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Wildlife, Animals, and Plants |
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VALUE AND USE
IMPORTANCE TO LIVESTOCK AND WILDLIFE:Shadscale is a valuable browse species [152], providing a source of palatable, nutritious forage for a wide variety of wildlife and livestock [19]. The fruits and leaves are a food source for deer [114,125], desert bighorn sheep [25], pronghorn [3,11,135], small rodents [119], jackrabbits [49,56,114], game birds, and songbirds [114]. Big game: Shadscale is good browse for mule deer [125], which feed upon shadscale during winter, spring, and fall in the Rocky Mountains [100]. Shadscale is a minor component of desert bighorn sheep diets [25]. Although it is not preferred [11,135], shadscale may provide winter forage for pronghorn [3]. Small mammals: Shadscale habitats of northeastern Nevada are important home ranges for small mammals. Chisel-toothed kangaroo rats feed on shadscale foliage and use shadscale habitats during the spring, summer, and fall. Deer mice use shadscale habitats all year [119]. Shadscale leaves and seeds are preferred forage for jackrabbits [49,56]. The Great Basin kangaroo rat also feeds on shadscale foliage [103]. Birds: The loss of shadscale and associated shrubs in southwestern Idaho has a negative effect on golden eagle habitat. Areas of shadscale shrub-steppe provide cover and forage for black-tailed jackrabbits, which are a major food source of golden eagles. Kochert and others [98] recommend maintaining shrub steppe within 1.9 miles (3.0 km) of golden eagle nests [125]. Several species of birds eat shadscale fruit [125]. Livestock: Shadscale provides good browse for domestic sheep [125,152] and goats [125]. Shadscale leaves and seeds are an important component of domestic sheep and cattle winter diets [19,45,70,142]. The spiny branches are unsuitable for cattle [19]. Shadscale is an important forage for domestic sheep on winter ranges of the Great Basin. Greatest use was observed before seed dissemination, after which use declined except when other forage was covered with snow [71]. In the Mojave Desert shadscale is moderately preferred by domestic sheep, which use it early in the grazing season [124]. The spinescence of shadscale allows for no more than 15 to 20% use of previous herbage growth by domestic sheep [81].
PALATABILITY:Shadscale is palatable to all domestic grazing animals [114]. Seeds are the most palatable part of shadscale. During moist weather branches are softened, increasing palatability [157]. Shadscale palatability is summarized below by state [51]:
NUTRITIONAL VALUE:Shadscale provides 50 and 55% of winter range requirements for phosphorus and energy, respectively [46]. Average chemical composition of shadscale during winter in desert ranges of Intermountain Region was [45]:
Average digestibility of the chemical constituents, digestible protein, and metabolizable energy of shadscale during winter in desert ranges was [45]:
COVER VALUE:Within shrub steppe of southwestern Idaho, shadscale provides cover for sage sparrows, Brewer's sparrows, sage thrashers, and western meadowlarks [97]. In the Great Basin it provides cover for rodents and small game [55]. Overall cover value has been rated as follows [51,101]:
VALUE FOR REHABILITATION OF DISTURBED SITES:Revegetation of shadscale communities is inherently difficult [21,161]. Dry soil surfaces resulting from low humidity, high irradiation, and moderate to strong winds are major obstacles in revegetation projects [21]. The extensive polyploidy of shadscale is an important consideration when implementing revegetation projects [36,129] because ploidy levels are usually associated with distinct habitats. Diploid individuals are unlikely to perform as well in areas where tetraploids are more common. Diploid individuals generally occur above Pleistocene lake levels, whereas lake floors are usually occupied by autotetraploids. Octoploids generally occur at lower bottoms. Overall, tetraploids are the most widespread throughout its range [36]. Shadscale ploidy level may be determined through pyrolysis-gas chromatographic fingerprinting [137]. Sanderson and others [128] provide a list of ploidy levels for shadscale individuals inhabiting specific localities within Arizona, California, Colorado, Idaho, New Mexico, Nevada, Oregon, Utah, and Wyoming, along with comparisons of morphology. Seeding: Due to the complex mechanisms behind shadscale seed dormancy, revegetation through seed is usually unsuccessful [55,63,111,161]. Garvin and others [66] document difficulty in breaking seed dormancy. Results from a comprehensive review of literature suggest a staggered germination pattern resulting in increased probability of survival under specific germination conditions. However, dormancy mechanisms controlling germination patterns are still unknown to an "agronomic" level of predictability. Dumas and Sanders [55] found mechanical scarification increased germination by 15% within growth chambers. Garvin and others [66] provide recommendations to improve artificial regeneration on rangelands:
