SPECIES: Atriplex lentiformis
|Michael Charters, Southern California Wildflowers|
Big saltbrush may not regularly hybridize, even though it occurs with several Atriplex species . However, Hanson  reports hybrids of quailbush and beach saltbush (A. leucophylla) and quailbush and Davidson's bractscale (A. serenana var. davidsonii) in the collections of the California Academy of Sciences.LIFE FORM:
SPECIES: Atriplex lentiformis
|Quailbush. Tony Baker, Natural Landscapes|
Riparian zones in which big saltbrush occurs include woodlands such as cottonwood-willow (Populus-Salix spp.) and mesquite (Prosopis spp.) cover types, as well as riparian scrub. Big saltbrush also grows on the margins of oases and wetlands. In cottonwood-willow woodlands big saltbrush typically occurs with low frequency [16,49,93]. According to vegetation classifications based on literature and expert opinion [49,93], more common riparian species such as mule's fat (Baccharis salicifolia), common reed (Phragmites australis), sandbar willow (S. exigua), and Fremont cottonwood (Populus fremontii) occur with big saltbrush in riparian areas across big saltbrush's range. Goodding willow (S. gooddingii) is another component of these communities, although it is less common in southern California coastal areas and absent from California's central coast [93,109]. Big saltbrush is an uncommon species in the riparian areas of California's Central Valley and central and southern coastal regions, which typically contain California sycamore (Platanus racemosa), red willow (S. laevigata), Pacific willow (S. lucida ssp. lasiandra), arroyo willow (S. lasiolepis), Douglas' mugwort (Artemisia douglasiana), and common elderberry (Sambucus nigra ssp. canadensis) . On the Mojave River big saltbrush may occur with velvet ash (Fraxinus velutina), white alder (Alnus rhombifolia), and riparian species common throughout its range . Giant reed (Arundo donax) and tamarisks (Tamarix spp.) also co-occur with big saltbrush in riparian zones throughout much of big saltbrush's range [49,93].
Riparian scrub forms thickets along rivers and streams of the Southwest, which are typically dominated by tamarisks and arrowweed (Pluchea sericea) [15,17,63]. In addition to these dominants, some communities may contain scattered Fremont cottonwood and willows, as well as big saltbrush, screwbean mesquite (Prosopis pubescens), honey mesquite (P. glandulosa), saltgrass, Palmer's coldenia (Tiquilia palmeri), mule's fat, and/or spiny chloracantha (Chloracantha spinosa) [15,16,17,49,63,71,106]. Mojave seablite, cattle saltbush, and iodinebush (Allenrolfea occidentalis) can also be components of this vegetation type .
Further from the river channel is the mesquite bosque forest. Big saltbrush is a typical species of the mesquite bosque understory . Presettlement mesquite bosque forests had relatively open understories with grasses, forbs and saltbushes, such as big saltbrush and cattle saltbush (Atriplex polycarpa) forming the ground cover [14,49,71]. These communities can contain honey mesquite, velvet mesquite (P. velutina), and/or screwbean mesquite as well as Mojave seablite (Suaeda moquinii), viney milkweeds (Sarcostemma spp.), gourds (Cucurbita spp.), netleaf hackberry (Celtis reticulata), common elderberry, blue paloverde (Parkinsonia floridum), wolfberries (Lycium spp.), and saltbushes including big saltbrush, cattle saltbush, and fourwing saltbush (A. canescens) [49,71,93].
Big saltbrush occurs on the margins of oases, wetlands, and in alkali sink communities. Vogl and McHargue  report big saltbrush as a rare species within the oases along the San Andreas Fault. Typical species within southern Californian oases include California palm (Washingtonia filifera), blue paloverde, mule's fat, desert willow (Chilopsis linearis), common reed, arrowweed, mesquite (Prosopis spp.), screwbean mesquite, sandbar willow, Goodding willow, and desert wild grape (Vitis girdiana). [93,114]. Along the margins of Sonoran wetlands, species from surrounding scrublands including tamarisk (Tamarix spp.), arrowweed, mesquite, and big saltbrush mix with species more typical of wetlands, such as common cattail (Typha latifolia), saltgrass (Distichlis spicata), common threesquare (Schoenoplectus pungens), and common reed . Big saltbrush may be one of several saltbrush species found in alkali sinks of the desert Southwest along with iodinebush and Mojave seablite . According to a literature review by Thorne , several other Chenopods occur in this community including goosefoot species (Chenopodium spp.), pickleweeds (Salicornia spp.), seepweeds (Suaeda spp.), and black greasewood (Sarcobatus vermiculatus). Other species found in alkali sinks include fewleaf spiderflower (Cleome sparsifolia), stinkweed (Cleomella spp), spreading alkaliweed (Cressa truxillensis), alkali pepperweed (Lepidium dictyotum), spiny caper (Oxystylis lutea), and spectacle fruit (Wislizenia refracta) .
