| | |
 |
|
| 
| ||
 |
|
|
|
 |
|
Wildlife, Animals, and Plants |
|
|||
|
VALUE AND USE
IMPORTANCE TO LIVESTOCK AND WILDLIFE:Blackbrush is not preferred as forage by domestic livestock, deer, or pronghorn, but it does provide poor forage during the spring, summer, and fall for domestic cattle, horses, and domestic sheep [8,19,41,50,90,112,124]. Blackbrush provides poor to good forage for domestic goats [41,84,90]. Mule deer and bighorn sheep generally use the blackbrush vegetation type in winter, and livestock generally use it in winter and spring [17,98,112,124]. The principal forage value of blackbrush appears to be as a browse species for bighorn sheep [17,18,68]; blackbrush communities also provide important habitat for desert bighorn sheep in Nevada [18]. Domestic sheep and goats, and to a lesser extent, cattle browse blackbrush [47,70,118,124]. It provides fair forage for domestic sheep and cattle in the winter in southwestern Utah [17,41], but spiny stems coupled with chemical compounds in current year's growth protect blackbrush from heavy browsing by livestock [6,79,80]. Due to the spinescent growth form of blackbrush, the low amounts of current-season growth are of limited accessibility to most browsing animals [79,112]. Carrying capacities on blackbrush ranges are low, from 30 to 300 acres/AUM [8,124]. Blackbrush often occurs as nearly monospecific stands, with few other forage species available [112]. Though it is not desirable deer forage, in areas where it is extensive it may experience heavy browsing pressure [8,68]. Where it forms an appreciable proportion of the brush cover, it provides a substantial part of the diet of domestic sheep and goats and deer, despite its small leaves and spinescent growth [17]. In California, blackbrush has comprised up to 25% of the mule deer winter diet [52]. Blackbrush-dominated sites where animals congregate may provide inadequate nutrition and impede the regeneration of bitterbrush, a key browse species [8]. The presence of blackbrush in Arizona chaparral may reduce the range quality rating due to its low forage value and exclusion of higher forage value plants [41]. Greater resistance to grazing probably allows blackbrush to persist and perhaps expand after the more palatable species are removed [8]. Small mammals and birds consume blackbrush seeds [68,74,98,124].
PALATABILITY:The spinescent character of blackbrush combined with low phosphorus and protein levels and high tannin levels result in low palatability [8,80]. New growth is likely more palatable and nutritious than old spinescent branches [17], but regrowth of blackbrush has been found to be unpalatable to domestic goats and cattle [124].
NUTRITIONAL VALUE:Blackbrush is low in phosphorus and protein and high in poorly digestible fiber [8,79,84,85]. Low nitrogen levels suppress microbial activity in the rumen, thereby decreasing fiber digestibility and lowering forage intake. High tannin levels, also typical of blackbrush, may depress intake by decreasing palatability and suppressing protein digestion [80]. Domestic goats have been found to avoid blackbrush current-season growth in favor of older growth, even though new growth is higher in nitrogen and is more digestible. Current-season growth is high in concentrated tannins, which may deter browsing because tannins interfere with digestive or metabolic processes [81]. Twig nutrition varies by location on the plant; twigs
from basal branches, located within the canopy, are higher in crude protein and
in-vitro digestible matter than those on older, terminal branches, located at
the outer edges of the canopy [79,82,86]. Blackbrush nutrition has been evaluated according to plant part
[16,17,118]: the following table compares
the nutritional content of leaves and stems [16,17]:
Blackbrush leaves and stems exceed the minimum carotene required for gestating and lactating domestic animals but are deficient in phosphorus for domestic cattle and sheep during gestation and lactation [16,17]. Ether extract is comparable to that of big sagebrush and black sagebrush (Artemisia nova) during the winter [16,17].
COVER VALUE:Blackbrush provides cover for nongame birds and small mammals [22]. In southern Nevada, blackbrush communities with an understory including big galleta are preferred cover for desert bighorn sheep [110].
