BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Atriplex canescens | Fourwing Saltbush 



GENERAL BOTANICAL CHARACTERISTICS : 
Fourwing saltbush is an erect, warm-season, freely branching evergreen
shrub [44,69] which generally grows from 1 to 7 feet (30-200 cm) in
height and from 1 to 15 feet (30-450 cm) in crown diameter [25].  A
giant or gigas form which is found in the Little Sahara Sand Dunes near
Jerico, Utah grows at nearly twice the rate of other fourwing saltbush
populations and typically reaches 8 to 15 feet (244-457 cm) in height,
with a crown spread of 12 to 15 feet (366-457 cm) [49,54].  Growth form
of fourwing saltbush varies from open and treelike to a dense, closed
canopy [47].

Fourwing saltbush is described as the most variable and rapidly evolving
species in North America [53].  Populations and individuals exhibit
great variation in chemical composition, reproduction, palatability,
seed production, sex expression, growth form, winter hardiness, leaf
retention, and tolerance to soil salinity or alkalinity [27].  Numerous
varieties, races, ecotypes, and forms, each adapted to a specific
habitat, have been identified.  Diploid and polyploid races occur (2n,
4n, 6n, 10n, and 12n), with most populations autotetraploid (4n)
[51,53].  Most chromosomal races are morphologically distinct enough to
permit easy identification [51].  Most populations of fourwing saltbush
include both dioecious and low frequencies of monoecious individuals
[54].  Crowding, drought, and winter-induced stress can all result in
sex changes, usually by the pistillate individuals which assume male
characteristics [24,70].

Leaves are sessile to sub-sessile, entire, and gray-scrufy [69].  Some
accessions produce summer leaves which are followed by winter leaves,
whereas others produce only summer leaves [53].  Fourwing saltbush has a
deep and extensive root system, which can extend to 19.5 feet (594 cm)
in depth [6].  A plant 3.5 feet (107 cm) tall with a crown spread of 4
feet (121 cm) was found to have roots 6.5 feet (198 cm) deep in a
10-foot (304.8 cm) radius [34].  Fourwing saltbush accumulates wood
annually [50].  Mature plants often have considerable amounts of dead
wood in the crown (up to 60 percent of the total wood)[16].  Woody
tissues apparently absorb water in the spring when moisure has
evaporated [39].

Fruit of the fourwing saltbush is a wind- or gravity-dispersed, winged
utricle [9].  Fruit size and production are highly variable.  Leaves and
fruit may persist into or even through the winter [39].  

Fourwing saltbush is generally resistant to drought and tolerant of soil
salinity and alkalinity [37].  Salts from the soil in which it grows
tend to accumulate in the tissue of fourwing saltbush.  These
accumulated salts may act as an "antifreeze" in more northern climates
or alternately may promote greater drought tolerance [50].

The lifespan of fourwing saltbush is variable.  On neutral soils in
mountain brushlands, maturation is rapid, with senecence occurring at
approximately 10 years [39].  However, on drier alkaline sites, the
lifespan of fourwing saltbush is significantly longer [39].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Seed:  Fourwing saltbush typically produces an abundance of light, wind-
or gravity-dispersed seed [9].  Seed production in this prolific species
has been observed in plants as young as 1 year of age, although this is
probably uncommon [9].  Wide annual fluctuation in annual seed
production occurs as does ecotypic variability in the amount of seed
produced at a particular site [9,26].  Seed fill is also highly
variable, ranging from very little to 75 percent or more [9].  Cultivars
generally produce fill in excess of 70 percent [9].  Little is known
about length of seed viability under natural conditions; however, seeds
have remained viable for 10 to 16 years in laboratory tests [40,46].
Seeds often remain on the plants until the following spring and can
persist on the plant for up to 2 years in some instances [9].