Big saltbrush also inhabits comparatively dry habitats such as grasslands and desert scrub, including saltbush vegetation. Other saltbushes are the dominant species in this type, with big saltbrush a relatively common associate [43,63,85,106,108,112]. Cattle saltbush and thinleaf fourwing saltbush (A. canescens var. linearis) are frequently dominants of this type [63,107]. Several saltbushes are associated with this community, including big saltbrush, silverscale saltbush (A. argentea), fourwing saltbush, shadscale (A. confertifolia), wheelscale saltbush (A. elegans var. fasciculata), Nuttall's saltbush (A. nuttallii), Parry's saltbush (A. parryi), leafcover saltweed (A. phyllostegia), smooth saltbush (A. pusilla), and Torrey's saltbush (A. torreyi) . In addition, fivehorn smotherweed (Bassia hyssopifolia), iodinebush, boraxweed (Nitrophila occidentalis), Parish's pickleweed (Arthrocnemum subterminale), seepweeds, and saltgrass can occur in this community . Other species in this type are shrubby alkaliaster (Machaeranthera carnosa var. intricata), spiny hopsage (Grayia spinosa), white burrobrush (Hymenoclea salsola), rusty molly (Kochia californica), Anderson wolfberry (Lycium andersonii), peach thorn (L. cooperi), western honey mesquite (Prosopis glandulosa var. torreyana), and Pursh seepweed (Suaeda calceoliformis) . Vasek and Barbour  report big saltbrush as an important species in the salt scrub vegetation of Rabbit Dry Lake in California along with green molly (Kochia americana), Mojave seablite, and shadscale saltbush. Gullion  mapped the distribution of a Las Vegas Valley saltbush type that was comprised of saltbushes including big saltbrush and Mojave seablite, saltgrass, and globemallow (Sphaeralcea spp.).
Big saltbrush also occurs in other desert scrub types. Although rare in the oases studied by Vogl and McHargue , big saltbrush was one of many species, including catclaw acacia (Acacia greggii) and Schott's pygmycedar (Peucephyllum schottii), that were part of the surrounding desert community. Saltbushes can occur in mixed woody scrub, Joshua tree (Yucca brevifolia) woodland, and creosote bush (Larrea tridentata) scrub [49,105,106]. Confirmation of big saltbrush in these communities is not provided by the literature. Big saltbrush has been reported as a codominant with coyote bush (Baccharis pilularis) on upland sites , and as the dominant species in an area with fourwing saltbush .
There are few reports of big saltbrush occurring in grasslands. However, Munz  includes valley grassland in a list of communities that contain quailbush. In addition, Heady  notes the need for more research of the saltbush variations of valley grasslands. He notes the occurrence of cattle saltbush on foothills and other drained areas that border sinks. Other alkali-tolerant associated species include iodinebush, rusty molly, Parish's pickleweed, seablite and grasses including saltgrass, dwarf barley (Hordeum depressum), and alkali sacaton (Sporobolus airoides). It is likely that big saltbrush is an uncommon associate in these or similar areas.
Big saltbrush, typically quailbush, occurs in coastal sage scrub [4,10,25]. In coastal regions near the mouth of the Ventura River, big saltbrush and coyote bush occur amongst other scattered dune vegetation dominated by sand verbena (Abronia spp.) and silver burr ragweed (Ambrosia chamissonis). Other species characteristic of this vegetation type are beach suncup (Camissonia cheiranthifolia ssp. suffruticosa), California croton (Croton californicus), saltgrass, seaside buckwheat (Eriogonum latifolium), and chamisso bush lupine (Lupinus chamissonis) . Pearcy and Harrison  studied big saltbrush in a coastal area where it occurred with saline saltbush (Atriplex subspicata), California seablite (Suaeda californica), California sagebrush (Artemisia californica), and saltgrass.When big saltbrush is included in classification schemes it is typically as an associated species, not a dominant or indicator species.
|Quailbush. Ken Gilliland, Thomas Payne Foundation|
Big saltbrush is a large, perennial, native shrub. It typically grows to between 3.3 and 8.2 feet (1-2.5 m) tall, but can reach 9.8 feet (3 m) [8,57,79,90,119]. Plants are wide spreading [25,113]. Individuals approximately 6.6 feet (2 m) tall were reported to cover areas ranging from 5.6 m² to 7.8 m² , and some plants reach coverages of up to 10 m² . Big saltbrush is typically evergreen, but can be drought deciduous in some desert environments [25,28,113,119]. The numerous leaves of big saltbrush are somewhat thick, about 0.4 to 2 inches (1-5 cm) long, 0.25 to 1.5 inches (0.3-4 cm) wide, and covered in fine scales [8,25,113,119]. Big saltbrush branches are numerous and slender. The bark is typically covered in fine scales when young and becomes rough on old trunks . The small, imperfect flowers occur in panicles [25,74,119]. The fruits are utricles with bracts typically 0.1 to 0.15 inch (3-4 mm) long and wide, which contain a seed 0.04 to 0.06 inch (1-1.5 mm) wide [8,69,119].
Breeding system: Big saltbrush can be either monoecious or dioecious [113,119,123]. In plantings done to determine potential of big saltbrush as a forage crop the sex ratio was 60% male plants, 10% female plants, and 30% monoecious plants . In their 1984 article, Freeman and others  included data from previous research demonstrating change of sex in big saltbrush. Plants typically change from dioecious to monoecious, but can also change from female to male. The ability to change sex appeared to enhance survival and may provide a reproductive advantage to the population. The table below shows the number of individuals from a wild population of 70 that exhibited each type of change in sex between 1978 and 1983 .
|Type of Change in Sexual Morphology||Number of individuals|
|Female to male or female to monoecious to male||9|
|Female to monoecious||9|
|Male to monoecious||5|
Pollination: According to Meyer  saltbush species are wind pollinated, but evidence demonstrating this for big saltbrush is lacking. Saltbush sootywing butterflies feed on big saltbrush nectar . Whether they or other insects transfer pollen while feeding is not reported.
