at least 25 years. A study investigating the effects of fire on western wheatgrass found that vegetative propagation of western wheatgrass was enhanced immediately following burns and growth returned to the level of unburned plots during the 2nd growing season. Plots were burned in April and May, 1983 and 1984, and clipped in April 1983. Western wheatgrass spread vegetatively during the 1st growing season but often did not produce seed until the 2nd growing season following burning [152].

Although growth of new shoots from rhizomes can sometimes be retarded by early spring burning, this effect often does not persist, as fall- and spring-burned plants have similar yields after mid-May. In eastern Montana, spring-burned plants quickly overcame initial slow growth and herbage yields equaled those on fall-burned plots [163]. By mid-June spring burned plots may have higher yields of western wheatgrass than adjacent unburned plots [128,161,170]. In an eastern Montana study, spring and fall-burned plots produced significantly more (P < 0.05) forage than unburned plots, but by the end of July, no differences were noted [163]:

season and treatment      percent basal cover         
fall burn                 19.0%
spring burn               14.3%
clipped not burned        14.4%
untreated control         15.3%

Following years in which precipitation is below average, western wheatgrass tiller density may be lower in plots with "reduced surface litter," such as burned plots, than in areas with undisturbed surface litter [158]. Plants on burned plots may dry out more rapidly than on unburned areas and may provide less standing forage after early July. Reductions in western wheatgrass yields after late spring burns have been attributed to moisture stress [162].

For further information on western wheatgrass response to fire, see Fire Case Studies. The Research Project Summary Seasonal fires in Saskatchewan rough fescue prairie provides information on prescribed fire use and postfire response of plains grassland community species, including western wheatgrass, that was not available when this species review was originally written.

FIRE MANAGEMENT CONSIDERATIONS:
Burns in the spring after new growth is initiated can severely injure western wheatgrass [148]. Bushey [28] reported that prescribed fire generally has a positive impact on the frequency and aboveground biomass of western wheatgrass in Nevada.

In the northern Great Plains, forage yield can be increased with the use of fire and careful timing of reintroduction of livestock to the burned range [151]. Areas burned can become attractive to grazers where yields and density of western wheatgrass increase [22]. After fire, western wheatgrass recovers more rapidly on ungrazed pasture than on grazed plots [32].

Forage quality can be improved with burning [151]. Burning (with or without mechanical treatments) can increase the crude protein content of western wheatgrass within the first postfire growing season. Results from a South Dakota area burned in the spring of 1984 are as follows [60]:

Mean crude protein (%) clipped at ground level:

                 Treatment
				
burning      none  burn  burn    burn     burn 
mechanical   none  none  contour pitting  rip &
                         furrow           furrow
1984        8.19   8.56  10.25   8.94    9.54
1985       12.94  10.50  10.81  10.37    9.81
Frequent defoliation of western wheatgrass severely reduces plant reserves. In northern Colorado on a shortgrass prairie, a 14- to 26-month resting period from grazing was sufficient for the recovery of plants from a single heavy defoliation. After this period plants exhibited vigor and total nonstructural carbohydrate levels which were similar to control plants [29,30]. Defoliation during dormancy had the least effect on yield [143]. A greenhouse study showed that the frequency of clipping significantly ("P=5%") reduced cumulative aboveground production of western wheatgrass. The height of clipping affected aboveground and belowground production. Western wheatgrass plants that were clipped at either a 2 inch (5.0 cm) or 4 inches (10.0 cm) stubble height had significantly (P=0.05) less root biomass than did unclipped control plants [125].

Fine fuel amounts should total at least 600 lbs/acre for good fire spread in rhizomatous wheatgrass [133].


FIRE CASE STUDIES

SPECIES: Pascopyrum smithii

1st CASE STUDY:

FIRE CASE STUDY CITATION:
Tirmenstein, D., compiler. 1999. Prescribed burning on a ridge and meadow in Wind Cave National Park, South Dakota: effects on western wheatgrass. In: Pascopyrum smithii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [ ].

REFERENCE:
Gartner, F. Robert. 1975. Final Report: Wind Cave National Park grassland ecology. Unpublished paper on file at: U.S. Department of Agriculture, Forest Service, Intermountain Research Station Intermountain Fire Sciences Laboratory, Missoula, MT: 29 p. [61].

SEASON/SEVERITY CLASSIFICATION:
No entry

STUDY LOCATION:
The study was conducted in the northwest corner of Wind Cave National Park in southeastern South Dakota. Bordering the site to the north and west is a park perimeter fence. Gravel roads occur south and northeast of the site. A major paved highway through the park, SD 87, provided a fuelbreak on the east side of the study site.