Hall and Anderson [72] were successful revegetating disturbed areas of Nellis Air Force Range, Nevada with seeded shadscale. Seeding resulted in 1 plant/m2 after 2 years. Cuttings/seed grown transplants:Establishment of shadscale from container stock provides the highest probability for successful revegetation [41,48]. Cuttings from juvenile plants readily propagate [156]. Crofts and Van Epps [48] recommend taking cuttings in fall or early spring and placing in a medium with good aeration. Richardson and others [127] found no difference in the rooting ability of stems cut from different sexes. Stem cuttings treated with 0.3 indolebutyric acid (IBA) talc powder [86,127] resulted in the highest production of adventitious roots. Higher concentrations of IBA slightly reduced the overall percentage of stem cuttings with adventitious roots but had no negative effect on root development after initiation [127]. High humidity must be maintained during propagation. The rooting medium should allow for good aeration and drainage and still maintain relatively high water-holding capacity [86]. Shadscale establishes well from transplants when put out in the early spring, after 6 weeks of high soil moisture [20]. McKell [107] has shown success revegetating with container grown shadscale transplants. Seed-grown stock is available commercially [7].
OTHER USES AND VALUES:Historically, shadscale was a food source for native Americans of the southwestern United States [37]. Seeds were used by native Americans of Arizona, Utah and Nevada for bread and mush [57].
MANAGEMENT CONSIDERATIONS:Extensive shadscale die-off occurred within the Great Basin from 1977 to 1986, during a historically high period of precipitation. Greatest die-off was from 1983 to 1985. Areas of severe die-off were most often within valley bottoms or upland depressions where prolonged periods of high soil moisture occurred [117]. Several theories for causative agents have been presented [116,117,151]. Prolonged periods of high soil moisture are believed to increase shadscale's susceptibility to parasites and disease [151]. Shadscale is very susceptible to water mold, root rot, and vascular wilt fungi [117]. Mealy bugs and scale insects found in the crown and upper root zone of shadscale may also lead to high mortality [116]. Weber and others [151] found high soil conductivity and moisture significantly (p<0.05) correlated with shadscale die-off. This, in conjunction with genetically uniform populations within the Pleistocene lake bottoms of the Great Basin, lends to large-scale disease outbreak. Walser and others [150] evaluated cold hardiness of shadscale between December and March. Observations suggest that -67 degrees Fahrenheit (-55 °C) in December and -53 degrees Fahrenheit (-47 °C) in March are sufficient to damage plants so that upcoming summer stress results in high mortality. If a cold spell is preceded by temperatures greater than freezing, the cold tolerance of shadscale is greatly reduced. Pocket gophers may kill shadscale by severing the stem while feeding on roots [21]. Grazing: In shadscale communities of the Great Basin, grazing pressure has increased the overall presence of exotic annuals such as cheatgrass, halogeton, and Russian-thistle (Salsola kali). However, Harper and others [75] observed grazed shadscale communities suppressed growth of exotic annuals. At the present time, the ability to indefinitely suppress of exotic annuals through close management is still under question. The spinescent habit of shadscale lends to its browsing tolerance [19,85]. Increased presence of shadscale within grazed versus ungrazed areas is generally a result of the decreased competition from more heavily browsed associates [19,39,81]. Reduced competition from more palatable species in heavily grazed areas may increase shadscale germination and establishment. Chambers and Norton [38] found shadscale establishment higher under spring than winter browsing as well as heavy compared to light browsing (p<0.01). Within the northern Great Plains (Montana), shadscale is most tolerant of intermediate livestock stocking rates [82]. Hutchings [84] recommends 25% use of annual shadscale growth within winter ranges of Utah, Nevada, southern Idaho, and southwest Wyoming. Cook and Child [44] found shadscale was most tolerant of light (30% overall herbage removal) winter browsing. Heavy (90% herbage removal) grazing during spring and/or winter reduces shadscale. Shadscale is also tolerant of early spring (1 April) light-intensity browsing. During years of below average precipitation, shadscale is very susceptible to grazing pressure regardless of season (grazing × season × intensity interaction effects, p<0.05) in Desert Experimental Range, Utah [38].
Related categories for SPECIES: Atriplex confertifolia | Shadscale |
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