Seed production: Big saltbrush has been reported to produce an abundance of seeds , but quantitative data illustrating this are not available.
Seed dispersal: Ohmart and Anderson  note that seed dispersal occurs mainly by water and vertebrates. Several species, including ring-necked pheasants and Gambel's quail, are known to eat big saltbrush seeds [25,44], but there is no research addressing bird dispersal of big saltbrush seeds.
Germination: In laboratory studies, big saltbrush germination rates have varied. Watson and others  obtained average germination rates of 7% one year and 57% the following from four replicates of 25 seeds incubated on a 68/100 °F (20/40 °C) diurnal temperature regime. Seeds were collected in the fall and winter of both years. In low salinity treatments Jackson and others  found 21% to 24% mean germination rates of seeds with utricles removed, and Young and others  report a mean germination rate of 39% to 40% over 55 different temperature treatments ranging between 32 °F and 104 °F (0° and 40 °C). Malcolm and others obtained high germination rates, above 80%, with big saltbrush seeds that had their utricles removed .
Thorough studies on the effect of temperature on big saltbrush germination have been performed. Young and others  investigated the effects of 55 different alternating and constant temperature regimes on big saltbrush germination. They obtained the best germination rates, between 65% and 68%, when the 8-hour warm period temperature was between 68 °F and 86 °F (20° and 30 °C) and the 16-hour cold period temperature was between 41 °F and 59 °F (5° and15 °C). No germination occurred when warm and/or cold period temperatures were below 41 °F (5 °C). When both were 41 °F (5 °C) the mean germination rate was 5%. The only other temperature regimes that resulted in no germination were at warm-period temperatures of 104 °F (40 °C) when the cold-period temperature was 95 °F (35 °C) or higher. Mean germination was 6% when both warm and cold period temperatures were 95 °F (35 °C). All other temperatures resulted in germination greater than 20%. Results are from 4 replications of 100 seeds each . Young and others  did not find a significant effect (p>0.01) of light on big saltbrush germination. Mikhiel and others  found the highest germination rate with a treatment in which seeds were exposed to 50 °F (10 °C) and 68 °F (20 °C) each for 12 hours per day. The germination rates for the 3 treatments are shown in the table below .
|5° and 15 °C||10° and 20 °C||20° and 30 °C|
In addition to temperature, salinity has a strong influence on germination rates. Jackson and others  observed no big saltbrush germination in salinity treatments of 18,000 mg/L and higher. At salinity levels of 6,000 mg/L and lower, mean big saltbrush germination rates were between 21% and 24%. The table below shows the germination rates of big saltbrush subject to 4 salinity treatments .
|control||~12 dS/m||~24 dS/m||~36 dS/m|
Differences between the control and the 3 salinity treatments were significant (p<0.05), while the differences between salinity treatments were not statistically significant. The germination rate at the ~24 dS/m salinity level was significantly (p<0.05) higher than other saltbushes tested, including cattle saltbush and fourwing saltbush . Mikhiel and others  also determined germination rates for big saltbrush at 4 salinity levels; their results are shown in the table below. Unlike many other species investigated, big saltbrush does not exhibit a significant synergistic effect of temperature and salinity .
|0.0 M||0.05 M||0.20 M||0.40 M|
In the field, estimates for germination rates are from rehabilitation plantings. For example, in a review of several revegetation projects, Biggs and Cornelius  report that germination of big saltbrush on the Cibola National Wildlife Refuge in Arizona was initially high, with over 1,000 seedlings produced on four 19.7-foot × 29.5-foot (6- × 9-m) plots. Anderson and others’s  first attempt at establishing big saltbrush on the lower Colorado River, by broadcast seeding, was almost entirely unsuccessful. The table below shows big saltbrush percent germination per meter of seeds planted in loam in watered areas along the lower Colorado River in their third attempt to establish big saltbrush. The number of meters sampled per site is shown in parentheses .
|Site 1||Site 2||Site 3|
|Nov. 6||9.4 (35)||2.8 (36)||9.9 (20)|
|Mar. 6||5.6 (31)||4.0 (64)||6.8 (11)|
Seedling establishment/growth: Big saltbrush can successfully establish on many types of sites [3,13,30,41,60,80]. After 1 growing season in the northern portions of the Crescent Bypass riparian revegetation area, about 34 miles (56 km) south of Fresno, California, most big saltbrush had grown quickly and survival was 88% . In a review of revegetation projects, Briggs and Cornelius  report that some big saltbrush grew to over 3 feet (1 m) and were producing seed after 3 growing seasons at Mittry Lake in Arizona. In rehabilitation plantings in western Australia, big saltbrush had relatively high establishment compared to several other saltbush species and reached 14.6 inches (37 cm) tall and 40.6 inches (103 cm) diameter after 2 years' growth . Three years following planting of quailbush in San Onofre State Beach, California, coverages reached 11.9% on a site that had been hydroseeded and 13.8% on a site that had been broadcast seeded and raked .
