Zuckia brandegeei



INTRODUCTORY


 

Al Schneider, www.swcoloradowildfires.com

AUTHORSHIP AND CITATION:
Gucker, Corey L. 2008. Zuckia brandegeei. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

FEIS ABBREVIATION:
ZUCBRA

NRCS PLANT CODE [37]:
ZUBR
ZUBRA
ZUBRB
ZUBRP

COMMON NAMES:
siltbush
applebush
spineless hopsage

TAXONOMY:
The scientific name of siltbush is Zuckia brandegeei (A. Gray) S.L. Welsh & Stutz ex S.L. Welsh (Chenopodiaceae) [5,9]. It is common to see the scientific species name spelled brandegei throughout systematic and other literature [6,20], but the correct spelling of the last name of the first person to collect siltbush is Brandegee [2,36].

Infrataxa:
Zuckia brandegeei var. arizonica (Standl.) S.L. Welsh
Zuckia brandegeei var. brandegeei (A. Gray) S.L. Welsh & Stutz ex S.L. Welsh [6]
Zuckia brandegeei var. plummeri (Stutz & S.C. Sand.) [4,36,39]

Throughout this review, siltbush varieties are identified using scientific names.

Hydbridization: Drobnick and Plummer (1966, cited in [1]) reported that siltbush and shadscale (Atriplex confertifolia) hybrids occurred naturally, and in artificial pollination experiments, Blauer and others [1] found that viable seed was produced when fourwing saltbush (A. canescens) received siltbush pollen.

SYNONYMS:
For Zuckia brandegeei var. brandegeei:
Atriplex brandegeei (A. Gray) Collotzi ex W.A. Weber [38]
Grayia brandegeei (A. Gray) [8,27]

For Zuckia brandegeei var. arizonica:
Zuckia arizonica (Standl.) [10]

LIFE FORM:
Shrub

FEDERAL LEGAL STATUS:
None

OTHER STATUS:
Information on state-level protection status of siltbush in the United States is available at NatureServe.

DISTRIBUTION AND OCCURRENCE

SPECIES: Zuckia brandegeei
GENERAL DISTRIBUTION:
Siltbush has been described as a "narrowly distributed edaphic endemic" [30]. Isolated populations occur in salt desert habitats in the Colorado River drainage from northwestern New Mexico and northeastern Arizona to Utah and the Colorado-Wyoming border. A single siltbush population occurs outside of this area, in the Great Basin west of Sterling, Utah [3,23,35,36]. Scattered Zuckia brandegeei var. arizonica populations occur in northern Arizona and southeastern Utah [30,40]. Zuckia brandegeei var. brandegeei occurs in northeastern Arizona, south-central Utah, and western Colorado, and Z. b. var. plummeri populations occur in northeastern Utah, south-central Wyoming, western Colorado, and northwestern New Mexico [10,30,40]. Flora of North America provides a distributional map of siltbush and its varieties.

HABITAT TYPES AND PLANT COMMUNITIES:
Throughout its range, siltbush generally occurs in monotypic stands [23,30,35]. On harsh sites (see Site Characteristics), siltbush shrubs are widely spaced [35]. Desert shrublands, Colorado pinyon-Utah juniper (Pinus edulis-Juniperus osteosperma) communities, and Stansbury cliffrose (Purshia mexicana var. stansburiana) shrublands are possible at the edges of siltbush stands [24,30].

In the Chinle Shale vegetation type in the Orange Cliffs area of Utah, siltbush and shadscale dominate a transitional area between the San Rafael Desert and Canyonlands National Park. The vegetation type occurs on hard-packed gray clay and shale and may include bottlebrush squirreltail (Elymus elymoides), green rabbitbrush (Chrysothamnus viscidiflorus), galleta (Pleuraphis jamesii), and fourwing saltbush [32].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Zuckia brandegeei

 

Al Schneider, www.swcoloradowildfires.com

   

GENERAL BOTANICAL CHARACTERISTICS:
This description provides characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [5,10,40]).

Aboveground description: Siltbush is an erect, low-growing shrub. It is often described as nearly herbaceous or suffrutescent, since stems are produced annually from a persistent, gnarled woody base. Stems are slender, densely pubescent, without thorns, and may reach 2.6 feet (0.8 m) tall [3,5,6,8,28,40]. Leaves are alternate, entire to lobed, and measure 0.3 to 3 inches (0.8-8 cm) long by 0.4 to 1.8 inches (1 to 4.5 cm) wide [5,6,40]. Siltbush produces both male and female flowers, but production is temporally separate. Female flowers occur individually or in short spikes, and male flowers are often clustered in groups of 2 to 5 in spikes [3,10,40]. Siltbush fruits are one-seeded utricles that are flattened or 6-keeled and may be winged and at maturity [16,40]. The bracts that enclose siltbush seeds have been described as papery [19] or extremely hard [3]. Siltbush seeds are small. On average, 491 cleaned seeds are required to make up a gram of weight [1], and seeds are often just 2 mm broad [3].