PREFIRE VEGETATIVE COMMUNITY:
Two distinct plant communities were present on the ridge and meadow sites. The Ridge was dominated by western wheatgrass (Pascopyrum smithii). Green needlegrass (Nassella viridula) was also common. Other, shorter graminoids included blue grama (B. gracilis), buffalo grass (Buchloe dactyloides), Japanese brome (Bromus japonicus), and sedges (Carex spp.).

Vegetation in the meadow was dominated by Kentucky bluegrass (Poa pratensis); western wheatgrass was also abundant. Green needlegrass and blue grama were common. There were very few ponderosa pine (Pinus ponderosa) trees in the meadow areas, and pine seedling encroachment was minimal.

TARGET SPECIES PHENOLOGICAL STATE:
No entry

SITE DESCRIPTION:
Annual precipitation averages 18 inches (450 mm), with about 3/4th of it occurring in the growing season. Site characteristics were:

Ridge - Soils on the ridge site are deep loams with clay on the surface. Aspect is level. Elevation is 3,700 feet (110 m).

Meadow - Meadow soils are moderately deep (12 to 24 inches (30-60 cm)), stony clays. Aspect is east; elevation is 3,926 feet (1178 m).

FIRE DESCRIPTION:
Objectives were to control ponderosa pine encroachment onto grassland and to evaluate effects of burning in different seasons. Treatments were: (1) prefrost fall burning (18 Sept. 1973); (2) postfrost winter burning (13 Feb. 1974); (3) early spring burning (10 April 1974); and (4) no burning (control). Total fuel load was more than 2 tone/acre (oven dry) and did not vary significantly between burning dates. Herbaceous fuels averaged 4,814, 4,234, and 4,895 lbs/acre on the ridge, slope, and meadow sites, respectively. Conditions at time of burning were as follows:
Fall fire
       Temperature  Relative  Wind speed  Wind       Time
       (oF)         humidity  (miles/h)   direction
Ridge  78           24        5-7         S-W        1330
Meadow 77           30        5-6         SE-NE      1450

Winter fire
       Temperature  Relative  Wind speed  Wind       Time
       (oF)         humidity  (miles/h)   direction  
Ridge  49           34        3-5         E          1205
Meadow 50           36        5-8         SE         1335

Spring fire
       Temperature  Relative  Wind speed  Wind       Time
       (oF)         humidity  (miles/h)   direction
Ridge  50           52        7           NE         0930
Meadow 45           64        10-15       N-NE       1100
FIRE EFFECTS ON TARGET SPECIES:
Density of western wheatgrass was greater on all burned sites compared to the unburned site; however, yields were pronouncedly different between replicates. Yields increased after spring burning on the ridge but were slightly reduced on the slope and meadow sites. One month after fall burning, western wheatgrass was 1 to 2 inches (2.5-5 cm) tall. In general, fall- and winter-burned treatments greened-up later and grew more slowly than the spring-burned site. Recovery of western wheatgrass on 26 May 1974 was as follows:
Ridge
             Fall     Winter     Spring     Unburned
  
Height (cm)  21.6     21.9       22.9       27.5
yield(kg/ha) 869      725        1208       104


Meadow       
             Fall     Winter     Spring     Unburned
  
Height (cm)  18.2     19.6       20.5       22.0  
Yield(kg/ha) 66       95         95         261 
FIRE MANAGEMENT IMPLICATIONS:
Spring burning will probably produce more forage of western wheatgrass and other cool-season grasses than will fall burning.


2nd CASE STUDY:
FIRE CASE STUDY CITATION:
Tirmenstein, D., compiler. 1999. Burning in bluestem and mixed-grass prairies in Wind Cave National Park, South Dakota: effects on western wheatgrass. In: Pascopyrum smithii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [ ].

REFERENCE:
Schripsema, Janet R. 1978. Ecological changes on pine-grassland burned in spring, late spring and winter. Rapid City, SD: South Dakota State University. 99 p. Thesis. [128].

SEASON/SEVERITY CLASSIFICATION:
Fires were conducted in late winter (March 1), early spring (Apr. 21) and late spring (May 27). Severity was not specified, but the fires were severe enough to kill 65% to 95% of young ponderosa pines (Pinus ponderosa) less than 3 feet (1 m) tall.