Despite the ability of big saltbrush to tolerate drought, establishment and survival are probably improved with greater availability of water. Young big saltbrush plants have been reported to be more susceptible to drought (Anderson and Ohmart, personal communication in ). Goodin and McKell  noted a lack of regeneration when subject to only 3.9 inches (100 mm) mean precipitation and speculated that the dry conditions were interfering with seedling establishment. Big saltbrush growth to 6 feet (1.8 m) in height and diameter within a year was documented in plantings done near the Fresno Slough from 1959 to 1960 . Given the short distance to the slough, the water table was likely shallow and plants were also irrigated during the summer months. In addition, Watson and others  found a general trend toward larger numbers of big saltbrush establishing closer to the irrigation source. In 1992, they found 5 big saltbrush established per linear meter when 1.5 meters from the irrigation source; this decreased with distance from the irrigation source. In 1993, a drier year, less than 1 big saltbrush established per linear meter when 1.5 meters from the irrigation source. Again establishment decreased as distance from the irrigation source increased, although at a lower rate than observed in 1992 . For more general information, see the Water section below.
High levels of salinity appear to affect seedling development. Jackson and others  reported no effect of salinity on the growth of big saltbrush seedlings at salinity levels of 18,000 mg/L and lower. However at 36,000 mg/L and 60,000 mg/L, shoot biomass was significantly (p<0.05) less than the 6,000 mg/L and 18,000 mg/L treatments. The total stem growth over 120 days was also significantly less (p<0.05) at 36,000 mg/L and 60,000 mg/L salinity levels compared to less saline treatments. The effects of the higher salt concentrations became larger over time. However, none of these salinity treatments resulted in seedling mortality . In addition, Malcolm and others  found increased cotyledon width and more rapid formation of true leaves in delayed salinity treatments, where big saltbrush seeds were subject to a period of low salinity (160 mS/m) before salinities were increased (1900 mS/m).
Asexual regeneration: There have been no reports of big saltbrush reproducing asexually in the wild.SITE CHARACTERISTICS:
|Arizona||< 4,000 feet (1,220 m) |
|California||< 2,000 feet (610 m) [25,74]|
|Utah||2,500 to 3,120 feet (760-950 m) |
|Mexico||0 to 4,000 feet (0-1,220 m) |
Temperature: The optimal temperatures for big saltbrush depend on the location of the populations sampled. It has been demonstrated that for big saltbrush in coastal areas, temperatures below 97 °F (36 °C) result in higher CO2 uptake than big saltbrush in desert areas. However, above 97 °F (36 °C) big saltbrush in desert areas have more efficient CO2 uptake. Photosynthesis is most efficient at 111 °F (44 °C) . Big saltbrush in desert areas have been shown to have a greater capacity to acclimate to high temperatures . For effects of temperature on germination see Germination.
Soil: Big saltbrush is typically found in moist to dry alkaline or saline soils [37,57,90,111], and has low tolerance for acidity . The range of pH and electrical conductivity found on 3 sites, one in southwestern Utah and two in Nevada, containing big saltbrush are shown in the table below .
|pH||Electrical Conductivity (mmhox/cm)|
Values of pH and electrical conductivity measured on sites near Safford, Arizona, where big saltbrush was grown to test its use as a forage crop, are shown in the table below .
|Sample||Date||pH||Electrical Conductivity (dS/m)|
|Pre-irrigation||Mar. 1984||7.5||1.3 (s=0.3)|
|Furrow top||June 1984||7.3||68.2 (s=20.2)|
|Furrow bottom||June 1984||7.6||48.7 (s=24.1)|
|Post-irrigation||Jan. 1985||7.9||9.6 (s=6.7)|
Big saltbrush occurs in a variety of soil textures from quite coarse soils, especially in the case of the quailbush, which can grow in pure sand  to silty loams and silty clay loams . Big saltbrush was established in an area of revegetation with sandy loams . Turner and Brown  note the occurrence of the saltbush series, a community type containing big saltbrush, in areas with soil textures that are generally finer than sandy loams. Marks  reports saltbush communities typically growing in soils with intermediate textures, such as silty loams to silty clay loams. Soils with poor aeration can result in severe growth limitations in big saltbrush . Soil texture has not been shown to have a significant (p>0.05) effect on germination . See the Germination and Seedling establishment/growth sections for more information on factors affecting big saltbrush in these stages.
Water: Big saltbrush may grow in areas with or without an accessible water table [37,41,57,66]. In California, Pearcy and Harrison  found moist soil at depths between 7.9 to 15.8 inches (20-40 cm) on a desert and a coastal site containing big saltbrush. In an experiment investigating water use of several species, big saltbrush was grown in tanks with an experimentally set water table depth of between 3.3 and 5.5 feet (1-1.7 m) . According to McDonald and Hughes  big saltbrush has been found on sites with deep water tables. These plants are likely to survive on surface sources of soil moisture and be less vigorous than specimens that occur in areas with a shallow water table.
Big saltbrush can tolerate drought and flooding. Precipitation in areas with big saltbrush can be very low. For instance, Goodin and McKell  noted their observation of big saltbrush occurring in conditions of 3.9 inches (100 mm) mean annual precipitation. A catalog of native seeds recommends planting in areas which receive at least 4 inches (101.6 mm) of rain per year . Although these areas may not typically receive much rain, big saltbrush occurs in areas, such floodplains and valley bottoms that are subject to flooding . Big saltbrush has been classified as flood tolerant. It can survive flooding for most of a growing season, with some root growth likely during this period .
