December 2012 Number 1 - Utah Native Plant Society

Calochortiana December 2012 Number 1
Biogeography of Rare Plants of the
Ash Meadows National Wildlife Refuge, Nevada
Leanna Spjut Ballard,
Ballard Ecological Consulting, Millville, UT
Abstract. The Ash Meadows National Wildlife Refuge encompasses more than 23,000 acres of unique desert that
provides habitat for at least 25 plant and wildlife species found nowhere else in the world. Distinctive hydrology sustains
high concentrations of endemic plants on the Refuge. Spring complexes, alkaline desert uplands, and velvet ash,
emergent marsh and wet meadow communities known only to exist within the Refuge provide structure and habitat
for several rare, endemic and endangered plants. Two studies designed to assist the Refuge with large-scale habitat
restoration plans are underway. These studies include mapping all vegetation communities to a fine scale and locating
and mapping the distribution of rare and listed plants on the Refuge. Mapping and classifying the vegetation communities
to the alliance and association scale throughout the entire Refuge will provide a baseline of existing ecological
conditions for monitoring change in the future. The rare plant surveys will also serve as a tool for monitoring the rare
plants and the habitats in which they occur. Initially, vegetation classification standards were based upon community
types derived from multiple earlier published sources. Due to the unique habitats and patterns of co-dominance of
species occurring at the Refuge, several new alliance and association classification descriptions are being written to
accurately describe plant communities.
Description of the Ash Meadows National Wildlife
Refuge
The Ash Meadows National Wildlife Refuge
(AMNWR) encompasses more than 23,000 acres of
unique desert that provides habitat for at least 25 species
found nowhere else in the world. The refuge may support
the largest concentration of endemic species of any
terrestrial landscape in the 48 contiguous United States.
The Devil’s Hole pupfish (Cyprinodon diabolis) and
one plant species, Ash Meadows niterwort (Nitrophila
mohavenis), are listed as federally endangered, and most
of the other endemic species are either listed as threatened
or are managed as sensitive species. Unfortunately,
past human activities in AMNWR have resulted in the
invasion of numerous non-native plant species, several
of which negatively affect native populations and habitats
(Otis Bay and Steven Ecological Consulting 2006).
Ash Meadows is essentially a watered island amidst the
vast Mojave Desert. Groundwater discharging from a
regional carbonate aquifer feeds the numerous springs
that exist at Ash Meadows. Spring discharge maintains
soil moisture in the lowlands while uplands receive water
only from rainfall that averages less than 2.75 inches
annually. Annual evaporation exceeds 98.50 inches.
Ash Meadows is situated at approximately 2,200 feet
elevation in the Mohave Desert, 40 miles east of Death
Valley National Monument headquarters at Furnace
Creek, California, and 90 miles northwest of Las Vegas,
Nevada (Figure 1). It is located in the east-central portion
of the Amargosa Desert. A series of Cambrian
limestone and dolomite ridges form the eastern boundary
of the Refuge near the center of the Amargosa Val-
ley. The northern boundary crosses Quaternary playa
deposits while the southern boundary primarily crosses
Quaternary alluvial fan deposits. The pattern of sand
dunes, badlands, alluvial fans, and broad meadows observed
throughout Ash Meadows is the result of a history
of playa deposition followed by erosion, formation
of alluvial fans adjacent to surrounding ranges, and the
transport of sand by both wind and infrequent flows in
larger washes and drainages.
The distinctive hydrology of Ash Meadows is the
result of an extensive groundwater system and surface
water drainage that culminates in the Carson Slough, a
tributary to the Amargosa River (Otis Bay and Stevens
Ecological Consulting 2006). Carson Slough is the primary
drainage in Ash Meadows and is generally considered
the core of the Ash Meadows ecosystem. The Crystal
Spring drainage and the Jackrabbit/Big Spring drainages
are significant tributaries of Carson Slough and
drain large portions of the Refuge. Two primary aquifers,
a regional carbonate aquifer and a local valley-fill
aquifer, are present. Water is generally retained within
the wetlands and alkali flats that sustain many of the
Refuge’s endemic plants, as well as some endemic fish
and wildlife species (BLM 2007). The persistence of
this water since the late Pliocene/early Pleistocene has
allowed for the continued existence of relict plants and
animals which gained access to the region during pluvial
climates. The isolation of these species in this harsh
environment permitted their differentiation from related
taxa and resulted in the distinctive character of many
present-day occupants (Reveal 1980). The onset of
more xeric conditions isolated Ash Meadows, thereby
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