| Alkali
scrub communities are typically dominated by such shrubs
as Atriplex lentiformis ssp. torreyi (Nevada saltbush),
Chrysothamnus nauseosus (rabbitbrush), Sarcobatus vermiculatus
(greasewood), and Suaeda moquinii (inkweed).
Distichlis spicata (saltgrass) and Sporobolus airoides
(sacaton) are often present in the understory. Alkali scrub
communities occur where water tables are slightly lower (two-to-four
meters deep) than necessary to sustain alkali meadows (Manning 1997).
When alkali meadows are subject to the combined anthropogenic
stresses of groundwater pumping and livestock grazing, the meadows
may become vulnerable to invasion by shrubs and conversion to alkali
shrub communities (Manning 1999). Alkali scrub communities
also occur in abandoned agricultural fields and are often floristically
depauperate, consisting, in extreme cases, of monocultures of
Atriplex lentiformis ssp. torreyi. The spatial
extent of alkali shrub communities appears to have increased greatly
in conjunction with anthropogenic disturbance, just as the extent
of alkali meadows has diminished. In many alkali shrub communities,
clumps of dead sacaton can still be found under the shrub canopy,
which suggests how recently the conversion from meadow to shrubland
occurred. |