Belowground description: In the available literature (2008), descriptions of belowground siltbush growth were generally lacking. However, unpublished data reported by Shaw and others [31] suggested that siltbush root systems can be "extensive" after a single growing season, and it is generally accepted that most chenopods (Chenopodiaceae) have deep root systems and with pulses of moisture produce ephemeral roots [18].

Siltbush varieties: Descriptions and comparisons of the siltbush varieties are provided in the following references: [30,36].

RAUNKIAER [26] LIFE FORM:
Chamaephyte

REGENERATION PROCESSES:
Siltbush primarily regenerates sexually through seed production and seedling establishment, but "a limited amount of vegetative spread also occurs" [21].

Pollination and breeding system: Siltbush flowers are wind pollinated, and plants are monoecious [24]. Although many thought that siltbush was dioecious [6,18,40], an in-depth breeding system study of a population near Sterling, Utah, determined that siltbush is monoecious. However, male and female flowers on the same plant are almost completely separated in time, so plants "functionally approach dioecy" [22]. Siltbush shrubs are either protogynous or protandrous. Erroneous reports of siltbush as dioecious were likely the result of insufficient specimen collection. Nearly all herbarium specimens were collected before female flower development or after fruit was produced and male flowers had died [24].

Temporal separation of male and female flowers indicates that cross pollination predominates. In artificial fertilization experiments, significantly fewer self-pollinated than cross-pollinated flowers produced viable fruits (P=0.0006) [22,24].

Seed production: Siltbush seed production can be sporadic, and typically protogynous plants produce more viable seed than protandrous plants [19,24]. McArthur and Monsen [16] reported that siltbush seed viability is generally low, which they attributed partly to harsh, arid growing conditions. Predation by thrips, Lepidopteran larvae [24], small mammals, and birds [16] can also reduce siltbush seed production.

In a siltbush population near Sterling, Utah, researchers found that breeding system (protandrous vs. protogynous), site conditions, and precipitation affected flowering and seed production. Protandrous plants produced significantly fewer fruits/stalk (P=0.0088) and viable seeds/stalk (P=0.05) than protogynous plants. Delayed fruit production on protandrous plants likely contributed to poor seed development. Protandrous fruits matured several weeks later than those of protogynous plants, when moisture stress was likely greater [21,24]. The importance of moisture availability to seed production was determined when multiple sites and years were compared. Protogynous plants located below a seep produced nearly double the amount of fruits and seeds/plant than those on a site that did not receive additional moisture. Both protogynous and protandrous plants produced double the number of seeds in a year when winter and early spring precipitation was 28% more than the previous year [21].

Seed dispersal: Wind and gravity are the primary siltbush seed dispersal agents [30]. Dispersal is considered slow, and fruits may remain on the plant through the winter [31]. Although birds and mammals were identified as seed predators (see Seed production), they were not noted in the available literature as important dispersers.

Seed banking: It seems unlikely that siltbush seed persists in the soil seed bank. In laboratory experiments, nearly all siltbush seed collected in Utah and Wyoming germinated after relatively short periods of cold exposure (see Germination), suggesting that persistence in the soil is unlikely unless some dormancy mechanism failed to materialize in the experiments [19]. Collotzi [3] reported that his collections of siltbush seeds were enclosed in "extremely hardened" bracts that required hot-water soaking for seed release. While extremely hard bracts were not described elsewhere in the available literature (2008), bracts have been linked to the dormancy of siltbush seeds (additional information provided in Seed dormancy).

Siltbush seeds survived less than 15 years of storage in an open warehouse in Escalante, Utah. Over a 25-year period in the warehouse, temperatures ranged from -21.8 to 101 F (-29.9 to 38.3 C). After the first 4 years of storage, siltbush germination ranged from 86% to 92%, but germination decreased significantly in subsequent years (P<0.05). After 5 years of storage, germination was 57%; after 7 years, 13%. No siltbush seeds germinated after 15 or more years of storage [33].

Germination: Prevailing climates affect siltbush seed germination requirements, and bracts that enclose siltbush seeds function in seed dormancy. After germination studies on seed collected from many sites, researchers concluded there is "strong selection pressure for adaptive germination-timing strategies in response to climate". However, regardless of temperature, seeds without bracts germinated better than seeds enclosed in bracts (also see Seed dormancy). Generally, germination was best at 59 F (15 C) and 86 F (30 C). Seeds from Antelope Valley, Utah, where January temperatures (31 F (-0.6 C)) were the warmest of all collection sites, were least sensitive to germination temperature. Seeds collected from Baggs, Wyoming, with the lowest average January temperature (17 F (-8.3 C)), germinated best at 86 F (30 C). Eight weeks of cold exposure were sufficient to encourage germination of seeds from sites where average January temperatures ranged from 25 to 28 F (-3.9 to -2.2 C). Researchers concluded that seeds from warm-winter sites were relatively nondormant, probably germinated with fall moisture, and survived as seedlings through the relatively mild winter. Seeds from cold-winter sites may germinate at high temperatures soon after dispersal but largely remain dormant until early spring [19].

