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Revegetation of Native Grasses at a
Mojave Desert Gold Mine
1
Raymond Franson 2
Cattle were introduced to the east Mojave Desert in the 1880•s, and records indicate the
vegetation was mostly grass, shoulder high by some accounts, with some herbs. Gold was
discovered in 1906, and mines were established in areas already altered by grazing. The influx of
miners, and the resultant effects of cattle drives to provide beef to the miners may have created
even more disturbance. Currently, the area must be considered borderline habitat for grazing, as
the land will only support one cow per 1000 acres.
At this elevation, 4300-5000 feet above sea level, there are reportedly 175 species of native
plants, but many are rarely found. The rainfall pattern differs from that of Arizona, as most of the
eight inches of mean annual precipitation falls in the winter months. Seed set in a given year is
undependable, and successful establishment from seed is rare. These conditions, coupled with
degradation from cattle and mining, make revegetation projects in the Mojave particularly
challenging. Propagation of seed in a greenhouse, from plants collected locally, is an important
element in revegetation of these mine sites, as is a salvage nursery for plants removed from sites
that are slated for mining activities.
Grasses present a special suite of problems for revegetation. Many rarely set seed in native
habitats. Propagation under greenhouse conditions is possible, but successful live plantings are
very difficult, even if the plants are hardened off. Supplementation of sparse natural rainfall with
irrigation brings salts to the surface. The planting substrate is crushed rock, so there is no topsoil
to provide appropriate growth media for grasses. Without topsoil, there is no mycorrhizal network to
provide nutrients to the grasses. These conditions, although unfavorable for grass, are conducive to
the establishment of some exotics, namely Russian thistle.
Although many regulators now insist on the use of vesicular-arbuscular mycorrhizal fungi as a
component of revegetation projects, most land use managers are not qualified to determine the
appropriate fungal population for a given site, and may become victims of unscrupulous
contractors. Independent assessment of the mycorrhizal component of a revegetation program
may prevent abuses.
1
2
Summarized by Linda Elliott, Botany Department, Arizona State University, Tempe, /lZ..
Viceroy Gold Corporation, Searchlight, NV.
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