• IMPORTANCE TO LIVESTOCK AND WILDLIFE
• PALATABILITY
• NUTRITIONAL VALUE
• COVER VALUE
• VALUE FOR REHABILITATION OF DISTURBED SITES
• OTHER USES AND VALUES
• MANAGEMENT CONSIDERATIONS

IMPORTANCE TO LIVESTOCK AND WILDLIFE:

Bluebunch wheatgrass is considered one of the most important forage grass species on western rangelands for both livestock and wildlife [213,225].

PALATABILITY:

Although bluebunch wheatgrass can be a crucial source of forage, it is not necessarily the most highly preferred species. In cattle feeding trials of 8 range grasses, bluebunch wheatgrass was less palatable than crested, western (Pascopyrum smithii), and slender (Elymus trachycaulus) wheatgrasses, tall oatgrass (Arrhenatherum elatius), California brome (Bromus carinatus), smooth brome (B. inermis), and orchardgrass (Dactylis glomerata) [145]. In another cattle trial, bluebunch wheatgrass was the least preferred of crested, thickspike (E. lanceolatus), and bluebunch wheatgrasses [152]. In a tractable elk feeding trial with Rocky Mountain elk, bluebunch wheatgrass was chosen less frequently than thickspike and crested wheatgrasses [152]. In tractable mule deer feeding trials, bluebunch wheatgrass was not a preferred plant [21].

Older bluebunch wheatgrass plants lose palatability [31,151].

Livestock and wildlife use of bluebunch wheatgrass is as follows [22,29,31,34,43,45,95,109,117,140,146,151,157,157,161,163,167,171,173,178,181,182]:

                   ID             NV          OR          
cattle             high           high        high        
domestic sheep     ----           high        ----       
elk                medium-high    high        ----         
mule deer          medium         ----        medium-high 
white-tailed deer  high in spring ----        ----         
bison              ----           ----        ----        
pronghorn          low            medium      low          
bighorn sheep      high           ----        ----         
feral horses       ----           ----        high         
jackrabbits        ----           ----        ----        


                   MT               UT          BC
cattle             high             ----        ----
domestic sheep     ----             low         ----
elk                high in winter   medium      ----
mule deer          high in spring   medium-high ----
white-tailed deer  ----             ----        ---- 
bison              medium in winter ----        ----
pronghorn          low              ----        ----
bighorn sheep      high in winter   ----        low-medium
feral horses       ----             ----        ----
jackrabbits        ----             medium      ----

NUTRITIONAL VALUE:

Bluebunch wheatgrass is nutritionally sufficient for some animals for only part of the year. In central Utah, bluebunch wheatgrass had 26.0% protein in spring and 13.6% in fall. Sixteen percent is considered to be the maximum requirement for mule deer. Digestible dry matter was 72.3% in spring and 59.9% in fall. In winter, the forage quality of bluebunch wheatgrass is inadequate for elk maintenance in northeastern Oregon [65].

Bluebunch wheatgrass had the lowest crude protein content of 15 forage species in Oregon from flowering in July through maturity. Seasonal variation ranged from almost 25% in May to less than 5% in November [135]. McInnis and Vavra [173] obtained the following crude protein values in Oregon: spring, 16.3%, summer, 5.7%, fall, 3.7%, and winter, 2.3%.

Percent nutrient content of beardless wheatgrass for domestic sheep in the Great Basin was as follows [74]:

Date       Ether     Total     Lignin   Cellulose                
           extract   protein                       
12-14-52   5.1       2.8       7.3      34.9       
11-13-53   3.1       3.4       8.4      42.0       
Mean       4.1       3.1       7.8      38.4       

           Other carbo-  Ash    Ca     P     Carotene                   
           hydrates                          (΅g/lb)
12-14-52   39.0          11.0   0.50   0.05  0.5
11-13-53   33.0          10.2   0.48   0.06  ---
Mean       36.0          10.6   0.49   0.06  0.5

COVER VALUE:

Bluebunch wheatgrass does not generally provide sufficient cover for ungulates, but the communities are well used when there is appropriate cover nearby. In northeastern Oregon, perennial grasslands featuring bluebunch wheatgrass were generally avoided by white-tailed deer unless hiding cover was nearby [32]. However, mule deer were frequently found in bluebunch-dominated grasslands [43].

In northwestern Montana, Columbian sharp-tailed grouse nests are found primarily under rough fescue (Festuca scabrella) and bluebunch wheatgrass plants [112].

In central Montana, pronghorn are most commonly found in sagebrush-bunchgrass habitats, of which bluebunch wheatgrass is an important component [29].

VALUE FOR REHABILITATION OF DISTURBED SITES:

Bluebunch wheatgrass seeds are not easily harvested and can be expensive, which, along with some of its botanical characteristics, makes the plant a less desirable choice for reclamation projects [51,89].

Bluebunch wheatgrass seedlings are considered to be fairly weak [159]. Seeding trials with bluebunch wheatgrass have shown limited success. In southern Idaho, bluebunch wheatgrass seedlings failed to establish on 71% of 134 plots, although beardless bluebunch wheatgrass did better than bluebunch wheatgrass, with only 46% of 74 plots failing [144]. Beardless bluebunch wheatgrass was drilled and broadcast seeded in a native seed mix in trials to revegetate a coal mine site in southeastern Montana, but did not perform well [90]. When bluebunch wheatgrass was seeded with a mix of other wheatgrasses (Triticeae) in southern Idaho, including crested wheatgrass, crested wheatgrass eventually dominated the site, and bluebunch wheatgrass disappeared from the study plots [144].

Once established, mature bluebunch wheatgrass plants feature extensive root systems, so they are excellent soil stabilizers [126].

