Introductory
SPECIES: Ambrosia dumosa | White Bursage 



ABBREVIATION : 
AMBDUM

SYNONYMS : 
   Franseria dumosa Gray [27]


SCS PLANT CODE : 
   AMDU2


COMMON NAMES : 
   white bursage
   bursage
   burrobush
   burroweed


TAXONOMY : 
The currently accepted scientific name for white bursage is Ambrosia
dumosa (Gray) Payne [35].  It is a member of the aster family
(Asteraceae).  There are no recognized infrataxa.


LIFE FORM : 
Shrub

FEDERAL LEGAL STATUS : 
No special status

OTHER STATUS : 
NO-ENTRY


COMPILED BY AND DATE : 
Sara Lynn Korthuis, September 1988


LAST REVISED BY AND DATE : 
K. Anna Marshall, November 1994


AUTHORSHIP AND CITATION : 
Marshall, K. Anna. 1994. Korthuis, Sara Lynn. 1988. Ambrosia dumosa.
In: Remainder of Citation

DISTRIBUTION AND OCCURRENCE
SPECIES: Ambrosia dumosa | White Bursage 



GENERAL DISTRIBUTION : 
White bursage occurs throughout the Sonoran and Mojave deserts although
it is typically considered a Mojave Desert species [1].  It ranges north
to Death Valley, California, southern Nevada, and southwestern Utah.  It
extends along the Gulf in Baja California as far south as Bajia Los
Angeles and into Sonora as far south as Tiburon Island [41].


ECOSYSTEMS : 
   FRES30  Desert shrub


STATES : 
     AZ  CA  NV  UT  MEXICO


ADMINISTRATIVE UNITS : 
     ORPI  JOTR  DEVA  GRCA  LAME  SAGU


BLM PHYSIOGRAPHIC REGIONS : 
    3  Southern Pacific Border
    6  Upper Basin and Range
    7  Lower Basin and Range
   12  Colorado Plateau


KUCHLER PLANT ASSOCIATIONS : 
   K041  Creosotebush
   K042  Creosotebush - bursage
   K043  Paloverde - cactus shrub


SAF COVER TYPES : 
   242  Mesquite


SRM (RANGELAND) COVER TYPES : 
NO-ENTRY


HABITAT TYPES AND PLANT COMMUNITIES : 
White bursage is a dominant or codominant member of most plant
communities in the Sonoran and Mojave deserts.  It usually occurs in
open, species-poor communities with creosotebush (Larrea tridentata).

At the northern boundary of white bursage, in the transition zone
between the Mojave and Great Basin deserts, associated species of the
creosotebush-white bursage community include wolfberry (Lycium spp.),
range ratany (Krameria parvifolia), Mojave yucca (Yucca schidigera),
California jointfir (Ephedra funera), spiny hopsage (Grayia spinosa),
and winterfat (Krascheninnikovia lanata) [38,47].  The density of white
bursage is about 2,500 plants per hectare [3,47].

Approximately 70 percent of the Mojave Desert is covered with open or
very open stands of creosotebush and white bursage [15,29,40].
Associated species in the Mojave Desert include desertsenna (Cassia
armata), Nevada ephedra (Ephedra nevadensis), white burrobrush
(Hymenoclea salsola), and wolfberry [22].

In the Sonoran Desert, associated members of the creosotebush-white
bursage community are acacia (Acacia paucipina), fourwing saltbush
(Atriplex canescens), ocotillo (Fouquieria splendens), big galleta
(Hilaria rigida), cholla (Opuntia spp.) and western honey mesquite
(Prosopis glandulosa var. torreyana) [40].  In the Arizona Upland
Subdivision of the Sonoran Desert, the density of white bursage is 549.7
plants per hectare and white bursage cover is 2.7 percent.  In the Lower
Colorado River Valley, the density of white bursage is 84 plants per
hectare and white bursage cover is 0.1 percent [29].

In addition to the creosotebush-white bursage association, white bursage
is a member of the following associations:  Joshua tree (Yucca
brevifolia)-big galleta [24], saguaro (Carnegiea gigantea)-paloverde
(Cercidium spp.) [39], Sonoran creosotebush scrub, Mojave creosotebush
scrub, and Mojave mixed woody scrub [22].

