• 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:

Rubber rabbitbrush is considered an important browse species on depleted rangelands [77]. In general, wildlife and livestock forage only lightly on this species during the summer, but winter use can be heavy in some locations [80]. Fall use is variable, but flowers are often used by wildlife and livestock. A few leaves and the more tender stems may also be used. The forage value of rubber rabbitbrush varies greatly among subspecies and ecotypes. Chrysothamnus nauseosus ssp. albicaulis, C. n. ssp. hololeucus, and C. n. ssp. salicifolius are preferred [78].

In Montana and Wyoming rubber rabbitbrush is considered to be an important fall and early winter food source for mule deer [33,73,100]. In north-central Montana, the percentage of rubber rabbitbrush in mule deer diets doubled from September to October, with highest use recorded in December [33]. Rubber rabbitbrush represents one of the single most important food items in winter mule deer diets in Wyoming, where it is used in summer and winter [100]. However, in parts of California it is considered only a minor mule deer food item even in winter [71]. Some elk use during September has been reported in the Missouri Breaks of Montana [73].

Pronghorn consume both flower tops and current-year leafage of rubber rabbitbrush [34]. In mixed shrub communities in Montana and Wyoming, they consume large amounts of rubber rabbitbrush during the fall. Pronghorn also use it in winter in some areas [2,9]. In parts of Saskatchewan, rubber rabbitbrush is a highly preferred pronghorn browse species during late fall [29].

In salt-desert communities of Utah, black-tailed jackrabbits graze the current year's growth of rubber rabbitbrush during dormancy [22]. In southern Idaho black-tailed jackrabbits exhibit a preference for forbs and shrubs, including rubber rabbitbrush, during August [37].

Rubber rabbitbrush is, in general, considered of little value to all classes of livestock although some subspecies receive at least light use by livestock during the winter months [123]. It is described as a "poor" forage species for domestic sheep in winter [59]. However, in parts of Utah, domestic sheep may utilize as much as 17% of the current year's growth [42]. Generalized importance ratings are as follows [15]:

     black-tailed deer - low         Rocky Mountain elk - moderate
     mule deer - moderate            moose - low
     white-tailed deer -low          caribou - low
     mountain goat - low              bighorn sheep - moderate
     Roosevelt elk - low

PALATABILITY:

Palatability of rubber rabbitbrush varies greatly according to subspecies. In general, the white or gray subspecies such as Chrysothamnus nauseosus ssp. salicifolius and C. n. ssp. albicaulis are more palatable to wildlife and livestock than are the green subspecies [99]. Generalized palatability ratings by subspecies are as follows [77,111]:

C. n. ssp. albicaulis - medium to high
C. n. ssp. consimilis - low
C. n. ssp. graveolens - low to medium
C. n. ssp. hololeucus - medium to high
C. n. ssp. salicifolius - medium to high

All subspecies are considered to be slightly toxic to livestock [30]. Rubber rabbitbrush fruit and flowers tend more palatable than other parts of the plant, and palatability of all subspecies is generally highest in fall and winter. New leaders may be preferred by some browsers [73]. Meyers and others [87] report that C. n. ssp. hololeucus and C. n. ssp. albicaulis are most palatable of the subspecies. Chrysothamnus nauseosus ssp. albicaulis remains palatable even during summer [111] and the entire aboveground plant of C. n. ssp. hololeucus is palatable [111]. The following tables summarize reported palatability ratings of rubber rabbitbrush subspecies by state.

C. n. ssp. albicaulis

                     CO        MT       ND        UT      WY
-------------------------------------------------------------
Cattle              ----      poor     ----      fair    fair
Sheep               ----      fair     ----      good    fair
Horses              ----      poor     ----      poor    fair
Pronghorn           ----      ----     ----      good    good
Elk                 ----      ----     ----      fair    good
Mule deer           ----      ----     ----      good    good
White-tailed deer   good      ----     ----      ----    ----
Small mammals       ----      ----     ----      good    good
Small nongame birds ----      ----     ----      good    fair
Upland game bird    ----      ----     ----      fair    fair
Waterfowl           ----      ----     ----      poor    poor

                      CO        MT       ND        UT        WY
---------------------------------------------------------------
Cattle              ----      ----     ----      poor      ----
Sheep               ----      ----     ----      poor      ----
Horses              ----      ----     ----      poor      ----
Pronghorn           ----      ----     ----      poor      good
Elk deer            ----      ----     ----      fair      good
Mule dule           ----      ----     ----      fair      good
White-tailed deer   good      ----     ----      ----      ----
Small mammals       ----      ----     ----      good      good
Small nongame birds ----      ----     ----      fair      fair
Upland game birds   ----      ----     ----      poor      fair
Waterfowl           ----      ----     ----      poor      poor