Germination:  Germination is often erratic and varies greatly according
to ecotype, race, or form [41].  Germination rates are generally higher
in diploid than in tetraploid chromosomal races [55].  These differences
are illustrated below [54]:

              Pollen         Seed           Seed           Germination
              Fertility      Germination    Fill           of Filled Seed
              (%)            #       %      #      %       #         %

Diploids        72         316/1100  28.7  1194/3720 32   1053/1194  88.11
Tetraploids     51         549/5800   9.5  1400/4093 34   140/2828    4.90

Maximum germination occurs between 55 and 75 degrees F (13-24 degrees C)
[67].  Germinating fourwing saltbush is best able to tolerate moisture
stress at 63 degrees F (17 degrees C) [41] and does not respond to the
presence or absence of light [46].  Dewinging seeds and using a
hammermill generally speed germination [41].  A 10-month afterripening
period typically enhances germination of fourwing saltbush [9].
Chemical treatments, scarification, and water soaks have been tried, but
none of these methods have consistently improved germination [9].  The
removal of pericarps generally speeds germination [58] but seed coats
are quite variable.  Scarification has increased germination in some
types of fourwing saltbush seed but has had little effect on others
[67].  Although timing varies greatly, seedlings can emerge in only 6 to
20 days [9].
              
    Seed Source        Temperature        Days          % Germination

        CA             65-75 degrees F     30                44
        NM             65 degrees F        30                94
        UT             32-38 degrees F     50                53

Vegetative regeneration:  The fourwing saltbush is known to reproduce
vegetatively through root sprouting or layering.  Adventitious buds
sometimes form on the root crown or underground portions of the stem
[63].  The relative importance of vegetative reproduction is not well
documented for this species.  However, a study of two New Mexico sites
revealed that up to 77 percent and 96 percent of the plants respectively
were of root sucker origin [63].  The gigas diploid form which grows in
the Little Sahara Sand Dunes of Utah is known to layer [25].


SITE CHARACTERISTICS : 
Fourwing saltbush is well adapted to a wide range of temperature and
soil conditions.  It is highly tolerant of drought, salinity, and
alkalinity.  Fourwing saltbush occurs on sand dunes, in gravelly washes,
on mesas, ridges, alluvial plains, and slopes [25].

Soils:  Fourwing saltbush is particularly common on deep, well-drained,
sandy often alkaline soils in desert and foothill ranges of the Great
Basin [49].  However, it also grows well on heavy clay and on
selenium-enriched soil [5,25].  Although fourwing saltbush has been
reported on sites with as much as 1 percent soluble salts [39], soil
salinity usually ranges from 307 to 1,693 p/m, and healthy plants have
been observed growing on soils with soluble salts in excess of 4,229 p/m
[60].  Cultivars have been developed which grow readily on coal,
uranium, bentonite, and copper or other hard rock mine spoils [3].

Elevation:  Generalized elevational ranges are as follows [7]:

             from  3,900 to 8,600 feet (1,190 to 2,623 m) in CO
                   4,200 to 8,000 feet (1,281 to 2,440 m) in UT
                   4,400 to 6,900 feet (1,342 to 2,105 m) in WY


SUCCESSIONAL STATUS : 
Facultative Seral Species

Fourwing saltbush occurs in a number of climax saltbush-grassland
communities.  It also readily colonizes newly disturbed areas and is
well represented in many early seral communities [62].



SEASONAL DEVELOPMENT : 
Leaves generally remain succulent even during midsummer [29] when most
annual growth has ceased [44].  Depending on the accession or even the
individual, leaves may be retained throughout the winter months.  Some
accessions produce summer leaves followed by winter leaves, whereas
others produce only summer leaves [53].  In the Upper Sonoran Desert,
growth resumes in spring to early summer, and in the Lower Sonoran
Desert, renewal growth begins with summer rains [59].  Time of flowering
is as follows [7]:

                        Beginning of Flowering      End of Flowering
         CO                     May                   September 
         MT                     August                October
         ND                     July                  August
         UT                     May                   September
         WY                     June                  September

Fruit generally ripens from October to December, with seed dispersal
from October through April (3 to 4 months after flowering) [9,59].  In
some instances, seed may remain on the plants for 1 or 2 years [9].

Related categories for Species: Atriplex canescens | Fourwing Saltbush