Publications listing white bursage as a dominant or codominant species
include:

Sonoran Desert [10]
Preliminary descriptions of the terrestrial natural communities of California
  [22]
Vegetation of the Santa Catalina Mountains: community types and
  dynamics [34]
Mojave Desert scrub vegetation [60] 

VALUE AND USE
SPECIES: Ambrosia dumosa | White Bursage 



WOOD PRODUCTS VALUE : 
NO-ENTRY


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
White bursage is an important browse species in several areas of the
Sonoran Desert.  Browsing pressure on white bursage is particularly
heavy during years of low precipitation, when production of winter
annuals is low [8].

White bursage is of intermediate forage value [21].  It is fair to good
forage for horses and fair to poor for cattle and sheep.  However,
because there is often little other forage where white bursage grows, it
is often highly valuable to browsing animals [24].  Webb [51] observed
that sheep browsed primarily on new growth and seeds.

In the Mojave Desert, 8 percent of mature white bursage plants were
browsed by black-tailed jackrabbits.  Forty-three percent of
transplanted seedlings were browsed.  Fourteen percent of browsed
seedlings were more than 90 percent consumed [26].

Many desert rodents, including kangaroo rats, eat white bursage seeds
[57].


PALATABILITY : 
White bursage is moderately palatable to cattle and sheep and slightly
more palatable to horses.  Closely cropped white bursage plants on
heavily stocked range indicates inadequate forage rather than high
palatability [23].

White bursage is palatable to feral asses.  Fecal analysis indicated
that white bursage was the primary forage used by feral asses in winter
[21].


NUTRITIONAL VALUE : 
The nutrient value of white bursage fluctuates seasonally; it is greater
in the spring and less in the fall [21].  In a 2-year study in the Lower
Colorado River Valley, white bursage had a gross energy value of about
4.2 kilocalories per gram.  Crude protein was highest in February at 10
percent, declining the rest of the year to 4 to 7 percent.  Phosphorus
content was highest in spring at 1,110 milligrams per kilogram of plant
material, declining to 500 milligrams per kilogram in August and
September [21].

In the northern Mojave Desert, Romney and others [38] estimated the
nutrient load of new white bursage leaves as follows:

Nitrogen        1.29   kg/ha
Phosphorous     0.114  kg/ha
Sodium          0.035  kg/ha
Potassium       1.70   kg/ha
Calcium         0.93   kg/ha
Magnesium       0.17   kg/ha

Reichman [56] estimated that white bursage seeds contain 3,838 calories
per gram or 23.72 calories per seed.


COVER VALUE : 
NO-ENTRY


VALUE FOR REHABILITATION OF DISTURBED SITES : 
White bursage may be used to revegetate disturbed sites in southwestern
deserts.  For instance, white bursage may be planted along California
highways where unirrigated perennial vegetation has not survived [12].

White bursage may be planted from containerized plants with a high
probability of success.  Plantings should be made in late winter or
early spring, although the time of planting is less important than the
vigor of the seedlings.  Rodent protectors should be used [12].



OTHER USES AND VALUES : 
White bursage is a host for sandfood (Pholisma sonorae), a parasitic
plant with a sweet, succulent, subterranean flowerstalk.  Sandfood was
a valuable food supply for desert peoples [58,59].


MANAGEMENT CONSIDERATIONS : 
Creosotebush-white bursage communities are poorly suited for livestock
grazing because of low productivity and low water availability [23].

White bursage is sensitive to browsing.  Browsing significantly
decreased the cover and volume of white bursage by 27 and 21 percent,
respectively, in the Mojave Desert [51].  In the Lower Colorado River
Valley, overbrowsing decreased the cover of white bursage from 2.26 to
0.04 percent [21].

Pollution from electric power generating facilities may also decrease
white bursage.  White bursage showed intermediate sensitivity to sulphur
dioxide and nitrogen dioxide fumigation [45].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Ambrosia dumosa | White Bursage 



GENERAL BOTANICAL CHARACTERISTICS : 
White bursage is a native, drought-deciduous rhizomatous shrub growing
from 8 to 24 inches (20-60 cm) tall.  Its many slender, stiff branches
form a compact, hemispherical crown [14,41].  The leaves of white
bursage are small and deeply divided.  They may become so dry that it is
difficult to tell whether they are alive or dead [41].

The staminate and pistillate heads of white bursage intermingle
throughout the length of its racemes [41].  The pistillate heads are
two-flowered, producing obovoid fruits 0.2 to 0.8 inches (5-20 mm) long.
The burs generally contain 20-35 flattened, scattered, unhooked spines
that are about 0.08 inches (2 mm) long [33].