                     CO        MT       ND        UT        WY
---------------------------------------------------------------
Cattle              ----      ----     poor      poor      ----
Sheep               ----      ----     fair      poor      ----
Horses              ----      ----     fair      poor      ----
Pronghorn           ----      fair     good      fair      good
Elk                 ----      fair     ----      fair      good
Mule deer           ----      good     good      fair      good
White-tailed deer   good      ----     ----      ----      ----
Small mammals       ----      ----     ----      good      good
Small nongame birds ----      ----     ----      fair      fair
Upland game birds   ----      ----     ----      fair      fair
Waterfowl           ----      ----     ----      poor      poor

            			
C. n. ssp. nauseosus 

                     CO        MT       ND        UT        WY
---------------------------------------------------------------
Cattle              poor      poor     poor      poor      fair
Sheep               fair      fair     fair      good      fair
Horses              fair      poor     fair      poor      fair
Pronghorn           ----      fair     good      good      good
Elk                 ----      poor     ----      good      good
Mule deer           ----      good     fair      good      good
White-tailed deer   good      fair     ----      ----      ----
Small mammals       ----      ----     ----      good      good
Small nongame birds ----      ----     ----      fair      fair
Upland game birds   ----      ----     ----      fair      fair
Waterfowl           ----      ----     ----      poor      poor

NUTRITIONAL VALUE:

Rubber rabbitbrush has been rated "good" in energy and protein content [30]. Dry matter digestibility has been reported as 44.4% and crude protein content at 7.8% [25,140]. Nutritional value varies seasonally, with highest crude fat values noted in fall [120]. Crude protein levels also fluctuate seasonally. Protein value varied seasonally in 1964 as follows [131]:

                     01/2    2/5     3/1     4/2    11/30
% crude protein	     8.4%    8.0%    9.1%    8.2%   9%


Additional nutritional information is listed below [120]:

                summer    winter
crude fat       15-19%     ----
carotene        7 µg/g     ----
ash              ----      8.0%
P             0.09-0.11%   0.30%
K                0.80%     3.10%
Na               0.0169%   0.032%

COVER VALUE:

                       UT        CO        WY        MT      ND
-----------------------------------------------------------------
Elk                   poor      ----       poor      ----    ----
Mule deer             fair      ----       poor      ----    ----
White-tailed deer     ----      poor       ----      ----    ----
Pronghorn             fair      ----       fair      ----    ----
Upland game birds     fair      ----       good      ----    ----
Waterfowl             poor      ----       fair      ----    ----
Small nongame birds   good      ----       good      ----    ----
Small mammals         good      ----       good      ----    ----

                      UT         CO        WY        MT      ND
-----------------------------------------------------------------
Elk                   poor       ----      poor      poor    ----
Mule deer             fair       ----      fair      poor    good
White-tailed deer     fair       ----      fair      ----    ----
Pronghorn             fair       ----      fair      poor    good
Upland game birds     good       ----      good      ----    ----
Waterfowl             poor       ----      fair      ----    ----
Small nongame birds   good       ----      good      ----    poor
Small mammals         good       ----      good      ----    poor

                       UT         CO        WY         MT      ND
-----------------------------------------------------------------
Elk                   poor       ----      poor       ----    ----
Mule deer             fair       ----      poor       ----    ----
White-tailed deer     ----       poor      ----       ----    ----
Pronghorn             fair       ----      fair       ----    ----
Upland game birds     fair       ----      good       ----    ----
Waterfowl             fair       ----      fair       ----    ----
Small nongame birds   good       ----      good       ----    ----
Small mammals         good       ----      good       ----    ----

                      UT         CO        WY         MT      ND
-----------------------------------------------------------------
Elk                   poor       ----      poor       poor    ----
Mule deer             fair       ----      poor       poor    good
White-tailed deer     poor       ----      fair       ----    ----
Pronghorn             fair       ----      fair       poor    good
Upland game birds     fair       ----      good       ----    ----
Waterfowl             poor       ----      good       good    good
Small nongame birds   good       ----      good       ----    poor
Small mammals         good       ----      good       ----    poor

VALUE FOR REHABILITATION OF DISTURBED SITES:

Rubber rabbitbrush is excellent for soil stabilization and erosion control [26,60]. It is also well suited for use on degraded winter ranges [14,111]. Rubber rabbitbrush has a deep root system and can establish rapidly, even on severe sites [96]. Plants produce large quantities of leaf litter which produces soil mulch. On poor sites litter is important as a means of recycling nutrients to the soil surface from the deeper rooting profile. Rubber rabbitbrush has been planted in sagebrush grass, pinyon-juniper, northern desert shrub, southern desert shrub, and salt desert shrub communities [38,75,95].

Rubber rabbitbrush can be successfully seeded directly onto mined lands, including surface coal mine spoils [28,94]. It has also been successfully planted on disturbed areas such as along roadsides, where it frequently forms almost pure stands [138]. Chrysothamnus nauseosus ssp. albicaulis is considered one of the best shrubs for revegetating roadside cutbanks in the Sierra Nevada foothills [35].