Big saltbrush can also tolerate irrigation with saline water. Electrical conductivity and pH of water used to irrigate big saltbrush at a site near Safford, Arizona were measured twice during a study investigating its use as a forage crop. In May of 1984 the water had an electrical conductivity (EC) of 10.3 dS/m and a pH of 8.6. In September 1984 the electrical conductivity was 9.3 dS/m and the pH was 8.8 . The feasibility of irrigating big saltbrush with saltwater has also been investigated. Wiley and others  used big saltbrush from a site irrigated with seawater discharge from a shrimp aquiculture facility in Sonora, Mexico. They reported total dissolved salts of 40 parts per trillion (ppt); typical levels for seawater are between 30 to 35 ppt. In another investigation in the same area using the same water source (hypersaline, 39%-41%), the growth rate of big saltbrush was less than that for sites irrigated with freshwater in Bodega Head and Death Valley in California. However, mean annual productivity was 1,794 grams of dry weight/ m² (s = 149), which is similar to the more northern sites due to the longer growing season in Sonora . See Palatability/nutritional value for more information on the forage production of big saltbrush.SUCCESSIONAL STATUS:
In riparian areas, disturbances, typically floods, occur regularly. Johnson and others  note that desert riparian communities that establish after a disturbance typically have the same species assemblages as before the disturbance. Species composition is influenced more by site characteristics, such as depth to water table, than time since last disturbance. The frequency and intensity of disturbances does affect which species can establish. For instance, consistent flooding can allow for establishment of species that do not tolerate high levels of salt . This interaction between disturbance and site characteristics results in a dynamic mosaic of vegetation types . Whether flooding was recent or occurred some time ago, big saltbrush could occur on a site with appropriate conditions. Whether this trend would be observed after other types of disturbances, such as fire, has not been reported. However, Busch  was unable to detect a postfire successional trend in burned cottonwood-willow woodland along the lower Colorado River.
Although healthy riparian forests of the Southwest may not exhibit Clementsian succession, changes to disturbance regimes have resulted in changes in species composition. In altered habitats, such as those with decreased water tables, decreased frequency of flooding, and a resulting increase in fire, tamarisks (Tamarix spp.) can replace native species over time [17,24], resulting in older sites being dominated by dense stands of tamarisk . Due to big saltbrush being a "vigorous competitor" on sites where it is already established, these areas may be less likely to follow this pattern .However, the strong response of tamarisks after fire  could negatively affect big saltbrush exposed to increased fire frequencies. For a comprehensive review of tamarisks see the FEIS Tamarisk review and Glenn .
Few studies have addressed succession in saltbush scrub. Karpiscak  summarizes succession in saltbush and creosotebush shrublands. Species typical of saltbush or creosotebush vegetation typically recolonize abandoned agricultural areas after a series of mostly invasive annuals. Russian-thistle (Salsola kali) gives way to several mustard species (Brassicaceae) after two or three years, which is followed by annual grasses. Goldenbush (Isocoma spp.) and desertbroom (Baccharis sarothroides) follow, and typically establish just before saltbush or creosotebush species .SEASONAL DEVELOPMENT:
Fire regimes: In desert shrublands fire is rare due to lack of continuous fuels [67,82,100,120,121]. The expansion of invasive annuals such as cheatgrass (Bromus tectorum) and red brome (B. madritensis ssp. rubens) can increase the frequency of fire in these ecosystems . Fires in saltbush vegetation are likely to be more severe and spread faster with increasing fuel porosity, decreasing levels of moisture, and increasing amounts of fine fuels and dead vegetation .
Little is known of the role of fire in riparian habitats of the desert Southwest. The flammability of riparian habitats would likely vary temporally with drought and spatially due to fire frequency of surrounding landscapes . There is evidence that the fire frequency in riparian areas is longer and more variable than that of the surrounding landscape [98,99,110]. Riparian areas can slow or impede the spread of fire [29,98,99,104]. However, in drought conditions higher fuel loads compared to other saltbrush containing communities (250 to 1000 lb/acre for mesquite bosque forest compared to 40 to 100 lb/acre for saltbush/greasewood types ) can make riparian areas more susceptible to fire . Human ignitions sources [29,110] and the invasion of tamarisk  will likely increase the frequency of fire in these habitats.
The following table provides fire return intervals for plant communities and ecosystems where big saltbrush occurs. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".
|Community or Ecosystem||Dominant Species||Fire Return Interval Range (years)|
|coastal sagebrush||Artemisia californica||<35 to <100|
|saltbush-greasewood||Atriplex confertifolia-Sarcobatus vermiculatus||<35 to <100|
|paloverde-cactus shrub||Parkinsonia microphylla/Opuntia spp.||<35 to <100 |
|California steppe||Festuca-Danthonia spp.||<35 [84,103]|
|creosotebush||Larrea tridentata||<35 to <100 |
|mesquite||Prosopis glandulosa||<35 to <100 [68,84]|
SPECIES: Atriplex lentiformis
IMMEDIATE FIRE EFFECT ON PLANT:
In laboratory experiments, big saltbrush has been shown to exhibit reduced flammability compared to highly flammable chaparral shrubs  and plants with lower silica-free mineral content than big saltbrush . The effects of wildfire or prescribed burns on big saltbrush have not been investigated.
DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
Big saltbrush has been shown to have reduced flammability due to high moisture and ash contents. Montgomery and Cheo  reported reduced flammability of 3.2 to 4 inch (8-10 cm) cuttings of big saltbrush terminal growth due to its naturally high moisture content. The table below shows the ignition times and type of combustion (ignition times for char combustion are approximations) for big saltbrush of varying moisture content at 1202 °F (650 °C). Heat-dried samples were exposed to 212 °F (100 °C) for 45 minutes then placed in a desiccator until just before burning. They showed no reduction in flammability compared to heat-dried samples of species considered to be highly flammable .
|rainy season||dry season||heat-dry|
|char (18-24 seconds)||char (12-20 seconds)||flame (2.2 ± 0.28 seconds)|
Field collected big saltbrush moisture contents were high, 62.3% fresh weight in the dry season and 71.5% fresh weight in the rainy season. Big saltbrush also lost moisture at a slower rate than the other species investigated. Ash content was not found to have an effect on big saltbrush flammability. However, burning was at temperatures much higher than those where effects of ash content are likely to be observed (Philpot, personal communication in ). Philpot  demonstrated species with high ash content, including big saltbrush, exhibited reduced flammability compared to species with low ash content when burned at temperatures between 225 °F and 720 °F (125° and 400 °C).PLANT RESPONSE TO FIRE:
Despite reports of big saltbrush producing large amounts of seed , even less is known about the colonization of burned areas by big saltbrush. High ambient temperatures have been shown to decrease germination rates . However, the effects of a more intense heat source for a shorter duration have not been investigated. Although the same moisture and soil factors important on unburned sites are probably important, factors affecting the ability or inability of big saltbrush to establish on recently burned sites are unknown.FIRE MANAGEMENT CONSIDERATIONS:
Palatability/nutritional value: Leaves and seeds of big saltbrush are eaten by many species. Mule deer, pronghorn, and livestock browse the leaves [6,25,57,84,94,113]. In literature reviews, small mammals such as rabbits and rodents have been reported to eat big saltbrush [44,84]. Briggs and Cornelius  report rabbit damage to big saltbrush in a revegetation plot and Everett and others  report that, although big saltbrush was one of the least preferred species in their laboratory trials, deer mice ate its seeds. Reviews have included big saltbrush as a component of the diet of several game birds [30,44]. In a literature review, Gullion  noted use of big saltbrush by ring-necked pheasants and Gambel’s quail. Big saltbrush is also important to some insects. The saltbush sootywing uses big saltbrush as one of its hosts as a caterpillar and feeds on the nectar of big saltbrush flowers as an adult .
Several studies have investigated the nutritional content of big saltbrush. Cibils and others  found the mean and range of several nutritional measurements available in the literature. These are shown in the table below and represent values for a number of saltbush species.
|Gross Energy||3.9 Mcal/kg||3.4-4.3 Mcal/kg|
Although the values from several studies specifically investigating big saltbrush fall within these ranges [22,59,124], there are exceptions. For example, gross energy reported by Wiley and others  was less than that reported in the Cibils and others's literature review . Wiley and others found 3.1 Mcal/kg in untreated big saltbrush and 3.9 Mcal/kg gross energy in washed big saltbrush. This data was obtained from big saltbrush irrigated with highly saline water (40 ppt) . Khalil and others  included digestible energy, which was 3.215 Mcal/ Kg, and metabolizable energy, which was 2.636 Mcal/ Kg. They also found a lower fiber content, 8.0% dry weight , than the minimum reported by Cibils and others .
Wiley and others  and Khalil and others  included other big saltbrush measurements. Wiley and others  reported mean ash content measurements of 37.4% dry matter for untreated big saltbrush and 21.7% dry matter for washed big saltbrush, while Khalil and others  found an ash content of 22.0% dry weight. In addition, both of these studies measured acid detergent fiber (ADF). Wiley and others  found an ADF of 23.2% dry matter in untreated big saltbrush and 27.5% dry matter in washed big saltbrush, while Khalil and others  measured ADF as 18.5% dry weight. Wiley and others  measured neutral detergent fiber as 41.6% dry matter for untreated big saltbrush and 53.6% dry matter for washed big saltbrush. Khalil and others  included the results from their measurement of digestible dry matter, which was 74.5% dry weight. They also measured several important minerals. The results are included in the table below .
|Dry weight (%)||µg/g|
Other studies investigating nutritional values of big saltbrush included results over time or variations due to site conditions, such as high salinity. Two studies have addressed the effect of time on nutritional content of big saltbrush. The table below shows the results of Goodin and McKell  from two harvests in percent dry weight.
|Harvests at 45 cm height||Protein||Ash||Fiber||Nitrogen-free extract||Fat||Ca||P||Total carbohydrates|
|1st harvest (June)||16.9||31.6||8.5||40.2||2.8||1.00||0.21||2.9|
|2nd harvest (Sept.)||14.6||23.9||17.9||41.0||2.6||1.08||0.17||-|
Watson and others  found an effect of harvest treatment and phenological stage on the nutritional content of big saltbrush. Like Goodin and McKell  they observed a decrease in ash and protein contents over time. The table below shows nutritional information determined by Watson and others  from harvests of aboveground plant material when plants were harvested near 60 cm tall. All measurements are shown in percentages of dry weight, except fluoride, which is in ppm.