The root system of white bursage is derived from a segmented root crown,
and is mostly comprised of lateral roots [14].  Roots may grow 5 to 15
times the length of the stem [41] and extend to a depth of 28 inches (70
cm) [14].  Anderson [4] found the shoot to root dry weight ratio of
white bursage to be 1.38.  The leaf to root ratio was 0.18.

Definitive information on the longevity of white bursage is not
available in the literature.  Due to cloning, white bursage may be an
extremely long-lived shrub [32].  Some researchers, however, have
suggested that the longevity of white bursage is similar to that of its
noncloning congener, triangle bursage (A. deltoidea):  somewhat less
than 50 years [31,63].


RAUNKIAER LIFE FORM : 
   Phanerophyte
   Chamaephyte


REGENERATION PROCESSES : 
White bursage reproduces both vegetatively and sexually.

Vegetative reproduction:  Muller [32] and Wright and Howe [52] have
described vegetative reproduction in white bursage.  As white bursage
plants age, their crowns open irregularly with the successive deaths of
individual aerial shoots.  The clone slowly spreads to as much as 3.3
feet (1 m) in diameter.  The original seedling shoot branches
intricately at its base and below the soil.  The short rhizomes root
independently so that the death of the seedling stem and subsequent
rotting away of the original root crown disconnects the rhizomatous
shoots.  Windblown soil and organic debris accumulate about the base of
white bursage clones, producing a sizable mound over time [32].

Sexual reproduction:  White bursage flowers anytime during the spring,
summer, and fall if enough rain falls [1].  It produces seeds
abundantly, and seedlings establish in open space [31].  Large numbers
of white bursage seedlings emerge following heavy fall precipitation
[6].  In September of 1976, after a record rainfall near Ocotillo,
California, the density of white bursage seedlings was 466 plants per
acre (1,151 plants/ha) [55].

White bursage seeds have prickles that easily enter and remain in skin
and hair, so white bursage is probably dispersed by mammals.  Although
white bursage has moderately heavy fruits with low lofting ability,
requiring an air current of 87.9 centimeters per second, Maddox and
Carlquist [30] suggested that the tumbling ability of the fruits aids in
dispersal.

Germination experiments have been performed on white bursage.  Young and
Young [54] found that 30 days of moist stratification treatment at 35
degrees Fahrenheit (1.7 deg C) markedly improved white bursage
germination.  Graves and others [19] found that both moist sand
stratification and carbon treatments improved 7- and 14-day germination
of white bursage.


SITE CHARACTERISTICS : 
White bursage commonly grows on arroyos, bajadas, gentle slopes, valley
floors, and sand dunes at elevations up to 3,000 feet (900 m) throughout
the Sonoran and Mojave deserts [27,32,41,44,53].  It occurs on
calcareous, sandy, alluvial soil that is often underlain by a caliche
hardpan [3,13,29,41,54].  White bursage grows in pure stands or with
associates, especially creosotebush, in barren or open areas [24,31,41].

Temperatures in the Sonoran and Mojave deserts are variable and extreme.
At Puerto Libertad, Sonora, near the southern boundary of white bursage
distribution, the mean annual temperature is 68.37 degrees Fahrenheit
(20.2 deg C).  Daytime temperatures in the summer often reach 117
degrees Fahrenheit (47 deg C) [11].  In Rock Valley, Nevada, near the
northern boundary of white bursage distribution, temperatures range from
5 degrees Fahrenheit (-15 deg C) in winter to 117 degrees Fahrenheit (47
deg C) in summer [3].

Phenological events in the Sonoran and Mojave deserts are triggered by
rain.  In the Sonoran, rainfall averages 4 to 12 inches (100-300 mm)
annually with a bimodal distribution [29].  The Mojave gets more winter
than summer rain [29].  In Rock Valley, Nevada, rainfall averages 5.524
inches (138.1 mm), with 60 percent falling between September and February
[7].

Low soil oxygen may be a controlling factor in the distribution of
desert species.  White bursage was more tolerant of low soil oxygenation
than creosotebush [20].



SUCCESSIONAL STATUS : 
Succession in the desert is difficult to characterize because there is
no clear change in species composition over time.  For instance, in
creosotebush-white bursage communities, both white bursage and
creosotebush persist in the community even though changes in their
relative abundances may occur.

Most white bursage are located on bare soil away from other plants.
McAuliffe [31] found that 83 to 92 percent of all young white bursage in
creosotebush-white bursage communities were located in bare spaces.
White bursage was the principal colonizer of open spaces in those
communities.