OTHER USES AND VALUES:

No entry

MANAGEMENT CONSIDERATIONS:

Bluebunch wheatgrass is moderately grazing tolerant only during its nongrowing period. Lightly grazed plants produce higher growth than ungrazed plants [109]. The plant is extremely sensitive to defoliation during active growth [10,18,39,50,76,85,125,131,134,164,171,174,183,195,211]. Even grazing by small mammals can negatively affect the vigor of bluebunch wheatgrass [200]. Montane meadow mice grazing bluebunch wheatgrass in the winter in Washington significantly reduced survivorship of seedlings [199].

Some authors suggest grazing should be delayed until the late boot stage to protect the stand from degradation [19,31,128]. Heavy grazing may result in degradation or mortality of the stand, and the plant is considered a grazing "decreaser" [41,73,85]. Heavier grazing treatments result in lower root and stem carbohydrate reserves. If reserves are too low going into the winter, the plant may die [110]. In the seedling stage, the slow development of the roots makes plants susceptible to being pulled from the ground during early grazing [166].

Appropriate management may alleviate degradation problems. Eckert and Spencer [100] studied the effects of a rest-rotation grazing system on the mean live basal area of bluebunch wheatgrass in Nevada. Although some of the grazing occurred during the growing season, no significant difference was found in basal area between the grazed and ungrazed plots after 6 years.

In southeastern Idaho, study plots open to domestic sheep grazing over a 10-year period showed significant (P<0.05) decreases in density and frequency of bluebunch wheatgrass, the dominant grass in the habitat type. The authors characterized this decrease as a deterioration of range condition. On sample plots in the study open to cattle grazing, no statistically significant changes were found in cover (basal area) of bluebunch wheatgrass [12].

Root development in bluebunch wheatgrass is slower than in a crested wheatgrass/desert wheatgrass hybrid, cheatgrass (Bromus tectorum) [18], and crested wheatgrass [28]. Drought resistance was better in crested wheatgrass than bluebunch wheatgrass in a 3-year drought and drought-and-clipping study [58]. The rates of leaf, daughter tiller and total leaf area production, height growth, and total and regrowth yield for both species were lowest under the drought and clipping treatment.

Bluebunch wheatgrass is susceptible to competition from diffuse (Centaurea diffusa) and spotted knapweed (C. maculosa). Even under good range conditions in British Columbia, bluebunch wheatgrass offered little resistance to knapweed invasion [5]. Clipping significantly reduces bluebunch wheatgrass' ability to grow with competition. In a study in Utah, plants were clipped at three levels: none, heavy (clipped once to 50% of weight on June 25), and extreme (a similar clipping, followed by a later clipping of all regrowth). When growing with competition, heavy clipping reduced following year production 38%, and extreme clipping reduced production by 75%. However, without competition, even the heavy clipping plots showed no significant reduction of following year productivity, leading the authors to conclude that in the absence of competition, bluebunch wheatgrass is able to recover from defoliation during the crucial growing time [183].

A study comparing germination rates of bluebunch wheatgrass and medusahead (Taeniatherum caput-medusae) concluded that medusahead germinates much more rapidly, especially at colder temperatures, and early season root growth is significantly greater. These characteristics contribute to the ability of medusahead to invade native bunchgrass communities by earlier seedling establishment in the growing season [114]. Cheatgrass and medusahead roots are able to grow at colder temperatures than bluebunch wheatgrass, and once they reach a thermally protected depth, they can continue to grow throughout the winter [131,132]. They may use all available soil moisture in the spring before the roots of bluebunch have begun to grow again [128,129,131]. Bluebunch wheatgrass generally needs temperatures of 39  Fahrenheit (4 °C) for root growth, although some ecotypes appear to grow very slowly at 36 °Fahrenheit (2 °C) and below [131]. In one study in Washington, bluebunch wheatgrass was able to penetrate only four inches (10 cm) before temperatures were too cold for root growth, while cheatgrass grew throughout the winter to a depth of three feet (.9 m) [130].

Roots of bluebunch wheatgrass have a heavy endodermis, a waxy layer that prevents desiccation in dry soil conditions. Cheatgrass roots do not have such a developed endodermis [130,131]; due to its annual life history, cheatgrass puts comparatively fewer resources into root development. This difference explains, in part, why cheatgrass does not easily invade undisturbed, established bluebunch wheatgrass communities.

Throughout the West, the introduced crested and desert wheatgrass species have overtaken much of the historical range of bluebunch wheatgrass. Some of the reasons for the loss of native bluebunch wheatgrass and the ascension of the introduced crested and desert wheatgrasses are related to some small but crucial ecophysiological differences. Following partial defoliation, desert wheatgrass rapidly grows a canopy with three to five times the photosynthetic surface of bluebunch wheatgrass. Also, desert wheatgrass invests less nitrogen per unit area of photosynthetic tissue and has great flexibility in its allocation of nitrogen and carbon resources. Desert wheatgrass takes advantage of soil gaps much better than bluebunch wheatgrass, especially during the winter [103]. Finally, desert wheatgrass can extract soil moisture from deeper underground than bluebunch wheatgrass [30].

One of the characteristics that contributes to the ability of crested wheatgrass to withstand grazing better than bluebunch wheatgrass is its ability to activate basal buds to produce new tiller growth, when apical meristems have been removed. Unlike bluebunch wheatgrass, crested wheatgrass grows these tillers quickly and curtails carbon allocation to root production, thereby increasing photosynthetic area and then restoring root:shoot balance [59,60,204].

Bluebunch wheatgrass seeds are susceptible to wireworm damage and the soil-borne pathogen Podosporiella verticillata [126].

Related categories for SPECIES: Pseudoroegneria spicata | Bluebunch Wheatgrass