STUDY LOCATION:
Wind Cave National Park is in a semiarid region of the Black Hills in South Dakota. The 2 study areas within the park were: the Rankin Ridge study area in the northwest corner of the park and the Wind Cave Canyon study area about 2 miles (3.3 km) east of park headquarters on the south slope of Wind Cave Canyon.

PREFIRE VEGETATIVE COMMUNITY:
The vegetation on the Rankin Ridge site was dominated by little bluestem (Schizachyrium scoparium) and big bluestem (Andropogon gerardii). Western wheatgrass (Pascopyrum smithii), Sandberg bluegrass (Poa secunda), Kentucky bluegrass (P. pratensis), grama grasses (Bouteloua curtipendula and B. gracilis,), and Canada bluegrass (P. compressa) were common. Ponderosa pine was encroaching on the site.

At the Wind Cave Canyon study site, the mixed-grass prairie consisted of needle-and-thread grass (Hesperostipa comata), green needlegrass (Nassella viridula), western wheatgrass, bluebunch wheatgrass (Pseudoroegneria spicata), and the following shortgrasses: sideoats grama (Bouteloua curtipendula), blue grama (B. gracilis), hairy grama (B. hirsuta), and buffalo grass (Buchloe dactyloides).

TARGET SPECIES PHENOLOGICAL STATE:
Fires were conducted when plants were actively growing.

SITE DESCRIPTION:
Average annual precipitation is 18 inches (460 mm). On the Rankin Ridge site, soils are deep cobbly loams with a 6 to 15% slope. Aspect is north-northeast; elevation is between 4,440 and 4,4480 feet (1353 and 1366 m).

On the Wind Cave Canyon site, soils are deep silty loams on a 2 to 6% slope. Elevation is between 3,980 and 4,000 feet (1213 and 1219 m)
Weather conditions at time of the fires were as follows: 

Date    Time Location      Temp.       RH      Wind
of burn                                       (mph)
5/27/76 0900 Rankin Ridge  70oF(21oC)  38%     ENE 4-7
3/1/77  1100 Rankin Ridge  30oF(-11oC) 78%     SSE 3-6
4/21/76 0600 Wind Cave     48oF(9oC)   49%     NNW 4-9
4/21/76 0825 Wind Cave     70oF(21oC)  40% N   W   7-12* 
*At 0845 the wind switched to SE at 8-12 mph. 
FIRE DESCRIPTION:
In the spring 30 acres (12 ha) were burned at the Rankin Ridge site with an additional 45 acres (18 ha) burned in the winter. The late spring burn (May 27, 1976) was initiated on the northwest and southwest edges of the site. The fire then burned into the wind, widening the firebreaks. The northeast and southeast edges were then ignited and a headfire carried the fire across the study area. In the late winter (March 1, 1977), a burn was ignited at the southwest corner. The northwest, northeast, and southwest lines were widened by burning into the wind. Once the lines were widened the southeast edge was ignited, and a headfire carried the fire across the study area. Burning was initiated at about 1000 hours and completed by 1130.

On the Wind Cave Canyon study area, 35 acres (14 ha) were burned. Vegetation was burned between two strips of fire retardant that were about 6 to 9 feet (2-3 m) apart. Both burns at this study site were conducted on March 21, 1976. The south fire line was reinforced by burning west to east strips from the existing line toward a slope. The fire was then backed downhill through mountain-mahogany (Cercocarpus spp.) to reduce fuels and minimize damage to shrubs. Along the east end of the area the fire burned with the wind through ponderosa pine. Burning was initiated at about 0830 and completed by 1130.

FIRE EFFECTS ON TARGET SPECIES:
All burning treatments decreased western wheatgrass plant height. The late spring burn on Rankin Ridge had lower yield of western wheatgrass the first postfire year but not the second year. Yield on the late winter burn did not differ significantly (p=0.10) from that on control plots. On the Wind Cave Canyon mixed-grass prairie burns, western wheatgrass yields were significantly greater on burned than unburned sites. Yields (g/m2) were as follows:
 
Location     Rankin Ridge             Wind Cave Canyon
tmt.    control  3/1 burn  5/27 burn  control 4/21 burns
1976    2.11     -----     1.28*      6.25    17.51*
1977    2.39     3.54      1.00       4.31    13.48*   
* significantly different from unburned areas at p=0.10
FIRE MANAGEMENT IMPLICATIONS:
Prescribed burning is effective for creating firebreaks for 4 to 5 years, or until the mulch layer is replaced. Burning when mulch is moist helps retain a mulch layer that reduces evaporation from the soil, thus increasing grass yields. The size of burned areas can affect postburn recovery, since bison attracted to burns can easily overgraze small areas.

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