Once established, white bursage acts as a nurse plant to creosotebush
and other desert species, providing improved microhabitat and protection
from herbivory [16,31].  McAuliffe [31] found that 85.5 percent of all
young creosotebush were rooted beneath the canopies of live white
bursage or positioned next to dead ones.  Most creosotebush
establishment apparently occurs while the white bursage are alive.  The
smallest creosotebush in McAuliffe's study were associated exclusively
with live white bursage.

Because of its colonizing ability, white bursage is a common pioneer on
disturbed areas in the Mojave Desert [36].  In a comparison between
vegetation in disturbed and undisturbed sites, white bursage was
subdominant to creosotebush on control sites and dominant on disturbed
sites 40 years after disturbance [36].  Vasek [50] noted that while
white bursage colonizes open space by large-scale seedling
establishment, creosotebush depends upon cloning or requires white
bursage for establishment.

Creosotebush-white bursage communities are probably adapted to continual
or relatively slight disturbance such as lightly shifting sand surfaces
[49,50].  If slight disturbance does occur, creosotebush-white bursage
communities recover quickly in terms of species composition [36].


SEASONAL DEVELOPMENT : 
White bursage leafs out in February or March; the mean leafing-out date
in Rock Valley, Nevada, was February 23.  The mean flowering date was
May 2 [46].  White bursage seeds usually germinate following heavy
September precipitation [6].  A minimum amount of rainfall is required
to induce germination.  For instance, a 1971 rain of 1 to 1.96 inches
(25-49 mm) was sufficient but neither an August 1972 rain of 0.68 inch
(17 mm) nor a July rain of 0.84 inch (21 mm) promoted germination [2].

White bursage has a drought dormancy period in the summer and may have
an induced dormancy period during the winter if freezing night
temperatures kill its leaves [1].

FIRE ECOLOGY
SPECIES: Ambrosia dumosa | White Bursage 



FIRE ECOLOGY OR ADAPTATIONS : 
There is little mention of fire in relation to white bursage in the
literature.  One study described limited sprouting and seedling
establishment after fire [9].

Fires in the desert are infrequent and of low severity because
production of annual and perennial herbs seldom provides a fuel load
capable of sustaining fire.  In the Mojave Desert, there is little
record of fires.  Humphrey [25] stated that the creosotebush-bursage
community is "essentially nonflammable" because the shrubs are too
sparse to carry fire.

Woody remains of white bursage take about 40 years to decay beyond the
point of recognitions [31].


POSTFIRE REGENERATION STRATEGY : 
   Small shrub, adventitious-bud root crown
   Rhizomatous shrub, rhizome in soil
   Initial-offsite colonizer (off-site, initial community)

FIRE EFFECTS
SPECIES: Ambrosia dumosa | White Bursage 



IMMEDIATE FIRE EFFECT ON PLANT : 
Fire generally kills white bursage.  A low-severity fire occurred in the
Coachella Valley, California, after 7 years of above normal
precipitation.  Some white bursage plants survived because the fire
burned patchily.  However, most white bursage plants burned because
their canopies contained numerous small branches in proximity to
herbaceous fuels.  A few white bursage plants were only scorched; they
retained most of their branches and dried foliage.  Eighty-nine percent
of white bursage plants were killed by the fire [9].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
White bursage sprouted at low rates after the low-severity fire in the
Coachella Valley, California.  Only 6 out of 16 scorched plants and 2
out of 81 burned plants sprouted [9].  White bursage seedling
establishment on burned sites was poor during the first growing season
after the fire but increased in later growing seasons.  Poor seedling
establishment was probably unrelated to seed availability since white
bursage occurred in adjacent unburned areas [9].  In postfire year 5,
cover of white bursage on burned sites was 1 percent while cover on
adjacent unburned sites was about 5.8 percent [9].



DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Biomass production and thus fuel loadings vary seasonally and annually
for white bursage.  In 1971 and 1974 in Rock Valley, Nevada, estimated
abovegound stem dry mass of white bursage was 31 and 41 grams per square
meter, respectively.  Net aboveground production was consistently higher
in spring than in fall.  In 1973, after an above average year of
rainfall, flowers and fruits made up almost half of the new tissue
produced by white bursage [47].

REFERENCES
SPECIES: Ambrosia dumosa | White Bursage 



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Related categories for Species: Ambrosia dumosa | White Bursage