| The Algodones Dunes are an
active system composed of a chain of very large barchan dunes.
Barchans are crescent-shaped dunes with crests oriented toward
the wind and horns oriented away from it. In the Algodones,
these horns commonly join together. Some geologists believe
the Algodones Dunes originated from sands transported from the
shores of ancient Lake Cahuilla, the forerunner of the present
day Salton Sea basin. Others disagree, citing evidence
to suggest that the sand must have come from beaches and alluvial
deposits to the west. In the Lake Cahuilla origination
scenario, northwesterly winds are believed to have driven the
sand from the beaches of the lake to the southeast. The
Algodones are believed to be among the oldest California dunes,
possibly dating back to the latter part of the Pleistocene epoch
10 to 20 thousand years ago. Although the Algodones Dunes
are thought to be less active today than in the past, they are
still observed to be moving southeasterly at a rate of about
one foot per year.
Because of their extreme
aridity, large area extent, and the challenges associated
with their constantly shifting sands, the Algodones Dunes
represent a most unique habitat for plants and animals within
southeastern California’s Colorado Desert. These natural
forces have resulted in the evolution of a number of unique
plants and animals found only in the Algodones and nearby
dunes in northwestern Mexico. The Algodones Dunes are
home to several rare, threatened or endangered plant species.
Plant species such as these which are restricted to active
dunes are sometimes referred to as psammophites(sand lovers),
or psammophytes (sand plants).
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The Silvery coloration
of the stems and leaves in many dune plants is an adaptation
to the excessive heat and light of this very arid region.
The leaves of some plants, like the Algodones Dunes sunflower,
have a dense covering of fine hairs that give them their silvery
appearance as well as a velvet-like softness. Other
plants, like Wiggins’ croton, have tiny plate-like overlapping
scales that cover the leaves. Leaf hairs or scales help the
plant to control evaporation from the leave surface, and thus
slow water loss. They also help to regulate the temperature
of the leaf by blocking out some of the light and heat within
the environment. This helps the plant to keep leave
temperatures low enough for the process of photosynthesis
to continue, allowing the plant to maintain the production
of sugars for growth even in the face of high air temperatures.
Giant Spanish needle
(Palafoxia arida var. gigantea) is an attractive pink-flowered
member of the sunflower, or aster family. It is an annual
or short-lived perennial species with dark green, linear shaped
leaves. Heads of pink disk flowers appear in both the
spring and fall, with sufficient rainfall. As its name
implies, the giant Spanish needle is larger than its more
common relative, Spanish needle (Palafoxia arida var. arida).
Giant Spanish needle grows to be three to six feet tall and
is found only within the Algodones Dunes system. The
common Spanish needle generally grows to be only two feet
tall, or less, and is found throughout much of the Sonoran
and Mojave deserts. Like many psammophilic species,
the seeds of the giant Spanish needle will germinate and emerge
as greater depths than the non-psammophilic Spanish needle.
Studies of seed germination and emergence in the two varieties
of Spanish needle have shown that in dune sand greater than
one inch deep, twice as many seedlings of giant Spanish needle
will emerge when compared to the more common Spanish needle.
At depths of three inches or greater, only seedlings of giant
Spanish needle emerged. Giant Spanish needle is listed
on the Department of Fish and Game’s (DFG) Special Plants
list and is regarded as a species of concern by the USFWS.
Sand food (pholiuma
sonoras) may be the most unusual plant of this (and possible
any) dune system. A member of the lennoa family, sand
food is a flowering plant that is parasitic on the roots of
a few perennial plans found in the Algodones Dunes, most notably
dune buckwheat (Eriogonium deserticola, and plicata coldenia
(Tiqulia plicata). Most of the year the sand food plant
remains unseen, buried deep in the sand, but attached to the
root of its host plant. In late winter or early spring,
particularly after an unusually wet fall or winter, sand food
produces a flowering stalk that passes through several feet
of sand to reach the dune surface. At the surface, the
head—a flattened, tan-colored, fuzzy disk up to five inches
in diameter—resembles the head of a mushroom. Clusters
of small, lavender to purple heliotrope-like flowers usually
appear in the woolly disks during the months of April.
Comparatively few host plants are actually parasitzed by sand
food. When they do occur, flowering heads of sand food
may be observed in clusters of a few (one to three) to many
(20 to 30). After flowering, the flower heads dry and
turn brown, remaining visible on the sand for many months.
Sand food was an important food source for the indigenous
peoples of the Colorado River delta area, particularly the
Sand Papago and the Cocopa. It is said to taste something
like a sweet potato. Sand food is listed on the DFG
Special Plants list and is regarded as a species of concern
by the USFWS.
TheAlgodones Dunes are
managed by the U.S. Department of the Interior’s Bureau of
Land Management (BLM) as part of the 184,000 acre Imperial
Sand Dunes Recreation Area. The dune system itself comprises
approximately 140,000 acres of the recreation area, including
popular off-highway vehicle (OHV) recreation spots such as
Mammoth Wash, Glamis, and Buttercup Valley. An estimated
500,000 OHV enthusiasts visited the dunes with their vehicles
in 1998. Approximately 118,000 acres of dunes (77 percent
of the dune system) are open to OHV use. The remaining
32,000 acres (approximately 23 percent of the dunes system)
are protected within the North Algodones Dunes Wilderness,
established by the 1994 California Desert Protection Act.
Motorized vehicles are prohibited in the wilderness area and
access is by hiking or horseback only.
In the spring of 1998,
the BLM with the help of the DFG, the California Native Plant
Society, and the USFWS, began a long-term monitoring program
to review the distribution and health of rare plant population
within the Algodones Dunes. A total of 34 transects
across the entire length of the California portion of the
dunes, including the wilderness and OHV open area were examined.
Data collected from these transects will be compared with
data to be collected in coming years and with a 1977 study
of the Algodones Dune rare and endangered plant populations
to evaluate the effects of OHV recreation on these unique
dune plants. The ongoing challenge for the BLM, USWS
and DFG is to ensure that the management of the Algodones
Dunes provides for reasonable recreational access for the
public while preserving the rare, threatened and endangered
plants and animals of this unique system for future generations.
James Dice
is a plant ecologist with the California Department of Fish
and Game’s region 6. Debra Sebasta is a botanist with the
Bureau of Land management California Desert District El Centro
Field Office.
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