|Weeks after transplanting||Crude Protein||Ash||Neutral- detergent fiber||Acid-detergent fiber||Ca||P||F||Oxalate|
Salinity has also been shown to have an effect on nutritional aspects of big saltbrush. Ibrahim  measured the contents of several minerals in four salinity treatments. The results of this investigation, in percent dry weight, are shown in the table below.
|~ 12 dS/m||22.9||0.7||1.6||1.7||4.2|
|~ 24 dS/m||32.6||1.0||2.1||2.6||5.4|
|~ 36 dS/m||36.8||2.3||2.2||2.8||6.3|
The following table shows the ion contents in mol/g of dry weight for several durations of salinity treatments found by Malcolm and others . The 1st number in each column is the result for the low salinity treatment of 160 mS/m, while the 2nd number is from the high salinity treatment, 1,900 mS/m.
|Duration of Salinity (days)||Ca||Mg||Na||K|
Toxicity of big saltbrush may be a problem in some areas. Concern over selenium and oxalate levels have been addressed. In a literature review Guillion  notes that saltbush species can reach toxic levels of selenium. In a laboratory study soil was injected with 3 mg sodium selenate per kilogram of soil. This was repeated every ten days until the soil had been injected with 18 mg of Se/kg of soil. The harvested big saltbrush contained selenium at a concentration of 7 ppm, while the combined, root free soil had a concentration of 2 ppm. These selenium levels in big saltbrush could be toxic if it comprised the majority of the diet . Glenn and O'Leary  measured oxalate levels and found mean of 3.57% dry weight. The highest oxalate values Watson and others  obtained was 4.57% dry weight. This was considered nontoxic. Watson and others  also determined that fluoride levels were sufficiently low.
In addition to the possibility of toxicity, there are other disadvantages of use of big saltbrush as a forage species that should be addressed when considering its use. It has been found to lack phosphorus  and carbohydrates . Other authors have noted the high levels of ash  and salts, especially sodium [38,50,59]. Acceptability of big saltbrush is also an issue. Domestic goats found diets with 25% big saltbrush (leaves and smaller stems) palatable, but big saltbrush had been shown in previous investigations to have low acceptance when comprising larger proportions of the goat diet . The Cibilis and others's  literature review also addressed the issue of adaptation to the diet. They suggest that if a period of adjustment is necessary for animals to uptake the nitrogen in big saltbrush, as some evidence suggests, saltbush species may be much less useful in filling gaps in food availability. Despite these concerns most agree that big saltbrush is valuable forage for livestock, when not the sole food source [41,59,117,124].
In addition to the nutrition value, productivity of big saltbrush is another attribute which increases its forage potential. Ibrahim  notes that big saltbrush can produce over five kilograms of dry matter every 3 months. Goodin and McKell  reported yields from big saltbrush planted as a forage crop. Fresh weight yields (kg/ha) for various harvesting strategies are included in the table below.
|1st 45-cm harvest||2nd 45-cm harvest||60-cm harvest||75-cm harvest||Season mean|
They found no statistically significant (p > 0.05) advantage of harvesting twice when plants reached 17.7 inches (45 cm) compared to harvesting once at 23.6 or 29.5 inches (60 or 75 cm) height. Watson and others  also determined there was no advantage to harvesting more than once during the establishment year. The highest estimated yield of big saltbrush they obtained was 14.7 tonnes/hectare. In addition, transplant survival of big saltbrush was high . In a later investigation, Watson and O'Leary  found yield rates of 6.3 t/ha, 9.3 t/ha, and 3.5 t/ha in the subsequent harvests. Only one treatment with saline water (EC 18 dS/m) occurred before the first harvest, but thereafter the irrigation water had a mean electrical conductivity of 18 dS/m. The drop in the yield of the third harvest reflected loss of individuals from previous harvests . Glenn and O'Leary  measured the productivity of big saltbrush when irrigated with hypersaline (39%-41%) seawater and obtained an estimate of 794 grams of dry weight/ m2/ year (s=149) over a year, which was similar to productivities of big saltbrush irrigated with freshwater on sites with shorter growing seasons. Despite encouraging results with forage crops, sustainable browsing of livestock on natural stands of big saltbrush is complex. According to the Cibils and others  literature review, the processes of recruitment and mortality in saltbush species are more sensitive to changes than other shrubs. Care must be taken to incorporate both the effects of herbivory and its interactions with intra- and interspecific "competition" of the plant species when managing these communities.
