BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Sarcobatus vermiculatus | Black Greasewood 



GENERAL BOTANICAL CHARACTERISTICS : 
Black greasewood is a native, long-lived, winter deciduous, perennial
shrub which grows 3.3 to 8.2 feet (1.0-2.5 m) in height [11,46,55].  It
is most typically a freely-branched and spreading shrub, although
rounded and erect growth forms also occur [20,55].

Branches, some of which end in spines, are rigid and numerous [20,55].
Bark is smooth and whitish, and graying at maturity [21,55].  Black
greasewood typically has a long taproot.  Roots can extend 20 to 57 feet
(6.1-17.4 m) below the soil surface [13].  Leaves of black greasewood
are simple, linear, alternate, and fleshy, with entire margins [20,55].
The leaves are shed in winter.  

Numerous staminate flowers are borne on fleshy, catkinlike terminal
spikes, whereas pistillate flowers form singly or in pairs in the axils
of leaflike bracts [7,55].  Fruit is a small, coriaceous achene which is
winged at the middle [55,59,61].  The fruit contains small brown seeds
[34,61].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Seed:  Black greasewood is generally monoecious.  Staminate and
pistillate flowers mature at different times, thus maximizing
opportunities for cross-pollination [49].  According to McArthur and
Sanderson [30], the investment in male and female functions varies from
dry to mesic sites, allowing for efficient occupation of patchy,
stressful, and heterogeneous environments.  Seeds mature in the fall and
are dehisced over the winter [49].

Some seed is produced annually [39,55], but abundant seed production is
limited to occasional years [4].  Seed production also apparently varies
according to levels of disturbance.  Roundy and others [49] report that
black greasewood is a poor seed producer on undisturbed sites.  Only 20
percent of the plants on undisturbed sites produced seed, with an
average total of less than 20 seeds per plant [49].  However, where 30
percent of the black greasewood had been killed, resprouted plants
produced an average of 250 seeds [49].  Seed fill varies from 16 to 94
percent [11].

Germination:  An afterripening period of 30 to 60 days is generally
required for the embryo to mature [11].  Laboratory studies have
indicated that optimum germination occurs within an average of 5.5 days
at a constant temperature of 52 degrees F (11 degrees C) and -16
moisture requirement bars [50].  Under natural conditions, most seeds
germinate during relatively long periods of high soil moisture [46].
The presence or absence of light does not appear to affect germination
rates [50].  The presence of the membranous pericarp and enclosing
papery bracts, however, does influence germination [64].  When the
pericarp was broken, the embryo uncoiled within an hour, and root hairs
developed within 24 hours [11].  When the pericarp remained undamaged,
the seeds quickly imbibed water, but germination was slow and many seeds
had not germinated after 30 days [11].

Both inter- and intra-population differences in germination have been
observed at varying osmotic potentials and salt concentrations, and
ecotypic variation in germination characteristics is suspected [46].  A
certain proportion of seed commonly fails to germinate at low osmotic
potential or where salt concentrations are high.  These remaining seeds
may germinate later, thus representing an adaptation to a range of
environmental conditions [46].

Vegetative regeneration:  Black greasewood typically sprouts after fire,
application of herbicides, and other types of disturbance [62,65].


SITE CHARACTERISTICS : 
Black greasewood grows on dry, sunny, flat valley bottoms, on lowland
floodplains, in ephemeral stream channels, and at playa margins [49,57].
It is a dominant plant throughout much of the Great Basin and Mojave
Desert.  Black greasewood occurs in salt shrublands, inland saltgrass,
northern and southern desert shrub, and pinyon-juniper communities
[34,37].  Black greasewood communities generally occur below the moister
sagebrush or shadscale zones [49].  In high saline areas, black
greasewood often grows in nearly pure stands, although on less saline
sites it commonly grows with a number of other shrub species and
typically has a grass understory [29].

Soil:  The growth and distribution of black greasewood is affected by
soil salinity, ionic concentrations, soil depth, and total water
potential [48].  Black greasewood is often considered an indicator of
saline-sodic or relatively moist soils [44,50].  Sites typically have
clay-loam, silt-loam, or deep, fine, sandy loam soils with high salinity
or alkalinity [11,21].  Although black greasewood most commonly develops
on finely textured saline or alkaline soils, it occasionally grows on
coarsely textured nonsaline soils [46].  Black greasewood is often
abundant on outcrops of alkaline or salt-bearing shales with little soil
development [38,53].

