Sagebrush - Mountains and Plains: The Ecology of Wyoming Landscapes - page 124

Fire suppression

Fire

Native perennial grassland Sagebrush steppe with perennial grasses

Heavy grazing,
particularly
during spring

Moderate
grazing

Possible recovery
if no fire and only
fall sheep grazing

Fire

Only annuals,
rabbitbrush, and
sagebrush

Native grass cover with possible
shift toward less-palatable warm-
season species; rabbitbrush and
sagebrush may increase slightly

Fire again

Only annuals;
increased erosion

Possible recovery
with reduced grazing
if no significant loss
of soil and no fire

More
frequent fire

Near-permanent
deterioration of site

Cheatgrass and other annuals increase, as do sagebrush,
rabbitbrush, and less-palatable grasses and forbs

Fig. 7.13. the apparent effect of cheatgrass introduction,
heavy livestock grazing, and increased fire frequency in the
big sagebrush steppes of Utah and nevada. A similar scenario

may apply to Wyoming if cheatgrass becomes more common.
the introduction of exotic species can cause undesirable eco-
system changes. Adapted from West (1988).

A confounding factor may be climate change, as
both warming and higher levels of carbon dioxide
would probably favor cheatgrass expansion. even
without warming, annual plants often evolve rapidly
to tolerate new environmental conditions. in addition,
other disturbances caused by road building, plowing,
and various industries have created new habitats for
this invader and others. of great concern, cheatgrass—
an annual—persists even with very little moisture.
After a decade or more of cheatgrass occupancy and
the concomitant reduction of native species, the land
could be left with little plant cover. Soil erosion would
accelerate.
efforts to control cheatgrass have generally been
futile. experiments with herbicides, the introduction
of pathogens, and strategically timed fires and grazing
have had some success, but only at considerable cost.
Promoting the establishment of native species may

be the best approach, along with adjustments in live-
stock management, but that may require highly dis-
ruptive weed control practices, and then resting the
rangeland for many years while native species become
re-established. 76 Restoring biological soil crusts may be
required, about which little is known.
one way to stop or slow the spread of cheatgrass
is to suppress fires where cheatgrass invasion is likely
to occur, at least until effective and affordable control
strategies are found. curiously, there is evidence for the
intriguing idea that some native species may be evolv-
ing adaptations for competing with invasive species.
However, preventing the invasion of exotic plants and
pathogens should be a high priority where that is still
an option and where there is a desire to maintain bio-
diversity and the services provided by native ecosystems
(see chapter 6 for further discussion of invasive plant
management). 77