Seed dormancy typically decreased with seed age and was controlled by enclosing bracts. Fifty-three percent of 4-month-old seeds were dormant, 24% of 24-month-old seeds were dormant. Experiments on seeds with and without bracts that were kept moist with water, bract leachate, or saline water revealed that physical inhibition from intact bracts was important to seed dormancy. However, another inhibitory factor was possible, since a 16 mmhos/cm concentration of leachate suppressed germination more than saline water with similar conductivities and osmotic potentials [23].

Seedling establishment/growth: Siltbush seedlings are most common in plant interspaces [23], and although they reportedly grow quickly, predation by small mammals occurs [16]. In the field, siltbush seedlings did not occur beneath the parent plant, where bracts and litter accumulated. The researcher suggested that these accumulations may, through dissolved salts or other inhibitory compounds (see also Seed dormancy), inhibit or suppress seedling establishment [23].

Vegetative regeneration: Layering is the only type of vegetative regeneration described in the available siltbush literature (2008). When studying siltbush near Sterling, Utah, Pendleton [24] wrote that "in some cases, it was difficult to determine what constituted an individual plant, whether one large plant whose lateral branches had become buried or several separate plants." Layering was also observed on a steep clay site in Colorado, although discrete shrubs were most common (Pendleton 2008, personal communication [25]).

SITE CHARACTERISTICS:
Throughout its range, siltbush often occurs on steep dry hills or slopes [8,35,40]. The extensively studied siltbush stand near Sterling, Utah, occupied slopes of 52% [24].

Soils: Siltbush habitats are rarely described without mention of soils. Typically siltbush stands occur on saline or seliniferous soils [40]. Soil textures in siltbush habitats can be fine-textured heavy clays, clay loams, or silts [10,35,36,40]. Pendleton and Meyer [23] indicated that siltbush was most common on heavy clay soils from decomposed shale with a "high shrink-swell capacity". Collotzi [3] found siltbush most often where the pH ranged from 7.4 to 7.7 on silty clay loam soils of the Chipeta formation. Siltbush populations near Sterling, Utah, occurred on slopes with little soil development [24].

Climate: The restricted distribution of siltbush suggests a fairly narrow climatic tolerance. Siltbush occurrence on salt deserts implies outstanding drought tolerance, since it maintains physiological processes in high-salt soils [35]. The climate in siltbush habitats has been described for the Orange Cliffs area of Utah, which experiences weather typical of the Colorado Plateau and represents nearly the center of the siltbush range. Nearby meteorological stations report precipitation averages of 5.2 to 11.6 inches (132-295 mm), maximum temperatures of 63.4 to 69.4 F (17.4-20.8 C), and minimum temperatures of 36.7 to 41.8 F (2.6-5.4 C) [32]. Average winter temperatures reported from siltbush habitats in Baggs, Wyoming, were much lower than minimums reported for Orange Cliffs (see Germination).

Weather can affect siltbush flowering. A series of rainstorms in early June delayed flowering, especially of male flowers, in the Sterling, Utah, population [22].

Elevation:

Elevational ranges reported for siltbush by state
State Elevation range (feet)
Arizona ~5,000 [10]
Colorado 5,000-6,500 [8]
Utah 4,200-8,010 [40]
4,800-6,700 in Uinta Basin [6]

SUCCESSIONAL STATUS:
Succession, disturbance, and disturbance responses in siltbush stands were rarely described in the available literature (2008). It is unknown whether siltbush is capable of sprouting from its woody root crown after top-kill. Postfire regeneration methods are unknown, and it is unclear how long it could take for siltbush stands to return to predisturbance density and/or coverage. McArthur and others [17] reported that "land disturbance appears to stimulate increase in numbers of plants". No other data or details were reported.

SEASONAL DEVELOPMENT:
Siltbush typically flowers in late spring or summer, produces fruit by early July, and has mature seed by late September or early October [16], (unpublished data, cited in [24]). Fruit dispersal is slow, and some seed often remains on the plant until January or throughout the winter [16,31]. Weather can affect flowering (see Climate) [22]. For information related to climate and germination, see Germination.


