December 2012 Number 1 - Utah Native Plant Society

Calochortiana December 2012 Number 1
sima) and Russian knapweed (Acroptilon repens) found
throughout Carson Slough, as well as in the parceled
wet meadows created adjacent to Rogers Spring where
spring water once flowed unobstructed into the slough.
The Refuge is in the habitat restoration stage and will
remain so for many years. Goals of the restoration plan
include restoring natural hydrology and native vegetation
communities, establishing a baseline of existing
vegetation communities, and managing and recovering
rare and endangered species occurring on the Refuge
(McKelvey 2007). The U.S. Fish and Wildlife Service
is conducting long-range, strategic management and
restoration planning at AMNWR to accomplish the recovery
goals of ecosystem and species restoration. The
recovery objective for the Refuge is: “delisting for all
species but the Devil’s Hole pupfish, which can only be
downlisted to threatened status” (Sada 1990).
PRELIMINARY VEGETATION MAPPING AND
CLASSIFICATION
The consulting firm BIO-WEST, Inc. undertook two
studies designed to assist the AMNWR with its restoration
efforts. The first study involved mapping all vegetation
communities to a fine scale (0.25 acres), with the
objective of providing a baseline data set for evaluation
of management actions and future vegetation change,
while the second included a comprehensive survey of
distribution and abundance for twelve rare plant species.
Completion of vegetation mapping on the Refuge has
resulted in 6,237 delineated polygons (Figure 2). Of the
delineated polygons, 5,913 (or 95 percent) have been
assigned a preliminary alliance. Alliance assignments
will be referred to as preliminary until classification is
finalized. These classifications are being derived from
multiple sources including Alliances of the Mojave Desert
(USGS 2004), the National Vegetation Classification
System (Grossman et al. 1998), and community
data available on NatureServe (USGS 2004).
As currently assigned, the alliances comprising the
highest total acreage on the Refuge are the Atriplex confertifolia
Shrubland Alliance, the Larrea tridentata-
Ambrosia dumosa Shrubland Alliance, and the Isocoma
acradenia Shrubland Alliance. Several delineated vegetation
communities do not correspond to any previous
classifications. Often this is the result of a Refuge community
that has a typical dominant species occurring
with an atypical co-dominant. An example of this is the
Atriplex confertifolia Shrubland Alliance compared with
the Atriplex confertifolia-Suaeda moquinii Shrubland
Alliance. The first is a common community throughout
the desert southwest. However, communities with both
Atriplex confertifolia and Sueda moquinii occurring as
co-dominants have not been classified. In these cases a
new alliance classification may be written to best represent
the vegetation community. Once final classifica-
tions have been assigned, botanical descriptions will be
developed for each of the newly created alliances.
Association classifications are also currently in the
developmental stage. Many of the common botanical
associations are applicable to communities at the Refuge.
However, a significant number of the delineated
polygons contain associations of plants that are not
commonly recognized in current classifications. These
associations are being thoroughly researched in order to
identify appropriate resources for classification assignments.
As with the alliance classifications, we expect to
develop several new association classifications to accurately
describe the communities at the Refuge (BIO-
WEST 2008).
The vegetation mapping effort has resulted in a
clearer picture of the diverse composition of vegetation
communities that exist within AMNWR (Figure 2).
Common vegetation communities that have been identified
include Alkali Sink (an extensive shrubland community
dominated by succulent shrubs such as Mojave
seablite, [Suaeda moquinii] that occur adjacent to seasonally
flooded wetlands and along desert washes), as
well as a variety of wetland communities. Lowland Riparian
Woodlands are found in the lowest elevations of
the Refuge; they support a variety of canopy species
such as velvet ash (Fraxinus velutina), mesquite
(Prosopis), and narrow-leaf willow (Salix exigua). One
of the more unique community types is the Alkali Playa
community found west of Crystal Reservoir and Lower
Marsh. This community may support the largest populations
of rare and endemic plants on the Refuge.
The western portion of the Refuge also supports
well-established populations of salt cedar, Russian
knapweed, and five-hook bassia (Bassia hyssopifolia).
The salt cedar communities function as riparian woodlands
and in some cases may provide important wildlife
habitat. Several of the abandoned agricultural fields
have been infested with five-hook bassia. However,
these fields currently receive enough seasonal inundation
to sustain recruiting populations of native wetland
vegetation.
Fairly intact transitional Upland and Desert Shrubland
communities are present in the central and eastern
portions of the Refuge. The Alkali Shrub community
type transitions from a mesic phase as the topography
rises in elevation from west to east. A noticeable
change in vegetation composition occurs as whiteflower
rabbitbrush (Chrysothamnus albidus)-dominated communities
become replaced by alkali goldenbush
(Isocoma acradenia) in the higher elevations where the
water table is less accessible. Moving up into the alluvial
fans, what was once classified as part of Creosote
Shrubland is now classified as Salt Desert Shrubland
composed of desert holly (Atriplex hymenelytra), shad-
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