VALUE FOR REHABILITATION OF DISTURBED SITES:Blackbrush contributes to desert fertility by 1) protecting the soil against wind erosion through retarding the movement of soil and increasing the accumulation of fine soil particles around its base; 2) protecting understory vegetation from the effects of high temperatures, thereby helping to retain surface nitrogen and adding organic matter to the soil; and 3) serving as a nitrogen reservoir through the storage of nitrogen in roots, leaves, and stems [16]. Blackbrush displays no natural vegetative reproduction [64], but regeneration can be achieved with asexual propagation from artificial cuttings. One-year growth has been found to produce a higher percentage of rooted cuttings, more roots, and longer roots than older growth [40].
OTHER USES AND VALUES:No entry
MANAGEMENT CONSIDERATIONS:Dayton [27] considers blackbrush "almost worthless" forage. Nevertheless, blackbrush areas are economically important for winter grazing by domestic livestock, especially sheep, and by wild ungulates, primarily mule deer and desert bighorn sheep [45]. Blackbrush is a native plant species resistant to trampling and recreation impacts [25]. Solid stands of blackbrush may result in areas where overgrazing has removed the perennial grasses and palatable shrubs [16,17]. Blackbrush tolerates heavy browsing but survives at much reduced cover, and areas of blackbrush communities that have not been grazed have substantially more herbaceous vegetation than recovering, lightly, moderately, or heavily grazed sites [45,47,118,127]. A thriving blackbrush/desert needlegrass community exists at the Nevada Test Site, where grazing had been excluded. In adjacent areas that have been subject to grazing, the desert needlegrass component was virtually nonexistent [108]. Removal of spinescent material from blackbrush plants stimulates sprouting from basal and axillary buds; therefore, plants that are heavily browsed by livestock produce large quantities of new, more accessible growth [79,80,85,112]. Browsing improves nutritional quality of blackbrush twigs by increasing current-season growth; however, browsing may decrease palatability due to high tannin levels in current-season growth [86]. Nutritional value varies in response to browsing treatments: low protein and high tannin content persists, though current-season growth generally has increased protein [80]. Heavy browsing followed by 1 to 2 years of rest allows blackbrush to accumulate twigs that are more palatable because they are lower in tannins due to lower proportions of current-season growth [80,84,85,86]. Domestic goats can be used to remove spinescent growth and increase production of current-season growth to improve forage for cattle; however, the low crude protein levels may cause a reduction in livestock weight [83,112]. Livestock browsing on blackbrush should be supplemented with protein to improve rumen function and minimize weight loss [80,84,85]. With intensive management, stocking intensities of 1.8 AUM/ha can be maintained [80]. Blackbrush can produce substantially larger amounts of current growth with somewhat greater palatability and nutritional value through the use of mechanical or browsing treatments [112]. Prescribed burning can lead to replacement by other shrubs, diversifying plant communities and increasing the winter forage base, which may increase livestock carrying capacity [8,112]. Because blackbrush exhibits strong apical dominance that suppresses annual twig growth, removal of terminal buds during the dormant winter season stimulates lateral twig growth during the spring [81,82]. Brush beating damages plants and stimulates growth of new shoots, improving forage quality [17]. The results of a simulated brush beating in different plant communities 1 year after treatment are presented below. Blackbrush plants in the blackbrush association responded better to the brush beating treatments than blackbrush plants in either the Joshua tree/blackbrush or Utah juniper/blackbrush associations. The number of blackbrush plants (out of 30 at each location) is presented according to the response to brush-beating treatment and the plant community in which the blackbrush occurred [16]:
Efforts to manipulate blackbrush rangelands to increase forage production have produced unanticipated results [6]. Blackbrush stands might be manipulated for improvement of forage quality and quantity without destroying the original vegetation; however, the manipulation may open the plant community to the invasion of other, perhaps less desirable, species [17].
Related categories for SPECIES: Coleogyne ramosissima | Blackbrush |
 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 | |
| |
| |
| Content on this web site is provided for informational purposes only. We accept no responsibility for any loss, injury or inconvenience sustained by any person resulting from information published on this site. We encourage you to verify any critical information with the relevant authorities. | |
| |
|
About Us | Contact Us | Terms of Use | Privacy | Links Directory |
| 1Up Info All Rights reserved. Site best viewed in 800 x 600 resolution. |