Cover value: Dense stands of big saltbrush provide excellent cover for several species. Most work has investigated avian use of big saltbrush. Anderson and others  found that plots with big saltbrush had higher avian densities (p<0.05) than vegetatively similar sites without big saltbrush in 3 out of the 4 seasons investigated. Species including blue grosbeak, blue-gray gnatcatcher, Crissal thrasher, ruby-crowed kinglet, Gambel's quail, and verdin had higher densities on sites with big saltbrush . Similar studies have found comparable results [2,28]. Disano and others  found that densities of several avian species and guilds, such as passerine granivores, Gambel quail, and to a lesser extent permanent residents and visiting insectivores, were higher in areas where big saltbush and Mohave seablite coverage was approximately 1,500 plants per hectare compared to densities averaged over all riparian vegetation types along the lower Colorado River. Gullion  lists big saltbrush as one of several species in habitats that provide excellent Gambel quail cover. In a literature review he notes big saltbrush's importance to Gambel's quail in southern Nevada . Ohmart and Anderson  note the possibility of high densities of foliage arthropods contributing to the high avian habitat quality of big saltbrush, although the mechanisms behind the interaction between big saltbrush and avian populations are uncertain. In addition to providing anecdotal evidence suggesting that big saltbrush revegetation efforts improved habitat quality to the point of allowing for successful establishment of Gambel's quail, Ermacoff  reported an increase in ring-necked pheasant activity and populations as well as increased cottontail populations. Little else has been published regarding small mammal use of big saltbrush. However, information on rodent use of saltbush vegetation in general is available .VALUE FOR REHABILITATION OF DISTURBED SITES:
Although pretreatment of seeds is not necessary for germination, some pretreatments may enhance germination rates. For example, a month-long afterripening period is suggested by Jorgensen and Stevens , and improved germination occurs if seeds are rinsed or soaked and then wrung [8,125]. Young and others  reported increases in germination rate of 20% or more in seeds that were rinsed and wrung before planting when incubated at temperatures between 50 °F and 77 °F (10°-25 °C). The maximum germination rate, just over 80%, was observed when rinsed and wrung seeds were germinated at 68 °F (20 °C).
Conditions that improve germination include covering seeds with a small amount of soil and germinating at optimal temperatures and salinities. Depth of planting appears to be important factor for germination success. Goodin  reports that big saltbrush should not be planted at depths of more than 0.2 to 0.4 inches (5-10 mm). Also germination is significantly (p < 0.05) enhanced when a thin layer of soil covers the seeds. The table below shows germination rates for different soil types when seeds were planted at either a depth of 0.2 inches (0.5 cm) or on the soil surface. Differences between soil types were not statistically significant (p > 0.05) .
|Buried 0.5 cm deep||28%||45%||56%|
The ease of propagating saltbush species, including big saltbrush from cuttings [64,77,122] provides another method for production. Wieland and others  report that cuttings of many of the saltbush species tested rooted without the application of rooting hormone, although rooting success in big saltbrush was best when rooting hormone was used. Richardson and others  investigated factors affecting rooting success of fourwing saltbush, shadscale, and valley saltbush. They found that 4.7 inch (12 cm) cuttings had much higher rooting success than 2.4 inch (6 cm) cuttings, that concentrations of rooting hormone between 0.3% and 2.0% had the best results depending on the species, and that propagating cuttings in spring and summer resulted in the highest success while propagating cuttings in fall had the lowest success. In a study of 54 Nevada shrubs, big saltbrush was one of the easiest species to propagate from cuttings and had higher rooting success when cuttings were semi-hardwood and/or collected during the stage of twig growth .
Several methods and levels of effort toward subsequent maintenance have allowed successful establishment of big saltbrush. Hydroseeding [10,48], use of a niche seeder , broadcast seeding then raking , and transplanting individuals older than 9 months  have all resulted in successful establishment of big saltbrush. Briggs and Cornelius  provide a review of several revegetation efforts; some of these plant big saltbrush and planting methods used differ. Given the susceptibility of young saltbrush to drought, irrigation during the first summer is likely to improve establishment (Anderson and Ohmart, personal communication in ). Reductions in salinities, even for short periods after planting, may also assist in establishing big saltbrush . For general information on effects of water and salinity in big saltbrush establishment see Seedling establishment/growth. Fencing may be included to reduce browsing , as several revegetation projects have reported losses from livestock and small mammals such as rabbits and gophers [13,39,95]. Seed predation by deer mice has also been investigated. Although not a preferred species, big saltbrush seeds may suffer from high predation rates when other food sources are lacking . Collection of seed from on-site sources is another option. This is recommended for riparian revegetation efforts  and has produced good results . Seeds can be stored for a maximum of 3 to 6 years [8,53,89]. Winter has been suggested as the best time for planting seeds [58,90], while transplants 2 to 3 years old have been successfully planted throughout the summer when irrigated .
Large rates of big saltbrush mortality and low growth rates have been reported, but the cause of these outcomes is unknown. For instance, on the third attempt Anderson and others  successfully established big saltbrush on three watered sites along the lower Colorado River. Mean growth rates from the time of planting to 6 months later were between 0.8 and 1.2 inches (2-3 cm). Big saltbrush planted at a mine reclamation site exhibited 100% mortality. Whether this was due to the level of soluble salts, which ranged between 335 and 3182 ppm, or some other factor or factors is not discussed .OTHER USES:
Traditional Uses: Castetter's  literature review of studies on tribes of the American southwest included information regarding the Pima Indians' practice of pit curing and drying big saltbrush seeds before using them to make a thick gruel. Bean and Saubel  report a similar practice among the Chauilla as well as use of the flour to make small cakes, use of leaves as a soap, and use of flowers, stems and leaves as a treatment for nasal congestion. Conrad  suggests that seeds were likely used in a similar way to fourwing saltbush. Seeds of fourwing saltbush were also reportedly ground into flour. Other uses for fourwing saltbrush that may have been similar for big saltbrush are the use of the ground meal as an emetic, use of ground flowers or roots moistened with saliva in treating ant bites, and addition of ashes to water for dyeing meal greenish-blue .OTHER MANAGEMENT CONSIDERATIONS:
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