FIRE EFFECTS AND MANAGEMENT

SPECIES: Zuckia brandegeei
FIRE EFFECTS:
Little to nothing is known about the effects of fire on siltbush. There is no evidence that siltbush sprouts vegetatively after fire, but investigations into vegetative reproduction are generally lacking. Heat tolerance of siltbush seeds on or beneath the soil surface is unknown, so the importance of on- and/or off-site seed sources in postfire seedling establishment is unclear. Because siltbush often occurs as isolated stands, without vegetative regeneration postfire recovery may be slow.

POSTFIRE REGENERATION STRATEGY [34]:
Unknown

FUELS AND FIRE REGIMES:
Fires are considered historically rare in salt desert shrubland habitats, which are arid, usually dominated by chenopods, and occupy saline soils [41]. However, weather events that encourage production of annual species that provide fine fuel in the interspaces between shrubs may increase burning potential. After an El Nio event in Utah and other nearby desert areas, many separate fires occurred. Fires were fueled by increased production of nonnative annuals [41]. While increased nonnative grasses were reported in some salt desert shrublands of Utah, Sanderson and Stutz [29] indicated in a 1994 report that siltbush habitats rarely supported dense cheatgrass (Bromus tectorum) growth.

Without increased fine fuel production, salt desert shrublands, and more specifically siltbush stands, are dominated by widely spaced shrubs and lack the fuel continuity needed to support fire spread [25]. Based on the LANDFIRE Rapid Assessment Vegetation Models, there is little evidence of fire in salt desert shrublands, and because of the discontinuity of fuels, any fires are typically small (tens to hundreds of acres). For the most part, researchers and experts suggest that the fire-return interval for salt desert shrublands was greater than 200 years and as high as 1,000 years [11,12,13].

The Fire Regime Table summarizes characteristics of fire regimes for vegetation communities in which siltbush may occur. Follow the links in the table to documents that provide more detailed information on these fire regimes.

FIRE MANAGEMENT CONSIDERATIONS:
Information on the effects of fire on siltbush, siltbush's survival strategies, and its postfire regeneration potential is necessary before recommendations about fire use or fire exclusion in its habitats can be made. Data on mortality and postfire regeneration rates in burned siltbush stands are needed to ensure the best management of this species.

MANAGEMENT CONSIDERATIONS

SPECIES: Zuckia brandegeei
IMPORTANCE TO WILDLIFE AND LIVESTOCK:
Livestock and game animals browse siltbush, especially in the spring [17]. Thrips and Lepidopteran larvae "heavily" utilize siltbush seeds [24], and seeds that persist on the plant through the winter are often removed by small mammals and bird seeds [16]. Mice and other small rodents consume siltbush seedlings. Seedling protection may be necessary for revegetation on some sites [17].

Palatability/nutritional value: Palatability of mature plants has been rated as "moderate" (Stutz, personal communication cited in [30]).

VALUE FOR REHABILITATION OF DISTURBED SITES:
Siltbush is potentially useful in the revegetation of heavy soil sites in pinyon-juniper and basin big sagebrush (Artemisia tridentata subsp. tridentata) communities [16]. Siltbush may stabilize shale soils and is said to spread "effectively" on roadsides and roadcuts [17].

OTHER USES:
No information is available on this topic.

APPENDIX: FIRE REGIME TABLE

SPECIES: Zuckia brandegeei
Fire regime information on vegetation communities in which siltbush may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models [11]. These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the PDF file linked from the name of each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.
Southwest Great Basin Northern and Central Rockies
Southwest
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Southwest Shrubland
Salt desert scrubland Replacement 13% 200 100 300
Mixed 87% 31 20 100
Desert shrubland without grass Replacement 52% 150    
Mixed 48% 165    
Southwest Woodland
Pinyon-juniper (mixed fire regime) Replacement 29% 430    
Mixed 65% 192    
Surface or low 6% >1,000    
Pinyon-juniper (rare replacement fire regime) Replacement 76% 526    
Mixed 20% >1,000    
Surface or low 4% >1,000    
Great Basin
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Great Basin Shrubland
Salt desert scrubland Replacement 13% 200 100 300
Mixed 87% 31 20 100
Salt desert shrub Replacement 50% >1,000 500 >1,000
Mixed 50% >1,000 500 >1,000
Basin big sagebrush Replacement 80% 50 10 100
Mixed 20% 200 50 300
Great Basin Woodland
Juniper and pinyon-juniper steppe woodland Replacement 20% 333 100 >1,000
Mixed 31% 217 100 >1,000
Surface or low 49% 135 100  
Northern and Central Rockies
Vegetation Community (Potential Natural Vegetation Group) Fire severity* Fire regime characteristics
Percent of fires Mean interval
(years)
Minimum interval
(years)
Maximum interval
(years)
Northern and Central Rockies Shrubland
Salt desert shrub Replacement 50% >1,000 500 >1,000
Mixed 50% >1,000 500 >1,000
*Fire Severities
Replacement: Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Mixed: Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects.
Surface or low: Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [6,10].

Zuckia brandegeei: REFERENCES


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