When selecting accessions for rehabilitation, the relative palatability of the subspecies should be considered. On highly erosive soils, less palatable subspecies can be planted to discourage herbivory [95].

Seeds can be sown in spring or fall [117]. Initial establishment from seed is described as "good to fair" and early growth is generally rapid [77,123]. Seedlings are easy to establish, even on unprepared seedbeds [96]. Drill seeding, direct seeding, and aerial application have all been used effectively [28,77]. Transplanting container stock or nursery seedlings can also be effective [67,77]. Rubber rabbitbrush can be propagated by using stem cuttings [76,128,137]. Once established, it spreads easily by abundant, wind-disseminated achenes.

OTHER USES AND VALUES:

Rubber rabbitbrush was first tested as a source of good quality rubber during World War II [101]. In recent decades, there has been renewed interest in the potential of this species as a source of rubber and other chemicals [54]. Rubber content varies according to subspecies and environmental factors, with highest rubber production (6.67%) observed in Chrysothamnus nauseosus ssp. turbinatus [54]. Rubber content increases during periods of high temperatures and low soil moisture [53]. Chrysothamnus nauseosus ssp. consimilis has been found to produce the highest concentrations of resin (35.89%) [54].

Compounds present in rubber rabbitbrush are being tested for medical applications including use as a nematocide and for anti-malarial properties [138]. It is also a possible source of natural insect repellents [55]. Rubber rabbitbrush has been tested for suitability as a potential energy source from biomass. This shrub is known to grow in dense stands while maintaining relatively high individual plant biomass [132].

Rubber rabbitbrush has been cultivated since 1886 [27]. Certain subspecies have value for use as ornamentals [138]. Specific applications include urban plantings and parking strips [55,138]. The striking color of some of the white/gray subspecies and the ability to grow with little water makes them well suited for desert landscaping [137].

Some Native American peoples used rubber rabbitbrush latex as a source of chewing gum [101].

MANAGEMENT CONSIDERATIONS:

Rubber rabbitbrush can be susceptible to herbicides such as 2,4-D, but results vary widely according to type of treatment, rate of application, and date and year of treatment [8,143]. Relative effectiveness also depends on the amount of new twig growth and subsequent rainfall [92]. Highest kill rates are obtained when plants have at least 3 to 4 inches (7.6-10.2 cm) of new growth and when soil moisture exceeds 13% [8,27,143]. Rubber rabbitbrush may be less susceptible to herbicides during drought years when new growth may be minimal [92,112]. Plants may be more susceptible to 2,4-D after burning [112].

Various types of mechanical treatments have been tested for reducing or eliminating cover of rubber rabbitbrush. Because sprouting can occur after aboveground foliage has been removed, many types of mechanical treatments have limited utility. Areas that have been subjected to many types of mechanical disturbance often experience an increase in rubber rabbitbrush [48].

Mechanical treatments such as chaining and brush-beating are often ineffectual in reducing the cover of rubber rabbitbrush [17]. Plants may be killed by disking, but only if disks cut deeper than the ordinary 3 to 4 inches (8-10 cm) [102]. Plowing at depths below the root crown (greater than 5 to 7 inches (13-18 cm) may be effective, but often repeated treatments are necessary [102,103]. Cluff and Roundy [17] observed that only 17% of rubber rabbitbrush plants (Chrysothamnus nauseosus ssp. consimilis) were killed by rotobeating. Many plants resprouted vigorously the following year.

A leaf beetle, Trirhabda nitidicollis, may be at least moderately effective as a natural control agent of rubber rabbitbrush [23].

Clipping studies from eastern Oregon and Washington indicate greatest twig yields on heavily clipped plants (75% removal), with good production on moderately clipped plants [43,44]. Rosentreter and Jorgenson [111] noted good production when 73% of the annual growth was clipped during four consecutive autumns, although crown cover was reduced. A use level of 50% should allow rubber rabbitbrush to maintain good vigor [43,44].

Rubber rabbitbrush may dominate a site, but it tends to provide less competition to understory plants than do other shrub species such as sagebrush. Roots extend deeper in the soil than do those of perennial grasses and forbs. Because rubber rabbitbrush is deciduous, plants growing beneath the canopy of rabbitbrush receive sun during spring green-up and are protected by shading during the hot summer months. In addition, shrubs such as rubber rabbitbrush can function as windbreaks. During the winter, snow often accumulates around shrubs and provides added moisture in the spring for plants growing near the base. On favorable sites, herbage cover is greater where rabbitbrush is present [40]. Species such as crested wheatgrass (Agropyron cristatum) remain succulent and exhibit greater fall regrowth under rubber rabbitbrush [41].

Related categories for SPECIES: Chrysothamnus nauseosus | Rubber Rabbitbrush