In some areas, the salt content of the soil 3 feet (1 m) below the
surface reaches 1.08 percent [13].  When salinity increases above this
level, black greasewood becomes yellow and dwarfed [13].  Representative
pH levels at a black greasewood site are as follows [6]:

               pH               Na (me/100g)          Ca (me/100g)

upper soil    7.9                    9.1                   9.1
lower soil    8.0                   12.0                  15.4

Exchangeable sodium can range up to 12.0 me/100 g, with a pH as high as
9.82 [11].  Black greasewood is highly tolerant of boron, as well as
sodium, in the soil beneath the canopy [43,48].

Climate:  Black greasewood is tolerant of a wide range of climatic
conditions but most commonly grows in areas with hot, dry summers [44].
The distribution of black greasewood is thought to be highly dependent
on a high soil moisture content below the depth of seasonal
precipitation percolation [45,57].  It commonly occurs in areas with a
seasonally high water table and is often the only green shrub in pluvial
desert sites with available groundwater [63].  Average annual
precipitation ranges from 5 to 10 inches (12-25 cm) [48].  The water
table is generally within 14.8 feet (4.5 m) of the soil surface, and may
rise seasonally to 5 to 3.3 feet (1.5-1 m) below the surface [48].

Elevation:  Elevational ranges by geographic area have been documented
as follows [10,34,61]:

            from  3,000 to 7,000 feet (914-2,134 m) in CA
                  4,500 to 8,500 feet (1,373-2,593 m) in CO
                  4,000 to 7,118 feet (1,220-2,170 m) in UT
                  3,600 to 7,300 feet (1,098-2,227 m) in WY


SUCCESSIONAL STATUS : 
Black greasewood, a long-lived species, occurs as a nonclimatic climax
indicator in many saltbush, sagebrush, or sagebrush-grassland
communities.  It is described as a "stable dominant" under moist-sodic
edaphic climax conditons [11].  Black greasewood can compete after
disturbance and is also well represented in a number of early seral
communities.  Many Great Basin sites now occupied by black greasewood
were formerly dominated by Great Basin wildrye (Leymus cinereus) or big
sagebrush (Artemisia tridentata) [7,43].  Soil changes in the form of
increased salinity brought about by litter deposition of greasewood may
have led to the replacement of sagebrush [43].  With increasing salinity
(above 1.08 percent), black greasewood is replaced by species such as
inland saltgrass (Distichilis stricta var. stricta), pickleweed
(Allenrolfea occidentalis), or samphire (Salicornia utahensis) [13].


SEASONAL DEVELOPMENT : 
Vegetative development:  Leaves of black greasewood appear in mid to
late spring [55].  Vegetative growth is initially slow, but a period of
accelerated growth, lasting from 3 to 6 weeks, occurs annually from late
May to early July [49].  Increased soil temperatures may promote
accelerated growth of greasewood, while low soil moisture ends this
rapid period of growth [49].  Accelerated leader growth at a Nevada site
was documented as follows [49]:

                 Onset Date                     Cessation Date
       Average           Range            Average         Range  

       May 15            May 10-25        June 30         June 25-July 10
       May 15            May 15           June 15         June 5-25
       May 15            May 10-25        June 20         June 5-July 10

Leaves of black greasewood are shed in early fall or over the winter
months [49].  Phenological development of black greasewood at a
southwestern Colorado site was documented as follows [5]:

                Stage                    Date

                dormant                  October-December
                early leaf               March
                full leaf                April
                flower buds developing   April
                early bloom              May
                fruit developing         June
                seed ripening            July
                seed shattering          July-September

Flowering:  The appearance of spikes coincides with the onset of rapid
growth, with spikes opening after maximum vegetative growth is completed
[49].  Reddish-green, winged utricles are formed by the pistillate
flowers from late July to late August [11,49].  Floral development at a
Nevada site was as follows [49]:

Staminate        Staminate         Staminate      Winged calyxes     Utricles
flowers appear   flowers open      flowers dried  formed             matured

   May 25           June 8            July 1         July 20         October
   May 16           June 7            June 20        July 25         October

Generalized flowering by geographic area is as follows [10,34]:

Location    Beginning of flowering      End of flowering

CA          May                         August 
CO          May                         August
MT          June                        June
ND          June                        July
UT          July                        October
WY          May                         September

Seed matures from late July through November.  Seeds are shed from late
fall through the following spring [11,49].

Related categories for Species: Sarcobatus vermiculatus | Black Greasewood