Sagebrush - Mountains and Plains: The Ecology of Wyoming Landscapes - page 121

ing of the climate could favor grasshoppers, killing
many of the shrubs and reducing forage availability
at a time when it already is in short supply because of
drought. Historically, grasshopper densities fluctuate
greatly from one year to the next, leading entomolo-
gists to conclude that control measures in most parts of
Wyoming are beneficial only during the year that insec-
ticides are applied. Usually, little or no multi-year bene-
it occurs. 58 it is still unknown whether global warming
will change that conclusion.

elevations, where mountain big sagebrush is the domi-
nant shrub. 61 Fire rotation can be thought of as the aver-
age time required for one or more fires to burn an area
equal to the entire landscape under consideration. it's
tempting to think that global warming and drought will
shorten the fire-return interval in sagebrush ecosystems.
However, if droughts are severe enough, the interval
could be lengthened because of less fuel production.
Gaining confidence in fire rotation estimates is im-
portant, because prescribed fire can be a good manage-
ment strategy in some places. However, at the present
time, how often should sagebrush be burned, if at all?
Has fire suppression really created a stand in need of res-
toration, or might the area be thought of as old-growth
sagebrush with values for wildlife? Answers to such
questions are required for the proper management of
animals that are sagebrush obligates. As the sagebrush
habitat is fragmented in one way or another, these
species have less habitat available to them, potentially
reducing their populations to the point where they
become locally rare or extinct. Significantly, the re-
establishment of sagebrush can require several decades,
and if invasive plants (such as cheatgrass) already have
seeds in the soil, there is the potential that sagebrush
may not recover at all.
in general, the effects of fire on sagebrush eco-
systems are more prominent than those following
grassland fires because many of the shrubs are killed
(figs. 7.11 and 7.12). other native species also may
be reduced in abundance by burning, such as idaho
fescue, needle-and-thread grass, pricklypear cactus,
and threadleaf sedge—though others can be favored,
such as bottlebrush squirreltail, Sandberg bluegrass,
and western wheatgrass. 62 Although the cover of big
sagebrush is greatly reduced by fire, several sprout-
ing shrubs persist or increase in some locations, for
example, horsebrush, rabbitbrush, and winterfat in
relatively dry basins; and antelope bitterbrush, prairie
rose, silver sagebrush, skunkbush sumac, and western
snowberry in more moist environments. 63 Sprouting
species definitely are favored if fires occur more than
once every 20-25 years. As expected, perennial grass
production commonly increases when competition
from shrubs is reduced. 64 Unfortunately, undesired
weedy species also can increase. 65

Fire

once started, whether by humans or lightning, fire can
burn large areas of sagebrush. in 1868 James chisholm
explored the Wind River Basin and the vicinity of
South Pass city during the Wyoming gold rush. He
observed the rapid spread of at least two human-caused
fires across what must have been sagebrush-dominated
uplands, 59 writing in his journal:

the grass took fire and all our efforts could not extin-
guish it. this time the situation was really alarming,
for there was a prospect that the entire Wind River
Valley might go up in a flame. . . . the flame went over
the nearest hill with amazing velocity, Heaven knows
how far. . . . the mountains were black and bare over
which we travelled for the rest of that day, and we saw
the fire pursuing its way far ahead in several direc-
tions, but fortunately away from the valleys.

the words “mountains” and “away from the valleys”
suggest that much of the burned area was in the foot-
hills or higher, where mountain big sagebrush probably
was the dominant shrub and fuel accumulation might
have been greater.
the mean fire-return interval in sagebrush steppe
in the 1800s is thought to have ranged from 20 to 100
years, depending on the potential for plant growth and
fuel accumulation on the site. 60 However, University of
Wyoming ecologist William Baker did a thorough review
of the methods used for calculating such estimates and
concluded that fire rotations probably were much longer:
325-450 years in shrublands dominated by low sage-
brush; 100-240 years in shrublands dominated by Wyo-
ming big sagebrush; and 70-200 years or more at higher